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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/delaytaskforcest03ohar 



U.S. DEPARTMENT OF COMMERCE 
National Technical Information Service 



AD/A-030 305 



O'HARE DELAY TASK FORCE STUDY, VOLUME III: 
TECHNICAL APPENDICES 



JULY 1976 



TRANSPORTATION LIBRARY 

MAY I 2 1978 
NORTHWESTERN UNIVERSITY 






tRAN 



TRGN 

HE 7 

9797. 7C4r- 

U58o 

v. 3 




FAA-AGL-76-1, III 



3 5556 022 309 546 



© ; 

CO 



O'HARE DELAY TASK FORCE STUDY 

VOLUME 3 TECHNICAL APPENDICES 

CHICAGO O'HARE INTERNATIONAL AIRPORT 



CO 

O 



i sj ' T »^ 







July, 1976 



Document is available to the public through the 

National Technical Information Service, 

Springfield, Virginia 22151 



Prepared by the joint effort of: 

FEDERAL AVIATION ADMINISTRATION 

CITY OF CHICAGO-DEPARTMENT OF AVIATION 

THE AIRLINES SERVING O'HARE 



REPRODUCED BY 

NATIONAL TECHNICAL 
INFORMATION SERVICE 

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



4Gt« 



'spoh 



k ^fi/^ et , 



U52 



v 



.3 



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. 



T 



Technical Report Documentation ~gge 



V. Report No. 

FAA-AGL-76-1, III 



2. Government Accession No. 




Vtorming Orgomzotion Code 



O'Hare Delay Task Force Study. Volume 3 „ s. r.>p.n 9U . f on 

l ' , , ..,,, — ■.,4*»-'P»t>'»rminn Organ 



ffl Federal AViaUoft^aminist ration, Chicago 

VK3 Department of Aviation, Airlines Serving O'Hare 



9. Performing Organization Nome and Address 



/fuj ^l^kltizMz 3 . 



12. Sponsoring Agency Name and Address 

Federal Aviation Administration 

Great Lakes Region 

2300 E. Devon Avenue 

Des Plaines, Illinois fgOOlg 



15. Supplementary Notes 




16. Abstroct 

This joint FAA/City of Chicago/airUne study of air *%?£?£%%?££„ 
toternationa! Airport is presented I in three volumes ^^™^ e ° the 
summary of the study findings and recommendations Jhe second and 

reSc^^^ 

tain data and explanatory materials. 

* • f -ff,> Hp1*v at Chicago O'Hare International Airport, its causes and 

system. 




17. Key Words 

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



18 Distribution Stotement 

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



19. Secur.ty Clossil. (of this report) 

unclassified 



20. Secur.ty Class. f. (of this page) 

unclassified j ft. 



Form DOT F 1700.7 (8-72) 



Reproduction of completed poge authorized 

* a w / 




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 December 1974 through June 1976. During 
this time several of the delay reduction concepts identified by the taskforce have 
been tested and implemented by the study sponsors with results which appear to 
parallel those identified in the taskforce evaluations, lending additional cred- 
ence to the validity of the directions identified. 

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



Volume 1 - Management 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 



AIRLINES 



Arras, William F. 

Hottman, Ralph C. 
Hubbard, Herbert B 

McLean, George D. 

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



Airport Manager, O'Hare 

Operations Supervisor, O'Hare 

Project Manager 

Assistant to the Commissioner 

Chief of Planning 

Project Manager 



Senior Consultant 
Vice President 



Manager, Airfield Operations 

Planning 

Regional Director 

Director Operations Research 

& Development 

Director, Operational 

Engineering 

Project Leader 

Director Airport Planning 

Director Operational S Advance 

Engineering 



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



Landrum & Brown 
Landrum £ Brown 



United Airlines 

ATA Chicago 
United Airlines 

American Airlines 

United Airlines 
American Airlines 
Continental Airlines 



FAA/ATA WASHINGTON WORKING GROUP 



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

Poritzky, Sigbert 

FAA Consultants : 

Hockaday, Steve 
Sinha, Agam N . 

Taskforce Chairman 
Group Chairmen 



Program Manager ATF-4 

Program Manager AEM- 100 

Vice President, Regional 

Operations 

Director, NAS System Engineering 



Senior Consultant 
Member of Technical Staff 



FAA 
FAA 
ATA 

ATA 



PMM&Co. 
MITRE Corp. 



I! 



TABLE OF CONTENTS 

O'HARE DELAY TASKFORCE STUDY 
VOLUME 3 - TECHNICAL APPENDICES 



PREFACE 

TABLE OF CONTENTS 



Page 



I 
Hi 



APPENDIX A 

1 . FAA Capacity Model Input Parameters 

2. "AIRSIM" Model Input Parameters 

3. Consolidated Listing of Results 

APPENDIX B - AN OVERVIEW OF "AIRSIM" 

1 . Background 

2. Model Development Objectives 

3. Conceptual Design of "AIRSIM" 

4. "AIRSIM" Software Description 

5. "AIRSIM" Validation 



A-1 

A-11 

A-24 



B-l 

B-2 

B-3 

B-25 

B-26 



APPENDIX C - AN OVERVIEW OF "CATESIM" 

1 . Background 

2. Model Development Objectives 

3. "CATESIM" Conceptual Description 

4. "CATESIM" Program Description 

5. "CATESIM" Validation 



C-1 

C-2 

C-3 

C-17 

C-22 



APPENDIX D - FAA RUNWAY CAPACITY MODEL 

1 . Background 

2. Objectives 

3. Model Concepts 

4. Software Description 

5. Validation 



D-1 
D-2 
D-3 
D-6 
D-8 



APPENDIX E - IMPACT OF SHORT-TERM CAPACITY REDUCTIONS 

1 . Background E-1 

2. Traffic Movement Demand at O'Hare E-2 

3. Effect of Reduction in Capacity for One Hour E-3 

4. Effect of Reduction in Capacity for Several Hours E-4 

5. Cumulative Traffic Movement Demand at O'Hare E-5 

6. Impact of 3-Hour Reduction in Capacity E-6 

7. Potential Backioq Queues and Total Delay Hours E-8 

8. Average Delay Costs and Fuel Consumption Rates E-8 

9. Imbalance Between Airport Movement Capacity and Demand E-9 
10. Conclusions E-10 



APPENDIX F - CAPACITY IMPACT OF FAA ENGINEERING AND DEVELOPMENT 
ELEMENTS 

1. Introduction F-1 

2. E&D Elements Impacting Operations atO'Hare F-1 

3. Methodology of Assessing the Impact of E&D Elements F-1 1 

4. Potential Capacity Impact of WVAS, Upgraded Automation 

and DABS F-19 

5. Potential Impact of ASTC, RNAV and MLS F-24 



IV 



I 



APPENDIX A 

MODEL INPUTS AND CONSOLIDATED 
EXPERIMENT RESULTS 



Prepared for: 
The Chicago Delay Taskforce 

Prepared by: 

Land rum & Brown 
Airport Consultants 



t-l 



APPENDIX A 
MODEL INPUTS AND CONSOLIDATED EXPERIMENT RESULTS 



The purpose of Appendix A is to present the input parameters employed 
in all FAA capacity model and City of Chicago/Landrum S Brown AIRSIM model 
experiments conducted by the taskforce along with a consolidated listing of the 
results from experiments. The appendix is divided into three sections: 



FAA Capacity Model Input Parameters 
AIRSIM Model Input Parameters 
Consolidated Listing of Results 



For detailed explanations of the interpretation and use of all input data, Appen- 
dices B and D should be referred to. 



1. FAA CAPACITY MODEL INPUT PARAMETERS 



Inputs to the capacity model were specified by the Chicago O'Hare delay 
taskforce. They were drawn from observed data collected (separately) by the 
Federal Aviation Administration and Landrum & Brown during 1973 augmented 
with observations of current operations, projected future airline schedules, and 
air traffic control personnel. 

Exhibit A-1 defines the runway use configurations employed in the base- 
line capacity analyses (except for Configuration 18 which was omitted) . Con- 
figurations 1, 3, 4, 6, 13 and 16 were also analyzed to determine the potential 
improvements resulting from future air traffic control automation. These run- 
way use configurations were selected to include the most utilized combinations 
of runways. Configurations providing three arrival or three departure runways 
were explored as near term possibilities for reducing delay. Other exhibits de- 
scribing input to the FAA capacity model are briefly described below. 



Exhibit A-2 defines the parameter inputs used to generate 
the baseline Capacity /p> analyses. 

Exhibit A-3 defines the parameter inputs used to generate 
the Capacity fpj analyses for a pre-1985 (Croup 2) and post- 
1985 (Group 4) ATC environment. 

Exhibit A-4 defines the standard deviations used in the 



Capacity /pj analyses. 



(\IP 





Note: 

See Exhibit 2-"6 

for runway I?yqv1 





10 




13 





.x' 






7< 







8 




11 






•jrtarie Delay Taskforcelsibdy^ 
Chicago O'Hare International Airport 












12 





18 




JTITLI: RUNWAY 

CONFIGURATIONS Kn 
EXAMINED 









L and r u m A Brown 

Alf»PO*»T CONSULTANTS 



\-2 




O'Hare Delay Taskforce Stifdy 
Chicago O'Har. International! Airport 



FAA CAPACITY 
MODEL INPUTS 



Administration 



A- 3 



ARRIVAL RUNWAY OCCUPANCY TIMES (seconds) 


Arrival 
Runway 


Aircraft Class 


A,B 


C 


D 


4L 

4R 


47 
52 


51 
58 


57 
68 


9L 
9R 


46 
54 


54 
47 


60 
54 


14L 
14R 


49 
42 


52 
52 


57 
58 


22L 
22R 


52 
46 


52 
63 


58 
64 


27L 
27R 


47 
43 


53 
52 


64 
59 


32L 
32R 


41 
44 


54 
50 


61 
57 



6' Ha re Delay Taskforce Study 
Chicago O'Hare International Airport 



TITLl: 



FAA CAPACITY 
MODEL INPUTS 

A-4 



SOURCE 

Federal Aviation 
Administration 



ICXHMMT: 

A-2 




Turnni ' »■■». separates csec^T 



Lead B 
Aircraft 
Class C 



50 50 50 50 

50 50 50 50 

55 55 50 50 

U0 120 120 105 



Lead B 
Aircraft 
Class C 



60 60 60 60 

60 60 60 60 

60 60 60 60 

D 120 120 120 105 



o ware Delay Tasktorce Study 
C^agdOHare WernaUona. A.rpoM 



FAA CAPACITY 
MODEL INPUTS 



A-5 



Federal Ayia 
Administrati 



(A 

"O 

c 
o 
o 

0) 

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z 
o 

5 
IX 

UJ 

oc 

3 

oc 

£ 

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$ 

oc 
oc 
< 


Arrival /Departure 

Separations (seconds) 

Aircraft Class 


Q 


m 


cn 

po 


o 




en 


cn 


cn 
po 


cn 

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in 
in 


m 


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PM 






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3 
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£ 

UJ 

a 


Departure/Arrival 
Separations (n. miles) 


oc 


PM 


PM 


PM 


PM 


PM 

i 


PM 
* 


PM 


PM 


PM 


PM 


PM 


PM 


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PM 


PM 


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PM 


PM 


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UL 

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CC 


Arrival 
Runway 


-J 

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-1 


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cn 


-J 


-1 


a: 

PM 
PM 


OC 

ST 


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ST 


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PM 
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PM 
PM 


PM 


cc 

PM 
PM 


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PM 


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PM 


CC 
PM 
PM 


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PM 
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Departure 
Runway 


-J 

•3- 




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cn 






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PM 
PM 




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r- 

PM 






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P» 
PM 


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PM 
PO 


CC 

PM 
PO 







'#-•' 



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



ITITUE: 



FAA CAPACITY 
MODEL INPUTS 

A-6 



SOURCE 

Federal Aviation 
Administration, 



lEXMMT: 

A-2 



Percent Arrivals: 50% 








1 


Aircraft Mix: Pre-1985 (Croup 2) 




Aircraft 


Class 


JL | 


A 


B 


C 


Configurations 3, 4, 13, 16 










Arrivals 


3.1 


1.5 


70.8 


24.6 


Departures 


11.4 


2.9 


60.0 


25.7 


Configuration 1 (with segregation of heavy 










departures from south half of field) 








] 


Arrivals 


3.1 


1.5 


70.8 


24.6 1 


Departures - North runways 


— 


— 


48.6 


51.4 


- South runways 


22.9 


; 7 


71.4 


— 

< 


Configuration 14 










Arrivals/Departures 


7.4 


2.2 


65.2 


25.2 | 


Aircraft Mix: Post-1985 (Croup 4) 










Configurations 3, 4, 13, 16 








, 


Arrivals 


1.5 


1.5 


46.2 


50 . 8 


Departures 


10.0 


2.9 


41.4 


45.7 


Configuration 1 (with segregation of heavy 








. 


departures from south half of field) 








1 


Arrivals 


1.5 


1.5 


46.2 


50.8 


Departures - North runways 


-- 


-- 


8.6 


91.4 \ 


- South runways 


20.0 


5.7 


74.3 


. "' [ 


Configuration 14 








[ 


Arrivals/Departures 


5.9 


2.2 


43.7 


48.2 | 



O'Har© Delay Taskforce, Study 
Chicago O'Hare International Airport 



FAA CAPACITY MODEL INPUTS 
FUTURE ATC RUNS 



SOURCE y 

Federal. Aviation 
Administration; 



lEXMterr i 



A-7 



ARRIVAL /ARRIVAL SEPARATIONS (nautical miles) 
TODAY AND GROUP 2 FALL BACK (vortex present) 


VFR 


IFR 


Trail Aircraft Class 


Trail Aircraft Class 


A B C D 


A B C D 


A 1.9 1.9 1.9 1.9 

Lead B 2 .7 1.9 1.9 1.9 
Aircraft 

Class c 2.7 1.9 1.9 1.9 
D 4.5 3.6 3.6 2.7 


A 3.0 3.0 3.0 3.0 

Lead B 4.0 3.0 3.0 3.0 

Aircraft 

Class C 4.0 3.0 3.0 3.0 

D 6.0 5.0 5.0 4.0 



1 — 

GROUP 2 AND GROUP 4 FALL BACK (vortex present) 


VFR 


IFR 


Trail Aircraft Class 


Trail Aircraft Class 


A B C D 


A B C D 


A 1.9 1.9 1.9 1.9 

Lead B 2.7 1.9 1.9 1.9 

Aircraft 

Class C 2.7 1.9 1.9 1.9 

D 4.5 3.6 3.6 2.7 


A 3.0 3.0 3.0 3.0 

Lead B 3.5 3.0 3.0 3.0 

Aircraft 

Class C 3.5 3.0 3.0 3.0 

D 5.0 4.0 4.0 3.0 



GROUP 4 


VFR 


IFR 


Trail Aircraft Class 


Trail Aircraft Class 


A B C D 


A B C D 


A 1.9 1.9 1.9 1.9 

Lead B 2.1 1.9 1.9 1.9 

Aircraft 

Class C 2.1 1.9 1.9 1.9 

D 3.4 2.7 2.7 2.1 


A 2.0 2.0 2.0 2.0 

Lead B 2.4 2.0 2.0 2.0 

Aircraft 

ClaiS C 2.4 2.0 2.0 2.0 

D 3.7 3.0 3.0 2.3 



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



Ffifik CAPACITY MODEL INPUTS 
FUTURE ATC RUNS 



SOURCE 

Federal Aviation 
Administration 



EXHHMT: 

A-3 



A-8 



as a ^zBiSj m wmjm 



DEPARTURE/ DEPARTURE SEPARATIONS 


i 

(seconds) \ 




TODAY 










VFR/IFR 




Trai 


1 Aire 


:raft Class 


A 


B 


C 


D 




A 60 


60 


60 


60 


Lead 


B 60 


60 


60 


60 


Aircraft 










Class 


C 60 


60 


60 


60 




D 120 


120 


120 


90 







GROUP 2 






1 










VFR/IFR 








Trai 


1 Aircraft CI 


ass 


[ 


A 




B 


C 




D 




A 


60 




60 


60 




60 


Lead 


B 


60 




60 


60 




60 


Aircraft 














i 


Class 


C 


60 




60 


60 




60 




D 


90 




90 


90 




60 



GROUP 4 










VFR/IFR 








Trai 


1 Aircre 


ift CI 


ass 




A 




B 


C 




D 




A 


60 




60 


60 




60 


Lead 


B 


60 




60 


60 




60 


Aircraft 
















Class 


C 


60 




60 


60 




60 




D 


60 




60 


60 




60 



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



I TITLE: 

|FAA CAPACITY MODEL INPUTSJ 
FUTURE ATC RUNS 



SSHI38T: 



Federal Aviatio. 
Administration 



A-9 





BASELINE ATC 


FUTURE ATC 




VFR 


IFR 


TODAY 


GROUP 2 


GROUP 4 


AR 


6.0 


6.0 


6.0 


6.0 


6.0 


DR 


8.0 


8.0 


8.0 


8.0 


8.0 


AA 


18.0 


15.0 


15.0 


11.0 


8.0 






PROBABILITY OF VIOLATION 








PRESENT ATC 


.04 






GROUP 2 ATC 


.01 






GROUP 4 ATC 


.01 





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



TITLE: 



FAA CAPACITY MODEL 
STANDARD DEVIATIONS 

A 1 



'SOURCE 

Federal Aviation 
Administration 



The arrival and departure aircraft mixes were developed from existing 
and proposed future Official Airline Guides (OAC) with general aviation (s:k1 
non-scheduled) aircraft added. For 1975, pre-1985, and post-1985 environ- 
ments, an hourly mix containing 53 percent heavy jet aircraft was selected. 
Because of the scheduling practices inherent in the Official Airline Guide 
(OAG), the hourly arrival and departure mixes for these time periods were 
not exactly equal . 



AIRSIM MODEL INPUT PARAMETERS 



Inputs to the AIRSIM model were based on data collected by Landrum & 
Brown and the City of Chicago, Department of Aviation during 1973. AS! in- 
puts were reviewed and approved by the taskforce. The 1973 data base was 
supplemented, as necessary, with data collected in the fall of 1975 in the 
O'Hare tower cab and the Terminal Radar Approach Control (TRACON) facil- 
ity. The input data presented in this section are not intended to be ail inclu- 
sive, as much of the data base required by AIRSIM is related to the physical 
features of the airfield, such as runway lengths, exit locations, etc. This 
information was taken directly from the airport layout plan which was depicted 
in Chapter 2. Input data to the AIRSIM model are presented in the exhibits im- 
mediately following. These exhibits are briefly described below. 



Exhibit A-5 : AIRSIM Model Aircraft Classification 
Codes 

Exhibits A-6 and A-7 : Operations contained in the January 
1975, September 1975, pre-1985 and post-1985 AIRSIM sched- 
ules. Note that these schedules are coded (J1, SI, etc.) and 
may be cross referenced to the experiment design matrix pre- 
sented in Exhibit A-15. 

Exhibits A-8 and A-9 : Fleet mixes contained in the January 
1975, September 1975, pre-1985 and post-1985 AIRSIM sched- 
ules. 

Exhibit A-10 : Mean arrival/arrival separations. 

Exhibit A-11 : Standard deviations for arrival/arrival 
separations. 

Exhibit A-12 : Departure/departure separations and 
intersection wake separations. 

Exhibit A-13 ; Flight path distances. 

Exhibit A-14: Departure/arrival separations. 



A-11 

















AIRCRAFT DESCRIPTION 


AIRSIM 
Code 


FAA 
Model 
Code 


ATC 
Classification B 




4 Engine Turbojet 


1 


c 


Large 


H Engine Turbofan v 


2 


c 


Large 


3 Engine Turbofan 


3 


c 


Large 


3 Engine "Stretch" Turbofan 


4 


c 


Large^ 


-~^2 Engine Turbofan 


5 


c 


Large 


4 Engine HBPR Turbofan 


6 


b~ 


Heavy 


3 Engine HBPR Turbofan \ 


7 





Heavy 


SST 


8 


N/A* 


N/A # 


General Aviation Jet 


9 


C 


Large 






H Engine Propeller 


10 


C 


Large 


2 Engine Propeller, Greater than 12,500# 


11 


B 


Large 


2 Engine Propeller, Less Than or equal 
12,500# 


12 


A 


Small 


1 Engine Propeller 


13 


A 


Small 


4 Engine Turbofan 


it 




Heavy 








■ As used in AIRSIM. 
• Not Applicable. 





O'Ware Delay Taskforce Study 
Chicago OHare International Airport 


title AIRSIM AND FAA MODEL 
AIRCRAFT CLASSIFICATION 

CODES 


^SOURCE v 

Landrum & Brown 

AWPORT CONSULTANTS 


EXHWIT: 

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



cllRRENT AIRSIM SCHEDULES 
(VOLUME) 

A-13 



,SOURCE . 

LafldrurttcV Brown 

AIWPOBT CONSUCrAHTS 



EXHIBIT: 





Schedule S4 




Schedule S5 






Baseline SI With 




Baseline Si With 






Balanced Hourly 




Hourly Operations 






Arrivals and Departures 


Limited to 135 




Time 


Arrivals Departures 


Total 


Arrivals Departures 


Totals 


8- 9AM 


58 58 


116 


57 59 


116 


9-10 


62 61 


123 


62 61 


123 


10-11 


64 64 


128 


59 69 


128 


11-12 


58 59 


117 


57 60 


117 


12- 1PM 


64 64 


128 


66 62 


128 


1- 2 


72 71 


143 


68 67 


135 


2- 3 


67 68 


135 


66 69 


135 


3- 4 


72 72 


144 


67 68 


135 


4- 5 


70 71 


141 


69 66 


135 


5- 6 


70 71 


141 


69 66 


135 


6- 7 


68 69 


137 


60 75 


135 


7- 8 


69 69 


138 


69 66 


135 


Total 


794 797 


1,591 


769 788 


1,557 





Schedule S6 












Baseline SI with 


21% 




Schedule S7 






Volume Reduction 


(21% 




Baseline SI with 






of Baseline Operations) 


General Aviation Removed 


Time 


Arrivals Departures 


Total 


Arriva 


s Departures 


Total 


8 - 9 AM 


44 42 


86 


55 


57 


112 


9 -10 


46 48 


94 


58 


58 


116 


10-11 


44 50 


94 


55 


67 


122 


11-12 


52 47 


99 


53 


56 


109 


12- 1 PM 


50 57 


107 


61 


54 


115 


1 - 2 


60 49 


109 


68 


66 


134 


2-3 


48 55 


103 


61 


62 


123 


3-4 


52 56 


108 


62 


68 


130 


4-5 


58 50 


108 


68 


59 


127 


5-6 


63 52 


115 


67 


61 


128 


6-7 


48 64 


112 


56 


72 


128 


7-8 


65 51 


116 


68 


62 


130 


TOTAL 


630 621 


1,251 


732 


742 


1,474 



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



TITLE: 



CURRENT AIRSlRfi SCHEDULES! 
(VOLUME) 

A 14 



Landrum 4V Brown 

AIHPWT CONSULTANTS: 



lEXNIMT: | 

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> O'Hare Delay Tasfcforce Study 
Chicago O'Hare International Airport 



I TIT 



PutURE AIRSIM SCHEDULES 
(VOLUME) 



lIXtiOKT: 



llahdrum & Brown 

i" AIRPORT CONSULTANT! 



JANUARY, 1975 








Schedule . 


J2 


Schedule J3 








Baseline J1 with Quota 


Baseline J 1 with Quota 




Schedule 


J1 


Period Adjusted to 


Period Adjusted to 




January 1975 Baseline 


30 Minutes 


15 Minutes 


Aircraft 


Operations 


% of 


Operations 


% of 


Operations 


% of 


Type 


Scheduled 


Total 


Scheduled 


Total 


Scheduled 


Total 


1 


6 


.4 


6 


.4 


6 


.4 


2 


182 


11.5 


182 


11.5 


182 


11.5 


3 


301 


19.0 


301 


19.0 


301 


19.0 


4 


263 


16.6 


263 


16.6 


263 


16.6 


5 


301 


19.0 


301 


19.0 


301 


19.0 


6 


39 


2.4 


39 


2.4 


39 


2.4 


7 


114 


7.2 


114 


7.2 


114 


7.2 


8 





0.0 





0.0 





0.0 


9 


35 


2.2 


35 


2.2 


35 


2.2 


10 


7 


0.4 


7 


0.4 


7 


0.4 


11 


121 


7.6 


121 


7.6 


121 


7.6 


12 


193 


12.1 


193 


12.1 


193 


12.1 


13 


26 


1.6 


26 


1.6 


26 


1.6 


14 





0.0 





0.0 





0.0 


Total 


1,588 


100.0 


1,588 


100.0 


1,588 


1 00 . 



SEPTEMBER, 1975 










Schedule S3 








Schedule S2 


Baseline SI with 




Schedule SI 


Baseline Si with 10% 


10% Greater 




September 1975 Baseline 


Fewer Carrier Operations 


Air Carrier Operations 


Aircraft 


Operations 


% of 


Operations 


% of 


Operations 


% of 


Type 


Scheduled 


Total 


Scheduled 


Total 


Scheduled 


Total 


1 





0.0 





0.0 





0.0 


2 


138 


8.7 


126 


8.6 


151 


8.8 


3 


279 


17.5 


249 


17.1 


306 


17.8 


4 


310 


19.5 


285 


19.5 


340 


19.8 


5 


293 


18.4 


263 


18.0 


320 


18.6 


6 


31 


2.0 


30 


2.0 


31 


1.8 


7 


136 


8.5 


127 


8.7 


156 


9.1 


8 





0.0 





0.0 





0.0 


9 


32 


2.0 


32 


2.2 


32 


1.8 


10 





0.0 





0.0 





0.0 


11 


103 


6.5 


96 


6.6 


115 


6.7 


12 


204 


12.8 


196 


13.4 


204 


11.8 


13 





0.0 





0.0 





0.0 


14 


65 


4.1 


57 


3.9 


65 


3.8 


Total 


1,591 


100.0 


1,461 


100.0 


1,720 


100.0 



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



TITLE: 



ICURRENT AIRSIM SCHEDULES! 
IFLEET MIX; 

A 16 



Landrum & Brown! 

;: AIRPORT CONSULTANTS 





Sched 


ule S4 


Schedule S5 




Baseline Si with 


Baseline Si with 




Balanced Hourly Arrivals 


Hourly Operations | 




and Dep 


•artures 


Limited to 135 


Aircraft 


Operations 


% of 


Operations % of ! 


Type 


Scheduled 


Total 


Scheduled Total 


1 


1 


0.1 


0.0 


2 


137 


8.6 


138 8 


.9 


3 


279 


17.5 


279 17 


.9 


4 


310 


19.5 


310 19 


.9 


5 


293 


18.4 


293 18 


.8 


6 


31 


2.0 


31 2 





7 


136 


8.5 


136 8 


7 


8 





0.0 








9 


32 


2.0 


26 1 


7 


10 





0.0 


0. 





11 


103 


6.5 


100 6 


4 


12 


204 


12.8 


180 11. 


6 


13 





0.0 


0. 





14 
Total 


65 
1,591 


4.1 
100.0 


64 4. 


1 


1,557 100.0 j 





Schedule S6 




1 




Baseline SI with 21% 


Schedule 


S7 




Volume Reduction (21% 


Baseline SI i 


with General 




of Baseline Operations) 


Aviation Removed 


Aircraft 


Operations 


% of 


Operations 


% of 


Type 


Scheduled 


Total 


Scheduled 


Total 


1 





0.0 





"g 

0.0 


2 


138 


11.0 


138 


9.4 


3 


279 


22.3 


279 


18.9 


4 


139 


11.1 


310 


21.0 


5 


124 


9.9 


293 


19.9 


6 


31 


2.5 


31 


2.1 


7 


136 


10.9 


136 


9.2 


8 





0.0 





0.0 


9 


32 


2.6 





0.0 


10 





0.0 





0.0 


11 


103 


8.2 


89 


6.1 


12 


204 


16.3 


133 


9.0 


13 





0.0 





0.0 


14 


65 


5.2 


65 


4.4 


Total 


1,251 


100.0 


1,474 


100.0 j 



i 0,'Hare Delay Taskforce Study - 
C h icago O'Ha re Inter national Ai rpor t 



TITLE: 

(current AIRSIM SCHEDULES! 
(FLEET MIX) 




A 1 



PRE -1985 






Schedule F1 


Schedule 


F2 


Schedule F3 




115 Maximum Hourly 


105 Maximum Hourly 


130 Maximum Hourly 




Air Carrier 


Operations 


Air Carrier Operations 


Air Carrier Operations 


Aircraft 


Operations 


% of 


Operations 


% of 


Operations 


% of 


Type 


Scheduled 


Total 


Scheduled 


Total 


Scheduled 


Total 


1 





0.0 





0.0 





0.0 


2 





0.0 





0.0 





0.0 


3 





0.0 





0.0 





0.0 


4 


1,042 


64.4 


961 


64.2 


1,148 


65.0 


5 





0.0 





0.0 





0.0 


6 





0.0 





0.0 





0.0 


7 


384 


23.8 


345 


23.0 


405 


22.9 


8 





0.0 





0.0 





0.0 


9 


63 


3.9 


63 


4.2 


71 


4.0 


10 





0.0 





0.0 





0.0 


11 


34 


2.1 


34 


2.3 


36 


2.1 


12 


91 


5.6 


91 


6.1 


103 


5.8 


13 


3 


0.2 


3 


0.2 


3 


0.2 


14 





0.0 





0.0 





0.0 


Total 


1,617 


100.0 


1,497 


100.0 


1,766 


100.0 



POST -1985 




Schedu 


le F4 


Schedule F5 


Schedule F6 




115 Maximum Hourly 


105 Maximum Hourly 


130 Maximum Hourly 




Air Carrier 


Operations 


Air Carrier Operations 


Air Carrier Operations 


Aircraft 


Operations 


% of 


Operations 


% of 


Operations 


% of 


Type 


Scheduled 


Total 


Scheduled 


Total 


Scheduled 


Total 


1 





0.0 





0.0 





0.0 


2 





0.0 





0.0 





0.0 


3 





0.0 





0.0 





0.0 


4 


758 


46.9 


706 


47.2 


867 


48.2 


5 





0.0 





0.0 





0.0 


6 





0.0 





0.0 





0.0 


7 


667 


41.2 


599 


40.0 


738 


41.1 


8 





0.0 





0.0 





0.0 


9 


81 


5.0 


81 


5.4 


81 


4.5 


10 





0.0 





0.0 





0.0 


11 


43 


2.7 


43 


2.9 


43 


2.4 


12 


60 


3.7 


60 


4.0 


60 


3.3 


13 


8 


0.5 


8 


0.5 


8 


0.5 


14 
Total 



1,617 


0.0 
100.0 




1,497 


0.0 




1,797 


0.0 8 


100.0 


100.0 3 



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



| TITLE: 

FUTURE AIRSIM SCHEDULESl 
(FLEET MIX) 



Landrum & Brown 

AIRPORT CONSULTANTS 



jCXHIW? 

A-9 



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QHare Delay Taskforce Study 
Chicago O'Hare international Airport 



itle Mean ARRIVAL/ARRIVAL 
iEPARATIONS-AIRSIM MOPE! 



_J ro X 



Landrum & Br own 



A 19 





TODAY'S 


ATC 














All 


Wea 


ther 










Conditions 




Trai 


ircraft CI 


ass 






S 




L 




H 




S 


.33 




.33 




.33 


Lead 














Aircraft 


L 


.33 




.33 




.33 


Class 
















H 


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.33 




.157 



GROUP 2 ATC 






All Weather 
Conditions 


Trail Aircraft Class 
S L h 


Lead 

Aircraft 

Class 


, S 
L 
H 


.2 .2 .2 
.2 .2 .2 
.2 .2 .1 



GROUP 4 ATC 








All Weather 
Conditions 




Trail Aircraft CI 


ass 






S 


L 


H 




S 


.15 


.15 


.15 


Lead 










Aircraft 


L 


. 15 


.15 


.15 


Class 












H 


.15 


.15 


.07 



d-Ware Delay Task force Study 
Chicago O'Hare International Airport 



TITLE 



STANDARD DEVIATIONS 
FOR ARRIVAL/ ARRIVAL 
SEPARATIONS (AIRS1M KJODEl 

A 20 



Landrum & Brown } 

AIRPOPT, CONSULTANTS', 



lEXHIWT: 

AH 















TODAYS AND GROUP 2 


FALLBACK ATC 






1 






Mean 






Standard 






Separation 






Deviation 


Lead A/CA 


Trail A/C 


(seconds) 






(seconds) 


S,L 


S # L (>45 u )# 


60 






3.3 


S,L 


S,L (<45°)* 


90 






10.0 


H 


H 


100 






3.3 


H 


S,L 


120 






3.3 


GROUP 2 AND GROUP 4 


FALLBACK ATC 






! 






Mean 
Separation 






Standard 
Deviation 


Lead A/C 


Trail A/C 


(seconds) 






(seconds) 


S,L 


S,L (>45°) 


60 






3.3 


S,L 


S,L (<45°) 


60 






3.3 


H 


H 


90 






3.3 


H 


S,L 


90 






3.3 




GROUP 4 ATC 












Mean 






Standard 






Separation 






Deviation 


Lead A/C 


Trail A/C 


(seconds) 






(seconds) 


S,L 


S,L (>45°) 


60 






3.3 


S,L 


S,L (<45°) 


60 






3.3 


H 


H 


60 






3.3 


H 


S,L 


60 






3.3 | 


Required time separation at an intersectior 


i after a heavy aircraft 


passes through 


airborne 










! 




Croup 2 ATC Group 4 ATC 


Safe (no vortex) 


90 




60 




j 


Fallback (vortex) 


120 


[today) 


90 


(G 


roup 2) 






S - Small, L - Large, H - Heavy 
Flight paths diverging by more than 45° 
Flight paths diverging by 45° or less 



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



Ititlc: DEPARTURE AND 
INTERSECTION SEPARATIONS 
AIRSIM MODEL 



IsxMtsrr 



Landr<u,.„ 

« »■ ^'"POKf CONSULTANTS;;' 



A 21 



DISTANCE FROM OUTER FIX IN NAUTICAL MILES 


Runway 


OUTER FIX 


Farmm 


Base 


Plant 


Vains 


4R 


62.9 


59.7 


57.6 


25.5 


4L 


55.0 


63.5 


62.4 


25.3 


9R 


37.7 


66.8 


68.7 


28.2 


9L 


36.8 


63.8 


70.2 


I'd. 1 


14R 


28.0 


65.6 


71.5 


42 . 3 


14L 


28..0 


47.7 


70.3 


43.5 


22R 


46.2 


30.1 


61 .4 


58.2 

j 


22L 


48.7 


29.8 


59.6 


61.6 


27R 


54.9 


38.9 


44.4 


59.8 


27L 


64.5 


35.9 


43.2 


56.8 


32R 


63.3 


54.1 


36.5 


59.5 


32L 


62.6 


56.3 


36.7 


52.4 



Note: Not all of these flight path distances were actually 
used in the AIRSIM experiments and are only 
presented for completeness. 



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



TITLE: 



Flight path distances 
(airsim model) 



Landrum & BrownS 

, i AIRPOHT CONSULTANTS \ 



A 22 



mm 



DEPARTURE RUNWAY 


ARRIVAL RUNWAY 


DEPARTURE/ARRIVAL SEPARATES] 
(nautical miies) 


VFR SFR 


4L 


9L 
14L 


1 

2 


2 

2 


4R 


9R 


A 


2 

1 J 


9L 


14L 
22R 


2 2 
1 2 


9R 


4R 

14R 

9R 


2 2 

1 2 

R.O.T.^ 2 


22L 


27L 
22L 


1 2 
R.O.T. 2 

: 


27L 


14R 
32L 


2 T 2 i 

2 2.5 


32 L 


27L 


!# i 


32R 


27R 
22R 
32R 


1 
2 
R.O.T. 


2 

2 

i 

2 



AIRSIM does not release a departure if an arrival is within 2 miles 
of the 9R threshold; however, as soon as the arrival has touched 
down, the departure is released. 
Runway Occupancy Time 
Independent 




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



Jtitu: DEPARTURE/ARR8VAL 
SEPARATIONS (nautical mites) 
AIRSIM MODEL 



ftLa;ndrufn 4 

AIRPOBT CO 



A-23 



CONSOLIDATED LISTING OF RESULTS 



For convenience, Exhibit A-15 presents the design matrix for all model 
experiments, both FAA and Landrum S Brown (AIRSIM) . Exhibit A-16 pre- 
sents the results from all FAA model capacity experiments. Exhibit A-17 pre- 
sents the results from all AIRSIM capacity experiments, while Exhibit A-18 
presents the results from all AIRSIM delay experiments. 



A-24 



\ ATC E3UIS>MENT 

\ SCHEDULES, AM 

\ SPECIAl 


Eau 
Rul 


ling ATC 
H Prior to 


EXISTING ATC EQUIPMENT AND RULES 


FUTURE OROUP > ATC 
EQUIPMENT AND RULES 


FUTURE GROUP* 
ATC EQUIPMENT AND RULES 




Nov IS. 197S 


SEPTEMBER 1875 OPERATIONS SCHEDULES 


If? 

Ir 

5 & 


ft 1 
H 


if! 


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117% Heavy Ml,) 


Po.t IMS 
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(•SI Heavy 

MIX 


Pre IMS 

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Poii 1963 Schedule. 
(IS! Heavy Ml.) 




\ MODELEC 

OOMFKaj(IATiOt\ 
AND WEATHER \ 
COtMHtWIONS \ 
MODELED 


Jan Operation! 
1975 Schedule* 




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O'Hare Delay Taskforce Study 
Chicago O'Hare Ihternatiorial Airjport 



V™* FA A CAPACITY 
MODEL RESULTS 



Federal Avia|i(0rt| 
Admin istratibn * 



A-26 



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O'Hare Delay Taskforce Study 
Chicago O'Hare Internat ional Airport 



TITLE: 



CAPACITY^) RESULTS 
AIRS1M MODEL 

A 2 7 




Landrum & Bro 

AI«l»0«T CONSULTAN. 




A Jl 



APPENDIX B 



AN OVERVIEW OF "AIRSIM" 
THE AIRSPACE/AIRFIELD SIMULATION MODEL 



Developed By: 

LANDRUM S BROWN 
AIRPORT CONSULTANTS 



For: 

The Department of Aviation 

City of Chicago 

Chicago, Illinois 



</ / 






APPENDIX B - "AIRSIM" 



The purpose of this appendix is to present a general description of the 
airspace/airport simulation model, "AIRSIM", developed by Landrum S Brown 
for the City of Chicago's Department of Aviation. The document is abstracted 
from the first of five proprietary volumes which, together, completely describe 
the model. This abstract addresses five key areas: 

Background, 

Model Development Objectives, 
Conceptual Description of "AIRSIM", 
"AIRSIM" Software Description, and 
"AIRSIM" Validation. 

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

1. BACKGROUND 

In 1972, Landrum & Brown developed an apron/gate simulation model for 
the City of Chicago for the purpose of evaluating alternative concourse expan- 
sion programs. The alternatives included an extended concourse versus a 
chevron concept of gate expansion for O'Hare's apron/concourse system. Pre- 
liminary results of this evaluation indicated that the number of additional gates 
required at O'Hare might well be a function of airspace and/or airfield limita- 
tions as opposed to geometric constraints of the apron/gate areas. The City of 
Chicago responded to these findings by requesting that Landrum 6 Brown de- 
velop a quantitative technique with which to measure the true capacity of O'Hare's 
runways and terminal airspace — one which would ensure the development of a 
balanced airside/landside facility. Further, it was specified that the technique 
have general applicability as a planning tool with the capability of calculating 
selected cost, environmental, and operational implications (e.g., delays) of 
Chicago's options for the use of its airspace/airfield system. These options in- 
cluded new airfield facilities at O'Hare and Midway, the transfer of selected 
flights from O'Hare to Midway, changes in FAA airspace rules and regulations, 
and a possible third Chicago airport. 

After a thorough literature search and review of existing techniques for 
evaluating airspace/airfield systems it was determined that: 

No quantitative techniques existed which fulfilled all of 
the City's requirements. 

Digital computer simulation offered the most efficient, 
cost-effective means of problem solution. 



ft/ 



Therefore, a program was initiated to construct a high speed, stochastic, 
event sequenced, airspace/airfield simulation model for the Department of Avi- 
ation, City of Chicago. 

The project resulted in the development of a planning tool which enables 
the City to define the Chicago terminal area airspace system in terms of air 
traffic control procedures, outer fixes, climb and descent corridors, inner 
and outer holding stacks, and approach flight paths. Within this defined term- 
inal airspace system, any number of airfields (either existing or planned) may 
be described to the model and their interactions assessed. The model may be 
used to simulate the system's response to any volume/fleet mix combination of 
aircraft demand which may be imposed on the system from any geographic 
location and with any desired peaking characteristics. 

The true worth of the model to the City is derived primarily from its 
total system concept of problem analysis. That is, Department of Aviation 
planners are now able to observe the airspace/airfield system's operation 
(by analyzing the simulation output) and assess the implications of any phy- 
sical, procedural, or activity change on the entire Chicago Terminal airspace 
system. 



2. MODEL DEVELOPMENT OBJECTIVES 



What is meant by the term "capacity"? Webster defines capacity as the 
ability to accommodate. Classical queuing theory defines the capacity of a 
system as its maximum throughput rate under conditions of infinite queues 
and 100 percent utilization of the serving units. It is capacity of the overall 
airspace/airfield system which is sought in planning work; however, many 
existing capacity techniques give superficial treatment at best to the airspace 
component of the system, focusing mainly on the airfield. Attempts to apply 
these airfield techniques to form conclusions regarding the capacity of the 
entire system have, in the past, furnished less than accurate, if not mislead- 
ing, information to planners. Further, the assumptions inherent in some exist- 
ing capacity techniques severely limit their application. 

For example, should airspace/airfield system capacity analyses be 
based upon an airfield technique which presupposes acceptable delay levels? 
What levels of delay are acceptable? Are these levels of delay universally 
acceptable? Is it accurate to state that system capacity is the maximum pos 
sible airfield throughput under conditions of infinite queues? Is knowledge 
of the airfield throughput rates and levels of delay adequate to assess the 
capacity of the entire airspace/airfield system? How does the geometry of 
the terminal area airspace affect the system? How do air traffic controller 
workload, aircraft sequencing, and merging considerations affect the sys 
tern? Landrum £ Brown and the Department of Aviation felt that these ques 
tions had to be satisfactorily answered. 



F-2 



Accordingly, the objective was to develop a quantitative, state-of-the- 
art, airspace/airfield analysis tool with the capability of predicting the total 
system's response, in terms of cost, environmental, and operational para- 
meters, to any option the City /Airlines or Federal Aviation Administration 
might desire to exercise over the Chicago airspace/airport system. Further, 
the tool was to provide not only for detailed analyses of the throughput capabi- 
lities of the entire system, but also for detailed analyses of the many factors 
which determine this throughput such as: 

Fleet Mix Characteristics, 

Airline On-Time Performance, 

Demand Peaking Characteristics, 

Meteorology, 

Air Traffic Control Rules, Regulations, and Procedures, 

Terminal Airspace Structure, and 

NAVAIDS. 

It was also desired that the technique developed should provide the analyst with 
a tool for examining (often overlooked) measures of system performance, includ- 
ing: 

Average Delay per Aircraft 

Inbound 
Outbound 

Average Delay per Delay 

Daily Distribution of Delay (with emphasis on quota hour periods) 

Delay Costs 

Facility Utilization Statistics 

Departure Runway Queue Statistics 

Stack Sizes and Durations, and 

Environmental Impact. 

The resulting model, "AIRSIM", is described in the following section. 



3. CONCEPTUAL DESIGN OF "AIRSIM" 

The objective in simulation modeling is to develop an abstraction of a 
real world system which reasonably reproduces the characteristics of that 
system. When this abstraction is sufficiently developed then it, instead of the 
real world system, can be observed for problem solving purposes. In airspace/ 
airfield system analyses the advantages of simulation are readily apparent--the 
actual system is simply too large to observe in its entirety. Even if the system 
could be observed, it only functions as today's operational rules and procedures 



E-3 



permit. The questions most often asked of problem solvers deal with the per- 
formance of the system under future operational rules and procedures. There- 
fore, simulation modeling offers a viable alternative to this dilemma. 

Every simulation model is constructed from certain basic definitions, 
assumptions, and concepts. An understanding of these is essential if the 
adequacy and appropriateness of the model for a particular application is 
to be assessed. The basic concepts of "AIRSIM" may be summarized, topically, 
as: 



System Boundaries 

Entities, Events and Event Processing 

Variables 

Decision Processes 

Data Input Requirements 

Measures of System Effectiveness (Model Output) 



Each of these is discussed in the following paragraphs. 



(1) System Boundaries 

The outermost limits of the system modeled are the major outer fixes 
along the perimeter of the Chicago terminal area airspace. The innermost 
limit of the system is the outer taxiway at O'Hare, or a similarly defined 
division between the airfield and apron/gate areas for other airports to 
be modeled. Between the outer and inner limits of the system modeled 
"AIRSIM" is capable of recognizing certain system characteristics. For con- 
venience, these characteristics can be summarized under one of three ma- 
jor divisions of the system: approach control airspace, flight tracks, and 
airports. 

Approach Control Airspace - Exhibit B-1 depicts the ter- 
minal area airspace considered in the model. Although 
as many entry points to the airspace system as desired 
may be defined to "AIRSIM", those employed are generally 
the five primary outer fixes (Base, Plant, Chicago Heights, 
Vains, and Farmm) located along the perimeter of the ter- 
minal area airspace. Due to the necessity of processing air- 
craft to or from certain geographical regions through particu- 
lar outer fixes, a method of locating the fixes within the air- 
space was required. To accomplish this the airspace was 
divided into 16 segments, each 22-1/2°, numbered clockwise 
beginning at true north. This numbering system allows each 
airport within the overall system to have up to 16 fixes serv- 
ing it (one fix per segment) . The assignment of fixes to air- 



B-4 



& 



& 




STUDY AREA APPROACH CONTROL A5RSPACE 




STUDY AREA AIRWAYS AND NAVAIDS 










B-5 



space segments is made within the schedule processing pro- 
gram as will be explained elsewhere. This division of the 
airspace provides flexibility, in terms of analyzing alterna- 
tive airspace geometry, which as "AIRSIM" recognizes, is 
influenced by the number and location of the outer fixes and 
their distances from the runway thresholds. Flight track 
distances provide the means to specify the distances from 
the outer fixes to the runway threshold. 

Flight Tracks - Within the terminal area airspace at Chicago 
there are very specific routes over which air traffic con- 
trollers generally guide aircraft from each outer fix to a 
given runway threshold. These routes are called flight 
tracks and were identified in discussions with Chicago air 
traffic controllers. From these tracks, examples of which 
are shown in Exhibit B-2, flight path distances from all 
outer fixes to all runway thresholds were derived. Along 
each flight track there are six points that "AIRSIM" rec- 
ognizes: 

Outer Fix - The outer fix is a navigational waypoint 
which marks the entry into terminal airspace and 
also, if necessary, serves as a focal point for a hold- 
ing stack. 

Merge Point - A merge point is a point where two or 
more flight tracks intersect, forming a common path 
to the runway threshold. 

3,000' Intercept - The 3,000' intercept is the point 
where the flight track intersects the 3,000' flight level. 
It is necessary to identify this point so that "AIRSIM" 
can calculate the total time that an aircraft spends be- 
low 3,000 feet to use in later environmental analyses. 

Missed Approach Point - The missed approach point, 
usually located about a mile from the runway threshold, 
is the point on the flight track at which a pilot must 
have his aircraft stabilized and the threshold in view 
or else execute a missed approach. 

Outer Marker - The outer marker, on each ILS equipped 
runway, identifies the point of glide slope interception. 
This is the point at which reductions in approach velo- 
city may be initiated by individual aircraft in the Chi- 
cago terminal area airspace. 



B-6 




B-7 



Threshold - This is the beginning of the usable portion 
of a runway. 

Airports - The third major division of the overall system 
modeled is the airport component. Although "AIRSIM" can 
simulate any number of airports within a given airspace sys- 
tem, all output formats and array sizes are based on a maxi- 
mum of three airports. If more than three airports ever need 
to be analyzed, array sizes and output formats in the program 
source code must be changed . 

To describe an airport such that its physical characteris- 
tics can be easily interpreted by the model requires three 
definitions. 

Runway Exit Node - A runway exit node is simply a 
runway turnoff, classified as either a high, medium, 
or low speed exit. For identification purposes every 
usable exit at ORD was given a number. The numbers 
were in sequential, increasing order for a runway and 
were not duplicated . 

Runway Entrance Node - A runway entrance node was 
defined as the point of entry onto an active departure 
runway. "AIRSIM" allows one such entry node which 
usually corresponds to the last exit node number of the 
corresponding opposite direction runway, i.e., the en- 
trance node number for runway 22L was the same as 
the last exit node number for runway 4R. 

Outer Taxiway Node - An outer taxiway node is a point 
of entrance/exit to or from the apron/gate area. All 
outer taxiway nodes taken together forma natural divi- 
sion between the system simulated by "AIRSIM" and the 
system simulated by the "CATESIM" model. 

The term outer taxiway node came about from the outer 
taxiway at O'Hare Airport. Although this taxiway forms 
a natural division line on which to define entrance/ exit 
nodes, the nodes may be defined at any point. 



B-8 



,2, EntUies^EvenU i _an £L I^^ 



• ihe airspace/airfield s.mu- 

The entities, or units, of main interes tin ^ ^ 

,ation model are defined as the ,nd,v£u -•<« are recog „ized by 

lh e system Fourteen d, e en. a,rc n* and a|r)|nes recognize u 

"AIRSIM" for each of 13 alrl ' n «„ resDec , iv ely . 
are listed in Exhibits B-3 and B-4. respect. 

■ ,. »rea airspace/airfield system. 
To aid in modeling the Chicago term.nal area a p^ ^.^ rf 
,he entire system was P-rt.t»njdm to event ^ particular parti- 

activities that an aircraft must P-*^' f , to proces5 the event "en 
tion in the system. For example for a »» ^^ must be 

ter the active runway and accelerate 



examined: 

Inbound Aircraft Proximity, 
Previous Departure Proximity, 

Destination Heading, 
Runway Entrance Velocity, 

Runway Acceleration Rate, and 
Lift Off Velocity . 



ft are shown in Exhibit 

The events to be P^^^by oX-d •"»•* '" ^ 
B-5. Those events to be processed oy 



in Exhibit B-6 



„t processing is employed by 
The "next-event" concept of event process g which the 

"A.RSW". This implies that the ^l^h the next even, may begin) 
,ast event was completed (the «^^**„n through the system 
or all aircraft in the »~J*~fi%L in which the events are 
then is by an iterative process 'echniq sele cted. mathema- 

se!ected in chronological order • W ^V an r med which indicate the .me 

when the statistics are y» svstem is descrioeu. 

JL* of that aircraft through the sysw g com , 

the passage of that for a|| airc raft or for a.rcra 

tistics may also be averag to tne same ^ airline) ^^ 

m on characteristic isucn ma|RS im» a re averaged, they Turn. 
l„y statistics gathered * A'^" '^ of the system's operational 
Ture's of effectiveness ^^^ures of effectiveness are d,s 



efficiency may be judged 
cussed in subsection (6) 



B-9 



AIRSIM 

Aircraft 

Code 

1 



2 
3 
4 
5 

6 
7 
8 
9 

10 
11 
12 



Aircraft Types 



13 



14 



B-707-120, 320, 420, B-720; DC-1-20, 30; 
CV-880 

B-707-120B 

B-727-100 series 

B-727-200 series 

B-737-100, 200; DC-9-10, 20, 30, 40, 50; 
BAC-111 

B-747-100, 200B, 200C 

DC-10-10, 20, 30, 40; L1011; A-300B 

Concorde, TU-144 

Jetstar, Learjet, Falcon, F-28, Culfstream 
Scbre, SA-28T 

L-188; L-100; DC-6, 7; Viscount; Electra 

CV-580, FH-227, M-404 

Beech Baron, Queen 80, B-99; Cessna 400 
Series, Aero Commander 500; Piper Aztec; 
Swearingen Metro 

Cessna 150, 172, Turbo-Centurian Bonanza; 
Twin Otter; Cherokee Six; Ballanca Turbo 
Viking 

B-707-320B; DC-8-61, 62, 63 




B-10 






Code No 



Airline (Parking Location) 



1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 



International 

Continental 

Northwest 

Braniff 

Eastern 

United 

Ozark 

TWA 

Air Canada 

North Central 

Delta 

American 

Allegheny 



IN 

CO 

NW 

BN 

EA 

UA 

OZ 

TW 

AC 

NC 

DL 

AA 

AL 



m 





B-11 




q 




B-12 






M:w 



I' - H : l 



-Z. co 
lu > 

CO 




B-13 



(3) Variables 



Variables in the "AIRSIM" model include both decision (controllable) 
and uncontrollable variables. Decision variables are those variables of 
the system which are under direct control by the analyst and uncontrol- 
lable variables are those over which the analyst has no control. Examples 
of decision variables are: 



Outer Fix Placement, 

Flight Track Length, 

Outer Marker Location, 

Arrival Fix/Arrival Runway Assignment, 

Controller Workload Criteria, 

Departure Path /Departure Runway Assignment, 

Aircraft Spacing, 

Aircraft Velocities, and 

Airline Schedule. 



Examples of uncontrollable variables are: 



"Upline" Delays to Inbound Aircraft, 
Touchdown Points for Arriving Aircraft, and 
Aircraft Service Delays. 



(4) Decision Processes 



The decision processes within the "AIRSIM" model include the oper- 
ating procedures in effect within the Chicago terminal area airspace and 
at O'Hare International Airport as of November, 1975. Many of these pro- 
cesses or procedures consist of both variable and non-variable components, 
of which the variable components may change by runway configuration. In 
these cases the non-variable components are internal to the model and are 
operative upon being supplied the variable components or parameters. 

An example of such a variable decision process (configuration depen- 
dent) is the issuance of departure clearances to aircraft on an intersecting 
arrival/departure runway pair. Depending on the arrival/departure run- 
way pair, controllers may issue departure clearance if an inbound aircraft 
is as little as one nautical mile from the arrival runway threshold in some 
configurations while requiring a minimum of two nautical miles in other 
configurations (the actual distances input to "AIRSIM" are summarized in 
Appendix A) . In either case the decision process is similar: the only 



B-14 



• ~4 „f thA arrivinq aircraft from the 
difference is the •*-" U -^"££?i £ decision processes 
threshold, in 9-eral var able porho „^ o ^ ^ program 

are automatically supplied to the model ay assump tions internal 

execution time. Decision processes, rules, 
to the model are summarized below. 

Stacking Rules: 

- Aircraft in stacks are first in. first out 

. sucks, if they exist, are located at the outer fixes 

toring time which is currenuy 

eludes: 

_ ten to 12 minutes of approach control zone 

_ SSfflv. minutes of enroute slowdown 

_ An approach controller's workload normally will not 
exceed 12 aircraft and includes. 

zone 

• a »oi v three aircraft could be on 
l„ addition, approx.mately ^"^ contro! , so tha t, 

approach to a ^-Y . und^ w ft tne mode , 

on the average, the total num ^ • , e rU n- 

a.lows to be conducting an approach to s.ng 

way is 15. 

- An approach controller's workload may never exceed 

14 aircraft 

to 14 aircraft to avoid starting a stack. 

• i= fivina the approach control zone, common 
Seauencing arrivals, flying me cw 
• broach path, and the glide slope path. 



B-15 



"Target" arrival/arrival separations are ensured between 
lead and trail aircraft pairs at critical points of an approach. 
These "target" separations are chosen from a normal distri- 
bution and reflect the minimum separations which ATC pro- 
cedures and weather conditions desired to be simulated 
permit Three weather conditions are generally of 'n*^** 1 ' 
although additional conditions may be described to the model. 

These weather conditions are described below in terms of 
ceiling (in feet above ground level) and visibility (statute 
miles) . 

— Weather condition 1 

. . ceiling/visibility greater than or equal to 

3500/5 

-- Weather Condition 2 

. . ceiling/ visibility greater than or equal to 
1000/3 but less than 3500/5 

— Weather Condition 3 

. . ceiling/visibility greater than or equal to 
500/1 but less than 1000/3. 

The means and standard deviations for "target" arrival /arri- 
val separations under existing and proposed new generation 
air traffic control equipment groups are presented in Appendix 
A for each of these three weather conditions. 

Critical points of separation are as follows: 

— In the Approach Control Zone and Common 
Approach Path 

Outer Marker - if lead aircraft is slower 
Merge Point - if lead aircraft is faster 
and aircraft are from different fixes 
Outer Fixes - if lead aircraft is faster 
and both aircraft are from same fix 

— On the Glide Slope 

Threshold - if lead aircraft is slower 
Outer Marker - if lead aircraft is faster 



B-16 
f 



lassjis*-. 



. n.r "sees" that his workload will equal or 
When a controller sees inai means 

exceed M aircraft w thin the nex .hou, ^the ( be 

(except for the last listed «£££*£, means wl.l 
decreased by 1 m.le (■.••-' <**< es ? mi|es und er 

never be decreased be.o» ,3 3*. and ^ separations 

today's ATC system and rules) f( .„ 

wil | be maintained until demand Ml be* 

th e next hour and W«r £^££J *rti during peak 

This reflects a controller s increase 



hours. 



As ne w aeration ATC ^ment groups are JjJ-u-. 
it is expected that controllers w. ' be traffic flow. 

increase their efforts in "f"*^^ t w ,„ become 
This is because separation between aire capa _ 

, arg ely a function * W«l^ »"£ Vaqulpmant. this 

increased workload factor win n 
has not been included in "AIRSIM . 

„ a ;rrraft from different fixes will be 
Merging between two aircraft from a 
allowable, if distances permit. 

_- Minimum "target" separation at critical points on 
approach must be obaen* * g ., „ 

" SSL^Sll- exists between 
the two aircraft already sequenced. 

Five and one-half miles if lead aircraft 

is non-heavy. 

Eight miles if lead aircraft is heavy. 

mon approach path win oe standard 

uted velocity calculated using a mean 
deviation for each aircraft type. 

♦h «,ill be flown at a normally 

standard deviation for each a.rcratt typ 

. Flig ht path crossing InvoM ^P-^- "T 
craft requires a two minute sepa 
minutes is required: 



B-17 



— Prior to departure clearance when a departure 
flight path will cross the path of an arriving 
heavy aircraft. 

— Prior to crossing the threshold when an arriv- 
ing aircraft's flight path will cross the path of 
a departing heavy aircraft. 

This two minute (120 seconds) separation changes to: 

~ Ninety seconds under group 2 ATC equipment 

— Sixty seconds under group 4 ATC equipment 

Arrivals have priority over departures. 

Sequencing departures from independent runways, mixed 
operation runways, and intersecting arrival /departure run- 
way pairs. 

A departure is sequenced in either: 

— The previous departure, or 

— The aircraft inbound to the arrival runway, 
whichever is more critical. 

Time separations drawn from the normal distribution 
are employed between necessive departures. The 
means and standard deviations of the distribution 
vary to reflect different ATC equipment groups. The 
means and standard deviations of departure/departure 
separations used in the "AIRSIM" experiments are 
presented in Appendix A. 



(5) Data Input Requirements 



In any simulation model of significant scope the data input require- 
ments are quite large and if not given careful consideration, quickly 
become burdensome. The problem of data entry into "AIRSIM" has 
been solved by gathering physically similar data into five logical group- 
ings, called master files. The first three of these master files (airport 
data, runway data, and aircraft data) contain data related to aircraft 
performance and airport facility characteristics. The master file con- 
cept is effective because it allows a complete data base to be created 



"X 



B-18 



and updated independently of "AIRSIM" itself. The master files are 
interactive with "AIRSIM" and, upon initiation of a simulation experi- 
ment, furnish all data related to the airports and the aircraft using them. 
In this manner the user is freed from the task of entering data for each 
run. In addition, he conserves resources because only data that will 
actually be used in the particular simulation run are transferred from 
the master files to core storage for program execution. 

The other two master files contain general data and forecast opera- 
tional data—all five are described below: 

Airport Data - The airport data group defines the physical 
relationship of all runway exits to all other taxiway entry 
points. This data group is the basis for the airport master 
description file. Airport data requirements are: 

Distance in feet from every runway exit to every 
outer taxiway entry point. 

Distance in feet of every runway exit from its 
associated runway threshold (or displaced thres- 
hold, if any) . 

- ■. Type of each runway exit: 

.. low speed (60°" 170°) 

medium speed (31° - 59°) 
.. high speed (10° - 30°) 



Runway Data - The runway data group describes the physi- 
cal characteristics of not only each runway, but of each run- 
way's flight track from each outer fix. The runway data 
group is the basis for the runway description master file. 
Runway data requirements are: 

Length in nautical miles of flight tracks from every 
outer fix to every runway threshold. 

Distance in nautical miles from every outer fix to the 
merge point (beginning of the common approach path) 
for every flight track. 

Exit numbers for all exits on all runways. 

Outer taxiway entry point probabilities for every 
outer taxiway entry point for every airline. 



B-19 



Outer taxiway exit point probabilities for every 
outer taxiway exit point for every airline. 

Distance in nautical miles from the missed approach 
point to the threshold for all runways. 

Usable exits on each runway. 

Type of each departure runway entry node. 

.. low speed (60° - 170°) 

medium speed (31° - 59°) 
.. high speed (10° - 30°) 

Length in nautical miles of all glide slope paths. 

Departure runway entry node number for all departure 
runways . 

Flight track distance in nautical miles from the 3,000 
foot intercept to the threshold for all runways. 

Distance in feet from threshold to intersection for inter- 
secting runways. 

Aircraft Data - The aircraft data group consists of all data re- 
lated to aircraft performance, either on the ground or in the air, 
This group is the basis for the aircraft master description file. 
Aircraft data requirements are: 

Distribution of time to taxi from outer taxiway entry 
points to the gate area for all airlines and all air- 
craft types (empirical distribution) 

Distribution of actual gate occupancy times for all 
airlines and all aircraft types (empirical distribution). 

Distribution of time to tow an aircraft from gate to apron 
area for all airlines and all aircraft types (empirical 
distribution) . 

Distribution of time to taxi from the apron area to 
outer taxiway exit points for all airlines and all air- 
craft types (empirical distribution) . 

Mean approach control zone velocity (from outer fix to 
outer marker) for each aircraft type. 



B-20 



Mean glide slope velocity for each aircraft type. 

Runway coast velocity for every aircraft type. 

Taxiway taxi velocity for every aircraft type. 

Standard deviation of glide slope path velocity. 

Standard deviation of approach control zone velocity. 

Mean touchdown distance in feet for every aircraft 
type. 

Standard deviation of touchdown distance for every 
aircraft type. 

General Data - The following data is stored internally by the 
model: 

Mean and standard deviation of "target" separation 
distance between arriving aircraft. 

Distributional form of "target" separation between 
arriving and departing aircraft (e.g., normal). 

Distributional form of approach control zone velo- 
city for different aircraft type. 

Distributional form of glide slope path velocity for 
different aircraft type. 

Distributional form of runway touchdown point for 
different aircraft type. 

Empirical distribution relating mean "target" separa- 
tion in approach control zone to mean "target" separ- 
ation on common approach path. 

Mean and standard deviation of time separation in be- 
tween successively departing aircraft. 

Maximum number of aircraft a controller can control 
at any given time (for both normal and overload con- 
ditions) . 

Maximum time an aircraft can be vectored in the 
approach control airspace. 



B-21 



Forecast Operational Data - "AIRSIM" does not have provisions 
for creating a schedule of arriving and departing aircraft to pro- 
cess but rather relies on this information being supplied exter- 
nally by a traffic forecasting model. This model "loads" each 
expected operation onto a data storage file which is made up of 
individual records, each of which represents either a system 
arrival or a system departure. The data storage file furnishes 
input to the schedule processing program, which was previous- 
ly described. The output of the schedule processor is schedule 
of operations which the system to be simulated must attempt to 
process. 

A complete Chicago data base has been assembled and is constantly 
updated as airspace and airport geometry, rule changes, and other data 
changes are introduced. The data for "AIRSIM" were collected from many 
sources, depending on whether they were classified as either non- 
operational or operational data. 

Non-Operational Data - Airport and runway data were 
gathered from four major sources: 

U.S. Aeronautical Charts, 

Airport Layout Plans, 

FAA Personnel and Documents, and 

FAA Tower/Tower, Tower/Center letters of agreement. 

Operational Data - Operational data for "AIRSIM" were collected 
by statistical sampling during several surveys at O'Hare. Ob- 
servations were made of arriving and departing aircraft by 
survey team members at five stations: 

TRACON Room (from radar scope) 



Velocity and time at outer fix 
Velocity and time at 15 miles 
Velocity and time at five miles 
Airline and flight number 
Time between successive departures 



Outer Taxiway 

Taxi velocity for all aircraft types 
Airline and flight number 

Runway Ends 

Time threshold to touchdown 
Airline and flight number 



B-22 



Tower Cab 

Runway exit usage 
. . Outer taxiway entry and exit patterns 
runway occupancy times 

Old Tower Cab 

Gate occupancy times 
. . Push out times 
. . Taxi in/taxi out times 

Once the data were collected, they were entered onto data pro- 
cessing cards, verified, and statistically analyzed to determine 
the necessary model parameters. 



(6) Measures of System Effectiveness (Model Output) 

Measures of effectiveness, as used in systems analysis, are those quali- 
ties of the system which indicate the degree to which the goals of the system 
are accomplished. For the Chicago O'Hare airspace/airfield system, the ac- 
cepted goal is to process aircraft to and from O'Hare with minimum delay. 
Therefore, all measures of effectiveness employed by "AIRSIM" were di- 
rected toward determining how efficiently this is being done. Some of these 
measures of effectiveness or model outputs are briefly described below: 

Inbound delay — the sum of stack delay and vectoring 
delay. 

Stack delay - time an aircraft departs the outer 
fix minus the time it arrived at the outer fix. 

Vectoring delay - the time over and above the 
time required to fly from outer fix to runway 
threshold over a predetermined route at a nomi- 
nal velocity. 

Outbound delay — the time required (for departures) from 
leaving the outer taxiway until receipt of departure clearance 
minus the same time under no queue conditions. This defini- 
tion assumes that departure clearance is issued immediately 
under no queue conditions. 



B-23 



Total throughput — the sum of arrival throughput and de- 
parture throughput. 

Arrival throughput is the total number of arrivals 
processed in a given time. 

Departure throughput is the total number of depar- 
tures processed in a given time. 

Means, standard deviations and 95 percent confidence intervals are gene- 
rated as part of the standard statistical output for the above measures of 
effectiveness. In addition, each measure is available in virtually any form 
the analyst requests of the model . For example: 

by day 

by hour 

on a scheduled basis 

on a processed basis 

by airline 

by runway 

total, average, average per delay (for all delay measures) . 

Other supplementary output available includes: 

Distribution of Delays — all delay statistics are presented 
in relative frequency distributions with interval widths of 
five minutes. 

Stack Utilization — The percentage of total time during 
which aircraft were stacked is available for each outer fix. 
In addition, graphs are generated which depict stack start 
and stop times. 

Departure queue and stack sizes: 

average 

average when a queue or stack exists 

maximum 

For definitional purposes, a departure is considered in the 
departure queue when it enters the system at the outer 
taxi way. 

Operational Backlogs -- output is available which compares 
scheduled arrivals and departures to actual arrivals and 
departures in order to determine operational backlogs or 
unprocessed operations which carry over into following time 
periods. 



B-24 



Wave Offs -'- those arrivals which could not complete their 
approaches because the runway was occupied by the pre- 
vious operation. 

Again, it should be stressed that the entities or units of main interest 
in "AIRSIM" are individual aircraft and it is on the aircraft level at which 
statistics are collected. This implies that essentially any data related to 
the performance of an individual aircraft is available for analysis. 



4. "AIRSIM" SOFTWARE DESCRIPTION 

The "AIRSIM" model consists of four basic computer programs which are 
usable by persons without an extensive knowledge of computers. The four basic 
programs are: 

Data Base Creation Program - A complete data base creation 
program in which all information pertinent to O'Hare and any 
other airports is entered into a permanent file. This data 
base may be updated at any time, independently of "AIRSIM". 

Schedule Processing Program - As input, the schedule pro- 
cessor uses output from the Chicago traffic forecasting model 
or other sources which provide a schedule of demand. To be 
interpreted by "AIRSIM", simulated aircraft arriving in the 
Chicago terminal area must be assigned a clearance limit fix 
and aircraft departing the area must be assigned a departure 
runway. These assignments are made by the schedule pro- 
cessor based upon the geographic origin or destination of the 
aircraft, the overall percentage of arrivals or departures to 
be allocated to each runway, and any restrictions to traffic on 
specific runways. The program makes the assignments on an 
hourly basis and ensures that demand is balanced among the 
runways In use. 

"AIRSIM" - The AIRspace/Airfield Simulation model performs 
all actual processing of aircraft. "AIRSIM" is interactive with 
the independent data base and will automatically retrieve only 
the data needed for a particular run, thus saving time and 
operating expense. At the completion of a simulation experi- 
ment "AIRSIM" creates an output file of all pertinent data 
accumulated during the run~the data may then be analyzed 
and destroyed or saved for future reference. 



B-25 



Post-Processor - The Post-Processor is independent of "AIRSIM" 
and may be run at any time in order to reduce data stored on the 
output files created by "AIRSIM". A complete statistical summary 
report is produced presenting means, standard deviations, confi- 
dence intervals, distributions, and graphs of all important para- 
meters produced by a given "AIRSIM" experiment. 

The above four computer programs were written in FORTRAN IV for the Control 
Data Corporation 6000 Series computer. 



5. "AIRSIM" VALIDATION 

To validate a simulation model two questions must be answered: 

Does the model perform as intended? 

Does the model's performance duplicate that of its real 
world counterpart? 

In answering the first question, individual subroutines were removed 
from "AIRSIM" and executed in a time-sharing environment to assure their 
validity. When satisfied with the performance of all subroutines, the sub- 
routines were recombined and example problems were simulated with the de- 
tailed output of the model being continuously monitored. When it was concluded 
that the model performed as intended, the question of duplicating real world 
results was addressed. 

During initial validations, data collection exercises played a large part 
in determining that "AIRSIM" did, in fact, duplicate the real world operations 
of the system modeled. Statistics such as runway occupancy times, taxi times, 
queue lengths, and operations actually processed were gathered at O'Hare Inter- 
national Airport while operations were conducted in various configurations. 
These statistics were then compared to the statistics "AIRSIM" produced when 
simulating the same configurations as observed. When analysts were satisfied 
that the real world system was being duplicated, conferences were held with 
FAA personnel who further verified the results. 



The most stringent validation for any simulation model is that of subject- 
ing it to close examination by other professionals who understand both the sys- 
tem modeled and the simulation techniques employed. The O'Hare delay taskforce 
provided an extremely rigorous validation test which was conducted to the satis- 
faction of Federal Aviation Administration and airline technical representatives 
participating in the O'Hare Delay Taskforce. The entire model logic was first 
examined. As a result of this logic review several airline suggested improve- 



B-26 



ments were incorporated into "AIRSIM." Subsequently, United Airlines supplied 
detailed actual hourly reported delay and throughput statistics for comparisons 
with the model output. The model was again found to produce reasonable and 
accurate results down to the level of individual airline performance. The results 
of this taskforce validation effort are described in the paragraphs which follow 
and presented in Exhibits B-7 through B-13. 

Two separate validation efforts based upon O'Hare Configuration 1 (arriv- 
als on 27R and 32L, departures on 27L and 32R) in visual flight rules (VFR) 
weather conditions were undertaken for "AIRSIM". The first was based upon 
actual observed data in January, 1975 and the second on an updated September, 
1975 schedule (when it was decided to switch) . Both exercises produced a close 
correlation with observed value. For the purpose of this discussion, only the 
results of the January validation are presented. Exhibits B-7 and B-8 pre- 
sent a comparison of "AIRSIM" arrival and departure throughput by hour versus 
three days in January and the three day average when O'Hare was operating in 
Configuration 1 in VFR weather conditions. Note not only the close correlation 
of volumes processed but also the similarity of pattern by hour. Exhibit B-9 
presents a comparison of total system arrivals by hour by individual arrival 
runway. The close correlation of volume and pattern shows the model is prop- 
erly addressing the allocation of arrival demand by runway. Exhibits B-10 
and B-12 present tabulations of actual United Airlines reported arrival and de- 
parture delays for three VFR #1 days in January; with the adjustments noted to 
gain consistency with the model delay definitions, a target delay was established. 
Exhibits B-11 and B-13 present a comparison of these United target delays with 
"AIRSIM" output for United. Both the pattern and level of average delay are re- 
markably similar with the "AIRSIM" delay values fall entirely within the range 
of delay observed on the three actual days. The United delay data was consid- 
ered representative of the total airport by the taskforce since United's opera- 
tions account for approximately 22 percent of the total airport operations. 

The taskforce concluded from this evaluation and from thorough examination 
of the model logic that "AIRSIM" produced a very reasonable representation of the 
real world. 



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APPENDIX C 

AN OVERVIEW OF "CATESIM" 
THE APRON/GATE SIMULATION MODEL 



Developed by: 

Landrum & Brown 
Airport Consultants 



For: 



The Department of Aviation 

City of Chicago 

Chicago, Illinois 



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APPENDIX C - "GATESIM" 



The purpose of this appendix is to present a general description of 
the apron/concourse simulation model "GATESIM", developed by Landrum & 
Brown for the City of Chicago's Department of Aviation. The document is 
abstracted from the first of five proprietary volumes which, together, completely 
describe the model. This abstract addresses five key areas: 

Background, 

Model Development Objectives, 
"GATESIM" Conceptual description, 
"GATESIM" Model Description, and 
"GATESIM" Validation. 

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

1. BACKGROUND 

In 1972, the City of Chicago requested that Landrum & Brown develop 
an apron/gate simulation model for the purpose of evaluating alternative 
concourse expansion programs. The alternatives included an extended con- 
course versus a chevron concept of gate expansion for O'Hare's apron/con- 
course system. 

After a thorough literature search and review of existing techniques 
for evaluating apron/concourse systems it was determined that: 

No quantitative techniques existed which fulfilled all of 
the City's requirements. 

Digital computer simulation offered the most efficient, 
cost-effective means of problem solution. 

Therefore, a program was initiated to construct a high speed, stochastic, 
event sequenced, apron/concourse simulation model for the Department of 
Aviation, City of Chicago. The project resulted in the development of a planning 
tool which enables the City to evaluate the O'Hare apron/concourse system under 
various conditions of apron/concourse facilities arrangement, schedule demands, 
operational characteristics of the apron/concourse facility, and taxiway con- 
figurations. The model may be used to simulate the system's response to any 
volume/fleet mix combination of aircraft demand whiqh may be imposed on the 
system. 



C \3s 



With the model the City's planners are now able to observe the apron/ 
concourse system's operation (by analyzing the simulation output) and assess 
the implications of alternate physical, procedural, or activity changes on 
the O'Hare apron /con course system. 



2. MODEL DEVELOPMENT OBJECTIVES 

The objective of the "GATESIM" development program was to prepare an 
analytical tool for the purpose of assessing the O'Hare apron/gate complex 
system performance and to provide quantitative measures of the operational 
aspects of alternate development options; these measures to be used as 
input to the benefit/ cost evaluation process. A survey was conducted for 
material on operational aspects of the O'Hare apron/concourse system. This 
information was reviewed and furnished the basis for the simulation model's 
conceptual design. Examination of the O'Hare system indicated that a detailed 
analysis of the following factors would be necessary to successfully develop 
the apron /concourse simulation model: 

Aircraft Maneuvering Characteristics 

Apron/Concourse Geometry 

Aircraft Performance Characteristics 

Gate Scheduling Procedures and Requirements 

Further, as input to the benefit/ cost evaluation process, it was concluded 
that the technique developed should provide the analyst with the following 
measures of system effectiveness: 

Average Maneuvering Delay Per Aircraft 

Inbound 
Outbound 

Occupancy Related Delay 

Daily Penalty Box Contents 

Average Penalty Box Hold Time 

Daily Delay Costs 

The resulting model, "GATESIM", is described in the following section. 



C-2 



3. "CATESIM" CONCEPTUAL DESCRIPTION 

The elements of the Chicago O'Hare apron/concourse system as defined 
in the "CATESIM" model are described in this section. These include: 

System Boundaries 

Entities and Events 

Variables 

Decision Processes 

Data Input Requirements, and 

Measures of Effectiveness (Model Output) . 

Each of these is discussed in the following paragraphs. 

(1) System Boundaries 

The outer most limit of the system modeled is the outer taxiway 
at O'Hare. The inner most limits of the system are the entire 
domestic and international gate facilities located on the concourses 
of the O'Hare Terminal. The simulation does not track or 
follow aircraft before entrance or after exit from these system 
boundaries. The physical characteristics of the apron/concourse 
system are depicted in Exhibits C-1 through C-3. The apron/con- 
course system is defined by the following elements: 

Taxiway Blocks - A division of the inner and outer 
taxiway structure used to simulate the movement of 
aircraft. For simulation purposes the taxiway 
structure is divided into taxiway blocks that are 
large enough to hold an aircraft but too small to hold 
more than one aircraft. The movement of an aircraft 
is simulated by moving an aircraft from block to block 
along the taxiway. The taxiway blocks are given 
relative numbers for simulation purposes. The number 
of the taxiway block on the inner taxiway is the 
same as the number of the block on the outer taxi- 
way that is opposite it. 

Entry/Exit Blocks - A position from which an aircraft 
may proceed onto or exit from the taxiway structure. 

Taxiway Crossover Block - Is a taxiway block that 
connects the inner and outer taxiway structures. 

Flow Channel Blocks - The flow channel or Cul-De-Sac 
is the maneuvering area of the airport apron located 
between or adjacent to the fingers of the terminal 



C-3 




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C-6 






building. A flow channel block is a division of the 
flow channel used to simulate the movement of air- 
craft. For simulation purposes the flow channel is 
divided into blocks that are large enough to hold 
an aircraft, may be wide enough to hold two aircraft 
(if passing permits), but are too small to hold more 
than two aircraft. The movement of an aircraft in 
the flow channel is simulated by moving an aircraft 
from block to block. The flow channel blocks are 
given relative numbers with the block nearest the 
inner taxi way having the largest number. 

Inbound/Outbound Crossover Points - A relative 
position number from which an aircraft enters or 
leaves a flow channel. This number is equal to 
the relative number of the taxiway block that is 
adjacent to the flow channel . An inbound crossover 
point is the position from which an aircraft crosses 
from the inner taxiway to the flow channel and it 
is equal to the relative number of the taxiway block 
from which the aircraft will maneuver. An out- 
bound crossover point is the position from which an 
aircraft crosses from a flow channel to the inner taxi- 
way and it is equal to the relative number of the taxi- 
way block into which the aircraft will maneuver. The 
inbound and outbound crossover points for a gate position 
should not normally be equal. If they are equal, the 
passing permissions in the flow channel may prevent 
the aircraft from maneuvering properly. They will be 
equal, however, for a gate that parks and unparks 
directly from the taxiway. 

Parking Blocks - A parking block for a gate is a 
position where an aircraft can receive service. A 
parking block is located within a flow channel block 
and it carries the same number as the flow channel 
block, i.e., if gate number one for an airline is 
physically located along terminal finger D, and the 
aircraft must maneuver into flow channel block 
number two in order to get to the gate, the gate has 
a parking block of two. 



C-7 



(2) Entities and Events 

The entities or items of central interest In the Apron /Concourse 
simulation are the aircraft moving into and out of the system. In 
addition, aircraft are further defined by airline and major aircraft 
ground performance characteristics. These types were the B-747, 
DC-10/L1011, 4 engine "stretch" fan, H engine jet, 3 engine "stretch", 
3 engine jet and 2 engine jet and turbo-prop aircraft. The airline 
and aircraft types used in the simulation are presented in Exhibits 
C-4 and 5, respectively. 

An event is a particular function or activity an aircraft must 
perform while maneuvering in the apron/concourse system. The 
following events are performed by all aircraft entering the system: 

Arrival 

Check Cate Assignment 

Taxi to Cate 

Park 

Service \j 

Tow into Flow Channel 

Power Out to Flow Channel 

Depart System 

These activities are required of each aircraft in the system and 
are performed sequentially. 

(3) Variables 

Variables in the "CATESIM" model include both decision 
(controllable) and uncontrollable variables. Decision variables are 
those variables of the system under direct control by the analyst 
and uncontrollable variables are those over which the analyst 
has no controj. Examples of decision variables are: 

Taxi way Entrance/Exit Locations 
Cate Locations 
Concourse Geometry 
Parking Restrictions 
Aircraft Passing Restrictions 

Examples of uncontrollable variables are: 

Airline Schedule 
Early/Late Arrivals 
Aircraft Service Delays 



C-8 



Code No. 


1 


2 


3 


4 


5 


6 


7 


8 


9 


10 


11 


12 


13 



Airline (Parking Location 



International 

Continental 

Northwest 

Braniff 

Eastern 

United 

Ozark 

TWA 

Air Canada 

North Central 

Delta 

American 

Allegheny 



IN 

CO 

NW 

BN 

EA 

UA 

OZ 

TW 

AC 

NC 

DL 

AA 

AL 





W} 



C-9 



Numeric Code 
For CATESIM 



5 
6 

7 v 



Description Type 



Four Engine HBPR Fan 
Three Engine HBPR Fan 
Four Engine "Stretch" Fan 
Four Engine Turbo Jet 



Four Engine Turbo Fan 



Three Engine "Stretch" Fan 
Three Engine Turbo Fan 
Two Engine Turbo Fan 
Two Engine Turbo-Prop 



Specific 
Type 

B-747 

DC-10; L-1011 

DC-8-61, 707-300 

B-707-120 
B-707, 320; B-72 
DC-8-20; DC-8-30 
CV-880 

B-707- 120B 
B-720B 
DC-8-40 
DC-8-50', DC-8-62 

DC-727-200 

B-727-100 

B-737; DC-9 

CV-580; FH-227 



h 



9 

i 

j 
u 



C-10 



(4) Decision Processes 

The decision processes within the "AIRSIM" model include 
the operating procedures in effect within the apron/concourse 
system at O'Hare International Airport as of November, 1975. 
These include directional flow of aircraft on the inner and outer 
taxiway. This flow is either clockwise or counterclockwise on 
the outer taxiway and the reverse on the inner taxiway. The flow 
is determined by the runways in use at the airport. Other decision 
processes are internal to the model . These are: 

Rules used for placing aircraft in the penalty box 
and rescheduling the aircraft to another gate: 

The following decision process is applied 
to all aircraft arriving at the system. 

"■- -If an aircraft arrives at the system 
and its "preferred" gate is available 
the aircraft will proceed to its gate. 

t- If an aircraft arrives at the system 
and its "preferred" gate is unavailable 
but the aircraft currently holding the 
gate is scheduled to depart the system 
within five minutes, the arriving air- 
. craft will be sent to the penalty box 
and try to enter the system after 
the aircraft holding the gate is scheduled 
,.-,„ to depart. 

— If an aircraft arrives at the system and 
• : 7' .'*-■. ,ts "preferred" gate is unavailable and 

the aircraft currently holding the gate 
is not scheduled to leave within five 
minutes, the aircraft will be "forced" 
into the compatible gate having the 
longest open period before next scheduled 
use . 

— If a smaller aircraft is being "forced" 
into a wide-bodied gate and a wide-bodied 
aircraft is due to arrive at that gate 
within the next ten minutes, the smaller 
aircraft will be assigned another gate, 

or be sent to the penalty box if no other 
gate is available. 



C-11 






— If no gate is available the aircraft will 
be sent to the penalty box and await 
the next available compatible gate. 

Rules used for gate assignment. 

The model simulates the dynamic gate 
permission restrictions which occur during 
gate scheduling. 

— Parking permission sets are defined 
for each gate based upon the aircraft 
types occupying the adjacent gates. 

— Each gate has a primary set of per- 
missions which identify all the possible 
aircraft types which may park in the 
gate. 

— Each gate has a set of restrictions based 
upon the aircraft types occupying the 
adjacent gates. 

— Both the permission set and the restriction 
set are checked before an aircraft is 
assigned to its gate. 

Rules Used for Path Selection 

All aircraft follow the flow convention in use at 
the time. Clockwise or counterclockwise on the 
outer taxiway and the opposite direction on the 
inner taxiway. 

Aircraft will cross between the circular taxi ways on 
the crossover pavement being used for its cul-de-sac. 

If aircraft can select another entry location it will 
choose the path of least congestion. 

Rules Used for Maneuvering Aircraft on the Apron System 

All aircraft are maneuvered from block to block 



C-12 



-- 50 block maximum division of the inner and 
outer circular 

-- Ten block maximum division of the cul-de-sac 

All aircraft must follow the flow convention in use on 
the circular taxiways. 

Aircraft may pass in cul-de-sacs which are wide 
enough to allow maneuvering. 

-- the simulation is told what aircraft types 
can pass other aircraft in each cul-de-sac 

— inbound aircraft may not pass inbound 

— outbound aircraft may not pass outbound 

— within the cul-de-sacs inbound aircraft have 
priority over outbound and tows 

— within the cul-de-sacs outbound aircraft have 
priority over tows 

Outbound aircraft within the cul-de-sac have priority 
over inbound aircraft still on the circular trying to 
enter the cul-de-sac. 

(5) Data Input Requirements 

In any simulation model of significant scope the data input requirements 
are quite large and if not well defined can be burdensome. In defining 
data requirements for GATESIM, physically similar inputs were gathered 
into four logical groups. The groups are defined as follows: 

Gate Permission File - The Apron/Concourse Simulation Model's 
Gate Scheduling Program has the capability of creating a 
schedule of aircraft, constrained by the available gate facilities. 
The three main data requirements needed to constrain the fore- 
cast are: 

Aircraft/Gate parking permissions or compatibilities 

Mean or average gate occupancy time for each airline/ 
aircraft type 

An early/late aircraft arrival time distribution. 



C-13 



These three data sets are required to develop a 
schedule of aircraft/gate locations list. This list 
is normally referred to as a "ramp chart". 

Aircraft Performance File - This data file consists 
of the basic distribution functions related to aircraft 
performance on the ground. The main data time 
requirements are: 

Intra- line connection 

A gate occupancy distribution 

An inbound taxiing distribution 

An outbound taxiing distribution 

A tow out distribution 

A departure delay distribution 

Each of these distributions are described as cumulative 
percentage distributions of the time required to perform 
each of the above functions. These distributions are 
normally described both by aircraft type and airline. 

Geometric File - The geometric data file described the 
physical dimensions of the system to be simulated. It 
includes the following main requirements: 

The division of the taxiway structure into 
maneuvering blocks 

The locations of the entry and exit points for the 
taxiway 

The passing permissions within the cul-de-sac 

The location of double parked gates 

The location of airline shared gate positions 

The location of gates that may obstruct the taxi- 
way when departing 

j 
The identification and location of each airline's 
gates 



C-\H 



The division of each flow channel into maneuvering 
blocks 

The identification of entry and exit points for each 
cul-de-sac 

This data file is normally created on the basis of existing 
or proposed facility layout plans. 

Arrival/Departure Schedule - This file is the demand input 
for the Apron/Concourse Simulation. It is normally obtained 
from either the "Official Airline Guide" or is developed on 
the basis of some forecasting algorithm. It is feasible to 
accept this schedule from the output file of L&B's airspace 
simulation. The schedule is then used as input to the 
simulation model's Gate Scheduling Program, GATSKED, which 
constrains the schedules to the gate facilities available. This 
demand file is then imposed on the Apron/Concourse Simulation 
for evaluation of alternative facility designs. 

(6) Measures of Effectiveness 

? The measures of effectiveness used in the apron /con course 
simulation are of three basic types. These types are: 

Maneuvering related delays 

Gate related delays 

System performance statistics. 

The maneuvering related measures are defined as follows: 

Inbound Maneuvering Delay 

Taxiway Delay - Delay incurred by an 
arrival trying to maneuver on the inner or 
outer taxi ways. 

Crossover Delay - Delay incurred by an 
arrival trying to maneuver from a crossover 
block between the inner and outer taxiways. 

Flow Channel Delay - Delay incurred by an 
arrival trying to maneuver into or in a 
cul-de-sac. 



C-15 



Inbound Congestion Delay - Delay incurred 
by an arrival held outside the system due to 
congestion around its cul-de-sac. 

Outbound Maneuvering Delay 

Taxiway Delay - Delay incurred by a departure 
trying to maneuver on the inner or outer taxiway. 

Crossover Delay - Delay incurred by a departure 
trying to maneuver from a crossover block between 
the inner and outer taxiways. 

Flow Channel Delay - Delay incurred by a departure 
trying to maneuver in a cul-de-sac. 

Outbound Congestion Delay - Delay incurred by a 
departure held at its gate because of congestion 
in its cul-de-sac. 

The gate related measures are defined as follows: 

Occupancy Delay - Delay incurred by an inbound aircraft 
due to unavailability of a gate location. 

Penalty Box Data 

Penalty Box Count - Total number of aircraft 
entering the penalty box over the time simulated. 

Average Penalty Box Time - Total accumulated 
time of all aircraft in the penalty box divided 
by the number of aircraft entering the penalty 
box. 

Gate Utilization - The gate utilization of an airline is 
calculated by summing for each gate used by that airline 
the number of minutes the gate was occupied, divided 
by the total time simulated. 

Ramp Chart - The ramp chart is a graphical means of 
tracing the gate usage of each airline over the simulated 
period. The ramp chart indicates the gate positions, 
the flight number and type of aircraft in the gate, and 
the time the aircraft occupied the gate. 



C-16 



^<<HsSSiJB 



The system performance measures include the fo! Sowing: 

Aircraft Fleet Mix - The percentages of each aircraft 
type processed by the simulation. 

Aircraft Arrival Histogram - The total number of air- 
craft processed by the system . 

System Arrival Performance - A measure of the early 
and late arrivals the apron/concourse system. 

Gate arrival Performance - A measure of the early/ late 
arrivals at the gate. 

Gate Departure Performance - A measure of the on-time 
and late departures. 

Average Time Arriving - The time it takes an aircraft to 
enter the system and maneuver to its assigned gate. 

Average Time departing - The time it takes an aircraft 
to tow-out of its gate an maneuver out of the system. 

Aircraft Delay Costs - Cost to all airlines calculated on 
the basis of delays incurred by aircraft in the apron/ 
concourse system. 

4. "GATESIM" PROGRAM DESCRIPTION 

The development of the GATESIM model emphasised construction of 
a computer simulation which was usable by a person without extensive knowledge 
of computer operations. The resulting model consists of three basic program 
units: 

Input Unit 
Aircraft Processor 
Output Unit. 

These elements are depicted diagrammatical ly in Exhibit C-6, and 
described in the following paragraphs. 



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C-18 



The Input Unit - The function of the Input Unit is to develop 
an aircraft/ gate schedule. As such the input unit requires 
a schedule of demand by airline, aircraft and time of arrival 
and departure from the gate area. Secondly, the input unit 
requires a complete description of the apron/concourse system, 
The apron concourse facility is described in three groups, 
namely, gates, taxiways, and operational characteristics. 
These groups are described as follows: 

Gate Facilities 

— Number of gates for each airline. 

— Dimensions of each gate which limits the 
use of that gate to specified aircraft types. 

— Gate permission lists. 

— Gate/cul-de-sac assignments which spatially 
locates the gate geometry. 

— Cul-de-sac subdivisions with associated gate 
locations. This dimension will allow aircraft 
to pass in the cul-de-sac whenever feasible. 

— Double parking capacities for an airline. 

— Specification of gates which will tow aircraft 
into the inner taxiway whenever operationally 
required. 

Taxiways 

-- Entrance/exit locations to outer taxiway 

— Outer taxiway subdivisions (maximum of 50) 

— Crossover points between the outer taxiway 
and the inner taxiway 

-- Inner taxiway subdivisions (50 maximum) 
which are of similar size and purpose as the 
outer taxiway subdivisions. 

— Entry/exit locations for each cul-de-sac. 



C-19 



Operational Characteristics 

— Flow control, described as either counterclock- 
wise or clockwise, for the outer taxi way. The 
inner taxi way operates in the opposite direction. 

— Aircraft look ahead feature, which enablee the 
simulation to know the actual arrival time of 
aircraft in advance for a specified period 
(usually one hour) . 

The input unit will then calculate an associated gate assignment list for 
each aircraft. 

The Aircraft Processor - This is the unit of the simulator 
that reproduces the operation of the apron /concourse 
system. To accomplish this function, it determines (by 
Monte Carlo methods) the identity, characteristics, precise 
time of arrival and entry location of each succeeding aircraft 
that enters the apron/ concourse system. Prior to entry of the 
system the aircraft checks for its assigned gate's availability. 
At this decision point the aircraft will: 

proceed to its designated gate, 
proceed to a rescheduled gate, or 
wait in the penalty box. 

When an aircraft is cleared to maneuver to its gate, it checks 
the flow control of the outer taxi way . It then proceeds into 
the taxiway system and maneuvers through the system on a 
block to block basis. The aircraft will stop whenever the 
block in front of it is occupied. The aircraft continuously 
checks for the turn-in point to its assigned cul-de-sac and 
will initiate this maneuver when appropriate. Within the cul- 
de-sac the aircraft will check for passing capability whenever 
required and will halt whenever it will obstruct the taxi lane. 
Once the aircraft arrives at its gate and has received service, 
it will initiate a similar set of checks in order to depart the 
system. In order to move through the apron/concourse system, 
an aircraft proceeds through a series of events. These events 
are: 

Aircraft arrival and assignment of an entrance location 

Gate assignment check, leading to initiation of one of 
the following actions: 



C-20 



— Proceed to assigned gate 

— Proceed to rescheduled gate 

— Wait in penalty box. 

Aircraft maneuvers inbound 

Aircraft is receiving service 

Assignment of an exit location 

Aircraft moves into the flow channel for departure 

Aircraft maneuvers outbound 

Aircraft departure from the system. 

The aircraft processor will calculate and record for all aircraft 
the time of occurrence of all simulated events from entry into 
the system until exit from the system. 

Output Unit - The output unit calculates the measurements of 
system performance. These measurements include: 

Percent of gate uti I i zation 

Fleet mix of processed aircraft 

Histogram of the arrival rate by hour 

Total aircraft delay by: 

— Types of aircraft 

— Maneuvering related conflicts 

— Non-availability of gates 

Average time in penalty box 

Average delay /aircraft 

Average departure delay/aircraft 

Daily and annual delay cost 

Gates rescheduled for each airline 

Ramp chart of gate usage by airlines by flight. 



C-21 



Emphasis was placed on presenting information to planners 

in such a way that the outcomes of alternate development schemes 

for the Chicago apron/concourse system were easily interpreted. 



5. "CATESIM" VALIDATION 

To validate a simulation model two questions must be answered: 

Does the model perform as intended? 

Does the model's performance duplicate that of its real 
world counterpart? 

In answering the first question, all of the individual subroutines 
comprising the model were checked for logical correctness of the code. 
When analysts were satisfied with the logical performance of all of the 
subroutines, the question of duplicating real world results was addressed. 

During initial validations, data collection exercises played a large part 
in determining that "CATESIM" did, in fact, duplicate the real world operations 
of the system modeled. Statistics such as daily penalty box counts, average 
penalty box hold, taxi times, tow out times, and operations actually processed 
were gathered at O'Hare International Airport. These statistics were then 
compared to the statistics produced by "CATESIM". The model was found to 
produce reasonable and accurate results down to the level of individual air- 
line performance. 

A validation exercise was conducted for the Federal Aviation Administration 
and airline technical representatives participating in the O'Hare delay taskforce. 
The model was first examined and as a result, several airline suggested 
improvements were incorporated into "CATESIM". Subsequently, United 
Airlines supplied actual hourly reported throughput and maneuvering statistics 
for comparisons with the model output. The model again was found to produce 
reasonable and accurate results. The results of this taskforce validation effort 
are described in the paragraphs which follow and presented in Exhibits C-7 
through C-T». 

The validation effort was based upon visual flight rules (VFR) weather 
conditions using a Thursday schedule for September 1975. Exhibit C-7 presents 
a comparison of CATESIM air carrier operations processed versus three days 
in September and a three day average. Note not only the correlation of volumes 
processed but also the similarity of pattern by hour. Exhibits C-8 and C-9 
present a comparison of United Airlines processed arrivals and inbound 
maneuvering times versus the arrivals and inbound maneuvering times of oper- 
ations processed by CATESIM . 



C-22 



The close correlation of volume and pattern show the mode! to be 
producing reasonable statistics. Exhibit C-10 presents an outbound maneuvering 
time target, derived from United actual reported times, with adjustments noted 
to gain consistency with the model outbound maneuvering times. Exhibit C- i 1 
presents the CATESIM outbound maneuvering times for United Airlines and the 
total airport. Note the close correlation of average maneuvering time produced 
by CATESIM versus the target maneuvering time derived from United's reported 
times. Exhibit C-12 presents a comparison of penalty box contents for two 
Thursdays in September versus penalty box counts from CATESIM. The 
extremely volatile gate situation observed at the O'Hare complex makes 
comparison of penalty box contents and hold times by hour difficult. However, 
the total aircraft time accumulated in the penalty box and the average hold time 
per aircraft can be compared and were found to be within acceptable limits. 
Exhibits C-13 and C-14 present outputs of simulation maneuvering and occupancy 
delay displayed by aircraft type and by hour. 

It was concluded from this evaluation and from thorough examination of 
the model logic that "CATESIM" produced a reasonable representation of the 
real world. 



C-23 



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INBOUND 


MANEUVERING DELAY (li 


1 Minutes) 


Cross 


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Aircraft Type 


Taxiway 


Over 


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Total 


B-747 Q 


1.06 


.01 


.76 


1.83 


DC-10 7 


8.38 


.88 


8.76 


18.03 


4 Eng Super ^j H 


2.87 


.05 


1.52 


4.44 


4 Eng Stand 1 


10.30 


.83 


10.36 


21.49 


3 Eng Super u- 


24.10 


* .. v 88 


24.70 


49.67 


3 Eng Stand 3 


21.62 .86 


17.60 


40.08 


2 Ena t 


— -■ 28.37 «_/ 


1.11 


10.62 


40.43 


Total 


96.70 


4.95 


74.32 


175.97 




OUTBOUND MANEUVERING DELAY 


(In Minutes) 




Cross 


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Aircraft Type 


Taxiway 


Over 


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Total 


B-747 


.14 


.04 


1.03 


1.21 


DC-10 


1.78 


.08 


6.00 


7.86 


4 Eng Super 


.61 


.02 


.73 


1.36 


4 Eng Stand 


5.02 


.15 


6.42 


11.59 


3 Eng Super 


11.70 


.36 


17.31 


29.37 


3 Eng Stand 


13.12 


.74 


15.83 


29.67 


2 Eng 


14.18 


.59 


6.81 


21.58 


Total 


46.55 


1.98 


54.13 


102.66 




GATE RELATED DELAY (In Minutes) 


Gate 


Inbound 


Outbound 




Aircraft Type 


Occupancy 


Congestion 


Congestion 


Total 


B-747 


87.47 


8.05 


1.67 


97.19 


DC-10 


10.39 


26.69 


13.54 


50.62 


4 Eng Super 


0.00 


11.60 


2.99 


14.59 


4 Eng Stand 


11.72 


30.62 


26.72 


69.06 


3 Eng Super 


31.97 


37.83 


29.88 


99.68 


3 Eng Stand 


32.01 


27.49 


43.08 


102.58 


2 Eng 


54.39 


8.58 


58.16 


121.13 


Total 


227.95 


150.86 


176.04 


554.85 


Average Delay /Aircraft =1.32 






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a 


a 



C-30 



Hour? 

8- 9 
9-10 
10-11 
11-12 
12-13 
13-14 
11-15 
15-16 
16-17 
17-18 
18-19 
19-20 



Hours 

8- 9 
9-10 
10-11 
11-12 
12-13 
13-14 
14-15 
15-16 
16-17 
17-18 
18-19 
19-20 



INBOUND MANEUVERING DELAY (In Minutes) 

Flow 
Cross Over Channel Total 



Taxiway 

3.15 
9.74 
5.93 
6.08 

10.23 
9.18 
5.31 
7.07 

10.93 

11.24 
6.99 

10.84 



40 
,34 
.27 
.11 
.69 
.21 
.22 
.18 
.67 
.83 
.20 
.83 



1.95 
7.81 
4.86 
3.96 
5.25 
6.77 
6.62 
6.68 
10.54 
8.10 
3.53 
8.26 



5. 


50 


17. 


89 


11. 


06 


10. 


15 


16 


17 


16 


16 


12 


15 


13 


93 


22 


14 


20 


17 


10 


.72 


19 


.93 



OUTBOUND MANEUVERING DELAY (In Minutes) 

Flow 
Cross Over Channel Total 



Taxiway 

3.46 
4.28 
3.32 
4.45 
2.28 
3.27 
2.30 
4.76 
4.15 
3.99 
5.00 
5.30 



13 

15 

13 

10 

23 

.13 

.12 

.14 

.10 

.30 

.19 

.26 



2.06 
2.70 
3.24 
4.70 
3.09 
4.04 
4.55 
6.70 
3.21 
5.82 
8.86 
5.16 



5. 


65 


7. 


13 


6. 


69 


9. 


25 


5 


60 


7 


44 


6 


97 


11 


60 


7 


46 


10 


11 


14 


.05 




10.72 




Hours 

8- 9 
9-10 
10-11 
11-12 
12-13 
13-14 
14-15 
15-16 
16-17 
17-18 
18-19 
19-20 



Z-^7 



GATE RELATED DELAY (In Minutes) 

Inbound 
Occupancy Congestion 



.85 

9.36 

51.70 

5.90 

10.98 

4.69 

16.07 

15.53 

18.50 

14.70 

49.69 

29.97 



.24 

13.80 

16.84 

4.35 

10.26 

11.48 

6.66 

9.57 

20.97 

13.13 

21.70 

21.86 



Outbound 
Congestion 



10.77 
12.24 
22.43 
13.23 
13.07 
23.11 
10.07 
14.77 
15.12 
13.53 
14.55 
13.15 






Total 

11.86 

35.40 

90.97 

23.48 

34.31 

39.28 

32.80 

39.87 

54.59 

41.36 

85.94 

64.98 




C-31 



APPENDIX D 



FAA RUNWAY CAPACITY MODEL 



Prepared for: 
The Chicago Delay Taskforce 



Prepared by: 
Federal Aviation Administration 



M 



APPENDIX D 
FAA RUNWAY CAPACITY MODEL 



This appendix presents a discussion of the FAA runway capacity model 
used to produce the capacity analysis contained in this report. This appen- 
dix is divided into five sections: 



Background 
Objectives 
Model Concepts 
Software Description 
Validation 



BACKGROUND 



For several years, the Federal Aviation Administration (FAA) has been 
involved in a broad research program to develop reliable planning tools to 
quantify changes to the airport airside system. 

A method for estimating runway capacity was developed for the FAA in 
1960. Since then, widebody aircraft have been placed in service, new air- 
craft separation rules have evolved, and other changes in the air transporta- 
tion system have occurred. "Capacity", in the 1960 method, was defined as 
"that movement rate of aircraft which results in a reasonably acceptable aver- 
age delay to operations". It was found that this definition led to "capacity" 
flow rates that can be exceeded. 

In June, 1972, the FAA retained a project team to develop procedures 
for predicting airfield (i.e., runway, taxiway and gate) capacity and aircraft 
delay. The project team was headed by the Douglas Aircraft Company of the 
McDonnell Douglas Corporation and included Peat, Marwick, Mitchell & Co. 
(PMM&Co.), McDonnell Douglas Automation Company (MCAUTO), and American 
Airlines, Inc. Professor Robert Horonjeff of the Institute of Transportation 
and Traffic Engineering (University of California, Berkeley) served as a gen- 
eral advisor to the project team. 

In consultation with FAA and industry users, the project team selected 
a definition of capacity which is independent of delay . It was determined 
that capacity defined as the upper limit or maximum number of aircraft oper- 
ations that can occur would be a more natural and better understood concept. 
Recognizing the need to relate demand, capacity and delay in airport planning, 
the project team developed hourly delay curves which can be used to determine 
the average hourly delay per operation associated with airport specific capacity 
and schedule (i.e., demand and peaking within the hour) characteristics. 



btk 



The selected approach to the definition of runway capacity has several 
advantages. It allows the sponsor/planner to select the level of service; i.e. , 
average delay per operation, for which the airport will be designed (or will 
be permitted to operate) . It also provides a realistic hourly limit to the oper- 
ations rate for an airport. 

In support of the runway capacity model development, a comprehensive 
data collection program was carried out. Some 150,000 items of data were 
collected at 18 U.S. airports, including Chicago O'Hare, as part of this activ- 
ity. 

The capacity model was developed and validated during 1973-1974. 
Validation was carried out at three high capacity airports. 



Chicago-O'Hare International Airport (ORO) 

Dallas Love Field (DAL) (Using pre-DFW operations) 

Orange County Airport, Santa Ana, California (SNA) 



The validation process was performed to verify the logic of the capacity 
model. The validation process demonstrated that the model yielded aircraft 
flow rates within the desired accuracy. The availability of the capacity model 
in early 1975 led to its use by the Chicago Taskforce. 



OBJECTIVES 



The FAA runway capacity model provides a relatively quick and inex- 
pensive means to gauge the impact of changing airport conditions (i.e. , air- 
craft mix, weather, percent arrival, spacings, etc.) on airport operations. 
For this reason, it was selected by the Chicago O'Hare Taskforce to perform the 
following analysis: 



Determination of baseline capacities. This was used to 
develop the upper limit of present operational capability. 

Determination of future capacity. This served as a basis 
for studying which runway use configurations are best 
suited to accommodate future aircraft fleets, and to measure 
the incremental increase in capacity resulting from ATC 
automation. 



D-2 



MODEL CONCEPTS 



The principal output of the runway capacity model is hourly runway 
capacity. Hourly runway capacity is defined as the maximum number of air- 
craft operations (i.e. , arrivals and/or departures) that can take place on the 
runway in an hour under a specified combination of conditions. Hourly runway 
capacity depends on a number of conditions including, but not limited to, the 
following: 



Runway Use Configuration 

Aircraft Mix 

Percent Arrival 

Intersection Location, if runway centerlines cross 

Operating Conditions (IFR, VFR) 

Exit Location 

Human Factors 



Variations of any of these parameters may significantly impact runway capacity. 

The capacity values given in this report are the maximum flow rates that 
occur under saturation conditions. Capacity flow rates assume that arrival and/ 
or departure aircraft are available when needed to fill an operational slot. This 
would normally require that the queue of arrival and departure aircraft be always 
at least 1 . The capacity flow rates make no arbitrary assumption regarding 
"acceptable" delay per operation . Delays at capacity flow rates may vary from 
2 to 10 or more minutes per operation depending on the distribution of demand 
over the hour (i.e. , bunching) and length of time that demand rates are greater 
than capacity. 

The principal parameters incorporated in runway capacity are: 

Runway Use Configuration . Runway use configuration is a term 
used to categorize specific combinations of airfield geometry and 
operational use. 

The geometry includes: 

The number of runways in coordinated use. This 
identifies the unique combination of runways in use 
during some period of time. 



D-3 



Relative orientation of the runways; i.e., single, 
parallel, intersecting, etc. 

Separation; i.e. , distance between runway center- 
lines or from threshold to intersection. 

The operational use includes: 

The direction of operation on the runway. 

The kind of operations taking place on each runway; 
i.e., arrival only, departure only, or arrival and 
departure operations . 

Location of departure roll point; i.e., whereon 
the runway do departures start from? 

Aircraft Mix . Aircraft mix is defined in terms of four aircraft 
classes: A, B, C, and D. For the Chicago O'Hare capacity 
analysis, the following aircraft categorization was used: 

Class A includes single-engine propeller aircraft; 
twin engine propeller aircraft with gross takeoff 
weight less than 12,500 pounds; and Lear jets. 

Class B includes twin-engine propeller-driven 
aircraft with gross takeoff weight greater than 
12,500 pounds. 

Class C includes four-engine propeller aircraft 
and non-heavy jet aircraft (i.e., aircraft not cap- 
able of weights of 300,000 pounds) . 

Class D includes heavy jet aircraft (i.e., aircraft 
capable of weights of 300,000 pounds or more) . 

The model assumes a random distribution of these aircraft 
classes over the hour. The frequency with which any aircraft 
pair occurs is the product of the relative percentages for the 
respective aircraft classes. 

Percent Arrival . Percent arrival is defined as the percent of 
all aircraft operations that are arrivals. Pre-emptive priority 
is given to arrival operations in determining current capacity. 
In future Air Traffic Control environments, arrival and depar- 
ture operations were given equal priority for use of the runway. 



D-4 



Intersection Location . The location of the runway intersec- 
tion point from the threshold of the two runways affects sev- 
eral parameters of the model: 

Arrival-Departure Separation . ( AD). This is the 
time interval between an arrival crossing the runway 
threshold and a departure being cleared to roll. 

Departure-Arrival Separation . ( DA). This is the 
minimum distance an arrival can be from its thres- 
hold when a departure is released. 

In the case where the intersection distance on both runways 
is very long (i.e., approximately 7,000 feet or more) con- 
trollers will anticipate aircraft exiting the runway. Observed 
data for Chicago O'Hare runway pair 14R/27L show that con- 
trollers can determine that the arrival will exit before reaching 
the intersection by the time the arrival is approximately 4,000 
feet (i.e., 39 seconds) down the runway. Anticipation of exit- 
ing was used in the capacity model runs for runway pairs 14L/ 
9L, 14R/27L, 14R/9R, and 4R/9R. 

Operating Conditions . "VFR" and "IFR" are used in this ap- 
pendix to define sets of air traffic control procedures. 

VFR . VFR (visual flight rules) conditions occur 
when the ceiling is at least 1,000 feet and the visi- 
bility is at least 3 statute miles. A visual approach 
is an approach wherein an aircraft on an IFR 
flight plan operating in VFR conditions under con- 
trol of a radar facility and having an air traffic 
control authorization may deviate from the pre- 
scribed instrument approach procedure and pro- 
ceed to the airport by visual reference to the air- 
port or a preceding aircraft sequenced by ap- 
proach control. Visual approach conditions 
occur at Chicago O'Hare International Airport when 
the ceiling is at least 3, 500 feet and the visibility 
is at least 5 statute miles. In this report, aircraft 
are assumed to operate with visual approaches, 
weather permitting. Standard radar separation 
is provided by the control tower until the aircraft 
has been cleared for the visual approach. Longi- 
tudinal spacing is then determined by the pilots 
themselves on the final approach path. However, 
no two aircraft are permitted to operate on a single 
runway simultaneously. 



D-5 



IFR . IFR (instrument flight rule) conditions occur 
when the ceiling is less than 1,000 feet and/or visi- 
bility is less than 3 statute miles. The air traffic 
control separation standards specify the minimum 
spacing between all aircraft. In this report, "IFR" 
is defined as a ceiling of 200 feet and visibility of j 
statute mile. In this environment, no visual relief 
is permitted to the air traffic separation minimums. 
However, this analysis assumes that the controller 
is able to tell (by visual contact or electronics) when 
an arrival has landed on the runway. 

Exit Location . For each runway exit and aircraft type, the 
model requires the runway occupancy time (i.e., average 
elapsed time from over threshold to clear of exit) and exit 
probability (i.e. , the percent of a given aircraft type which 
will use a given exit) . These inputs are used to calculate 
the average runway occupancy time for each runway by air- 
craft type. 

Human Factors . The overall impact of human factors in 
combination with aircraft performance is considered by the 
model. This is done by selecting model inputs that reflect 
actual operating conditions. Specifically, measures of vari- 
ability which account for the combined interaction and per- 
formance of controllers, pilots and aircraft are included by 
the standard deviation ( a ) of: 

Arrival-Arrival Separation 
Arrival Runway Occupancy Time 
Departure Runway Occupancy Time 



4. SOFTWARE DESCRIPTION 



The runway capacity model is a series of algebraic equations that re- 
late the mean and standard deviation of the time required to perform a series 
of movements to an hourly increment of time. It is both deterministic and 
probabilistic in construction. The computational procedure is first to deter- 
mine the required separation between pairs of arrivals and then the arrival 
only capacity of the runway use configuration. With this information, the 
model determines the number of departure operations that can be interspaced. 
The arrival and departure capacities thus produced are then checked and 
adjusted as necessary to assure that the specified percent arrivals is produced, 



D-6 



The FAA Capacity Model contains logic to analyze over 150 runway use 
configurations. The software description that follows pertains to a pair of 
intersecting runways where arrivals use one runway exclusively and depar- 
tures use the other runway exclusively. AH reference to "the model" refers 
to this specific subset of the model. 

In determining the time separation between a pair of arrival aircraft at 
the runway threshold, the model takes into account: 



The required air traffic control separation by aircraft pair. 
This can be determined by data collection or assumed from 
the air traffic control procedure. 

The final approach velocity of each aircraft. 

If the trail aircraft is faster than the iead aircraft, 
the required arrival separation is ensured at the 
runway threshold. 

If the trail aircraft is slower than the lead aircraft, 
the required arrival separation is set up at the be- 
ginning of the common approach path (generally 
1 to 2 nautical miles beyond the outer marker) . 
The amount of time the trail aircraft falls behind 
is included in the time separation over threshold 
for this aircraft pair. 

Runway occupancy. Only one aircraft is permitted to occupy 
the runway at any given time. 

Missed approach. The model applies a buffer time to the 
minimum arrival separations to ensure a low incidence 
of controller intervention to prevent missed approaches. 



The model determines a time separation between a pair of departure air- 
craft which takes into account the required air traffic control separation by 
aircraft pair. This is used to set up 3, 4 or 5 nautical miles and increasing 
separations between light-light, heavy-heavy, and heavy-light departure 
aircraft pairs respectively, and to ensure a 2 minute hold after a heavy jet 
begins to roll. 

The model will permit a departure to roll on an intersecting runway 
(thus interspacing arrivals and departures) when all of the following conditions 
have been fulfilled: 



D-7 



The arrival aircraft has cleared the intersection or has 
exited. 

That at the time the departure begins to roll, the arrival 
is not within a distance DA of the arrival threshold . 
This departure-arrival separation DA is an input by 
runway pair. 

That the departure will clear the intersection before the 
arrival is over its threshold. 



If departure and arrival flight paths are projected to cross (i.e. , runway 
pair 32L/27L), the model ensures that an additional wake turbulence separation 
(currently 2 minutes) will be met whenever: 



A heavy departure would be followed by heavy or non- 
heavy arrival; 

A heavy arrival would be followed by a heavy or non- 
heavy departure. 



VALIDATION 



In order to have a reliable planning tool, the FAA required the McDonnell 
Douglas project team to demonstrate that the capacity model produced results 
within + 15 percent of observed saturation flow-rates. This was done to assure 
the soundness of the model concepts, to test the program coding, and to estab- 
lish the accuracy of the model results. 

In support of this activity, a data collection team headed by PMM&Co. 
collected movement data for 10 days at Chicago O'Hare International Airport 
during October, 1973. This data included: 



Arrival time over threshold 
Departure roll time 
Runway number 
Aircraft type 
Weather conditions 
Departure queue size 



D-8 



45s 



From this data base, intervals of time were selected that were judged to 
be saturated. Some factors that weighted on this judgment were: 



Departure queue size. Saturation conditions were assumed 
to exist, if the departure queue was always at least 1 . 

Length of time interval. Time intervals of 30 minutes or 
more were selected to eliminate distortions due to the 
averaging interval. 

Absence of operational gaps. Candidate saturation time in- 
tervals were inspected to assure that no unexplainable gaps 
in the flow occurred. For example, did departures roll 
after an arrival cleared the intersection, if all other ATC 
separations were fulfilled? 



The selected time intervals were analyzed for: 



Runway use configuration 

Aircraft mix 

Percent arrival 

Observed flow rate adjusted to an hourly base 



Figure 1 compares the capacity flow rates predicted by the model and 
observed flow rates for 11 data samples. The average difference between ob- 
served and calculated capacity for this data set is 3.9 percent. 



D-9 



FIGURE 1 

O'Hare Delay Taskforce Study 
OBSERVED VS. CALCULATED CAPACITY 



Data 
Sample 
(Number) 



1 

2 

3 

4 

5 

6 



1 
2 

3 
4 
5 



Observed 

Capacity 

(Op/Hr) 



Calculated 

Capacity 

(Op/Hr) 



RUNWAY PAIR 27R/32R in VFR 



76 
78 
80 
74 
78 
77 



78 
77 

75 
72 
75 
75 



RUNWAY PAIR 32L/27L in VFR 



65 
68 

72 
72 
66 



70 
69 
68 
69 
69 



Percent 
Difference 



- 2.6 
+ 1.3 
+ 6.2 
+ 2.7 
+ 3.8 
+ 2.6 



- 7.7 

- 1.5 
+ 5.6 
+ 4.2 

- 4.6 



D-10 



APPENDIX E 



IMPACT OF SHORT-TERM 
CAPACITY REDUCTIONS ON TOTAL AIRPORT DELAYS 



Prepared For: 
The Chicago Delay Taskforce 



Prepared By: 

United Airlines 
October 16, 1975 



£-7 



APPENDIX E 
IMPACT OF SHORT-TERM CAPACITY REDUCTIONS ON TOTAL AIRPORT DELAYS 



A reduction in the effective movement capacity at a busy airport, even 
for 30 minutes or one hour, during the peak demand periods can cause substan- 
tial backlog queues and lengthy delays to all flights over an extensive time per- 
iod following the initial disruption. At a major airport like ORD, such delays 
have increased the total fuel consumption by over 200,000 gallons and added 
over $100,000 in direct costs in one day. 



1, BACKGROUND 



During the early phases of the ORD Airport Capacity /Delay Taskforce 
effort, a review of historical data from the airlines indicated that the total de- 
lays incurred on some days were far in excess of the amounts that might be 
indicated by average steady-state analyses. 

The impact of short-term reductions in the effective movement capacity 
during peak demand periods had not been fully recognized, probably because 
of two reasons: 



The tower records show the number of movements handled 
by hour but do not show the number of movements held in 
backlogs, and 

The total demand (including the backlogs) was gradually 
reduced to reasonable levels prior to the build-up in traf- 
fic on the following day. 



The following analysis was undertaken in order to understand the rela- 
tionships between airport capacity and traffic demand and to quantify the po- 
tential impact of short-term reductions in capacity on total traffic delays. 



r 



<ljL 



2. 



TRAFFIC MOVEMENT DEMAND AT ORD 



Chart A shows the total demand for all aircraft movements (departures 
and arrivals) by hour of the day at ORD for a representative weekday (Monday 
through Friday) during January ,• 1975. It can be seen that the demand is low 
from midnight until 6AM, averaging only 17 movements per hour, but then 
builds up to an average level of 120 movements per hour between 8AM and 1PM. 
From 1PM to 8PM, the average demand is 135 movements per hour, which is 
equal to the quota, or rated airport capacity level. After 8PM, the demand 
falls to an average level of only 30 movements per hour from 10PM to mid- 
night. 



TRAFFIC MOVEMENT DEMAND AT ORD 



MOVEMENTS 
BY HOUR 














200 -| 












150 - 






- 






1 100 - 














••*% 










4i 




JSQ - 














'■":... 










s..„... 


d 


3 


6*m 


9 


12 


3 6pm 


» 


12 ' 



CHART A 



Midnight 



Noon 



Midnight 



The traffic demand curve for ORD reflects the preference of most pas- 
sengers to travel between 7AM and 8PM, rather than during the night hours. 
The shape of this curve is reasonably representative to the traffic demand 
curves for other major air carrier airports, with the exception that the after- 
noon peak is flattened and extended by the quota level of 135 movements per 
hour established for the five-hour period from 3PM to 8PM. 



E-2 



EFFECT OF REDUCTION IN CAPACITY FOR ONE HOUR 



Chart B 'llustrates the effect of a reduction on the airport capacity down 
to 80 movements for only a one-hour period between 12 noon and 1PM, when 
the traffic demand is 120 movements. The 40 movements not accommodated by 
1PM would be backlogged and added to the normal demand of 135 movements 
in the next hour. Even if the effective capacity were restored to 135-140 move- 
ments per hour from 1PM on, it can be seen that a backlog would progressively 
move into each succeeding hour until it would be finally worked out by 9PM, 
due to the lower normal demand of 85 movements between 8PM and 9PM. 



EFFECT OF REDUCTIONS IN CAPACITY FOR ONE HOUR 



MOVEMENTS 
BY HOUR 



200 n 



BACKLOG 




CHART B 



Midnight 



Noon 



6pm 9 12 

Midnight 



It should be recognized that the aircraft subject to delays are not limited 
to the initial 40 movements backlogged at 1PM, but rather that over 1, 100 move- 
ments from 12 noon until 9PM are subjected to the compounding delays of vary- 
ing durations. 



E-3 



4. 



EFFECT OF REDUCTION IN CAPACITY FOR SEVERAL HOURS 



Chart C illustrates the effect of a reduction in the effective capacity to 
120 movements per hour from 1PM on. The 15 movements backlogged from 
1PM to 2PM raised the total demand in the next hour to 150 movements, or 30 
in excess of the reduced capacity. The 30 movements backlogged from 2PM 
to 3PM raised the total demand to 165 in the next hour, or 45 in excess of the 
reduced capacity. Similarly, the compounding demand would snowball to 
225 at 8PM before the reduced normal demand would permit the backlog to be 
gradually eliminated by 11PM. 



EFFECT OF REDUCTION IN CAPACITY FOR SEVERAL HOURS 



MOVEMENTS 
BY HOUR 

200 -i 




CHART C 



All flights from 1PM until 11PM would be subjected to the compounding 
traffic delays of varying durations. 

Although this type of chart gives some indication of the impact of reduced 
capacity on backlogs and delays, it does not show the maximum delays suffered 
nor the total hours of delay incurred. In order to determine this information, 
it is convenient to show the daily movement demand and capacity in cumulative 
numbers from midnight to midnight. 



E-4 



CUMULATIVE TRAFFIC MOVEMENT DEMAND AT ORD 



Chart D shows the cumulative demand for movements, starting at mid- 
night, increasing by an average of 17 movements per hour until 6AM, then 
building up to an average rate of 120 movements per hour from 8AM to 1PM, 
increasing to an average of 135 movements per hour from 1PM to 8PM, and then 
increasing at a reduced rate of 30 movements per hour from 9PM until midnight. 



CUMULATIVE TRAFFIC MOVEMENT DEMAND AT ORD 



TOTAL 
MOVEMENTS 

2,000 "l 



1.500- 



1.000 



500- 




-i 1 r 

3 6am 9 12 3 

Midnight Noon 



i 1 1 r 

6pm 9 12 3 6am 

Midnight 



CHART D 



This chart shows the same information as Chart A, but in a cumulative 



count. 



E-5 



IMPACT OF 3-HOUR REDUCTION IN CAPACITY (ILLUSTRATIVE 
EXAMPLE) 



Chart E utilizes the cumulative movement demand curve of Chart D but 
also shows the situation that would develop if the effective capacity were re- 
duced from 135 movements per hour (equal to the normal demand) to only 95 
movements per hour for the three-hour period from 1PM to 4PM, before the 
capacity were restored to the standard 135 movements per hour. 

The length of individual flight delays is shown by the horizontal dis- 
tance between the cumulative demand and capacity curves, starting with zero 
delay at 1PM, but building up to 54 minutes by 4PM, and then continuing at 
54 minutes until 8PM, when the normal demand falls off. 

The number of flights backlogged is shown by the vertical distance be- 
tween the cumulative demand and capacity curves, again starting with zero 
backlog at 1PM, but building up to 120 by 4PM (= 40 deficiencies per hour x 3 
hours), and then continuing at 120 until 8PM, when it would gradually be 
worked out. 



IMPACT OF 3-HOUR REDUCTION IN CAPACITY 
(Illustrative Example) 



TOTAL 
MOVEMENTS 

2.000T 



1.500 



l.ooo- 



500- 




120 Backlog 
54 Min. Delay 



3 

Midnight 



— i i 

12 3 

Noon 



— r- 

6pm 



-i 1 r 

« 12 3 

Midnight 



CHART E 



6am 



E-6 



In order to show the total delay hours involved, the shaded area of 
Chart E is shown on Chart F with expanded scales. 



POTENTIAL TOTAL DELAY HOURS 



MOVEMENTS 
150H 



100- 




CHART F 



50- 



DEFICIENCY 
3 HOURS 



PERIOD 
6 HOURS 



TOTAL 780 HOURS 

OR 

AVERAGE OF 47 MINUTES FOR 1.000 MOVEMENTS 



A deficiency of 40 movements per hour for 3 hours would build up to 
a backlog of 120 movements. The triangular area represents the delay hours 
accumulated by the end of 3 hours, or 180 hours (equal to J x 3 x 120) . If 
the effective airport capacity were then increased to 155 movements per hour 
(or 20 greater than the normal demand), the backlog would be gradually reduced 
to zero after 6 additional hours (= 120/20), but an additional 360 hours of delay 
(equal to i x 6 x 120) would be accumulated in the process for a total of 540 
hours. 

On the other hand, if at the end of the three-hour reduced capacity period, 
the effective airport capacity were restored only to the standard 135 movements 
per hour, equal to the normal demand, the backlog would continue at 120 move- 
ments until the end of the day, accumulating an additional 240 hours of delay for 
an overall total of 780 hours of delay, or an average of 47 minutes for all the 
flights involved. 



E-7 



7. POTENTIAL BACKLOG QUEUES AND TO TAL DELAY HOUR 

The table of Chart C generalizes the impact of various reductions in 
effective capacity for different durations, in terms of the potential backlog 
queues, the maximum delays for individual flights, and the total hours of 
delay incurred under several recovery conditions. 





POTENTIAL BACKLOG QUEUES AND TOTAL DELAY HOURS 


MOVEME.VTS'HR. 


LENCTH 
OF TIME 
(HOURS! 


POTENTIAL 

BACKLOG 

QUEUE 


MAXIMUM 

DELAY 
<HRS:MINS> 


POTENTIAL TOTAi DELAY HOURS 


ACTUAL 
CAPACITY 


SHORT- 
AGE 


RECOVERY RATE 


NO RECOVERY 


-20fMH «10M/H 


2 HRS. 4 HRS. 






2 


20 


10 


30 40 


60 100 


125 


-10 


4 


40 


:20 


120 160 


160 240 






6 


60 


:30 


270 360 


290 410 






2 


40 


:20 


80 120 


120 190 


115 


-20 


4 


80 


:40 


320 480 


300 460 






6 


120 


100 


720 


790 1030 






2 


60 


:30 


150 240 


170 290 


105 


-30 


4 


120 


1:00 


600 960 


430 670 






6 


180 


1:30 


1350 


1140 1500 






2 


80 


:40 


240 400 


220 380 


95 


-40 


4 


160 


1:20 


960 


870 1 190 




J 


6 


240 


2:00 


- 


990 1470 



CHART G 



For example, a deficiency of 20 movements per hour for 6 hours would lead to 
a 120-airplane backlog, with a maximum delay to a flight of 60 minutes, and 
720 hours of delay incurred if the recovery rate were 20 movements per hour 
above rated capacity (135 + 20 = 155 movements per hour) . If the capacity 
were restored only to standard (no net recovery), the total hours of delay 
would compound to 1,030 if the maximum backlog were reached 1 hours before 
the normal demand fell off in the evening hours. 

The impact of these delays due to short-term capacity reductions should 
also be measured in terms of additional fuel consumption and increased direct 
costs . 



8. AVERAGE DELAY COSTS AND FUEL CONSUMPTION RATES 



Chart H summarizes the average direct costs and fuel consumption per 
minute for various air carrier aircraft, for ground operations and airborne. 
It can be seen that the direct costs of a one-hour traffic delay can range from 
$300 to $1,500, and that the fuel consumption can range from 2, 100 pounds 
(or over 300 gallons) to over 20,000 pounds (or 3,000 gallons) per hour. 



E-8 



AVERAGE DELAY COSTS & FUEL CONSUMPTION RATES 
AMERICAN / UNITED 



AIRCRAFT 

6-747 

DC-10 
DC-8/B-707 
B-727 
B-737 



(5-13-75) 






DIRECT COSTS PER 


FUEL CONSUMPTION ILBSt 


MINUTE OF DELAY* 


PER MINUTE OF DELAY 


Ground Airborne 


Ground 


Airborne 


$13.30 $25.20 


125 


345 


10.00 17.00 


65 


205 


8.00 13.20 


75 


170 


6. 49 10. 10 


55 


125 


5. 10 7. 50 


35 


75 



CHART H 



• Includes crew time over schedule, maintenance, fuel, and oil. 



A short-term reduction in effective movement capacity that results in 
a total compounded traffic delay of 200 hours can consume over 200,000 gallons 
of critical fuel and increase direct costs by over $100,000 in one day. 



IMBALANCE BETWEEN AIRPORT MOVEMENT CAPACITY AND DEMAND 



This analysis was primarily directed toward a better understanding of 
the relationships between airport capacity and traffic demand and a method 
for quantifying the impact of short-term disruptions. However, it should be 
recognized that there are many possible causes for such reductions in capacity 
below the rated runway acceptance rates (or Engineered Performance Standards) 
Among these causes are: 

Airfield construction work, especially runways and taxiways. 

Increased in-trail separations because of visibility and/or 

wake turbulence. 

Lower capacity runway configurations due to wind and weather 

conditions or for noise abatement. 

Changing from one runway configuration to another during 

peak periods. 

Inoperative or malfunctioning landing systems, lighting, etc. 

Squall lines or storms in the immediate area. 

Accidents on the airport. 



E-9 



A similar analysis has shown that relatively small increases in aver- 
age traffic demand, of only 5 to 10 movements per hour in excess of the effec- 
tive airport capacity, can also substantially increase the total delays for all 
flights during the overloaded period and all succeeding flights until the back- 
log is eliminated. 



10. CONCLUSIONS 



A reduction in the effective movement capacity of an airport 
during peak demand periods, even for short time durations, 
can cause substantial backlog queues and extensive com- 
pounded delays. 

In view of the potential impact on fuel consumption and di- 
rect costs, it is essential that disruptions in the effective 
airport capacity be minimized, and that the traffic demand 
be controlled in balance by such measures as the following: 

Performing runway work at night during off-peak 
traffic seasons. 

Limiting runway configuration changes during the 
peak traffic demand periods. 

Effectively monitoring the actual airport movement 
capacity during peak hours, including runway 
configurations employed and actual average sepa- 
rations. 

Controlling the actual traffic demand within quota 
limits under all weather conditions. 

The potential fuel and cost impact of capacity disruptions can be 
reduced by flight consolidations and/or cancellations, and it 
may be reduced by improved techniques for forecasting changes 
in effective airport capacity and the development of a practical 
and equitable system for holding traffic on the ground at upline 
stations when the effective airport capacity is limited. 

Considerations should be given to segregation of airport type 
(heavy, standard, light) by runway or airport and the possi- 
ble justification for a "maintenance" runway for ORD. 



E-10 



APPENDIX F 



CAPACITY IMPACT OF FAA ENGINEERING 

AND DEVELOPMENT 

ON CHICAGO O'HARE INTERNATIONAL AIRPORT 



Prepared for: 
The Chicago Delay Taskforce 



Prepared by: 

The Mitre Corporation 

April 15, 1976 



H 



APPENDIX F 

CAPACITY IMPACT OF FAA ENGINEER8NG AND DEVELOPMENT 
ON CHICAGO O'HARE INTERNATIONAL AIRPORT 



INTRODUCTION 



The analysis presented here provides the best current estimates of the 
capacity impact of the various elements of the FAA Engineering and Develop- 
ment (E&D) program on the operations at Chicago O'Hare International Airport 
(ORD) . The operating conditions at ORD are impacted only by the E&D ele- 
ments relating to a high density major hub airport. Consequently, other ele- 
ments of the E&D program, e.g., Aeronautical Satellite (AEROSAT) , Flight 
Service Stations (FSS) have not been analyzed. For an overview and a full 
description of the elements of the FAA E&D 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, March 1975" (Reference 1) . 
The primary purpose of this analysis is to estimate capacity improvements and 
capacity recovery (prevention of loss of capacity, especially in bad weather) 
brought about by the E&D products. No attempt has been made to provide a 
cost/benefit study of the E&D elements for ORD. For study purposes, the im- 
pact of the E&D elements are estimated under certain assumptions of their im- 
plementation at the airport (refer to Section 3) . 

The current operations at ORD form the baseline of this analysis. 
Planned improvements of the airport have been incorporated in the analysis of 
future environments. Although every attempt has been made to predict future 
ATC environments accurately, the analysis, by its very nature, has to be 
based on the best engineering judgment of the performance characteristics 
of the E&D elements. In some cases, extensive development is required to 
demonstrate the achievability of the performance characteristics of the ele- 
ments. Consequently, the results of this analysis may need to be updated as 
better estimates become available. 

Section 2 discusses the E&D elements related to the terminal area oper- 
ations at ORD. The methodology used to evaluate the impact of E&D elements 
on O'Hare is presented in Section 3. Section 4 discusses the estimated capacity 
increases for O'Hare through reduced longitudinal separation and metering 
and spacing systems. The potential impact of Airport Surface Traffic Control 
(ASTC), Area Navigation (RNAV) and Microwave Landing System (MLS) is 
presented in Section 5 with the conclusions and recommendations of this anal- 
ysis being discussed in Section 6. 

2. E6D ELEMENTS IMPACTING OPERATIONS AT O'HARE 

Of the nine basic elements of the FAA E&D program (Reference 1), the fol- 
lowing six affect the operations at O'Hare: 



I- 



Wake Vortex 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) 

Area Navigation (RNAV) 

Microwave Landing System (MLS) 



This section provides a brief description of each of these elements and their 
interactions. The potential impact of the elements on O'Hare are discussed in 
Sections 4 and 5. In addition to the overview document (Reference 1), a num- 
ber of previous studies provide insight into the operations and benefits of the 
E&D elements - Reference 2 for ASTC; References 3, 4, and 5 for RNAV; and 
References 6, 7, and 8 for MLS. 



2.1 WAKE VORTEX AVOIDANCE SYSTEM (WVAS) 



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. To develop a system capable of re- 
ducing separations by predicting vortex motion, it was first necessary to 
learn enough about the life, decay and movement of vortices as a function of 
generating aircraft and meteorological conditions so that such predictions 
could be made. Using predictive data, the approach controller can then es- 
tablish aircraft spacings 5-15 miles from the runway threshold based on the 
expected vortex transport and decay conditions in the runway approach corri- 
dor. 

Currently, there are two levels of WVAS installations envisioned. The 
first level, called the Wake Vortex Advisory System, utilizes the concept of 
using wind speed and direction information to reduce aircraft separations 
during those times when vortices either quickly decay or move from the ap- 
proach corridor. As shown in Figure 2-1, the meterological network con- 
sists of six (6) 50-foot towers located to measure wind parameters at each 
of the operating corridors. Six towers are considered necessary since tests 
at O'Hare and at the JFK International Airport have shown that the inhomo- 
geneity cf the atmosphere precludes the use of a single centrally located 
sensor for the measurement of the wind parameters. Data is transmitted 
from the meteorological towers to a centrally located processor. A multi- 



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plexer successively samples the sensor outputs and converts these to a 
parallel digital data word which in turn is serialized and transmitted over 
standard existing FAA lines to a central facility where receivers reconvert 
the data to a parallel format for input to a microprocessor. 

The sensor outputs are sampled at two samples per second with two 
minute running average maintained on each sensor. The averaged meteor- 
ological data from the runway in use is then compared to a meteorological 
vortex advisory system algorithm and the vortex condition determined. Long 
term sampling and hysteresis are used to prevent frequent and erroneous 
changes in the indicated vortex condition. 

Arrays of ground wind vortex sensors are used in the wake vortex 
advisory system to provide an alert or fail safe function if the vortices 
move contrary to the predictive algorithm. During the current feasibility dem- 
onstration phase, being conducted at O'Hare, only three (3) arrays of ground 
wind sensors have been installed. A complete operating system at O'Hare 
would require all six operating corridors to be instrumented. 

It should be noted that the wake vortex advisory system design rep- 
resents a "first-cut" system design and it is anticipated that both hardware 
and software changes will be required during the feasibility evaluation phase. 
Finally, one must be reminded that the intent of the feasibility demonstration 
at O'Hare is to test the validity of the concept, and is not intended as a final 
hardware design . Should the advisory system prove itself capable of im- 
proving ATC operations, an available option is to leave it in place and uti- 
lize its capabilities operationally. If such a decision is made, it will be 
necessary to modify the installation to change it from temporary to permanent. 
In addition, it will be necessary to install ground wind sensor equipment in 
the remaining three operating corridors and to conduct some operational 
suitability tests. 

Wake vortex program plans also include the development of a more 
sophisticated automated system with predictive capabilities called the Wake 
Vortex Avoidance System. Figure 2-2 shows a block diagram of the automated 
wake vortex avoidance system concept. 

The system operates in the following manner. Vortex and meteorolog- 
ical data will be continually input into the WVAS dedicated minicomputer. 
Stored within the minicomputer will be the vortex behavior algorithm and 
aircraft spacing criteria. Spacing between various aircraft types will be 
specified as a function of the vortex behavior algorithm and the hazard 
associated with each aircraft type. A spacing matrix is generated and pro- 
vided to the ARTS III computer where it will be used along with metering 
and sequencing criteria to establish minimum spacings in the terminal area 
compatible with safety and operational requirements. The predicted infor- 



F-4 



> 1 1 1 



VORTEX SENSOR — , -_ METEOROLOGICAL SENSORS 



WVAS COMPUTER 



STORAGE 



OUTPUT 



VORTEX BEHAVIOR SAFE 
ALGORITHM SEPARATION 

MATRLX 



HAZARD SEPARA- 
TION CRITERIA 



ALARM 



ATCRBS 



ART HI COMPUTER 



STORAGE 



METERING 
AND SPACING 
CRITERIA 



OUTPUT 



SEPARATION 



ALARM 



TOWER 



SEPARATION 



ALARM 



AIRCRAFT 



o 

< 
K 

< 

w 



Figure 2-2. WVAS Automated Operation 



F-5 



mation should be provided to ARTS III with a lead of about 10-15 minutes to 
allow for proper metering and hand off procedures in the terminal areas. 

The spacings provided must also be sufficiently insensitive to minor 
meteorological variations so that the spacing matrix is not continually changing 
since this would prevent orderly sequencing and metering operations. 

Concurrent with providing spacing information to ARTS III, the WVAS 
minicomputer will be continually monitoring and tracking vortices in real 
time. When a vortex moves contrary to the predictive algorithm and remains 
in the flight path, an alarm signal is simultaneously sent to ARTS III, the tower 
and the affected aircraft. For the predictive system to operate effectively, the 
probability of such a situation occurring must be quite low. To determine the 
probability of a vortex moving counter to the prediction requires knowledge 
of the sensitivity of the vortex behavior model to minor changes in its critical 
parameters. Once this sensitivity figure is established, it should be possible 
to reduce the probability of a vortex moving counter to the prediction by adding 
additional safety margin to the critical behavior model parameters. 

To obtain maximum benefit from the WVAS an effective metering and 
sequencing program is essential, since controllers would not have the cap- 
ability to fully utilize the matrix output. The matrix conceivably would be 
complex and change relatively frequently, requiring a computer to store, uti- 
lize and display optimum spacing data. 



2.2 UPGRADED AUTOMATION 



The automation aids to the controller, when fully developed, will in- 
clude digitized displays of aircraft separations, computer generated alarms 
and WVAS information display. The Upgraded Automation program plans to 
develop metering and spacing (MeS) systems evolving from the current manual 
system to the sophisticated Advance M&S system through a basic (Initial Oper- 
ating Capability - IOC) M&S system. The purpose of the M&S systems is to de- 
crease the delivery error of aircraft at the gate of the final approach in order 
to provide higher precision for the aircraft separations uniformly over time. 

The basic (IOC) M&S system employs path stretching and shortening 
between way points defined on arrival routes. The system will evolve from 
the Denver M&S system and will provide control instructions to the controller 
displays for voice transmission to the pilot. The path control of aircraft over 
the way points on the arrival routes will increase the delivery accuracy of the 
aircraft. Such an increase will help reduce the buffer required to ensure non- 
violation of the separation standards. The reduction in the required buffer 
decreases actual spacing between aircraft and thus aids in increasing the 
capacity. 



F-6 



The basic (IOC) M&S system design will be able to handle up to two 
independent arrival streams which cover all the operating configurations at 
O'Hare. The M&S system will be based on the ARTS III A (enhanced) system 
and will be oriented toward controlling traffic for a single airport (i.e., 
satellite airports are not considered) . The system will incorporate the abil- 
ity of handling changes in runway configurations. With the basic (IOC) M&S 
system the controller will be required to manually input the desired separa- 
tion between arriving aircraft to obtain appropriate departure gaps. The con- 
troller has the freedom to change the desired departure gaps to accommodate 
changing traffic situation through appropriate input to the M&S system. The 
interface with the Wake Vortex Advisory /Avoidance System is also conducted 
manually through appropriate two state (RED/GREEN) input depending on 
the indication of the WVAS output. The basic (IOC) M&S system is expected 
to decrease the inter-arrival error between aircraft from the current 18 
seconds (one standard deviation) to 11 seconds (one standard deviation) 
(Reference 9) . 

The advanced M&S system, expected to evolve from the basic (IOC) 
system, enhances the performance with better delivery accuracy and added 
system capabilities. This system will be able to control multiple dependent 
arrivals (up to 3 streams) . In addition, the handling of the departure queue 

(i.e. , creating departure gaps) will be automated, as will the interface with 
the WVAS installation. The presence of the data link will enable the ad- 
vanced M&S system to provide routine control messages to the pilot in an 
automated mode. The advanced M&S system will also interact with the ASTC 
system to provide a more efficient interspacing of arrivals and departures. 
The inter-arrival error between aircraft is expected to decrease to 8 seconds 

(one standard deviation) under the advanced M&S system (Reference 9). 



2.3 DISCRETE ADDRESS BEACON SYSTEM (DABS) 



DABS is a logical technical improvement to today's Air Traffic Control 
Radar Beacon System (ATCRBS) and will be fully compatible with ATCRBS 
airborne transponders and ground-based interrogators. DABS is designed 
to reduce the surveillance error and provide a ground-air-ground data Sink 
with the capability of addressing each aircraft in a discrete manner. The 
data link will assist in reducing the voice communication workload of the con- 
troller and provide the means of automating the transmission of routine mes- 
sages between the aircraft and the ground. The data link will also interact 
with the M&S system interchanging automated messages between discretely 
addressible aircraft and the ground control system. 



F-7 



2.4 AIRPORT SURFACE TRAFFIC CONTROL (ASTC) 



Reference 10 describes the ASTC program and Reference 2 its appli- 
cation to ORD. A brief description of the elements of ASTC is presented 
here. The results of the study for ORD (Reference 2) are presented in 
Section 5. 

The ASTC program is primarily oriented toward aiding the ground con- 
troller with improved automated displays using surveillance data and digit- 
ized displays. The need for an automated improved airport surface traffic 
control becomes more important in bad visibility conditions. There are two 
basic aids being developed. 

ASDE-3 (Airport Surface Detection Equipment), a new ground surveil- 
lance radar, will display the position of each surface vehicle on the airport 
surface to the ground controller. In heavy traffic, however, some degree of 
pilot position reporting may be required due to lack of identity (on ASDE-3 
display) . The same basic information that is given to the ground controller 
may also be given to the local controller. ASDE-3 will be a modern solid 
state radar. The specified MTBF will be 2000 hours, a 10 to 1 improvement 
over the modified ASDE-2. The unit will operate at about 16 GHZ versus 
the 24 GHZ of ASDE-2 and have a redesigned antenna. Range improvement 
under similar rainfall rates has been estimated at approximately 50 percent. 

TAGS (Tower Automated Ground Surveillance) has the primary objec- 
tive of restoring the ground control capacity lost through bad cab visibility 
even when an ASDE is available. TAGS will present a clear uncluttered plan 
view display of the airport and will label each ATCRBS (DABS) beacon 
equipped target with flight identity. Target detection and identity correla- 
tion problems present with ASDE should be eliminated. In addition, since 
TAGS will be a cooperative (relying on an on-board beacon), it will be vir- 
tually weather immune eliminating rainfall penetration problems associated 
with passive radars (even ASDE-3) . 

Figure 2-3 presents a possible display format for TAGS. The figure 
shows a wholly synthetic display such as would be used if TAGS were to re- 
ly solely on the ATCRBS (DABS) sensor for information and thus replace 
ASDE. The decision as to whether ASDE should be replaced or used by TAGS 
has not yet been made. A TAGS system which would use ASDE-3 for an analog 
radar target and the ATCRBS (DABS) sensor for flight identity to tag the radar 
image is under consideration. As currently planned, the combined sensor 
system (hybrid system) would be an option in the TAGS engineering model 
development program. 



F-8 




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The E&D element most closely tied to TACS is Metering and Spacing. 
The current local control problems arise when the demand forces the con- 
troller to try and release departures between the closely spaced arrivals 
on dependent runways. In order to increase arrival rates, M&S will space 
more arrivals closer together. This will expand the problems of local con- 
trol. Unless timing aids can be supplied (i.e., TAGS), the departure capac- 
ity may drop off lower than it is now. Excess arrivals can bog down the air- 
port and may not be of value without concomitant increases in departure capac- 
ity. This problem has not been examined in detail but will be as Advanced 
M&S develops. 



2.5 AREA NAVIGATION 



A detailed study of RNAV and its benefits can be found in References 
1, 3, 4, and 5. A brief description of RNAV is presented here with its bene- 
fits for ORD being discussed in Section 5. 

In the present ATC system, navigation is performed along a series of 
straight line courses known as radials which extend radially from VORTAC 
and VOR ground stations. This constrains all routes to a series of straight 
line segments joining one VOR/VORTAC to another. The term Area Naviga- 
tion (RNAV) refers to an airborne navigation system which provides. navi- 
gation along any course to any destination or to any intermediate way point. 
The term 2D is commonly used to refer to RNAV systems which provide navi- 
gation in the horizontal plane to a point defined in two dimensions by lati- 
tude and longitude or a bearing and a distance from a VOR/VORTAC ground 
station. The 3D-RNAV (or VNAV) system adds the third vertical dimension 
of altitude and 4D RNAV systems add the fourth dimension of time. RNAV 
will enable aircraft to fly from one designated way point to another within 
the terminal area without being told when and where to turn and change 
altitude by the controller by using (1) delay fan; (2) direct to next way 
point; (3) parallel offsets on base leg; and (4) multiple discrete parallel 
departure paths . 

The RNAV routes may interact with the M&S system in defining the 
M&S way points and the RNAV system may provide better aircraft location 
data to the M&S system. 



2.6 MICROWAVE LANDING SYSTEM (MLS) 



A detailed description of MLS and its benefits are presented in 
References 1, 6, 7, and 8. The following paragraphs provide a brief sum- 
mary of MLS. The benefits of MLS for ORD is discussed in Section 5. 



F-10 



MLS is an air-derived data system operating in the microwave (C-band) 
region of the frequency spectrum which provides precise azimuth and eleva- 
tion angle data as well as range (DME) data over a wide coverage volume. The 
data is suitable for visual display to facilitate manual approach and landing 
in poor visibility conditions, and may be provided as an input to the automa- 
tic flight control system for fully automatic approach and landing. A simp- 
lified schematic presentation of the MLS is shown in Figure 2-4. The system 
can be installed with a number of levels of sophistication; from the capability 
to define a single path vertically and horizontally to a capability to define 
multiple paths. The horizontal position is defined by signals transmitted from 
the ground azimuth unit (AZ-1) and the vertical path is defined by signals 
transmitted from the ground elevation unit (EL-1) . In some systems, precise 
flare guidance is provided by an additional elevation unit (EL-2) and horizon- 
tal missed approach guidance is provided by an additional azimuth unit (AZ-2) . 
Aircraft position within the area of coverage is determined on-board the air- 
craft by a compatible receiver. The system operates in the C band except for 
the flare guidance (EL-2) which operates in the KU band. 



3. METHODOLOGY OF ASSESSINC THE IMPACT OF E6D ELEMENTS 



To assess the impact of the six E&D elements, it is convenient to study 
WVAS, Upgraded Automation and DABS through runyvay capacity increases 
brought about by reduced longitudinal separation and increased delivery accur- 
acy of the M&S system. The effect of ASTC, RNAV and MLS are best analyzed 
individually and a number of previous studies (References 2 through 8) have 
done extensive analysis in this respect. The benefits of ASTC, RNAV and MLS 
for O'Hare, presented in Section 5, draw heavily from these references. 

In order to analyze WVAS, Upgraded Automation and DABS, it is con- 
venient to group the future ATC equipments according to the expected time 
of availability. It should be recognized that there are inherent risks in any 
development program, and hence, the time of availability reflects the current 
best FAA estimates. Table 3-1 shows the equipment groups!/ for the future 
environments together with the estimates of the development and the implement- 
ation dates of each. The optimistic, most likely and the pessimistic dates are 
based on accelerated,, normal and deferred priority of budget, procurement and 
implementation cycles. In this analysis the groups have been considered as a 
single entity and no attempt has been made to study the impact of any particular 
element of a group. 



V The equipment groups for future ATC environments and the develop- 
ment and implementation dates were provided by AEM-100 division of 
the Office of Systems Engineering Management of the Federal Aviation 
Administration. 



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Croup 1 has only the wake vortex advisory system which is then supple- 
mented, in Croup 2, by the basic M&S system. Croup 3 has the more sophis- 
ticated wake vortex avoidance system and the benefits of an improved surveil- 
lance including automation aids to the controller in the form of digitized dis- 
plays of separation measures and computer generated alarms. Croup 4 repre- 
sents the most sophisticated system with advanced fully automated metering and 
spacing and DABS supplementing the Wake Vortex Avoidance System. 

For each of the groups of Table 3-1, to be able to estimate the capacity 
improvements, the reduced longitudinal separation standards, departure 
spacings, M&S buffers and WVAS utilization has to be developed. These per- 
formance characteristics can then be used as inputs to the FAA capacity model 
to estimate future capacities under both safe (green light) and fall -back (red 
light) conditions of the WVAS. These inputs have been developed in Refer- 
ence 9 and are based on the small/ large/heavy classification of aircraft as 
follows: 



Small: 12,500 pounds or less certificated gross takeoff 

weight and Learjets 

Large: Between 12,500 pounds and 300,000 pounds cer- 

tificated gross takeoff weight (except Learjets) 

Heavy: 300,000 pounds or more certificated gross takeoff 

weight 



The relevant inputs for the capacity models are presented in Tables 
3-2 through 3-5. For further details, the reader is referred to "Longitudinal 
Separation Standards on Final Approach for Future ATC Environments, October 
1975" (Reference 9) . The IFR separation standards for each of the groups - 
under both safe conditions and fall back position as indicated by WVAS instal- 
lations - are shown in Table 3-2. The minimum IFR standards are down to 
2.5 nmi in Group 3 and 2 nmi in Croup 4 under "Green Light" conditions of WVAS. 
In Croup 4, almost all the standards are 3 nmi or less with the exception of a 
small aircraft following a heavy aircraft. The VFR "separation standards" shown 
in Table 3-3 are only analytic constructs to appropriately represent operations 
under VFR conditions in the modeling process and hence, should not be consid- 
ered regulatory in nature. Table 3-4 shows the predicted departure rules for 
the four ATC Groups. The M&S buffer and the Wake Vortex System utilization 
are shown in Table 3-5. Although the basic (IOC) and the advanced M&S system 
reduce the delivery error, the number of standard deviations (sigma) to be 
protected against is increased from 1.65 (0.05 probability of violation) to 2.33 
(0.01 probability of violation) . This is due to the fact that in the current sys- 
tem the controller is able to anticipate situations in advance and reduce the op- 
erational violation probability considerably. The increase in the number of 



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F-18 



standard deviations in the M&S buffer assures a suitably low violation probabil- 
ity under a tighter, less flexible automated system. The estimates of the Wake 
Vortex System utilization are based on the same preliminary analysis of vortex 
data. 



4. POTENTIAL CAPACITY IMPACT OF WVAS, UPGRADED AUTOMATION & DABS 



The capacity impact of WVAS, Upgraded Automation and DABS are evalu- 
ated using the equipment groups discussed in Section 3. Each group is consid- 
ered as an entity and no attempt is made to study each element individually. Such 
an analysis is appropriate due to the strong interrelationship of the elements of a 
group. Capacity estimates for selected configurations for both IFR and VFR con- 
ditions are made using the FAA capacity model. Capacity calculations are re- 
stricted to Croup 2 and Croup 4 together with their respective fall back positions. 
These estimates are sufficient to show the trend of the future ATC equipment 
groups. All estimates are based on 50 percent arrival and the inputs presented 
in Section 3. The operations data used in the baseline runs were not changed 
except for future separation standards (including departure rules), aircraft mix 
and M&S buffers. For analysis purposes, Croup 2 calculations are based on the 
1985 mix and Croup 4 on the 1995 mix. To better understand the effect of mix 
changes (increasing heavy aircraft) on capacity, estimates are also made of 
capacity with future mixes under the existing ATC rules of separations and de- 
parture rules with today's system capabilities. 

For both IFR and VFR, a number of different configurations were selected 
so as to appropriately represent the range of capacities of the various runway 
configurations at ORD. Specifically, Configurations 3, 4 and 16 were chosen to 
represent IFR operations and Configurations 4, 6 and 13 to represent VFR oper- 
ations. In addition, Configuration 1 was analyzed to study the effect of mix segre- 
gation on the south complex (arrival 32L, departure 27L) where the vortex rule 
has a significant impact on capacity. The vortex rule requires a two minute gap 
behind any heavy operation in such a configuration because both the arrival 
and the departure aircraft are airborne at the intersection. 

The results of Croup 2 and Croup 4 analysis are presented in Table 4-1 . 
Figures 4-1 and 4-2 are graphical representations showing the range of capac- 
ities of different runway configurations for IFR and VFR respectively. The capac- 
ity gains!' for Croup 4 over today are of the order of 10 percent to 37 percent 
for IFR operations at O'Hare. The gains!' under VFR conditions are more mod- 
est with a range of 8 percent to 10 percent. It should be noted that these in- 



ly Weighted gains based on 75 percent utilization of the wake vortex 
avoidance system . 



F-19 



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creases are in spite of the increases of the heavies from 16 percent today to 
48 percent for Group 4. Without the E6D elements, the increase in the percent- 
age of heavy aircraft causes a decrease in IFR capacity of over 5 percent and a 
reduction of 5 percent - 10 percent in VFR capacity. 

For Croup 2, the IFR capacity increases!' are of the order of 5 percent. 
Under VFR conditions the separation standards are not predicted to change 
for Croup 2. Consequently, the capacity impact!/ is small (less than 3 per- 
cent) .V It should be noted that although M&S system reduces the inter-arrival 
error, in this analysis the number of standard deviations to be protected against 
is increased for Croup 2 (refer Section 3) to account for a tighter less flexible 
automated system. 

Table 4-2 shows the effect of traffic segregation in Configuration 1 used 
under VFR conditions. Segregating departures only increases the capacity 
under the configuration by 10 - 15 percent. Segregating arrivals also adds an 
additional 5-10 percent increase in capacity. 



5. POTENTIAL IMPACT OF ASTC, RNAV AND MLS 



This section discusses the benefits of ASTC, RNAV and MLS on O'Hare. 
The results presented here are drawn from a number of previous studies. In 
some instances only qualitative answers could be provided under the scope of 
this study. Areas requiring additional studies to determine the full impact of 
these E&D elements are identified. 



5.1 BENEFITS OF ASTC 



The ASTC program covers three stages of improvements at O'Hare. 
These are near term improvements to ASDE-2, ASDE-3 deployment and TAGS 
deployment. Under bad visibility conditions, ground movement of aircraft 
presents a critical problem at O'Hare. Under such conditions, ASDE-2 Brite 
displays become exceedingly useful. The next three subsections discuss 
the three stages of improvements for O'Hare. 



5.1.1 Near Term System Improvements 



While the ASDE-2 Brite display contributes significantly to 
the bad cab visibility capacity at O'Hare, ASDE-2 is an aging 



1/ Weighted gains based on 40% utilization of the wake vortex advisory 

system . 
2/ The estimate includes the effect of the loss ,n capacity due to increase 

in the percentage of heavy aircraft. 



F-24 



piece of equipment with several limitations. ASDE-2 problems 
which have affected the O'Hare unit are: 



System reliability - low MTBF (18.3 hours). 

Brite display system performance (giving a 
dim and "fuzzy" picture with poor target def- 
inition) . 

Low received signal strength and high noise 
(giving loss of small targets at long range) . 

Poor rainfall penetration (causing whiteout at 
short range and blackout at long range) . 



In response to these problems several near term improvements 
have and will be made to the O'Hare ASDE-2: 



Reliability modifications have been made replacing 
the local oscillator with solid state components and 
redesigning the modulator section. The MTBF has 
been raised to over 200 hours. The mods were in- 
stalled at O'Hare in 1972 and 1974 by TSC at a cost 
of approximately $4,000. 

A new video scan converted bright display (Nu- 
Brite) was developed and tested at JFK in early 
1973. A production version will be installed at 
O'Hare in May 1976 by ITT under contract to TSC. 
The unit will give a bright version of the ASDE-2 
PPI with little loss in target definition. Tests at 
JFK indicate a substantial improvement in basic 
target detection (approximately a 40 percent im- 
provement) . The O'Hare unit will cost approxi- 
mately $120,000 since the production buy is only for 
3 airports (O'Hare, San Francisco, and New York 
(JKF)) and includes non-recurring engineering de- 
sign and development costs. Added units will 
cost about $50,000. The Nu-Brite will be used 
with ASDE-3. 

A new Display Enhancer Unit was developed by 
Texas Instruments and tested at LAX and JFK. A 
production buy is being initiated by AAF-320. An 



F-25 



estimate on O'Hare deployment would be early 1978. 
The DEU will suppress all unwanted display back- 
ground and synthetically enhance all runway and 
taxiway edges. Limited tests at LAX indicate a sub- 
stantial improvement in basic target detection (approx 
imately a 45 percent improvement) . 

A solid state IF amplifier section has been devel- 
oped by Cardion under contract to TSC . A unit 
has been installed and tested by BOS. Substan- 
tial improvements in received signal to noise were 
found. In addition, amplifier alignment was greatly 
simplified. The latter will result in a more maintain- 
able (and, therefore, better performing) ASDE-2. 
No schedule for deployment exists pending funding 
resolution for a production buy. Costs per radar 
on a production buy covering all 12 ASDE-2 's are 
estimated at $17,000. 



5.1.2 ASDE-3 Deployment 



The ASDE-2 improvements will result in a controller display 
which is nearly as good as state-of-the-art technology can produce 
for an imaging analog radar. ASDE-3 benefits will be in further 
improving ground surveillance reliability, maintainability, and 
availability and in improving rainfall penetration. Development of 
an ASDE-3 engineering model for test and evaluation is scheduled 
for completion in time for the FY79 production buy. It is estimated 
that an ASDE-3 will be available for deployment at O'Hare by 1980. 
Production costs are estimated at $750,000 per unit (installed) . 

An earlier study (Reference 2) has estimated the impact of ASDE 
on capacity at O'Hare. The results are given in Figures 5-1 and 5-2 
for local and ground control, respectively. The figures also show 
TAGS improvements which are discussed in Section 5.1.3. The fig- 
ures indicate that when the controllers cannot see their area of re- 
sponsibility (i.e., runways for local, taxiways for ground) and 
they do not have an ASDE radar, the capacity of both positions drops 
significantly. An operational ASDE restores nearly all lost local 
control capacity. This benefit to local control during poor visibi- 
lity weather conditions is the rationale for both the ASDE-2 improve- 
ments and ASDE-3. ASDE does not help ground control nearly as 
much as it does local control. For all but the very large airports, 
the help provided ground control by ASDE is adequate. O'Hare, 
unfortunately, is one of those airports where ground control re- 
quires something beyond ASDE. This motivates the TAGS system 
described below. 



F-26 



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F-28 



5.1.3 TAGS Deployment 



In addition to the basic TAGS system described in Section 
2.4, two system options will be available. The first will per- 
mit the TAGS sensor to detect activation of the Ident button on 
the ATCRBS beacon in each aircraft. 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 position reports to cue aircraft location. This could re- 
duce voice channel loading in all visibility conditions and pro- 
vide a more efficient communication system to both controller 
and pilot. Reduction in voice channel loading of 10 percent 
over visibility loading has been estimated (Reference 2). 

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 within a mile or so of the 
airport currently lost to the ASR. Airborne data will be supplied 
to TAGS from ARTS on an automated data transfer when available. 
The key information to be displayed is estimated time-to threshold 
for the arrival system. The computer will utilize position, speed 
and aircraft type to provide the estimate. When factored into con- 
troller strategies, it has been estimated that this information could 
increase the good visibility local control /runway capacity on cer- 
tain difficult to operate configurations. It should be pointed out 
that TAGS will not affect the best configurations and so will not 
likely impact the overall airport quota. The benefit would be to 
raise the bad configuration capacities closer to those of the good 
configurations and reduce the delays associated with being forced 
to them. No delay reduction estimate has been made. 

The primary objective of TAGS is to restore the capacity lost 
by ground control during bad cab visibility (even with ASDE) . 
Figure 5-2 indicates that this loss is substantial. Secondary bene- 
fits of TAGS would be reduced voice loading to ground in good 
visibility and potential capacity improvements to local on diffi- 
cult to handle configurations (e.g. , an estimated 9 percent for 
a single mixed operation as shown in Figure 5-1) . 

TAGS is currently in the final stages of system definition. 
Sensor field tests are concluding and controller evaluations of 
anticipated display capabilities are planned for this Spring. 
O'Hare controllers will be involved. Development and test of 
an engineering model is scheduled for completion about 1980. 
O'Hare is under consideration for the test and evaluation site 



F-29 



using the ASDE-2 (with all proposed modifications) to provide 
the TAGS hybrid option. With this scenario, O'Hare could be 
deriving TAGS benefits by 1980. A production unit using 
ASDE-3 for the radar targets would not likely be deployed be- 
fore 1982. Deployment costs for TAGS (not including ASDE-3 
if the hybrid is used) are estimated at $1.4 million per unit 
installed. 



5.2 BENEFITS OF RNAV 



RNAV routes will help eliminate some of the airspace congestion brought 
about by the increase in traffic. Although the benefits of RNAV are fully 
realized in a total RNAV environment, a pervious study (Reference 5) of real- 
time terminal area simulation at NAFEC has concluded that (1) the controllers 
are capable of operating in a mixed VOR/RNAV environment with reduced 
workload and no reduction in system capacity and (2) significant reductions 
in controller communications time were observed as the percent RNAV mix 
increased. 

An RNAV terminal area design developed by Champlain Technology 
(References 3, 4) was compared to present traffic flows within the ORD terminal 
area. The designs are shown in Figures 5-3 through 5-6 representing today's 
traffic flows and those of a post-1982 RNAV structure. This analysis has not 
attempted to evaluate alternative approaches to more flexible navigation (e.g., 
additional VOR, route restructuring, etc.), their impact and the relative bene- 
fits of RNAV with respect to other VOR scenarios. Table 5-1 shows the 2D 
RNAV fuel and time benefits of the RNAV designs over the present traffic flows 
resulting from reduced route lengths and/or reduced altitude restrictions to 
combined arrival and departure flight. 

In addition to the 2D RNAV benefits at ORD, an estimate of the benefits of 
utilizing pilot initiated 3D (VNAV) descents over the same RNAV terminal routes 
to provide additional time and fuel benefits was made. Table 5-2 below shows 
the results of that study (Reference 3) . 

Based on the above fuel and time savings for 2D and 3D RNAV, an esti- 
mate was made for the annual air carrier economic savings of 2D and 3D RNAV 
at ORD. Assuming a conservative fuel cost of $0,036 per pound and a cost for 
time of $9.62 per minute for air carriers, the following annual estimates for air 
carrier terminal area 2D and 3D benefits at ORD are made: 





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 



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F-36 



The same study estimates that a 4D RNAV system may 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 and 27L (Reference 11), indi- 
cates that the reductions for arrivals and departures are substantial in a 100 
percent RNAV environment (Table 5-3) . These estimates compare very fav- 
orably with the detailed RNAV simulation conducted at NAFEC (Reference 5) . 

Three additional points should be made in considering the application 
of RNAV to ORD . These are perhaps the most important from the controller 
point of view and are important findings of the NAFEC simulations. First, 
the benefits in the reductions found in the number of control instructions is- 
sued, radio transmissions and radio talk time are not found only at a 100 per- 
cent RNAV environment but are found to a worthwhile degree even for a 
mixed environment in which only 25 percent of the traffic is RNAV equipped. 
As the percentage of RNAV traffic increases, so these benefits increase. 

The second point addresses the controller acceptance of RNAV in the 
terminal area. It has been found through the NAFEC simulations (in which 
both current field controllers as well as NAFEC controllers have been used 
as test subjects) that controllers generally started the simulations with a neg- 
ative attitude toward the use of RNAV. However, after being exposed to and 
trained in the use of RNAV, controller opinion was always reversed and fav- 
ored RNAV. This change was particularly marked in the field controllers. 
The point here is that controllers' attitudes changed in favor of RNAV after 
adequate training and exposure. 

The last point that should be made is that while no increase in oper- 
ations rates was found in the simulations of RNAV operations, there was no 
decrease in operations rates in the simulations completed to date. 



5.3 BENEFITS OF MLS 



A detailed analysis of MLS application was beyond the scope of this 
study. Such an analysis is recommended to evaluate the need and the impact 
of MLS for O'Hare. A brief evaluation of the possible applications of MLS 
showed that the following characteristics of MLS may provide some benefits 
for O'Hare (subject to further detailed analysis): 



Smaller critical areas under CAT II and III conditions - 
With arrivals and departures on the same runway (e.g. , 
14L/R or 32L/R), the critical area for ILS under CAT II 
conditions requires the departing aircraft to be more than 
400' away from the runway centerline or the arriving air- 



F-37 



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F-38 



craft to be beyor.d the outermarker when a departing air- 
craft is within 400' of the runway centerline. The problem 
is more severe in CAT III conditions. MLS will have a 
smaller critical area with significantly less restrictions 
on traffic flow. A detailed study is required to assess the 
impact of such an installation. 

Curved approaches to resolve possible traffic patterns 
between O'Hare and Midway - O'Hare runway 32 parallel 
operations and Midway runway 22 operations present a 
conflicting traffic pattern. A similar situation exists 
with runway 32L arrival at O'Hare and runway 13R arriv- 
al at Midway. MLS with its curved approach capability 
will be able to resolve these conflicts similar to those ex- 
isting in New York - JFK and LGA (References 6, 7 and 8) 

Availability of additional frequency channels - Currently 
there are no ILS frequencies available for assignment at 
Chicago. At O'Hare, four runways operate with identical 
frequencies serving opposite ends of the runway: 



Runway 4R/22L 110.1 MHZ 

4L/22R 111.3 MHZ 

9L/27R 110.5 MHZ 

9R/27L 111.1 MHZ 



MLS provides 200 frequency channels as opposed to 20 
ILS frequency channels currently available. In addition, 
MLS will provide sufficient frequency channels to allow 
additional landing aids on other airports in the vicinity. 
The individual frequency assignments to the runway ends 
at O'Hare (4R/22L, 4L/22R, 9L/27R and 9R/27L) will 
make more runway configurations available when main- 
tenance is conducted on an ILS at a particular runway end. 

Reduced susceptibility to reflections - MLS may further 
benefit O'Hare by providing a full landing aid on runway 
4L (currently without glide slope) due to the inherent re- 
duced susceptibility of MLS to reflections. A detailed 
siting study is required to determine the feasibility of 
a full instrumented landing aid on 4L even under an MLS 
environment. 

Noise benefits of curved approaches - The curved ap- 
proach capability of MLS provides the technological 
basis to develop approaches to aid in noise abatement 



F-39 



procedures by routing traffic away from populated and 
noise sensitive areas in favor of parks, industries, high- 
ways and less noise sensitive areas. An extensive 
study, such as References 7 and 8 for New York, would 
be required to explore the feasibility and quantify such 
benefits, if any, for O'Hare. 



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REFERENCES 



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, Revision 1), March 1975. 

2. Transportation Systems Center, "Airport Surface Traffic Control: 
Concept Formulation Study Volumes l-ll." Computer Sciences 
Corporation Report No. CSC-TR-75, 4419, February 1975. CSC-TR- 
74-4411, November 1974. 

3. Federal Aviation Administration, "Implementation of Area Navigation 
in the National Airspace System: An Assessment of RNAV Task Force 
Concepts and Payoffs." FAA-RD-75- , Draft Report, August 1975. 

4. Federal Aviation Administration, "Terminal Area Design: Analysis 
and Validation of RNAV Task Force Concepts." FAA-RD-75- 
Draft Report, October 1975, 

5. Federal Aviation Administration, "Preliminary Two-Dimensional Area 
Navigation Terminal Simulation." FAA-RD-74-209, February 1975. 

6-. Matney, J.S., "Microwave Landing System Applications and Benefits." 
The MITRE Corporation, MTR-6938, July 1975. 

7. Amodeo, F.A., "Benefits of MLS Guidance for Curved Approaches, 
Volume I, Noise Abatement Case Studies." The MITRE Corporation, 
MTR-6951, Volume I, July 1975. 

8. Iyer, R.R., "Benefits of MLS Guidance for Curved Approaches, 
Volume II, Operational Benefits for New York Airports." The MITRE 
Corporation, MTR-6951, Volume II, July 1975. 

9. Sinha, A.N. and Haines, A.L., "Longitudinal Separation Standards 
on Final Approach for Future ATC Environment." The MITRE Corpor- 
ation, MTR-6979, October 1975. 

10. Federal Aviation Administration, "Engineering and Development Pro- 
gram Plan - Airport Surface Traffic Control." FAA-ED-08-1, July 
1972. 

11. Federal Aviation Administration, "Application of Area Navigation to 
Chicago O'Hare" correspondence from ARD-333, February 10, 1976. 



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