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Full text of "Delay Task Force study : Chicago O'Hare International Airport"

Digitized by the Internet Archive 

in 2012 with funding from 

CARLI: Consortium of Academic and Research Libraries in Illinois 



http://www.archive.org/details/delaytaskforcest02ohar 



r 



U.S. DEPARTMENT OF COMMERCE 
National Technical Information Service 



AD-A030 172 



O'HARE DELAY TASK FORCE STUDY VOLUME 2 
TECHNICAL REPORT CHICAGO O'HARE 
INTERNATIONAL AIRPORT 



Federal Aviation Administration 
Des Planines, Illinois 



July 1976 



TRANSPORTATION LIBRARY 

MAY 2 6 1978 *>**■& 
NORTHWESTERN UNIVERSITY 



TRAN 



TRAN 

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9797. 7C4 

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v.2 _ 



FAA-AGL-76-1, 



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O'HARE DELAY TASK FORCE STUDY 

VOLUME 2 TECHNICAL REPORT 

CHICAGO O'HARE INTERNATIONAL AIRPORT 



- si '»**-- 




*'-«riso' 



July, 1976 



Document if available to the public through the 

National Technical Information Service, 

Springfield, Virginia 22151 



REPRODUCED BY 

NATIONAL TECHNICAL 
INFORMATION SERVICE 

U. S. DEPARTMENT OF COMMERCE 
SPRINGFIELD, VA. 22161 

Prepared by the joint effort of: 

FEDERAL AVIATION ADMINISTRATION ^ 
CITY OF CHICAGO-DEPARTMENT OF AVIATION 
THE AIRLINES SERVING O'HARE 



c. "\- A L \ 



U6KAM 



U5$o 



NOTICE 

This document is disseminated under the sponsorship 
of the Department of Transportation in the interest 
of information exchange. The United States Govern- 
ment assumes no liability for its contents or use. 




Technical fcapart Documentation Pag* 



AGL-76-1 



Title and Subtitle 



ZfflL/ 



2. Government Accession No, 



O'Hare Delay Task Force Study* Volume 2 # 



hr- <L&4- 



"TfapA 



ni. 






7. Author's) Federal Aviation Administration, Chicago 
Department of Aviation, Airlines Serving O'Hare 



8. Performing Organization Report No. 



3. Recipient'* Co'oioo No. 



Report Date _' t 

Julfl 1976 J - 

rrerlSrwitig^rgoni lotion Cpde 



9. Performing Organisation Nan 



10. Work Unit No. (TRAIS) 



11. Contract or Grant No. 



12, Sponsoring Agency Nam* and Address 

Federal Aviation Administration 
Great Lakes Region 
2300 E. Devon Avenue 
DesPlaines. IUiaoiB 600*8 

15. Supplementary Note] 



13. Type of Report and Period Covered 



'«■ Sponsoring Agency Code 




%^hmq^ y£ft*'D«* ?V-:W7Mf< t 



^■^■^"^^r^^^ 



16. Abstract 

~> This joint FAA/City of Chicago/airline study of air traffic delay at Chicago O'Hare 
International Airport is presented in three volumes. The first volume is an executive 
summary of the study findings and recommendations. The second volume is the 
technical report, covering the findings, conclusions and documentation of the data and 
methodology utilized in the study. The third volume consists of appendices which con- 
tain data and explanatory materials. 

This study of air traffic delay at Chicago O'Hare International Airport, its causes and 
potential solutions outlines a comprehensive program of delay reduction measures that 
have the potential to dramatically reduce the level and cost of delay. The study also 
quantifies benefits of elements of the upgraded third generation air traffic control 

system. 




II. Qleh-iev««en Statement 

Document is available to the public through 
the National Technical Information Service, 
Springfield, Virginia 22151. 



17. Key Wards 

delay, capacity, throughput, demand, 
quota hours, schedule peaking, optimized 
configuration selection 



19. Security Classif. (of this report) 

unclassified 



Jl. No. of Pages 



20. Security Classif. (*f this page) 

unclassified 



22. Price 



Form DOT F 1700.7 (8-72) 



Reproduction of compUtod page rmfKorlied 



PREFACE 

The joint FAA, City and Airline study of air traffic delay at Chicago O'Hare 
International Airport, its causes and potential solutions has identified no individ- 
ual panacea to the problem in the present or future. However, the study does 
outline a comprehensive program of delay reduction measures which if imple- 
mented, has the potential to dramatically reduce the current level and cost of de- 
lay. The program will also provide significant future delay reduction benefits 
regardless of the future air traffic control environment. The potential cost savings 
outlined are not intended to represent absolutes but rather to point out the most 
productive directions in which to focus future industry action. 

The study is unique both in the degree of quantitative evaluation applied 
and the cooperative atmosphere with which it was accomplished. In an industry 
beset by a myriad of problems such as sharply escalating operating costs, the 
study's focus on increasing the efficiency of an existing resource is noteworthy. 
That potential improvements in efficiency were identified in an operation as com- 
plex and as thoroughly studied in the past as O'Hare is encouraging. 



The study was conducted from 1 December 1974 through June 1976. During 
this time several of the delay reduction concepts identified have been tested and 
implemented by the study sponsors with results which appear to parallel those 
identified in the taskforce evaluations, lending additional credence to the valid- 
ity of the directions identified. 

The O'Hare Delay Taskforce Study Report is presented in three volumes: 



Volume 1 - Executive Summary - a summary of the key 
findings, conclusions and recommendations developed by 
the study group. 

Volume 2 - Technical Report - detailed technical evaluation 
which led to the study findings and conclusions. 

Volume 3 - Technical Appendicies - documentation of the 
data and methodology utilized in the analyses. 



Throughout the approximate 18 month period of this study, numerous in- 
dividuals made contributions to the group's endeavors. A list of the individuals 
who most frequently participated in the taskforce deliberations is presented on 
the following page. 



O'HARE DELAY TASKFORCE PARTICIPANTS 



FAA GREAT LAKES REGION 

Amundsen, Norman 
Johnson, Carl W.* 
Murray, James 
Oleson, Norman 



Chief of Planning Staff 
Planning Specialist 
Operations Specialist 
Planning/Procedures Officer 



CITY OF CHICAGO DEPARTMENT OF AVIATION 



Carr, John 
Donovan, Jim 
Henry, David 
Rothengass, Albert A.** 
Shaver, Paul D.** 
Stubitsch, Jon V. 



City Consultants : 



Booth, C.F. 
Thomas, Jeffrey N. 



Airport Manager, O'Hare 

Operations Supervisor, O'Hare 

Project Manager 

Assistant to the Commissioner 

Chief of Planning 

Project Manager 



Senior Consultant 
Vice President 



AGL-4 
AGL-4.3 
AGL 540.4 
O'Hare Tower 



Landrum & Brown 
Landrum & Brown 



AIRLINES 



Arras, William F. 

Hottman, Ralph C. 
Hubbard, Herbert B 

McLean, George D. 

Mountjoy, Kimball 
Vittas, George P.** 
Wickens, Ronald D. 



Manager, Airfield Operations 

Planning 

Regional Director 

Director Operations Research 

& Development 

Director, Operational 

Engineering 

Project Leader 

Director Airport Planning 

Director Operational & Advance 

Engineering 



FAA/ATA WASHINGTON WORKING GROUP 



Dziuk, James C. 
LaRochele, Phillip J 
McGinn, James 

Poritzky, Sigbert 

FAA Consultants: 



United Airlines 

ATA Chicago 
United Airlines 

American Airlines 

United Airlines 
American Airlines 
Continental Airlines 



Program Manager ATF-4 

Program Manager AEM-100 

Vice President, Regional 

Operations 

Director, NAS System Engineering 



FAA 
FAA 
ATA 

ATA 



* 
** 



Hockaday, Steve 
Sinha, Agam N. 

Taskforce Chairman 
Group Chairmen 



Senior Consultant 
Member of Technical Staff 



PMM6C0. 
MITRE Corp. 



TABLE OF CONTENTS 



O'HARE DELAY TASKFORCE STUDY 
VOLUME 2 - TECHNICAL REPORT 



Page 

PREFACE i 

TABLE OF CONTENTS iii 

LIST OF EXHIBITS v 

CHAPTER 1 - INTRODUCTION 

1.1 Background 1- 1 

1.2 Objectives 1- 5 

1.3 Scope 1-6 

1.4 Methodology 1- 7 

CHAPTER 2 - SYSTEM DESCRIPTION 

2.1 Existing Airspace Structure 2- 1 

2.2 Existing Airfield Facilities 2- 9 

2.3 Existing Apron/Gate Facilities 2- 9 

CHAPTER 3 - CURRENT SYSTEM PERFORMANCE 

3.1 Current Airspace/Airfield System Capacity 3- 1 

3.2 Current Level of Airspace/Airfield System 

Delays 3-14 

3.3 Causes of Current Airspace/Airfield System 

Delays 3-26 

3.4 Delays Due To Short Duration Operating 

Anomalies 3-47 

3.5 Current Level of Apron/Gate System Delays 3-51 

CHAPTER 4 - CURRENT DELAY REDUCTION OPTIONS 

4.1 Air Traffic Control Procedural Options 4- 5 

4.2 Airport Use Policy Options 4-17 

4.3 Airport Development Options 4-31 



in 



TABLE OF CONTENTS 

O'HARE DELAY TASKFORCE STUDY 
VOLUME 2 - TECHNICAL REPORT 



Pa g e 
CHAPTER 5 - FUTURE DELAY REDUCTION OPTIONS 

5.1 Overview of the FAA Engineering and 

Development Program 5- 1 

5.2 Description of Future O'Hare Operating 

Scenarios 5- 4 

5.3 Future Airspace/Airfield System Capacity 5- 9 

5.4 Future Level of Airspace/Airfield System 

Delays 5-18 

5.5 Other Future Delay Reduction Options 5-23 

5.6 The Potential Impact of ASTC, RNAV, and MLS 5-26 

CHAPTER 6 - DEMAND/DELAY RELATIONSHIPS 

6.1 Existing Demand/Delay Relationships at 

O'Hare 6- 1 

6.2 Future Demand/Delay Relationships Under 

Existing ATC Separations 6- 7 

6.3 Demand/Delay Relationships for Assumed 

Pre- 1985 ATC Equipment 6- 9 

6.4 Demand/Delay Relationships for Assumed 

Post- 1985 ATC Equipment 6-11 

6.5 Future Delay Costs 6-12 

CHAPTER 7 - SUMMARY FINDINGS AND RECOMMENDATIONS 

7. 1 Current System Performance 7- 2 

7.2 Delay Reduction Options 7- 5 

7.3 Future ATC System Improvements 7-11 

7.4 Demand/Delay Relationships 7-14 

7.5 Recommended Action Plan 7-16 



IV 



LIST OF EXHIBITS 

O'HARE DELAY TASKFORCE STUDY 
VOLUME 2 - TECHNICAL REPORT 



Exhibit Description Page 

1-1 NASCOM Delay Reports 

1-2 Weather Conditions Modeled 

1-3 Runway Configurations Examined 

1-4 Basic Schedules Modeled 

1-5 Study Experiment Design Matrix 

1-6 Objective 1 Methodology 

1-7 Objective 2 Methodology 

1-8 Objective 3 Methodology 

1-9 Objective 4 Methodology 

2-1 Airport Vicinity Map 

2-2 NAS-Chicago ARTCC Boundaries 

2-3 Study Area Airspace 

2-4 Terminal Area Vector Routes 

2-5 Terminal Area Airports 

2-6 Airfield Plan 

2-7 Existing Airfield Characteristics 

2-8 Arrival and Departure Minimums 

2-9 O'Hare Terminal-Gate Complex 

3-1 Experiment Design Current Baseline 

3-1A Results of Current Baseline Experiments 

3-2 FAA Model Capacity rpj 

3-3 Arrival Percentage Impact on Capacity tp\ 

3-4 Baseline Capacity/Throughput 

3-5 Throughput/Capacity (ST) Relationships 

3-6 Historic Runway Use Pattern 

3-7 Average Daily & Peak Hour Delay by Configuration 

3-8 Delay vs. Capacity (ST) Daily & Peak Hour 

3-9 Delay vs. Throughput f Capacity tcj\ 

3-10 Current Annual Baseline Delay 

3-11 Current Delay Cost £ Fuel Consumption 

3-12 Capacity Impact Intersection Location 

3-13 Daily Connecting Passengers 

3-14 Scheduled Operations by Hour Friday, Nov. 

3-15 Baseline Schedule Demand Characteristics 

3-16 Scheduled vs. Actual Operations-Sept. 1975 



. 


1- 2 




1-13 




1-15 




1-16 




1-18 


' 


1-20 




1-22 




1-24 




1-26 




2- 2 




2- 4 




2- 5 




2- 7 




2- 8 




2-10 




2-11 




2-12 




2-13 




3- 2 




3-3 


• 


3- 5 




3- 6 




3- 8 




3-10 


! • 


.3-12 


ration 


3-16 




3-18 




3-20 




3-23 




3-25 




3-32 




3-39 


7, 1975 


3-41 




3-42 


■- 


3-44 



LIST OF EXHIBITS 

O'HARE DELAY TASKFORCE STUDY 
VOLUME 2 - TECHNICAL REPORT 

Exhibit Description Page 

3-17 Anomalous Operating Delays 3-19 

3-18 Anomalous Operating Backlog 3-50 

3-19 Current Domestic Apron Frontage Requirements 3-53 

3-20 GATESIM Data-Current System Performance 3-55 

4-1 Initial Listing Delay Reduction Options 4- 2 

4-2 Experiment Design Current Delay Reduction 4- 3 

4-2A Results of Current Delay Reduction Experiments 4- 4 

4-3 Arrival Runway Capacity vs. Separation 4- 6 

4-4 Wind/Weather Coverage by Configuration 4- 9 

4-5 Daily Benefit of Improved Configuration Selection 4-11 

4-6 Configuration Rank Order by Average Delay 4-13 

4-7 Delay Optimized Runway Use Pattern 4-14 

4-8 Delay Impact of Runway Load Balancing 4-18 

4-9 Delay Impact of Intrahour Quota 4-22 

4-10 Schedule vs. Actual Arrival Pattern 4-23 

4-11 Distribution of Variations to Scheduled Arrivals 4-24 

4-12 Impact of Scheduled Carrier Volume Variations 4-28 

4-13 Proposed 4L/22R Angled Exit 4-33 

4-14 Terminal Area Taxiway System 4-36 

5-1 Future ATC Equipment Groups 5- 5 

5-2 Future ATC Separation Standards 5- 7 

5-3 Future ATC Operational Parameters 5- 8 

5-4 Experiment Design Future Delay Reduction 5-10 

5-4A Results of Future Delay Reduction Experiments 5-11 

5-5 Future O'Hare Hourly Capacity (pj 5-12 

5-6 Pre-1985 Delay 5-20 

5-7 Post-1985 Delay 5-21 

5-8 Capacity q^j 6 Delay Costs Pre & Post-1985 5-27 

5-9 Local Controller Performance 5-29 

5-10 Ground Controller Performance 5-30 

6-1 Experiment Design Demand/Delay Relationships 6- 2 

6-1A Results of Future Demand/Delay Experiments 6- 3 

6-2 Delay vs. Demand Existing System 6- 5 

6-3 Delay vs. Demand Current ATC Separations 6- 8 

6-4 Delay vs. Demand Pre-1985 ATC 6-10 

6-5 Delay vs. Demand Post- 1985 ATC 6-13 

6-6 Annual Delay Costs Optimized Runway Use 6-14 

7-1 Recommended Action Plan 7-22 



VI 



1 . INTRODUCTION 



This study of Chicago's O'Hare International Airport represents an in- 
depth evaluation of the complex interactions between aircraft demand, facility 
and equipment configurations, and air traffic control and airport management 
procedures which result in the airport's ability to process aircraft effectively. 



1.1 BACKGROUND 



Since the introduction in the early 1970's of the heavier wide-bodied air- 
craft with their attendant wake vortex problems, airfield capacity has been 
steadily reduced at the nation's major airports. The effect of this capacity re- 
duction has been compounded by the rapid escalation of aviation fuel prices re- 
sulting in significant increases in the cost of aircraft operation. In addition, en- 
vironmentalist pressures following enactment of the National Environmental 
Policy Act of 1969 have virtually foreclosed the development of new metropolitan 
airports to augment system capacity and made the incremental expansion of ex- 
isting facilities difficult at best. 

It has become increasingly clear that continued provision of satisfactory 
air transportation service will require the industry to concentrate its effort on 
maximizing the efficiency of the existing airport system, a fact brought out in 
the 1973 President's Aviation Advisory Commission report on the national avi- 
ation system. 

Faced with rapidly escalating aviation fuel prices and with increasing 
numbers of wide-bodied aircraft with direct operating costs upwards of 25 
dollars per minute, the aviation industry is faced with the need for quantitative 
system performance data on which to base tough management decisions on sched- 
uling strategies, facility and equipment expenditures, and research and devel- 
opment priorities. To provide such system performance data, this study was 
undertaken as a joint effort of the Federal Aviation Administration (FAA), the 
City of Chicago Department of Aviation and the airlines serving O'Hare under 
the general guidance of the Washington FAA/Air Transport Association (ATA) 
working group. 



1.1.1 The Upward Incidence of Air Traffic Delay Reports Provides 

Evidence that O'Hare Efficiency has been Affected by Recent 
Events . 



O'Hare, which annually processes approximately 9 percent of 
the nation's air passengers, is experiencing significant delays. 
National Airspace System Communications (NASCOM) records which 
tabulate the number of reports of delay in excess of 30 minutes are 
one measure of the effectiveness of system performance. Examina- 
tion of the NASCOM delay report data presented in Exhibit 1-1 yields 
the following information. 




OHare Delay Taskforce Study 
Chicago OHare International Airport 



ITITLE: 



NASCOM DELAY REPORTS 



SOURCE •" .", . ... 

Federal Aviation 
Administration 



1-2 



O'Hare delay reports show an upward trend as a per- 
centage of total reports since the 1970 introduction of 
heavy jet separation standards. In 1974, O'Hare delay 
reports approached the level experienced in 1969. How- 
ever, deiay reports in 1975 are 53 percent less than 
those reported in 1974. 

O'Hare has experienced a greater percentage increase 
in delays than the other major airports. This is clearly 
evident in the upward trend in O'Hare reports as a per- 
centage of the national totals, increasing from 22.5 per- 
cent in 1969 to 48.8 percent of such reports in 1974. 
In 1975, O'Hare delay reports decreased to 34.4 percent 
of the national totals; this level is considerably higher 
than that in the 1969-1970 period. 

The volume of total aircraft operations correlates closely 
with the level of delay reports; the number of reports 
being highest in those years when the total operational 
volume is the greatest. 

Scheduled domestic carrier traffic volumes have not 
varied significantly in the 7 year period from 1969 
through 1975. However, the O'Hare air carrier air- 
craft fleet currently includes in excess of 15 percent 
heavy jet aircraft, none of which were classified as 
heavy jets in the 1969 time period. 



As noted in the 1974 FAA study on airport capacity 1/ "... air- 
side capacity has fallen steadily at these airports" (8 major airports 
including O'Hare), "primarily because of the wake vortex problems 
associated with the new and heavier aircraft. . ." This study went 
on to state that "Reported cases of these delays indicate that 89 per- 
cent are attributable to weather related problems . . . the majority 
of severe delays are weather related and are largely unavoidable." 
There is reason in the O'Hare delay statistics pattern to question if, 
in fact, such delays are "largely unavoidable" or rather result from 
a series of factors (many controllable such as the number of aircraft 
in the system) which, when triggered by weather or other problems, 
compound into a severe system problem. 



1/ FAA Report on Airport Capacity; No. FAA-EM-74-5, Volume 1, 
FAA/DOT - January, 1974. 



1-3 



While the 1974 FAA capacity study furnished considerable in- 
sight to the capacity problems at O'Hare, many in the aviation in- 
dustry felt that the depth of the analysis was restricted by its multi- 
ple airport nature and general national system emphasis. In addi- 
tion, techniques available at the time of the 1974 study were inade- 
quate to measure the complex interactions between facilities, equip- 
ment, procedures, manpower, and aircraft that created delays. 
Both the FAA and the City of Chicago, recognizing the need for an 
increased level of quantification in airport development and oper- 
ation planning, were undertaking separate efforts to develop new 
capacity /delay methodologies. With availability of these new tech- 
niques, an updating and expansion of the previous work with more 
specific local input on the feasibility of implementing the improve- 
ments appeared in order. 



1.1.2 A Local Taskforce was Chosen as the Most Appropriate Means 

to Focus Industry Effort on O'Hare Problems . 



Establishment of a local Taskforce to study problems at O'Hare 
was an outgrowth of Washington FAA and ATA concern with airport 
capacity at the nation's major airports. In late 1974, an ad hoc FAA 
working group was established with the primary purpose of devel- 
oping mid and long term action plans to reduce airport delays. How- 
ever, in early coordination meetings with ATA, it was decided to 
concentrate initially on O'Hare problems and to merge the FAA effort 
with independent airline and FAA Great Lakes Region studies of the 
problem since both were getting underway. The City of Chicago De- 
partment of Aviation which had been studying O'Hare airfield improve- 
ments also became an integral part of the taskforce team. 

The Taskforce was envisioned as a method of developing joint 
support by the airlines, the City and the FAA for actions that would 
effectively reduce current delay and as a means to identify mid and 
long term development options for implementation or further inten- 
sive study. It was contemplated that recommendations developed 
jointly would be used as a basis of support for individual manage- 
ment decisions by each participant group, the net result of which 
would be a coordinated series of further actions whose combined 
effect would reduce delay significantly. 

The Taskforce was chaired by a representative of the Planning 
Staff, Great Lakes Region, FAA; the City contingency was headed by 
the Chief of Planning, Department of Aviation, and the airline/ATA 
group was headed by the Director of Airport Planning, American 
Airlines. Each participating group brought to the team its unique 



1-4 



perspective on the problem and technical expertise. FAA Washington 
provided the full support of its technical organization and consultant 
support as required from The Mitre Corporation (authors of the 1974 
capacity study and experts on the ATC environment) and Peat, Mar- 
wick, Mitchell 6 Co. (co-authors of the new FAA capacity model) . 
The Department of Aviation provided the use of the "AIRSIM" and 
"CATESIM" models and the continuous technical and editorial support 
of Landrum & Brown (developers of AIRSIM and CATESIM) in the 
full spectrum of taskforce activities. 



1.2 OBJECTIVES 



Considering the background of escalating delays with their cost implica- 
tions, the taskforce agreed upon five objectives to guide the analysis of present 
and future O'Hare conditions. These objectives were: 



1 . To determine current capacity and delay levels and to identify 
causes of aircraft delay associated with operations in the airspace/ 
airfield and apron/gate systems. See findings in Chapter 3. 

2. To determine the potential delay reduction benefits of alternate 
ATC procedural, airport use policy, and facility development 
options in the current and future periods. See current findings 
in Chapter 4 and future findings in Chapter 5. 

3. To determine the potential capacity increase and delay reduc- 
tion benefits of proposed future air traffic control (ATC) system 
improvements. See findings in Chapter 5. 

4. To determine relationships between air traffic demand and delay 
in the current and future time periods as an aid in establishing 
acceptable air traffic movement levels. See findings in Chapter 6. 

5. To identify areas of potential capacity constraint in the O'Hare 
terminal, groundside and access systems. 



The scope of the study and the methodology utilized to achieve these ob- 
jectives are described in the balance of this chapter. As noted above, subse- 
quent report chapters describe the study findings. Study conclusions and 
recommendations are presented in Chapter 7. 



1-5 



1 . 3 SCOPE 



Intensive effort was focused on the system elements where the aircraft is 
the predominant factor, principally the airspace/airfield system and secondly 
the apron/gate system. This focus does not imply that the O'Hare problems are 
primarily on the airside of the system or that these problems are more severe, 
but rather recognizes that with the limited time and resources available, the 
group simply could not accomplish an intensive evaluation of all key system 
elements. In fact, the list of potential O'Hare landside improvements is large, 
encompassing such diverse items as new terminal building construction, ground 
transit, curb front parking, access roadway additions, cargo, fuel system and 
other ancillary support facilities expansion, etc. , some of which may be critical 
factors constraining O'Hare's future capacity. The taskforce did not accomp- 
lish the identification of potential landside constraints envisioned in study Ob- 
jective 5. 

Specific attention should be brought to the fact that the taskforce did not 
evaluate major future capacity increasing items such as proposed dual lane run- 
ways which could reduce the impact of abnormal operating conditions caused by 
disruptions such as runway maintenance and construction programs. The scope 
of the study was thus constrained for the following two key reasons: 



First, it was recognized by the group that implementation of a 
major airfield facility improvement today requires extensive en- 
vironmental impact assessment and public coordination well be- 
yond the intent of the taskforce. In view of this situation, it 
was generally agreed that conclusions drawn only upon the oper- 
ational considerations being evaluated by the taskforce ran too 
high a risk of prejudicing the ability to ever accomplish what 
might prove to be desirable long-term airport development op- 
tions. 

Second, a currently on-going master plan study of the City's 
three airports, being funded under the Airport and Airways 
Development Act of 1970, provides a convenient vehicle to accom- 
plish the full environmental and economic evaluation required 
for major development projects. The master plan will include 
an exhaustive evaluation of items such as the role of each air- 
port in the Chicago system, relocation of the international and 
general aviation terminals, new runway or runway extension 
construction, parking, roadway and other access improvements, 
etc., resulting in a balanced plan for future facility improve- 
ment. The analyses and information developed by the taskforce 
provide basic input to the master plan and an excellent basis 
for initiating further study. 



1-6 



Consistent with the group's primary objectives, the effort focused on means 
for increasing ' iciiity operating efficiency and reducing delay through proced- 
ural adjustments, airport-use policy changes, and/or airport development actions. 

It should be recognized that the benefit analysis employed is in part a rel- 
ative one, that is, the conclusions were reached by comparing the relative order 
of magnitude of potential cost reduction offered by the options analyzed. In the 
course of the taskforce sessions, many potentially effective delay reduction ac- 
tions were identified which will require further intensive efforts and actions on 
a joint or individual basis by group participants. 

The conclusions and recommendations of the taskforce as presented in 
Chapter 7 of the report identify four types of actions as follows: 



Implementable Items - Changes or improvements whose bene- 
fits have been clearly identified and do not necessitate a major 
policy change by any of the study participants. 

Major Policy Items - Changes in procedural or regulatory en- 
vironment requiring major policy changes by one or more study 
participants. 

Master Plan Study Items - Physical improvements whose delay 
reduction merits must be assessed giving consideration to the 
full environmental and economic consequences. 

Air Traffic Control System Items - Improvements whose char- 
acter requires that they be system-wide in application, neces- 
sitating further evaluation and/or research and development 
by the Federal Aviation Administration. 



The methodology used to quantify the relative merits of the delay reduc- 
tion options under study is described in the following section of this chapter. 



1.4 METHODOLOGY 



The purpose of this section is to describe generally the methodology em- 
ployed by the O'Hare Delay Taskforce in achieving each of its study objectives. 
The intent at this point in the report is to provide the reader with an overview 
of the many concepts and methods used with specific details to be supplied 
throughout the report in support of key findings and conclusions. 



1-7 



1.4.1 Both Anaiytical and Simulation Models were Selected and 

Validated as Techniques with Which to Develop System Per- 
formance Parameters Under Alternate Operational Scenarios . 



One of the first efforts of the study was the selection of the 
quantitative techniques to be employed in support of all quantita- 
tive analyses. From these efforts, the Federal Aviation Adminis- 
tration's analytical capacity model and the City of Chicago/Land rum 
& Brown airspace/airfield and apron/gate simulation models were 
selected for use. These three models are briefly described in the 
following paragraphs. The appendices should be consulted for a 
detailed description of each model . 



1.4.1.1 FAA Capacity Model 



The FAA capacity model used in the study was devel- 
oped by Douglas Aircraft Company in association with Peat, 
Marwick, Mitchell and Company, McDonnell Douglas Auto- 
mation, and American Airlines under contract DOT FAA 72 
WA-2897. The model is, in essence, a series of equations 
which calculate the average time between successive op- 
erations for a specific runway configuration under specific 
conditions, the inverse of which is theoretical operations 
per time, or capacity. The model is described in Appen- 
dix D. 



1.4.1.2 Airspace/ Airfield Delay Simulation Model (AIRSIM) 



The City of Chicago AIRSIM model was developed and 
is maintained for the City by Landrum 6 Brown airport con- 
sultants. AIRSIM is a fast-time, stochastic simulation model 
which simulates arriving aircraft from entry into terminal 
airspace until reaching the outer taxiway at O'Hare. Depar- 
tures are simulated from entry into the outer circular taxi- 
way until exit into the terminal airspace. All significant 
operations within the terminal area airspace/airfield sys- 
tem are included in the model. As part of the taskforce 
study, the model was successfully validated against Janu- 
ary and September 1975 operations data; this validation is 
described in Appendix B . 



1-8 



1.4.1.3 Apron/Gate Simulation Model (GATES IM) 



The City of Chicago GATES IM model, also developed 
and maintained by Landrum & Brown, is a fast-time, 
stochastic simulation model and was used, to a limited ex- 
tent, to identify current delays incurred by aircraft man- 
euvering in the apron/gate area. GATESSM is a companion 
model to AIRSIM and simulates aircraft movement and gate 
scheduling and rescheduling functions in the terminal apron 
area and taxiway system surrounding the terminal area. 
The GATESIM model output compared favorably to Septem- 
ber 1975 operations data as described in Appendix C. 



1.4.2 Capacity, Throughput, and Delay were Selected as Basic 

Measures of System Performance for Use in the Analyses , 



In a system as large and complex as Chicago's O'Hare Inter- 
national Airport and its surrounding airspace, there are a multitude 
of parameters which serve as leading indices of the performance of 
the entire system. For purposes of this study, capacity, through- 
put and delay were selected as those most indicative of good or bad 
system performance. For use in this study, it was necessary to 
give these terms very careful and precise definitions as discussed 
below. 

As applied to an airport, "Capacity" is an often misunderstood 
concept. The term originated as a simple, all-inclusive quantitative 
descriptor of an airport's capability to process aircraft operations. 
Capacity was intended to be a simple descriptor, reliable enough to 
support the making of key decisions on subjects such as airport facil- 
ities expansion or aircraft scheduling. Unfortunately, experience 
in the aviation industry has demonstrated that airport capacity is, 
in fact, a highly complex concept. It is often misunderstood and sub- 
sequently misused because of either a failure on the part of techni- 
cians to adequately present all qualifying definitions and assump- 
tions or a failure on the part of industry professionals to take the 
time and effort to acquire a thorough understanding of the language 
and symbolism involved. 

The O'Hare Delay Taskforce recognized these problems of defi- 
nition and interpretation at the beginning of the study and, accord- 
ingly, adopted the following definitions of capacity related terms. 



1-9 



Airfield Capacity is the maximum number of aircraft 
operations (takeoffs and landings) which may be pro- 
cessed, irrespective of delay, in a given time at an 
airport under specific conditions of: 

airspace constraints 

ceiling and visibility conditions 

runway layout and use 

aircraft mix 

percent arrivals 

exit taxiway locations 

system variability 

As a number, airfield capacity is always a calculated 
value and may be expressed on an hourly or an annual 
basis. On the surface, airfield capacity seems a simple 
concept. However, confusion begins when one seeks 
to attach a number to the word "capacity" as a descrip- 
tor of the airport under some specific set of conditions. 
Because several different methods are employed in 
this study to calculate airfield capacity, and because 
the various methods rest on different simplifying as- 
sumptions to make the capacity calculation tractable, 
and because the various methods yield different an- 
swers, each valuable for different limited purposes, 
it was necessary to devise some additional definitions 
and symbols for use throughout the rest of this report. 

Capacity (F) " This is the maximum number of aircraft 
operations which may be processed in an hour at 
O'Hare under specific conditions of: 

airspace constraints 

ceiling and visibility conditions 

runway use 

aircraft mix 

percent arrivals 

exit taxiway locations 

and under the assumption of constant, continuous de- 
mand. In this study. Capacity ,p* was calculated only 
by using the FAA capacity model described in Appen- 
dix D. 



1-10 



Throughput is the number of aircraft operations 
that may be processed at O'Hare given actual de- 
mand under the same situation descriptor inputs 
listed above. At practical operating levels, through- 
put is always less than capacity due to variations in 
volume and distribution of actual demand. In this 
study, throughput is a value calculated using the 
AIRSIM model described in Appendix B. Throughout 
this report, daily throughput and hourly throughput 
calculations are both discussed. Daily throughput re- 
fers to the number of operations processed from 8AM 
to 8PM . 

Capacity (C .-r\ ' s tne throughput value calculated using 
the AIRSIM model under the special case assumption 
of demand saturation . The ST subscript alludes to sat- 
uration throughput. 

Capacity rw^) expresses the year round, weather and 
configuration use weighted, average hourly aircraft 
processing capability of O'Hare. The WA subscript re- 
fers to weighted annual capacity calculated with the 
AIRSIM model. 



In addition to the above listed capacity related terms, the following 
delay related terms were adopted. 



Delay is the difference between the actual time it takes 
an aircraft to perform an operation over a specific por- 
tion of the system and the normal time it would take to 
perform the same operation with no interference from 
other aircraft. Three delay measures calculated by the 
AIRSIM model are utilized throughout the report as fol- 
lows: 

Average Delay - Average delay per aircraft 
operation - total system delay minutes divided 
by total aircraft operations processed. 

Departure Delay - Average delay per aircraft 
departure - total departure delay minutes di- 
vided by total departures processed. 

Arrival Delay - Average delay per aircraft 
arrival - total arrival delay minutes divided 
by total arrivals processed. 



1-11 



In addition to the foregoing airspace/airfield delay measures, 
the CATESIM model was used to determine delays associated with 
aircraft operations in the apron/gate system. 



Although the above defined parameters were employed in every 
analysis conducted, these basic measures of system performance 
were supplemented by other performance measures (queue statistics, 
etc.) as required. Throughout this report when the word "capacity" 
is associated with a number, one of the subscripted forms of the word 
defined above is used to identify the method used to calculate the 
number. When the concept of capacity is under general discussion, 
and is not associated with a number, the word is used uncapitalized 
and unsubscri p te d . 



1.4.3 A Listing of Potential Delay Reducing Items was Synthesized 

as a Basis for Design of Analytical and Simulation Model 
Experiments . 



The Initial effort was the listing by each group participant of 
facility development items, instrumentation/equipment requirements,, 
operational and procedural changes which they believed would be 
beneficial in reducing delay. After discussing the various delay 
causes and considering study time and resources limitations, the 
group synthesized a composite listing of possible delay reduction 
options as a guide for further evaluation; this list is presented in 
Chapter 4, Exhibit 4-1 . To the extent that the delay reduction items 
on the list contributed to the overall objectives, they were investi- 
gated using all qualitative and quantitative methods of analysis at 
the taskforce's disposal. 

While the FAA capacity model and City of Chicago simulation 
models were the primary quantitative analysis tools employed to 
meet the study objectives, additional quantitative analyses were 
used both to facilitate and to supplement the model experiment re- 
sults. These analyses are discussed in detail throughout the text 
in this and subsequent chapters. These basic descriptors of the 
study experiment design are discussed in the paragraphs which 
follow. 

Four "weather conditions" were identified to be modeled. These 
conditions represent the various ceiling/visibility combinations shown 
in Exhibit 1-2 along with the historic occurrence of each combination. 
The FAA model experiments were conducted for weather conditions 1 
and 4 while the City of Chicago model experiments were conducted for 



1-12 



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NOTE: •Period of record is January 1, 1965 to December 31, 1974 
(time period: 8am -8pm) 

• Numbers in parentheses indicate historic annual 
percentage of the minimum and maximum ceiling/visibility 
conditions indicated by the shaded areas. 



O'Hare Delay Taskforce Study , i 
Chicago O'Hare International Airport 



I TITLE: 



WEATHER CONDITIONS 
MODEL ED 

1-13 



SOURCE (;.'■: ;.■:. >.,. 

Land rum & Brown 

-? ■' AIRPORT CONSULTANT S'. 



EXHIBIT 

1-2 



weather conditions 1, 2, and 3 thereby providing information regard- 
ing operations at O'Hare in weather ranging from ceiling and visibil- 
ity unlimited (CAVU) down to ceiling and visibility of 200/*. Weather 
below 200/ i has occurred only 1 . 1 percent annually over the period 
of record (January, 1965 to December, 1974). With the exception of 
the AIRSlM validation exercise, described in Appendix B, weather 
conditions 1 and 2 were combined to represent VFR operating condi- 
tions in the taskforce evaluation . 

In all analyses employing the models, the combinations of run- 
ways modeled (configurations) were selected to represent those 
used extensively in the past as well as to represent those configu- 
rations which might perform well under present or future opera- 
tional conditions. Exhibit 1-3 graphically depicts the operational 
configurations examined and their numeric designation as used 
throughout the report. The weather condition/configuration com- 
binations modeled by the two techniques were not necessarily coin- 
cidental and were selected for different reasons. The FAA model 
experiments were designed to provide a first cut relative ranking 
of the VFR or IFR capacity for all configurations. City of Chicago 
AIRSlM experiments were designed to provide baseline capacity and 
delay data for those configuration/weather conditions most reflec- 
tive of the current airport use patterns and those configurations 
identified as offering potential for high capacity/low delay perform- 
ance. All experiments conducted for future operational scenarios 
employed VFR and IFR configurations with expected performance 
typical of the overall system operation in the future. 

For the purposes of the taskforce analysis, an aircraft "sched- 
ule" consists of a listing of the arrival and/or departure time, air- 
line, and aircraft type for all airport activity during the period 
from 8AM to 8PM. The "schedule" includes scheduled domestic and 
international air carrier, scheduled air taxi, and air cargo flights 
plus non-scheduled general aviation, air taxi, air carrier extra 
sections, charters, and test flights. It should be noted that the non- 
scheduled activity does not include military flights or the general 
aviation activity which is handled on runways other than those in 
the primary configurations. 

The hourly pattern of demand in the four basic aircraft "sched- 
ules" modeled is depicted in Exhibit 1-4. Each "schedule" is de- 
scribed in additional detail in Appendix A. The January and Sep- 
tember 1975 schedules were developed using the scheduled activity 
identified in the Official Airline Guide and non-scheduled activity 



1-14 





Note: 

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Chicago O'Hare International Airport 



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as identified in tower records and by field observation of O'Hare 
activity. Initial analyses were conducted assuming January 1975 
levels of operational demand and then existing ATC separation 
standards. However, during the fall of 1975 it was announced 
that those separation rules would be amended to include an addition- 
al mile separation for all aircraft of the newly created "small" cate- 
gory when following a large or heavy aircraft on final approach. The 
"small" category consists of all aircraft whose gross weight is 12,500 
pounds or less, including all models of the Learjet. In order not to 
invalidate any results it was decided to conduct all further experi- 
ments against September 1975 levels of operational demand under 
the new ATC separation standards. The latest separation standards 
(November 15, 1975) have been used for the current "baseline"; 
however, the January data is presented for reader information. Two 
basic future operational demand schedules depicted in Exhibit 1-4 
were utilized, one for the pre- 1985 period with 27 percent heavy jet 
aircraft and a second for the post-1985 period with 45 percent heavy 
jet aircraft. These "schedules" were based upon airline supplied 
volume and fleet mix data by 15 minute time increments and upon 
historic patterns of non-scheduled aircraft demand. These schedules 
assumed enforcement of the present 135 operations per hour estab- 
lished by the quota rule and extension of the quota hours. 

In addition to the January and September separation standards 
which are hereafter referred to as existing ATC, two future ATC 
environments were modeled. Future air traffic control system im- 
provements are planned to be implemented in time periods or stages 
(called groups) with different improvements installed during each 
period, each group enhancing the performance of the last. A total 
of four such equipment groups are described in detail in Appen- 
dix F. The intent was not to conduct a benefit analysis of each ATC 
improvement for O'Hare but to measure the benefits which will be 
derived from reduced in-trail separations and increased delivery 
precision of the Croup 2 and Group 4 equipment. These equipment 
groups were assumed achievable during pre- 1985 and post- 1985 
time periods, respectively. 

The experiment design for the capacity and delay experiments 
is presented in matrix form in Exhibit 1-5. In the experiment de- 
sign matrix, each row represents the runway configuration and 
weather combination. Each column represents a specific set of ATC 
separation standards governing operations, basic operational de- 
mand schedule, and schedule adjustment or modification. The en- 
circled numbers identify "AIRSIM" and "CATESIM" experiments and 
will be used in later chapters to identify the output. The numbers 
are not necessarily in the sequence in which the experiments were 
conducted. The dots represent unnumbered capacity model experi- 
ments. Specific details of each operations schedule and capacity 



1-17 





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1-5 



1-18 



model input parameters are presented in Appendix A along with de- 
tails of the ATC separation standards and the operating procedures 
for each configuration. 

The fundamental relationships between model inputs, analysis, 
and outputs are discussed in the sections which follow as they apply 
to each of the four study objectives accomplished. 



1.4.3.1 To Determine Current Capacity and Delay Levels 

And to Identify Current Causes of Aircraft Delay 
Associated with Operations in the Airspace/Airfield 
And Apron/Gate Systems . 



Objective 1 was accomplished using the relationships 
between study input, analyses and output depicted in Ex- 
hibit 1-6. In order to satisfy Objective 1, it was necessary 
to determine the hourly capacity ratings and throughput and 
delay characteristics for each key configuration currently 
operating at O'Hare during the high activity period. The 
period from 8AM to 8PM was selected since the bulk of air- 
port activity and delay occurs during these hours. With 
the above described model outputs, it was possible to de- 
termine the performance of one configuration relative to a- 
nother and in conjunction with those most familiar with the 
operation of the system to assess the factors causing cur- 
rent levels of delay, either on a configuration specific or 
total airspace/airfield system basis. In order to ensure 
consistency of study analyses, the AIRSIM capacities and 
throughput statistics were compared with FAA Engineering 
Performance Standard (EPS) estimates of system perform- 
ance. The relationships of delay to airfield capacity and 
the throughput/capacity ratio to delay were analyzed for 
the current operation. 

With knowledge of the delay performance of each key 
configuration and determination of the historic runway use 
pattern (ascertained by analysis of control tower records 
and discussions with O'Hare controllers), it was possible 
to define the weighted annual VFR and IFR capacity of 
O'Hare as it has been operated in the past and to identify 
the annual level cf system delay. The annual hours of de- 
lay were converted to direct aircraft operating costs by 
application of weighted fleet operating cost data. The in- 
dividual daily configuration and annual system delay sta- 
tistics provided a baseline against which capacity and de- 
lay improvements could be measured in meeting the group's 
other objectives. 



1-19 




O'Hare Delay Taskforce Study 



T OBJECTIVE 1 METHODOLOG 
IRENT SYSTEM PERFORMANCE 



IcxHierr 



t_andrum & Brown 

AIRPORT CONSULTANTS' 



1-6 



1-20 



The findings for Objective 1 are presented in Chap- 
ter 3 . 



1.4.3.2 To Determine the Potential Delay Reduction Benefit 

Of Alternative ATC Procedural, Airport Use Policy 
And Facility Development Options in the Current 
And Future Time Periods. 



Objective 2 was accomplished using the relationship 
between study input, analyses and output depicted in Ex- 
hibit 1-7. There exists a wide variety of options offering 
delay reduction potential capable of implementation today. 
These options can be broadly categorized as follows: 



Air Traffic Control Procedural Options - op- 
tions exercised by the Federal Aviation Ad- 
ministration for the purpose of promoting the 
safe, orderly, and expeditious flow of air 
traffic. 

Airport Use Policy Options - options exer- 
cised by those managing and using the air- 
port which determine the operational char- 
acteristics of both the demand on the airport 
and the facilities serving that demand. 

Facility Development Options - options whose 
implementation is characterized by the installa- 
tion of new equipment or construction of facil- 
ities. 



The baseline capacity and delay values developed in 
Objective 1 were compared with mode! experiments per- 
formed to measure the incremental benefit resulting from 
delay reducing alternatives. By measurement of the capac- 
ity increase or delay reduction over current baseline con- 
ditions as a result of each option, the potential benefit of 
each option was identified. Delays were extensively uti- 
lized because the potential direct aircraft operating cost 
savings derived from reduced delays are the primary eco- 
nomic justification for undertaking improvements, recogniz- 
ing that any direct aircraft operating cost saving is accom- 
panied by a corresponding reduction of like magnitude in 



1-21 





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865ECT8VE 2 METHODOLOGY 


SOURCE 

Landrum & Brown 

AIRPC^T CONSULTANTS .' 


CXHHHT: 


1 Chicago O'Hare International Airport 


DELAY REDUCTION OPTIONS | 


1-7 



1-22 



inconvenience and cost to the traveling public. Techniques 
other tha ■ simulation which were employed to assess other 
options are described in later chapters. 

The findings related to current delay reduction options 
are presented in Chapter 4 while those related to the future 
periods are presented in Chapter 5. 



1.4.3.3 To Determine the Potential Capacity Increase and 

Delay Reduction Benefits of Proposed Future ATC 
System Improvements . 



The third study objective was accomplished using the 
methodology depicted in Exhibit 1-8. Capacity statistics 
were computed to determine the performance of selected 
configurations in the ATC environment as it is forecast to 
be in the pre- 1985 and post- 1985 periods. The forecasts 
of future ATC system performance were developed by FAA 
research and development experts and are documented in 
Appendix F. The potential capacity increase and delay 
cost savings benefits were measured by comparing the re- 
sults of carefully constructed simulation experiments rep- 
resenting the future with and without proposed ATC im- 
provements. 

Those elements of proposed ATC equipment which did 
not directly affect capacity and delay and did not lend them- 
selves to quantification with the models were also analyzed. 
The expected benefits of future ATC system improvements 
are presented in Chapter 5. 



1.4.3.4 To Determine Relationships Between Air Traffic 

Demand and Delay in the Present and Future Time 
Periods as an Aid to Establishing Acceptable Air 
Traffic Movement Levels. 



Objectives 1 and 2 defined O 'Hare's current capacity 
and identified the benefits of delay improvement options. 
Objective 3 defined the system's future capacity and delay 
imminent under the two most probable future ATC and de- 
mand scenarios. In order to meet Objective 4, it was de- 
sired to extend these analyses to predict the amount of air- 



1-23 




O'Hare Delay Task force Study 
Chicago O'Hare International Airport 



TITLE 



Hike- 

OBJECTIVE 3 METHODOLOGY 
FUTURE ATC IMPROVEMENT S 

1-24 



Landrum & Brown 

AIRPORT CONSULTANTS 



craft delay to be expected under various demand levels 
both now and in the future. This expected delay under 
different demand levels was of primary importance be- 
cause of the guidelines it furnishes for setting future 
quotas and schedules to ensure that delays at O'Hare do 
not become extreme yet demand is not overly restricted. 
The relationship between demand and expected delay for a 
given set of operating conditions was expressed in the form 
of curves similar to the one illustrated below. Such rela- 
tionships between demand and delay were developed for the 
current, pre-1985 and post-1985 time periods. 



TYPICAL DELAY CURVE 



Average 
Delay 




Demand 



The City of Chicago "AIRSIM" model was used in the anal- 
ysis employing the procedure schematically depicted in Ex- 
hibit 1-9. Typical VFR and IFR runway use configurations 
were selected for analysis in both the pre-1985 and post- 
1985 ATC environment and modeled with operational sched- 
ules conforming to three possible future demand levels for 
each time period. In order to test the sensitivity of delay 
to percentage of heavy aircraft, upper and lower estimates 
of the percentage of heavy aircraft in future fleets were de- 
veloped. 

The current relationships between demand and delay 
and those estimated to occur in the pre-1985 and post-1985 
periods are presented in Chapter 6 under the most probable 
future ATC equipment environments and the "do nothing" 
situation. 



1-25 



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O'Hare DelayTaskforce Study 
Chicago O'Hare International Airport 



I TITLE: 



OBJECTIVE 4 METHODOLOGY 
(N D/ DELAY REL A1 

l-2fr 



Landrum 4 Brown; 

, ;». -A.IRPORT CONSUtTANTS' 



(EXHIBIT: w. 

1£J 



2. SYSTEM DESCRIPTION 



Chicago O'Hare International Airport (ORD) is located approximately 16 
miles northwest of the downtown Chicago Loop area. The airport lies in 2 counties, 
Cook and DuPage, on approximately 6,925 acres of land. O'Hare International's 
main access lies to the east of the airport boundary near the intersection of 1-194 
and 1-294. These interstate highways provide far easy access to the airport from 
nearby population centers. Exhibit 2-1, Airport Vicinity Map, is provided to 
show the relationship of O'Hare International Airport to the Chicago metropolitan 
area. 

All analyses encompassed a system composed of O'Hare's terminal area 
airspace, its airfield, and its apron/gate facilities. The components of the total 
system include the Chicago approach control airspace, stacks, approach areas, 
runways, exits, the inner/outer circular taxiway, the apron area, and the air- 
craft gate positions. The purpose of this section is to describe briefly the phys- 
ical properties of these system components: 



Existing Airspace Structure 
Existing Airfield Facilities 
Existing Apron/Cate Facilities 



These system elements are discussed in the following paragraphs, 



2.1 EXISTING AIRSPACE STRUCTURE 



The purpose of the following discussion is to provide a basic inventory, 
review and preliminary analysis of the enroute and terminal airspace system 
associated with Chicago O'Hare International Airport. The review performed 
was general in nature to provide a data base for more detailed study where nec- 
essary in later phases of the taskforce study. 



2.1.1 The Enroute Element of the System is the Responsibility of 

the Chicago Air Route Traffic Control Center . 



The Chicago Air Route Traffic Control Center (ARTCC) con- 
trols all IFR air traffic arriving and departing the Chicago metro- 
plex area. Traffic for O'Hare and other satellite airports is handled 
by the Chicago Center before control is transferred to Chicago Term- 




SCALE IN MILES 



QHare Delay Taskforce Study 
Chicago O'Hare International Airport 



ITITLE: 



AIRPORT VICINITY MAP 



2-2 



Deparfjrient 
of Aviation 



lEXMWIT: 

2-1 



inal Radar Approach Control (TRACON) . Overflights of Chicago 
Center airspace are generally kept to the south of O'Hare for east/ 
west traffic and to either the east or west for north/south oversights, 
the purpose being to reduce the number of targets on radar scopes 
in the ARTCC arrival and departure transition sectors. Exhibit 
2-2 displays the National Airspace System (NAS) Stage A bound- 
aries of the Chicago ARTCC and its low altitude sectors. Of pri- 
mary concern are the arrival transition sectors through which air- 
craft inbound to O'Hare are transitioned (in attitude) from the en- 
route portion (about 18,000 feet) to the terminal portion (7,000 
feet) of their flight. Associated with each of these transition sectors 
is an approach fix (clearance limit) at which control of inbound 
aircraft is generally transferred ("handed-off") from center to ap- 
proach control. The transition sectors with the associated primary 
approach fixes are the northeast (Base), southeast (Chicago Heights/ 
Plant), southwest (Vains), and northwest (Farmm) arrival sectors. 
Note that the areas between the arrival transition sectors are used 
as departure transition sectors. These sectors are also identified 
in Exhibit 2-2. Exhibit 2-3 depicts each arrival transition sector 
along with its primary approach fix and associated holding pattern 
airspace. Also shown in the exhibit is the boundary between that 
airspace belonging to approach control and that airspace belonging 
to Chicago ARTCC. It should be noted that holding pattern air- 
space in addition to that shown is available to the Chicago ARTCC 
and approach control. Only the primary fixes and holding pattern 
airspace are depicted. 



2.1.2 The Terminal Area Element of the System is the Responsibility 

of Chicago Approach Control (TRACON) . 



The Chicago terminal area airspace system includes all facilities, 
equipment, and personnel in the near-airport area required to trans- 
ition an aircraft safely from enroute to terminal area flight and subse- 
quent airport landing. In this report the terminal or study area air- 
space is defined as the approach control airspace which is shown in 
Exhibit 2-3. Within this airspace, Chicago ARTCC has delegated to 
Chicago approach control authority and responsibility for control 
of IFR and special VFR aircraft!/ at and below 10,000 feet. Also de- 
picted in Exhibit 2-3 is the Chicago terminal airspace network of 
Victor Airways, VORTACs, and non-directional beacons. 



1/ Special VFR aircraft are aircraft flying under visual flight rules in 
weather conditions less than basic VFR. 



2-3 



MKG - Low Altitude Sector Codes 



ZMP 




ZOB 



ZID 



NAS-STACE A ARTCC BOUNDARIES 



O'Hare Delay Taskforce Study 
Chicago O'Hare Internationa! Airport 



nrni: NAS- CHICAGO 

ARTCC BOUNDARIES 



Land r u tri^M. B r own i! 

i. ; AiBPO«t l 'G'6MSULT*NT$S, 



2-4 



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APPROACH CONTROL AIRSPACE 

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AIRWAYS AND ^AVAIDS 




Chicaao OMare interna' lonaif-AirDc 



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STUDY ARE^ 
2-5 



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23 



Current O'Hare arrival and departure radar vector routes with- 
in the terminal airspace are shown in Exhibit 2-4 for four primary 
directions of operation . After handoff by the ARTCC transition sec- 
tor controller, the arriving flights for O'Hare are vectored along 
the paths indicated by the solid line and merged into a single stream 
before the turn to the final approach. For the parallel runway oper- 
ations shown, the turns onto the final approach are separated by 
1,000' in altitude until established on the respective ILS localizer/ 
final approach course. 

O'Hare arrivals have historically been handled by two approach 
controllers who split all Chicago arrival traffic based on the primary 
direction of runway operation. Each of the approach controllers then 
vectored traffic to a separate runway and was responsible for merg- 
ing the aircraft from his approach fixes with the spacing requested 
by the tower local controllers. At times, when traffic was heavily 
imbalanced in favor of one runway, traffic adjustments were made to 
equalize controller traffic load. In this way, the spacing was ad- 
justed to accommodate departures, as required. Departures were 
handled by giving the flights a vector heading shortly after take- 
off. These headings, in general, were designed to allow the de- 
parting flight to proceed to the point of handoff to the Center enroute 
controller. The O'Hare departure routes are indicated by the dashed 
lines in Exhibit 2-4. 

However, a new concept which serves to distribute workload 
more evenly is currently being implemented at O'Hare. Under this 
concept, two additional controllers may be added during heavy traf- 
fic demands. These controllers initially accept arriving traffic from 
the ARTCC and establish the arriving sequence. After the arriving 
sequence has been established, the aircraft are handed off to the 
final controller who completes the vector to the final approach. De- 
parture procedures remain unchanged. ' 

Because of the high levels of traffic to and from Chicago, a Group 
I Terminal Control Area (TCA) has been established about Chicago 
O'Hare International Airport. This controlled airspace is shown in 
Exhibit 2-5. Also depicted in the exhibit are the location of the 33 
general aviation, commercial, and military airports within the Chicago 
terminal area airspace. Of the 33 airports, presently 13 have instru- 
ment approach capability. The terminal area is dominated by the op- 
erations at the O'Hare terminal. All ATC procedures are designed 
to move flights into and out of O'Hare with maximum efficiency. 
Terminal routings for the other airports within the Chicago metropol- 
itan area, including Midway, reflect this philosophy. 



2-6 



NORTHWEST 




Arrival Route 
Departure Route 



EAST 




Arrival Route 
Departure Route 




Arrival Route 
Departure Route 



WEST 




Arrival Route 
Departure Route 



O Hare Deiav Tasktorc# : Sludy 
Chicago^) Hare internal iojna£ Alport 



I TITLE: 



TERMINAL AREA 
VECTOR ROUTES 



Landrum & Brown 

- %l;Of>OP'. ; - ONSUlf A : N.T,S 



24 



2-7 



TEKMNMAL 

CCMTROL 
AREA 



■■*■ 




A PPRO ACH 
CONI HTO L. 

AIRSPACE 

10,000 FT. 



ft 



ILLINOIS 
McHenery County 

1 Killoy 

2 Hebron 

3 Gait 

4 Northern Pump 

5 Woodstock 

6 Crystal Lake 

7 Kuranz 

Lake County 

8 Antioch 

9 Cade 

10 Waukegan Memorial 

11 Campbell 

12 Haley AAF 

13 Chicagoland 



Kane County 

14 Landings 

1 5 Koppie 

16 Elgin 

Cook County 

17 Pal-Waukee 

18 NAS Clenview 

19 Mill Rose Farm 

20 Chicago O'Hare International 

21 Chicago Meigs . 

22 Chicago Midway 

23 Howell 

24 Chicago Hammond 



Pu Page County 

25 Chicago Schaumburg 

26 Wayne 

27 Du Page County 

28 Brookridge 

Will County 

29 Naper 

30 Wheatland 

31 Clow 

32 Lewis Lock port 

INDIANA 



Lake County 

33 Gary Municipal 



Hare Delay Taskforce Study 
Chicago O'Hare International Airport 



rrrai: 
TERMINAL AREA AIRPORTS 



Landrum &, Brown' 



2-8 



2.2 EXISTING AIRFIELD FACILITIES 



The airfield area includes the system of runways and taxiways as shown 
in Exhibit 2-6. The airfield consists of three sets of open parallel runways and 
one single runway. Parallel runways are in the southeast-northwest (14-32) 
direction, the east-west (9-27) direction and the northeast-southwest (4-22) 
direction. The single runway is in a north-south (18-36) direction. All runways 
except 18-36 and 4L-22R have parallel taxiways. Runway 18-36 is used primar- 
ily by general aviation propeller aircraft. Takeoffs in the 36 direction and land- 
ings in the 18 direction are the only operations conducted on this runway to pre- 
vent overflights of the terminal area. 

At present, all runways at O'Hare except 18-36 have some degree of instru- 
mentation to premit operations below VFR minimums. Two runways, 14L and 14R, 
are approved for Category II operations. A summary of pertinent information on 
existing runway characteristics, instrumentation and lighting, is shown in Ex- 
hibit 2-7. The arrival and departure minimums for each runway at O'Hare are 
presented in Exhibit 2-8. 



2.3 EXISTING APRON/GATE FACILITIES 



The apron/gate complex includes the concourses, aircraft parking posi- 
tions (i.e., gates), air carrier aircraft parking apron and dual circular inner/ 
outer taxiway. Exhibit 2-9 shows the general location of the various terminal 
complex facilities. These components are described in the following paragraphs 



2.3.1 The O'Hare Terminal Complex Consists of Three Unit Terminals 



The O'Hare terminal is of the unit with concourse type and con- 
sists of three structures. Terminal 1 is essentially the International 
Terminal where all customs and immigration (Federal Immigration 
Service, FIS) facilities are located. Non-scheduled supplemental 
carrier flight activity is also handled in Terminal 1 . Domestic air 
carrier flights are handled in Terminals 2 and 3. Concourse A facil- 
ities are used primarily for air taxi and commuter airline flights. 
General aviation aircraft operate from ramps both north and south of 
the fixed base operator building with services provided by Butler 
Aviation. 



2-9 



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O'Hare Oelav TasKforce Stutfy ^ 
Chicago O'Hare international Airoort : 



AIRFIELD PLAN 



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AIRPORT ONSUUANTS, 



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Tmfi EXiSTt K3 AIRFIELD 


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EXMIBIT: | 


Chicago Hare International' Airport : 


CHARACTERISTICS 


^ Ad nil n i st ra fi or*- 


2-7 



2-11 



RUNWAY 


MINI 


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TO 


REMARKS 


ARRIVAL 


DEPARTURE 


4L 


403-3/4 


1/4 VIS 






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Not considered feasible because 
of runway length. 


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250 - 3/4 


1/4 Vis. 


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200-1/2 


MALSR planned 1976. Land 
acquisition required for MALSR. 
Approach clearing being 
accomplished. 


9L 


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1/4 Vis. 


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250 - 1/2 


MALSR 1976. 


9R 


200-1/2 


1/4 Vis. 


RVRT, 
RVRR 


700 
RVRT* 


MALSR and RVR In 1976. 

A Center line light bases in place. 

Fixtures and wiring needed. 


14 L 


1200 RVR 


700 
RVRT 






Existing CAT II. 


14 R 


1200 RVR 


700 
RVRT 






Existing CAT II. 
Planned CAT IIIA. 


22 L 


250-3/4 


1/4 Vis. 


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200-1/2 


MALSR programmed for 1976 
Land acquisition required. 


22 R 


200-1/2 


1/4 Vis. 








27L 


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RVRR 


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RVRT* 


RVR in 1976. 

a Center line light bases in place. 

Fixtures and wiring needed. 


27 R 


2400 RVR 


1600 
RVRT 








32 L 


1800 RVR 


700 
RVRT 






Touchdown Zone lights installed. 


32 R 


2400 RVR 


700 
RVRT 








18 


VFR 


Not Auth. 








36 


Not Auth. 


Standard 









A Completion of center line light system needed to 
lower departure minimums to 700 RVRT. 

• Future improvement considerations limited to Category 1 
arrival minimums and to improve departure minimums. 



O'Hare Delay Taskforce Study 
Chicago QHare International-Airport 



STITLE: 



ARRIVAL AND 
DEPARTURE MINIMUMS 

2-12 



iSOURCt . • •■ 

: FederallAviatioTV 
Administration' 



2-8 



^A «$► 



^G° 







4$> 



GATE ASSIGNMENTS 



TERMINAL 2 ^^ E 



UN^N?TyAL) 




/ 



TERMINAL FACILITIES 




OHafiKjOelay Taskforce ;;Study ;| 
ChicagoiO^Hare International 'Airport! 



TITt£ 



O'HARE 
TERJCNAL-GATE COMPLEX 

2-13 



2.3.2 O'Hare's Apron/Cate Complex Has 94 Aircraft Parking Posi 

tions Located on 8 Concourses . 



j Of the 94 total gate positions, 81 are for domestic carrier use 
and 13 for use by international carriers. The 81 domestic gate posi- 
tions have a total gate frontage of 11,493 linear feet, while the 13 
international gates have a total frontage of 2,400 linear feet. The 
assignment of gates for each airline is shown in Exhibit 2-9. Gates 
along Concourse B, C2 and C3 are shared jointly by the internation- 
al airlines and Gates C5, C6, C7 and C8 are shared by Northwest 
Orient, Pan American and Continental. Gates in Concourses D, E, 
F, G, H and K are exclusive-use gates occupied by the domestic air 
carriers. Some gates at O'Hare are shared by more than one air- 
line. This sharing is done in two different ways. The gates may 
be shared on a scheduled basis or may be leased for a single flight 
on a one-time basis when needed by another airline. Each airline 
at O'Hare has a set of gate restrictions which limit the type of air- 
craft that may use a particular gate. 



2-14 



CURRENT SYSTEM PERFORMANCE 



The purpose of this chapter is to present the findings of all analyses 
employed to determine O'Hare's current capacity and current delay levels 
and to identify causes of aircraft delay associated with operations in the 
airspace/airfield and apron/gate systems. The chapter is organized into 
the following five sections: 



Current Airspace/Airfield System Capacity 
Current Level of Airspace/Airfield System Delays 
Causes of Current Airspace/Airfield System Delays 
Delays Due to Short-Term Operating Anomalies 
Current Level of Apron/Cate System Delays 



Three models were used in support of the findings of this chapter: the 
FAA Capacity Model and the City of Chicago AIRSIM and GATES I M models. 
Exhibit 3-1 presents the experiment design matrix which is intended to facil- 
itate cross reference of the input data used to conduct each model experiment 
with the experiment results. In the matrix each row represents a runway con- 
figuration and weather combination; each column represents a specific set of 
ATC equipment, schedule and conditions modeled. The numbers at the inter- 
sections of the rows and columns identify the experiments. The highlighted 
experiments will be used throughout this chapter. Exhibit 3-1A presents a 
summary of the raw data generated by the AIRSIM model for each of the exper- 
iments of interest in this chapter. 



3.1 CURRENT ASRSPACE/AIRFIELD SYSTEM CAPACITY 



In determining current airspace/airfield capacity, the primary objec- 
tive was to arrive at the maximum number of landings, and takeoffs which may 
realistically be processed by various operating runway configurations under 
specific conditions at O'Hare during a one hour period. A secondary objec- 
tive was to assess the overall capability of the facility as it has been operated 
in the past, weighting capacity to reflect the historic utilization of the most 
commonly used runway configurations. To make these determinations, two 
recently developed models, the FAA capacity model (an analytical model) and 
the City of Chicago AIRSIM model (a simulation model) were employed. 



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KEY 


Symbol Dealgnataa 
E Schedule X 
(x) Alr-alm Delay Experiment 1 
f /x\ Celetim Eiperlment 
CX Alr.im Capacity Gi.perlmer.1 • 


Symbol Designate* 

• FAA Capacity Model Run 
NV No Vortex Condition* 
V Vorta* Condition* 

*> Arrival Runwey 

—■—ft Departure Runway 


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O'Hare Delay Taskforce Study ■ ': 
Chicago O'Hare International Airport.' 



EXPERIMENT DESIGN 
CURRENT BASELINE 



SOURCE 

1 Landrum V/Brown , 

.'AIRPORT CQHSU15TANTS 



[EXHIBIT: 

3-1 



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. O'HareVDelay laskforce Study. V T '\j 
Chicago O'Hare International Airport ' 1 


ITU: 




RE 
BA! 


SUL 
>ELI 


TS 

NE 


OF 

EX 


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MEI 


JT 
<TS 








-source-;- y: l ; , : -■- ;•;•>,;'■,; 
t s Landrum A Brown 

^■" - ;! ' ■ -A'tHPORT: CONSULTANTS 


JESH 


•rr: 

3-1 


A 



V 



3.1.1 The FAA Capacity Model Was Employed To Identify The 

Relative Capabilities of 23 Configuration and Weather 
Combinations. 



The hourly airfield capacities as determined by the FAA capacity 
model for each of 23 combinations of weather and configurations ex- 
amined are shown in Exhibit 3-2 . The model is presented in Appen- 
dix D and input data employed in arriving at these capacities are de- 
scribed in Appendix A. The baseline capacities determined by the 
FAA model were based upon an arrival/departure relationship of 53 
percent arrivals. This value was derived by analyzing the quota 
hour!/ activity in September 1975 Baseline Schedule. The quota 
hour from 5PM to 6PM was selected as representative of the current 
peak demand period. 

It should be noted that the capacities determined by the FAA 
model are considered "point estimates", i.e. , each capacity is the 
result of very specific input regarding such variables as aircraft 
mix, and percent arrivals under conditions of continuous demand. 
A change in any input parameter yields a change in the capacity 
achieved by each combination of arrival and departure runways 
called configurations. Further, the degree of change in capacity 
varies by configuration with identical changes in input parameters 
as is illustrated in Exhibit 3-3 for Configurations 1 and 4 for VFR 
ceiling/visibility conditions better than or equal to 1000/3. It can 
be seen that by varying only the percent arrival parameter, the ca- 
pacity fluctuates widely, indicating that capacity is very sensitive 
to the percent of aircraft arrivals. Also, due to physical and oper- 
ational characteristics of each configuration, capacity peaks at a dif- 
ferent arrival/departure relationship for each configuration. Be- 
cause of this sensitivity of the FAA model to this input parameter, it 
is necessary to run the model over a range of arrival /departure in- 
put values in order to fully determine the capacity of an individual 
configuration. However, taskforce budget limitations restricted the 
number of FAA model runs; therefore, it was decided that the model 
would be executed only once for each of 23 combinations of weather 
and configurations. Again, the results are considered point esti- 
mates of capacity in the sense that each represents a single point on 
a graph such as shown in Exhibit 3-3. Although each point is inad- 
equate to determine capacity over the full range of operating condi- 
tions experienced, it is useful in distinguishing the merits of one 
configuration relative to another. In this context, the results of the 
23 FAA model experiments (shown in Exhibit 3-2) were used during 
the taskforce study to identify high performance configurations for 
further detailed capacity and delay analysis. 

1/ Refer to Section 3.3.6.2 for a definition of the quota rule at O'Hare 
and the quota hours. 



3-4 



- 

Configurations 


CAPACITY^ A 


VFR (Operations) ||FR (Operations)* 


1 


140 NC 


2 


NC 


NC 


3 


NC 


111 


4 


140 


111 


5 


140 


111 


6 


141 


NC 


7 


138 


NC 


8 


138 


NC 


9 


137 


111 


10 


136 


NC 


11 


140 


111 


12 


139 


NC 


13 


180 


NC 


14 


139 


110 


15 


141 


111 


16 


127 


111 


17 


139 


NC 



NC: Not Calculated 
A Computation based upon a 53% arrival/47% departure input assumption 

• Ceiling 200 feet and visibility i mile (FAA Model LIFR) 



Note: The data in the above table are not comparable to the data in 
Exhibit 3-4 . See text of Section 3.1.1. 



1 Haref Delay Task fore ^"S^.o. 
Ch'caoovO'Hare Interna? "oria a rporf 



ITITU: 

FAA MODEL CA*ACITY <F) 



-Peat. Marwick., 
"Kiitchell and -Col 



32 



3-9 





MO 


u. 




>- 


120 


O 




2 


100 


< 




o 





20 




20 



40 



Baseline FAA Model Capacity 
53% Arrivals 




Configuration 1 



Range of Quota Hour Variation in 
O'Hare Arrival /Departure Ratio 



60 



80 



100 



PERCENT ARRIVALS 



O'Hare Delay Jaskforce Study 
Chicago O'Hare International A'irport 



TITLE 



ARRIVAL PERCENTAGE 
IMPACT ON CAPACITY (F) 



source ; ; / 

Pe^tvMarwick; 
Mitchell i& CoV 



3-6 



3.1.2 The AIRSIM Model Was Employed to Determine the Capacity , gj\ 

of Configurations Under the Range of Demand Variations 
Experienced During the Quota Hours. The Capacity fST) of 
the Configurations Examined Was Found to Vary in VFR (1000/ 
3 and Above) From 135 to 172 Operations Per Hour and in IFR 
(1000/3 to 500/1) From 125 to 146 Operations Per Hour . 



Since the maximum number of operations which can be processed 
atO'Hare (capacity) varies by hour, even under conditions of satu- 
rated demand, due to changing fleet mix and arrival/departure rela- 
tionship, the taskforce wished to define a capacity indicative of the 
maximum throughput capability of each configuration for the full 
range of demand during the quota hours. Such an evaluation was 
made utilizing hourly throughput statistics from the AIRSIM model 
with a saturated demand schedule. In order to ensure saturated de- 
mand conditions, the September Baseline Schedule was doubled. 
The period of interest was th«j quota hour period, therefore, the oper- 
ations processed under saturated demand conditions for each of the 
3PM-8PM quota hours were averaged to arrive at the AIRSIM capacity 
values shown in Exhibit 3-4. These average throughput values under 
saturated demand (called Capacity (gj)) were considered to be indic- 
ative of actual airfield performance capability, since the AIRSIM model 
reacts to the constantly changing fleet mix and arrival /departure 
variations via the operations schedule. 

The results of the AIRSIM Capacity t$jy analysis are presented 
for selected configurations and weather conditions in Exhibit 3-4. 
As depicted in the exhibit, the Capacity (ST) °* tne configurations 
examined varies from 135 to 172 operations per hour in VFR condi- 
tions of 1000/3 and above. The IFR Capacities ($j) vary from 125 
to 146 for conditions 1000/3 to 500/1. AIRSIM Capacity /^j* statistics 
were not developed for IFR conditions of less than 500/1, which occur 
approximately 4.8 percent of the year. The FAA Capacity tp\ model 
results were assumed to be representative of system capability in 
Weather Condition 4 (ceiling/visibility of 500/1 and below) . The 
AIRSIM capacities presented in Exhibit 3-4 are averages of the 5 
quota hours (data not presented) and should not be confused with 
the hourly throughput values presented in the exhibit which are 
based upon the September 1975 demands. Hourly capacity varies 
due to demand factors, generally in a range of plus or minus 5 oper- 
ations per hour over the 5 hours examined. 



3-7 




Capacities for weather categories 1 
representative of weather category 
Not calculated. 



and 3 are Capacity (ST) . Capacities used as 
4 (500/1 and below) are Capacity (F) . 



O'HaretDelay Taskforce Study 
Chicago O'Hare International Airport 



titii: 



BASELINE CAPACITY 
/THROUGHPUT 



Landrurri & Browrv, 

*IPPORT;;.CONSUl.TANTS ; : 



3-8 



At this point, the definition of Capacity (ST) as determined by 
the AIRSIM model should be further qualified. The results obtained 
were based upon assumptions of normal controller workloads. The 
difference between normal and demand workload as modeled by 
AIRSIM is fully explained in Appendix B. Simply stated, demand 
workload logic within the model simulates the air traffic controller's 
ability to reduce the normal buffers moving closer to the target sep- 
aration standards for short periods under heavy demand conditions. 
In effect, the controllers at O'Hare frequently work at a rate greater 
than normal for short periods of time in order to expedite the pro- 
cessing of heavy demand on the system. It was felt unrealistic to 
define capacity at a work rate that cannot be realistically sustained 
for prolonged periods of time. 

In order to fully interpret the data in Exhibit 3-4, it is important 
that the reader fully understand why throughput can actually exceed 
Capacity r$j\ . It was explained above that for short periods of time, 
O'Hare controllers frequently process more than their normal work- 
load of aircraft in order to process demand backlogs. For the pur- 
poses of this study, capacity was defined to be a normal controller 
workload. Therefore, under periods of heavy demand and increased 
controller workload, it is possible to process aircraft in excess of the 
level defined as capacity. 



3.1.3 The Quota Hour Throughput in September 1975 Ranged 

From 87 to 98 Percent of Capacity (ST) For the VFR and 
IFR Configurations Investigated . 



The relationship between throughput and Capacity (sjj during 
the quota periods was identified for the most commonly used config- 
urations at O'Hare. Exhibit 3-4, which presents Capacity (ST) sta ~ 
tistics, also depicts the quota hour throughput for each configura- 
tion based upon the September 1975 Baseline Schedule. These quota 
hour throughputs were averaged to estimate an average volume of air- 
craft processed for the quota hour for comparison with the Capacity (ST) 
determined in Section 3.1.2. Throughput for each configuration was 
then expressed as a percent of configuration Capacity tcj\ and graphed 
for each configuration investigated by the taskforce. The results of 
this analysis are presented in Exhibit 3-5 and indicate that average 
VFR and IFR quota hour throughput falls in a region from 87 to 98 
percent of configuration Capacity (ST) • The delay implications of 
high throughput/Capacity /g-j- j ratios will be shown in Section 3.2.4. 



3-9 





J 


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70 




AVERAGE QUOTA HOUR THROUGHPUT ASA PERCENTAGE OF CAPACITY 



(ST) 



Short-term capability when arrivals exceed 60%. 
Configurations identified in the historic use pattern 



O'Hare Delay Taskforce Study 
Chicago O'Hare International Airport 



mar 



THROUGHPUT/CAPACITY, ST J 
RELATIONSHIPS 



Land rum: & 

. -'. AIRPO«T.:.e6W:S,Ul:TiANTS. 



1EXMNMT 



3-10 



3.1.4 Based Upon the Way O'Hare Has Been Operated in the Past 

(Historic Configuration Use), the Current Average Capacity n/yA) 
Is 141 Operations Per Hour. O'Hare's Weighted VFR and IFR 
Capacities (WA) Currently Average 143 and 126 Operations Per 
Hour Respectively . 



The historical use of runways, by configuration, was estimated 
based upon review of tower records and discussion with O'Hare 
controllers. The pattern of historic runway usage shown in Ex- 
hibit 3-6 is similar in form to that presented in the 1974 FAA Report 
on runway capacity. 1/ The average weather and configuration use 
weighted hourly capacity which results from the pattern of historical 
use of the runway system at O'Hare is a useful index. The taskforce 
arrived at this value for both VFR and IFR weather conditions; the 
methodology employed was to establish an average hourly VFR and 
IFR capacity weighted to reflect the historic usage of O'Hare's pri- 
mary configurations as presented in Exhibit 3-6. In the analysis 
conducted, AIRSIM Capacities (ST) were employed for weather con- 
ditions down to 500/1 and a representative IFR Capacity (pj (from 
the FAA capacity model) was used to represent the IFR weather be- 
low a 500 foot ceiling and 1 mile visibility. The resulting average 
Capacities (WA) are reflective of the full spectrum of demand, weather 
and configuration variations experienced over the course of a year. 
The values are a good indicator of the capability achievable with past 
operating procedures and configuration selection practices. As will 
be demonstrated in other sections of this report, the values should 
not be viewed as the maximum capability of the existing O'Hare air- 
field facility, but rather the capability realized as a consequence of 
current airfield operating procedures. 



3.1.5 FAA Air Traffic Service's Engineered Performance Standards 

(EPS) Are Mathematically Based System Operating Efficiency 
Measures Which Are Not Directly Comparable With the Individ - 
ual Configuration Capacities Calculated by the FAA and AIRSIM 
Models. 



In conjunction with the FAA Air Traffic Service Performance 
Measurement System (PMS), system acceptance standards have been 
set for use in evaluating airfield/airspace system and air traffic con- 



1/ FAA Report on Airport Capacity; No. FAA-EM-74-5, Volume 1, 

FAA/DOT - January, 1974. 



3-11 



CONFIGURATION 


TASK FORCE 

CONFIGURATION 

NUMBER 


WEATHER CONDITION 


TOTAL USE* 


VFR 

GREATER 

THAN 1000/3 


IFR 

LESS 

THAN 1000/3 


fc 


1 


28.3% 


- 


28.3% 


& 


6 


20.2% 


- 


20.2% 


<\—/ 


3 


6.4% 


5.5% 


12.9% 




2 


12.2% 


- 


12.2% 


♦ 

^ 


• 
14 


7.2% 


5.7% 


11.9% 




18 


6.0% 


- 


6.0% 


"%. 


a 


1.2% 


4.0% 


5.2% 




n 


3.3% 


- 


3.3% 


TOTAL 
OCCURANCE 


- 


84.8% 


15.2% 


100% 



Estimated based upon tower records and controller observations. 

Representative of typical IFR configuration performance-parallel 
arrivals/mixed departures used in ceiling and visibility conditions 
below 500/1 or in high wind velocity situations. 



'"- O'Hare Delay Taskforce Study 
Chicago O'Hare International Airport 



HISTORIC RUNWAY 
USE PATTERN 



Taskforce 



3-12 



trol staff performance. Termed Engineered Performance Standards 
(EPS) and commonly referred to as "EPS capacities", they are mathe- 
matically based system operating efficiency measures, which by 
taskforce definition are not "capacities"--capacity being defined for 
taskforce purposes as the maximum number of aircraft operations 
which may be processed given a set of input assumptions, including 
in all cases, continuous demand on the system. As "standards" they 
are rules for measurement of performance which are established by 
general consent as a criterion or goal . As applied at O'Hare, the 
EPS values are realistically average system throughput numbers 
representing goals consistently achievable by controllers given the 
full spectrum of day-to-day variations in the factors in play in the 
system. The initial standards, shown in Exhibit 3-4, have been 
simplified in presentation to a single value rather than a complex 
matrix of values to facilitate their practical use in the field. 

In practical application, rather than reflect a system perform- 
ance deterioration corresponding to separation increases as a func- 
tion of weather condition, the EPS values have been established for 
average separation standards, fleet mix, and weather including 
Category II and above. When system throughput drops below the 
EPS rating, factors causing the drop are to be identified, i.e.: in 
low ceiling and visibility conditions, weather would be noted as the 
reason for system performance at less than standard rates. The 
taskforce evaluation, on the other hand, provides full quantitative 
definition of the system performance capability of specific config- 
urations in various weather categories. 

Also, the EPS values reflect an equalized number of arrivals 
and departures, i.e. , if the capability of a configuration is 40 arriv- 
als per hour and 47 departures per hour, the EPS rating would be 
indicated as 80 total operations per hour. The taskforce capacity 
(i.e., Capacity (ST)) would indicate the full configuration perform- 
ance capability of 87 operations per hour. 

Although the EPS values are not directly comparable to the FAA 
and AIRSIM model results for each specific configuration, the 132 
EPS rating for O'Hare appears to be a reasonable indicator of the 
average system throughput rates achievable with past O'Hare oper- 
ating procedures and configuration selection practices. The EPS 
rating is 93.6 percent of the historic average weighted capacity of 
141 operations per hour defined in previous Section 3.1.4. The 93.6 
percent value falls within the region of current O'Hare configuration 
throughput vs. Capacity jst) relationships identified in Exhibit 3-5. 



3-13 



3.2 CURRENT LEVEL OF AIRSPACE/AIRFIELD SYSTEM DELAYS 



Having established that the relationship of O'Hare capacity to current 
throughput varies as a function of the operational configuration and weather con- 
dition under evaluation, it is necessary to examine the efficiency with which that 
throughput is realized. Notwithstanding adequate capacity or flow rate, if 
lengthy delays are incurred by aircraft operating within the airspace/airfield 
system, the overall system may be performing inefficiently. Therefore, the most 
meaningful measure of airspace/airfield system performance is the delay incurred 
by aircraft operating within the system. Because delay as a measure of system 
performance is easily translatable into cost, a comprehensive analysis was con- 
ducted in order to establish the delay characteristics of key O'Hare operating 
configurations. 



3.2.1 The AIRSIM Model was Used to Determine the Current Delay 

Characteristics of 22 Different Combinations of Weather and 
Runway Configurations. Average Delay Per Operation in VFR 
Weather Ranged From 2.4 to 9.6 Minutes for the Configura- 
tions Studied. Average Delay Per Operation for the IFR Con- 
figurations Studied Ranged from 5.9 to 16.8 Minutes . 



The AIRSIM model was used in conjunction with the September 
1975 Baseline demand and the new (November 15, 1975) air traffic 
separation standards to simulate the operations at O'Hare from 8AM 
to 8PM for 22 combinations of weather and runway configurations. 
The output from these simulation experiments provided not only the 
hourly numbers of operations processed (i.e., throughput), as dis- 
cussed in Section 3.1.3, but also the delays incurred by these oper- 
ations. 

In order to understand fully the output from the simulation exper- 
iments, it is necessary first to discuss briefly two different methods 
used with the AIRSIM model for recording delays. As will be seen 
in later exhibits, delays are tabulated by the model on an hourly 
basis. The first method of tabulation is by processed times, that is, 
the delay incurred by an aircraft is recorded in the hour during which 
it is processed (time aircraft wheels touch-down or lift-off from run- 
way pavement) . The second method is by scheduled times, meaning 
that the delay incurred by an aircraft is recorded in the hour during 
which the operation was scheduled to occur, regardless of when it 
actually occurred. All time related statistics generated by the model 
were available in either accounting mode; however, the results have 
generally be reported on a processed basis except as where noted 
in the exhibits. 



3-14 



Exhibit 3-1A presents a summary of the raw data generated by the 
AlRSIM model for each of the 22 baseline configuration/weather com- 
binations simulated. All the data were presented on a processed 
basis with the exception of the hourly quota period statistics regard- 
ing arrival delay, departure delay, and average delay per operation. 
These data were presented on a scheduled basis to facilitate compari- 
sons with airline management records, which are generally kept in 
this fashion. 

The configurations investigated by the taskforce displayed a 
wide range of delay characteristics. These characteristics are most 
easily examined by converting the raw data of Exhibit 3-1 A into a 
graphic format as has been done in Exhibit 3-7 for average delay 
per operation . 



3.2.2 For the VFR Configurations Studied, Maximum Peak Hour De- 

lays Are 68 Percent Higher Than the Average Daily Delay. 
For the IFR Configurations Studied, Maximum Peak Hour De- 
lays Are 136 Percent Higher Than the Average Daily Delay . 



Exhibit 3-1A presents, in addition to average delay per operation 
over the period 8AM to 8PM, much useful information about the delay 
characteristics of the configurations examined. When dealing with 
average daily delays, it must be remembered at all times that an aver- 
age delay, which appears reasonable over the period of a day, may be 
a result of many high delays (during peak hours) and many low de- 
lays during off-peak hours. This fact is the principal reason for seek- 
ing information additional to the daily average delay statistics. Ex- 
hibit 3-7 also depicts the average delay for the configurations studied 
during the quota hours. Note that in this and subsequent discussions 
the terms "peak hours", "quota period", and "quota hours" are used 
interchangeably . 

As an example of how the information in Exhibit 3-7 should be in- 
terpreted, consider the relationship of average daily delay to maxi- 
mum and average peak hour delays for Configuration 1 in VFR weather 
better than or equal to 1000/3 and Configuration 3 in IFR weather con- 
ditions down to 500/1 . In Configuration 1, maximum hourly delay 
occurred between 6- 7PM (7.4 minutes) and was found to be 68 per- 
cent higher than the average total delay over the entire day, while 
average peak hour delay was 25 percent higher than the daily average. 
From the delay distribution in Exhibit 3-1A, it can be determined that 
no aircraft experienced total delays exceeding 30 minutes while one 
percent experienced delays between 20 and 30 minutes. The peak 
hour delay of 7.4 minutes as compared to the daily average of 4.4 min- 
utes is not unusual for the configuration utilized in VFR weather at 
O'Hare. 



3-15 



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DELAY PER OPERATION 
(minutes) 

Note: 

The numbers in parentheses denote the highest 
average peak hour delay (in minutes) . 



OHare Delay Taskforce Study 
Chicago OHare International Airport 



WERAGE DAILY ANDPEAK H( 
DELAY BY CONFIGURATION 



Landrurir & Brown' 

. AIRPORT CONSULTANTS. 



9CXHNNT: 

3-7 



3-16 



In Configuration 3, maximum average peak hour delay also 
occurred between 6-7PM and was 125 percent higher than the daily 
average of 9. 6 minutes per operation. The peak hour average de- 
lay of 21 .6 minutes per operation with 5 percent of all aircraft pro- 
cessed experiencing delays exceeding 30 minutes is noteworthy, 
particularly considering that this configuration has historically 
been the predominant one utilized in IFR, and that reduced capac- 
ity in low ceiling and visibility conditons less than 500/1 are not 
considered in this evaluation. 



3.2.3 The Average Daily and Hourly Delays Per Operation Sustained 

By Current O'Hare Activity Are Directly Related to the Capac- 
ity ($T) of the Configuration Being Utilised and the Prevailing 
Ceiling and Visibility Conditions . 



Exhibit 3-8 graphically depicts the current relationship between 
Capacity (ST) and average daily and average peak hour delay for the 
O'Hare configurations examined by the taskforce. Three distinct re- 
lationships have been identified from the capacity and delay statistics 
of the individual configurations. These sets of curves represent: 



VFR operating conditions (1000/3 and above) - expressed 
as curves through plots of the daily (8AM to 8PM) aver- 
age delay and quota hour (3PM to 8PM) average delay 
versus the VFR Capacity (^j\ of each configuration. 

IFR operating conditions (1000/3 to 500/1) - expressed 
as curves through plots of the daily and quota hour aver- 
age delay versus the IFR Capacity (£T) °^ eacn configur- 
ation . 

VFR three arrival runways (1000/3 and above) - curves 
depicting the unique arrival/departure relationships, 
having both high Capacity (ST) an ^ relatively high delay, 
of 2 three-arrival runway configurations studied by the 
taskforce. 



Examination of the results of this analysis clearly illustrates sever- 
al important aspects of the O'Hare capacity /delay relationship. First, 
distinctly different operating conditions result from the air traffic sep- 
aration standard variations between VFR and IFR weather. Second, 
with the exception of the triple arrival configurations which are fully 
discussed in Section 4.1.1, the average daily and hourly delays are 
directly dependent upon the Capacity (sj) of the configurations— the 



3-17 



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The numbers denote configurations. 



VFR Daily Average 
IFR Daily Average 
VFR Peak Hour Average 
IFR Peak Hour Average 
Daily 8AM -8PM 
Quota Hours 3PM-8PM 



THREE ARRIVAL 
RUNWAYS 

(see Section 4.1.1) 



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130 



140 



150 



160 



170 



CAPACITY (ST) 



O'Hare Delay Taskforce Study 
Chicago O'Hare International Airport 



ITTTLE: 



DELAY VS CANITY 



(ST) 



DAILY AND PEAK HOUR 

3-18 



L a n d r u m y& B r dvyh & 

AIRPQftT CONSULTANT* 



jCXKtaiT 

3-8 



less efficient (low capacity) configurations producing the highest de- 
lays regardless of weather conditions. A third finding illustrates the 
sensitivity of less efficient configurations to the heavy demand exper- 
ienced during the quota hours. Quota hour average delays exceed 
daily averages in the most efficient VFR configurations by approxi- 
mately 20 percent; while in the less efficient configurations, quota 
hour delays exceed daily delays by up to 45 percent. In IFR weather, 
the quota hour delay is even more sensitive, the efficient configura- 
tions reflecting a 70 percent increase in quota hour versus daily de- 
lays, while in the low capacity configurations quota hour delay ex- 
ceeds daily delay by approximately 120 percent. 



3.2.4 Current Hourly Throughput Is Approaching the Capacity of 

Many of the Most Frequently Used Configurations At O'Hare 
Resulting in High Delay Sensitivity, Particularly in IFR 
Weather Conditions. 



In Section 3.1.3, the ratio of throughput to Capacity (sy) was 
identified for numerous O'Hare configurations including those most 
frequently used in the past. This analysis was extended to deter- 
mine the relationship between the throughput/Capacity «j-rj ratio 
and delay resulting from aircraft processed at O'Hare as it has been 
operated historically. The historic pattern of runway use was de- 
fined in Exhibit 3-6. 

In this analysis, the average quota hour throughput/Capacity (ST) 
ratios depicted in Exhibit 3-5 were plotted against the average daily 
delay levels of each of the configurations identified in Exhibit 3-6. 
Thus the data points for each configuration are averages which are 
derived from the full spectrum of operating conditions experienced 
including variations in fleet mix, arrival/departure ratio, demand 
level, configuration and weather conditions, and represent the range 
within which O'Hare has historically operated, From these data points, 
it was possible to construct delay curves which generally define the 
O'Hare delay versus throughput/Capacity (§j) relationship in VFR 
and IFR weather conditions. The results of this analysis are pre- 
sented in Exhibit 3-9. 

From the exhibit, it may be seen that in VFR conditions the more 
efficient configurations at O'Hare, which typically operate at 85-90 
percent of capacity, yield average daily delays of 3 to 4 minutes with 
less efficient ones operating at 95 percent or more of capacity with 
average daily delays ranging to 9 minutes. The IFR configurations 
are shown to operate typically from 90 to 100 percent of capacity and 
the extreme sensitivity to delay is evident: for instance, at 95 to 100 
percent of configuration capacity, average daily delay may range any- 
where from 6 to 15 minutes or more. Clearly, delay rises significant- 
ly as throughput approaches configuration capacity. 



3-19 



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AVERAGE QUOTA HOUR THROUGHPUT* CAPACJTY (ST) x 100'/. 



■ VFR 
• IFR 



OHare Delay Taskforce Study 
Chicago O'Hare international Airport 



TITue DELAY VS 

[THROUGHPUT -=- CAPACITY (ST) 



landrum 4 Brown 

~> AIRPORT CONSULTANTS 



3-20 



3.2.5 Based Upon the Historic Pattern of Runway Use, Delays to 

O'Hare Aircraft Operations Under Normal Operating Condi - 
tions Are Estimated to Exceed 77,000 Hours Annually . 



Since delay within the Chicago terminal airspace area is not a 
directly observable phenomena, the airspace/airfield simulation 
model "AIRSIM" was employed as a tool with which to measure annual 
expected delay in the Chicago O'Hare airspace/airfield system. The 
following paragraphs describe the methodology employed and the re- 
sults obtained in that analysis. 

It should be stated at the outset that no standard exists which en- 
ables an analyst to infer knowledge of the nature of annual delays at 
an airport from a knowledge of daily delays. By using digital simula- 
tion techniques it is relatively simply to obtain accurate estimates of 
delays for a specific period of time (e.g., 8AM to 8PM). However, 
these estimates are "point estimates" only; that is, they are accurate 
only for the specified input parameters and assumptions. Obviously, 
the most accurate estimation of annual delays could be obtained by 
making 365 estimates, each with the specific characteristics of a par- 
ticular day of the year (configuration, demand, weather, etc.). In 
this manner, the delays occurring on each day of the year simulated 
could simply be totaled to yield an accurate estimation of annual de- 
lay. Although this technique would be the most accurate technique 
to employ for estimating annual delays, it would also be expensive 
and time consuming. Further, for planning purposes, the informa- 
tion gained would not be worth the time and money expended. 

The "annualization methodology" used to estimate O'Hare's cur- 
rent annual delays makes use of the pattern of configuration use at 
O'Hare which was identified in Exhibit 3-6. Each of these configu- 
rations was simulated in order to estimate arrival, departure, and 
average delays from 8AM to 8PM. The results (capacity and delay) 
have previously been shown in Exhibits 3-1A and 3-4 for all the con- 
figurations investigated. The average arrival and departure delays 
were adjusted to arrive at a weighted average delay which, for each 
configuration, was multiplied by the total annual days in which each 
configuration is expected to be in use (based on prior use patterns) . 
The final step in the "annualization methodology" was to adjust the 
annual delays for 12 hour days to represent the annual delays for 
24 hour days. This was accomplished by assuming that 85.7 percent 
of the total delays (therefore delay costs also) are accumulated in the 
period 8AM to 8PM. This assumption was based upon simulation ex- 
periments conducted over a 24 hour period which, when compared to 
the same experiments over a 12 hour period (8AM to 8PM), indicate 
that 85.7 percent of O'Hare's total delay does, in fact, occur between 
8AM to 8PM . 



3-21 



In order to arrive at weighted average arrival and departure 
delays, monthly operations data were analyzed for the period 1971 
to 1974. These data indicated that, on the average, demand during 
the month of September is 98.5 percent of average annual demand. 
Although the relationship between demand and delay is not linear, 
over the small range of deviations of actual monthly demand from 
average monthly demand, a linear relationship was assumed. There- 
fore, the total arrival and departure delays produced for a simulated 
day in September were divided by .985 to yield an approximation to 
the delays to be expected for a day in an average month. This meth- 
odology tacitly assumes that daily demand is at an equal level for days 
within the same month. The estimates of annual delay resulting from 
this methodology are presented in Exhibit 3-10 for the historic 
O 'Hare operating pattern identified in Exhibit 3-6. 

It should be noted that these delays represent normal operating 
conditions at the airport and do not reflect delay levels which are at- 
tributable to anomalousl/ operating circumstances. Operating anoma- 
lies are discussed in Section 3.4 of this chapter. Several factors are 
known to influence delays which are either not included in the anal- 
ysis or are difficult to accurately account for. Some of the factors 
which would cause the annual delay estimates to be conservative are 
briefly discussed below. 



The functional relationship between demand and delay 
is not linear. For example, a 10 percent decrease in 
demand may cause a 5 percent decrease in delay while 
a 10 percent increase in demand may result in a 25 per- 
cent increase in delay. This relationship varies with 
each configuration. 

Daily shifts in runway or configuration usage have not 
been accounted for. When the active arrival and de- 
parture runways are shifted, delays are generally in- 
creased . 

Only VFR weather adequate for visual approaches 
(better than 3500/5) and IFR weather (down to 200/ i) 
were considered. Delays during VFR weather worse 
than 3500/5 and in IFR weather less than 200/ i are 
higher than those included in the analysis. 



1/ In the remainder of this report, anomalous and abnormal are used 
interchangeably. As an adjective preceding demand or operating 
conditions, they refer to circumstances out of the ordinary such as 
severe thunderstorms or runway construction activity, which cause 
extreme disruptions to operations at O'Hare. Refer to Section 3.4 
for a detailed discussion of operating anomalies. 



3-22 



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hicao/o Mare iniernattdliai Airport 



title CURRENT 

ANNUAL BASELINE 
DELAY 



'Land rum & Brown 

AiPROCTro^suiTANTS 



9CXMWT: I 

3-10 



3-23 



The only perceived possibility for overstating annual delay 
arises from the fact that the methodology assumes equality between 
weekend demand (and, therefore, delays) and weekday demand. 
The overall effect of this possible overstatement is more than can- 
celled by the factors discussed above, yielding a conservative esti- 
mate of delay under normal operating conditions. 



3.2.6 Based Upon The Way The Airport Has Been Operated in The 

Past, Current O'Hare Delays Result in $35,900,000 in Direct 
Operating Costs Annually to Aircraft Operators . 

Having established the current pattern of delay at O'Hare under 
normal conditions, the current annual cost of delay to aircraft oper- 
ators was estimated. The purpose in estimating current delay re- 
lated direct operating costs was to establish a "baseline" against 
which the benefits of delay reduction options could be measured in 
dollars by the taskforce. 

In the analysis employed to predict the cost of current arrival 
and departure delays, the total arrival and departure delay minutes 
defined in Exhibit 3-10 were converted to dollar costs assuming the 
weighted average estimated costs for crew, fuel, oil, etc., for 
O'Hare's current fleet mix as depicted in Exhibit 3-11. The results 
indicate the costs of delay under normal conditions (about 77,000 
hours), as the airport has been operated in the past, are approxi- 
mately $35,900,000 annually. 



3.2.7 The Currenf Level of Aircraft Delay Is Estimated to Result in 

4,600,000 Annual Hours of Passenger Delays. 



In addition to the direct operating cost implications described in 
the previous sections, O'Hare air travelers suffer numerous hours 
of inconvenience. While it is difficult to quantify in absolute terms 
the magnitude and cost of inconvenience to the traveling public, an 
estimate of passenger hours was developed. An average load factor 
per aircraft arrival or departure was assumed; for scheduled air 
carrier the load was 66 passengers, for air taxi and commuter air- 
craft 6, and for general aviation operations 4 passengers per aircraft. 
At the current passenger demand level, 4,600,000 hours of delay are 
nominally incurred annually by O'Hare air travelers. While this esti- 
mate is at best a generalization, it conservatively defines the magni- 
tude of O'Hare delays today and provides a major incentive to the 
FAA, the City and the air carriers in choosing meaningful delay re- 
duction measures. In the definition of the benefits of alternative de- 
lay reduction options discussed in the balance of this report, it is 
left to the reader to assess the significance of these passenger delays 
in economic terms. 



3-24 



1975 WEIGHTED FLEET OPERATING COST 
AND FUEL CONSUMPTION RATE 



Representative 
Aircraft 




Direct Operating 


Fuel Consumption 


Percentage 


Cost Per Minute 


Per Minute 


Type 


Current Mix 


(dollars) 


(pounds) 


Ground 


Airborne 


Ground Airborne 


B-747 


1.9 


$13.30 


$25.20 


125 


345 


DC-10 


8.5 


10.00 


17.00 


65 


205 


DC-8/B-707 


12.8 


8.00 


13.20 


75 


170 


B-727 


37.1 


6.40 


10.10 


55 


125 


B-737 


18.4 


5.10 


7.50 


35 


75 


GA Jet 


2.0 


3.00 


5.00 


15 


30 


2 Engine Prop (+12,500) 


6.5 


3.00 


5.00 


10 


25 


2 Engine Prop (-12,500) 


12.8 


2.00 


2.50 


' 1.7 


3.4 


1 Eng Prop 
Weighted Average 


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Current O'Hare Fleet 


100.0 


$ 5.95 


$ 9.48 


45.5 108.6 

1 1 



CURRENT ANNUAL DELAY COST AND FUEL CONSUMPTION 







Estimated Current 
Annual Delay 
Minutes 


Weighted 
Cost Per 
Minute 
(Dollars) 


Annual 
Cost of 
Delay 
(Dollars) 


Weighted 
Fuel 

Consumption 
Per Minute 
(Gallons) 


Current 

Annual 

Fuel 

Consumption 

(Gallons) 


8AM -8PM 


24 Hour Day 


Arrival 
Departure 
Total 


1,990,642 
1,997,371 
3,988,013 


2,322,803 
2,330,655 
4,653,458 


$9.48 
$5.95 


$22,020,172 
$13,867,397 


16.2 
6.8 


37,629,408 
15,848,454 
53,477,862 

I 


$35,887,569' 



O'Hare Delay Taskforce|iStudv 
Chi c ago O Hare Internat i o'ipa I A i r d o r t 



CURRENT DELAY COST 
&HP FUEL CONSUMPTION 

3-25 



, Lia no r u m A B r o w n 



3.3 CAUSES OF CURRENT AIRSPACE/AIRFIELD SYSTEM DELAYS 



Six key factors have been identified as the principal causes of airspace/ 
airfield system delay at Chicago's O'Hare International Airport: 



The Proximity of Other Airports to O'Hare, 

Air Traffic Control Rules, Regulations and Procedures, 

Physical Properties of the Airspace/Airfield, 

Meteorology, 

Operational Procedures, and 

Aircraft Operating Demand. 



The impact of these factors on delay at O'Hare is discussed in the following 
paragraphs . 



3.3.1 The Proximity of Other Airports to O'Hare Affects O'Hare Delays 

The proximity of other airports to O'Hare affects delays to the 
extent that their operations limit the paths over which aircraft may 
be vectored to and from O'Hare, or must be coordinated through 
Chicago approach control or O'Hare Tower. 

For example, Midway traffic generally circumnavigates O'Hare 
except when O'Hare arrivals are landing on Runway 32L and Midway 
arrivals are landing on Runway 13R. In this instance, the approaches 
cannot be conducted simultaneously, thereby reducing the capacity 
and increasing the delays at both airports. Similarly, when 4L is the 
active departure runway at O'Hare and an aircraft is arriving at 
Palwaukee or Clenview, the ORD Tower controller must either coor- 
dinate ORD departures with the TRACON north satellite controller or 
hold 4L departures until the arrival is clear. Palwaukee departures 
do not affect ORD 4L departures; however, Clenview departures do, 
to some extent. 

Clenview operations affect not only ORD 4L departures, but 22R 
and 22L arrivals as well. When landing on either of the parallel 22 
runways at O'Hare, a gap must be made in the arrival stream to accom- 
modate a Clenview arrival or departure. 



3-26 



3.3.2 Air Traffic Control Rules, Regulations and Procedures Have a 

Significant Impact on O'Hare Delays . 



Although designed to ensure operational safety in the airfield en- 
vironment, certain ATC rules, regulations and procedures limit, to 
some extent, total system capacities achievable and affect airfield 
delays. While ATC rules and regulations are absolutely necessary 
for safety of operation, their relationship to capacity and delay should 
be understood. The rules and regulations most affecting capacity 
and delay are those regarding separation requirements between ar- 
riving and departing aircraft. The impact of these rules and regula- 
tions on capacity and delay at O'Hare is briefly discussed in the fol- 
lowing paragraphs. While this discussion does not suggest possibil- 
ities for delay reduction through rules and procedures, it does ex- 
plain why a certain level of delay is inherent in the operations at any 
airport. 



Arrival/Arrival Separations , limit the effective arrival 
capacity of the airfield because of the constraints they 
impose on the airspace structure's ability to deliver air- 
craft to the pavement. Total operational capacity and 
consequently delays of a single mixed operations run- 
way or an arrival/departure runway pair are greatly 
affected by the separations inasmuch as departures are 
interspersed between arrivals. 

An example of the impact of arrival/arrival separations 
on system performance occurred recently when the ATC 
rules for "small" aircraft were introduced in November, 
1975. In the early phases of the taskforce study, a series 
of experiments were conducted against a January 1975 
operations schedule. The results of these experiments 
were termed the January baseline results. When the ATC 
rule changes were announced to go into effect on Novem- 
ber 15, the same set of experiments was again conducted, 
this time against the new September operations schedule. 
As would be expected, a general trend toward increas- 
ing inbound delays was noted since an increase in sep- 
aration implies fewer aircraft in the same airspace sim- 
ultaneously. Although some arrival/arrival gaps were 
increased, the increase on the average is not enough 
to process an additional departure over the number which 
would usually be processed under the old rules. Thus, 
the extra time is "wasted" insofar as departures are con- 



3-27 



cerned and, in general, the departure delay increased 
in November over that experienced in January for the 
same configurations. The degree of increase attributable 
to the new separation standard for small category aircraft 
versus that due to demand variations between the January 
and September schedules was not ascertained. In sum- 
mary, the total delay per operation is expected to aver- 
age 1 to 6 percent higher at O'Hare under the new ATC 
separation rules than under the old rules. 

Arrival/Departure Separations on Intersecting Run- 
ways are critical to the capacities and delays sustained 
by certain operational runway configurations at O'Hare. 
ATC rules require that a departure be through the inter- 
section prior to threshold crossing by an aircraft arriv- 
ing on the other runway of the pair. However, landing 
clearance for arriving aircraft is generally not withheld 
when there is reasonable assurance that proper separa- 
tion will exist when the arrival crosses the landing 
threshold. Operationally, this means that so long as vis- 
ibility remains great enough for the tower controller to 
see traffic, separations between arrivals and departures 
on intersecting runways are anticipated by the control- 
lers. The inability to anticipate separations in poor vis- 
ibility conditions greatly reduces capacity and increases 
the delay sustained by departures when operating on 
intersecting runways. 

Another ATC safety consideration which affects capacity 
and delays on intersecting runways is wake turbulence. 
If a heavy arrival passes through an intersection in the 
air and the departure on the intersecting runway is an- 
ticipated to fly through the airborne path of the arrival, 
then the departure cannot be released until two minutes 
after the arrival has passed through the intersection. 

Departure/Arrival Separations on Intersecting Run- 
ways are also critical to capacities and delays incurred 
by some operational configurations at O'Hare. Particu- 
larly affected are those involving large numbers of heavy 
aircraft departures on runways with distant intersections. 
If a heavy departing aircraft is airborne at the inter- 
section, ATC rules state that an arriving aircraft cannot 
pass through the intersection until two minutes have 
elapsed if the arrival will fly through the airborne path 
of the departure. This rule necessitates, in some cases, 
an even larger gap between arrivals then is required 
from arrival/arrival separation standpoint, in order to 
meet wake vortex separation requirements. 



3-28 



Departure/Departure Separations on the same runway 
are, in general, not detrimental to airfield capacity and 
delay. However, airspace limitations which prevent 
a controller from "fanning" departures in different di- 
rections, and wake turbulence are two considerations 
which cause departure/departure separation to impact 
on capacity and delay. Airspace limitations, more ac- 
curately, affect the ability of the airspace to accept de- 
partures — not the ability of the airfield to deliver. Wake 
turbulence generated by heavy departures forces suc- 
ceeding non-heavy aircraft to delay their departure in 
order for the turbulence to subside. 



3.3.3 Physical Properties of the Airspace/Airfield Influence Delays 



The physical properties of O'Hare's airspace/airfield determine 
not only the ability of the entire system to accommodate various air- 
craft types, but also the operating efficiency, in terms of capacity 
and delay, of the configurations in which the airfield functions. The 
following physical properties of the airspace/airfield influence delays 
at O'Hare. 



Obstructions 

Displaced threshold on Runway 4R (removed in 1975) 

Shoulders on Runways 4L/22R and 9L/27R (corrected 

in 1975) 

Intersection and Exit locations 



The significance of these physical properties as they relate to delays 
is discussed in the following paragraphs. 



Obstructions , particularly the WGN radio tower to the 
west of O'Hare, impact not oniy delays experienced in 
some configurations at O'Hare, but also the ease with 
which controllers are able to make the configurations 
function . 

Whenever the weather at Chicago necessitates the use 
of departure Runways 32R and 32L and ceiling visibil- 
ity are less than 1,000 feet and 3 miles, respectively, 
the WGN radio tower dictates more demanding control 
techniques than would ordinarily be required on other 



3-29 



similar configurations. The reason for the demanding 
techniques is that 32L departures are required, under 
the above stated ceiling/visibility limits, to proceed on 
runway heading until reaching 1,500' mean sea level 
(MSL) prior to initiating a left turn (to assure obstacle 
clearance criteria) . The impact of this restriction is 
lost, however, without an understanding of the way in 
which the overall configuration functions. 

Generally, when departing 32R and 32L, 27R is used 
as one of the active arrival runways. The control pro- 
cedure for processing aircraft on these three runways 
is as follows: A landing on 27R clears the 32R inter- 
section whereupon the 32R departure is released; when 
radar separation from the 32R departure is achieved, 
the 32L departure is released. Ordinarily, when in a 
parallel departure configuration, takeoffs are "fanned" 
to either side of the extended runway centerline, allow- 
ing successive departures to be quickly released; how- 
ever, with the restrictions due to the WCN tower, 32L 
departures may not be fanned and must follow the run- 
way heading until reaching 1,500' MSL. Therefore, 
under circumstances where the 32L departure would 
normally initiate a turn from runway heading to allow 
for a departure to release on 32R, the tower restriction 
causes the 32R departure to hold, incurring delay. 
This hold, in many instances, causes a "domino effect" 
on delays because of the interrelationship between 32L 
and 32R departures and 27R arrivals. 

A Displaced Threshold on Runway 4R and Departure 
Restrictions on Runway 22L existed until 1975 due to 
problems with the operation and facilities of a railroad 
yard lying under the 4R approach. These restrictions 
have limited the use of several low delay configurations 
embodying this runway. With the displacement, Run- 
way 4R was too limited to adequately serve the entire 
aircraft fleet. 

The Shoulders on Runway 4L/22R and 9L/27R have 
been a source of minor delay and inconvenience at O'Hare 
because of their width which, until the 1975 summer con- 
struction program, was inadequate to allow the takeoff 
of 747 aircraft. Prior to the construction, all 747 depar- 
tures were segregated from these runways. 



3-30 



Intersection and Exit Location are the most critical 
physical properties, with respect to delay, atO'Hare. 
The preceding ATC discussion (Section 3.3.2) noted 
the required separations for arrivals and departures 
on an intersecting arrival and departure pair. It is 
evident from these rules that any intersecting config- 
uration with either (1) the intersection distant from 
the departure end (termed a "far" intersection), or 
(2) an intersection location such that wake turbulence 
on one runway frequently interrupts operations on the 
other, will experience considerably more delay than if 
the intersection were such as to eliminate this problem. 
Exhibit 3-12 illustrates point 1 above, showing the num- 
ber of departures which may be theoretically processed 
per hour on an intersecting arrival/departure runway 
pair, as a function of intersection location. 

Exit location determines how quickly an arriving air- 
craft can exit the active runway, allowing either another 
arrival or a departure on an intersecting runway. The 
delays currently experienced on many of O'Hare's con- 
figurations are significantly affected by both exit and 
intersection location as described below. 

Intersection location on the south half of the field is the 
major cause of delay for Configuration 1 (see Exhibit 
3-2) . Approximately 50 percent of the heavy arrivals 
on 32L touch down to the north of the intersection, thus 
creating a two minute wait (for wake vortex to dissipate) 
prior to the issuance of departure clearance to aircraft 
on 27L, Heavy jet departures on 27L also create wake 
turbulence problems for arrivals on 32L; however, this 
problem is alleviated by segregating heavy from non- 
heavy departures — in Configuration 1, all heavy jet de- 
partures normally use 32R. 

Intersection location also affects delays in Configura- 
tions 2 and 3 but in a manner different than in Config- 
uration 1 . On the south half of Configurations 2 and 3 
(which is identical in each) is a "far" intersection. 
ATC rules state that a departure on 27L must be through 
this intersection prior to the arrival of 14R crossing the 
threshold. In reality, this means that controllers gener- 
ally do not release a 27L departure if a 14R arrival is 
closer than two nautical miles from threshold. This is 
a "rule of thumb" which experience shows will allow 
adherence to the above rule. In effect, it implies less 



3- 31 



60 A 



50 



ec 

D 
O 

X 

AC 
UJ 

Q. 

Q 
UJ 
</> 
(0 
Ul 
O 

o 

JE 

Q. 

(0 
Ul 

EC 

2 

g 



40 



30 



20 



10 




RUNWAY INTERSECTION DISTANCE 



NEAR 



INTERMEDIATE 
22R 



FAR 



32 R 



027R 




14 L, 



9L- 



"N? 



O'Hare DelayTaskforce Study 
Chicago O'Hare International Airport 



ITITLC: 



CAPACITY IMPACT 
INTERSECTION LOCATION 



>SOUHCE " 

; Peat^MarJwick; 
Mitchell & Co. 



EXHNNT: 

3-12 



than a one-for-one operation on the south half of the 
field. That is, one departure may not be released be- 
tween each arrival pair. Thus, a reduction in capacity 
and increase in delay results. 

Note the existence of another "far" intersection on the 
north half of Configuration 3. However, even with two 
sets of intersecting runways, both "distant", Configu- 
ration 3 produces less delay in IFR weather than Con- 
figuration 2. This is because Runway 22R has no exits 
between the 14L/32R parallel taxiway and Runway 9L/ 
27R. In addition to ensuring that a departure from 9L 
is through the intersection (a "near" intersection) prior 
to the arrival crossing the threshold on 22R, the local 
controller must also ensure that arrivals to 22R are 
through the intersection prior to the release of 9L de- 
partures. The lack of exits on 22R forces increases 
in the runway occupancy time, delaying the release of 
departures on 9L and decreasing departure capacity. 
This, in turn, causes controllers to increase the normal 
arrival/arrival spacing on 22R by approximately one- 
haEf mile in order to minimize the occurrence of missed 
approaches. 

The lack of exits on Runway 14L increases delays ex- 
perienced in Configuration 3 for reasons similar to those 
noted above for Configuration 2. In particular, the lack 
of exits between the intersection of 14L with Runway 
18/36 and its intersection with Runway 9L/27R causes 
arrivals which cannot exit onto 18/36 to either stop 
short of 9L/27R or roll out past 9L/27R prior to releasing 
a 9L departure. 

Configuration 4 is the most efficient four-runway con- 
figuration in terms of delay, of the configurations in- 
vestigated by the taskforce. Departures on 32L are 
from taxiway Tl which yields essentially independent 
operations on the south side of the field. Although the 
north runways intersect, as in Configuration 1, the 
intersection distances are so short that arrivals and de- 
partures may be performed on essentially a one-for-one 
basis. 

The configuration is not without its problems, though, 
which are mainly centered on control functions. The 
difficulties in coordinating parallel 32 departures were 
noted in the discussion on obstructions. A similar 



3-33 



coordination difficulty exists for parallel 27 arrivals. 
In this arrival mode controllers are vectoring arrivals 
on either side of the localizers for 27R and 27L. The 
arriving aircraft are "turned on" to final with 1,000' 
altitude separation from 12.5 to 15 miles from runway 
threshold, depending on ceiling/visibility. These co- 
ordinating efforts are required for all configurations 
utilizing parallel arrival streams. 

Care must be exercised by the approach controllers not 
to allow a 27R arrival to "overshoot" its turn and pene- 
trate the airspace reserved for 27L approaches and vice 
versa. This additional care, which is not required in 
dual (non-parallel) approach configurations, places a 
greater workload on controllers. In addition, for ceiling/ 
visibility below 3500/5, two additional controllers are 
required to monitor the parallel approaches inside the 
outer marker. 

Besides airside problems with Configuration 4, two rel- 
atively minor groundside problems also exist. Depar- 
tures on 32L from T1 must taxi through the penalty box 
when departure queues exist, sometimes slowing the 
flow of ground traffic in this area of the field, particu- 
larly when the penalty box is in use. These same de- 
partures, under queue conditions, often back up onto 
the outer circular taxiway disrupting traffic flows. 



3.3.4 Meteorological Conditions Are a Major Cause of Delay at 

O'Hare. 



The operational strategy of the airfield is governed to a large 
extent by considerations of ceiling, visibility, precipitation and pre- 
vailing wind directions. These conditions determine not only what 
configuration will be in operation, but the control procedures to be 
used in processing aircraft to and from the field. Generally at O'Hare, 
the runway orientation is based upon 15 knot crosswind criteria with 
5 knot and 10 knot tail wind criteria for arrivals and departures re- 
spectively. Wind coverage of the existing runway system is excel- 
lent allowing use of multiple runway configurations under all but the 
most severe wind conditions. However, as was seen in Exhibit 3-7, 
average delay varies considerably by configuration, therefore, when 
the winds dictate the use of a high delay configuration, a premium, 
in terms of increased delay, is paid for its use. 



3-34 



Ceiling and visibility also affect the selection of operating con- 
figurations. While all of O'Hare's primary runways are equipped 
with instrumentation, the landing minimums vary from runway to 
runway, necessitating adjusting of the operating configuration to the 
prevailing ceiling and visibility conditions irrespective of the capac- 
ity of the runway combination. Meteorology also affects delays in 
even the most efficient configuration at O'Hare. For example, visual 
approaches (in which the pilot visually determines his own separation 
from the preceding aircraft) may not be conducted when the ceiling 
and visibility limits fall below 3,500 feet and 5 miles, respectively. 
This, in effect, causes an increased spacing between arrivals there- 
by decreasing capacity and increasing delay. As the ceiling and 
visibility approach IFR limits (1000/3), the spacing between arrivals 
again increases to allow a greater safety buffer between operations. 
In conditions of very low visibility, i.e., less than 500/1, visual 
observation of the runway system is not possible, requiring addition- 
al controller caution and increased dependence on pi lot/ controller 
communication, all of which further reduce the efficiency of the air- 
field system. 

The condition of the runways themselves can increase spacing 
(therefore increase delays) by reducing aircraft braking perform- 
ance thus increasing runway occupancy time. In addition, snow or 
ice on the runways will require periodic runway closures for main- 
tenance to ensure safe operating conditions. 

The passage of a frontal system through the Chicago area can be 
accompanied by turbulence severe enough to warrant the holding of 
departures on the ground and inbound aircraft in holding stacks. 
These conditions, although generally of short duration, often cause 
delays of major proportions due to the backlog of demand created. 
The impact of these interruptions is further discussed in a later sec- 
tion of this chapter. 



3.3.5 Operational Procedures Are a Contributor to O'Hare Delays 



The term "operational procedures" is meant to describe any pro- 
cedural decision by airport management or FAA which influences: 



The selection of operational configurations, 

The changing of configurations throughout the opera- 
tional day, or 

The availability of runways for operational use. 



3-35 



Several considerations enter into the first item above, most notably 
meteorology and controller preference (other considerations such as 
noise abatement are not addressed in this study) . While wind direc- 
tion and velocity are key determinants in the selection and changing 
of runway configurations, selection decisions remain the responsibil- 
ity of FAA air traffic control management (configurations have over- 
lapping wind coverages) . The selection of less efficient configura- 
tions can unnecessarily increase delays. 

Some configurations present control problems which increase the 
level of controller work effort. For instance, dual (non-parallel ar- 
rival runways) arrival configurations are favored in lieu of parallel 
arrival runway configurations because the latter require closer mon- 
itoring of the turns to final approach, thus increasing controller work- 
loads. While it is difficult to determine the extent to which such con- 
siderations affect configuration selection, the historic pattern of run- 
way use at the airport indicates that the configuration selection pro- 
cess does not yield greatest use of the configurations identified by 
the taskforce as most efficient from a delay standpoint. 

The changing of configurations throughout the operational day 
contributes to delay. Normally, the facility changes from a single 
arrival/departure runway configuration to dual or parallel arrival 
and departure runway configuration at 7AM and reverts back to a 
single arrival and departure configuration after 10PM. Such config- 
uration changes are used to adjust runway capacity to demand and 
create no delay problems. The O'Hare air traffic control tower op- 
erates under a policy which requires runway rotation every 8 hours 
for noise abatement purposes when wind and weather permits. Addi- 
tional configuration shifts are required when wind velocity and ceil- 
ing and visibility necessitate a change in arrival and/or departure 
runway orientation. The pattern of configuration shifts for the month 
of September, 1975, was examined in detail to determine the magni- 
tude and timing of runway changes. The September pattern, exclud- 
ing normal changes at 7AM and 10PM, was as follows: 



During September, there were 48 arrival and/or de- 
parture runway changes. 

The total number of changes throughout the month that 
occurred during a given hour of the day varied between 
a low of 2 and a high of 13 during the period between 
7AM and 10PM. 

The highest number (13) occurred in the hours 2-3PM 
and 3-4PM, just before and during the first hour of the 
quota period. ' 



3-36 



While no attempt was made to correlate these changes to wind and 
weather pattern or to identify the level of disruption, it would ap- 
pear from this limited analysis that a disproportionate number of 
configuration changes occurred during or near the beginning of the 
quota period when demand on the system is high and thereby esca- 
lated the delay levels. 

The unavailability of runways for use due to scheduled mainten- 
ance, construction, and weather related problems such as snow re- 
moval, also contributes to delay. To a large extent unavoidable 
weather related problems are the primary reason for "down" runways. 
However, scheduled maintenance and construction are a necessary and 
on-going function of the O'Hare operation which can contribute to de- 
lays. The scheduling of these functions should be at a time during 
which the need for the "down" runway or taxiway will be minimal . 
Airport management procedures have not always provided for detailed 
operational analyses prior to maintenance and construction schedul- 
ing, and coordination among aircraft and airport operators and the air 
traffic control management has not always occurred to the extent that 
the delay consequences of construction activities have been minimized. 



3.3.6 O'Hare Delays Are Directly Related to Aircraft Operating 

Demand and the Role of O'Hare as a Major Connecting Hub 



O'Hare International Airport processes more aircraft annually 
than any other airport in the world. The relationship between de- 
mand and the level of delay experienced at O'Hare is directly related 
to the absolute volume of aircraft operations and to the pattern of that 
demand. However, it should be understood that O'Hare serves as a 
major scheduled air transportation connecting complex (approximate- 
ly 50 percent of annual enpianements at O'Hare are transfers between 
aircraft) . Both the high volume and directional peaking character- 
istics of the scheduled air carrier demand at O'Hare are, to a great 
extent, due to the airport's connecting role. 

O'Hare is a natural connecting point, the Chicago area possessing 
both a high volume origin and destination city-pair market pattern 
and a geographic location directly in the path of primary east-west 
air carrier routes, and within short flying time of most communities in 
the heavily populated and industrialized central Great Lakes area of 
the nation. Thus, O'Hare provides convenient and frequent access 
to the entire domestic air transport network for many communities 
east and west of Chicago in an efficient, highly competitive manner. 
This connecting complex role manifests itself in a demand pattern 



3-37 



which tends to bunch arrivals and departures in blocks providing 
the capability to interchange connecting passengers in a high level 
of activity during the hours of the day which provide access to the 
west and east coasts of the nation with reasonable arrival and de- 
parture times. The existence of this connecting complex, which 
without doubt contributes to O'Hare delay levels, provides benefits 
to Chicago and the national system that are often misunderstood. 
These benefits include: 



An otherwise uneconomical level of service to many 
communities, large and small, is provided by means 
of through plane and connecting schedules. In ef- 
fect, because of O'Hare's ability to serve as a con- 
necting complex, hundreds of markets receive multi- 
ple daily scheduled flights with through or connecting 
plane service beyond Chicago when it would be diffi- 
cult for these markets to support even one daily sched- 
ule in each market on a direct flight basis. 



The Chicago traveling public enjoys a very high level 
of schedule frequencies which enhance the convenience 
of air travel to and from the area to the benefit of local 
business and pleasure travelers. 

Although delays occur at O'Hare due to the congestion 
created by the connecting complex air carrier schedules, 
a lower overall level of aircraft operations is required to 
carry passengers and cargo between many city-pair mar- 
kets in the national system of air transportation, undoubt- 
edly resulting in a measure of system-wide delay reduc- 
tion and energy conservation over what might otherwise 
occur . 



Exhibit 3-13 illustrates all of the above features of O'Hare's role 
as a major air carrier passenger interchange airport. Note that in 
the example shown the passenger loads represent approximately one- 
third local destination traffic, one-third intraline connections and one- 
third interline connections. It is the requirement to meet the minimum 
passenger connecting time that, in many cases, contributes to the vol- 
ume and directional peaking of air carrier aircraft movements at O'Hare. 

The taskforce evaluation focused upon the characteristics of de- 
mand that influence delay and the sensitivity of delay to changes in 
these characteristics. It should be noted that changes in the volume, 
composition or distribution of demand examined can impact upon the 
facility's ability to effectively serve the connecting complex role. 
Such effects were not examined by the taskforce. 



3-38 



^^^^^ Origin City 
^S. Departure 
^^^^^ Time 
Passenger ^^^^^ 
Destination >^ 


0730 


1030 


1500 


o 
o 

00 


Local Chicago Area 


31 


19 


43 


43 


Other Cities Intraiine: 
A 


8 


8 


7 


3 


B 


5 


1 


5 


4 


C 


2 


2 


3 


2 


D 


2 


3 


2 


1 


E 


1 





1 





F 


4 


3 


4 


2 


c 


1 


2 





8 


H 


2 


1 


1 





1 


1 





1 





J 


1 





1 





K 


1 


1 





3 


L 


1 








o 1 


Total Intraiine 


29 


21 


25 


23 1 


Other Cities - Interline 


32 


46 


38 


14 


Total 
Passengers 




92 


86 


106 


.0 



Note: 



Daily O'Hare connecting passengers from a typical community, August 1974. 



O'Harte' Delay Tasktorcef Study ,■■ 
Chicago O Hare International Airport 



IflTUE: 



DAILY CONNECTING 
PASSENGERS 

3-39 



Chicago Airlines 



£«£■ 



P. 



3.3.6.1 The Hourly Distribution of Current O'Hare Arrivals 

and Departures and the Mix of Aircraft Types In- 
fluence System Performance . 

As discussed in Sections 3.1 and 3.2 of this chapter, 
the hourly variations in aircraft mix and arrival /departure 
pattern affect airfield capacity and consequently delay, par- 
ticularly during the peak demand hours. Exhibit 3-14 de- 
picts a typical pattern of scheduled aircraft arrivals and de- 
partures at O'Hare. Evident is the high scheduled demand 
during the hours 7AM through 8PM. Both the level and con- 
tinuous nature of O'Hare demand contribute to delays. The 
arrival/departure ratio was examined for other delays con- 
sidering total operations; the ratio falls generally between 
45 percent to 55 percent. The fluctuation of this ratio, par- 
ticularly during peak quota hour periods, interacts with the 
hourly mix variations affecting capacity and delay. 

Exhibit 3-15 presents a summary of O'Hare daily (8AM- 
8PM) and quota hour operations from the September, 1975 
schedule used as the current baseline in the taskforce anal- 
ysis. From the exhibit, it can be seen that over 80 percent 
of the current O'Hare demand is in the large and heavy air- 
craft categories consisting of B-747, DC-10, B-727, DC-9, 
and other similar aircraft types. The category labeled as 
B-747 and DC-10 consists of aircraft with greater than 
300,000 pounds gross weight (heavy) which necessitate in- 
creased in-trail separation between following aircraft of all 
other categories due to wake turbulence. The categories 
labeled as Beech Bonanza, Baron, and King Air are repre- 
sentative of those aircraft weighing 12,500 pounds or less 
(small) which also necessitate increased in-trail separa- 
tion following either large or heavy aircraft. The inter- 
action between aircraft types with the current number of 
"heavies" and "smalls" at 15 percent and 13 percent of total 
demand respectively, reduces airfield capacity thus in- 
creasing delay. — 

The aircraft fleet mix, particularly the com- 
position of arriving and departing aircraft, 
varies by hour. 

The arrival/departure ratio changes dramat- 
ically by hour varying in the illustration from 
53 percent arrivals in the 4PM-5PM and 5PM- 
6PM hours to 44 percent arrivals in the 6PM- 
7PM period. Of course, the daily arrival/ 
departure relationship always approximates 
a 50/50 balance. Means to reduce the delay 
consequences of such demand variations are 
examined in Chapter 4. 



3-40 




I 

72 60 48 36 24 12 12 24 36 48 60 72 

NUMBER OF ARRIVALS NUMBER OF DEPARTURES 



O'Har© Delay Taskforce|StwcJv 
Chicago ?Q Hare International M.\rpor)t 



|title: scheduled operations 

BY HOUR 
FT 



Federal Aviation 
Administration 



314 



3-41 



TOTAL 

AIRCRAFT 

OPERATIONS 


11 

u ^- 

0.' >■ 
0. 00 

L. 
41 

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41 

E 


4 p.m 5 p.m Cessna 172. Beech Bonanza 

Beech Baron, King Air 
Convair 580, Crumman C-1 
B-727, DC-9 
B-747. DC-10 
Total 

5 p m 6 p.m. Cessna 172, Beech Bonanza 

Beech Baron, King Air 
Convair 580, Crumman C-1 
B-727, DC-9 
B-747, DC-10 
Total 

6 p.m. 7 p.m. Cessna 172, Beech Bonanza 

Beech Baron. King Air 
Convair 580, Crumman C-1 
B-727, DC-9 

B-747, DC 10 
Total 

8 a.m. -8 p.m. Cessna 172, Beech Bonanza 
(Total Daily Beech Baron, King Air 
Activity) Convair 580, Crumman C-1 

B-727, DC 9 

B-747, DC 10 

Total 



Hare Oelav Taskforce Stud-y 
Chicago O'Hare International Airport 



TITLE: 

BASELINE SCHEDULE 
DEMAND CHARACTERISTICS 



Landrum & Browni 

■■;■'.. ,*irpo?t:cqnsulta.iht'S'; 



iCXHIBIT: 

3-151 



3-42 



3.3.6.2 The High Level of Demand on the System, A Major 

Contributor to Current O'Hare Delays, Is Not Effec- 
tively Controlled By the 3PM to 8PM Quota Rule . 



O'Hare, like several other high-density traffic airports, 
operates under an FAA regulation restricting hourly IFR op- 
erations by user category. Subpart K of Part 93 of the Fed- 
eral Aviation Regulations, commonly referred to as the quota 
rule, is intended to restrict the volume of operations at O'Hare 
between the hours of 3PM to 8PM, local time, by reserving op- 
erational "slots" for the various users as follows: 



Scheduled Air Carrier 115 operations per hour 

Scheduled Air Taxis 10 operations per hour 

Other 10 operations per hour 



Any reservation allocated to but not taken by "sched- 
uled air carrier" operations is available for the "scheduled 
air taxi" operations. Any reservation allocated to but not 
taken by either of those user groups is available for "other" 
operations (general aviation and military). Additional IFR 
and VFR operations above the quota are allowed if a reser- 
vation is obtained from ATC. Additional reservations pres- 
ently are accommodated when the operation may be processed 
without significant additional delay. This significant delay 
level is not defined; however, present procedures allow ATC 
to accept additional VFR operations when the delay level is 
below 15 minutes per aircraft. Under the above noted cir- 
cumstances, it is possible for the activity of all user cate- 
gories to exceed their hourly allocation without violation of 
the quota rule. The current application of the rule to each 
user category is discussed in the paragraphs which follow: 



Scheduled Air Carrier - The air carriers mutually 
agree on the allocation of the 115 total quota hour 
slots. Having established the number of opera- 
tions by carrier, each is then free to schedule its 
operations at any time within the hour without re- 
gard to schedules of other carriers. Arrivals and 
departures are only restricted by the total number 
of operations that the carrier has allotted within 
each quota hour. All passenger and cargo opera- 



i 



3-43 



SCHEDULED OPERATIONS PER HOUR a 








Total 












Air Carrier 






Time 


Air Carrier 


Air Taxi 


and Air Taxi 






3: 00-4: 00 


103 


10 


113 






4:00-5:00 


113 


9 


122 






5: 00-6: 00 


111 


11* 


122 






6:00-7:00 


113 


12* 


125 






7: 00-8: 00 


109 


11* 


120 






ACTUAL OPERATIONS PER HOUR ♦ 








Total 




Total 


Time 


Air Carrier 


Air Taxi 


Scheduled 


Other 


Airport 


3:00-4:00 


104 


9 


113 


11* 


124 


4:00-5:00 


108 


11* 


119 


12* 


131 


5:00-6:00 


118* 


11* 


129* 


11* 


140* 


6: 00-7: 00 


121* 


11* 


132* 


8 


140* 


7: 00-8: 00 


104 


10 


114 


7 


121 



Above Quota 



A Scheduled aircraft gate arrivals and departures based on 
Official Airline Guide - September 19, 1975. 

♦ Actual aircraft operations performed on average weekday 
in September, 1975 based on tower records of aircraft 
landing and takeoff times. 



O'Hare Delay Taskforce Study 
Chicago 0*Hare International ^irport 



title: SCHEDULED VS ACTUAL 
OPERATIONS - SEPT. 1975 



Land rum A -Brown 

'■■ ' klRPO«.T CONSULTANTS-; 



16 



3-44 



tions of domestic, international and supplemental 
air carrier operators, with the exception of charter 
extra sections, training, reposition and test flights, 
are subject to the quota rule. The exempt carrier 
operations are only a small percentage of today's 
total demand. 

Examination of air carrier operations scheduled 
for the month of September, as shown in Exhibit 
3-16, indicates that operations were not scheduled 
in excess of the 115 quota hour allocation. Com- 
parison of the scheduled operations with average 
actual air carrier operations processed indicates 
that actual activity exceeded the quota level during 
2 of the 5 hours. It should be noted that the sched- 
uled operations figures are based on the aircraft 
arrival or departure at the gate, whereas the 
actual operations totals presented in the exhibit 
are recorded by ATC when the aircraft lands or de- 
parts. While not a pure comparison, the tabulation 
does demonstrate that operating patterns routinely 
place air carrier demand on the ATC system above 
the 115 operations provided for by the quota rule 
and scheduled in the airline guide. While these 
variations are in part attributable to early/late pat- 
tern of actual operations and adjustments for differ- 
ences between actual landing or take-off times and 
scheduled times, the airfield must accommodate 
these operations as they actually occur, not as they 
are scheduled. Current demand and delay patterns 
are such that air carrier operations peak in the 
hours between 5PM-7PM above the 115 operation 
quota level. 

Scheduled Air Taxi - Review of daily airport 
activity records indicates that air taxi operations 
currently are accounting for approximately 1.0 per- 
cent of total operations on a typical day. 

From Exhibit 3-16, it can be seen that air taxi 
schedules (as printed in the Official Airline Cuide) 
exceeded the allocated 10 slots during 3 of the 5 
quota hours; however, the combined total 125 sched- 
uled carrier and air taxi operations provided by the 



3-45 



existing regulation was not exceeded. Actual air 
taxi operations processed by ATC are frequently 
higher than the quota level volumes due in part to 
early and lateness of actual operations. While these 
aircraft operations can to some extent be accommo- 
dated on non-interfering runways during VFR oper- 
ating conditions, they add to the overall system con- 
gestion during SFR weather and periods of high 
wind which limit runway use. 

Other - The "other" category of activity consists 
of general aviation, non-scheduled air taxi, sup- 
plemental, and military operations. There is no 
procedure for allocating "other" slots, except for 
issuing reservations on a first-come basis. There 
has not been a major problem with military activ- 
ity in the past and no increase in military activity 
is anticipated to occur. All general aviation op- 
erations are accommodated by current policy, if 
possible. 

There is frequently "other" demand for slots above 
the 10 allowed by the quota rule. There is an at- 
tempt by ATC to handle this demand by accepting 
VFR operations whenever weather conditions per- 
mit and delay is below 15 minutes. This proced- 
ure allows these aircraft to be handled with mini- 
mum impact on the system if they can be handled 
on non-interfering runways. However, under 
wind or weather conditions that limit runway use, 
these aircraft do impact other operations. 

There is no current procedure to monitor the num- 
ber of "other" reservations; thus IFR operations 
per hour frequently exceed the level allowed by the 
quota. Failure to monitor reservations and accept- 
ance of VFR operations by ATC contributes to opera- 
tions above the quota. From Exhibit 3-16, it can 
be seen that "other" operations in September aver- 
aged in excess of the quota level in 3 of the 5 quota 
hours. Actually, the impact of "other" activity 
is much greater than shown. Examination of the 



3-46 



daily use records that make up the September aver- 
ages shows many days with "other" operations sig- 
nificantly above the 10 allowed by the quota rule 
on days when the total 135 hourly allotment was 
exceeded . 



Sections 3.2.3 and 3.2.4 showed that delay increases 
rapidly as throughput approaches configuration capacity 
and that delays in the peak hours are significantly greater 
than average daily delays. Simply stated, any action that 
increases total busy hour demand on the system increases 
delay disporportionately. Subsequent sections will demon- 
strate the cost of operating at other demand levels. 



3.4 DELAYS DUE TO SHORT DURATION OPERATING ANOMALIES 



The level of delay experienced at O'Hare is critically sensitive to oper- 
ating anomalies of short duration which, in effect, alter the capacity of the 
system. Such anomalies include, but are not limited to: 



Weather related problems (frontal systems, fog, etc.) 

Navigational aid malfunctions 

Runway closures due to disabled aircraft (blown tires 
or other mechanical problems) 

Runway closures due to construction and maintenance 



Analysis of the effect of these problem days found that a reduction in 
the effective movement capacity at a busy airport, even for 30 minutes to one 
hour, during the peak demand periods can cause substantial backlog queues 
and lengthy delays to all flights over an extensive time period following the 
initial disruption. At O'Hare, such delays have increased the air carriers' 
total fuel consumption by over 200,000 gallons and added over $100,000 in 
direct operating costs in one day. The following paragraphs present a fur- 
ther examination of short-term disruptions. 



3-47 



3.4.1 Operating Abnormaiities Have Historically Disrupted O'Hare 

Operations at a Rate of 75 Days Annually . 



Examination of FAA NASCOM delay records for the years 1973, 
1974 and 1975 indicated that delays (only delays in excess of 30 
minutes are reported) were incurred on 100, 137 and 97 days, re- 
spectively. Of those delay days, 61 days in 1973, and 107 days or 
78 percent in 1974 had aircraft delayed in excess of 50 aircraft, 
while in 1975, 45 days or 46 percent exceeded 50 aircraft delayed 
and could be considered severe delay anomalies of some type. Air- 
craft reporting delays on these days ranged from 51 to 1, 124 and 
averaged approximately 150 per day. Averaging the experience of 
three years, 1973 through 1975, it is possible to conclude that anom- 
alies can be expected to disrupt the O'Hare system severely at the 
rate of approximately 75 days per year. 



3.4.2 Short-Term Operating Anomalies Can Increase Total Delay 

Per Operation by More Than 100 Percent . 



In order to examine these unusual patterns of demand, simulation 
experiments were designed to simulate conditions occurring on typi- 
cal severe delay days. In order to reflect these conditions and the 
resulting backlog, it was assumed that the airport was closed to all 
arrival and departure activity for a period of one-half hour from 1PM 
to 1: 30PM (allowing stacks and departure queues to build); a condi- 
tion not unlike that caused by the passage through the airport area 
of a frontal system. This test was conducted for relatively high ca- 
pacity VFR and IFR configurations, #1 (Experiment 41) and #3 (Ex- 
periment 64) respectively. The resulting average delay for each of 
these experiments is compared with the baseline delay in Exhibit 
3-17. 

From the experiments, it is apparent that O'Hare system perform- 
ance (in terms of delay) is indeed sensitive to short-term anomalies. 

Total delay sustained per aircraft increased by 109 percent in 
VFR conditions and by 78 percent in the IFR experiment as a direct 
consequence of one-half hour airport closure. By reference to Ex- 
hibit 3-1A, it can be determined that aircraft experiencing delays in 
excess of 30 minutes (the NASCOM standard) rose from zero to 110 in 
the VFR experiment and from 77 to 277 in IFR, an increase of 260 per- 
cent in IFR weather. In the IFR experiment, system throughput for 
the 12 hour simulation period was reduced 53 movements indicating 
a continuing backlog beyond 8PM due to a 1-1: 30PM closure. The 
backlog of aircraft experienced in the simulated IFR anomaly is 
graphically illustrated in Exhibit 3-18. 



3-48 



I- 
< 
o 



H 

m £ 



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5- 



DEPARTURE 



OPERATIONS 
Experiment 21 

CONFIGURATION 1 



ARR8V&L 



K JWERAGE 



DEPARTURE 





4' '4 



r T TT¥.Tl^ 



OPERATING CONDITIONS 
Experiment 41 

VFR 




NORMAL 
OPSIAT1GNS 



ANOMALC 
OPERATE CGNDTTIONS 



Experiment 26 Experiment 64 

CONFIGURATION 3 JFR 

A Airport closed from 1 - 1:30 pm to simulate demand backlog due to anomaly 



3 MareDfMav TaskfdTP 'SHjck 
Chicaqc^Q- Hare international AiVpcv 



mux: 



operating ueum 



3-17 



3-n 



~*— 



CONFIGURATION 3 
WEATHER 3* 
EXPERIMENT ©4 



200 — 




TIME OF DAY 



A ceiling/ visibility limits down to 
500 feet and 1 mile 



actual demand 



processed 

demand 



Hare Delay Taskforce Study 
Chicago O Hare International Alport 



iTTTkl: 



ANOMALOUS 
OPERATING BACKLOG 

3-50 



•Land r u m SB r ow n- 

.• A I P PC*) T, ','X'Ohl Sin :' A N T S A 



In both the VFR and IFR simulation experiments, this severe 
system performance deterioration is not unlike the average O'Hare 
experience. It should be noted that the arrival operations, to which 
delay is more costly, suffer the most rapid deterioration; inbound 
delays throughout the afternoon hours averaged 30 to 70 minutes per 
aircraft. Means to reduce the consequence of such abnormalities are 
examined in Chapter 4 of this report. 



3.4.3 Based Upon Past O'Hare Operating Practices, $8,300,000 In 

Annual Operating Cost Is Directly Attributable to Abnormal 
Operating Conditions. Including the Impact of Anomalous 
Conditions, Current O'Hare Airspace/Airfield Related Delays 
Total $44,200,000 Annually . 



Based upon the delay increases noted in Section 3.4.2 and assum- 
ing that these changes are representative of the impact on all oper- 
ating configurations, the annual impact of anomalous conditions was 
determined. For this analysis, it was assumed that anomalous con- 
ditions will be experienced at the average rate of 75 abnormal days 
annually, or at a rate of 20 percent annual occurrence to be distrib- 
uted equally over all configurations. The expected days per year in 
each operational configuration were divided into "normal" and "anom- 
alous" days. Hours of delay were then annualized using a method- 
ology similar to that discussed in Section 3.2.5. This annual delay 
estimate, 93,000 hours, represents an increase over delays sustained 
under normal conditions of 16,000 hours due to abnormal operating 
days. The dollar costs of current delay at O'Hare are approximately 
$44,200,000 annually when anomalous operating conditions are in- 
cluded. Thus short duration operating anomalies are conservatively 
estimated to add $8,300,000 annually to the $35,900,000 cost esti- 
mated for normal operating conditions. 



3.5 CURRENT LEVEL OF APRON/GATE SYSTEM DELAYS 



The apron/gate system considered in this study encompassed all the 
areas of aircraft movement interior to and including the outer circular taxi- 
way. The purpose of this section is to describe the current performance of 
that system in terms of gate utilization rates and delays incurred by aircraft 
operating in the apron/gate area. 



3-51 



As described in Chapter 2, the O'Hare Terminal features an extended 
finger concept which provides for aircraft gates lined up along concourses which 
extend outward from the terminal building. To determine the current level of 
use of O'Hare apron/gate facilities and the delay associated with operations in 
the system, the baseline schedule was used in conjunction with the GATESIM 
model (described in Appendix C) . The results of these experiments are dis- 
cussed in the paragraphs which follow. 



3.5.1 Both Individual Domestic Carrier Gate Frontage and Simuitan - 

eous Gate Utilization Are Approaching the Physical Limits of 
the Existing Apron/Gate Facilities . 



Two analyses were conducted to determine the current use pat- 
tern of the domestic gate complex. First the September, 1975 domes- 
tic schedule as published in the Official Airline Guide was used to 
develop scheduled gate frontage (the wing span of each scheduled 
aircraft plus nominal clearance of 25 feet) . Second, the detailed 
GATESIM simulation output was examined to determine the utilization 
of apron frontage on a processed basis giving consideration to the 
variability of aircraft on-time performance and system interactions. 
Exhibit 3-19 presents the results of this analysis for each of the do- 
mestic carriers at O'Hare in terms of the maximum gate frontage ver- 
sus the assigned facility allocations on both cumulative (sum of the 
individual carrier's peak frontage use regardless of times of occur- 
rence) and simultaneous (total peak complex frontage use at single 
time) basis. The international carriers were excluded from this 
analysis because of the unique nature of their requirements for gate 
positions in a relatively limited time period. The presentation also 
excludes charter and extra section activity of the domestic carriers. 

It can be seen from the data that the current domestic scheduled 
aircraft use of the gate frontage exceeds the available allocation by 
925 linear feet. The excess demand is accommodated in one of two 
ways: either by the use of gate sharing or by the use of double 
parking. The actual processed gate utilization statistics vary from 
the scheduled use pattern, a reflection of the early and late arrival 
performance of scheduled flights. In the case illustrated in the ex- 
hibit, the cumulative frontage requirement on a processed basis is 
less than that indicated in the schedule, exceeding available frontage 
by only 328 feet. 



3-52 



AIRLINE 


CURRENT 

GATE 

FRONTAGE 

ASSIGNMENTS 

(linear feet) 


SEPTEMBER 


1 SCHEDULE 


GATESIM PROCESSED USE 


PEAK 
SCHEDULED 

GATE 
FRONTAGE # 
(linear feet) 


TIME OF DAY 

OF PEAK 

SCHEDULED 

FRONTAGE NEED 


PEAK GATE 
FRONTAGE 
UTILIZATION* 
(linear feet) 


TIME OF DAY 

OF PEAK 

FRONTAGE 

UTILIZATION 




Continental 


380 


628 


18:05 


628 


18:00 


Northwest 


745 


1,010 


11: 35 


1,040 


11:40 


Braniff 


395 


391 


14:05 


261 


14:05 


Eastern 


785 


492 


10:45 


492 


10:45 


United 


3,298 


3,113 


12:25 


2,952 


18: 10 


Ozark 


320 


924 


14:55 


693 


I 
14-30 


TWA 


1,600 


1,649 


11: 15 


1,649 


11:10 


Air Canada 


160 


157 


12:05 


157 


12:00 


North Central 


630 


808 


7:55 


693 


16:00 


Delta 


830 


1,022 


17:05 


1,022 


17:10 


American/ 
Southern 


2,195 


1,963 


12:35 


2,003 


j 
12: 30 


Allegheny 


165 


231 


8:55 


231 


9:25 


Cumulative 
Domestic Apron 
Frontage 


11,493 


12,418 


— 


11,821 




Simultaneous 
Total Domestic 
Apron Frontage 


11,493 


10,292 


17:45 


- 


■; 




lease of Ameri< 
aircraft wing 
te facilities 


:an gate. 

span plus 25 foot 


wing tip clearanc 




* Southern sub 

• Dimension of 
occupying ga 


:e for all aircraft 





O'Hare Delay TasktorcefStudy ft 
Chicago O'Hare International Airport 



title CURRENT DOMESTIC 



SBM^gZHL 



Landrum 4 Brown" 

. ;' 4I.BPOP.T CONSULTANTS 



JCXMBfT: 

3-191 



3-53 



Also defined in Exhibit 3-19 is the maximum simultaneous use of 
the total domestic gate complex on a scheduled basis. Based on Sep- 
tember 1975 schedule, a peak simultaneous apron frontage of 10,292 
linear feet occurs in the 5PM to 6PM hour. Simultaneous frontage 
utilization was not computed on a processed basis. On either a sched- 
uled or processed basis, the cumulative individual carrier frontage 
requirements and the simultaneous gate need are approaching the 
physical limits of the existing apron/gate facilities. 



3.5.2 Current Delays in the Apron/Gate Complex Average from 1.4 

to 1.7 Minutes per Aircraft Under VFR and IFR Conditions 
Respectively . 



Exhibit 3-20 presents the results of the GATESIM analysis of cur- 
rent apron/gate system operations. Examination of the data yields 
the following information with regard to current performance. Ex- 
periments G-1 and G-2 depict system performance with clockwise and 
counterclockwise movement, respectively, on the outer circular taxi- 
way system in average VFR weather conditions. Opera tfng~fn~ei ther^ 
mode, the average delay per aircraft is approximately 1.5 minutes. 

Of this delay, approximately 0.7 minutes is incurred maneuvering ) 

inbound while only 0.5 minutes occur maneuvering outbound. These 
results reflect the current operational procedure of giving departures 
priority to maneuver from the system. Additionally, an aircraft has 
about a 4 percent chance of entering a penalty box. For aircraft di- 
verted to the penalty box, the average duration of stay is between 
8.4 and 9.5 minutes in VFR conditions. 



L 



Experiment G-3 depicts the deterioration of system performance 
which occurs during IFR weather similar to condition 3. The change 
in demand pattern (more aircraft arriving late) coupled with connec- 
tion problems to accommodate the late arrivals, increases gate related 
delay. Gate availability delay accounts for 40 percent of the total de- 
lay in IFR versus only 24 percent in VFR conditions. Additionally, 
an aircraft has a 6.3 percent chance of spending time in the penalty 
box. Average time spent in the penalty box also increases from 8.4 
to 10.9 minutes. It should be noted that a severe distortion of the 
demand pattern can occur even under conditions of very good visi- 
bility in the airspace. One such anomaly would be the early arrival 
of eastbound traffic due to tailwinds and the late arrival of west- 
bound traffic due to the same wind condition. The more severe the 
demand distortion, the larger the resulting delay. 



3-54 



MEASURES 
OF 
EFFECTBVENSS 


EXPERIMENT 


G-1* 

Typical VFR 


G-2* 

Typical VFR 


G-3 

Typical IFR 


Gate 
Availability 
Delay 
(minutes) 


224 


220 


430 


Maneuvering 
Delay 
(minutes) 


746 


685 


640 


Total 
Apron/Gate 
Delay 
(minutes) 


970 


905 


1,070 


Average Delay 
per Aircraft 
(minutes) 


1.5 


1.4 


1.7 


Average 

Inbound 

Maneuvering 

Delay 
per Aircraft 
(minutes) 


0.8 


0.7 


0.7 


Average 

Outbound 

Maneuvering 

Delay 
per Aircraft 
(minutes) 


0.5 


0.5 


0.4 


TotaS Number 

of Aircraft in 

Penalty Box 


23 


26 


40 


Peak 
Penalty Box 
Occupancy 


4 


4 


4 


Average Time in 
Penalty Box 
(minutes) 


9.6 


8.4 


10.9 



▲ Clockwise movements on outer taxiway . 

9 Counter clockwise movements on outer taxiway 



O'HareiPelay Tasktorce Sftudy 
Chicago O'Hare International Airport 



,TLE GATESIM DATA- CURRENT 
SYSTEM PERFORMANCE 



L a nd r u rfi A B r ow h 

AIRPORT CONSULTANTS 



icxHwrr: 

3-2C 



3-55 



3.5.3 Current Q'Hare Apron/Gate System Delays Are Estimated to 

Exceed 6,900 Hours and Cost the Domestic Carriers Over 
$2,700,000 In Annual Aircraft Operating Costs . 

Having established the current pattern of delay at O'Hare under 
normal IFR and VFR operating conditions, the taskforce estimated the 
current annual cost incurred by aircraft operators assuming past 
patterns of weather occurrence. The analysis employed to derive 
the cost estimates involved annualization of the daily delay statistics 
using a rationale similar to that used in the airfield delay analysis. 
The cost of current delay (about 6,900 hours) is estimated to be 
approximately $2,700,000 annually. While such costs appear insig- 
nificant in light of the much larger airspace/airfield delay costs, if 
the aircraft fleet mix change projected for the pre- 1985 period occurs 
without facility expansion, the deterioration of the existing apron/ 
gate system performance will be rapid. The pre-1985 schedule (27 
percent heavy aircraft) indicates a need for 14,990 linear feet of cum- 
ulative domestic carrier gate frontage. 



3.5.4 Current Delays in the Apron/Gate System Are Primarily A 

Consequence of the Facility's Physical Limitations . 



In addition to the gate limitations discussed previously, the cur- 
rent delay in the apron/gate system is in large part a function of the 
physical characteristics of the facility. The cul-de-sacs between the 
concourses are relatively narrow by current standards, limiting gate 
ingress/egress to a single taxi lane for all but the smallest categories 
of aircraft (DC-9, B--727, etc.) Increasing numbers of larger, wide- 
bodied aircraft aggravate these dimensional restrictions causing de- 
lay. Clearances on the inner circular taxiway also restrict the oper- 
ation of B-747 aircraft necessitating additional maneuvering time. 

Gate facility limitations are reflected in the gate availability de- 
lays depicted in Exhibit 3-20. Arrivals sustaining such a gate re- 
lated hold in excess of several minutes are sent to an inbound holding 
apron adjacent to the D and E concourses known as the "penalty box". 
This facility has capacity to accommodate approximately two DC- 10/ 
B-747 or three B-727 aircraft. When the demand requires, departure 
aprons adjacent to Runways 32R and 32L are utilized. As indicated 
in the exhibit, the maximum penalty box occupancy observed in the 
three simulation experiments was four aircraft. This maximum value 
was observed at six separate times in the 15 days simulated in the ex- 
periment. On four of those occasions, occurring in both the morning 
and evening peak periods, the aircraft holding were as follows: 
B-747, DC-10, B-727-200, and B-737. This mix of inbound holding 
aircraft exceeds the capacity of the existing inbound hold apron. 
Operational difficulties associated with the current penalty box loca- 
tion are discussed further in Chapter 4. 



3-56 



4. CURRENT DELAY REDUCTION OPTIONS 



The purpose of this chapter is to present the findings of all analyses em- 
ployed to determine the potential delay reduction benefits of alternate air traffic 
control (ATC) procedural, airport use policy, and facility development options 
in the current time period. Exhibit 4-1 presents a composite listing of these 
options as identified for O'Hare in initial taskforce efforts. 

The analyses and findings presented in this chapter are for the purpose 
of evaluating the benefits of those delay reduction options listed in Exhibit 4-1 
which appear to offer significant potential for immediate or near term delay re- 
duction in the Chicago O'Hare airspace/airfield system. A series of simulation 
experiments was conducted to determine the delay characteristics of each op- 
tion. Exhibit 4-2 presents the experiment design matrix in order to facilitate 
the identification of changes in baseline input assumptions used to accomplish 
each experiment. Exhibit 4-2A is a summary of the raw data generated by the 
AIRSIM model for each of these experiments. 

The method employed to assess the benefit of each option investigated 
was to measure the delay savings (in terms of time and direct aircraft operating 
cost) possible over baseline conditions as a result of the option. 

The potential direct aircraft operating cost savings derived from reduced 
delays are the primary economic justification for implementing delay reduction 
improvements, recognizing that any direct aircraft cost savings will be accom- 
panied by a corresponding reduction in inconvenience and cost to the traveling 
public. It should be emphasized that the potential cost savings as derived in 
this chapter are not necessarily cumulative; that is, each experiment represents 
the change of a single variable (such as demand level) and cannot in all cases be 
added to the savings of any other experiment to determine a total delay reduction 
benefit. Rather, the presentation provides means to assess the relative bene- 
fit in order of magnitude of one delay reduction option versus another. The 
options providing the highest incremental cost savings are thus clearly ident- 
ified. 

The current delay reduction alternatives examined fall into three broad 
categories: 



Air Traffic Control Procedural Options 
Airport Use Policy Options 
Airport Development Options 



Each of these subjects is addressed in the paragraphs which follow. 







AIRPORT DEVELOPMENT OPTIONS ATC PROCEDURAL OPTSONS 










1. A Utilize three arrival and departure 






1. 


Full utilization of 4R/22L. Remove 
4R displaced threshold and opera- 
tional restrictions. Install GS & 
MALSR. 


runway configurations 

2. A Reevaluate runway selection 
criteria 






2. 


Additional instrumentation 
9L GS and MALSR 
9R/27L RVR and centerline 
lights 

CAT III 14R 6 14L 
CAT II 32L, 27L, 9R, 6 32R 


3. A Modify procedures to increase 

utilization of independent runways 








AIRPORT USE POLICY OPTSONS 










3. 


A New turnoff 22R 


1. * Review system demand 






4. 


New turnoffs I4L, 32L, 32R 


Scheduling peak hour and 
inter-hour distribution 






5. 


Unrestricted use of Inner/Outer 
Taxiway system 


Volume of operations 
2. * Conduct major review of pre- 






6. 


Full utilization of runways 4L and 
9L takeoff s by B-747 


sent quota rule to consider: 

Effectiveness and need for re- 
vision to reflect increased per- 






7. 


A Holding apron improvements for 
arrivals and departures 


centage of heavy aircraft 
Quota extension to other hours 
Fractional hourly quota limitations 






8. 


Two additional connecting taxi- 
ways - 9R/27L 


Arrival/departure balancing quota 
3. A Improve planning and coordination 






9. 


Airport surface control, guid- 
ance and surveillance improve- 
ments 

ASDE-2 and 3 improvements 
Airport surface traffic control 
Taxiway lighting and low visi- 
bility guidance system 
Airfield lighting, signage and 
graphics 


of construction projects to minimize 
operational impact. 

Fully coordinate all construction 

projects 

Pre-plan operational means to 

minimize impact of construction 

projects 

4. Improve instrumentation at Midway to 
reduce interference with ORD 32L IFR 






10. 


A Future ATC system improvements 
Wake vortex prediction and 
avoidance impact on arrival 


operations. 




A Subject of in-depth taskforce quantitative evaluation. 


O'Hare Delay TaSkforce Studv! ; 


TITlf: INITIAL LISTING 


SOURCE :.;.■■■;'.: ,.;.' / . ; ..._;, 


JCXHHMT: 


Chicago O'Hare International Airport 


DELAY REDUCTION OPTIONS 


; Taskfdrce 


4-1 



4-2 



FUTURE GROUP 2 ATC 
EQUIPMENT AND RULES 





' O'Hare Delay Taskforce Study, v 
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-— * 





4.1 AIR TRAFFIC CONTROL PROCEDURAL OPTIONS 



Air Traffic Control (ATC) procedures are those exercised by the Federal 
Aviation Administration for the purpose of promoting the safe, orderly, and ex- 
peditious flow of air traffic within the Chicago airspace/airfield system. The 
procedural options which the taskforce chose to analyze, for the purpose of 
determining potential delay reduction, were the utilization of triple arrival 
and departure runways and runway selection criteria. The results of these 
analyses are presented below. 



4.1.1 The Use of Three Arrival Runway Configurations Can Be of 

Significant Aid in Processing Arrival Surges and with Manage 
ment of Departure Restrictions Offer High Potential for Major 
Delay Reductions . 



In Chapter 3, Section 3.2.3, the relationship of current capacity 
versus delay was examined for 14 O'Hare operating configurations. 
The relationship of quota period to daily delay was identified for both 
VFR and IFR operating conditions and it was found that the delay level 
was directly related to configuration capacity — high capacity configu- 
rations having low delay and vice versa. 

In Exhibit 3-9 in the previous chapter, two configurations were 
shown to produce a unique capacity/delay relationship having both 
high capacity and relatively high delay. The reason for this seem- 
ingly atypical performance lies in the inbalance of arrival /departure 
capability of these triple arrival runway configurations. At O'Hare, 
it is difficult to devise a three arrival runway configuration which 
does not limit departure capacity on one or both departure runways, 
a condition that results in a major increase in departure delay if main- 
tained during periods of high departure demand. 

Three arrival runways do provide a major increase in arrival 
capacity with attendant decrease in arrival delays and can deal more 
quickly with arrival surges than is possible with dual arrival run- 
way configurations. The triple arrival runway schemes — Configu- 
rations 7 and 13 — were simulated from 8AM to 8PM. Examination of 
the results indicates that, over short time periods (one or more 
hours) when either (1) an arrival surge must be processed, or (2) 
departure demand is below average, a triple arrival configuration 
can process significantly more arrivals than dual arrival runway con- 
figurations. This point is illustrated in Exhibit 4-3. Arrival capacity 
is dependent primarily on average in-trail air traffic separations, the 
number of runways simultaneously in use and the configuration of 



4-5 




■— «*• 



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(saniM'N) NOiivuvdas 

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O'Hare Delay Taskforce Study 
Chicago O'Hare International Airport 



^ARRIVAL RUNWAY CAPACITY 



VS SEPARATION 



United Airlines 



4-3 



4-6 



those runways. As can be seen in the example depicted in Exhibit 
4-3, two independent arrival runways can process approximately 
70 arrivals per hour, a rate that is increased significantly to approx- 
imately 102 arrivals by addition of a third arrival runway. 

Notwithstanding their departure limitations, three arrival run- 
way configurations offer high potential for relief from arrival con- 
gestion such as that sustained on severe delay days when a dual 
arrival runway pair has insufficient capacity to relieve a surge of 
inbound aircraft when operating in weather conditions better than 
3500/5 (experience indicates that lower minimums may be used) . 
The O'Hare tower is now utilizing several three arrival runway com- 
binations and it appears that the departure limitations can be miti- 
gated by judicious management of the arrival spacing on the third 
arrival runway during peak departure periods to expedite depar- 
ture processing. With such management, triple arrival runway con- 
figurations may become a very effective means to reduce O'Hare de- 
lay, having the greatest impact on arrivals where the cost of opera- 
tion is highest. 



4.1.2 The Use of Configuration 4 Which Minimizes Arrival/Departure 

Runway Dependency in Place of Configuration 1 Could Result 
In an Annual Savings of $1,400,000 Based Upon the Historic 
Runway Use Pattern . 



The significance of "independent" runways, in terms of selec- 
tion of configurations which minimize delay at O'Hare, is an impor- 
tant finding of the taskforce. Historically, the preferred configura- 
tion at O'Hare has been Configuration 1 (see Exhibit 3-6), involving 
the use of dual approach Runways 27R and 32L. However, Configu- 
ration 4 was investigated in detail with the AIRSIM model in order to 
determine the delay reduction benefits possible from the implementa- 
tion of a high capacity parallel landing runway configuration utilizing 
Runways 27L and 27R. The primary feature of this configuration is 
the virtual elimination of runway dependencies by utilizing the T1 
taxi way intersection for Runway 32L takeoffs. As can be seen from 
the data in Exhibit 4-2, the use of arrival/departure runways (which 
minimize dependence represented by Configuration 4) can provide 
approximately one minute average delay reduction per aircraft oper- 
ation over those levels of delay experienced during use of dual land- 
ing runways, represented by Configuration 1, in VFR weather. 



4-7 



A weather coverage analysis was conducted for the configura- 
tions investigated by the taskforce in order to determine the percent- 
age of time each configuration could be used under IFR and VFR con- 
ditions during the period from 8AM to 8PM. In this analysis, the max- 
imum allowable crosswind component was 15 knots for weather better 
than 200/i and 10 knots for weather 200/i or below. A 10 knot tail- 
wind was allowed for departures and a 5 knot tailwind for arrivals. 
Although Configuration 4 has historically been used slightly more 
than 1 percent annually, Exhibit 4-4 indicates that it is capable of 
providing 77.7 percent VFR wind coverage. It appears contradic- 
tory that this configuration should have such high capacity/low de- 
lay characteristics and such good wind coverage and yet be used so 
little. However, further investigation explained why Configuration 4 
has not been used a greater percentage of the time. 



Parallel 32 departures present special ATC coordina- 
tion problems, particularly during IFR due to the WCN 
radio tower to the west of O'Hare. (This problem is 
mitigated by Configuration 5 with the third departure 
runway as discussed in Section 4.1.3.) 

Parallel arrival configurations require special ATC co- 
ordination techniques which increase controller work- 
load (refer to Section 3.3.3). 

When in Configuration 4, 32L departures from T1 must 
taxi through the penalty box under queue conditions, 
rendering it unusable by arrivals. 

Departure queues from T1 on 32L often back up to the 
outer circular taxiway disrupting ground traffic flows. 



When the above difficulties are resolved, Configuration 4 and 
other similar high throughput, low delay configurations can be em- 
ployed more often, and delay savings will be realized. To estimate 
the magnitude of delay savings possible, it was assumed that Con- 
figuration 1 could be replaced by Configuration 4 (which, aside from 
controller workload and airfield layout problems, appears entirely 
feasible). From Exhibit 3-6, this would imply utilizing Configura- 
tion 4 during 28.3 percent of VFR weather replacing Configuration 1. 
The resulting expected annual cost saving using the annualization 
methodology described in Section 3.3 would be $1,400,000. 



4-8 



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4.1.3 Addition of the Third Departure Runway In Configuration 5 

Could Mitigate the Croundside Problems Associated with Con- 
figuration 4 Operations and Result in an Annual Cost Savings 
of $2,300,000. 



As noted in the previous section, delay reduction benefits are 
possible from use of configurations which minimize arrival/departure 
dependency such as Configuration 4 although several factors have in- 
hibited its use historically. The addition to Configuration 4 of a third 
departure runway as in Configuration 5 to a large degree mitigates the 
effect of groundside and departure coordination problems. The lifting 
of restrictions on Runway 4R-22L in the summer of 1975 makes the use 
of the third runway in Configuration 5 possible. 

The layout of O 'Hare's runways permits the use of three depar- 
ture runways in several configurations including number 5 in which 
departure capacity is gained but not at the expense of arrival capac- 
ity and delay. Configuration 5 was simulated and the results (refer 
to Exhibit 4-2) indicate it to have the highest throughput and lowest 
average delay per operation of any configuration investigated by the 
taskforce. These results are because the south half of the configura- 
tion consists of essentially independent runways (departures on 22L 
and 32L from T1) and the intersection distances on the north half are 
short enough to allow at least a one-for-one operation with respect to 
arrivals and departures. Configuration 5 provides approximately a 
two minute reduction over the level of average delay experienced 
during use of dual landing runways, represented in Configuration 1, 
in VFR weather. The delay savings potential, as shown in Exhibit 
4-5, amounts to approximately $19,000 for each day (8AM-8PM) Con- 
figuration 5 is used to replace Configuration 1 and approximately 
$7,000 for each day it replaces Configuration 4. Based upon the his- 
toric use pattern, replacement of Configuration 1 by Configuration 5 
could result in an annual savings of $2,300,000. This $900,000 
greater savings than that achieved by replacement of Configuration 1 
with Configuration 4 is directly attributable to the use of a third de- 
parture runway. Examination of the wind coverage in Exhibit 4-4 
indicates that Configuration 5 can be utilized during 75. 7 percent of 
VFR weather, a coverage only 2 percent less than that provided by 
Configuration 4. Given its similar wind coverage, reduced control 
problems and higher level of delay savings, Configuration 5 is oper- 
ationally superior to either Configuration 1 or Configuration 4. 



4-10 





AIRCRAFT 
ARRIVALS 


AIRCRAFT 
DEPARTURES 


TOTAL 
OPERATIONS 


TOTAL DAILY DELAY* (Minutes) 








Configuration 1 
Configuration 4 
Configuration 5 


2,704 
2,584 
2,452 


4,112 
2,271 
1,371 


6,816 
4,855 
3,823 


DAILY DELAY SAVINGS* (Minutes) 








Configuration 5 versus 1 
Configuration 5 versus 4 


252 
132 


2,741 
900 


2,993 
1,032 


DAILY COST SAVINGS* (Dollars) 






■ 


Configuration 5 versus 1 
Configuration 5 versus 4. 


$2,389 
$1,251 


$16,309 
$ 5,355 


$18,698 
$ 6,606 



A 8am to 8pm. 

♦ Weighted fleet operating cost per minute of $9.48 airborne 
and $5.98 ground. 



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4.1.4 Selection of the Most Efficient Runway Configurations Could 

Result in an 8 Percent Increase in O'Hare's Current Effective 
Capacity rw/^) From 141 to 151 Operations Per Hour. O'Hare's 
Weighted VFR and IFR Capacities mma* Could be Increased to 
155 and 130 Respectively through Implementation of an Im- 
proved Configuration Selection Process . 



In Chapter 3, Section 3.1.4, a current weighted average hourly 
capacity was established based upon the historic usage (Exhibit 3-6) 
of O'Hare's runway configurations. The results of that analysis indi- 
cated that O'Hare is currently operated at an average Capacity m/A) 
of 141 operations per hour and that the average VFR and IFR Capac- 
ities (WA) were I 43 and 126 respectively. On the basis of the findings 
in Sections 4.1.1 through 4.1.3, the taskforce wished to examine the 
degree to which O'Hare capacity is limited by the operational config- 
urations selected. 

To conduct this analysis, all current Baseline configurations 
were first rank ordered according to total delay per operation. Ex- 
hibit 4-6 depicts the rank ordering of the Baseline configurations by 
VFR and IFR weather categories. By comparing the rank ordering 
in Exhibit 4-6 with historic usage (Exhibit 3-6), it can be seen that 
considerations other than capacity and delay have resulted in far 
less than optimum use of available runway configurations from an 
efficiency standpoint. Notably, the 5 high capacity/low delay con- 
figurations in the exhibit have historically been operated in total 
only 5.2 percent of the year. This limited prior use of these config- 
urations is mainly attributable to factors such as the airfield restric- 
tions on 22L departures and 4R arrivals and noise abatement consid- 
erations, but it also points out the level of understanding in the 
aviation community of the relationship between capacity and delay 
stemming from the limited nature of the quantitative techniques pre- 
viously available to assess the performance of the system meaning- 
fully. 

With knowledge of configuration capacity /delay and wind/ 
weather coverage data presented in Exhibit 4-4, a runway use pat- 
tern making use of O'Hare's most efficient configurations identified 
by the taskforce was developed. This revised pattern of use, pre- 
sented in Exhibit 4-7, reflects assignment of the bulk of operating 
hours where possible to the most efficient configurations. The re- 
sulting revised pattern is similar in form to the historic pattern, 
recognizing the need to spread the impact of noise equitably among 
all populated areas surrounding the airport and providing coverage 
of all wind and weather conditions affecting the operation. This de- 
lay optimized pattern appears achievable within the constraints cur- 



4-12 





CONFIGURATION 


EXPERIMENT 
NUMBER 


TOTAL DELAY 
PER OPERATION 

(Minutes) 


AVERAGE 
HOURLY 
CAPACITY (§T 
(Operations) 


RANK 
ORDER 

BY 
DELAY 




5 


30 


2.4 


160 


1 




17 


38 


2.9 


156 


2 




4 


27 


3.1 


156 


3 




15 
13 


100 
95 


3.4 
4.2 


154 
172 © 


4 
5 




1 


21 


4.4 


148 


6 


VFR* 


11 
3 


71 
69 


4.5 
4.8 


147 
145 


7 
8 




8 


35 


5.3 


NA 


9 




6 


70 


6.0 


143 


10 




2 

7 


23 
33 


7.3 
8.0 


138 
154* 


11 
12 




14 


72 


9.2 


136 


13 




18 


74 


9.6 


135 


14 




5 


32 


5.9 


146 


— — — — — 
1 




4 


29 


6.9 


143 


2 


IFR + 


3 
8 


26 

37 


9.6 
10.2 


133 
135 


3 
4 




2 


25 


16.5 


NA 


5 




14 A 


73 


16.8 


125 


6 



* 



As noted in Exhibit 3-6, this configuration is typical of IFR configuration 
performance: parallel arrivals/mixed departures used in ceiling and 
visibility conditions below 500/1. When operated in these low ceiling 
and visibility conditions, its capacity decreases to 110. 

Greater than 1000/3. 

■ 
Less than 1000/3. 

Capacity reflects a 60-40 arrival/departure ratio. 



OHarfe Delay Taskforcfe Study j;| 
Chicago 4>' Hare International Airport 



T,T " CONFIGURATION RANK 
ORDER BY AVERAGE DELAY 



>L a n.arij m & B r own' 



4-6 



4-13 



CONFIGURATION 


TASKFORCE 
CONFIGURATION 
NUMBER 


WEATHER CONDITION 


TOTAL USE* 


VFR 

GREATER 

THAN 1000/3 


IFR 

LESS 

THAN 1000/3 


"^ 


5 


28.1% 


6.2% 


34.3% 




17 


21.2% 


- 


21.2% 


•V 


15 


14.4% 


- 


14.4% 




11 


12.7% 


- 


12.7% 


<x* 


13 


3.4% 


- 


3.4% 




1 


.8% 


- 


.8% 


S>. 


3 


.8% 


1.6% 


.8% 




14* 


3.4% 


6.6% 


10.0% 


\ry+ 


8 


- 


.8% 


.8% 


TOTAL 
OCCURANCE 


- 


84.8% 


15.2% 


100% 



Estimated based upon historic wind and weather data and configuration 
delay performance. 

Representative of typical IFR configuration performance-parallel 
arrivals/mixed departures used in ceiling and visibility conditions 
below 500/1 or in high wind velocity situations. 



O'Hare Delay Taskforce Study 
Chicago O'Hare International Air f port 



DELAY OPTIMIZED RUNWAY 
USE PATTERN 



Landrum & Brown 



4-14 



rently governing the configuration selection process, it is intended 
as an example of the benefits to be achieved through use of more ef- 
ficient runway configurations. Like results could be attained with 
other runway use patterns not analyzed incorporating greater utili- 
zation of triple arrival and departure schemes. Note that the re- 
vised pattern stresses neither an inordinantly high level of use of 
any one configuration nor maximized use of the configurations based 
on capacity considerations alone. 

Using the optimized runway use pattern, the weighted hourly 
Capacity (WA) was recomputed. The results of that analysis indi- 
cate that a considerable increase in capacity would be achieved. 
Average O'Hare hourly Capacity (WA) wou 'd be increased by 7 per- 
cent to 151 operations per hour. The weighted VFR Capacity (WA) 
would rise by 9 percent to 155 operations per hour, while IFR 
Capacity (WA) wou 'd be increased from 126 to 130 operations per 
hour, an improvement of approximately 3 percent. The effect on de- 
lay of such a capacity increase is discussed in a subsequent section 
of the report. 



4.1.5 Increased Operation of O'Hare's Most Efficient Runway Config- 

urations Could Reduce the Current Cost of Operations Under 
Normal Conditions From $11,300,000 to $16,300,000 or More 
Annually . 



Having established an efficiency related priority scheme of con- 
figuration selection in Section 4.1.1, the cost of annual delay was 
again computed assuming operr s Jons under the "Delay Optimized 
Runway Use Pattern" depicted in Exhibit 4-7. 

As noted in Section 4. 1.4, this delay optimized runway use pat- 
tern is similar in form to the historic one; yielding a similar degree 
of variation in configuration usage. This can be readily seen by com- 
paring the "Total Use" columns of Exhibits 3-6 and 4-7. Note that 
in each case, the total percentage of use of the top 5 configurations 
is approximately 85 percent of the time annually, with the individual 
contribution of each configuration to total annual use not significantly 
different for the top 4 configurations of each case. In effect, this re- 
vised pattern represents a substitution of efficient configurations for 
less efficient ones in the historic use pattern, i.e., Configuration 5 
for 1, Configuration 17 for 6, etc. While no evaluation of the noise 
impact of this delay optimized runway use pattern was undertaken 
by the taskforce, the pattern does maintain the latitude to rotate 
configurations periodically. Thus, the taskforce considered this 
runway use pattern to be easily implemen table. Using the method- 



4-15 



ology defined in Section 3.2.5 the cost of annual delay for this opti- 
mized use scheme was computed to be $24,600,000 annually. This 
represents a potential annual delay savings of $11,300,000 over the 
$35,900,000 cost of annual delays with the historic runway use pat- 
tern. 

In addition, the taskforce desired to know the amount by which 
the annual cost of delay at O'Hare could be reduced if the runway 
configurations were selected in order to fully minimize delay and 
maximize throughput. In this analysis, it was assumed that for 
every ceiling/visibility and wind velocity combination, the highest 
ranking configuration would always be used; in other words, the 
weather coverage (see Exhibit 4-4) was always assigned to the low- 
est delay configuration possible. This pattern of runway use would 
result in use of Configuration 5 for approximately 75 percent of the 
year and Configuration 17 for approximately 14 percent with the 
balance of use spread over other configurations in order to achieve 
full coverage of wind and weather conditions. 

It would be possible to develop such a pattern of configuration 
usage if delay were the sole determinant in the selection process and 
a single configuration could be operated for the bulk of the time. 
Such a fully minimized delay scheme has a delay savings potential 
of at least $16,300,000 annually, over the historic three runway 
use pattern. It should be emphasized that this minimized delay pat- 
tern was derived from the configurations analyzed and is not in- 
tended to represent an all-inclusive evaluation. Greater potential 
benefits are achievable through use of triple arrival runway config- 
urations during periods of high arrival demand. While considera- 
tions such as noise abatement may preclude the full realization of 
any delay minimized pattern of runway use, this finding does dem- 
onstrate the level of delay reduction benefit possible through im- 
proved runway configuration selection. 

Inasmuch as the environmental impact of the fully minimized de- 
lay runway use pattern was not assessed, the optimized delay pat- 
tern depicted in Exhibit 4-7 was selected for use in determining fu- 
ture demand/delay relationships. 



4.1.6 Failure To Optimize Fix and Runway Assignments (Load 

Balancing) Could Increase the Costs of Annual Delays by 
$3,000,000. 



Earlier studies conducted by the Chicago ARTCC and O'Hare 
TRACON have indicated a need for improved distribution (load bal- 
ancing) of aircraft arriving at the O'Hare terminal area airspace be- 



4-16 



tween the outer fixes. By referring back to Exhibits 2-3 and 2-4, 
it can be seen that the entire Chicago terminal airspace is divided 
into four quadrants, each served by at least one primary fix. His- 
torically, arrivals have been assigned outer fixes located in the 
quadrant containing the arrival's preferred routing. However, the 
quadrant supplying the most demand fluctuates each hour. This 
fluctuation has resulted in attempts by Chicago ARTCC to balance 
the traffic load, with emphasis on equalizing the demand placed on 
each O'Hare approach controller. 

The taskforce extended the above analysis, recognizing the in- 
teraction between arrival and departure runways and the need to bal- 
ance arrival and departure delay. The impact of fix and runway 
loading imbalance was analyzed by comparison of a baseline experi- 
ment (number 27) which reflected an equal balance of average daily 
arrival and departure delay between runways to an experiment (num- 
ber 77) with a 45 percent/ 55 percent average delay relationship be- 
tween runways. Exhibit 4-8 depicts the average hourly arrival and 
departure delays by runway resulting from the balanced and unbal- 
anced system performance. The pattern of delay by hour is notice- 
ably changed in the unbalanced case resulting in higher delay levels. 
Operations in an unbalanced state result in a 10 percent increase in 
average daily arrival delay and a 9 percent increase in average daily 
departure delay per operation processed. If such unbalance were ex- 
perienced throughout the year, the additional delay costs would a- 
mount to approximately $3,000,000. 

It should be stressed that the phrase "load balancing" implies an 
equalization of delay levels, not operating volumes. There is a sig- 
nificant difference in the meaning of equalization of delays and the 
equalization of operations. For example, in several frequently used 
configurations at O'Hare, the delay characteristics of the north side 
of the field are significantly different from those of the south side of 
the field. Even if the operational demand were equalized, the delay 
incurred on one half of the field would be much different from that 
incurred on the other half. Equalization of demand implies equali- 
zation of delays only when independent runways with similar geome- 
try are processing similar mixes of aircraft. 



4.2 AIRPORT USE POLICY OPTIONS 



The operational characteristics of Chicago O'Hare Internationa! Airport 
are determined, in part, by all those involved in managing and using the air- 
port. Therefore their decisions, or use policies, are extremely important to 
the future of not only O'Hare, but the entire National Airspace System, in which 



4-17 





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O'Hare Delay: Task force Study 
Chicago O'Hare International Airport 



imM: DELAY IMPACT OF 
RUNWAY LOAD BALANCING 



Landrum 6V Brown ; 

i'lBPORT,.CO<NSUtTANTS:; 



ISINIMT: 

4-8 



4-18 



O'Hare is so vital . The taskforce chose to examine those use policy options 
which, in its opinion, offered the greatest potential for delay reduction, recog- 
nizing the existence of problems associated with practical implementation of 
some options. The results of those examinations are discussed in the following 
sections. 



4.2.1 Modification of the Current Pattern of Demand at O'Hare By 

Adjustment and Enforcement of the Quota Hour Rule Could 
Reduce Delay . 



The taskforce examined the effect of the current pattern of de- 
mand on delay at O'Hare, with emphasis on quota rule adjustment 
of the schedule peaking and the relationship of aircraft arrivals 
and departures. Three aspects of quota hour delay reductions were 
examined: 



Adherence to the 135 movement level 
Establishment of an intra-hour quota 
Arrival balancing quota 



4.2.1.1 Limiting Total O'Hare Demand to 135 Hourly Move- 

ments by Adjustment and Effective Enforcement of 
the FAR Part 93 Quota Rule Could Reduce the Aver- 
age Delay Per Operation in VFR Conditions by 12 
Percent and by 17 Percent in IFR Weather. This 
Delay Reduction Offers a Potential Current Cost Sav- 
ings of $4,000,000 Annually . 



As noted in Chapter 3, enforcement of the existing quota 
rule at O'Hare has not been effective with operations regular- 
ly exceeding quota limits in both IFR and VFR conditions. In 
order to examine the potential benefits of strict adherence to 
the 135 limit, two experiments (75 and 19) were conducted 
with a modified September baseline schedule (hourly opera- 
tions in excess of 135 were deleted from 8AM to 8PM) . Con- 
figurations 5 and 3 were chosen as representative VFR and 
IFR conditions, respectively. This analysis was predicated 
upon the assumption that the current quota rule would be ex- 
tended and adjusted in order to preclude any activity in ex- 
cess of 135 during the 8AM to 8PM hours irrespective of 
weather conditions and that the limit would be strictly en- 
forced. 



4-19 



The results of experiments 75 and 19 are shown in Ex- 
hibit 4-2A. Total delay per aircraft in VFR conditions is de- 
creased by 0.3 minute from the baseline case in the highest 
capacity O'Hare configuration. In typical IFR conditions, 
total delay per aircraft operation drops by 1 .6 minutes from 
the baseline case. Assuming that these results, in terms 
of percentage delay reduction, would be typical of all IFR 
and VFR configurations, adherence to the 135 quota limit 
would offer a potential annual savings of $4,000,000. 

The discussion of the current distribution of daily de- 
mand by hour in Chapter 3 indicated that O'Hare operates 
at or near the quota level of 135 operations continuously in 
the period from 8AM to 8PM, in fact, a noticeable pattern of 
demand build-up occurs from 1-3PM prior to the quota peri- 
od. Since this build-up, if severe enough, effectively rep- 
resents a level of demand in excess of that allowed in the 
quota period, this delay savings could only be fully achieved 
by extension of the quota hours. 



4.2.1.2 Leveling (de-peaking) the Scheduled Arrivals and 

Departures Within the Hour by Establishment of an 
Intra-hour Quota Offers a Potential Current Delay 
Cost Savings of $5,000,000 Annually . 



Serious concerns have been expressed about the impact 
of airfield delays due to the peaking of scheduled air carrier 
arrivals and departures at major high-density airports. 
Even though the total number of scheduled arrivals and de- 
partures does not exceed the hourly movement quotas, sched- 
uled arrivals (and departures) tend to peak on the hour or 
half-hour, or at five-minute intervals, rounded for the cbn- 
venience of the traveling public. If the airfield capacity is 
1 to 1.5 arrivals per minute, it would appear that serious 
delays could be incurred when 8 arrivals are "scheduled" 
to arrive during a one-minute interval. 

In view of these concerns, this matter was thoroughly 
investigated by the taskforce. It was suggested that sched- 
ule depeaking could be achieved by reduction of the pres- 
ent hourly quota periods from 60 minutes to 30 minutes or 
even 15 minutes, with the respective movement quotas re- 



4-20 



duced to 50 percent or 25 percent of the present quota of 
135 per hour. Based upon this rationale, two new opera- 
tion schedules were derived from the January, 1975 base- 
line schedule (see Appendix A for a description of all sched- 
ules) and a series of simulation experiments (10, 12, and 
13) were performed for two different runway configurations 
and weather conditions. Raw data from these experiments 
are presented in Exhibit 4-2A and the results are compared 
graphically to baseline conditions in Exhibit 4-9. The re- 
sults indicate that the total delay per movement under normal 
operating conditions could be reduced by approximately one 
minute in VFR and one-half minute in IFR if the quota period 
were reduced to 30 minutes in length. This delay reduction 
would result in a yearly savings amounting to approximately 
$5,000,000. 

The use of a 15 minute period length, which would en- 
tail a severe restructuring of current schedule patterns, does 
not yield additional delay reduction in VFR conditions re- 
sulting in total delay identical to that achieved in the 30 min- 
ute case. No IFR experiment was conducted for the 15 minute 
quota period option since VFR results indicated that the in- 
cremental benefit did not warrant further evaluation. 

Total delay is not extremely sensitive to depeaking of 
the nominal "scheduled" arrivals because in real life, air- 
craft do not arrive exactly in accordance with their nomin- 
al scheduled times. Exhibit 4-10 shows the nominal num- 
ber of "scheduled" arrivals at ORD by minute during a peak 
arrival period from 1540 to 1700 for January, 1975. The 
following extreme peaks may be noted: 8 arrivals at 1559, 
6 arrivals at 1610, and 5 arrivals each at 1630 and 1659. 
It will also be noted that there are 32 minutes during this 
time when no arrivals are "scheduled". The solid curve 
of Exhibit 4-1 1 shows that actual random variation to sched- 
uled touchdown times (exclusive of arrival ATC delays) 
that was experienced by all 6,054 United Airlines flights 
during the good operating weather month of August, 1973. 
This curve shows that 5 percent of United's flights arrived 
6 minutes or more ahead of "schedule", 70 percent no more 
than 6 minutes late, 10 percent arrived 20 minutes or more 
late, and all flights arrived within 180 minutes. This ran- 
dom variation from actual scheduled times is caused primar- 
ily by upline departure delays and variations in the actual 
flight times due to winds, altitudes, and gross weights 
and is reasonably representative of the total system "on 



4-21 



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EXPERIMENT NUMBER 



O'Hare Delay Taskforce Study' 
Chicago O'Hare International Airport 



ITITLC: 



DELAY IMPACT OF 
INTRAHOUR QUOTA 



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ITITLE: 



SCHEDULE VS ACTUAL 
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4-23 



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IdTStrbution of variations! 

TO SCHEDULED ARRIVALS 



United Airlines 



H-2H 



time" performance. In order to simplify the analysis for 
illustrative purposes, the dashed line, consisting of 5 
straight-line segments, was used to approximate the actual 
experience curve. By application of the "lateness" distri- 
bution shown in Exhibit 4-11 to the scheduled arrival pat- 
tern, the expected actual number of arrivals by minute was 
manually derived. In Exhibit 4-10 the expected average 
number of actual arrivals by minute is superimposed on 
the nominal scheduled arrival pattern. In effect, the nomin- 
al scheduled peaking of up to 8 arrivals in any minute is 
substantially dampened by the lateness distribution from 
real life, resulting in actual fluctuations ranging from 1 to 
2 arrivals per minute. 

While a similar analysis was not undertaken for depar- 
tures, the results could be expected to have a similar 
though somewhat lesser effect. The peak dampening for 
departures would be lessened because aircraft never depart 
prior to scheduled time and late arriving aircraft can to 
some degree be turned around to meet scheduled departure 
times by expeditious ground handling. 



4.2.1.3 An Arrival/Departure Balancing Quota Could Reduce 

Delay Costs by $2,500,000 Per Year if Compliance 
by Users is Achieved. 



As may be observed at O'Hare, there is, during certain 
time periods, a preponderance of either arrivals or depar- 
tures. The effect of this inbalance between arrivals and de- 
partures if often an underutilization of the airport's arrival 
capacity concurrent with the overutilization of the airport's 
departure capacity, or vice versa. 

The taskforce investigated, with the aid of simulation 
Experiment 42, the effect on delay of an attempt to balance 
hourly arrivals with hourly departures. The results of 
Experiment 42 (shown in Exhibit 4-2), when compared to 
Baseline Experiment 21, indicate that a 12 percent savings 
on arrival delay per operation may be realized using Con- 
figuration 1. This 12 percent arrival delay reduction if 
assumed for all configurations, would amount to an approxi- 
mate savings of $2,500,000 annually. 

This savings would result only if user compliance is 
achieved. As noted in Chapter 3, it was determined during 



4-25 



taskforce investigations that the current quota rule enforce- 
ment is most effective in limiting scheduled air carrier ac- 
tivity levels. 

4.2.2 Reduction of the Current Volume of Operations at O'Hare Is 

One Means to Reduce Delay . 



In addition to the evaluation of the effect of the pattern of demand 
on system delays, the taskforce also examined the impact of absolute 
volume on delay. The relationship of delay to volume of aircraft pro- 
cessed is discussed in the sections which follow. 

4.2.2.1 If the Air Carrier Level of Demand on O'Hare Facil- 

ities Were Reduced by 10 Percent, an Annual Delay 
Savings of $10,000,000 Could be Realized. If Air 
Carrier Demand Were Increased by 10 Percent, the 
Current Annual Cost of Delay Could Increase by 
$19,000,000. 



The absolute volume of operations at O'Hare does con- 
tribute to delays. The degree to which absolute volume pro- 
cessed at O'Hare contributes to delay was illustrated by con- 
ducting simulation experiments to determine the level of de- 
lay increase or decrease to be expected corresponding to + 
10 percent hourly changes in air carrier volume. These + 
10 percent volume changes were achieved by adding/sub- 
tracting scheduled airline operations to/from the September 
Baseline schedule. The purpose of these experiments was 
to determine the sensitivity of delay to volume of demand 
under today's airfield and ATC system conditions, 

As discussed previously, the relationship between de- 
mand and delay is not linear but rather more exponential 
in form. Because the operational characteristics of each run- 
way configuration are different, the graph of demand ver- 
sus delay will differ for each configuration. If this relation- 
ship were determined and graphed through numerous 
simulation experiments for each major configuration in both 
VFR and IFR, a family of curves would be generated from 
which the annual delay savings or increases could be ap- 
proximated. Since this effort was beyond the scope of the 
taskforce resources, a lesser series of experiments was de- 
signed (Experiments 65, 66, 79, and 80) from which the 
effects of volume adjustments could be reasonably surmised. 



4-26 



Configurations 1 and 3 were chosen as representative 
current VFR and IFR configurations, respectively, and 
were simulated against the + 10 percent schedules described 
above. The results of Experiments 65, 66, 79, and 80 along 
with September Baseline Experiments 21 and 26 are shown 
in raw data form in Exhibit 4-2A and graphically in Exhibit 
4-12. As would be expected, delays in VFR were less 
affected by volume adjustments than those in IFR. For a 
10 percent reduction in air carrier demand, 25 percent and 
34 percent reductions in total delay per operation were real- 
ized over Baseline delays in VFR and IFR, respectively, 
amounting to a potential annual savings of $10,000,000. For 
a 10 percent increase in air carrier volume, 48 percent and 
65 percent increases in total delay per operation were real- 
ized in VFR and IFR, respectively, which would potentially 
increase the current cost of delay by $19,000,000 in normal 
operating conditions. 



4.2.2.2 A 10 Percent Reduction of Current O'Hare Demand 

Could be Achieved by Elimination of Nonscheduled 
General Aviation Activity, Resulting in a Potential 
Delay Savings of $10,000,000 Annually . 



From the analysis presented in Subsection 4.2.2.1, it 
is estimated that a 10 percent reduction in air carrier de- 
mand upon O'Hare facilities could yield delay cost savings 
of approximately $10,000,000 annually. One alternative for 
attaining this reduction would be the removal of nonsched- 
uled general aviation from O'Hare. To investigate the possi- 
ble delay savings for such a removal, the nonscheduled 
operations portion of the September Baseline schedule was 
stripped of general aviation operations. Operations deleted 
total 117 and were comprised of 14 percent of all twin en- 
gine operations greater than 12,500 pounds and 35 percent 
of all twin engine operations less than or equal to 12,500 
pounds. The resulting schedule was used to simulate op- 
erations in IFR weather employing Configuration 3. The 
results of the general aviation removal Experiment 68 (Ex- 
hibit 4-2A) are similar to those in Experiment 66 which rep- 
resented a 10 percent reduction of air carrier operations, 
indicating that the volume of reduction is more significant 
to delay savings than is the segment of demand removed. 
Experiment 68 was also compared to Experiment 26 (Base- 



4-27 



16 



14 



12 



(A 

3 

i 10 



s 8 

c 

i 

jjj 6 
Ul 

O 

2 

IU 

5 4 



Note: 



125 
(-10%A/C) 




135 145 

(baseline) (♦tO%A/C) 

QUOTA VOLUME (hourly operations) 



Based on September Baseline Schedule. 




~fp) Experiment Number 



Hare Delay Taskforce Studv 
Chicago O'Hare International Airport 



|Ttnfr , MPACT0F SCHEDULED 
tRRIER VOLUME VARIATIONS 



L a nd r u m & B ro w n- 

■ »lRPO«T CONS'Ut-TANTS 



4-28 



line) to estimate the delay cost savings during a 12 hour 
IFR period with no nonscheduled general aviation aircraft. 
This analysis parallels the degree of savings indicated in 
Subsection 1.2.2.1 and thus would closely approximate a 
10 percent reduction of scheduled air carrier demand. A 
similar benefit might be realized by development of inde- 
pendent general aviation runways which would separate 
this activity from the carrier aircraft utilizing the major 
runways. This concept will be examined in the master 
plan study. 



4.2.2.3 A 30 Percent Decrease of O'Hare Scheduled Air Carrier 

Activity During Peak Hours (21 Percent Reduction of 
Total Schedule) Offers a Potential Annual Delay Savings 
of $19,000,000 for Current O'Hare Operations . 



In the discussion of a 10 percent increase or decrease 
in air carrier demand (Section 4.2.2. 1), it was noted that 
aircraft delays are more sensitive to a small increase in traf- 
fic volume than they are to small decreases. In order to fur- 
ther explore the contribution of demand level to current de- 
lays, simulation experiments were conducted to determine 
the potential delay savings of a significant reduction in total 
operations, a reduction envisioned by the City in previous 
Midway Airport revitalization proposals. The resulting 
schedule reflects the removal of approximately 30 percent 
of total air carrier activity during the peak morning and 
afternoon periods, a 21 percent reduction of total air carrier 
demand in the 8AM to 8PM period. 

This reduced schedule was used to simulate the opera- 
tion of Configuration 3 during IFR conditions and Configu- 
ration 1 representing VFR conditions. The delays in Exper- 
iments 11 and 20 (shown in Exhibit 4-2A) were compared to 
Baseline Experiments 26 and 21, respectively. This com- 
parison showed that the arrival and departure delays were 
reduced; in the IFR case arrival delay was decreased by 70 
percent from 12.5 minutes average per aircraft operation to 
3.8 minutes, while departure delay was decreased by 57 per- 
cent from 6.7 minutes to 2.9 minutes per operation. 

It should be stressed that this brief analysis indicates 
a potential delay savings at O'Hare only. If this air carrier 
activity were transferred to Midway rather than removed 



4-29 



from the Chicago air traffic control area as assumed in these 
experiments, the net benefits would undoubtedly be reduced. 
The question of total system delay savings was not addressed 
by the taskforce which did not study the Midway operation. 
Because of the complexity and scope of the issue of Midway 
as a reliever, this subject will be analyzed in detail in the 
on-going master plan study and in other intensive studies 
with the air carriers. 



4.2.3 Attention to Phasing and Scheduling of Airfield Construction 

Programs Can Reduce the Number of Abnormal Operating 
Days Experienced at O'Hare Offering a Potential Cost Savings 
of $2,200,000 Annually . 



As discussed in the last chapter, the current levels of delay at 
O'Hare are highly sensitive to short term operating abnormalities re- 
sulting in some 15,000 hours of annual delay at a cost of $8,300,000. 
One necessary and unavoidable cause of such abnormalities is run- 
way closures for major maintenance and construction. Of the 75 
average annual abnormal (severe delay) days recorded historically 
by the NASCOM statistics, 20 days or 27 percent are associated 
with periods of construction. Considering the delay implications 
of such closures, and the fact that yearly runway maintenance clos- 
ures are almost unavoidable in the high density use situation at 
O'Hare, it is imperative that they be managed (scheduled) so as to 
produce the least disruption to normal airfield activities. To ensure 
that disruption of airfield activities is minimized, three strategies 
are possible. 



Given that certain portions of the airfield must be closed 
for various periods of time, historical demand and 
weather analyses should be conducted in order to deter- 
mine those hours and times of the year during which 
the need for the closed portion will be minimized. 

Simulation analyses should be employed to identify the 
most efficient (high capacity/low delay) alternative con- 
figurations to use during construction periods and to 
define the phasing of the major runway projects. 

Maintenance and construction activity should be coor- 
dinated between planners, managers, contractors, users 
and controllers. 



4-30 



The above strategies were employed at O'Hare during the summer 
months of 1975 when major overlays of Runways 9L/27R and 4L/22R 
were undertaken. As verified by NASCOM delay reports, the disrup- 
tion to system traffic during this period was minimal — an improvement 
from previous experience at O'Hare. This performance can be contin- 
ued by use of the foregoing strategy affecting a 27 percent reduction 
of abnormal operating days with their associated delay hours and costs. 
The potential current direct cost savings of such construction planning/ 
management is $2,200,000, the largest part of which was undoubtedly 
realized by the carriers in 1975 as a consequence of the construction 
planning/management program. 



4.3 AIRPORT DEVELOPMENT OPTIONS 



As noted in Chapter 1, Section 1.3, the O'Hare delay taskforce focused 
primarily on ATC procedural and airport use policy options, inasmuch as 
the City of Chicago is currently engaged in a Master Plan Study in which the 
need for and benefits from both short and long term airport facility development 
options will be determined. However, the potential benefits from two limited 
near term facility modifications were addressed: (1) addition of a new turnoff 
on Runway 22R, and (2) increased and/or relocated arrival hold aprons. 

Several additional airport development options listed in Exhibit 4-1 were 
accomplished in the 1975 airport construction program; these included full utili- 
zation of Runways 4I_ and 9L for takeoffs by B-747 aircraft, and removal of the 
displaced threshold and operational restrictions oh Runway 4R/22L. Since these 
items were programmed for implementation in 1975, the taskforce did not attempt 
to define their benefits quantitatively, however, they are discussed briefly in 
the paragraphs which follow, along with a discussion of the potential benefits of 
an angled exit on Runway 22R and relocated arrival hold aprons. 



4.3.1 A New Angled Exit on Runway 22R Would Reduce Arrival 

Delays in Configuration 2 by 6 Percent and Departure Delays 
by 29 Percent Resulting in a Savings of $750,000 Annually if 
the Historic Runway Usage Pattern is Maintained . 



In Section 3.3.3, it was stated that the lack of an exit on Runway 
22R between the 14L/32R parallel taxiway and Runway 9L/27R causes 
a noticeably higher delay in Configuration 2 than is experienced in 
other configurations examined. An ASRSIM experiment was thus devel- 
oped to determine the degree of delay reduction potential provided by 



4-31 



an angled exit for Runway 22R landings as shown in Exhibit 4-13. It 
was felt that this runway exit would serve to reduce the dependency 
of Runway 9L takeoffs upon Runway 22R landings by exiting a substan- 
tial number of 22R landings short of the intersection 9L. If these land- 
ings could be held short of 9L on this new angled runway exit, 9L de- 
partures would then be able to receive more expeditious takeoff clear- 
ance, thus reducing departure delays. In addition to a reduction in 
departure delays, it was also felt that airside delays to aircraft arriv- 
ing Runway 22R would be reduced as a result of a new angled exit on 
22R. These additional arrival delay savings would result because 
interarrival separations between aircraft approaching 22R could be 
reduced to normal separation standards. At present, normal separa- 
tions between arrivals are increased by approximately one-half 
nautical mile to allow for the dependency of 9L departures on 22R 
arrivals. 

By comparing the simulated operation of taskforce Configura- 
tion 2 with the proposed new 22R exit with the operation of Config- 
uration 2 as it currently exists (Experiments 3 and 4), it was de- 
termined that a reduction of approximately 6.2 percent over cur- 
rent levels of arrival delay and approximately 29.2 percent over 
current levels of departure delay are possible if the exit is con- 
structed . 

It should be noted that Experiments 3 and 4 were conducted a- 
gainst the January 1975 Baseline schedule and ATC rules in effect 
prior to November 15, 1975. The results of these experiments, 
shown in Exhibit 4-2A, are felt to adequately represent the benefit of 
a 22R angled exit under the new ATC separation rules. Employing 
the methodology discussed in Section 3.2.5, the cost of annual Con- 
figuration 2 delay was computed both with and without the turnoff. 
The delay reduction provided by the new 22R turnoff would yield 
an annual savings of approximately $750,000 if the historic 12 per- 
cent use of this runway continues in the future. Even if the con- 
figuration is used less frequently in the future, which appears un- 
likely, this improvement would appear cost effective. For instance, 
at 3 percent annual use the delay savings from the turnoff would 
cover its cost in 5 years. Similar benefit can be obtained from con- 
struction of a new turnoff on Runway 14L. 



4-32 




<fi> 



ADDED PAVEMENT 



O'Hare Delay Taskforcepiudy § 
Chicago O'Hare International Airport| 



4L/22R 
AWOLEP gQT 

4-33 



4 Brownl 



4 



4.3.2 Relocation of the Existing Arrival "Penalty Box" Would Facil 

itate the Use of Several High Capacity Configurations and 
Provide Additional Inbound Aircraft Hold Capacity . 



Current O'Hare terminal area arrival hold facilities (see Exhibit 
4-14) are limited to open apron, the "penalty box", adjacent to Con- 
courses D and E, and aprons adjacent to Runways 32R and 32L. While 
used for inbound aircraft holds, both Runway 32 aprons are provided 
primarily for departing aircraft and use of the 32L apron requires 
crossing Runway 9R-27L for terminal ingress/egress. The outer 
taxiway system is also utilized for inbound holds for short duration. 
Section 4. 1 clearly defined the benefits (potential cost savings on 
the order of $11,300,000 annually) which could be derived from oper- 
ation of high capacity/low delay Configurations 4 and 5. However, 
as noted, the Runway 32L T1 (see Exhibit 4-14 for location of Tl) de- 
partures in both of these high capacity configurations present ground 
traffic control problems for the air traffic controllers with associated 
workload implications. The operational factors impacting arrival 
holds in Configurations 4 and 5 include: 



Departure queue interference with outer taxiway oper - 
ations . Departure queues, when a queue exists, at the 
Tl intersection average 10 aircraft in the Number 4 con- 
figuration, the maximum queue length reaching 26 air- 
craft during the peak departure period. These queues 
are reduced to an average of 1 and a maximum of 8 with 
addition of a third departure runway in Configuration 5. 
In either case the queues are of sufficient length to inter- 
fere with outer taxiway operations. The third departure 
runway could be utilized to a greater degree to limit the 
32L queue at the Tl location, however, this is not de- 
sirable from a capacity /delay viewpoint. The maximum 
delay reduction benefit will be realized when the 32R 
independence is fully utilized (a condition which requires 
a limited queue) and when 22L departure demand is held 
to a level which does not interfere with 27L arrivals (22L 
departures interact with 27L arrivals) . 

Requirement to route aircraft through the "penalty 
box" . Under queue conditions, departures are routed 
through the "penalty box" effectively eliminating the 
inbound aircraft hold capacity in this area when Tl is 
in heavy use. 



4-34 



Utilization of the 32R apron is restricted . In Configu- 
rations 4 and 5, departures can be expected to queue on 
the bridge taxiway and adjacent to Runway 32R at T1, 
restricting access to the hold apron in this area. 

Utilization of the 32L hold apron requires crossing 
an active arrival runway . Runway 27L is an active 
arrival runway in Configurations 4 and 5. Utilization 
of the 32L hold apron requires twice crossing this run- 
way both in ingress to the apron and egress from the 
apron/gate system. Crossing of an active arrival run- 
way is undesirable for it increases air/ground traffic 
control communication, and can decrease arrival run- 
way capacity. 



The net effect of these operating factors is the virtual elimination of 
effective arrival ground hold capability when operating in Config- 
uration 4 and restriction of the full effectiveness of the three depart- 
ure runway operation of Configuration 5. 

The apron/gate system evaluation in Section 3.5 noted that the 
capacity of the existing arrival hold apron is not adequate to accommo- 
date the peak demand of four aircraft simultaneously sustaining gate 
related arrival holds on an average day. The excess demand is gen- 
erally accommodated at the departure aprons adjacent to Runways 32R 
and 32L or by unnecessary taxiing on the inner/outer circular taxi- 
way, neither of which are desirable. Examination of the existing 
penalty box location as depicted in Exhibit 4-14 indicates that expan- 
sion of the facility to provide additional hold capacity and to elimin- 
ate taxiway flow blockage is not possible for the following reasons: 



Expansion of the apron depth to accommodate wide-bodied 
aircraft without blocking the 14R/32L parallel taxiway 
is totally constrained by the proximity of the service 
roadway and outer circular taxiway. 

Increased capacity of the apron is constrained by the 
outer circular taxiway system and a primary entrance/ 
exit to the inner/outer taxiway system. 

The present location is reasonably well located to serve 
the Terminal 1 and 2 apron areas but is remote from the 
Terminal 3 apron area. Primarily because their use is 



4-35 





O'Hare Delay Taskforce Study' 
Chicago O'Hare International Airport 



TITLE 



TERMINAL AREA 
TAXIWAY SYSTEM 



3EXMMT: 



jL a n d r u m & B ro w n 

':■■ . ^IBf^OPT^ONSULTA^TS'' 



4-14 



4-36 



a function of gate occupancy problems, arrival hold 
aprons should relate directly to the inner/outer taxi way 
structure and apron/gate complex and not to the airfield 
taxiway structure. 



Solutions to the arrival hold problem should be developed to facilitate 
increased operations of high capacity /low delay Configurations 4 and 5 



4.3.3 The Construction in 1975 of Improved Shoulders on Runways 

4L/22R and 9L/27R has Removed Serious Runway Use Restric- 
tions. 



Until the completion of the 1975 construction program, Runways 
4L/22R and 9L/27R were unusable for takeoff by B-747 aircraft due 
to inadequate shoulders. While this restriction did not cause serious 
problems with today's fleet mix, it would have increasingly inhibited 
the ability to balance arrival and departure loadings (a contribution 
to delay) and unnecessarily increased controller workload. 



4.3.4 Unrestricted Use of 4R/22L Facilitates the Use of Three 

Arrival and Departure Runway Configurations . 



The removal in 1975 of the displaced threshold on Runway 4R 
and use restrictions on Runway 22L departures eliminated the only 
serious runway restrictions atO'Hare. With Runway 4R/22L avail- 
able to serve the entire aircraft fleet, the use of three arrival and 
departure runway configurations has noticeably increased. The de- 
lay reduction potential of three arrival and departure runways was 
described in Sections 4.1.1 and 4.1.2. The removal of these use 
restrictions was also a key contribution to the expeditious handling 
of air traffic during the overlaying of Runways 9L/27R and 4L/22R 
in the summer of 1975. 



4-37 



5. FUTURE DELAY REDUCTION OPTIONS 



The purpose of this chapter is to present the findings of analyses related 
to the second and third study objectives defining the future system performance 
including identification of the potential capacity increase and delay reduction 
benefits of proposed future air traffic control (ATC) improvements. The assess- 
ment of future O'Hare performance presented herein is predicated upon two basic 
scenarios judged by the taskforce to represent the most probable combinations of 
ATC system equipment and airline operations schedule forecast for the pre -1985 
and post- 1985 time periods. The primary emphasis of the taskforce effort was 
placed upon identification of the future operating environment through quantita- 
tive evaluation of the capacity increase and delay reduction potential of FAA en- 
gineering and development equipment proposals. The current physical config- 
uration of O'Hare airfield facilities forms the basis for the analyses presented in 
this section. 

Although every attempt has been made to predict future ATC environments 
accurately, all performance parameter predictions of the characteristics of the en- 
gineering and development elements were based on the best current judgment of 
those persons most heavily involved in their definition. The ATC equipment per- 
formance scenarios were drawn from the material in Appendix F. In some cases, 
extensive engineering and development will be required to demonstrate the achiev- 
ability of these performance characteristics. Consequently, the estimates of future 
capacity and delay presented are only as accurate as the input assumptions and the 
results of all analyses should be viewed as "best guess" estimates that may need to 
be updated as more finite data on system elements become available. It should also 
be recognized that the future system performance in either time period may be 
overstated to the degree that the assumptions regarding the timing of implementa- 
tion of each element are optimistically stated by those associated with the engineer- 
ing and development effort. Implementation timing is also subject to resource al- 
location and operational policy decisions largely uncontrollable by the engineering 
and development group. 

The potential operational effects on the O'Hare airspace/airfield system pro- 
vided by other applicable elements of the engineering and development program 
are also discussed in the last section of the chapter. 

i 
5.1 OVERVIEW OF THE FAA ENGINEERING AND DEVELOPMENT PROGRAM 



This section presents a brief overview of the engineering and development 
elements and their anticipated applicability at O'Hare. Appendix F of this report 
provides additional details of those elements. For a description of the full FAA 
engineering and development program, the reader is referred to "An Overview 
and Assessment of Plans and Programs for the Development of the Upgraded Third 
Generation Air Traffic Control System," March 1975.1/ 



1/ Federal Aviation Administration. "An Overview and Assessment of Plans 
and Programs for the Development of the Upgraded Third Generation Air 
Traffic Control System." FAA-EM-75-5 (The MITRE Corporation Report 
No. M73-237, Rev. 1), March 1975. 



Six proposed FAA engineering and development items have the poten- 
tial to affect future operations at O'Hare. These items are: 



Wake Vortex Advisory /Avoidance System (WVAS) 

Upgraded Automation - Including Metering and Spacing 

(M&S) and automation aids to the controller 

Discrete Address Beacon System (DABS) 

Airport Surface Traffic Control (ASTC) - Including Airport 

Surface Detection Equipment (ASDE) and Tower Automated 

Ground Surveillance (TAGS) 

Area Navigation (RNAV) 

Microwave Landing System (MLS) 



The paragraphs which follow provide a brief description of each of these 
elements. 



Wake Vortex Advisory /Avoidance System (WVAS) will pro- 
vide increased capacity by reducing aircraft separation stan- 
dards. The major objective of the FAA's wake turbulence 
program is to develop a ground-based predictive system 
which will allow for decreased longitudinal spacing between 
aircraft when trailing wake vortices do not present a hazard 
to following aircraft. Using the predictive data based on the 
life, decay and movement of vortices, and meteorological con- 
ditions, the approach controller can establish aircraft spac- 
ings 5-15 miles from the runway threshold which reflect the 
expected vortex transport and decay conditions in the runway 
approach corridor. Two stages of development are envi- 
sioned: 

Wake Advisory - initial system of ground wind sen- 
sors which transmit meteorological data to a central 
processing computer algorithm which assesses the 
vortex condition by runway approach area. Control- 
lers will be provided with a display defining the ap- 
plicable aircraft separation criteria for wake or no 
wake conditions. 

Wake Avoidance - advanced system utilizing a more 
complex vortex behavior predictive algorithm and air- 
craft spacing data would be provided directly to the 
ARTS III ATC equipment which when combined with 
metering and spacing would provide highly automated 
sequencing and metering of aircraft arrivals automati- 
cally. 



5-2 



Upgraded Air Traffic Control Automation, whose princ- 
ipal element is metering and spacing (M&S), will increase 
capacity by decreasing the delivery error of aircraft at the 
gate of the final approach in order to provide more precise 
aircraft spacing uniformly over time. This increased pre- 
cision will allow reduced buffers which are now required 
to ensure non- violation of the separation standards. Addi- 
tional automation aids to the controller, when fully devel- 
oped, will include computer controlled aircraft routing and 
sequencing decisions, digitized displays of aircraft separa- 
tions, transmission of aircraft control instruction to the 
pilot, computer generated alarms and WVAS information 
displays. 

Discrete Address Beacon System (DABS) is an improve- 
ment of today's air traffic control radar beacon system 
(ATCRBS) intended to reduce the surveillance error and 
provide a ground-air-ground data link with the capability 
of addressing each aircraft in a discrete manner. The 
data link will assist in reducing the voice communication 
workload of the controller and provide the means of auto- 
mating the transmission of routine messages between the 
aircraft and the ground. The data link will also interact 
with the M&S system in interchanging automated messages 
between discretely addressable aircraft and the ground 
control system. 

Airport Surface Traffic Control (ASTC) is primarily 
oriented toward aiding the ground controller with improved 
automated displays using surveillance data and digitized 
displays. The need for an automated improved airport sur- 
face traffic control becomes more important in bad visibility 
conditions. Two basic aids being developed are a new ground 
surveillance radar (ASDE-3) to provide improved definition 
of aircraft surface traffic to the ground controller and tower 
automated ground surveillance (TAGS) which will provide 
a plan view display of the airport with discrete aircraft 
identity labels. 

Area Navigation (RNAV) is a ground derived airborne nav- 
igation system which will provide equipped aircraft with the 
ability to navigate along any course to any destination or to 
any intermediate way point. RNAV will enable aircraft to fly 
from one designated way point to another within the terminal 
area with minimal instructions from the controller; eliminated 
will be the need to advise aircraft when and where to turn and 
change altitude. 



5-3 



Microwave Landing System (MLS) is intended as an ex- 
tension of the current instrument landing system capability 
which provides precise azimuth, elevation angle and range 
data over a wide coverage volume. Such data may be pro- 
vided as an input to automatic aircraft flight control sys- 
tems to facilitate automated approach and landing and will 
provide the capability to define multiple final approach 
paths including curved approach capability. 



5.2 DESCRIPTION OF FUTURE O'HARE OPERATING SCENARIOS 



For taskforce study purposes, as noted in Chapter 1, the capacity and 
delay statistics were computed for selected combinations of wake vortex 
avoidance and upgraded automation improvements which represent the most 
probable forecast of the ATC environment (assuming implementation at 
O'Hare) which will exist in the pre-1985 and post-1985 periods. The impact 
of the Wake Vortex Advisory /Avoidance System and Metering and Spacing 
elements were studied by the taskforce through identification of the capacity 
increase and delay decrease benefits achieved by reduced longitudinal sep- 
aration standards on final approach and the increased delivery accuracy. 

Airline operations schedules for the pre-1985 and post-1985 time per- 
iods were also required. Operations schedules were developed by the air- 
lines representing the most probable future aircraft fleet mixes for the pre- 
1985 and post-1985 time periods. The following subsections describe the 
ATC equipment and operations schedule assumptions for the two future per- 
iods under evaluation. 

5.2.1 Future ATC Equipment Improvements Can Be Grouped For 

Analysis By Expected Time of Availability and Basic Per- 
formance Characteristics. 



For purposes of planning and analysis, it is convenient to group 
future ATC equipment according to the expected time of availability. 
It should be recognized that there are inherent risks in any develop- 
ment program, and hence, the time of availability reflects the current 
best FAA estimates. Exhibit 5-1 shows the equipment groups for the 
future ATC environments together with the estimates of the develop- 
ment and the implementation dates of each. The optimistic, most likely, 
and the pessimistic dates are based on accelerated normal or deferred 
priority of budget, procurement and implementation cycles. For the 



S-H 



USl 



EQUIPMENT GROUP 



A 

DEVELOPMENT 



ESTIMATED IMPLEMENTATION 
YEAR J* 



OPTIMISTIC MOST LIKELY 



PESSIMISTIC 



1 


Wake Vortex Advisory System 


77 


79 


80 


82 


2 


Wake Vortex Advisory System 
Basic Metering and Spacing 


78 


80 


82 


85 


3 


Wake Vortex Avoidance System 
Basic Metering and Spacing ■ 
Improved Surveillance • 


79 


82 


85 


88 


4 


Wake Vortex Avoidance System 
Advanced Metering and Spacing 
Discrete Address Beacon System 


80 


84 


87 


90 



■ Basic (Initial Operating Capability) Metering and Spacing System 

A Current Best FAA Estimates (Based on the Availability of the 
latest item in each group) 

# Assumes to include automation aid to the controller (e.g., 
digitized display of separation measure, computer generated 
alarms, etc.) 



O'Harje Delay Tasktorce Study 
Chicago O'Hare Internal ip'na'l Airport 



I TITLE: 



FUTURE ATC 
EQUIPMENT GROUPS 



Appendix F 



Iexmwtt. 

5-1 



5-5 



taskforce analysis, Group 2 consisting of the wake vortex advisory 
system and basic (IOC) M&S capability was chosen to represent the 
pre-1985 period and Group 4, consisting of the more sophisticated 
wake avoidance system, improved surveillance, and advanced fully 
automated M&S, was chosen as most representative of the post- 1985 
ATC environment. The degree to which the other* elements of the FAA 
engineering and development program (MLS, RNAV and ASTC) are 
required to achieve the capacity and delay benefits offered by the 
Wake Vortex Avoidance and Metering and Spacing items is discussed 
in Section 5.6 of this chapter. 

The performance characteristics of the Group 2 and Group 4 equip- 
ment are identified in Exhibits 5-2 and 5-3. The VFR and IFR separa- 
tion standards for each of the groups, under both no vortex ("green 
light") and vortex ("fall back") conditions, as indicated by WVAS in- 
stallations, are shown in Exhibit 5-2. The minimum IFR standards 
are down to 2 nmi in Group 4 under "Green Light" conditions of WVAS. 
In Group 4, almost all the standards are 3 nmi or less with the excep- 
tion of a small aircraft following a heavy aircraft. The VFR "separation 
standards" are only analytic constructs to appropriately represent op- 
erations under VFR conditions in the modeling process, and hence, 
should not be considered regulatory in nature. Exhibit 5-3 shows 
the predicted departure rules, the M&S buffer, and the Wake Vortex 
System utilization rates for the Group 2 and Group 4 equipment. 



5.2.2 Basic Future O'Hare Operations Schedules Were Developed to 

Represent the Most Probable Pre-1985 and Post- 1985 Demand . 



Schedules were developed for the pre-1985 and post- 1985 periods. 
The base schedules were constructed to reflect the volume constraints 
of the current quota movement level of 135 operations per hour, con- 
sisting of 115 scheduled air carrier, 10 air taxi, and 10 general avi- 
ation "slots". This pattern of hourly demand was assumed constant 
for all hours in the 8AM to 8PM period under evaluation. Airline esti- 
mates of scheduled aircraft fleet mix by 15 minute periods were utilized 
to construct the simulation schedules, the pre-1985 period reflecting 
27 percent heavy aircraft and post-1985 45 percent heavies. Air taxi 
and general aviation fleet mixes were upgraded to reflect increased 
sophistication of the future fleet. 

In addition to the two base schedules, two alternative levels of 
scheduled air carrier demand were examined to provide insight in 
future scheduling strategies. These alternative schedules were pred- 
icated upon 105 and 125 hourly air carrier operations with fleet mix 
and air taxi/general aviation activity unchanged from the base sched- 
ule for each time period. 



5-6 



TODAY 
GROUP 2 FALLBACK 



TODAY 
GROUP 2 FALLBACK 



VFR 

(Separation Criteria in nautical m£B@$) 



LEAD^^ 


S 


L 


H 


s 


1.9 


1.9 


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2.7 


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4.5 


3.6 


2.7 



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1.9 


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H 


3.4 


2.7 


2.1 



GROUP 2 NO VORTEX 
GROUP 4 FALLBACK 



GROUP 4 NO VORTEX 



IFR 

(Separation Standards in nautical miles) 



\. TKAIl. 

LEAP\ 


S 


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• 


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3.7 


3.C 


2.3 



GROUP 2 NO VORTEX 
GROUP 4 FALLBACK 



Fallback: Condition prevailing 
when wake vortex is 
present in the approach 



GROUP 4 NO VORTEX 

S:Small 
L- Large 
H : Heavy 



O'Hare Delay Taskforce Study - 
Chicago O'Hare International Airport 



Trrts 



FUTURE ATC 
SEPARATION STANDARDS 



Apperjdix: F 



5-7 



OPERATIONAL 
PARAMETER 


CONDITION 


ATC EQUIPMENT 


GROUP-2 


GROUP-4 


SEPARATION BETWEEN 
DEPARTURES ON 
THE SAME RUNWAY • 
(Seconds) 


SAFE (GREEN LIGHT) 


60/60/90 


60/60/60 


FALL BACK - VORTEX 


60/90/120 
(TODAY) 


60/60/90 
(GROUP 2) 


SEPARATION BETWEEN 
AIRBORNE HEAVIES 
AND OTHER AIRCRAFT 
ARRIVALS AND/OR 
DEPARTURES AT A 
RUNWAY INTERSECTION 
(Seconds) 


SAFE (GREEN LIGHT) 


90 


60 


FALL BACK - VORTEX 


120 
(TODAY) 


90 
(GROUP 2) 


METERING AND 
SPACING 


ONE SIGMA INTER- 
ARRIVAL ERROR AT 
THE GATE (Seconds) 


11 


8 


NUMBER OF SIGMAS TO 
BE PROTECTED AGAINST 
(PROBABILITY OF 

VICLATION) 


2.33 (1%) 


2.33 (1%) 


V\AKE VORTEX SYSTEM 
UTILIZATION 
(percent of year) 


SAFE (GREEN LIGHT) 


A 

40% 


■ 
75% 


FALL BACK - VORTEX 


A 

60% 


■ 
25% 



DEPARTURE RULES 



All departures assumed to be conducted under IFR rule'- 
Any aircraft behind Small or Large/Heavy - Heavy Small or 
Large behind a Heavy. 



A WAKE VORTEX ADVISORY SYSTEN' 
■ tf/KE VORTEX AVOIT ANCE SYSTEM 



O'Hare Delay Taskforce Study 
Chicago O'Hare International Airport 



|Tm.«: 



FUTURE ATC 



OPERATIONAL PARAMETERS 



Appendix F 



JEXNOTIT: 

5-3 



5-8 



5.3 FUTURE AIRSPACE/AIRFIELD SYSTEM CAPACITY 



In determining future airspace/airfield system capacity, the primary 
taskforce objective was to identify the most probable future O'Hare operating 
region as a function of the runway configurations most commonly utilized at 
the airport. The estimates of future system capacity and delay are derived 
using the methodology employed in the evaluation of the current system de- 
scribed in Chapter 3. By their nature, the estimates of future systesrc per- 
formance are less precise than those for the current system for they are 
predicted upon availability and performance characteristics of equipment 
and procedures which are currently only in the early stages of planning 
and development. 

Two models were used in support of the findings of this chapter: 
the FAA Capacity Model and the City of Chicago AIRSIM model . Exhibit 
5-4 presents the experiment design matrix which is intended to facilitate 
identification of the input data used to conduct each model experiment and 
the results of the experiments pertinent to the analysis of future system 
performance. 



5.3.1 The FAA Capacity Model Was Employed To Identify The Future 

Capabilities of 42 Configuration, Weather and ATC Equipment 
Combinations. 



The capacity impacts of WVAS and Upgraded Automation were eval- 
uated using the equipment groups discussed previously. The results 
are presented in Exhibit 5-5. Each group was considered as an entity 
and no attempt was made to study each element individually. Such an 
analysis is appropriate due to the strong interrelationship of the ele- 
ments of a group. Capacity rp\ estimates for selected configurations 
for both IFR and VFR conditions were made using the FAA capacity 
model. Capacity (pj calculations were restricted to Croup 2 and Group 
4 together with their respective fall back positions. The capacity es- 
timates drawn from Appendix F, while developed with input assump- 
tions differing from those used in the evaluation of current capacity, 
are sufficient to show the trend of the future ATC equipment group 
performance. All estimates are based on 50 percent arrival/departure 
relationship, therefore, varying from the FAA model estimates of cur- 
rent system Capacity (pj presented in Chapter 3, Section 3.1.1 which 
were computed for a 53/47 percent arrival/departure relationship. 
The FAA model is presented in Appendix O and input data employed 
in arriving at these capacities are described in Appendices A and F. 



5-9 





ATC EQUIPMENT 
.SCHEDULES. ANC 


Ell 
Equ 
Rul 


ling A 

pmcn 


TC 


EXISTING ATC EQUIPMENT AND RULES 


FUTURE GROUP a ATC 
EOUPMENT AND RULES 


FUTURE GROUP 4 
ATC EQUIPMENT AND RULES 




\ SPECIAL 
\ CONDITIONS 

CONFIOURATIOnV 
AND WEATHER \ 
COMBINATIONS \ 

MODELED 


Nov IS, U7J 


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; O'Hare Delay Taskforce Study 
Chicago O'Hare International Airport 



EXPERIMENT DESIGN 
FUTURE DELAY REDUCTION 



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4 



O'Hare Delay Taskforce Study 
Chicago O'Hare International Airport 



ITITLE: 



FUTURE O'HARE 
HOURLY CAPACITY (F) 

5-12 



Appendix F 



lEXHMIT: 

5-5 



As noted In Chapter 3, the Capacities (pj determined by the FAA 
model are considered "point estimates", i.e., each Capacity ^pj is 
the result of very specific input regarding such variables as aircraft 
mix, and percent arrivals under conditions of continuous demand. 
The operations data used in all time frames were Identical with the 
exception of future separation standards (including departure rules), 
aircraft mix and M&S buffers. For analysis purposes, Croup 2 calcu- 
lations were based on the pre-1985 mix (27 percent heavy) and Group 
4 on the post- 1985 mix (45 percent heavy) . To better understand the 
effect of mix changes (increasing heavy aircraft) on capacity, esti- 
mates were also made of capacity with future mixes under today's 
ATC separation and procedures. 

For both IFR and VFR, a number of different configurations were 
selected so as to represent appropriately the range of capacities of 
the various runway configurations currently being operated at O'Hare. 
Specifically, Configurations 3, 4 and 16 were chosen to represent IFR 
operations and Configurations 4, 6 and 13 to represent VFR operations. 
The results of Croup 2 and Group 4 analysis are presented in Exhibit 
5-4A. As expected, the capacity benefits of the ATC improvements vary 
considerably by configuration. For example, the Group 2 benefits 
range from 1 to 3 percent in VFR green light conditions, while the 
Group 4 capacity improvement in IFR green light conditions range 
from 13 to 44 percent. In order to assess the general future trends ev- 
ident in the Capacity /p> estimates, the taskforce averaged the results 
for the three configurations examined In each equipment group and 
weather category. The average percentage increase or decrease from 
today's capacity developed from the results in Exhibit 5-4A is as follows:. 





Pre-1985 






Post- 1985 


Today's 
ATC Rules 


Group 
2 

2% 


Group 2 
Fall Back 

(1%) 


Today's 
ATC Rules 

(8%) 


Group 
4 


Group 4 
Fall Back 


VFR (2%) 


12% 


2% 


IFR same 


7% 


2% 


(5%) 


25% 


11% 


() decrease 













The following general trends are apparent: 



Without the proposed ATC system improvements, O 'Hare's 
capacity will continue to deteriorate through the post- 
1985 time period due to the projected increase in heavy 
aircraft from 15 percent today to 45 percent in the future. 



5-13 



In the pre-1985 period, the proposed Group 2 equipment 
is estimated to largely offset the capacity reduction caused 
by increased numbers of heavy aircraft. When vortex con- 
ditions allow use of reduced separations (green light condi- 
tions estimated to occur 40 percent of the year), Capacity rpj 
will be increased from 4 percent in VFR to 7 percent in IFR 
from conditions which will prevail if no ATC improvements 
are achieved, the greater benefit being realized during IFR 
weather. When vortex conditions are present, the Capacity (p) 
improvements are reduced to 1 percent in VFR and 2 percent 
in IFR. 

In the post-1985 period, the proposed Croup 4 equipment 
is estimated to provide greater benefits over conditions 
which will prevail if no ATC improvements are achieved. 
Capacity tp \ is estimated to be increased by 20 percent in 
VFR weather and 30 percent in IFR weather in green light 
conditions (estimated to occur 75 percent of the year) . In 
vortex fall back situations, the Capacity,... benefits will 
range from 10 percent to 16 percent respectively in VFR 
and IFR weather. 



5.3.2 If No Improvements are Made in the Existing ATC System , 

Increasing Numbers of Heavy Aircraft Will Reduce O'Hare's 
Future Capacity . 



Using the average Capacity /pj impact estimates identified in the 
preceding section, it is possible to assess the deterioration in 
Capacity (WA) which will occur in the pre-1985 and post-1985 per- 
iods due to the projected increase in heavy jet aircraft operations if 
no ATC improvements are implemented (do nothing) . This analysis 
was accomplished by applying the appropriate Capacity /pj increase 
or decrease to the weighted IFR and VFR Capacities (WA) developed 
with the AIRSIM model in Chapters 3 and 4 for two configuration selec- 
tion strategies. For reference see Section 3.1.4 for current Capacity (WA) 
based on the historic runway use pattern and Section 4.1.4 for the 
Capacity n/vA) which could be achieved by implementation of a revised 
pattern of runway use. The results of the do nothing analysis are sum- 
marized in Exhibit 5-8 along with estimates of Group 2 and Group 4 
equipment performance which will be discussed in the sections which 
follow. 

Depending on the configuration selection strategy employed (his- 
toric use or the alternative revised runway use pattern identified in 
Chapter 4), the average Capacity (WA) is estimated to decrease 
from the current 141-151 operations per hour to 138-149 operations 



5-14 



in pre- 1985 and 130-140 in the post-1985 period. It is interesting to 
note that the improved runway selection procedure with its more effi- 
cient runway use pattern can alone go a long way toward maintaining 
O'Hare's effective Capacity (WA) at tne current level through the post- 
1985 period. In effect, improved configuration selection can offset the 
impact of future increases in the number of heavy jet aircraft. 



5.3.3 O'Hare's Average Capacity ny^j With Implementation of Pro - 

posed ATC improvements is Estimated to be 141 in the Pre- 
1985 Period and to Increase to 156 in the Post- 1985 Time 
Period if O'Hare Continues to be Operated as in the Past . 



Based upon the average capacity improvements estimated to be 
provided by future ATC equipment groups as identified in Section 
5.3.2, it was possible to assess the net impact of ATC improvements 
on O'Hare's ability to effectively process aircraft operations. The 
analysis, like that in the previous section, was undertaken by adjust- 
ment of the current average Capacities (WA) developed in Section 
3.1.4 for the historic runway use pattern by the percentage Capac- 
ity (F) increase or decrease by weather category and ATC equipment 
group. The Capacities (WA) were further weighted to reflect the wake 
advisory system performance which is estimated to provide 40 per- 
cent utilization (green light) for the Croup 2 equipment and 75 per- 
cent utilization for the Croup 4 equipment. 

The results of this analysis are presented in Exhibit 5-8, also 
included are estimates based upon the delay optimized pattern of run- 
way use which is discussed in Section 5.5.2 of this chapter. The 
Group 2 equipment will potentially provide limited help in IFR weather 
conditions; VFR Capacity ty^A) remains similar to that achieved with 
the historical use of O'Hare runway system. The potential Group 4 
benefits appear considerably more attractive, VFR Capacity (WA) ' s 
estimated to increase to 157 movements per hour and, significantly, 
IFR Capacity (WA) ' s estimated to be raised to 153, a level nearly on 
par with VFR rates achieved with the historical use of the runways. 
This average weighted IFR Capacity (WA) ' n a Group 4 ATC equipment 
environment reflects a 21 percent increase from the current 126 oper- 
ations per hour as the airport has been operated in the past. 



5-15 



5.3.M Implementation of Increased System Automation and Improved 

Surveillance Capability in Order to Achieve the VFR Separa- 
tion Reduction Offered by the Wake Advisory/Avoidance Sys- 
tem May Unnecessarily Delay Near-Term Benefits of the System , 



In Section 5.2.1, it was noted that the WVAS system involves a 
double set of separation standards for each equipment group reflecting 
safe (green light conditions when wake vortices are known to be mov- 
ing out of the runway approach zone) and fall back standards (red 
light conditions when wake vortices are known to exist in the runway 
approach) . However, FAA estimates of future equipment performance 
provided the taskforce (see Appendix F) indicate that reduced sepa- 
ration in VFR conditions is not fully achievable without simultaneous 
implementation of increased system automation (basic metering and 
spacing) and improved surveillance capability. The Group 1 and 2 
ATC equipment improvements are estimated to provide a 1 mile reduc- 
tion in IFR separation standards from current conditions between ar- 
riving heavy aircraft and trailing aircraft of any type. However, no 
arrival separation reduction is estimated to occur during visual 
flight rule weather with either equipment group. The initial system 
automation step of basic metering and spacing to be accomplished in 
Croup 2 will reduce the delivery error increasing capacity in both 
IFR and VFR conditions; this benefit will be offset to some degree by 
an increase in the number of standard deviations required to reduce 
the probability of violation of safety buffers under a tighter, less 
flexible automated system. Thus, VFR arrival separation reductions 
are dependent upon the development of improved surveillance in 
Croup 3 and advanced metering and spacing with DABS in Group 4; 
equipment not estimated to become operational until the 1985 to 1990 
time period. 

The dependency of VFR arrival separation reduction on major 
surveillance and automation developments raises two concerns: 



First, since approximately 75 percent of the total annual 
delay at O'Hare is incurred in VFR operating conditions 
which prevail 85 percent of the year, the potential cost 
reduction offered by Groups 1 and 2 is largely limited to 
25 percent of the delay problem; notably the most disrup- 
tive operational conditions. VFR delay contributes sig- 
nificantly to the current cost of operation at O'Hare and 
will not be measurably improved initially according to 
current engineering and development equipment perform 
ance estimates. 

Second, from discussions with FAA engineering and 
development team leaders and observation of post 



5-16 



development advances of other hardware, upgraded 
automation (metering and spacing) and improved sur- 
veillance with potential to provide reduced VFR sep- 
aration may be the most difficult elements of the pro- 
gram to accomplish. The metering and spacing pro- 
gram has already sustained some slippage and from a 
practical standpoint may be the program element furthest 
from actual operational implementation. 



Bearing in mind these concerns, there appears to be consider- 
able difference of opinion among FAA experts with regard to the op- 
erational potential of the wake advisory equipment currently being 
installed atO'Hare. There is. some indication that reduced separa- 
tion benefits could be partially attained in both VFR and IFR without 
metering and spacing and improved surveillance through use of a 
simplified separation matrix for use by the controllers with green 
and red light condition designations. 

All taskforce analyses of operations in the pre-1985 time peri- 
od were conducted under the assumption that when no wake vortex 
is detected, the separation standards on final approach will be as 
shown in Exhibit 5-2. However, these separations are likely to be 
conservative in light of current FAA planning. 

The Vortex Advisory System (VAS) now being tested at ORD for 
operational suitability by FAA is intended to operate in two states: 



When wake vortices are determined to be within the 
approach "window", normal (6, 5, 4n. miles) wake 
vortex separations apply. 

When the VAS shows, by reference to meteorological 
information and the anemometer line, that vortices are 
not persisting in the "window", a green light appears 
to the controller, and 3 n. mi He separations on final 
may be used . 

If implemented, this will result in somewhat more favorable capacity 
and delay figures than the calculations indicate. 

Implementation of 3 n. mile separations under no vortex condi- 
tions is complicated by the fact that current IFR/VFR separation 
standards in the terminal area ahead of final approach now call for 
4 n. miles separation heavy-behind-heavy, and 5 n. miles small/ 



5-17 



large-behind-heavy; these separations are applicable to aircraft 
operating directly behind at the same altitude, operating directly 
behind less than 1,000' below, and when following a heavy jet con- 
ducting an instrument approach. These separation criteria were 
established in part as a precaution because of certain limited pene- 
tration measurements with test aircraft at altitude attempting to in- 
tercept wakes, and in part to make the separations in the terminal 
maneuvering area consistent with final approach wake vortex sep- 
arations. They may not be needed when the wake vortex does not 
persist in the final approach path, especially in practical ORD op- 
erations from feeder fixes to interception of the final approach path. 

An analysis is currently under way to establish whether and 
how much the wake separations in the terminal maneuvering area 
can be reduced when the separations on final approach revert to 
the 3 n. miles no vortex situation. Adjustment of these separa- 
tion standards is necessary if full benefit is to be achieved from the 
Vortex Advisory System. 

A similar divergence of opinion is evident with regard to the 
period of utilization of the green light separation standards. Cur- 
rent engineering and development estimates place the utilization 
rates at 40 percent with Croup 1 and 2 and 75 percent with Croup 3 
and 4 equipment. There is some feeling that these estimates are ex- 
tremely conservative indicating that greater capacity increase/delay 
reduction benefits may be attained through the wake vortex advisory 
system depending upon the results of the tests currently being con- 
ducted at O'Hare and other airports. 



5.4 FUTURE LEVEL OF AIRSPACE/AIRFIELD SYSTEM DELAYS 



Having estimated the future capacity of O'Hare by weather condition and 
ATC improvement equipment groups, it is necessary to examine the efficiency 
with which that capacity is realized. A limited analysis was indicated in order 
to establish the trend of future system delay characteristics. 

The methodology utilized to define future system performance was as fol 
lows. In Chapter 3, a methodology for "annualizing" the cost of today's delay 
at O'Hare was developed. This methodology was extended in order to annual 
ize the cost of delay at O'Hare for pre- 1985 and post 1985 ATC and fleet mix en 
vironments. The reason for extending the methodology was to estimate, in terms 
of constant 1975 dollars, the expected cost of future delays at O'Hare assuming 
the airport continues to operate as it has in the past. 

A major difference in the operation of future air traffic control systems 
from today's systems will be the existence of "green light" and "red light" con 
ditions, i.e., no vortex or vortex conditions, respectively. The first step in 



5-18 



extending the original annualization methodology was to account for this phenom- 
ena. For planning purposes, it was assumed that these utilizations would be 
applied uniformly over all configurations. Therefore, the operational days per 
year in each configuration were divided between "green light" and "red light" 
periods of use according to the utilization percentages in Exhibit 5-3. 

A series of simulation experiments were conducted to estimate pre-1985 
and post-1985 (Group 4 ATC and 45 percent heavy mix) delay levels. From these 
experiments, percentage relationships were developed for Configurations 3 in 
IFR and 5 in VFR, which were considered (for this analysis) representative of 
the delay increase or decrease for all of O'Hare's different configurations. 

The results of the analysis of pre-1985 and post-1985 system performance 
are described in the paragraphs which follow. 



5.4.1 If No Future ATC Improvements Are Achieved, the Annual 

Cost of Delay at O'Hare Stated in 1975 Dollars Will Escalate 
to $69,800,000 in the Pre-1985 Period and to $72,600,000 in 
Post-1985 Time Period if the Airport Continues to be Oper - 
ated as it Has in the Past. 



The analysis of future capacity indicated that the projected in- 
crease in the number of heavy jet aircraft will result in continuing 
deterioration of O'Hare's Capacity (WA) through the post-1985 time 
period if no steps are taken to improve the ATC system. 

Two simulation experiments (numbers 14 and 78) were conducted 
using the post- 1985 45 percent heavy 135 operations per hour sched- 
ule and today's ATC rules to determine the potential impact of taking 
no ATC development action. The delays resulting from these experi- 
ments are presented in Exhibit 5-4 and graphically illustrated in Ex- 
hibits 5-7 and 5-8. Based upon the historic runway use pattern ident- 
ified in Chapter 3 and by conversion of total airside and groundside 
delay minutes to dollar costs,!' the results indicate that the cost in 
1975 dollars of delay under normal conditions in pre-1985 will be ap- 
proximately $69,800,000 annually and will approximately double 
current O'Hare delay costs rising to $72,600,000 in the post-1985 
period. 



1/ The following weighted (weighted according to fleet mix) average 

costs per minute of delay were assumed for the two future scenarios: 
Pre-1985: $10. 70 per minute of airside delay; $6. 70 per minute of 

groundside delay. 
Post-1985: $12.20 per minute of airside delay; $7. 50 per minute of 

groundside delay. 



5-19 



4- 



3- 



2- 



< 

UJ 

a. 
o 

si 

Q 

UJ 

8 

ff 

UJ 

5 




83 



3.2 



© @ 

2.2 mni2.2 




CONFIGURATION 5 



TODAY DO GROUP 2 GROUP 2^ 

(baseline 15% NOTHING (27% heavy) (fallback 27% 
heavy) (27% heavy) heavy) 

VFR 



24- 

20- 

16 
12 

8 

4 



NOTE: 

Group 2 ATC-27-6 
heavy 135 hourly 
operations 



(67) 



,17.9 





9.5 



1 17.1 



CONFIGURATION 3 



TODAY . DO GROUP 2 GROUP 2 

(baseline 15 "8 NOTHING (27% heavy) (fallback 27% 

heavy) (27\ heavy) heavy) 

IFR 



#0 Experiment 



O'Hare Delay Taskforce Study 
Chicago O'Hare International Airport 



TITU: 



PRE -1985 DELAY 



L a n d r u m 8c B row n 

AIRPORT 'CONSULTANT'S. 



|U*WHT: 

5-6 



5 20 



4- 



3^ 



1- 



z 
o 




H 




< 




K 




UI 




Ol 




o 




DC c 




a. £ 




3 




> c 




21 

UI 




Q 




UI 
(3 


24 


< 




C 




UI 




§ 


20 




16 




12 




8 




4 




CONFIGURATION 5 



TODAY DO GROUP 4 GROUP 4 

(baseline 15 'o NOTHING (45% heavy) (fallback 45% 
heavy) ( 45 * heavy) heavy) 



® 



VFR 



24.7 



NOTE: 

Group 4 ATC-45% 
heavy mix 135 hourly 
operations 




9.6 




CONFIGURATION 3 



TODAY DO GROUP 4 GROUP 4 

(baseline 15% NOTHING (45% heavy) (fallback 45% 



heavy) 



(45 'o heavy) 



heavy) 



IFR 



Experiment 



O Hare Delay Task force S^udy 
Chicago 0!Hare International: Airport 



iTfTtf: 



POST- 19*5 DELAY 

5-21 



Landrurn & Brown: 



5-7 



5.4.2 If Croup 2 and Group 4 ATC System Improvements Are 

Achieved, the Annual Cost of Delay at O'Hare in the Pre- 1985 
and Post-1985 Periods Will be Approximately $42,300,000 and 
$25,900,000 Annually, Respectively, as Expressed in Constant 
1975 Dollars if O'Hare is Operated as in the Past . 



Exhibits 5-6 and 5-7 depict the results of simulation experiments 
conducted with the pre- 1985 and post- 1985 schedules with Croup 2 
and Croup 4 ATC equipment in Configuration 5 for VFR conditions 
and in Configuration 3 for IFR weather. It should be stressed that 
the level to which operations were scheduled in the two future base 
schedules was 135 operations per hour, slightly less than today's. 
The main difference between future schedules and those of today 
will be the number of heavy aircraft, 27 percent in the pre-1985 per- 
iod and 45 percent in the post-1985 period. 

Two points of interest should be noted regarding the delay sta- 
tistics in the exhibits. First, during VFR weather, delay levels not 
unlike those experienced today might be expected, while during IFR 
weather with vortex conditions groundside delays much greater 
than today's may be expected. This does not imply that the Croup 2 
equipment will not reduce delays — only that it will not reduce them 
quickly enough to offset the effects of the increasingly heavy fleet 
mix. This is especially true during IFR vortex conditions, in which 
fall back separations would revert to those in effect today. Second, 
it is evident that the overall effect of Group 4 ATC equipment will be 
to maintain delays at levels not worse than today's during vortex 
conditions — expected 25 percent of the time while for the majority 
of the time (75 percent no vortex or green light conditions are ex- 
pected) reducing delays significantly below those experienced today. 

Having determined the relationship between pre-1985 and post- 
1985 arrival and departure delays (under vortex and no vortex con- 
ditions) and based upon the historic runway use pattern defined 
in Chapter 3, the cost of future annual delays were estimated. In 
the pre-1985 period, it is estimated that the cost of delay will be 
$42,300,000 annually, while in the post-1985 period, delays are 
estimated to cost $25,900,000. 



5.4.3 The Potential Net Delay Savings Of Future ATC System 

Improvements Appear Substantial. The Equipment Is Esti 
mated to Yield Delay Cost Savings of $27,500,000 in the 
Pre-1985 Period and $46,700,000 in Post-1985 Over Delay 
Costs at O'Hare if No ATC Improvements Are Realized . 



The net delay cost reduction benefits of the Croup 2 and 4 ATC 
equipment can be estimated by comparison of the annual delay costs 



5-22 



resulting from operations in the pre- 1985 and post- 1985 period with 
and without the proposed system improvements. In Section 5.4.1, 
pre-1985 O'Hare delays were estimated to cost the aircraft operators 
$69,800,000 and to rise to $72,600,000 annually in the post-1985 
period in 1975 dollars. These operating costs were estimated in 
Section 5.4.2 to be reduced to $42,300,000 and $25,900,000 by im- 
plementation of the ATC improvements. The differential between 
these values, $27,500,000 in the pre-1985 and $46,700,000 in the 
post-1985 period, represents the annual net benefit provided by the 
Group 2 and Croup 4 equipment improvements. 



5.5 OTHER FUTURE DELAY REDUCTION OPTIONS 



The findings of future system performance indicate that ATC improvements 
alone are not a panacea for future delay problems and that judicious management 
of demand and system operations will be required to maintain the delay costs at 
acceptable levels in the future. The cost of airside and groundside delays can be 
expected to increase in the future. Even stated in constant 1975 dollars, the aver- 
age cost per minute of delay will rise due to increasing numbers of heavy aircraft 
which, in total, use more fuel than smaller aircraft. Just as current delay reduc- 
tion options were characterized as air traffic control procedural, airport use pol- 
icy, and airport development, so may future delay reduction options be charac- 
terized. The findings of the extensive analysis of current delay reduction options 
presented in Chapter 4 closely parallel those in the future. 

Each of the delay reduction options examined extensively in Chapter 4 has 
the same or greater merit in the future planning period. In addition, major facil- 
ity development actions, such as new terminal, gate, or runway construction, be- 
come viable candidates for analysis of their delay reduction potential. However, 
the scope of the taskforce effort on future airport development options at O'Hare 
was restricted due to the on-going long-term master planning study. It was con- 
cluded that the taskforce effort should emphasize investigation of the future delay 
reduction potential afforded by improved ATC equipment now in the planning and 
development phases. While the taskforce could have chosen to re-examine each 
delay reduction option evaluated in Chapter 4, it was concluded that while the 
incremental benefit of each would undoubtedly increase, the relative value of one 
option versus another was unlikely to shift significantly. Thus recomputation of 
the future benefits would add little additional data upon which to draw conclu- 
sions with one notable exception. 

That exception, the future benefits to be derived from the judicious selec- 
tion of operational runway configurations which make up the airport use pattern, 
appeared to be critical to the assessment of future practical scheduling levels in 
Chapter 6 of the study. Also, potential problems with today's most widely used 
configuration indicated a need to assess future configuration selection options. 



5-23 



5.5.1 As The Percentage of Heavy Aircraft At O'Hare Increases, 

The Performance of Today's Most Widely Used Configuration 
Will Deteriorate Significantly . 



Taskforce Configuration 1 (arrivals on 27R, 32L and departures 
on 27L, 32R) is currently used approximately 28 percent annually. 
The configuration is not without operational limitations, caused mainly 
by wake vortex at the far intersection of 27L with 32L. Today, approx- 
imately 50 percent of all heavy arrivals on 32L cross through the inter- 
section in the air, causing a two minute wait for departure clearance 
to departures on 27L. In addition, if heavy departures are allowed 
on 27L, their vortex at the intersection will cause a two minute delay 
to aircraft inbound to Runway 32L. In today's environment, this prob- 
lem is eliminated by segregating most heavy departures to the north 
half of the field while in Configuration 1 . 

Both FAA capacity model experiments and AIRSIM simulation 
experiments have indicated a deterioration in performance of this 
configuration in a 27 percent heavy environment. This is because, 
as the number of heavy aircraft increase, it becomes increasingly 
difficult to segregate enough heavy aircraft to the north to eliminate 
the vortex problem on the south intersection. There are actually two 
options for solving this problem. The first is an ATC procedural 
option in which a replacement configuration is found for Configura- 
tion 1 when the delays in that configuration become intolerable. The 
second is an airport development option in which the intersection 
location is altered through runway extension. This option will be 
addressed in the City of Chicago's Master Plan Study. 



5.5.2 If the Configuration Selection Process is Revised to Reflect 

Increased Use of the Most Efficient Configurations, O'Hare's 
Capacity (WA) With Implementation of Proposed ATC Impro ve- 
ments Will be 152 Operations Per Hour in the Pre- 1985 Period 
and 169 In the Post- 1985 Time Period. 



Recomputation of average airfield Capacity (WA) based upon a re- 
vised runway use pattern presents a more optimistic picture of future 
O'Hare operating capability than that presented in Section 5.3.3. The 
results of this analysis were presented in Exhibit 5-8 and demonstrate 
that operation of O'Hare's most efficient configurations continues to be 
an effective means to increase capacity through the post- 1985 time 
period. On average, the improved selection of runway configurations 
is estimated to provide an average increase of 11 operations per hour 
over that achievable with the historic use pattern regardless of ATC 
equipment improvements. 



5-24 



The future benefits of more effective configuration selection may 
be considerably higher than those indicated in this study. Examina- 
tion of the Capacity (pj estimates in Exhibit 5-5 indicates that the con- 
figurations with the greatest degree of runway independence (ones 
with the highest capacity) appear to respond most readily to the ATC 
improvements. Configurations 4 and 13, two of the highest capacity 
layouts available at O'Hare, consistently show the highest percentage 
increase in capacity of the six configurations examined in all equip- 
ment groups. Configuration 4 shows the greatest improvement, an 
increase of 44 percent with Group 4 equipment in IFR conditions. 
While certainly not conclusive, this evidence provides further di- 
rection for analysis in the master plan study. 



5.5.3 If O'Hare's Most Efficient Configurations Are Utilized, The 

Costs of Annual Delays Are Estimated to be $29,200,000 in a 
Pre-1985 Environment and $17,600,000 in a Post- 1985 En- 
vironment. Thus Optimized Configuration Selection Would 
Represent Cost Savings of $13,100,000 and $8,300,000 For 
A 135 Operations Per Hour Schedule Over the Annual Cost 
of Delay Under the Historic Runway Use Pattern . 



The wake vortex problem described in Section 5.5.1 for Config- 
uration 1 will, in the future, be aggravated by increasing numbers 
of heavy aircraft. The problem will be alleviated to some extent by 
expected decreases in vortex separation times with Group 2 and 
Group 4 ATC equipment, however, the Group 2 vortex fall back sep- 
aration is expected to be the same as today's 120 seconds. Further, 
this condition is expected to occur at least 60 percent of the time. 
Therefore, relief must be found through the use of more efficient 
configurations. 

In Section 5.4:2, the annual delay costs in pre-1985 and post- 
1985 ATC and fleet mix environments were estimated for the historic 
runway use pattern. The same methodology was used to estimate the 
annual level of pre-1985 and post-1985 delay costs based upon the 
delay optimized runway use pattern developed in Chapter 4. The 
annual level of O'Hare delays resulting from the improved runway 
use pattern are estimated to be $29,200,000 in the pre-1985 period 
and $17,600,000 in the post-1985 period if O'Hare's most efficient 
configurations are utilized. Improved configuration selection thus 
yields a benefit of $13,100,000 in pre-1985 and $8,300,000 in post- 
1985 over conditions which will occur if the airport continues to be 
operated as it has in the past. 



5-25 



In Section 5.4.3, the net benefits provided by future ATC im- 
provements were estimated to be $27,500,000 for Croup 2 in pre- 
1985 and $46,700,000 for Group 4 in the post-1985 period. If an im- 
proved runway use pattern based upon selection of more efficient 
configurations is achieved, the net benefits provided by ATC equip- 
ment improvements will be decreased to some extent in both time 
frames. 

The benefit comparisons of future ATC equipment discussed in 
this and preceding sections are facilitated by reference to Exhibit 
5-8, which summarizes all future capacity and delay cost estimates. 



5.6 THE POTENTIAL IMPACT OF ASTC, RNAV, AND MLS 



The purpose of this section is to provide a discussion of the potential impact 
ASTC, RNAV, and MLS have on operations atO'Hare. This discussion largely 
summarizes the material presented in Appendix F which has been drawn from a 
number of previous studies, some specific to O'Hare. However, to the degree 
that the taskforce has gained insight in the course of the study into the potential 
utility of these program items, qualitative assessments are included. It should be 
noted that the taskforce's primary emphasis was capacity and delay oriented and 
no attempt was made to provide original quantitative evaluation of ASTC, RNAV, 
and MLS capability. 



5.6.1 The ASTC Program Could Enhance Runway Configuration 

Selection Options In Periods of Low Visibility and Will In- 
crease Local and Ground Controller Workload Capabilities. 



The ASTC program is oriented toward aiding both the local and 
the ground controller with improved automated displays ultimately 
using surveillance data and digitized displays, In low ceiling and 
visibility conditions when the ground movement of aircraft is ob- 
scured from tower cab view, airport surface traffic control becomes 
critical to expeditious handling of the heavy volume of aircraft being 
processed atO'Hare. While a number of improvements have and will 
be made to ASDE-2 system reliability (better target resolution, and 
increased rainfall penetration), two future evolutions of ASTC equip- 
ment are envisioned in the PAA engineering and development program 
The following subsections discuss these proposed improvements. 



5-26 



1 


TUE FRAME 


ATC 


;<U,^VAY 

USE 
PATTERN 


■ ANNUAL 
OELAY COST 
(MILLIONS) 


WEIGHTED nOUKLY 
CAPACITY {JA) 


PRE- 1985 
27% HEAVY MX 


TO JAY 


^HISTORIC 


69.8 


VFR 


140 


IFR 


126 


AVERAGE 


138 


B OPTI,VtlZEJ 


36.1 


VFR 


152 


IFR 


130 


AVERAGE 


149 


GROUP 2 


^hlSTORIC 


42.3 


VFK 


143 


IFR 


131 


AVERAGE 


141 


S OPTUIZEO 


29.2 


VFR 


155 


IFR 


135 


AVERAGE 


152 




TOO\Y 


^HISTORIC 


72.6 


VFR 


132 


POST- 1985 
45 HEAVY MX 


IFR 


120 


AVERAGE 


130 


a OPTf,vUZEO 


48.2 


VFR 


143 


IFR 


124 


AVERAGE 


140 


CROUP 4 


^HISTORIC 


25.9 


VFR 


157 


IFR 


153 


AVEKAGE 


156 


a OPTIMIZEO 


17.6 


VFK 


171 


IFR 


158 


AVERAGE 


169 


bee bection 3.1.4 
U bee bection 4.1.4 



O'Hare Delay Taskforce|fSludy % 
Chicago O Hare International {Airport 



Capacity# WA % and Delay 
Costs Pre and Post -1985 

5-27 




f.R^HSONSULT*N^; 



CXNMMT: 

5-8 



5.6.1.1 A Study by the DOT Transportation Systems Center 

(TSC) Estimates That Proposed ASDE-3 Equipment 
Will Limit Poor Visibility Performance Loss to 5 Per- 
cent for Local Controllers and 43 Percent for Ground 
Controllers From Current Levels of 25 Percent and 
57 Percent Respectively . 



The ASDE-2 improvements will result in a controller 
display which is nearly as good as state-of-the-art techno- 
logy can produce for an imaging analog radar. ASDE-3 bene- 
fits will be in further improving ground surveillance relia- 
bility, maintainability, and availability and in improving 
rainfall penetration. In terms of controller performance, 
the impact of ASDE-3 has been estimated in the previous 
study of O'Hare for a single runway operating in a mixed 
mode — similar to Configuration 14 in this study. The re- 
sults of that analysis are presented in Exhibits 5-9 and 5-10 
for local and ground controller respectively. The figures 
also show TAGS improvements which are discussed in Sub- 
section 5.6.1.2. Using good visibility conditions as a base- 
line, the current equipment (position reporting only) re- 
sults in a reduction in local controller performance by 25 
percent while the effect of ASDE-3 is to reduce the loss of 
performance to 5 percent. Current equipment in poor vis- 
ibility results in a ground controller performance loss of 
57 percent which is reduced to 43 percent by ASDE-3. The 
improvements are expected to be greater under the future 
ATC environment as higher runway capacities result in 
more ground traffic congestion. 



5.6.1.2 The TSC Studies Indicate That The TAGS System In 

Addition to Providing Discrete Aircraft Identity to the 
Ground Controller Will Reduce Voice Communication 
Requirements and Possibly Provide Local Control with 
Airborne Coverage Near the Airport Currently Lost 
to the ASR. 



In addition to the discrete aircraft identity information 
to the ground controller, two system options offering poten- 
tial benefits at O'Hare will be available. 



5-28 



§ 



3 
OE 

K 
O 

z 

E 

S 

eo 

z 
o 

g 

B 



Good Visibility; 



Poor Visibility 




CURRENT VFR FUTURE CURRENT FUTURE 

(visual control) VFR CONTROL IFR CONTROL IFR CONTROL 
(TAGS) (position (ASDE + position 

reports only) reports) 



Note: Numbers in ( ) are percentage change from current baseline controller 
performance in visual conditions. 

Estimates based on data acquired at Chicago-O'Hare 
Airport; these data apply to a single runway with 
mixed arrivals and departures. 



O'Hare Delay Task forced Study 
Chicago 'O'Hare International Airport 



TITLE: 



LOCAL CONTROLLER 
PERFORMANCE 

5-29 



Appendix F x 



5-9 



AC 
UJ 

_l 
-J 

o 

DC 



Good Visibility 



Poor Visibility 




CURRENT 

VFR 

CONTROL 
(visual control) 


FUTURE 

VFR 

CONTROL 

(TAGS) 


CURRENT 

IFR 
CONTROL 
(position 


FUTURE 

IFR 
CONTROL 
(ASDE 3 • 






reports only) 


position ri 



Estimates based on data acquired at Chicago O'Hare Airport 



Estimates based on data acquired at Washington National Airport 



Note Numbers in ( ) arv percentage change hen 
current baseline controller performance in 
visual conditions 



O'Hare Delay Taskforce Study 
Chicago O'Hare International Airport 



j TITLE 



GROUND CONTROLLER 
PERFORMANCE 



Appendix £ 



1 EXHIBIT: 

5-11 



5-30 



The first will permit the TAGS sensor to detect activa- 
tion of the Ident button on the ATCRBS beacon in each air- 
craft. Activation by the pilot can be displayed to the cab 
controllers (e.g., by a flashing data block leader) and can 
be used in place of verbal taxi requests, to acknowledge 
ground/local hand-offs, and in place of verbal pilot posi- 
tion reports to cue aircraft location. This could reduce 
voice channel loading in all visibility conditions and pro- 
vide a more efficient communication system to both control- 
ler and pilot. Reduction in voice channel loading of 10 per- 
cent over good visibility loading has been estimated. 

The second feature will present an integrated display 
to local control covering aircraft on final approach, on or 
near the runways, and on initial departure. It is possible 
that TAGS may be able to fill in the airborne coverage with^ 
in a mile or so of the airport currently lost to the A$R. Air- 
borne data will be supplied to TAGS from ARTS on an auto- 
mated data transfer when available. The key information 
to be displayed is estimated time-to-threshold for the arriv- 
al system. The computer will utilize position, speed, arsd 
aircraft type to provide the estimate. When factored into 
controller strategies, it has been estimated that this infor- 
mation could increase the good visibility local control capac- 
ity and runway capacity on certain difficult to operate con- 
figurations. ,,,*,... 

Based upon evaluation of a single runway operating in 
a mixed mode at O'Hare, TAGS is estimated to increase 
local controller performance by 9 percent. Ground control- 
ler performance is estimated to be improved by 10 percent 
over the current controller performance in the best of cir- 
cumstances. 



5.6.1.3 The ASTC Appears to the Taskforce to Offer High 

Potential for Direct and Indirect Improvement of 
O'Hare Future Capacity . 



it would appear that the aircraft identification capability 
of the TAGS system could reduce the time required for the 
controller to ascertain positively that an arriving aircraft 
can hold short of an intersecting departure runway or has 
cleared the runway under low visibility conditions. This 
could potentially increase the throughput potential of key 
runway combinations such as 14R arrivals with 27L depar- 
tures. 



5-31 



Another aspect of the TAGS system that has the poten- 
tial to enhance system capacity under all weather conditions 
is the improvement of the positive handling of aircraft on the 
O'Hare terminal circular taxiway system. Air traffic con- 
trollers have noted with some concern that the high capacity/ 
lew delay three arrival runway configurations tend to con- 
centrate large numbers of aircraft in the vicinity of the apron/ 
gate complex. Due to gate limitations and flow channel re- 
strictions, the level of congestion increases causing ground 
traffic control difficulties. To the degree that improved 
ground traffic surveillance and control will reduce the 
ground controller's workload, the use of these preferred 
configurations may well be enhanced by TAGS or some other 
improved ground surveillance technology. While indirectly 
related to TAGS, the potential benefits of improved configu- 
ration selection run into millions of dollars annually as de- 
scribed in Chapter 4 and in a previous section of this chap- 
ter. 

Another possibility could be use of the positive time-to- 
threshold data envisioned in the automated data transfer 
from ARTS to relax the current air traffic control procedures 
regarding operations on intersecting runways. As noted in 
Chapter 3, current air traffic procedures require departures 
on runways intersecting with active arrival runways to hold 
when an arriving aircraft is within 1 to 2 miles of the thres- 
hold . This current procedure restricts departure capacity, 
particularly when the intersection is a far one. With positive 
display in the tower cab or approaching aircraft time over 
threshold combined with possible filling in of airborne cov- 
erage within a mile or so of the airport, it is conceivable 
that the 1 to 2 mile departure hold procedure could be re- 
duced. Such a procedural change would enhance the capac- 
ity of many of O'Hare's best configurations. 

In addition, this equipment seems to have the potential 
to provide additional configuration selection options in low 
ceiling and visibility conditions, perhaps reducing or elim 
inating the dependence on use of mixed arrivals and depar 
tures which occurs approximately 5 percent of the year due 
to visibility limitations. The use of additional runways would 
increase capacity and decrease delay in the most critical area 
of the O'Hare operations. 



5 32 



5.6.2 An FAA Study Indicates that Area Navigation (RNAV) Could 

Reduce the O'Hare Terminal Area Controllers Workload With 
No Corresponding Reduction in System Capacity and Might 
Reduce Aircraft Operating Costs by $2,000,000 to $5,700,000 
Annually In a 100 Percent RNAV Environment . 



In the present ATC system, navigation is performed along a series 
of straight line courses known as radiais which extend radially from 
VORTAC and VOR ground stations. This contains all routes to a ser- 
ies of straight line segments joining one VOR/VORTAC to another. The 
term Area Navigation (RNAV) refers to navigation systems which pro- 
vide navigation along any course to any destination or to any intermedi- 
ate way point. The term 2D is commonly used to refer to RNAV sys- 
tems which provide navigation in the horizontal plane to a point de- 
fined in two dimensions by latitude and longitude or a bearing and a 
distance from the VOR/VORTAC ground station. 3D RNAV systems add 
the third vertical dimension of altitude and 4D RNAV systems add the 
fourth dimension of time. 

If all aircraft are RNAV equipped, RNAV routes could help elim- 
inate some of the airspace congestion brought about by increasing 
traffic levels. A previous study of real-time terminal area simula- 
tion at National Aviation Facilities Experiment Center (NAFEC) has 
concluded that: 



Significant reductions in controller communications 
time were observed as the percent RNAV mix increased. 

The controllers are capable of operating in a mixed VOR/ 
RNAV environment with reduced workload and no reduc- 
tion in system capacity, 



Based on RNAV terminal area design for ORD (see Appendix F 
for details), the fuel and time savings for 2D and 3D RNAV were esti 
mated to develop the annual air carrier economic savings at O'Hare 
in comparison to the current VOR system. Assuming a conservative 
fuel cost of $0,036 per pound and a cost for time of $9.62 per minute 
for air carrier operations, the following savings were developed for 
a 100 percent RNAV environment versus the existing system by this 
FAA study: 



5-33 





Fuel 


Time 


Total 




(Dollars) 


(Dollars) 


(Dollars) 


2D 


$ 867,528 


$1,606,540 


$2,474,068 


3D 


1, 187,107 


2,004,663 


3,191,770 


Total 


$2,054,635 


$3,611,203 


$5,665,838 



The same study estimated that a 4D RNAV system would enable further- 
increases in the delivery accuracy of the aircraft at the gate of the 
final approach. An analysis of the controller instruction reduction 
for O'Hare with arrivals on 27R and 32L and departures on 32R, 27L, 
indicated that the communication reductions are substantial in a 100 
percent RNAV environment on the order of 30 to 60 percent. These 
estimates compared favorably with the detailed RNAV simulation con- 
ducted at NAFEC. 

It is interesting to note that communication reduction benefits 
are not found only in a 100 percent RNAV environment, but also ap- 
pear worthwhile even for a mixed environment in which only 25 per 
cent of the traffic is RNAV equipped. As a percentage of RNAV traf 
fie increases, so do the benefits. Also, while no increase in airfield 
operation rates was found in the simulations of RNAV operations, there 
was no decrease in airfield operation rates in the simulations com- 
pleted to date. 



5.6.3 Installation of Microwave Landing Systems at O'Hare H a s Not 

Been Studied, But MLS May Have Potential Environme ntal 
Impact Reduction, Airspace Conflict Reduction and A i rfi e I d 
Layout Applications . 



MLS has several potential applications at O'Hare which have not 
been fully studied to date. Possible applications include: 



The curved approach capability of MLS may be useful 
at O'Hare in developing noise abatement procedures 
hy routing traffic away from populated areas, over 
forest preserves, highways, and less noise sensitive 
industrial areas. 



5-34 



The curved approach capability may be useful in reso- 
lution of the O'Hare 32L/Midway 13R arrival conflict 
and may also be of value in reducing the airspace inter- 
action with Palwaukee and Clenview airports. 

MLS will have a smaller critical area with significantly 
fewer restrictions on traffic flow. This feature should 
allow more flexibility in placement of the navigational 
aids and spacing of taxiways and holding aprons. 

MLS could provide sufficient frequency channels to allow 
assignment of individual frequencies to the runway ends 
at O'Hare (4R/22L, 4L/22R, 9L/27R and 9R/27L) making 
more runway configurations available when maintenance 
is conducted on an MLS at a particular runway end. 



Curved approach potential has not been studied for operational 
feasibility in O'Hare's congested terminal airspace. Detailed study 
of the application of MLS to O'Hare will be necessary to provide mean- 
ingful benefit/ cost evaluation. The O'Hare and Midway master plan 
studies will provide one means to examine the potential benefits of 
MLS. 



5-35 



6. DEMAND/DELAY RELATIONSHIPS 



The purpose of this chapter is to present the findings of all analyses con- 
ducted to determine the relationships between air traffic demand and delay in 
the present and future time periods. In order to establish these relationships, 
experiments were designed employing the A1RSIM model in conjunction with the 
September baseline schedule (SI) and six future operations schedules (F1 - F6 — 
see Appendix A) for both the pre-1985 27 percent heavy and post-1985 45 percent 
heavy fleet mix assumptions. The pertinent experiments are highlighted in Ex- 
hibit 6-1, the experiment design matrix, along with the results from these ex- 
periments in Exhibit 6-1A. The relationships presented in this chapter were 
empirically determined from a limited number of simulation experiments and 
should be interpreted in a relative or comparative sense. The methodology for 
constructing the demand/delay relationships varies and is so noted. Notwith- 
standing these limitations, the results furnish insight into the relationships be- 
tween fleet mix, ATC equipment groups, airline scheduling strategies and de- 
lay . 



6.1 EXISTING DEMAND/DELAY RELATIONSHIPS AT O'HARE 



The purpose of this section is to present empirically derived relation- 
ships between scheduled movement levels (demand) and average delay per oper- 
ation (8AM - 8PM) atO'Hare under assumptions of existing air traffic control rules 
and procedures. These relationships were determined for both non-optimized 
and optimized patterns of runway use (refer to Sections 3.1.4 and 4.1.4, respec- 
tively) in VFR and IFR weather conditions at three levels of scheduled activity. 
The relationships are presented graphically in Exhibit 6-2 and are hereafter re- 
ferred to as delay curves. 

The methodology employed to develop the delay curves involved estab- 
lishing a weighted average delay (weighted according to percent runway use) at 
the Baseline September 1975 level of average peak hour operations (137) for con- 
figurations in both the optimized and non-optimized runway use patterns. First, 
representative configurations for VFR and IFR were simulated at an air carrier 
volume level reduced by 10 percent. The changes in delay of these configura- 
tions from the delay of the same configurations at the baseline demand level were 
considered representative of the changes in delay which would occur in the 
weighted average baseline delay. The delay data from both the baseline and the 
reduced volume experiments were then graphically plotted in Exhibit 6-2. It 
should be noted that in an absolute sense the curves, as drawn between the 126 
and 137 demand levels, are an understatement of average VFR and IFR conditions 
because of the assumption of linearity between delay as a function of demand for 



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130 135 140 145 

AVERAGE PEAK HOUR DEMAND (operations) 



150 



ii nmapMHi 



O'Hare pelay Taskforce|St{jdy 
Chicago OJHare International Airport 



TITLE: 



DELAY VS DEMAND 
EXISTING SYSTEM 



m 



'JISXHJBlt: 



Landrum & Brow 

:' , , ';, »,HPO«T CONSULTANTS 



62 



the configurations investigated and the fact that the delay implications of opera- 
tions in VFR weather less than 3500/5 and IFR weather below 500/1 were not 
fully accounted for. Because of the relative flatness of the curves over this re- 
gion of demand, the error introduced is not serious. However, at increased de- 
mand levels, the error introduced, by failing to fully account for all weather 
conditions and the non linear relationship between delay versus demand for each 
configuration, would result in a significant understatement of delay . For this 
reason, the data base for the increased demand experiments was extended to 
account for all weather conditions and the non-linearity of change in delay versus 
change in demand for the configurations investigated through extrapolation and 
interpolation. 

From the delay curves in Exhibit 6-2, two key observations may be made: 



Delays during IFR weather are significantly greater than delays 
in VFR weather under any scheduled level of demand investi- 
gated. 

As the optimized runway use pattern recommended by the task- 
force is increasingly utilized, the potential will exist to: 

decrease today's average IFR and VFR delays by 3 
and 2.6 minutes per operation, respectively, at the 
current activity level, or 

increase the average hourly activity level by ap- 
proximately 4 to 5 operations without increasing 
delay levels over those experienced today. 

The potential for increased scheduled activity at O'Hare is not to be construed 
as a recommendation but is merely an observation of potential system capacity im- 
provement offered by the optimization of the runway use pattern. Operation at a 
higher volume of activity would decrease the delay reduction benefit identified in 
this analysis; however, there is potential for increased capacity at O'Hare with 
the facilities available. The extent to which this available additional capacity 
should be employed for delay cost reduction or for demand increases and the 
timing of such actions is beyond the scope of this study. 

The important fact to note, which the curves demonstrate, is that delay in 
IFR weather is significantly greater than that in VFR and is extremely sensitive 
to increases in demand. Planning for future increases in scheduled activity 
should give careful consideration to the region of IFR delays. 



6-6 



6.2 FUTURE DEMAND/DELAY RELATIONSHIPS UNDE R EXISTING ATC SEPARA- 
TIONS. 



For purposes of comparison it was desired to estimate the levels of delay 
which might be experienced at O'Hare if no future improvements are made in air 
traffic control equipment. This represents the "do nothing" alternative with re- 
spect to ATC hardware improvement and, although such conditions are not ex- 
pected, does furnish a basis for estimating the impact on delay of the mix of heavy 
aircraft in the fleet without a reduction in aircraft separation. 

The demand/delay relationships for the "do nothing" alternative are pre- 
sented in Exhibit 6-3 in the form of delay curves. Simulation experiments were 
conducted in VFR and IFR weather conditions against both the pre-1985 and post- 
1985 demand schedules. The demand/delay data points, one resulting from each 
experiment, were then used to vertically locate the 4 delay curves in Exhibit 6-3. 
The shape of each delay curve was assumed the same as the VFR and IFR curves 
of Exhibit 6-2 for the optimized pattern of runway use. For purposes of compar- 
ison, the current VFR and IFR delay curves for the historic runway use are also 
shown in Exhibit 6-3. 

It is apparent from the data presented in Exhibit 6-3, that if the volume of 
activity is increased significantly and ATC improvements are not added, greatly 
increased levels of delay will be experienced in IFR weather conditions. A 10 
percent increase in demand will result in approximately a 200 percent increase 
in IFR delay. In VFR operating conditions delay is estimated to be less sensitive 
to demand increases, rising approximately 80 percent as a consequence of a 10 
percent increase in demand. Further, as the percentage of heavy aircraft in- 
creases, delays in IFR weather will rise significantly. At the current operating 
level of 135 to 140 operations per hour, an increase from the current 15 per- 
cent heavy mix to 27 percent heavies is estimated to escalate delay by 40 percent; 
at 45 percent heavies, aircraft delay is estimated to be 100 percent greater than 
at 15 percent heavy mix. The sensitivity of delay to increased numbers of heavy 
jet aircraft is even greater at higher demand levels. A relatively small penalty 
is estimated to be associated with an increase in heavy aircraft from 27 percent 
to 45 percent in visual weather conditions. 

Regardless of the runway use and scheduling strategy employed, IFR 
weather conditions will continue to constrain the future level of operations which 
can effectively be scheduled at O'Hare in bad weather months unless future ATC 
equipment improvements are achieved to reduce aircraft separations in instru- 
ment operating conditions. 



6-7 




O Hare Delay; Task force Study 
Chicago O Hare 'International Airport 



DELAY VS DEMAND 
WRENTATC SEPARATION 

6-8 



6.3 DEMAND/DELAY RELATIONSHIPS FOR ASSUMED PRE-1985 ATC 
EQUIPMENT 



As described in detail in Chapter 5 the assessment of future O'Hare per- 
formance presented in this report is predicated upon two basic scenarios judged 
by the taskforce to represent the most probable combinations of ATC equipment 
and airline operations schedule forecast for the pre- 1985 and post-1985 time 
periods. These two scenarios are comprised of Croup 2 ATC equipment/27 per- 
cent heavy fleet mix and Group 4 ATC equipment/45 percent heavy fleet mix for 
pre- 1985 and post- 1985, respectively. Operations were simulated for the pre- 
1985 environment at three levels of maximum hourly scheduled operations (125, 
135 and 150 — see Appendix A) . The results of these experiments at a 27 per- 
cent heavy fleet formed the basis for both VFR and IFR delay curves presented 
in Exhibit 6-4 based upon the optimized pattern of runway use. Employing the 
methodology described in the previous section, point estimates are also indi- 
cated in the exhibit at the 135 operations per hour demand level for both 15 and 
45 percent heavy fleet mixes. 

As was noted in Section 6. 1, failure to account for the non-linear delay 
relationship between configurations and to fully represent all weather conditions 
tends to understate both the "break" in the delay curves and the absolute level 
of average delay incurred. The limited number of simulation experiments avail- 
able to the taskforce did not allow those factors to be taken into account in deter- 
mining the relationships between demand and delay for pre-1985 and post-1985 
ATC environments. Instead, the experimental data was plotted as a range with 
greater uncertainty indicated at higher demand levels. The resulting curves 
show the relative relationships between demand and delay under alternate volume 
assumptions in the pre-1985 ATC and 27 percent fleet mix environment. 

The future relationships shown in Exhibit 6-4 are more complex than those 
presented in the previous exhibits, involving conditions of wake vortex in addi- 
tion to VFR and IFR weather. It is conservatively estimated that the Group 2 
ATC equipment improvements will reduce the IFR separation between aircraft 
which result from wake vortices during 40 percent of the time in the pre-1985 
time period. As was noted in Section 5.3.4, the separations used in the task- 
force evaluation are probably conservative in light of current FAA planning, a 
fact that is particularly true with regard to VFR conditions where no reduction 
in VFR separation was assumed in no wake conditions. The following observa- 
tions may be made from the curves in Exhibit 6-4: 



During the 40 percent of the year when green light conditions 
prevail (no wake vortex in approach "windows") delay at 135 
operations per hour with a 27 percent heavy fleet is estimated 
to average approximately 1 to 2 minutes per operation higher 



6-9 




125 130 135 140 145 

AVERAGE PEAK HOUR DEMAND (operations) 

1/ IFR Vortex 45% Heavy 

2/ IFR Baseline (Vortex) 1975 Historic Runway Use 

3/ IFR No Vortex 45% Heavy 

4/ VFR Baseline (Vortex) 1975 Historic Runway Use 

5/ IFR No Vortex 15% Heavy 

6/ VFR Vortex 6 No Vortex 27% Heavy and 45% Heavy 

7/ VFR Vortex £ No Vortex 15% Heavy 

Note: All data based on optimized runway use, except as noted. 



155 



Delay curve estimated 

from a single point. 



Estimated Region 



O Hare Delay Task force Study 
Chicago O'Hare International Airport 



TITUE: 



DELAY VS DEMAND 
PRE - 1985 ATC 

6-10 



L an dVu m A firpw n 



6-4 



than delays would currently average if an optimized runway 
selection scheme were adopted In VFR and IFR weather. How- 
ever, based on the latest FAA planning, VFR green light delays 
could be expected to be less than those being experienced today. 

Under vortex conditions (60 percent of the time) IFR delays are 
estimated to increase approximately 100 percent higher than those 
during green light conditions at a 135 movement per hour demand. 
Both of these delay levels are considerably higher than those be- 
ing experienced today. 

As was the case in the existing ATC environment, IFR delays 
are estimated to be very sensitive to increases in demand. 



An increase in scheduled demand appears possible at historic levels of de- 
lay during all weather conditions except IFR vortex, where delay penalties re- 
sulting from increased demand will be severe. Conversely, if scheduled demand 
does not increase over today's levels, significant delay savings will be possible 
under an optimized pattern of runway use. 

It is interesting to note that, if scheduled with sufficient concentrations in 
peak hours, increased numbers of heavy aircraft do not necessarily imply in- 
creased levels of delay in VFR and no vortex IFR operating conditions. The reader 
should use caution when interpreting this delay estimate. In general, it would 
be expected that the delays arising from a 45 percent heavy schedule would be 
higher than those from a 27 percent heavy schedule. However, the schedules 
designed by the airlines for use by the taskforce exhibit a pattern of increased 
numbers of heavy aircraft during peak hours. As was seen in Exhibit 5-2, the 
separation between heavy aircraft pairs in the pre-1985 ATC environment is 
the smallest allowable (3 miles) . Therefore, the peak hour interaction between 
heavy aircraft (the percentage of heavy aircraft exceeded 50 percent during peak 
hours in this schedule) at minimum spacing reduced peak hour delay, resulting 
in a reduction in daily delay to a level slightly below that experienced with the 
27 percent heavy schedule during no vortex conditions. During IFR conditions 
when vortices are present in the approach zone, the 45 percent heavy schedule 
results in approximately 36 percent more delay at 135 movements per hour than 
the 27 percent schedule. 



6.4 DEMAND/DELAY RELATIONSHIPS FOR ASSUMED POST-1985 ATC 
EQUIPMENT 



Implementation of Group 4 ATC equipment in the post-1985 time period ap- 
pears to provide the potential for an increased volume of operations at less than to- 
day's delay levels. The relationships between delay and demand for the Group 4 



6-11 



equipment assumptions were developed according to the method described in Sec- 
tion 6.3 and are presented in Exhibit 6-5. Delays in the worst case operating con- 
ditions (predicted to be applicable during only 25 percent of IFR weather) are esti- 
mated to be less than historic levels. The performance of the Croup 4 ATC equip- 
ment is evident in the IFR no vortex estimates, which indicate that these IFR de- 
lays will be less than those during VFR weather in which wake vortex conditions 
exist. This relationship is clearly one heretofore unseen and a direct result of 
improvements offered by the advancement in ATC equipment. 



6.5 FUTURE DELAY COSTS 



The cost of future delays will be heavily dependent upon the volume of air- 
craft operations, the future ATC equipment environment, and the mix of heavy 
aircraft in the fleet. Sections 6. 1 through 6.4 identified present and future re- 
lationships between alternate hourly demand and daily average delay based upon 
optimized use of O'Hare runway configurations. This section extends that anal- 
ysis utilizing the identified demand/delay relationships to develop the annual 
cost of future operations, in constant 1975 dollars, under alternate volume, sep- 
rations and mix assumptions. 

The volume of aircraft operations will have a significant influence on future 
O'Hare delay costs. In the pre- 1985 period, a 27 percent heavy fleet was deter- 
mined most probable with resulting delay costs varying from $20,600,000 to 
$54,000,000. Thus in pre- 1985, a 10 percent increase from the present 135 quota 
volume yields a 46 percent rise in the annual cost of delay while a 10 percent re- 
duction in demand yields a 29 percent savings in annual delay costs. In the post- 
1985 period, a 45 percent heavy fleet was determined most probable yielding delay 
costs varying from $14,400,000 to $28,400,000 with an optimized runway use pat- 
tern. A 10 percent increase in demand from the current 135 hourly operations is 
estimated to result in a 61 percent rise in delay cost while a 10 percent decrease 
in demand is estimated to yield an 18 percent reduction of delay costs in post- 
1985. 

The cost estimates presented in Exhibit 6-6 are based upon an optimized 
runway use pattern. If less efficient runway configurations are utilized, the 
future cost of delay will be increased regardless of demand level and ATC equip- 
ment improvements. 

It is interesting to note that IFR operating conditions account for approxi- 
mately 62 percent of current delay costs although IFR weather occurs only 15 
percent of the year. The impact of ATC equipment improvements on IFR delay 
cost as a percentage of total delay cost is apparent in Exhibit 6-6. For example, 
at a demand of 135 operations per hour in pre- 1985 with a 27 percent heavy fleet, 



6-12 



12 



09 

3 
C 

I 



3 

o 

s 

UJ 

Q. 

s 

UJ 

o 



UJ 

c 



10 



jjRcjsr^i 



us%H*^a 




6 






<H/ 



125 



130 



136 



140 



145 



— ■— 

160 



155 



AVERAGE PEAK HOUR DEMAND (opev e t tone ) 



1/ 

y 

3/ 

!»/ 

5/ 
6/ 



IFR Baseline (Vortex) 1975 Historic Runway Use 
VFR Baseline (Vortex) 1975 Historic Runway Use 
IFR (No Vortex) 27% Heavy 
IFR (No Vortex) 15% Heavy 
VFR (No Vortex) 27% Heavy 
VFR (No Vortex) 15% Heavy 



Note: 



All data baaed on optimized runway use. 



Delay curves 

estimated from 
a single point. 

B Estimated Region 



•<■ » *o r ce Study ? 
'■!»"•': :r*'!Onal Airport 



mur- 



DELAY VS DEMAND 
POST-IMS ATC 

6-13 



L an d rum & . B r o Wl 



TIME 
FRAME 



Percent 

Heavy 

Aircraft 



ATC 



Average 

Peak 
Hourly 
Demand 



ANNUAL 
DELAY 
COSTS A 



ARRIVAL DEPARTURE 



VFR 



IFR 



TOTALS 



VFR 



IF* | VFR 



IFR 



All 

rVeath« 



Hours 



TODAY 



15% 



EXISTING 



137 



Dollars 8.1 



Fuel 



14.3 



17.0 



3.7 



15.3 I 17.9 



32.3 



50.2 



9.7 



1.3 



5.5 9.4 



15.2 



24.6 



13.9 



16.6 



1.5 



6.2 I 15.4 



32.8 



48.2 



Hours 



14.0 



16.5 28.0 



12.8 I 42.0 



29.3 



71.3 



EXISTING 



27% 



PRE- 
1985 



45% 



135 



Dollars 



9.0 



10.6 11.3 



5.2 20.3 



15.8 



36.1 



Fuel 



16.5 



19.4 



Hours 



10.9 



7.3 



125 



Dollars 



Fuel 



GROUP 2 



Hours 



135 



Dollars 



Fuel 



Hours 



150 



Dollars 



7.0 



4.7 



12.8 



8.6 



14.8 



14.4 



9.5 



9.2 



17.4 



16.9 



26.7 



30.2 



17.1 



19.4 



Fuel 



Hours 



195 



Dollars 



Fuel 



31.4 



35.4 



15.3 



15.2 



11.2 



11.1 



19.9 



19.7 



13.0 



5.9 



12.7 



9.5 



5.1 



3.8 



5.9 



4.4 



15.9 



10.1 



6.4 



4.1 



29.5 



25.3 



54.8 



23.6 



16.8 



40.4 



12.1 



8.5 



20.6 



18.7 



13.0 



31.7 



30.7 



24.5 



55.2 



15.9 



13.3 



29.2 



7.4 



4.7 24.8 



21.6 



46.4 



22.2 



21.5 48.9 



51.6 



108.5 



8.9 



8.6 26.0 



28.0 



54.0 



10.3 



10.0 41.7 



45.4 



87.1 



16.8 



12.8 32.1 



27.9 



60.0 



7.5 



5.7 I 18.7 



16.8 



35.5 



8.1 



6.1 I 28.0 



25.8 



53.8 



Hours 



16.8 



24.2 



18.9 



28.0 8 35.8 



48.2 



84.0 



EXISTING 



135 



Dollars 



12.3 



14.8 



8.5 



12.6 I 20.8 



27.4 



48.2 



Fuel 



Hours 



125 



Dollars 



POST- 
1985 



45% 



Fuel 



Hours 



GROUP 4 



135 



Dollars 



Fuel 



Hours 



150 



Dollars 



Fuel 



21.9 



26.3 



9.1 



13.5 31.0 



39.8 



70.8 



6.8 



4.3 



11.2 



2.7 18.0 



7.0 



25.0 



5.0 



3.2 



5.0 



1.2 



8.9 



5.6 



5.4 



1.3 



9.3 



5.2 



11.8 



3.7 



18.8 



4.4 



14.4 



14.3 



6.9 



21.2 



21.1 



6.8 



3.8 



5.3 



1.7 | 12.1 



5.5 



12.0 



6.8 



5.7 



1.8 



12.6 



9.3 



20.7 



6.8 



9.2 



6.8 



9.3 



3.0 



17.7 



8.6 



33.3 



16.1 



18.5 



9.8 



16.4 



12.1 



9.9 



3.3 8 26.3 



15.4 



30.0 



17.6 



26.3 



49.4 



23.3 



41.7 



Note: Delay cost computed for optimized runway use and does not include 
Anomalous Operating Conditions 

A Delay costs are thousands of hours, millions of dollars, and millions 
of gallons of fuel. 



O Hare Delay MsMorce Study 
Chicago O Hare- international Airrjort 



mup 



ANNUAL DELAY COSTS 
OPTIMIZED RUNWAY USE 

6-14 



' L j n d t u m & B'r d w ■ 



45 percent of total delay costs are estimated to be incurred in IFR weather. In 
the post-1985 period at the 135 operations level, IFR delays are estimated to con- 
tribute only 31 percent of total delay costs. The proposed ATC improvements 
clearly have the greatest impact in IFR conditions which have historically been 
most disruptive to O'Hare operations. 

It is possible to infer to a limited degree from the data presented in Exhibit 
6-6 the effect of fleet mix on deS&y cost. Th@ delay costs associated with both 27 
and 45 percent heavy fleet mixes were examined in the pre- 1985 period at a de- 
mand of 135 operations per hour. With the proposed ATC Improvements, delay 
costs are estimated to be $29,200,000 for a 27 percent heavy fleet and $35,500,000 
for a 45 percent heavy fleet. 



«-15 



7. SUMMARY FINDINGS AND RECOMMENDATIONS 



To facilitate formulation of study conclusions and recommendations, it is 
useful to reiterate the study objectives. As defined in Chapter 1, the taskforce 
agreed upon five objectives to guide the analysis of present and future O'Hare 
conditions; these were: 



To determine current capacity and delay levels and to identify 
causes of aircraft delay associated with operations in the 
airspace/airfield and apron/gate systems. 

To determine the potential delay reduction benefits of alterna- 
tive ATC procedural, airport use policy, and facility develop- 
ment options in the current and future periods. 

To determine the potential capacity increase and delay reduc- 
tion benefits of proposed future air traffic control (ATC) sys- 
tem improvements. 

To determine relationships between air traffic demand and de- 
lay in the current and future time periods as an aid to estab- 
lishing acceptable air traffic movement levels. 

To identify areas of potential capacity constraint in the O'Hare 
terminal, groundside and access systems. 



The findings and recommendations relative to each of these objectives are sum- 
marized in the material which follows along with an assessment of their implica- 
tions on the operation, planning, management and development of O'Hare and 
the national air transportation system. While environmental considerations were 
recognized in developing the findings and recommendations, assessment of environ- 
mental considerations was determined by the taskforce to be outside the scope of 
this study. 

The computer simulation techniques employed by the O'Hare taskforce 
are not new. They came into prominence in the early 1960's when they were ] 

used extensively in analysis of cost/benefit trade-offs associated with weapon 
system development. However, notwithstanding their substantial potential for 
illuminating the consequences of alternative system improvement options, they 
have not been used extensively in the analysis of airport system operational and 
developmental decision making. The work of the O'Hare taskforce has demon- 
strated the value of application of sophisticated operations analysis to specific air- 
port problems and future resource allocation decisions. Therefore, it is of para- 
mount importance that the FAA, airlines, and airport operators emphasize the ac- 
quisition of requisite skills in selecting and developing their own people. 



Based upon the conclusions and an assessment of their implementation 
feasibility, an action program for O'Hare has been formulated. Implementation 
of many of the items identified wilt require additional intensive study; some 
actions will require policy decisions, and all will require follow -through by one 
or more of the taskforce participant groups if the full delay reduction benefits 
are to be realized. 



7.1 CURRENT SYSTEM PERFORMANCE 



The taskforce findings related to study Objective 1, determination of cur- 
rent airspace/airfield and apron/gate system capacity and delay levels and 
causes thereof, can be generally described as follows: 



7.1.1 Current Quota Hour Demand of 135 to 145 Operations per Hour 

Is Approaching the Capacity of Many of the Most Frequently 
Used Configurations, Particularly in IFR Weather . 



Current hourly demand at O'Hare is in the area of 135 to 145 
operations per hour during peak periods. This heavy demand is 
imposed upon a facility whose capacity was found to be as follows: 



VFR capacity of O'Hare's runway configurations varies 
from 135 to 172 operations per hour. IFR capacity 
varies from 110 to 146 operations per hour. 

Based upon the historic runway configuration use, 
O'Hare's weighted VFR and IFR capacity average 143 
and 126 operations per hour respectively. 

Current average hourly and daily delays are directly 
related to the capacity of the configuration being uti- 
lized and the prevailing ceiling and visibility condi- 
tions. 



Based upon the way O'Hare has been operated in the past, quota 
hour demand is virtually equal to the airspace/airfield system aver- 
age VFR capacity and exceeds its average IFR capacity by 9 to 19 
operations per hour in IFR weather conditions. 



7-2 



7.1.2 Today's Delay Costs Are High— Approximately $44,000,000 

Annuaily--And Are Sensitive to Many Factors. A Wide 
Range of System improvements Is Needed . 



The study found the following with respect to current O'Hare 
delay. 



Under September 1975 Baseline demand and current 
air traffic separation standards, average delay per 
operation for the configurations used ranged from 2.4 
to 9.6 minutes in VFR weather and from 5.9 to 16.8 
minutes in IFR weather. 

In the most frequently used VFR configurations, peak 
hour delays are 67 percent higher than the daily aver- 
ages. In peak hours, IFR delays are 136 percent 
higher. 

Based upon the historic runway configuration use, de- 
lays under normal operating conditions add $35,900,000 
in direct operating costs to aircraft operators annually. 

Based upon the history of short-term operating anoma- 
lies, delays under abnormal operating conditions add 
$8,300,000 in direct operating costs to aircraft opera- 
tors annually. 

Sixty-seven million gallons of fuel are consumed annu- 
ally as a result of delays at O'Hare. 

The current aircraft delays result in 4,600,000 hours 
of passenger delay and inconvenience annually. 

O'Hare airspace/airfield related aircraft operating de- 
lays are primarily caused by the following factors: 






proximity of other airports to O'Hare 



ATC rules, regulations and procedures 

physical properties of the airspace/airfield 

system 

meteorological conditions 

airfield operating procedures 

characteristics of aircraft operating demand, 

including: 

— arrival/departure ratio 
4 — aircraft mix 

— volume of operations 

— pattern of operations 



7-3 



The consequences of the current situation in terms of cost to the 
aircraft operators and traveling public are high. Costs to the air- 
craft operators are estimated to total $44,000,000 annually, the bulk 
of which ($36,000,000) is sustained as a consequence of day-to-day 
operations in normal conditions. Passenger delay exceeds 4,600,000 
hours annually. The present situation is due to numerous factors, 
none of which are wholly controllable by system users, managers, 
or operators. A thorough understanding of their effect on system 
performance is fundamental in any attempt to determine means to 
enhance the airport's operational efficiency. 



7.1.3 Current Domestic Apron/Gate System Utilization Is Approaching 

the Physical Limits of the Facility. A Major Increase In Gate 
Frontage Will be Required to Accommodate the Pre- 1985 Domes- 
tic Airline Schedule. 



The taskforce findings related to current apron/gate system per- 
formance included: 



The current total gate frontage need is 12,418 linear 
feet. This need is satisfied with the available apron 
frontage of 11,483 feet by use of double parking and 
gate sharing procedures. 

Aircraft operating delays in the apron/gate complex 
average from 1 .4 to 1.7 minutes per operation in typical 
VFR and IFR conditions respectively and are primarily 
a consequence of the facility's physical limitations. 

Under September 1975 Baseline demand and past pat- 
terns of weather occurrence, apron/gate complex de- 
lays are estimated to total $2,700,000 in direct operat- 
ing costs to the domestic air carriers annually. 

The maximum number of inbound holding aircraft ex- 
ceeds the existing penalty box capacity resulting in 
use of the circular taxiway for limited holding oper- 
ations. In addition, the current penalty box does not 
adequately serve Terminal 3 gates because of its lo- 
cation . 



7-4 



While current apron/gate delays appear low relative to the much 
larger airspace/airfield delays, if the aircraft fleet mix change pro- 
jected for the pre-1985 period occurs without facility expansion, the 
deterioration of the existing apron/gate system performance will be 
rapid. The pre-1985 schedule (27 percent heavy aircraft) indicates 
a need for 14,990 linear feet of cumulative domestic carrier gate 
frontage; well in excess of the available 11,483 linear feet. 



7.2 DELAY REDUCTION OPTIONS 



The findings related to evaluating the potential delay reduction benefits 
of alternate ATC procedural, airport use policy, and facility development op- 
tions, clearly indicate there are alternative means to significantly reduce cur- 
rent aircraft delays. These options, if implemented, offer potential for contin- 
ued benefit through the pre-1985 and post- 1985 periods. 



7.2.1 Optimized Selection of O'Hare's Operational Runway Configu- 

rations Can Reduce Current Delay Related Operating Costs 
By $11,000,000 to $16,000,000 Annually . 



Eighteen of O'Hare's currently available configurations were 
analyzed. The five with the least delay characteristics are capable, 
from a meteorological standpoint, of operating the majority of the 
year. Heretofore, they have been operating less than 5 percent an- 
nually, primarily due to airfield restrictions. Recent airfield im- 
provements have removed these restrictions, and current experience 
indicates that the use of these low delay configurations has caused 
a noticeable trend towards decreasing the level of delay. Taskforce 
analyses found the following with respect to ATC procedures. 



The use of configurations with three arrival runways 
offers high potential for inbound aircraft delay savings, 
particularly with judicious management of the arrival 
spacing on the third arrival runway during peak de- 
parture periods in order to expedite departure pro- 
cessing. 

Increased use of O'Hare's most efficient runway con- 
figurations could increase O'Hare's weighted average 
VFR and IFR capacities to 155 and 130 operations per 
hour respectively. 

Increased use of O'Hare's most efficient runway con- 
figurations could result in an aircraft operating de- 
lay cost savings from $11,300,000 to $16,300,000 or 
more annually. 



7-5 



It is clear from the study findings that there exists a need for a 
delay-based operational criteria predicated upon the best possible 
estimates of the delay consequences of operating decisions. While 
a capacity-based criteria such as utilized in the past indicates the 
relative throughput capabilities of various configurations, it does 
not indicate the efficiency with which the throughput is achieved. 
However, no uniform or real time delay data with which to assess the 
consequences of day-to-day operational decisions currently exists. 

Delay is a more effective measure of system operational efficien- 
cy than is capacity. As an example, the taskforce found that while 
the capacities of Configurations 3 and 6 are similar at 145 and 143 
operations per hour, respectively, 1.2 minutes of delay may be 
saved for every operation processed with Configuration 3 as com- 
pared to the delay performance of Configuration 6. In this case as 
in numerous others, the capacity differential between configurations 
does not provide an adequate definition of the efficiency which the 
system processes demand; yet such small incremental differences in 
delay are difficult for the controller to ascertain in operational use. 

Optimized management of the air traffic control system (i.e. , op- 
timized procedures to aid in selection of runway configurations) could 
achieve now, at minimum investment cost, savings comparable to 
those that will be achieved much later at much higher cost when 
third generation ATC hardware is deployed. These observations 
highlight the importance of FAA management exploration of oppor- 
tunities for improved system efficiency by placing emphasis on op- 
timization of operations at least equal to that given development of 
ATC hardware. 



7.2.2 Airport Use Policy Options Have the Potential to Yield Annual 

Delay Related Operating Cost Savings From $2,500,000 to 
$19,000,000 by Altering the Demand/Capacity Relationship . 



Significant delay reduction benefits could be achieved through 
airport use policy adjustments related to the pattern and level of de- 
mand. The airport use policy options examined are summarized in 
the sections which follow. 



7-6 



7.2.2.1 Enforcement of the Current Quota Rule Along With 

Limited Adjustment of Its Procedural Application 
Could Reduce Delay . 



The analysis of current demand found the following 
with regard to the quota rule. 



Allocation of quota hour "slots" for the scheduled 
air carriers are handled by an airline reservation 
committee. There is no formal procedure for allo- 
cation of scheduled air taxi or other operations ex- 
cept the reservation system which operates on a 
first-come-first-served basis. The present quota 
reservation system has no effective procedure for 
monitoring or enforcement. Operations are handled 
with no attempt to verify that the aircraft has the re- 
quired reservation. This regularly results in more 
operations per hour than allowed by the quota. 

Current ATC policy is to handle all demand when 
weather conditions permit and delay is below 15 
minutes. In practice, there currently is no way 
to efficiently determine the delay being incurred 
by aircraft within the system, thus it is difficult 
to adjust demand to operating conditions. 



Acceptance of additional quota hour operations 
when delays are less than 15 minutes should be 
reassessed, recognizing the full cost of these 
added operations. 



In light of the sensitivity of delay to small volume in- 
creases in quota hours, a means to accurately assess system 
delay and to monitor aircraft reservations should be devel- 
oped. 



7.2.2.2 Significant Delay Savings Can Be Realized by De- 

mand Volume and Pattern Changes if They Can Be 
Achieved Without Compromising the Airport's Con- 
necting Function . 



Changes in the volume and pattern of total or sched- 
uled air carrier demand can yield significant delay reduc- 



7-7 



tion benefits. The implications on scheduling of such 
changes were outside the scope of this taskforce and should 
be thoroughly studied before action is taken. The analysis 
of volume and pattern changes found the following: 



A build-up in total airport demand was ob- 
served in the hours directly preceding the 
3PM quota hour. Elimination of this pre- 
quota hour bulge in demand and strict ad- 
herence to the 135 movement level by revi- 
sion, extension, and enforcement of the FAR 
Part 93 "quota rule" could result in aircraft 
operating delay cost savings of $4,000,000 
annually. 

Establishment of a 30 minute quota period 
so as to de-peak hourly demand could re- 
sult in aircraft operating delay cost savings 
of $5,000,000 annually. 

Establishment of an arrival/departure bal- 
ancing quota could result in aircraft oper- 
ating delay cost savings of $2,500,000 annu- 
ally. 

A 10 percent reduction in volume of air carrier 
aircraft demand could result in aircraft oper- 
ating delay cost savings of $10,000,000 an- 
nually. 

Increasing current operations by 10 percent 
could increase delay costs by $19,000,000. 

Elimination of non-scheduled general aviation 
aircraft demand could result in aircraft oper- 
ating delay cost savings of $10,000,000 annu- 
ally. 

A 30 percent reduction of scheduled air car- 
rier peak hour demand, corresponding to a 
21 percent reduction of total demand, could 
result in aircraft operating delay cost sav- 
ings of $19,000,000 annually. 



7-8 



One should bear In mind in Interpreting the benefits 
of adjustment of the O'Hare demand pattern, that while the 
delay reduction benefits look attractive, the costs associ- 
ated with such changes may have far reaching impact on 
national air transportation system efficiency because O'Hare 
serves as a major scheduled air transport connecting com- 
plex (approximately 50 percent of annual enplanements at 
O'Hare are connections) . Thus the high volume and direc- 
tional peaking characteristics of scheduled air carrier de- 
mand at O'Hare, to a great extent, are due to the airport's 
connecting role. 

In view of their broad system implications, use policy 
options including: 



extension of the quota hours, 
arrival/departure balancing quota, 
intrahour quota period, 
scheduled carrier demand reductions in- 
cluding shifts of activity to Midway, and 
quota hour mix adjustments, 



require careful examination of the total system costs prior 
to any implementation action. The City of Chicago and the 
scheduled air carriers serving Chicago should conduct 
further investigations of the costs to each associated with 
major demand pattern changes or shifts of scheduled air 
carrier service. The Federal Government should partici- 
pate in this joint study and initiate a complete review of 
the quota rule as it applies to O'Hare. 



7.2.2.3 Attention to the Phasing, Scheduling and Coordina- 

tion of Airfield Construction Projects Could Reduce 
the Number of Anomalous Operating Days, Offering 
A Potential Annual Savings of $2,000,000 . 



The taskforce found that construction and major main- 
tenance occurring yearly at O'Hare results in increased de- 
lay. Specifically, it was found that: 



7-9 



Construction programs have contributed to 
an average of 20 anomalous operating days 
per year. 

Attention to phasing and scheduling of air- 
field construction could result in aircraft 
operating delay cost savings of $2,000,000 
annually. 



A procedure similar to that used in 1975 should be im- 
plemented to ensure that construction programs are devel- 
oped jointly, well in advance, with full consideration given 
to operational means and construction techniques to mini- 
mize the delay consequences of such actions. 



7.2.3 Several Minor Airport Development Options Were Found To 

Offer Effective Means to Reduce Delay. 



Findings related to airport development actions include: 



A new Runway 22R angled exit would be justified by 
an annual use of 2 to 3 percent; a 12 percent use would 
yield a $750,000 savings annually. Similar benefit 
can be derived from construction of a new angled exit 
on Runway 14L. 

Because inbound aircraft holding in the existing "pen- 
alty box" conflict with T 1 departure queues creating 
a ground control problem during operation of high ca- 
pacity Configurations 4 and 5, relocation of this apron 
would facilitate increased controller use of these de- 
sirable configurations. 

Construction of an additional hold apron to better serve 
the "H" and "K" concourse gates not only would add 
needed arrival hold capacity, but also would reduce 
the need for relocation of the existing penalty box by 
providing a suitable alternate holding area when Con- 
figurations 4 and 5 are in use. 



7-10 



These development options will enhance the configuration se- 
lection options available to the controllers or facilitate the use of 
high capacity/low delay Configuration 4 and triple runway configu- 
rations by reducing controller ground handling difficulties associ- 
ated with operation of such configurations. 



7.2.4 Near-Term Delay Reduction Options Will Continue to Yield 

Significant Savings in the Pre- 1935 and Post- 1985 Periods . 



The taskforce analysis of future delay reduction options focused 
upon the impact of delay optimized configuration selection. The fol- 
lowing table summarizes the findings for the assumed pre- 1985 en- 
vironment (27 percent heavy fleet mix, Group 2 ATC equipment) and 
post-1985 environment (45 percent heavy fleet mix, Group 4 ATC 
equipment) . 



Average Hourly Annual Cost 

Capacity Of Aircraft Delays 

(Operations) (Millions of Dollars) 

Pre- 1985 Post- 1985 Pre-1985 Post- 1985 

Historic Runway Use 141 156 $42.3 $25.9 

Delay Optimized Runway 

Use 152 169 $29.2 $17.6 

Net Benefit of Delay Op- 
timized Runway Use 

Pattern 11 13 $13.1 $ 8.3 



From the findings it can be concluded that optimized runway con- 
figuration selection continues to provide significant capacity and 
delay benefits through the post- 1985 period. Essentially, each of 
the delay reduction actions--ATC procedural, airport use policy, 
and airport development options — found to be beneficial in the cur- 
rent and near-term would continue to provide significant delay re- 
duction benefit regardless of the future ATC equipment environ- 
ment. 



7.3 FUTURE ATC SYSTEM IMPROVEMENTS 



The third study objective was to determine the potential capacity increase 
and delay reduction benefits of proposed future air traffic control system improve- 



7-11 



ments. The study findings related to Objective 3, based upon the taskforce's 
estimates of the most probable future demand and ATC equipment scenarios, in- 
dicate that proposed air traffic improvements have major delay reduction poten- 
tial. 



7.3.1 Implementation of Two Key Elements of FAA's Proposed ATC 

Equipment improvement Program Offers Significant Capacity 
Increase and Delay Reduction Benefits in the Pre- 1985 and 
Post-1985 Periods. Potential Savings Range from $13,000,000 
to $46,700,000 Annually in Future Periods . 



The two elements of the FAA's engineering and development 
program which are foreseen to have a major impact on O'Hare capac- 
ity and delay are: 



Wake vortex advisory/avoidance 

Upgraded ATC automation in the form of automated 

aircraft metering and spacing 



The study findings included the following with regard to O'Hare 
capacity and delay in the assumed pre- 1985 environment (27 per- 
cent heavy fleet mix. Croup 2 ATC equipment) and post- 1985 en- 
vironment (15 percent heavy fleet mix. Croup 4 ATC equipment) . 



Average Hourly 
Capacity 

(Operations) 

Pre-1985 Post-1985 



No ATC Improvements (Do Nothing) 

Historic Runway Use 138 

Optimized Runway Use 149 

Most Probable ATC Equipment 

Improvements 

Historic Runway Use 141 

Optimized Runway Use 152 

Net Benefit of ATC Improvements 

Versus "Do Nothing" 

Historic Runway Use 3 

Optimized Runway Use 3 



130 
140 



156 
169 



26 
29 



Annual Cost 
Of Aircraft Delays 
(Millions of Dollars) 
Pre-1985 Post- 1985 



$69.8 
$42.2 



$42.3 
$29.2 



$27.5 
$13.0 



$72.6 
$48.2 



$25.9 
$17.6 



$46.7 
$30.6 



7-12 



It can be concluded from the foregoing findings that without 
proposed ATC improvements, O'Hare's capacity will continue to 
deteriorate through the post-1985 period and the cost of delay will 
escalate due to the projected increase in heavy jet aircraft. As 
the percentage of heavy aircraft increases, the performance of the 
configuration most widely used in the past will deteriorate signifi- 
cantly. Measured against conditions which will occur if no ATC 
improvements are undertaken, the potential net delay savings of 
the proposed future ATC system elements appear substantial. 

Of concern is the finding that the sizable benefits to be derived 
from the wake vortex advisory/avoidance system with its reduced 
intrail aircraft separations are heavily dependent upon the upgraded 
automation element of the engineering and development program. 
The metering and spacing function appears to be technically complex 
and consequently most vulnerable to implementation schedule slip- 
page. It is imperative that the priority for development and imple- 
mentation of the wake advisory /detection and metering and spacing 
elements of the ATC improvement program be raised to ensure that 
the major benefits of these equipment improvements are realized by 
the system users as quickly as possible. 



7.3.2 The Delay Benefits of Other FAA Engineering and Development 

Program Elements Have Not Been Fully Identified. ASTC Could 
Have Significant Delay Reduction Potential . 



The taskforce review of other engineering and development pro- 
gram elements found that: 



A study by the DOT Transportation System Center 
(TSC) estimates that proposed ASDE-3 equipment will 
limit poor visibility performance loss to 5 percent for 
local controllers and 43 percent for ground controllers \ 
from current levels of 25 percent and 57 percent re- 
spectively. 

The TSC studies indicate that the TAGS system in addi- 
tion to providing discrete aircraft identity to the ground 
controller will reduce voice communication requirements 
and possibly provide local control with airborne cover- 
age near the airport currently lost to the ASR. 



7-13 



The ASTC program appears to the taskforce to offer 
high potential for direct and indirect improvement of 
O'Hare future capacity. ASTC could enhance runway 
configuration selection options in periods of low visi- 
bility. 

An FAA study indicates that area navigation (RNAV) 
could reduce the O'Hare terminal area controllers' 
workload with no corresponding reduction in system 
capacity and might reduce aircraft operating costs by 
$2,000,000 to $5,700,000 annually in a 100 percent 
RNAV environment. 

Installation of microwave landing systems at O'Hare 
has not been studied, but MLS may have potential en- 
vironmental impact reduction, airspace conflict re- 
duction and airfield layout applications. 



The ASTC program providing discrete aircraft identity to the 
ground controller and airborne coverage near the airport appears 
to have potential to enhance runway configuration selection options 
in periods of low ceiling and visibility. Such equipment improve- 
ments will also contribute to a reduction in controller workload. 
Other elements of the FAA engineering and development program, 
while having potential for application in Chicago, have not been 
studied in sufficient detail to determine if they will provide any de- 
lay reduction benefits. 



7.4 DEMAND/DELAY RELATIONSHIPS 



The fourth study objective was to determine the relationships between 
air traffic demand and delay in the current and future time periods as an aid 
to establishing acceptable air traffic movement levels. Future demand/delay 
relationships will be more complex than current ones, consisting of sets of con- 
ditions not only for VFR and IFR weather but also for wake vortex and non-wake 
vortex conditions. The study findings with regard to the relationship of demand 
to delay were as follows: 



If the level of scheduled demand at O'Hare is increased signif- 
icantly, levels of delay greater than today's will be experienced 
without a reduction in separation provided by future ATC equip- 
ment. 



7-14 



As the percentage of heavy aircraft in the fleet increases, levels 
of delay greater than today's will be experienced at the current 
level of scheduled demand, without a reduction in separation 
standards afforded by improved ATC equipment. 

Under Croup 2 ATC equipment assumptions, delays will in- 
crease as a function of the maximum hourly operations sched- 
uled. 

The volume of scheduled aircraft operations will have a signifi- 
cant influence on future O'Hare delay costs; the system perform- 
ance appears less sensitive to fleet mix changes. Annual costs 
are estimated to be as follows: 



Annual Delay Costs (In Millions) 
Optimized Runway Use Pattern 





125 


135 


150 




Operations 


Operations 


Operations 




Per Hour 


Per Hour 


Per Hour 


Pre- 1985 Period 








27 Percent Heavy 


$20.6 


$29.2 


$54.0 


45 Percent Heavy 


— 


$35.5 


— 


Post- 1985 Period 









45 Percent Heavy $14.4 $17.6 $28.4 



Thus the study findings indicate that the existing O'Hare airfield/airspace 
system will be capable of processing increased numbers of passengers through 
the post-1985 planning period. In pre-1985, seat capacity increases appear pos- 
sible through volume increases in VFR weather and additional concentration of 
heavy aircraft during peak demand hours. In the post- 1985 environment, both 
increased volume and heavy aircraft concentrations appear possible at near cur- 
rent delay levels in all weather conditions. 

It should be noted that this future airfield/airspace system potential is 
realizable only if cost effective solutions are found to landside facility constraints 
such as access roadway limitations, vehicular parking restrictions, and inade- 
quate terminal building space and equipment. Serious, concerted airlines/city 
action must be taken to find creative means to eliminate the landside constraints 
and to mitigate the local environmental consequences of O'Hare operations and 
development if these future benefits are to be achieved. Included in the actions 
required, is a clear determination of the future role of Midway Airport in order 
to provide a meaningful basis for resolution of an O'Hare development program. 



7-15 



7.5 RECOMMENDED ACTION PLAN 



The taskforce findings and their broad implications were summarized in 
the previous sections. The results were assessed and consolidated into an action 
plan identifying the option priority, the type of action recommended and the re- 
sponsibility for follow-through. If implemented, the program of actions outlined 
will result in the delay savings described throughout this report. The plan ident- 
ifies four types of action items, described below: 



Imp lemen table Items - Changes or improvements whose benefits 
have been clearly identified and do not necessitate a major poli- 
cy change by any of the study participants. 

Policy items - Changes in procedural or regulatory environ- 
ment requiring major policy changes by one or more study par- 
ticipants. 

Master Plan Study Items - Physical improvements whose delay 
reduction merits must be assessed giving consideration to full 
environmental and economic consequences. 

Air Traffic Control System Items - Improvements whose nature 
requires that they be system-wide in application, necessitating 
further evaluation and/or research and development by the 
Federal Aviation Administration. 



Realization of the potential delay reduction benefits identified in this 
study will require an aggressive program of follow-up and implementation of 
the recommendations enumerated herein. The program will be difficult, espe- 
cially because it will require the full participation and cooperation of the air- 
lines, the ATA, the City of Chicago, and several disparate elements of the FAA 
organization and adequate leadership. 

This is an organizational question and new organizational forms must be 
devised to carry on the work. One such organizational form might be the ap- 
pointment of a standing committee of representatives of the FAA, City of Chicago, 
and appropriate user groups to foster implementation of the study findings. It 
is urgently recommended that the top management of FAA give immediate consid- 
eration to the broad, organizational and operational implications of this study and 
take early steps to formulate the mechanisms for carrying through implementation 
at O'Hare and for its extension to other parts of the system. 



7-16 



The following four sections describe the elements in each item of the action 
plan— the elements are listed in order of recommended implementation priority. 
Immediately following Section 7.5.4, "Air Traffic Control System Items", is Ex- 
hibit 7-1 which indicates the time frame for each item of the action plan along 
with a recommendation for the lead responsibility for follow-through on each item. 
It is stressed that the recommended responsibilities shown in Exhibit 7-1 pro- 
vide identification of the lead-agency in the most appropriate position to initiate 
action on each item; with few exceptions ail groups will be required to actively 
participate in accomplishing each action. 



7.5.1 Implementable Items 



1 . Operate O'Hare International Airport in delay optimal 
configurations employing the lowest delay configura- 
tion possible, given specific conditions of runway avail- 
ability, weather and noise abatement policy. Triple 
arrival and departure runway configurations should con- 
tinue to be used as often as feasible in order to reduce 

2. Strictly enforce the existing FAR 93 quota rule and 
eliminate non-reservation traffic in IFR weather con- 
ditions. 

3. Develop a uniform airline delay reporting procedure 
to provide FAA with data on system performance. 

4. Phase, schedule and fully coordinate airfield construc- 
tion to minimize its impact on delay. 

5. Do not initiate configuration shifts in the 1PM to 8PM 
peak traffic period unless weather or noise abatement 
dictates. 

6. Install centerline lights on Runway 9R/27L. 

7. Construct additional runway exits: 

on Runway 22R between the intersection with 






Runway 9L/27R and the 14L parallel taxiway. 

on Runway 14L between the intersection with 
Runway 18/36 and the intersection with Run- 
way 9L/27R. 






7-17 



8. Determine the location for and construct an addi- 
tional inbound aircraft holding apron to serve air- 
craft in the "H" and "K" concourse area. 

9. Investigate procedures to achieve better interairline 
apron coordination and control of inbound, outbound 
and gate related movements in jointly occupied apron 
cul-de-sacs. 

10. To the extent practical, given ATC constraints, segre- 
gate general aviation and air taxi operations to arrival 
or departure runways which do not interfere with run- 
ways in the primary configuration. 



7.5.2 Policy Items 



1 . Develop and implement a management plan which will 
ensure the operation of the O'Hare airspace/airfield 
system in a delay optimal manner under all conditions 
of weather, runway availability, noise abatement, etc. 
The plan should include a real time system for predict- 
ing, monitoring and evaluating system performance in 
terms of throughput by runway and system delay. 

2. Determine the feasibility of establishing: 

extended quota hours 
intrahour quotas 
arrival/departure quotas 

Also, revise current procedures for accepting VFR ar- 
rivals to the terminal area. The present practice of 
accepting VFR arrivals when delays are approaching 
15 minutes should be discontinued unless they can be 
accommodated on non-interfering runways. Determine 
the impact of including extra sections under the quota. 

3. Since the delay levels increase significantly with de- 
teriorating IFR weather, consideration should be given 
to a two level quota system. Such a quota could provide 
for a higher volume of activity during good weather 
months than during poor weather months. 



7-18 



4. Develop an effective and equitable plan for consolidation 
or cancellation of airline flights during anticipated re- 
duced capacity conditions at O'Hare (e.g., during major 
construction or other anomalous conditions) . 

5. Obtain a waiver to operate arrivals on Runway 14R in- 
dependent of departures on Runways 27L and 9R and ar- 
rivals on 14L independent of departures on Runways 27R 
and 9L during appropriate ceiling/visibility conditions. 

6. Employ quantitative techniques in all future major 
planning and construction work to facilitate optimal 
planning and design. 



7.5.3 Master Plan Items 



1 . Investigate reconfiguration of runway intersections such 
as that between Runways 9R/27L and 32L/14R which con- 
tribute to delays because of wake vortex clearance time 
requirements. 

2. Investigate alternative means to relocate existing penalty 
box to facilitate the use of high capacity low delay con- 
figurations and minimize ground control problems asso- 
ciated with some of O'Hare' s potentially best configura- 
tions. 

3. Investigate means to achieve expansion of existing gate 
capacity. 

4. Investigate alternate terminal facility expansion con- 
sidering relocation of U.S. Air Force, Butler Aviation, 
CaVgo and International Terminal functions. 

5. Consider the construction of maintenance runways (e.g., 
close parallels to existing Runways 14R/32L, 9L/27R and 
4L/22R) . 

6. Consider the construction of independent, exclusive 
use general aviation runways. 

7. Investigate expansion of the inner circular taxiway for 
full use by B-747 aircraft. 



7-19 



8. Define groundside system capacity constraints includ- 
ing airport access roadways. Investigate potential solu- 
tions. 

9. Reassess and fully quantify future O'Hare delay per- 
formance giving consideration to the operating experi- 
ence with the wake vortex advisory system and latest 
separation criteria for the purpose of more definitive 
airport and schedule planning. 



7.5.4 ATC System Items 



1. Take immediate action to utilize the potential reduced 
separation benefits of the wake vortex advisory system 
installed at O'Hare. 

Initiate an air traffic simulation study of opera- 
tional procedures for utilizing reduced separa- 
tions. These procedures should include chang- 
ing separation standards both from the existing 
separations to reduced separations under no 
vortex conditions and also going from the no 
vortex to vortex separations. This simulation 
should be designed to form the basis of recom- 
mended operating procedures and should be ac- 
complished prior to completion of the present 
test phase. 

Initiate a study to identify the environmental im- 
pact of reduced separations so that operational 
implementation is not delayed. 

Implement reduced separations under known 
safe conditions as defined in previous testing 
programs. 

Identify and program funds to modify and ex- 
tend the WVAS test equipment to allow for op- 
erational use. 

2. Proceed with highest priority on the development and 
installation of wake vortex and metering and spacing 
equipment. Reassess the timetable of other program 
elements if necessary to give highest priority to wake 
vortex and metering and spacing programs. 



7-20 



Conduct an airspace analysis to determine the inter- 
actions between O'Hare, Midway and other Chicago 
area airports. 

Refine the procedures for controlling traffic flow into 
the O'Hare terminal system under conditions of anom- 
alous demand. 

Investigate the feasibility of a management information 
system for the O'Hare ATC personnel which would link 
the ARTS III system to the real time system for monitor- 
ing and controlling system performance. 

Increase the development effort for the ASTC program 
including ASDE and TAGS which appears to offer the 
potential for increasing 'Hare's IFR capacity and re- 
ducing delay through enhanced configuration selection 
opportunities. 



7-21 



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NATIONAL TECHNICAL INFORMATION SERVICE 




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