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Full text of "Operations analysis of airport surface traffic control (ASTC) system at O'Hare International Airport"

A 



* 



PERMANENT COPY H"» * • & ^OEF 

OPERATIONS ANALYSIS OF 



APR 21 1975 




AIRPORT SURFACE TRAFFIC CONTROL (ASTC) 
SYSTEM AT O'HARE INTERNATIONAL AIRPORT 

VOLUME I 
SECTIONS 1 THROUGH 4 

F. D'Alessandro, W. Heiser, G. Knights, P. Monteleon, 
R. Reffelt, R. Rudmann, W. Wolff 



oMTJMv 




NOVEMBER 1974 



WORKING PAPER # / 



Prepared for 

DEPARTMENT OF TRANSPORTATION 

TRANSPORTATION SYSTEMS CENTER 
Cambridge, Massachusetts 02142 




/ 



Technical Report Documentation Page 



I. Report No. 



2. Government A 



ccfsnon No. 



4. Title and Subtitli 



Operations Analysis of Airport Surface Traffic Control 

(ASTC) System at O'Hare International Airport (Working 

Paper) Volume I - Sections 1 through 4 
Volume II- Sections 5 through 8 



7 Au^or',) w.Heiser.G. Knights, R. Reffelt, W. Wolff, 
F. D'Alessandro, R. Rudmann, P. Monteleon 



3. Kecipirnt'% Cotolog No. 



5. Reporr Oote 

November 1974 



6. Performing Ofqom zolion Code 



8. Performing Orgomiotion Reporr No. 

CSC-TR-74-4410 
CSC-TR-74-4411 



9. Performing Organ i lotion Noma and Address 

Computer Sciences Corporation 
670 Winters Avenue 
Paramus, New Jersey 07652 



10. Work Un.l No. (TRAIS) 



• I. Contract or Grant Nc 

DOT-TSC-678 



I 2. Sponsoring Agency Nome and Address 

Department of Transportation 
Transportation Systems Center 
Cambridge, Massachusetts 02142 



13. Type of Report and Period Covered 



Working Paper 



14. Sponsoring Agency Codf 



15. Supp lementor y Notes 



16. Abstract 

This working paper examines the air traffic control, airline operations, and airport 
management procedures at the busiest airport in the world. Detailed analysis of air- 
traffic flow (based on ASDE film data) and the associated delays are presented for 
ramp, ground control, and local control (runway management) areas. Runway con- 
figurations are examined and surface traffic routing is presented. Congestion loca- 
tions are identified and analyzed. ATC procedures employed by FAA controllers are 
examined through a detailed analysis of communications taking place between pilots 
and controllers. Controller activity and work flow procedures are set forth. The 
results of extensive interviews with pilots and controllers are given to indicate the 
constraints of such factors as aircraft type, visibility, display limitations, and 
special events. Safety aspects are also examined. Based upon the delays and con- 
troller workload results a cost effectiveness analysis is presented to show the pos- 
sible benefits which can be obtained from improvements in the surface traffic control 
system. 



i7. Keywords a irport Operations , Effective- 
ness Measures, Airport Configurations, 
Airline Operations, Tower Cab Operations, 
Environmental Conditions, Runway Config- 
urations, Cost Effectiveness 



18. Distribution Slafemenl 



19. Security Clossif. (of ttiis report) 

Unclassified 



20. Security Clossif. (of this page) 



21. No. of Poges 

Vol. 1-228 
Vol.II-300 



22. Pnc. 



Form DOT F 1700.7 (8-72) 



Reproduction of completed page authorized 



a U. S nOVFBNMrVT I'lllVriNfi OFFICE: 117? ?7"> -Stu/12H 



PREFACE 

This report presents the preliminary findings of the first 
phase of the Advanced Airport Surface Traffic Control 
(ASTC) Systems Concept Formulation Study. The overall 
study is a part of the ASTC program of the Department of 
Transportation, Transportation Systems Center (TSC). 
The program is sponsored by the Department of Trans- 
portation, Federal Aviation Administration (FAA), Sys- 
tems Research and Development Service. The TSC ASTC 
, program office has contracted with Computer Sciences 
Corporation to perform the study. 

The report is a working paper. It is not the final report 
of the study and is not intended for formal Government 
publication. Its purpose is to permit review, comment 
and correction (if required) by the FAA and other agen- 
cies involved prior to incorporating the findings into the 
final report. The report has been reviewed by TSC and 
does incorporate their comments. In addition, all of 
the theoretical analysis of local area capacity presented 
in Section 5. 3. 3. 1 was done by Messrs. Paul Rempfer 
and Lloyd Stevenson of TSC. 



in 



TABLE OF CONTENTS - VOLUME I 

Page 

Section 1 - Introduction 1-1 

1.1 General 1-1 

1.2 Overview of Study 1-1 

1.3 Description of Operations Analysis 1-4 

Section 2 - Operations Analysis Approach 2-1 

2. 1 General 2-1 

2.2 Establishing the Basis for Analyses 2-1 

2.3 O'Hare Operations Effectiveness Analysis Approach 2-8 

2.3.1 General 2-8 

2.3.2 Fuel Consumption Assessment 2-9 

2.3.3 Pollution Emission Assessment 2-11 

2.3.4 Operating Cost 2-12 

2.3.5 Passenger Inconvenience Assessment 2-13 

2.3.6 Accident Risk Assessment 2-15 

2.3.7 Summary of Effectiveness Measures 2-17 
2. 4 Methodology for Functional Analysis of ASTC System Operation 2-19 
2.4. 1 Controller Task Analysis 2-19 

2.4.2 Aircraft Flow Analysis 2-28 

2.4.3 Airline Operations Analysis 2-39 

2.4.4 Airport Management Operations Analysis 2-43 

2. 5 Projection of the Future Operating Environment at 

O'Hare Airport 2-44 

Section 3 - Airport Configuration Description 3-1 

3. 1 General 3-1 

3.2 Runway Configuration Description 3-1 

3.2.1 Runway Descriptions 3-1 

3.2.2 Runway Configuration Usage 3-6 

3.3 Taxi Flow Patterns 3-23 

3.3.1 Configuration 1 3-24 

3.3.2 Configuration 2 3-32 

3.3.3 Configurations 3-34 

3.3.4 Configuration 4 3-36 

3.3.5 Configurations 3-38 

3.3.6 Configuration 6 3-40 



TABLE OF CONTENTS (Continued) 



Page 

3.3.7 Configuration 7 3-40 

3.3.8 Configurations 3-43 

3.3.9 Configuration 9 3-45 

3.3.10 Configuration 10 3-47 

3.3.11 Configuration 11 3-47 
3.4 Terminal Configuration Description 3-51 
3.4. 1 Terminal Gate Layout 3-51 

3.4.2 Aircraft Docking at the Gates 3-54 

3.4.3 Aircraft Movements and Control 3-54 

3. 4. 4 Impact of Terminal Configuration on ASTC System Operation 3-55 

Section 4 - Functional Description of the O'Hare ASTC System 4-1 

4. 1 General 4-1 

4.2 FAA Airport Traffic Control Tower (ATCT) Functions 4-1 

4.2.1 General Responsibilities 4-1 

4.2.2 Tower Cab 4-2 

4.2.3 TRACON 4-69 

4. 3 Airline Functions 4-74 

4.3.1 General Responsibilities 4-74 

4.3.2 Airline Terminal Operations 4-75 

4.3.3 Flight Deck (Cockpit) Operations 4-84 

4.4 Airport Management Functions 4-88 
4. 4. 1 General Responsibilities 4-88 

4.4.2 Airport Personnel Position Descriptions 4-88 

4.4.3 Functional Operations Descriptions 4-92 

4.4.4 Emergency Operations 4-97 



VI 



TABLE OF CONTENTS - VOLUME II 

Page 

Section 5 - Operational/Functional Activity Analyses 5-1 

5.1 General 5-1 

5.2 Traffic Operations Environment for Data Analysis Periods 5-1 
5.2. 1 Selection of Operational Periods for Study 5-2 

5.3 Aircraft Flow Analysis 5-7 

5.3.1 Ramp Area 5-9 

5.3.2 Ground Controllers' Area 5-30 

5.3.3 Local Controllers' Area 5-77 

5.4 Controller Activity (Workload) Analysis 5-140 

5.4. 1 Controller Communications Activity Analysis 5-141 

5.4.2 Controller Non-Communications Activity Analysis 5-169 

5.4.3 Traces of Individual Flights Through the ASTC System 5-186 

5.4.4 Other Observations of Tower Cab Activities 5-194 

5.5 Cockpit Crew Activity (Workload) Analysis 5-201 

5. 5. 1 Crew Activities During Departure and Arrival 5-201 

5.5.2 Cockpit Workload Analysis 5-207 

5.5.3 Cockpit Observations 5-211 

Section 6 - ASTC System Operations Effectiveness Analysis 6-1 

6. 1 General 6-1 

6.2 System Effectiveness Criteria Measures 6-1 

6.3 Current O'Hare ASTC System Effectiveness 6-3 

6.3.1 Traffic Delay Effectiveness 6-4 

6.3.2 Controller Communications Workload 6-6 

6.3.3 Fuel Consumption Effectiveness 6-7 

6.3.4 Pollution Emission Effectiveness 6-10 

6.3.5 Operating Cost Effectiveness 6-14 

6.3.6 Passenger Inconvenience 6-16 

6.3.7 Accident Risk Evaluation 6-19 

6. 3. 8 Qualitative Analysis of Accident Risk Potential 6-25 

6.4 Future O'Hare ASTC System Effectiveness Assessment 6-32 

6. 4. 1 Projected Future Operating Environment 6-32 
6.4.2 Assessment of the ASTC System Effectiveness in the Projected 

Future Operating Environment 6-34 



Vll 



TABLE OF CONTENTS (Continued) 

Page 

Section 7 - Findings and Conclusions 7-1 

7. 1 General 7-1 

7. 2 Summary of Findings 7-1 

7.2. 1 Functional Responsibilities of Operational Personnel 7-1 

7.2.2 Current O'Hare Operating Configuration 7-5 

7. 2. 3 Future O'Hare ASTC System 7-9 

7.3 Conclusions 7-11 

7.3.1 Capacity and Delay 7-11 

7.3.2 System Effectiveness Assessment 7-18 

7.3.3 General Observations 7-20 

7. 3. 4 Summary 7-22 

7.4 Recommendations 7-23 

Section 8 - References 8-1 



vm 



LIST OF ILLUSTRATIONS 



Figur e 



Page 



1-1 Task Breakdown and Study Flow 1-2 

1-2 Simplified O'Hare Operations Analysis Flow Diagram 1-5 

2-1 Departure Flight Operations Flow 2-3 

2-2 Arrival Flight Operations Flow 2-4 

3-1 O'Hare International Airport 3-2 

3-2 Location of Departure Queues and Ground Control Handoff 

Areas at O'Hare 3-25/3-26 

3-3 Aircraft Route at O'Hare — Hangar, Cargo, and Air Force 

Areas 3-27/3-28 

3-4 Main Service Vehicle Roads at O'Hare Airport 3-29/3-30 

3-5 Configuration 1 3-31 

3-6 Configuration 2 3-33 

3-7 Configuration 3 3-35 

3-8 Configuration 4 3-37 

3-9 Configuration 5 3-39 

3-10 Configuration 6 3-41 

3-11 Configuration 7 3-42 

3-12 Configuration 8 3-44 

3-13 Configuration 9 3-46 

3-14 Configuration 10 3-48 

3-15 Configuration 11 3-49 

3-16 Gate Assignments 3-52 

4-1 O'Hare Control Tower Floor Plan 4-3 

4-2 Tower Cab Detail 4-4 

4-3 Tower Cab Photographs 4-10 

4-4 Visual Surveillance Limitations 4-30 

4-5 Radar Coverage 4-32 

4-6 Functional Flow of Major Flight Data Tasks 4-34 

4-7 Functional Flow of Clearance Delivery Tasks 4-39 

4-8 Functional Flow of Major Outbound Ground Tasks 4-45 

4-9 Functional Flow for Major Inbound Ground Tasks 4-56 

4-10 Functional Flow of Major Local Control Tasks 4-61 

4-11 TRACON Room - O'Hare International Airport 4-70 

4-12 United Airlines Gate Plan for O'Hare Airport 4-77 

4-13 VHF Radios in Cockpit 4-85 

4-14 Chicago - O'Hare International Airport Organization Chart 4-89 

5-1 Aircraft Flow Between Movements Analysis Areas 5-7 

5-2 Gate Assignments 5-10 

5-3 Distribution of Ramp Service Times for "Arrivals" 5-18 

5-4 Distribution of Ramp Service Times for "Departures" 5-20 



IX 



LIST OF ILLUSTRATIONS (Continued) 



Figure Page 

5-5 Distribution of Operation Durations 5-21 

5-6 Distribution of Gate Occupancy Times 5-23 

5-7 Timing Relationships - Ground Controllers' Area (Arrivals) 5-31 

5-8 Timing Relationships - Ground Controllers' Area 

(Departures) 5-32 

5-9 Penalty Box Delays 5-52 

5-10 Aircraft Delay in Ground Control Area 5-54 

5-11 Intersection Numbering - O'Hare (CSC Assigned) 5-56 
5-12 Time Line Plot of Ideal Single Runway Operation Saturated 

In Arrival and Departure Demand (80 Operations /Hour) 5-79 
5-13 Time Line Plot of Actual Single Runway Operation Saturated 

In Arrival and Departure Demand in Good Visibility 

Conditions (64 Operations /Hour) 5-79 
5-14 Arrival Runway Occupancy Time for Two One-Hour Periods 

(Total Mean 46 Seconds) 5-81 
5-15 Departure Runway Occupancy Time for Two One-Hour Periods 

(Total Mean 40 Seconds) 5-81 
5-16 Interarrival Spacing for Six One-Hour Periods of Varying 

Demand 5-82 

5-17 Interarrival Spacing for Two One-Hour Busy Periods 5-83 

5-18 Departure Capacity Estimate for Single Runway Operation 5-86 

5-19 Strategy Curves for Various Runway Configurations 5-88 
5-20 Position of Arrival Pairs at the Time of Departure Release 

for Two Runway Configurations 5-96 
5-21 Initial Heading Mix of Departures for Quasi-Independent 

Runway Operation Over 50 Minutes of Heavy Demand 5-98 

5-22 Potential Payoffs for Metering and Spacing 5-104 
5-23 Timing Relationships - Local Controllers' Area 

(Departures) 5-107 

5-24 Correlation of Delay and Capacity Estimates 5-126 

5-25 Local Control Delay - North Side (East Arrivals) 5-128 

5-26 Local Control Delay - South Side (East Arrivals) 5-129 

5-27 Local Control Delay - North Side (West Arrivals) 5-130 

5-28 Local Control Delay - South Side (West Arrivals) 5-131 

5-29 Inbound Ground Channel Occupancy Vs Traffic Volume 5-149 
5-30 Channel Occupancy Vs Aircraft Handled for Both Ground 

Control Positions 5-154 

5-31 Local Control Hourly Occupancy Time Vs Aircraft Handled 5-160 



LIST OF ILLUSTRATIONS (Continued) 



Figure Page 

5-32 Analysis of Short Term Communication Saturation Effects 5-163 

5-33 Ground Control Communication Saturation 5-165 

5-34 Local Control Communication Saturation 5-167 

5-35 Gate Delay Curves 5-183 

5-36 Flight Strip for UA 247 5-187 

5-37 Flight Strip for General Aviation N309VS 5-190 

5-38 Illustration of In-Cockpit Flight Trace 2 5-219 

6-1 Cockpit Communications Workload Calculation 6-22 

6-2 Projected Future Operating Environment at O'Hare 6-33 

7-1 Current O'Hare Layout 7-8 

7-2 Projected Future Operating Environment at O'Hare 7-10 



XI 



LIST OF TABLES 



Table Page 

2-1 Summary of Effectiveness Measures 2-18 

2-2 Examination of Aircraft Flow Variables 2-30 

2-3 Movement Events Measured for ASDE Film Analysis 2-33 

3-1 Classification of Crossing Runway Configurations 3-3 

3-2 Runway Landing Aids at O'Hare 3-5 

3-3 Primary Runway Configurations Identified by ATCT 3-8 

3-4 Runway Usage Minimums Under Low Visibility Conditions 3-11 

3-5 O'Hare Runway Utilization - CY-71 3-13 

3-6 Seasonal Runway Configuration Usage (Jan. and Feb. 1973) 3-15 

3-7 Seasonal Runway Configuration Usage (April and June 1973) 3-16 

3-8 Profile of Runway Configurations Used in Clear and Calm 

Weather 3-19 
3-9 Profile of Runway Configurations Used in the Clear and/or 

Windy Weather 3-20 
3-10 Relative Usage of Various Runway Configuration Classes 

at O'Hare 3-22 

3-11 Gate Assignments Vs Ramp Areas at O'Hare 3-53 

4-1 Responsibilities and Duties of the Flight Data Position 4-16 

4-2 Responsibilities and Duties of the Clearance Delivery 

Position 4-17 
4-3 Responsibilities and Duties of the Outbound Ground 

Position 4-19 

4-4 Responsibilities and Duties of the Inbound Ground Position 4-21 

4-5 Responsibilities of Local Control Position 4-23 

4-6 Clearance Delivery Gate Marking 4-41 

4-7 Predominantly Preferred Checkpoints for Position Reporting 

During Low Visibility Conditions 4-50 
4-8 Specific Points or General Area at Which Turnover to Local 

Control May be Made by Outbound Ground 4-53 

4-9 Responsibilities and Duties of the Approach Control Position 4-71 

4-10 Responsibilities and Duties of the Departure Control Position 4-72 

4-11 Responsibilities and Duties of Parallel Approach Monitor (2) 4-73 
4-12 Authorized Aircraft Parking - O'Hare Passenger Terminal - 

American Airlines 4-80 
5-1 Summary of Operational Environments for Data Periods 

Selected for Detailed Analysis 5-5 

5-2 Ramp Usage Data 5-12 

5-3 Peak Traffic Flow — Ramp Area 5-15 

5-4 Aircraft Flow Data - Ramp Area 5-16 

5-5 Arrival and Departure Hold Analysis 5-24 



xn 



LIST OF TABLES (Continued) 



Table Page 

5-6 Selected Ramp Area Activity (Run #33 - 16:45-17:45) 5-26 

5-7 Ramp Activity by 10-Minute Periods (Run #33) 5-26 

5-8 Sample Data Sheet 5-33 

5-9 Sample Data Reduction Sheet 5-35 

5-10 Summary of Ground Control Aircraft Flow 5-38 

5-11 Summary - Aircraft Flow Statistics - Ground Control 5-51 

5-12 Summary of Analyzed Runs 5-53 

5-13 Breakdown of Holds by Location and Cause 5-57 

5-14 Summary of Holds by Reason 5-70 

5-15 Delay Time by Category 5-70 

5-16 Operating Strategies for Capacity Estimation 5-87 

5-17 Predicted Capacity of Various Runway Configurations 5-89 
5-18 Single Runway Mixed Operations in Good Visibility with 

Continuous Double Departure Demand 5-91 

5-19 Near-Near Runway Configuration in Good Visibility 5-92 

5-20 Near-Far Runway Configuration in Good Visibility 5-94 

5-21 Far-Far Runway Configuration (1 of 2 Cases) 5-95 

5-22 Practical Estimated Runway Capacity 5-99 
5-23 Single Runway Mixed Operations in Bad Cab Visibility 

Conditions With Continuous Double Departure Demand 

and ASDE-2 in Use 5-100 
5-24 Single Runway Mixed Operations in Bad Cab Visibility 

Conditions With Continuous Double Departure Demand 

Without ASDE-2 in Use 5-102 

5-25 Effect of Bad Visibility on Single Runway Mixed Operations 5-102 

5-26 Sample Data Reduction Sheet 5-108 

5-27 Summary of Local Control Aircraft Flow 5-110 

5-28 Summary - Aircraft Flow Statistics - Local Control 5-122 

5-29 Average Delay for the Primary Arrival Modes 5-123 
5-30 North Side/South Side Delay for the Primary Arrival Modes 

in Good Cab Visibility Conditions 5-124 
5-31 Delay and Percent Predicted Capacity for Good Cab Visibility 

Conditions 5-125 
5-32 Distribution Statistics of Local Control Delays (Arrivals 

from West) 5-134 
5-33 i Distribution Statistics of Local Control Delays (Arrivals 

from East) 5-135 

5-34 Summary of Current O'Hare Capacity in Good Visibility 5-137 
5-35 Summary of ASTC Improved O'Hare Capacity in Good 

Visibility Without Metering and Spacing 5-138 



XI 11 



LIST OF TABLES (Continued) 



Table Page 

5-36 Summary of Clearance Delivery Transactions 5-144 

5-37 Summary of Inbound Ground Communications Transactions 5-147 
5-38 Intersection Control Instruction Approach Vs Visibility 

Conditions - Inbound Ground 5-150 

5-39 Summary of Outbound Ground Communications Transactions 5-152 
5-40 Intersection Control Instruction Approach Vs Visibility 

Conditions - Outbound Ground 5-155 

5-41 Summary of Local Control Communications Transactions 5-159 

5-42 Communication Channel Saturation Estimates 5-164 

5-43 Flight Data Activities Measurement 5-173 

5-44 Clearance Delivery Activities Measurement 5-174 

5-45 Departure Ground Activities Measurement 5-175 

5-46 Inbound Ground Activities Measurement 5-176 

5-47 • Local Control Activities Measurement 5-177 

5-48 Summary of Non- Communications Activity Workload 5-185 

6-1 Distribution of Aircraft Types at O'Hare 6-2 

6-2 Weighted Average Gallons of Fuel per Idle Aircraft 

Minute at O'Hare 6-9 
6-3 Typical Pollution Emissions Vs Fuel Consumption Rate 

at Idle Engine Speed 6-11 
6-4 Estimated Average Pollutants per Idle Aircraft Minute 

at O'Hare 6-12 
6-5 Weighted Average Operating Cost Per Idle Aircraft 

Minute at O'Hare 6-15 

6-6 Weighted Passenger Loading for Aircraft at O'Hare 6-17 

6-7 Accident Risk Evaluation 6-20 

7-1 Primary Runway Configuration Identified by ATCT 7-7 

7-2 Average Delay Summary in Good Visibility Conditions 7-16 

7-3 Summary of Aircraft Load (Density) 7-17 



xiv 



SECTION 1 - INTRODUCTION 

1. 1 GENERAL 

This working paper describes and presents the results of the first 
phase of the Advanced Airport Surface Traffic Control (ASTO Systems Concept 
Formulation Study conducted for the Transportation Systems Center (TSO under 
Contract DOT-TSC-678. The report describes the approach followed and the anal- 
ysis techniques employed in the performance of the operations analysis of the cur- 
rent ASTC system for the baseline airport, O'Hare International Airport, Chicago, 
Illinois. It also describes the data resulting from this analysis to draw conclusions 
on the effectiveness of the current ASTC system operations at O'Hare and on the 
effectiveness of the system in projected future operational environments at O'Hare. 

The remainder of this introductory section is intended to provide a 
reference for the descriptions of the study presented in Sections 2 through 6 and 
the summary and conclusions presented in Section 7. Section 1. 2 provides an 
overview description of the Concept Formulation Study to place the O'Hare Opera- 
tions Analysis in context. Section 1. 3 then provides a brief description of the ap- 
proach followed in the operations analysis. 

1. 2 OVERVIEW OF STUDY 

The basic objectives of the Concept Formulation Study are to: 

1. Define and evaluate functional and design concepts for potential 
future ASTC systems configurations. 

2. Estimate the potential for deployment of the alternative system 
configurations at airports in the National Airport Systems Plan 
(NASP). 

The overall approach adopted for the study to achieve these objectives 
is illustrated in a simplified manner in Figure 1-1. This approach represents an 
organization of technical studies providing a logical and stepwise methodology for 
characterization of ASTC system concepts and evaluation of these concepts as a 
basis for estimation of the nature of systems which may be deployed at NASP air- 
ports in an orderly and cost-effective manner. 



1-1 



















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1-2 



In essence, the study structure represents four technical analysis 
phases. The first three tasks shown comprise the airport operations analysis phase 
which is the subject of this working paper. This phase is intended to provide data 
from which an understanding of airport operations and operational needs can be 
developed. This includes a comprehensive and detailed characterization of the 
interrelationships between various organizations and individuals involved in air- 
port operations and areas in which these interrelationships might be enhanced by 
future ASTC systems to increase the effectiveness of airport operations. Thus, 
this phase serves as a baseline for the subsequent study efforts. 

The objective of the second phase of the study (Task 4 - Module De- 
scriptions and Benefits Estimated will be to define, examine, and evaluate func- 
tional performance concepts for potential ASTC system configurations. The under- 
standing of airport operations and operational needs developed in Phase 1 provides 
a reference for definition of future ASTC systems on a modular configuration basis; 
that is, conceptual structuring of future systems as the integration of a number of 
system modules, each intended to support a specific functional performance require- 
ment of an ASTC system. In addition, preliminary requirements analyses, system de- 
scriptions , and data collected at two other airports (Boston-Logan and Hartford-Bradley 
Field) already completed apart from this contract will be provided by the Government 
and utilized to avoid site specific modules. Each functional module will be defined in 
terms of the capabilities to be provided and its interrelationship with other system mod- 
ules and external interfaces. Utilizing the quantitative data on system operations 
developed in Phase 1, estimates of the performance and economic benefits of the 
achievement of these functional capabilities will be developed. 

The objective of the third phase (Task 5 - Mechanization Descriptions 
and Cost Estimates) will be to define, examine, and estimate the costs of functional 
design concepts for system modules; that is, conceptual structuring of the design 
of system modules as the integration of a number of hardware/software elements 
required to provide the functional capabilities defined for the modules in Phase 2. 



1-3 



Design concepts will be developed for mechanizing the system modules by alterna- 
tive equipment technologies (for example, digitized radar or trilateration on 
ATCRBS transponders) and the costs associated with these alternative approaches 
estimated. 

The objective of the fourth phase of the study (Task 6 - Deployment 
Analysis) will be to estimate the deployment potential for the various system design 
approaches defined in Phase 3; that is, estimation of the number of ASTC modules 
mechanized by each of the alternative equipment technologies that could be imple- 
mented at airports in the NASP on a cost-effective basis. This estimation will 
draw upon the understanding of airport operations and operational needs developed 
in Phase 1 to define ASTC functional capabilities that would be required at various 
NASP airports as a function of time. The estimation will also draw upon under- 
standing of performance and economic benefits of various module functional capa- 
bilities developed in Phase 2 and the costs of achieving those functional capabilities 
by alternative technological approaches as defined in Phase 3. This background 
understanding and data base will be combined to identify the types of ASTC systems 
which would be implemented that would most cost-effectively meet the needs of 
various airports and from this the total development potential for implementation 
of system modules by the competing technologies. 

1. 3 DESCRIPTION OF OPERATIONS ANALYSIS 

The technical approach taken in the O'Hare operations analysis is illus- 
trated in a simplified manner in Figure 1-2. 

As a point of departure for the operations analysis a preliminary ex- 
amination of the ASTC system operation at O'Hare was performed using informa- 
tion readily available. Primary sources of this information were documentation 
and materials provided by TSC at the initiation of the contract including maps, 
ASDF films, and communications recording tapes made by TSC in February /March 
1973, and a copy of the O'Hare Airport Air Traffic Control Tower (ATCT) Training 
Manual. The ASDE films were briefly reviewed to gain an impression of the 



1-4 



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traffic flow patterns for the various runway configurations observed. Similarly, 
communications recordings for the several air traffic controller positions in the 
tower cab and airline company communications were listened to in order to gain 
an impression of the basic nature and noticeable differences in the manner in which 
aircraft movements were controlled. These reviews were made against the back- 
ground of maps of airport surface configuration and the description of controller 
activities provided in the Training Manual. Based upon these activities, prelimi- 
nary flow diagrams outlining the estimated flow sequence for departure and arrival 
aircraft were developed. The sequence definitions included the various communi- 
cations and control actions that might be expected to occur in an aircraft's move- 
ments. 

These preliminary operational definitions provided the basis for the 
definition of the approach to be followed in assessing the effectiveness of the O'Hare 
ASTC system. Criteria against which the system effectiveness would be evaluated 
were first identified. Various methods of measuring the effectiveness criteria 
were considered and the most practical measures selected. The resulting effec- 
tiveness criteria were divided into two groups, those which could be directly meas- 
ured from operational flow data and those which could be measured indirectly (i. e. , 
as extrapolations of the directly measured criteria variables). Directly measur- 
able criteria included: traffic flow statistics (e.g. , delay time per operation), 
controller workload (e. g. , communications channel occupancy time), and pilot 
workload (e.g. , communications time per operation). The decision was made to 
utilize traffic flow statistics as the directly measurable criteria for the extrapola- 
tion of indirectly measured effectiveness criteria. Thus, examples of these indi- 
rect criteria included operational cost increase (delay time x cost of operation per 
unit of time\ incremental pollution emission (delay time x pollution emission rate 
per unit of time), passenger inconvenience (delay time x passengers delayed). It 
was also decided that accident risk represented an important variable for effective- 
ness evaluation but that a direct measurement of accident risk was not feasible. 
Therefore, accident risk was considered as an indirect criteria to be measured 



1-6 



in terms of such measurable parameters as the lack of visibility of operations in 
certain areas or number of missed instructions. 

The two preceding activities served as the basis for development of a 
Data Collection and Analysis Plan. The plan identified the data required to support 
the effectiveness criteria measurement, the means for collection of the data, and 
the methods for extraction and reduction of the data collected. In developing the 
plan the TSC collected ASDE films and communications recordings were reviewed 
again in further depth to identify the data which could be extracted from each and 
the most logical procedures for this extraction and reduction. A determination 
was made that the collection of additional data was required for several reasons 
including: the need to obtain clear recordings of ground controller channels*, ac- 
quisition of data for periods of Category I and II operations, and the need to obtain 
data on aircraft movements within the ramp/gate areas (which could not be derived 
from the ASDE films). A brief survey visit was made to O'Hare to derive informa- 
tion needed for finalization of the plan. The major objectives of this survey were 
to: 

1. Obtain brief descriptions of the general procedures followed by 
the various controller positions and identify areas in which spe- 
cific information on the variations in general controller proce- 
dures must be obtained through controller interviews and obser- 
vations in the tower cab. 

2. Identify locations from which traffic movements within the ramp/ 
gate areas could be observed and recorded. 

3 Test various methods for improved communications channels re- 
cording as a basis for design and fabrication of any special equip- 
ments necessary for this purpose. 

The Data Collection and Analysis Plan was then finalized and materials 

for the collection, extraction, and reduction of the data developed including: 



*Because of the method of recording employed, there was substantial interference 
between Outbound (departure) Ground and Inbound (arrival) Ground or clearance 
delivery communications recorded on the tapes. 



1-7 



• Log forms for the extraction and reduction of data from ASDE 
films and communications tapes 

• Log forms for observation/recording of system operations in the 
tower cab and ramp/gate area 

• Preliminary controller interview questionnaire 

• Questionnaires for interviews of airline gate scheduling/manage- 
ment personnel, pilots, and O'Hare Airport management person- 
nel. 

The Data Collection and Data Reduction and Analysis activities were 
then initiated in parallel. Within the Data Collection effort, considerable attention 
was devoted to detailed interviews with several tower cab controllers to obtain 
descriptions of the specific procedures followed in their operations at the various 
positions in the tower cab and their criteria for applying the procedures (e. g. , the 
criteria applied in routing aircraft to or from the runways in use where alternative 
routes are possible). In addition, the interviews were designed to solicit comments 
from the controllers on potential functional concepts for future ASTC systems for 
use in the second phase of the study. 

1. The conduct of interviews with gate scheduling /control personnel 
pertaining to personnel responsibilities and procedures followed 
in managing gate operations. 

2. The conduct of interviews with pilots pertaining to the responsibil- 
ities and procedures followed by flight officers in the operation of 
aircraft. 

3. Utilization of United Airlines and American Airlines control towers 
for the observation of ramp/gate area traffic operations. 

4. Flight Deck Authority for United Airlines aircraft for the purpose 
of observing cockpit operations at first hand. 

Interviews were also conducted with O'Hare Airport management per- 
sonnel to determine the responsibilities and procedures followed by functional units 
in maintaining the operating condition of the Airport and coordinating the operations 
of the units with the ATCT. 



1-8 



The additional operations data collection was performed and included 
periods of simultaneous ASDE film, controller communications recording, obser- 
vation and recording of traffic movements in the ramp/gate areas, and observation 
and recording of controller activities in the tower cab. 

The initial activities in Data Reduction and Analysis were directed 
toward the analysis of selected ASDE films and communications recordings made 
by TSC. Attention was focused on the analysis of selected periods with varying 
traffic operations rates under visual operation conditions for runway configurations 
representative of the normal easterly and westerly operations modes of the airport. 
The resultant data was intended to serve as a background for further analyses of 
the impact of weather conditions on O'Hare operations. As the information col- 
lected by CSC personnel in the field became available it was reduced and inter- 
preted for application in developing narrative and quantitative descriptions of 
O'Hare operations. 

The quantitative data developed in the preceding activity was compiled 
for application in the System Effective Analysis of the current O'Hare operating 
environment and projected future operating environments. A review of the approach 
defined earlier for the effectiveness analysis was made against the background of 
this data and other information acquired during the preceding efforts; in particular, 
a deeper understanding of the O'Hare operational processes and suitable adjust- 
ments to that approach were made. 

Because reliable data on future changes to the operating environment 
at O'Hare could not be obtained in the form required for the planned approach, cer- 
tain assumptions were made regarding future modification of the airport configura- 
tion. No attempt was made to quantitatively extrapolate the impact of these changes. 
However, qualitative assessments of the impact of these changes, particularly 
with respect to ground taxi and departure delays, were made. 



1-9 



With respect to the subject of accident risk, situations observed of the 
ASDE film analysis and the understanding of O'Hare operations developed through 
the field activities were drawn upon to develop qualitative assessments of poten- 
tials hazardous situations which merit attention and possible near term correction 
through ASTC system improvements. 

The plans, procedures followed, and results developed in all the pre- 
ceding activities served as the basis for the preparation of this working paper. 



1-10 



SECTION 2 - OPERATIONS ANALYSIS APPROACH 

2. 1 GENERAL 

The purpose of this section is to describe in detail the technical ap- 
proach followed in performing the operations analysis and effectiveness analysis 
for the O'Hare ASTC system and the rationale for this approach. 

2. 2 ESTABLISHING THE BASIS FOR ANALYSES 

As the first step taken, a preliminary definition of the ASTC system 
operation was developed. Maps of the O'Hare Airport configuration were studied 
to become familiar with the layout of the runways and taxiway network. 

The Chicago O'Hare Airport Air Traffic Control Tower (ATCT) Train- 
ing Manual was reviewed to obtain a general understanding of the responsibilities 
and duties of the tower cab positions and of positions in the TRACON as they inter- 
face with the airport operations. The Manual includes maps illustrating a number 
of basic runway utilization configurations and associated taxi flow patterns which 
provided a basic understanding of operational flow patterns. 

This understanding was further developed by review of a number of 
ASDE films taken by TSC in February and March, 1973. The films were studied 
to further examine the traffic flow for the various specific operational configura- 
tions in relation to: 

1. Emanation of traffic from or exit to the passenger terminal 

2. Taxi to and from the various runways in use 

3. Aircraft delays or stops enroute to or from the runways 

4. Departure aircraft queuing for the various runways 

5. Interleaving of departures and arrivals in cases of mixed opera- 
tions on the same runway and in separated operations on crossing 
runways 



2-1 



Controller and airline communications channel recordings made by 
TSC simultaneously with the ASDE films were reviewed to gain an impression of 
the communications between tower and airline personnel. Brief periods of the 
communications recording tapes for various controller positions and airline chan- 
nels corresponding to the ASDE films previously reviewed, where available, were 
listened to for the purpose of generally classifying: 

1. The stages in the aircraft flow in which communications take 
place with the various operational personnel 

2. The nature of the communications control discipline followed 

3. The nature of the information transmitted by the various person- 
nel involved 

4. Any distinctions between control procedures and associated com- 
munications arising from the operating configuration and condi- 
tions 

Based upon the preceding activities, simplified flow charts illustrating 
the basic stages of the passage of aircraft through the system were developed for 
both departure and arrival operations. The flow charts are illustrated in Figures 
2-1 and 2-2 for departure and arrival operations, respectively. Superimposed on 
these diagrams are indications of the controller positions involved in the process- 
ing of the aircraft throughout the various stages of operation. 

The purposes in developing these flow charts were twofold. The first 
was to provide a continuing reference for project personnel in the subsequent in- 
vestigations of the ASTC operation. The second, and more important, was to 
serve as the basis for defining the approach to be followed in studying the ASTC 
system and analyzing the effectiveness of its operations. The flow charts were 
examined to identify: 

1. Stages at which the flight could experience delays in its process- 
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2. Areas in which detailed investigation of the procedures followed 
at controller positions was essential in understanding the ASTC 
system operation, developing qualitative workload estimates, and 
formulating concepts for future ASTC systems. 

3. Areas in which detailed investigations of the procedures followed 
by airline operations and flight personnel were essential in under- 
standing terminal facilities usage and pilot information require- 
ments in relation to aircraft control, and in formulating concepts 
for future ASTC systems. 

4. Stages of operation at which reduced visibility conditions impact 
on the system and specific areas of investigation to quantify this 
impact on various system operational personnel. 

5. Stages of operation at which there is a risk of accident and spe- 
cific areas of investigation to qualitatively or quantitatively exam- 
ine the potential hazards. 

As an example, the stages of operation at which aircraft could experi- 
ence delays identified by the review are outlined heavily in Figures 2-1 and 2-2. 

The results of the review then served as the basis for the following: 

1. Preliminary definition of criteria and measures for assessment 
of the ASTC system effectiveness 

2. Definition of the data required for the defined system effectiveness 
analysis approach 

3. Preliminary identification of the appropriate sources of the data 
required and the means for extraction of the data from the sources 

4. Identification of areas in which further clarification of operational 
procedures or potential data collection methods was necessary for 
finalization of the analysis plan. 

A survey visit was then made to O'Hare Airport to satisfy the informa- 
tion requirements identified in 4 above. The survey activities included: 

1. Discussions with O'Hare ATCT personnel to determine the actual 
procedural flow of task activities for each controller position in 
the tower cab. The discussions identified both the basic procedural 
flow for each position and areas in which there is some variability 



2-5 



in individual controller procedures which would have to be deter- 
mined through personnel interviews and observations in the tower 
cab. 

2. Discussion of the problems encountered in the use of the current 
ASDE Brite equipments. It was learned that the ATCT had pre- 
viously determined the coverage limits of the equipments and that 
the results were presented on a map of the airport which would be 
provided for the study. 

3. Testing of a new method for recording of controller communica- 
tions channels directly from the communications equipment to 
eliminate the problem of overlap and interference between the 
Outbound (departure) Ground and Inbound (arrival) Ground com- 
munications encountered on the TSC recordings. The design re- 
quirements for the equipments that would be required to accom- 
plish this without interference with FA A channels were worked 
out with ATCT personnel as inputs to the design and fabrication of 
the equipments. 

Based upon the results of this survey a Data Collection Analysis Plan 
was finalized. The data collection and analysis procedures followed in the subse- 
quent operations analysis based upon this plan are described in the following para- 
graphs. 

A major aspect of the plans for analysis of the O'Hare ASTC system 
was a decision to examine the airport operations in terms of two modes of opera- 
tion. Review of the ASDE films and associated data provided by TSC and the maps 
of runway/ taxiway usage configurations provided in the ATCT Training Manual in- 
dicated that O'Hare operations could essentially be divided into two modes. These 
modes were "Arrivals from the East" and "Arrivals from the West. " As informal 
discussions with ATCT personnel indicated that the arrival runways were selected 
first in determining the runway configurations to be employed under various oper- 
ating conditions, this approach in defining the modes of operations in this manner 
was reasonable. 



2-6 



Thus, the ASTC system effectiveness analysis and supporting func- 
tional analysis approaches, described in the following Sections 2. 3 and 2. 4, were 
devised to provide an examination on this basis. Various TSC data collection runs 
and, subsequently, CSC data collection runs representing operations in these 
modes were selected for detailed analysis. 



2-7 



2. 3 O'HARE OPERATIONS EFFECTIVENESS ANALYSIS APPROACH 

2.3.1 General 

This paragraph summarizes the approach and methodology developed 
to evaluate the effectiveness of ASTC Systems at O'Hare. The proposed methods 
have general applicability to other airports and will be useful in evaluating the 
effectiveness of new ASTC concepts and techniques. While the methods offer this 
broad capability for future evaluations, attempts to apply them must be accom- 
panied by a rather extensive data collection program at the site under evaluation. 
Specifically, the data collection and reduction procedures used at O'Hare and dis- 
cussed throughout this report must be employed to accomplish the effectiveness 
evaluation at other airports. 

The objective of this analysis is to assess effectiveness by combining 
measured airport data with statistical considerations at O'Hare in order to evaluate 
the following derived effectiveness parameters: 

Fuel Consumption 
Pollution Emission 
Operating Costs 
Passenger Inconvenience 
Accident Risk 

This is accomplished by reducing raw data into a form which will pro- 
vide a direct measure of: 

• Airport surface holds, delays and service time 

• Controller communications workload 

• Cockpit crew communications workload 

• Communications incidents 

These direct measures are analyzed in conjunction with the following 
statistical considerations to determine a measure of effectiveness: 



2-8 



Airport operational demand 

Airport weather profile 

Aircraft profile 

Airport operating modes 

Aircraft engine fuel consumption factor 

Aircraft engine pollution factor 

Aircraft operating cost factor 

Aircraft loading factor 

This analysis permits the calculation of a numerical effectiveness 
score(s) for each derived parameter. Since these parameters are not independent 
and their relative significance is a highly subjective consideration, this method- 
ology stops short of providing a composite effectiveness score. Nevertheless, a 
combinatory method could be added in the future if a composite score is desired. 
This would involve assigning subjective weighting factors for each effectiveness 
parameter, calculating a weighted score, and adding the weighted scores of each 
parameter. 

The following paragraphs describe the general approach for the indi- 
vidual parameter analysis. Detailed calculations and measured data consistent 
with this approach are contained in Section 6 of this report. 



2.3.2 



Fuel Consumption Assessment 



In view of the energy crisis, minimization of aircraft fuel consumption 
is a reasonable ASTC System goal. This parameter is directly related to mea- 
sured and statistical factors which are related by the following overall formula 



FC ACT = [ST + HT1 X 



n. 

— x FF 
n 1 



(1) 



where 



FC 



ACT 



Estimated actual gallons of fuel consumed by aircraft on the 
airport surface during a one hour measurement period 



2-9 



ST = Measured total service time (i. e. , time for all AC to travel be- 
tween ramp and runway or runway and ramp without stopping) 
during a one hour measurement period 

HT = Measured total holding time (i. e. , time spent by aircraft in a 
holding status) during a one hour measurement period 

n. 

— = Ratio of a specific aircraft type to the total at O'Hare as deter- 
mined from the aircraft profile 

FF. = Fuel factor (i.e., the gallons of fuel consumed per idle engine 
minute for the ith aircraft type) 

This calculation will determine the estimated fuel consumption during 
a specific measurement period. 

It is important to specify the operating conditions which existed during 
the measurement period so that measured data which was obtained over a limited 
sampling period could be statistically extrapolated to an annual consumption factor. 
The important operating conditions for this extrapolation are: 

• Aircraft operations per hour (measured/desired) 

• Weather conditions (good/poor) 

• Runway modes (west/east arrivals) 

By specifying the actual measurement conditions and by recognizing 
the probability of having various conditions during the year, the annual fuel con- 
sumption could be estimated. 

Finally, it is important to identify the potential improvement which 
can be obtained through the use of an optimum ASTC System. This is accomplished 
by letting HT = in equation (1) thereby providing an estimate of the minimum 
gallons of fuel required. 

By forming the ratio of annual minimum fuel to annual estimated actual 
fuel the ASTC system can be given a fuel consumption effectiveness score which 
would optimally equal unity. 



2-10 



This analysis assumes a linear relationship between fuel consumption 
and aircraft surface travel delays. For the most part this assumption is reason- 
able; however, it is possible that an ASTC system could be devised wherein this 
was not the case (viz. , a system where tugs or cables transport aircraft to and 
from the runway). Another consideration is the fact that limited fuel supplies 
could make the impact of a fuel-saving ASTC System much more significant. For 
example, it could easily determine whether or not airlines could also determine 
the number of flights that an airline could schedule and thereby control its business 
potential. In summary, while the linear relationship is reasonably valid, the 
impact of fuel conservation measures could exhibit effectiveness discontinuities 
which make fuel-saving ASTC systems even more attractive than this methodology 
indicates. 

2.3.3 Pollution Emission Assessment 

The primary environmental consideration associated with aircraft 
surface travel is air pollution. While noise is a consideration, surface travel 
noise is reasonably well confined to the immediate airport vicinity. The main 
noise abatement consideration involves takeoffs and initial climb maneuvering as 
it affects surrounding communities. While a substantially reduced level of surface 
noise pollution could result in simplified airport terminal building construction 
and better working conditions at the terminal, it is doubtful that future ASTC sys- 
tems will be capable of such vast reductions in noise level. Nothing short of the 
tug or cable transports mentioned previously could accomplish these levels of 
noise reduction. 

The air pollutants of major interest are carbon monoxide (CO), sulfur 
dioxide (SO ), and various hydrocarbons. These are generally measured in parts 
per million (ppm). As in the case of fuel consumption, pollution is a function of 
delays and the aircraft profile and individual aircraft pollution factors at idle 
engine speed. Pollution emission can be calculated as follows: 



2-11 



PE ACT = [ST + HT] X 



n. 

— x PF. 

n 1 



where 

PE = The estimated total actual pollutants emitted during the test 

hour 

PF. = Air pollution factor (i. e. , ppm of pollutants per idle engine 
minute for the ith aircraft type) 

While the extrapolation of this effectiveness measure to an annual esti- 
mated value is not as significant as in the fuel consumption case, it is of major 
medical concern to people who are continually in the airport vicinity. Extrapola- 
tion to the annual figures will be performed in a manner analogous to that used for 
the fuel consumption parameter. The resulting actual and minimum annual pollu- 
tion levels could be compared then and an effectiveness score determined on that 
basis. 

Of additional interest to pollution assessment is the air quality index 
during peak operating and adverse environmental weather conditions. Brief 
periods of excessively unhealthy air represent a serious problem to all personnel 
and passengers regardless of the time spent in the airport vicinity. The proba- 
bility of having excessively unhealthy air (P ) can be calculated by estimating 

UHA 

the joint probability of having a temperature inversion and peak operations through- 
out the year. The complement of this probability (1 - P ) provides another 

UxiA 

measure of air pollution effectiveness which is optimally equal to one. 

2.3.4 Operating Cost 

Airline operating costs are directly proportional to surface traffic 
delays since many of the elements which comprise this cost are based on the time 
between unblocking and blocking the aircraft at the gate, e.g. , crew hours, engine 
hours. To a certain degree surface traffic delays can be attributed to the airline 



2-12 



itself as a result of ineffective gate control and scheduling. For the most part, 
however, these delays can be attributed to the ASTC System of the airport under 
evaluation. For this analysis airline operating costs will be estimated on a per 
aircraft type basis. These costs include: crew costs (salary /overhead) , fuel 
and oil, insurance, taxes, air frame maintenance, engine maintenance, deprecia- 
tion, rentals, maintenance burdens, and other miscellaneous expenses associated 
with the time an aircraft is in use. Not included are estimates for the ticketing 
system, reservation system, management, gate fees, etc. Airline operating cost 
will be computed from the formula: 



OC ACT = [ST + HT] x 



li 



n. 

x CF. 



_ 1 



where 

OC = Estimated total actual cost per test hour 

and 

CF. = Average airline cost in dollars per block minute for the ith 
aircraft type 

The estimated actual value for a specified measurement period was 
statistically extrapolated to an annual estimate. In addition, by letting HT = 
in the formula, the minimum cost was determined such that the effectiveness 
score could be calculated as the ratio of the minimum to the actual annual cost. 

2.3.5 Passenger Inconvenience Assessment 

Passenger inconvenience is a difficult parameter to assess, since 
inconvenience can vary considerably among passengers based on individual cir- 
cumstances. There are at least two airport surface travel factors which con- 
tribute to passenger inconvenience; however, the relative significance of these 
factors is not easily determinable. The general factors involved are: 



2-13 



• Inconvenience due to delays 

• Inconvenience due to lack of comfort 



The delay factor is assessedby measuring the total ground delay time 
during a test hour and by using the formula 



where 



and 



PD ACT - [HT] x 



v- n. 

y ^ x pl. 

L^ n 1 



PD = The total number of passenger delay minutes during the test 

AC./ 1 , 

hour 



PL. = The average passenger loading factor for the ith aircraft type 

The passenger delay effectiveness score is assessed by calculating 
the estimated actual passenger ground travel minutes for the year using the 
formula 



PT ACT = [ST + HT1 X 



v-^ n. 

y + x pl. 

L n 1 



and the statistical extrapolation factors. The minimum passenger travel minutes 
can be computed for the year by letting HT = 0. The effectiveness score is then 
determined as the ratio of the minimum to the actual annual passenger ground 
travel minutes. 

The comfort factor is assessed by measuring the number of starts 
and stops which the aircraft makes during airport ground travel using the 
formula 



2-14 



PC ACT = [2HN1 X 



— x PL. 



where 



and 



PC. „ = Total number of passenger starts and stops during the test 
hour 



HN = The number of aircraft holds during the test hour 



Using the statistical extrapolation factors, the annual estimate for 
passenger starts and stops can be determined. The optimum value for this 
parameter is equal to zero. 

2.3.6 Accident Risk Assessment 

Section 6 provides a detailed discussion of specific observed situations 
which could be viewed as potentially hazardous. By computing the ratio of the 
number of these observed situations to the number of actual operations during the 
tests it is possible to assign an accident risk potential computed as 

PA = |L x 100 

where 

PA = Accident risk potential in percent 

HI = Potentially hazardous incidents observed 

TO = Total operations observed 

Unfortunately, the assessment of the hazardous nature of these incidents 
is rather subjective. Furthermore, the test period provides a small base upon 
which to assess this parameter, since the frequency of occurrence of hazardous 
situations is fortunately so low. 



2-15 



A more generalized approach toward accident risk assessment is also 
provided based on the following measured factors: 

• Controller communications workload* 

• Crew communications workload 

• Communications incidents 

The general assumption is that increased controller communications 
workload, increased crew communications workload, and a large number of com- 
munications incidents yield an increased potential for accidents attributable to the 
ASTC System. 

The controller communications workload is measured in terms of the 
percentage utilization of the ATC frequency where 

CT 
CTW = ^~ x 100 
60 

where 

CTW = Controller communications workload during the one hour measure- 
ment period expressed as percent of channel occupancy 

and 

CT = The total duration of communication transactions during the test 
hour 

The crew communications workload is keyed to ATC "chatter", i. e. , 
by the number of communications messages monitored by individual AC crews 
during the one hour measurement period where 






*Although the total controller workload includes non-communications, observations 
during the study indicated that they are performed for the most part at the same 
time the controller is in communication with the associated flight. Therefore, 
computation of a total workload including both components would produce a higher 
estimate of total working time than is actually experienced. 



2-16 



CTN 



1 



where 



CCW= The cockpit crew workload measured as the number of communi- 
cation transactions monitored by the cockpit crew while in the 
ASTC system 

CTN = The total number of communication transactions which took place 
during the total measurement period on the kth ATC frequency 

T = The average time that an aircraft was on the kth ATC frequency 
during the test period 

The number of communications incidents (CI) was also measured for 
each ATC frequency. This number will be used directly to assess his incident 
risk factor. 

Based on a statistical extrapolation to the annual estimate for these 
three accident risk factors, an annual estimated accident risk potential expressed 
as three separate scores is determined. 

2.3.7 Summary of Effectiveness Measures 

Table 2-1 provides a summary of the derived effectiveness parameters 
included in this effectiveness assessment methodology. The key measurement 
factors, the effectiveness measures, and the optimum effectiveness scores are 
also included for consideration. Section 6 demonstrates the application of these 
concepts to the evaluation of O'Hare ASTC effectiveness. 



2-17 



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2-18 



2. 4 METHODOLOGY FOR FUNCTIONAL ANALYSIS OF ASTC SYSTEM 

OPERATION 

In performing the functional analysis of the O'Hare ASTC System oper- 
ation, the analysis activities were primarily directed toward developing the data 
required to support the ASTC system effectiveness analysis approach previously 
described. In essence, this required more than just the derivation of quantitative 
data describing aircraft movements and communications. It also required the de- 
velopment of an understanding of the environments, constraints, and procedures 
followed by the various operational personnel involved in the passage of aircraft 
through the ASTC System as a background for meaningful interpretation of the 
quantitative data. Thus, the development of the information base for the functional 
analysis of the ASTC System consisted of the collection, reduction, and analysis 
of operational movements and communications data and the conduct and analysis of 
interviews with representative samples of the operational personnel. 

The efforts in each of these areas for various aspects of the airport 
operation are described below. 

2. 4. 1 Controller Task Analysis 

The controller task analysis effort was effectively divided into three 
distinct but related areas: interviews with representative controller personnel; 
controller communications recordings analysis; observation and analysis of physi- 
cal task activity. 

2. 4. 1. 1 Controller Interviews 

Arrangements were made with the O'Hare ATCT and Great Lakes Re- 
gion for the availability of a number of representative tower cab controller person- 
nel to be available for in-depth interviews on traffic control procedures employed 
at the various controller positions. 

A draft Controller Interview Questionnaire was developed. The inter- 
view was designed to incorporate questions covering the operational procedures 



2-19 



followed by the subject when operating the Clearance Delivery, Outbound Ground, 
Inbound Ground, and Local Control positions under normal (good) visibility condi- 
tions and poor visibility conditions. The opportunity was taken to include a number 
of questions intended to solicit controller opinions on potential functional perform- 
ance and design concepts for future ASTC systems. The interview was designed 
to be conducted verbally and included use of graphical representations of selected 
future ASTC System concepts. 

The draft interview was tested and recorded on tape for two control- 
lers. However, the interview with the second controller was terminated because 
of shortcomings of the draft questionnaire. Based on the experience gained by the 
interviews and difficulties experienced in attempting to transcribe the recording 
for the first controller, it was determined that revisions to the questions asked 
and method of recording the responses were required. A revised interview ques- 
tionnaire was developed. It consisted of two parts. The first was composed of 
questions to which simple responses could be expected and recorded directly on 
the interview form. The second was a written supplement composed of ques- 
tions for which the responses could be expected to be more extensive or complex 
and on which the controller would record his responses. This revised interview 
format was then employed for the second test controller and eight additional con- 
trollers. 

When completed, the interviews were analyzed to determine a com- 
posite of the results identifying the predominant response for the various ques- 
tions and the percentage of controller interviews providing this response. In 
many areas the controller responses were found to indicate a high degree of stand- 
ardization of procedures and decision criteria where alternative techniques might 
be applied. 

The results of this analysis served as a baseline reference for the 
controller communications analysis and, most particularly, for the observations 
of controller activities in the tower cab. 



2-20 



A sample of the Controller Interview Questionnaire form employed is 
included in Appendix A. Completed interview questionnaires are included in the 
O'Hare Operations Analysis Data Supplement. 

2. 4. 1. 2 Controller Communications Recordings Analysis 

Magnetic tape recordings of communications transactions between con- 
trollers and pilots (or surface vehicles^ are uniquely useful in studying controller 
workload as these communications represent the major measurable element of his 
activity. Analyses of such recordings were performed to permit direct assess- 
ment of the controller communications activity and, in particular, for determina- 
tion of the amount of time spent in communications to all aircraft and to individual 
aircraft. The analysis identified in detail the nature of the communications in 
terms of the information transmitted between controllers and pilots and the vari- 
ous types of control disciplines employed by the various positions. Further, the 
data was derived in such a form as to permit limited extrapolation of the resultant 
data at the observed traffic levels to higher traffic levels for use in the future 
O'Hare ASTC system effectiveness analysis. 

To generate a data base for analysis, the tape recordings for various 
positions were examined in depth to classify the communications in terms of: 

1. Individual communication transactions between controller and 
specific aircraft in chronological sequence. * 

2. Message elements per communication transaction. The message 
element classifications were defined as the most descriptive re- 
garding the nature of the information transmitted within the trans- 
action. 



*A communications transaction was defined to include all the transmissions of 
both the controller and pilot necessary to complete the communication and any 
pauses in the conversations prior to its completion. 



2-21 



3. Primary communication transaction designations, i. e. , the pri- 
mary function of the transaction in terms of the message elements 
communicated, wherever possible. 

Message element classifications employed were derived from the 
communications analysis procedures currently in use by the FA A at NAFEC. 
These procedures are employed extensively in field studies of ATC facilities 
throughout the United States and in experimental studies at NAFEC. The rationale 
for selection of this approach is that it utilized well-defined standard definitions of 
ATC communications and would permit later comparison of the results of this study 
with studies of communications at other airports performed by NAFEC personnel. 
FAA message classification identifications were directly accepted or modified 
slightly to permit further refinements for the purposes of this study. For exam- 
ple, the basic FAA classification of a Control Instruction (Message Identification 
No. 110) was expanded to permit identification of aircraft sequence instructions 
or instructions related to penalty box holds by ground controllers as 111 and 112 
identification numbers, respectively. The message element identifications and 
general classifications are listed below for the various controller positions. 

Clearance Delivery 

180A Clearance requests by pilot 

180B Clearance repeat requests or checks by pilot 

180 Clearance delivery 

180S Special clearance delivery 

(Communication contact by controller after initial contact) 

150 Request to push back aircraft by pilot 

210A Broadcast call for clearance requests by controller 

21 OB Broadcast call for taxi requests by controller 

230 Handover 

310 Position reports 

420 Taxi requests by pilots 

450 Weather related communication 



2-22 



500 Communication incident (No response to call by controller or 

pilot) 

Inbound Ground Control 

110 Control instruction (other than hold) 

111 Sequence instruction (Instruction to follow another aircraft) 

112 Penalty box or holding area instruction and advisories 

120 Hold instruction 

140 Yield instruction* (Instruction to control movement to yield 

right of way to another aircraft) 

150 Clearance to pilot to enter ground control system 

160 Clearance to pilot to enter ground control combined with 

hold instruction 

310 Position report (Controller request and pilot response) 

311 Destination or gate of incoming aircraft (a specific type of 
position report) 

410 Traffic advisories 

420 Taxi request by pilot wishing to move aircraft between hangar 

and terminal, etc. 

470 Gate status information 

500 Communication incident 

Outbound Ground Control 

110 Control instruction 

111 Sequence instruction 
120 Hold instruction 
140 Yield instruction 

150 Clearance to pilot to enter ground control system 



*In the NAFEC message classification system this message identification is used 
for Speed Control instructions. This classification was adopted for the Yield In- 
struction since it is essentially an instruction to the pilot to adjust the speed of 
his aircraft's movement so as to permit another aircraft the right of way at an 
intersection. 



2-23 



160 Clearance to pilot to enter ground control combined with hold 

instruction 

230 Handover 

310 Position reports 

410 Traffic advisories 

500 Communication incidents 

Local Control 

110 Control instruction (Runway turnoff or taxi) 

120 Hold instruction 

151 Takeoff clearance 

152 Landing clearance 

160 Clearance with runway hold (e. g. , position and hold) 

230 Handover 

310 Position reports 

450 Weather reports (winds, visibility, etc. ) 

500 Communication incidents 

Communication transactions were timed out for each magnetic tape 
recording, usually of one hour duration. During the early stages of the communi- 
cations recording analysis an attempt was made to record the absolute start and 
stop time for each communications transaction. It was intended that these measure- 
ments would be used to: (1) compute the duration for each transaction; (2) provide 
a basis for statistical computation of the durations for various message types; 
(3) trace the aircraft between controller positions; and (4) match communications 
with air movements data in the ramp areas, taxiways, and runways. However, 
this was found to be extremely time consuming to accomplish satisfactorily and 
within the time and funds available. Thus, the procedure settled upon was to ac- 
cumulate, using a stop watch, the times spent in all communications transactions 
over a test period. The total communications activity time was then divided by 
the total of transactions to compute the average duration of a communications 
transaction. 



2-24 



Examples of the communications transactions analysis form employed 
for each controller position is presented in Appendix A. 

The data obtained in the above data base generation was reduced to 
form the following parameters: 

1. Clearance Delivery 

Average number of communication transactions (CD required per 
aircraft (AC) 

Average CT duration 

Percentage channel occupancy time required by transactions 

Average time lapse between first contact and handoff 

2. Outbound Ground Control 

Average number of communication transactions (CT) required per 
aircraft 

Average CT duration 

Percentage time occupancy required by transactions 

Average number of required message elements per aircraft 

Average number of required control type instructions required 
per aircraft 

Number of departures per hour 

3. Inbound Ground Control 

Average number of transactions required per aircraft 
Average CT duration 

Percentage time occupancy required by transactions 
Average number of message elements required per aircraft 



2-25 



Average number of control type instructions required per aircraft 

Number of aircraft handled per hour 

4. Local Control 

Average number of transactions required per aircraft 
Average CT duration 

Percentage time occupancy required by transactions 
Average number of message elements required per aircraft 
Aircraft handled/hour 

The large amount of magnetic tape data made available by TSC for 
February/ March 1973 was collected when the traffic volume was high. Unfortu- 
nately, the data was subject to adjacent channel interference. This was particularly 
so for the Ground Control positions, rendering reduction to be extremely difficult 
or impossible with accuracy. Therefore, only TSC Run #33 was analyzed for the 
Inbound Ground Control position from this source of data. 

Further recordings were made by CSC in January 1974 on smaller 
traffic volumes (due to reductions in scheduled operations based on the national 
fuel shortage). These recordings are the primary source of data for the Ground 
Control positions in this report. 

2. 4. 1. 3 Tower Observation and Analysis of Controller Task and Non- Commu- 
nication Activities 

During several periods project analysts were stationed in the tower 
cab to observe and record the overall nature of operations in the cab and the spe- 
cific task activities of the various controller positions. 

General observations were made in relation to the observers' impres- 
sions of the working interface between control positions and the effect of the traf- 
fic environment and operating conditions on controller activities. During these 
periods a number of particularly significant events were observed and the actions 



2-26 



taken by controllers were noted. Where the situation permitted after the events 
were resolved the particular problems were discussed with the controllers affected. 
The information gained from these general observations primarily served to sup- 
plement the information on controller procedures obtained through the previously 
discussed controller interviews. In addition, it served to supplement the detailed 
observations of controller non- communication activities. 

Several attempts were made to observe and chronologically record the 
activities of individual control positions in relation to all aircraft controlled over 
a period of one-half hour. However, these attempts were all unsuccessful for a 
number of reasons. Primarily, no position could be found where the observer 
could station himself such that he could accurately observe all activities and/or 
relate those activities to particular aircraft (as planned) without becoming an ob- 
struction to the operations of the control position he was observing or of other con- 
trol positions. Secondarily, the short durations of the non-communications tasks 
being observed did not permit the recording of all the information desired, partic- 
ularly the time involved, without missing or losing data for the next activity when 
they performed in immediate time sequence. Therefore, this approach was dropped. 

Instead, a two-step approach to the recording of controller activities 
was adopted. In the first step, the analysts concentrated on observing and record- 
ing the performance times for one non- communications task activity at a time. 
For each task activity a number of stop watch measurements of the performance 
times were made for three different controllers. Since ground and local control- 
lers were observed to be continually scanning the traffic situation visually or em- 
ploying the ARTS or ASDE Brite display, no attempt was made to measure this 
type of non-communications activity. 

In the second step, a number of departure and arrival flights were se- 
lected for a detailed Flight Trace. In performing the Flight Trace the particular 
flight was followed from its entry into the ASTC System to its exit from the System. 
For arrivals, the trace was started when the aircraft was established on the runway 



2-27 



course and was located at approximately the 10-mile marker ring on the Local 
Control ARTS Brite display. The trace was completed when the aircraft docked 
at its gate. For departures, the trace was started in all but one case when air- 
craft began its pushback; in the one case, the trace was started when the flight 
called for its clearance. The trace was completed when the flight was handed off 
to Departure Control and the flight strip dropped down the Flight Strip Tubes to 
Departure Control. The aircraft was followed through all control positions in- 
volved in its passage through the system and the activities, both communications 
and non- communications, of each controller with respect to the flight recorded. 

The performance times measured for the various individual activities 
were utilized to derive statistical descriptions for the activities. These descrip- 
tions were used to compute total non- communications task activity times for each 
control position as a function of traffic volume. 

2. 4. 2 Aircraft Flow Analysis 

The aircraft flow analysis procedure was designed to examine the 
movements of aircraft traffic within three major areas of the airport. These in- 
cluded the ramp areas and the Ground Controllers' and Local Controllers' areas 
of responsibility. Each aircraft moves through these areas irrespective of 
whether it is a departure or arrival. 

For the purposes of the analysis, these areas were defined as follows.- 

1. Ramp area - that area between the terminal concourses and inside 
a line defined by the outer edges of adjacent fingers. * 



*It was not possible to examine with any accuracy traffic flow within the cargo or 
hangar areas. 



2-28 



2. Ground Controllers' area - that area traveled by an aircraft be- 
tween the ramp area and end of the departure queue (waiting line) 
or exit from the landing runway. * 

3. Local Controllers' area - the area including the departure queues 
and the active runways. * 

The variables which have been considered in the aircraft flow analysis 
fall into two categories, namely, independent and dependent. The dependent vari- 
ables which were measured include: 

Runway operations time 

Taxi service time (Nominal movement time excluding delays) 

Delays 

Safety (accident risk) 

The independent variables which influence the above dependent param- 
eters and which have been considered in this analysis include: 

Runway (R/W) configuration - arrivals from the east vs arrivals from 
the west 

Traffic Volume - operations/hour and other parameters to be defined 
later in this report 

Weather (visibility) conditions 

Gates - number, scheduling, availability 

Routing procedures 

Locations at which aircraft may be held because of the traffic flow 
pattern or gate unavailability for occupancy 

Aircraft flight phase - arrival, departure 



*It was recognized that these definitions may not reflect the actual division of air- 
craft control between these positions. However, the ASDE films which served as 
the major source of data for these analyses do not permit identification of the 
points at which actual transfer of control was accomplished in all cases , 



2-29 



Based upon these definitions of the areas of interest, the aircraft flow 
analysis was effectively divided into three distinct but related areas: interviews 
with ATCT personnel and review of ATCT records; detailed analysis of ASDE 
films; and direct observation and recording of traffic movements within selected 
ramp areas. The independent and dependent variables considered in each of the 
areas are summarized in Table 2-2. 

Table 2-2. Examination of Aircraft Flow Variables 





Flow Analysis Methodology Area 


ATCT Interviews 


ASDE Film 


Ramp Area 


Aircraft Flow Variable 


and Records 


Analysis 


Observations 


INDEPENDENT 








Runway Configuration 


X 


X 




Traffic Volume 


X 


X 


X 


Weather Conditions 


X 


X 




Gates 


X 




X 


Routing Procedures 


X 






Aircraft Hold Locations 


X 


X 


X 


Aircraft Flight Phase 


X 


X 


X 


DEPENDENT 








Runway Operations Time 




X 




Taxi Service Time 




X 


X 


Delays 




X 


X 


Safety (Accident Risk) 




X 


X 



2-30 



2. 4. 2. 1 ATCT Personnel Interviews and Records Review 

Extensive interviews were conducted with ATCT personnel. These 
interviews were conducted with members of the operations planning staff and with 
Watch Supervisors. The objectives of these interviews were to determine: 

1. The primary runway configurations employed at O'Hare 

2. The criteria used in determining the runway configurations to be 
employed for operations under various operating conditions 

3. The operating minimums for the various runways that influence 
their use during lower visibility conditions 

4. The aircraft taxi routing patterns employed for the various pri- 
mary runway configurations 

With seven runways oriented in several compass directions there are 
a large number of potential combinations that could be employed to achieve con- 
figurations appropriate to a wide range of operating conditions. However, many 
of these potential configurations are essentially variations of the primary config- 
urations to meet particular constraints, e. g. , runway closing for maintenance 
operations. Thus, the decision was made to focus on the 11 primary configurations 
identified by the ATCT personnel. 

In deriving items 1, 2 and 4 above, specially prepared illustrations of 
the airport surface and passenger terminal layout were used. A separate illustra- 
tion sheet was used for each configuration. The primary arrival and departure 
runways were noted as well as additional runway usage for departures and VF 
arrivals by general aviation and STOL commuter aircraft. Particular conditions 
affecting the choice of the configuration were also noted. Finally, the primary 
and alternate taxi routes for departure and arrival aircraft were traced on the il- 
lustration. The results of these interviews are provided in Section 3. 

Arrangements were made for a review of ATCT records to determine 
the degree to which various runway configurations are employed by the ATCT. It 



2-31 



was determined that the ATCT did not compile its records in the manner desired 
and had not as yet compiled the runway usage data for FY1973 or calendar year 
1973. Therefore, access was provided to the collection of Daily Work Summary 
sheets that would ordinarily be used to compile this data. Because of the volume 
of such data, it was determined that a sampling process would be employed. Sum- 
mary sheets for at least one weekday in each week within a month were selected 
basically at random, with the one exception that care was taken to select sheets 
for different days of the week within each month. The following data was extracted 
from the summary sheets: 

1. The runway configurations employed during the normal busy hours 
of 7 a. m. to 11 p. m. 

2. The hours within which the various configurations were employed. 

3. The arrival and departure traffic volumes for each different run- 
way configuration period. 

This data was employed to compile a summary of the easterly and 
westerly modes of operation for the airport. 

2. 4. 2. 2 ASDE Film Analysis 

Detailed analysis of the ASDE films provided by TSC and made during 
this study period served as the primary source of data for the analysis of aircraft 
traffic flow during the ground taxi, takeoff, and landing phases of operations. 
ASDE film analyses were performed in three steps with the first being a deriva- 
tion of overall traffic flow statistics and the last two focusing on specific aspects 
of the flow process; i. e. , causes and locations of aircraft holds and potentially 
hazardous incidents. 

2. 4. 2. 2. 1 Aircraft Flow Statistics 

The ASDE films were made using a time-exposure control camera. A 
frame was taken every two seconds; one second of exposure followed by a pause of 
one second. A digital clock was mounted on the ASDE monitor and within the area 



2-32 



of view. The films were then produced using a special film analysis projector 
providing variable speed and frame-by- frame control. 

The method of data extraction involved examination of the operations 
for one runway at a time. Each arrival aircraft was identified during its approach 
phase and traced in time until it reached and entered the ramp area. The ASDE 
films did not permit accurate examination of the aircraft movements within the 
ramp area. For this reason it was necessary to treat departure aircraft as 
"arrivals in reverse" and to trace them backward in time from takeoff to emana- 
tion from the ramp area. Aircraft identity and, except in some cases (e. g. , 747s), 
aircraft equipment type could not be determined from the film. In addition, the 
precision of the films did not permit separation of traffic on the inner and outer 
circular taxiways, except in a few cases. 

Table 2-3 illustrates the events for which times of occurrence were 
recorded for arrival and departure aircraft. It should be noted that it was not 
possible to obtain data on the movements of aircraft between the terminal ramp 

Table 2-3. Movement Events Measured for ASDE Film Analysis 



Arrivals 


Departures 


OL 


- Over Last Light 


LR 


- Leave Ramp Area 


TO 

HI/SI; 

H2/S2 


- Turn Off Runway 

- "Holds" 


HI/SI; 
H2/S2 

EDQ/LDQ 


- "Holds" 

- Enter/Leave "Dept. Q" 


HP/SP 


- Enter/Leave Penalty Box 


RTR 


- Ready to Roll 


ER 


- Enter Ramp Area* 


STO 


- Start Takeoff 



2-33 



areas and the hangar/cargo areas. * The times recorded were used to compute 
the taxi service time and hold delay time for each aircraft. 

As noted in Table 2-3 the beginning and end of each "Hold" was deter- 
mined for each aircraft. These "Holds" included a "Penalty Box Hold" for some 
arrival aircraft. This delay is attributable to gate unavailability rather than sur- 
face traffic congestion and a method for identification and subtraction of this type 
of "Hold" time from the total delay was developed. The guidelines used for iden- 
tification of Penalty Box Holds include location of "Hold" area associated with the 
following guidelines : 

• Aircraft stops within known areas for holding of aircraft 

• An arrival aircraft may occupy a holding area only once 

• All "Holds" whose duration was in excess of 90 seconds were 
assumed to be of gate nature unless the ASDE films permitted 
assessment of another reason for the hold. 

A copy of the form used for the reduction of the ASDE films is shown 
in Appendix B. 

From the times computed for each aircraft observed in an analysis 
period, average taxi service times and delay times were derived for the analysis 
period. These values were then used to compute and/or plot the average times 
for various traffic levels for the two different modes of operation for the airport: 
arrivals from the east or west. 

In addition, the measured data was employed to compute a value for 
the average number of aircraft under control in the Ground Controllers' and Local 
Controllers' areas using the relationship 



* These aircraft are handled by the Arrival Ground Controller; the level of this 
ground movement activity appears to be less than 10 percent of the aircraft 
actually measured and may be determined from the analysis of the communica- 
tion tape records for the above controller position. 



2-34 



Q = £- 

^ 1+ AT 

T. 



where 



Q = Average aircraft density or number of aircraft under control 
N = Total number of aircraft controlled during analysis period 
AT = Duration of the analysis period (normally one hour) 



T.= Average time under control for individual aircraft 



2. 4. 2. 2. 2 Ground Taxi Hold Analysis 

Following the derivation of the data for the aircraft flow statistics, the 
ASDE films were then subjected to further detailed analysis of the holds recorded 
(with the exception of "Penalty Box Holds"). The purpose of this analysis was to 
determine whether particular patterns relative to the locations at which aircraft 
holds are likely to occur could be discerned from the films to corroborate infor- 
mation developed in discussions with ATCT personnel. 

To accomplish this a map of the airport surface configuration was 
utilized. Each surface intersection was given an identification number according 
to an assignment scheme which distinguished between intersections on the inner/ 
outer circular taxiways, other taxiway/taxiway intersections, and taxiway/ runway 
intersections. The circumstances associated with each hold (i. e. , its location and 
the movements of other traffic relative to the holding aircraft) were studied and 
the location and (judged) probable cause or reason recorded, where it could be 
ascertained. The reason categories used included: (1) competing traffic; (2) run- 
way crossing; (3) ramp congestion; (4) unknown; and (5) other. 



2-35 



The recorded data was compiled for each analysis period, and for each 
mode of airport operation. The results were analyzed to determine whether a 
particular pattern could be observed for each of the two modes of operation and 
combined operations. 

2. 4. 2. 2. 3 Potentially Hazardous Incident Analysis 

During the first step in the ASDE film analysis, the reducing analysts 
noted a number of incidents which could have represented potentially hazardous 
situations. As in the case of the hold analysis, the circumstances of the situations 
were studied in further detail. However, in this case, the review of aircraft 
movements on the ASDE film was supplemented by review of the communications 
recordings for the control positions involved. In most instances these situations 
occurred between arrival and departure aircraft, although a number involved taxi- 
ing aircraft. 

2. 4. 2. 3 Ramp Area Observations 

It was determined that the only feasible way of collecting accurate data 
on aircraft movements within the terminal building ramp areas was by direct ob- 
servation and recording of events of interest. In comparison with other data col- 
lection methods (e. g. , ASDE photographic recording) the manual recording of 
ramp area activities presents certain constraints which should be recognized. 
First, the observer location dictates physical limits in the size of the area which 
can be viewed and accurate data collected. 

Prior to the start of the data collection efforts, a data recording form 
was developed to facilitate the data collection process. A sample of this form is 
shown in Appendix B. The form provided for recording of the operating airline, 
aircraft type, gate number, the time of occurrence of various events in the move- 
ments of arrival and departure aircraft in the gate area (e.g. , pushback, start to 
taxi, begin hold) and the apparent reason for any delays. In testing the data col- 
lection method it became apparent that it was not practical to readily identify the 



2-36 



time at which a jetway was removed. Consequently, this item was omitted from 
further consideration. The use of 35 mm camera recording techniques was also 
investigated. However, due to the relatively restricted viewing area of a camera 
(even with a wide-angle lens) from feasible observation points on the airport, it 
was concluded that no significant advantage would result by this means. 

Second, depending on the location of the observation point, the rapid 
identification of the specific gate at which an activity commences can at times be 
difficult due to obstructions (other aircraft blocking the view, for example) or due 
to the considerable distances and viewing angles involved. 

Finally, when multiple aircraft are in various stages of arrival or de- 
parture simultaneously, the problems associated with noting a particular event 
and the time of the event and immediately recording this data for the correct air- 
craft became rather difficult in a short period of time. 

The optimum method for dealing with these constraints during the ob- 
servation period consisted of combinations of (1) limiting the area under observa- 
tion, (2) proper location of the observation point, and (3) by working as a team 
with one observer noting the occurrence and time of an event and a second ob- 
server recording the data in the appropriate space on the data sheet. 

2. 4. 2. 3. 1 Data Collection 

Observations of aircraft movements were made from three different 
locations which permitted coverage of the individual ramp areas. United Airlines 
operates a ramp tower located on top of the intersection of the E and F concourses. 
From this location an unobstructed view is available for the ramp areas between 
the D-E, E-F, and F-G concourses. The second location was at the ramp tower 
located on top of the intersection of the H and K concourses. This tower is oper- 
ated by American Airlines for control of their assigned gates. Due to the physical 
location of various offices within the ramp tower area (facing the H concourse), 
the view is restricted to the H-K and K ramp areas and the two AAL gates (H-l 



2-37 



and H-2) located on the inner edge of the H concourse. The third location selected 
for observation of the G-H ramp area was located within the main terminal approx- 
imately midway between the G and H concourses. In the case of observations of 
the G-H ramp area, it was absolutely essential to use the team approach for date 
collection as a result of an additional factor not mentioned above. This was due 
to the relative illumination levels of the area under observation and within the 
terminal building during the early morning and early evening hours which made 
observations much more difficult than those from the ramp control towers. 

For arriving aircraft, the time of entry into the ramp area was re- 
corded when the aircraft physically passed the outer edge of a particular con- 
course. In the event of an arrival hold, the times at which the aircraft stopped 
taxiing and began taxiing again were recorded. The docking time was recorded 
as that time when the aircraft came to a halt at the gate. Aircraft type, airline, 
and gate number were also recorded at that time. 

For departing aircraft, aircraft type, airline, and gate number were 
recorded while the aircraft was still at the gate. Timing measurements began 
when the aircraft first began pushing back from the gate. Pushback was consid- 
ered to be complete when the tow bar was physically removed from the aircraft 
and the time was then recorded. The time at which the aircraft began to taxi was 
recorded. In the event of a departure hold at any point in movements (e. g. , dur- 
ing pushback or after taxi was begun) the times at which the movement stopped and 
was reinitiated were recorded. The time of exit from the ramp area was recorded 
when the aircraft physically passed the outer edge of a particular concourse. 

In the event of a movement hold for either arrival or departure, the 
apparent reason for the hold was recorded (if possible to ascertain). 

2. 4. 2. 3. 2 Data Analysis 

For arrival aircraft two movement characteristics were computed: 
Ramp Service Time and Arrival Hold Duration. Ramp Service Time for "Arrivals" 



2-38 



was defined as the duration of the time interval between time of entry and docking, 
including holds, if any. Arrival Hold Duration consisted of the total of all holds 
in the ramp area while the aircraft was entering. 

Ramp Service Time and Hold Duration were computed for departure 
aircraft as well. In addition, two other movement characteristics, Pushback Dur- 
ation and Engine Start Time, were computed. Pushback Duration was defined as 
the time difference between the start of pushback and removal of the tow bar. 
Engine Start Time was defined as the time interval between completion of push- 
back and the start of departure taxi. Departure Hold Durations included all peri- 
ods during which the aircraft is stopped after the initial taxi operation began. 
Ramp Service Time, for departures, was defined as the total time interval between 
the start of pushback and the time the aircraft passed the outer edge of the finger. 

For those aircraft which arrived and departed within the specific ob- 
servation period, a "Gate Occupancy Time" was derived to provide data on the 
length of time the aircraft physically occupied the gate. This interval was deter- 
mined from the time of docking to the time that pushback commenced. 

The resulting data was used to develop statistical distributions of these 
various movement characteristics. In addition, an analysis of the data was made 
to determine the primary causative factors for aircraft delays within the gate area. 
An analysis was made to determine the average ramp density (number of aircraft 
in the area per minute) and the short-term effect of scheduling peaks on aircraft 
movements in the ramp area. 

2. 4. 3 Airline Operations Analysis 

The airline operations analysis was designed to examine those aspects 
of aircraft operator procedures that impact on the total operations at O'Hare and 
the operations of the ASTC System. The aspects of airline operations of interest 
include planning of aircraft schedules and gate assignment, control of gate 



2-39 



operations, and aircraft flight crew operations. To study these aspects the air- 
line operations analysis was divided into two distinct but related areas: 

1. Interviews with airline terminal operations management personnel 
and observation of operational activities 

2. Interviews with pilot personnel and in-flight observation of flight 
crew activities 

2. 4. 3. 1 Gate/Planning Control Interviews and Observations 

The specific objective of the interviews with airlines terminal opera- 
tions personnel was to obtain information related to: 

1. The manner in which flight schedule and gate assignment plans 
are developed. 

2. The criteria employed in developing the gate assignment plan and 
making adjustments to that plan when gate delays are experienced. 

3. The procedures employed in coordinating aircraft departure from 
and arrival at the gates. 

The primary method of obtaining this information was interviews with 
personnel from three major airlines operating at O'Hare: American Airlines, 
TransWorld Airlines, and United Airlines. These airlines were selected because 
they were major operators at O'Hare, constituting more than 50 percent of all 
traffic; hence they could provide the most information on gate planning and control, 
they operated a variety of aircraft, and they were most subject to gate delay prob- 
lems. The three airlines were contacted and arrangements for the interviews 
made. The principals interviewed for each of the airlines were: 

American Airlines - Mr. Jack Woods 

TransWorld Airlines - Mr. Peter Constantino 

United Airlines - Mr. Michael Jankovich 

A structured questionnaire was developed for use in these interviews. 
It incorporated a number of questions in each of the objective areas identified 



2-40 



above and provided for recording of the responses directly on the form. In addi- 
tion, the opportunity was taken to incorporate a number of questions soliciting the 
opinions of the interviewees on potential concepts for coordination of airline gate 
planning/control functions with traffic control functions in future ASTC systems. 
A copy of the questionnaire employed is included in Appendix C. 

These interviews were supplemented by observations in the airlines' 
planning and control facilities to gain a first-hand impression of these operations. 

The results of the activities were utilized to develop the functional 
description of the duties and responsibilities of airline personnel provided in para- 
graph 4. 3. 

2. 4. 3. 2 Pilot Interviews and Cockpit Observations 

The specific objective of the interviews with pilot personnel was to ob- 
tain information related to: 

1. The division of functional responsibilities between the members 
of the flight deck (cockpit) crew. 

2. The procedures followed in communications with the ATCT and 
airlines operations. 

3. The procedures followed in controlling the movements of aircraft 
within all phases of the flight. 

4. Attitudes toward the existing ASTC System at O'Hare including 
both control by the ATCT and visual ground aids. 

Arrangements were made with American, TransWorld and United Air- 
lines for access to a number of pilots, including both management and line pilots. 
In addition, with the assistance of two of these pilots, contact was established 
with two general aviation pilots who agreed to provide an interview. The pilots 
who participated in this activity include: 

1. Robert Smith, Mgmt Pilot, AAL 

2. John Hub. Line Pilot. AAL 



2-41 



3. John Rhodes, Mgmt Pilot, TWA 

4. Curtis E. Rogers, Mgmt Pilot, TWA 

5. H. A. Jacobsen, Mgmt Pilot, TWA 

6. Bernard Sterner, Mgmt Pilot, UAL 

7. Richard Schultz, Line Pilot, UAL 

8. Raoul Castro, General Aviation Pilot (Corp) 

9. Robert E. Riddle, General Aviation Pilot (Corp) 

The structured questionnaire developed for use in these interviews was 
divided into two parts. The first which was completed by the pilots was a summary 
of his flight experience. In the second part of the interview the pilots were first 
asked to provide a narrative scenario of the functions performed by each flight of- 
ficer during departure and arrival. This was followed by detailed questions and 
answers covering specific aspects of interest of crew activities not previously 
covered by the interviewee as well as pilot attitudes toward current ASTC System 
operations. In addition, the opportunity was taken to incorporate a number of 
questions to solicit pilot opinions pertaining to potential concepts for improved 
visual ground guidance and transmission of clearances and control instructions to 
aircraft in future ASTC systems. To assist in this latter area of the interview, 
illustrations of potential methods of providing this information to the cockpit crew 
were prepared as references for the questions asked. A copy of the questionnaire 
employed is presented in Appendix C. 

These interviews were supplemented by in-cockpit observations by 
project staff members. Arrangements for Flight Deck Authority for two staff 
members were made with the assistance of United Air Lines for flights between 
O'Hare and Newark Airports. Depending on the availability of one or two observer 
seats in the cockpit for the flights flown, one or both of these staff members were 
in place in the cockpit to observe operations during departure and arrival phases 
of flight. Departure phase observations were made from the point at which the 
crew boarded the aircraft until the aircraft reached its enroute altitude. Arrival 



2-42 



phase observations were made from the point at which descent was initiated until 
the completion of flight check procedures following the docking of the aircraft. 
The equipments flown during these flights included DC-10, DC-8, and DC-8-60 
series aircraft. 

During the flights recordings were taped of the observers' impressions 
of the activities of the flight crew and the situations encountered. In a few flights, 
detailed records were made tracing the movements of the aircraft, the activities 
of the crew, and communications with ATC and airline operations in time sequence. 

The results of the activities serve as the basis for the functional de- 
scriptions of flight crew responsibilities in Section 4. 3 and the flight crew work- 
load analysis in Section 5. 4. 

2. 4. 4 Airport Management Operations Analysis 

The airport management operations analysis was designed to examine 
those aspects of the procedures followed by the O'Hare Airport management which 
impact on the total operations of O'Hare and the operations of the ASTC System. 
The aspects of airport management operations of interest included planning and 
coordination of airport maintenance operations, planning and coordination of snow 
removal operations, and coordination of emergency operations. This included 
coordination of these operations within the airport management organization and 
with the ATCT. 

The information in these areas was derived through interviews with 
airport management personnel and through review of the O'Hare Operations Man- 
ual and Emergency Operations Manual provided by the Assistant Airport Manager. 

A structured questionnaire was developed for use in the interviews. 
It incorporated questions covering each of the above areas of interest as well as 
the functional organization of the airport management. The opportunity was also 
taken to incorporate a number of questions to solicit the opinions of the interview- 
ees on potential concepts for the interface between airport management and ATCT 
operations in future ASTC systems. 



2-43 



2. 5 PROJECTION OF THE FUTURE OPERATING ENVIRONMENT AT 

O'HARE AIRPORT 

An attempt was made to obtain detailed information pertaining to pro- 
jections of the future operating environments of O'Hare Airport through 1985 for 
use in the future ASTC System effectiveness analysis. The information desired 
fell into the general categories of: 

1. Runway construction 

2. Taxiway construction 

3. Terminal facilities construction 

4. Traffic volumes 

5. Aircraft fleet 

It was not possible to obtain the desired information. Therefore, it 
became necessary to formulate a projected environment based upon certain reason- 
able assumptions. 

Assumptions relative to future construction of runway, taxiway and 
terminal facilities were based upon discussions with ATCT, airline, and airport 
management personnel. In meetings with these personnel, various possible 
changes to the airport facilities which have been considered were discussed and 
those most probable of implementation noted. Therefore, for the purposes of the 
future ASTC system analysis the projected environment was assumed to include: 

1. Construction of a new 9L-27R runway parallel to and north of the 
existing runway and use of the existing runway as a parallel taxi- 
way 

2. Construction of a new 4L-22R runway parallel to and northwest of 
the existing runway and use of the existing runway as a parallel 
taxiway 

3. Construction of a new section of taxiway connecting the 14R-32L 
parallel taxiway to the 4L end of the existing 4L-22R runway or 
future parallel taxiway 



2-44 



4. Construction of a new International Terminal Complex on the cur- 
rent site of the USAF/Air National Guard terminal facility. 

Another possible change in the airport facilities mentioned in discus- 
sions — the elimination of inner gates of the various terminal concourses and con- 
struction of underground facilities for passenger access to the remaining concourse 
areas — was rejected as being unreasonable for the foreseeable future. This is based 
upon the fact that gates represent revenue-producing elements for the airlines and 
airport and their elimination, particularly in view of revenue losses caused by the 
recent flight schedule cutback and increasing operating costs, would appear un- 
likely. In addition, prior to the cutback, operations at O'Hare were to some ex- 
tent gate limited, i. e. , gate delay holds were frequently encountered by arrival 
aircraft during heavy traffic periods. Thus, if traffic volume increases of any 
significance are to be considered for future O'Hare operations, reduction in the 
current gate capacity would be counter-productive. In fact, in 1970-71 extension 
of the existing concourses to provide increased gate capacity was under consider- 
ation by the airport management. 



2-45 



SECTION 3 - AIRPORT CONFIGURATION DESCRIPTION 

3.1 GENERAL 

The purpose of this section is to provide a functional description of the 
physical configuration of O'Hare Airport as it affects traffic operations and flow. 
It is also intended to serve as a background reference for the functional desciption 
of the ASTC System operation in Section 4. The material in this section is di- 
vided into descriptions of the various runway configurations and usage patterns, 
taxi flow patterns in relation to runway configuration in use, and the terminal facil- 
ities configuration. 

3.2 RUNWAY CONFIGURATION DESCRIPTION 

3.2.1 Runway Descriptions 

Figure 3-1 presents a plan view of O'Hare Airport. The north side of 
the field has four runway pavements; however, runway 18/36 is restricted to light 
aircraft departures. While the south side of the airport has the same number of 
major runway pavements (three) as the north side, the runway intersection ratios 
are appreciably different in the south than in the north. Each runway pavement, 
of course, can be used in two directions so that six major runways are available 
in each of the north and south areas. Runway identification is based upon the mag- 
netic heading of the runway (to the nearest 10 degrees) with suffix "L" or "R" to 
distinguish between the "parallels" as viewed from the aircraft. 

From 0800 to 2000, it is common for four primary runways to be in 
operation — an arrival /departure pair on the north side and one on the south side 
of the airport. From the layout of the runways shown in Figure 3-1, it is seen 
that most of the possible arrival /departure runway pairs involve intersecting run- 
ways. As will be shown in paragraph 5. 3. 3. 1. 3, the capacity of intersecting run- 
ways is determined by the ability of the controller to manage departure releases 
in the face of the incoming arrivals. Briefly, if the arrivals routinely cross the 



3-1 




Figure 3-1. O'Hare International Airport 



3-2 



departure runway prior to turnoff, then departure releases are keyed directly to 
the arrivals. The difficulty of the task depends on both how quickly the arrivals 
cross the intersection after touchdown and how quickly the departures clear the 
intersection after release. The farther down the runways the intersection occurs, 
the greater the dispersion on roll times to the critical intersection and the lower 
the capacity. On the other hand, if the arrivals routinely turn off prior to crossing 
the departure runway, then departure releases may be handled relatively indepen- 
dently of the arrival traffic. This results in a sharply increased capacity over the 
configuration in which both arrivals and departures have long rolls to the critical 
intersection. Because of the importance of configuration on the operation and 
capacity of intersecting runways, these runway combinations have been divided into 
four classes for the purposes of this working paper. These classes are presented 
in Table 3-1. 

Table 3-1. Classification of Crossing Runway Configurations 



Crossing Run- 








way Configu- 




Departing Aircraft 


Examples 


ration Classi- 


Arriving Aircraft Will 


Will Cross 


(Arrival/De- 


fication 


Cross Departure Runway 


Arrival Runway 


parture Runway) 


Near-Near 


While still in air or within 


Within 2000 ft from 


• 27R/32R 




2000 ft from start of touch- 


roll initiation 


• 9L/4L 




down zone 






Near-Far 


Same as above 


Roll to intersection 
> 2000 ft 


• 32L/27L 


Far-Far 


Intersection beyond 2000 ft 
from start of intersection 
and arrivals routinely 
cross departure runway 
prior to turn off 


Same as above 


• 14L/4L 


Quasi- 


Arrivals routinely turn off 


Not constrained 


• 14R/27L 


Independent 


prior to intersection but a 
missed approach initiated 
just prior to touchdown 
may pass over the depar- 
ture runway 




• 14R/9R 



3-3 



Landing Aids 

The following source data was used to identify the landing aids of 
O'Hare: 

1. Composite Utility Drawings (Revised July 1973) 

2. Pavement and Taxiway Lips (Effective Nov. 18, 1972) 
3 FAA Map (No date shown) 

4. FAA Airport Master Record (Date of print 5/24/73) 

Due to differing dates of the information sources shown, a number of 
possible conflicts/inconsistencies were noted and attempts made to resolve them. 
Although Source 3 is not dated, it does appear to be the most recent source in 
terms of ILS component location as well as actual runway taxiway configurations. 

Table 3-2 provides a summary of both electronic as well as visual 
landing aids deployed for the various runways. For the purpose of this table, the 
Cat I ILS components consist of (1) Middle Marker, (2) Glide Slope, and (3) Local- 
izer. The Cat II components are the same as for Cat I with the addition of an 
Inner Marker. 

Based on the above components, substantial agreement between the 
various sources was noted; however, the following items could not be located on 
Source 1, an omission considered to be due to lack of complete updating: 

Runway Missing ILS Component 



9R 


Glide Slope 


27L 


Middle Marker 


14R 


Inner Marker 


32 L 


Middle Marker 


14L 


Inner Marker 


32R 


Localizer 


4L 


Localizer 



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Visual landing aids were found to be in general agreement between 
Sources 3 and 4 with a single exception. For runway 4L, Source 3 indicates 
ALS/SFL while Source 4 indicates SALSF. In addition, it has been assumed that 
the acronym ALS/SFL used in Source 2 is identical to ALSAF used in Source 4 
and may be due to changes in the manner of usage. 

RVR instrumentation, as obtained from Source 3, is available as shown 
in the table. The only disagreement noted from Source 4 involves a single instal- 
lation which serves runways 9L and 4L with an RW. 

3.2.2 Runway Configuration Usage 

Identification of the usage patterns for the O'Hare runway configuration 
was based on five sources of data:* 



1. 



Maps illustrating the primary runway usage/taxi flow configura- 
tions and runway operations counts for CY 1971. * 



2. Discussions with O'Hare ATCT personnel. 

3. Review of runway configurations observed on TSC and CSC ASDE 
films. 

4. Review of ATCT summary Daily Work Sheet for a sample of days 
over a six month period, January to June 1973. 

5. Chicago O'Hare Airport Air Traffic Control Tower Training 
Manual, Dept. of Transportation/ Federal Aviation Administration, 
December 1973. 



*The maps illustrating runway configurations provided in item 2 were estimated to 
be at least two years old and did not include any reference to runway 4R/22L 
which was not completed until late in 1971. Therefore, the effort under item 2 
was essentially intended to determine recent configurations data. 



3-6 



3.2.2.1 Runway Configurations 

The discussions with the ATCT resulted in the identification of eleven 
primary runway configurations for O'Hare operations. This does not in any way 
reflect all the possible configurations that could be employed where the situations 
dictate, e.g., the closing of a runway requiring the use of a different configuration. 
Even within the eleven configurations a number of variations were identified, which 
basically involved the substitution of one runway for another for departures with- 
out changing the basic ground traffic flow pattern. 

The configurations identified are presented in Table 3-3. It may be 
noted that, for each configuration, Table 3-3 also provides a classification of the 
basic mode of operation for the airport, the classification of the runway opera- 
tions made, and the particular conditions under which this configuration may be 
employed. 

In discussing the development of the study analysis approach in Section 2 
it was indicated that two modes of operation of the airport seemed apparent, i.e., 
Arrivals from the East and Arrivals from the West. This assumption apoears to 
be borne out by the runway configurations shown in Table 3-3. In configurations 
1 to 4 the approaches to the arrival runways indicated are essentially made from 
east to west, with departures also from east to west. In configurations 5 to 10 
the approaches to the arrival runways (and departures) are essentially west to 
east. Configuration 11 has been classified as a mixed mode of airport operation 
since it incorporates arrivals and departures from both east to west and west to 
east. The significance for this configuration could not be ascertained by CSC. 

The decision to classify the mode of airport operations in terms of 
arrival direction was further borne out in discussions with ATCT personnel rel- 
ative to the manner in which the runway configuration to be used is chosen. It was 
indicated that the arrival runways were essentially chosen first based upon par- 
ticular selection criteria and then the departure runways compatible with the 
arrival runway operations and local noise abatement requirements. 



3-7 



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Runway 

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3-8 



In determining the runway configuration to be employed, the weather 
and wind conditions are the primary selection criteria. This gives rise to the 
runway operations mode classifications shown in Table 3-3. When weather con- 
ditions are above 800 feet ceiling and 2 miles visibility and wind velocity is low, 
i.e. , below 15 knots, the runways are operated in a "Dual" Approach Mode. In 
this mode headings for approaches to the arrival runways in the south or north 
areas are skewed with respect to one another as are departure runway headings. 
When weather conditions are below 800/2 and/or wind velocities are above 15 knots, 
the runways are operated in a Parallel Approach Mode; that is, approaches are 
made to parallel runways. It may be noted in Table 3-3 that several of the parallel 
approach mode operations also involve parallel departure runways. 

It is also shown in Table 3-3 that, under VFR conditions — that is, ceil- 
ing and visibility above 3500 feet and 5 miles — visual approaches may be made to 
other than the primary northside runway subject to the restriction indicated. 

3. 2. 2. 2 Limitations on Runway Usage 

It should be noted that although arrivals to runways 4L/4R are shown 
in Table 3-3 for configuration 10, this configuration is avoided except when the 
winds are strong out of the northeast. This is because use of 4L causes a loss of 
service for 14R, the prime runway for the west mode of operation. In addition, 
approaches to 4R pass low over the railroad yards south of the airport and inter- 
fere with switching operations which are conducted by voice communications. For 
this same reason the use of configuration 4 involving 22L departures is avoided 
unless 32 L is unavailable to allow use of configuration 1. 

It was noted that configuration 9 was used if runway 9L was not avail- 
able. Although the use of 4L for departures would eliminate the crossing of an 
active departure runway for arrivals on 14L to reach the terminal, such depar- 
tures take flights over a densely populated area immediately after takeoff (result- 
ing in noise complaints by residents). 



3-9 



Configuration 8, involving parallel 9L/9R arrivals, was noted to be used 
when winds are strong out of the east. However, this usage is different from other 
parallel operations which are employed when the ceiling and visibility are below 
800 feet and 2 miles. For this configuration clear visual operating conditions are 
required because the approach lighting system available for 9R does not permit 
operations under lowered visual conditions. 

It was noted for configuration 7, involving the use of only 14R/14L for 
both departure and arrival operations, that its use was limited to Category II con- 
ditions. As previously indicated in paragraph 3. 2. 1, these are the only runways 
instrumented for Category II operations. This subject of instrumentation leads to 
another limitation on runway configuration usage. By virtue of the nature of the 
instrumentation for the runways, primarily RVR and RVV, there are minimums 
below which they may not be employed. These minimums are summarized in 
Table 3-4. The values shown are taken from the Tower Training Manual for 
O'Hare. Discussions with ATCT personnel and observations indicated that low 
visibility operations below Cat I conditions are not conducted on other than the 14s. 
During an observation period when conditions changed from low Cat I (300 ft ceiling 
and 1/2 to 1 mile variable visibility) to Cat n, all arrival operations and departures 
waiting at 9L were routed to 14 L. 



3-10 



Table 3-4. Runway Usage Minimums Under Low Visibility Conditions 



Runway 


Arrival* 
Minimum 


Departure Minimum* 


4L 


400'-3/4 


RVV = 1/4 mile 


4R 


500'-l 


Prevailing visibility - 1/4 mile 


9L 


- 


RVV = 1/4 mile 


9R 


200'-l/2 


Prevailing visibility - 1/4 mile 


14L 


1200' RVR 


700' Touchdown RVR 
600' Rollout RVR 


14R 


1200' RVR 


1200' Touchdown RVR 
1000' Rollout RVR 


22L 


- 


Prevailing visibility - 1/4 mile 


22R 


400'-l 


Prevailing visibility - 1/4 mile 


27L 


200'-l/2 


Prevailing visibility - 1/4 mile 


27R 


2400' RVR 


1600' Touchdown RVR 


32L 


2400' RVR 


1200' Touchdown RVR 
1000' Rollout RVR 


32R 


2400' RVR 


700' Touchdown RVR 
600' Rollout RVR 



*According to O'Hare Tower Training Manual, 
December 1973. 



3-11 



From this table it may be noted that, in the case of runways 14R/14L, 
arrival minimums are identical but the departure minimums for 14L are lower. 
As noted during the observations referenced above, this differential resulted in 
the routing of traffic waiting for departure on 14R to 14L when severe fog caused 
the visibility conditions to go below the 14R minimums. 

3. 2. 2. 3 Runway Usage Records 

Runway utilization records for 1971 provided by the ATCT are sum- 
marized in Table 3-5. The runway operations counts provided are shown in part 
(a) of the table. Part (b) represents a breakdown of the counts for these runways 
in terms of the two airport operating modes. 

The above data did not provide any means for determining the specific 
runway configurations for which these operations took place or of the effect of 
seasonal weather variations on runway configuration selected. However, it is 
expected that seasonal weather variations will influence both the mode of airport 
operation and the most popular runway configurations used at different times of 
the year. Both the TSC and CSC surveys were taken primarily in the months of 
January and February and therefore do not reflect operations at other times of the 
year. 

A short investigation was made of the runway configuration data kept 
on a daily basis by O'Hare. The following guidelines were used: 

• Weekdays only; 12 hour period between 0800 and 2000 

• Special situations (snow removal, etc.) eliminated. 

• Configurations used for 30 minutes or less are excluded from data. 

Four time periods in 1973 were selected, with eight sample days in 
each period, from records readily available from which the desired data could 
be obtained. These periods are as follows: 



3-12 



Table 3-5. O'Hare Runway Utilization CY-71 



Runway 


Departures 


Arrivals 


14R 


17,663 


73,423 


14L 


11,527 


44,739 


32R 


58,668 


9,985 


32L 


17,564 


71,131 


4R 


4 




4L 


6,892 


555 


22R 


1,177 


37,181 


22L 


639 


255 


27R 


3,095 


55,916 


27L 


121,964 


14,585 


9R 


24,573 


10,487 


9L 


47,794 


2,119 


18 




85 


36 


4,561 




Totals 


316,124 


320,460 



Helicopters — 4,857 

a) Aircraft Count 





Sout 


l Area 


North Area 


Arrival from 
West Runways 


14R 




9R 


4R 




14L 




9L 




4L 




Arrival from 
East Runways 




32L 




27L 


22L 




32R 




27R 




22R 


% of Arrivals 


22.9 


22.2 


3.3 


4.6 


Probably 
opened only 

r>3T*t fitwonr 1 


14.0 


3.1 


.7 


17.4 


.2 


11.6 


% of De- 
partures 


5.6 


5.6 


7.8 


38.6 


3.6 


18.6 


15.1 


1.0 


2.2 


.4 


% of Total 


14.3 


13.9 


5.5 


21.4 






8.8 


10.8 


7.8 


9.3 


1.2 


6.0 



Estimated % arrivals from west = 40%; from east ~ 60% 



b) Percentage breakdown 



3-13 



Nominal Time Period Dates 

A - January Jan. 2,5,8,11,16,19,22,26 

B - February Jan. 30; Feb. 2,6,9,12, 28; March 2,5 

C - April Mar. 28; April 3,11,19,27,30; May 2,8 

D - June May 14,24,29; June 1,7,12,20,25 

The various runway configurations and the time interval of usage for a 
particular configuration were determined for the 96-hour sample comprising each 
time period. The data derived from this analysis are presented in Tables 3-6 and 
3-7. Each runway configuration is identified by the primary arrival runway followed 
by the primary departure runway. The entries in each matrix element represent 
the continuous number of hours the particular configuration was observed before a 
change occurred. From this data we have also determined the "life", or duration, 
of a runway configuration. 

The January and February data are combined in Table 3-6 and the 
April and June data are combined in Table 3-7. The top matrix in each table pre- 
sents the configuration defined as "Arrivals from the East" while the lower matrix 
presents the "Arrivals from West" mode (in the upper left set of entries enclosed 
by the solid line) plus other "mixed" configurations. In these mixed configura- 
tions the use of runway 22R in the north side appears to be appreciably more popular 
in winter months. Note that while the "Arrivals from East" mode was used 63 per- 
cent (1165 ■* 187. 25) of the time in January and February, the "Arrival from the 
West" mode (excluding the mixed configurations) was only used 10 percent 
(19 ■*■ 187. 25) of the time. These results may be contrasted with those of Table 3-7 
for April plus June where the east mode was used 46 percent, and the west mode 
42 percent of the time while mixed modes dropped to 12 percent usage. 

The "life" of a runway configuration was appreciably shorter in the 
winter months (4. 6 hours) as contrasted with the April/June results of 5. 8 hours, 
i. e. , there are more runway changes in winter months. Using these results, it 



3-14 



Table 3-6. Seasonal Runway Configuration Usage 
(January and February 1973) 



ARRIVALS FROM EAST 







SOUTH SIDE 












27L/22L 












OR 








32L/27L 


32L /32L 


27L/32L 


27L/27L 


TOTAL HRS 




JAN. 


FEB. 


JAN. 


FEB. 


JAN. 


FEB. 


JAN. 


FEB. 






3.5 


2.0 






-- 


1.25 


-- 


2.25 


93.75 






12.0 


1.5 




















12.0 


2.0 


















27R/32R 


12.0 

11.0 

3.5 


11.5 
12.0 
















NORTH SIDE 




7.25 






















1.25 


- 


5.5 










18.25 




32R/32R 


-- 


1.5 

3.75 

1.25 




5.0 












22R/27R 














-- 


2.25 
2.25 


4.50 


TOTAL HRS 


98 


10.5 


1.25 


6.75 


116.50 



ARRIVALS FROM WEST AND OTHER RUNWAY CONFIGURATIONS 







SOUTH SIDE 


TOTAL HRS 




9R /4R 


9R / 9R 


9R /14R 


14R/14R 

-9R 
14R / 9R 


14R /27L 

OR 
14R/22L 


9R /22L 




JAN. | FEB. 


JAN. | FEB. 


JAN. | FEB. 


JAN. I FEB. 


JAN. 


FEB. 


JAN. 


FEB. 


NORTH SIDE 


14L/4L 


.75 
6.0 

1.25 -- -- 6.0 
4.25 
1.75 
"ARRIVALS FROM WEST" MODE 










6.75 


14L/9L 


.75 


2.25 


"" 


2.25 


18.50 


14L/14L 


-- 


2.50 






2.50 


22R/14L 














3.0 


-- 


12.00 
1.75 


7.75 
2.75 






27.25 


22R/9L 


















8.50 
4.25 
1.25 


1.75 






15.75 


TOTAL HRS 


6.75 




1.25 


15.0 


45.50 


2.25 


70.75 



187.25 

Average Interval Between R/W Configuration change = Total Time-^ No. of observations = = 4.6 hours 

41 



3-15 



Table 3-7. Seasonal Runway Configuration Usage 
(April and June 1973) 



ARRIVALS FROM EAST 







SOUTH SIDE 


TOTAL HRS 




32L /27L 


32 L /32L 


27L/32L 


27L /22L 

OR 
27L/27L 




APR. 


JUN. 


APR. 


JUN. 


APR. 


JUN. 


APR. 


JUN. 


NORTH SIDE 


27R/32R 


6.50 
2.75 
6.50 


16.25 
12.00 










7.25 


2.50 


53.75 


32R/32R 






1.0 
3.0 


-- 










4.00 


32R/4L 


- 


9.25 














9.25 


22R/27R 














12.00 


6.75 


18.75 


TOTAL HRS 


53.25 


4.0 




28.50 


85.75 



ARRIVALS FROM WEST AND OTHER RUNWAY CONFIGURATIONS 





SOUTH SIDE 


TOTAL 
HRS 




9R /4R 


9R /9R 


9R /14R 


14R/14R 

-9R 
14R /9R 


14R /14R 


14R /27L 

OR 
14R/22L 


9R /22L 




APR. | JUN. 


APR. | JUN. 


APR. | JUN. 


APR. | JUN. 


APR. | JUN. 


APR. 


JUN. 


APR. 


JUN. 


NORTH 
SIDE 


14L/4L 


6.75 2.25 - 2.0 
2.25 7.25 
4.75 

2.25 -- 6.75 -- 3.25 3.0 
9.75 
5.25 
1.25 

500 5 - 75 "ARRIVALS FROM WEST" MODE 
6.00 4.50 










25;25 


14L/9L 


5.5 








37.00 


14L/14L 












9L/4L 










21.25 


22R/14L 






















.. 


5.25 






5.25 


22R/9L 






















-- 


10.00 






10.00 


TOTAL HRS 


44.50 


2.25 


6.75 


22.50 


2.0 


20.75 




98.75 



187.5 
Average Interval Between R/W Configuration change = Total Time-4- No. of observations = = 5.8 hours 



3-16 



appears that there are many days wherein three runway configuration changes occur 
during the time period 0800-2000. These "changeover periods" can pose special 
problems to both the controllers and pilots. 

Summation of all four time periods (a total of 32 days and about 370 
hours) indicates the following: 

1. The "Arrivals from East" mode occurs approximately 60 percent 
of the time over the six month period, which compares with the 
data provided in Table 3-5. 

2. In the "Arrival from East" mode there is one predominant runway 
configuration. The most popular configuration (used in 75 percent 
of samples for this mode) was 32L/27L in the south and 27R/32R 
on the north side. 

3. In the "Arrivals from West" mode, there is no similarly predomi- 
nant runway configuration. On the north side the following com- 
binations were used for the percent of hours listed: 

14L/4L - 19 percent 
14L/9L - 33 percent 

On the south side the results were: 

9R/4R - 30 percent 
14R/9R - 22 percent 

It would appear that in the north the 14L/9L combination is sig- 
nificantly more popular but there is no significantly popular 
combination in the south. 

4. In the Mixed mode of operation, the configuration of 22R/14L in 
the north and 14R/22L or 27 L in the south is the one most used. 
This agrees with the information provided by the ATCT in dis- 
cussions on runway configurations in which the combination of 
22R/14L and 14R/27L was identified as one of O'Hare's pri- 
mary configurations. 



3-17 



Runway Configuration Profile 

In summary, the operational runway configurations are characterized 
in Tables 3-8 and 3-9, for clear and calm weather operations and for unclear and/or 
windy weather operations respectively. These tables present the arrival runway 
configurations, the weather conditions under which the various arrival configura- 
tions are selected for operation, and the departure runway configurations used with 
each arrival configuration. The list of arrival and departure runway configurations 
was compiled from the O'Hare Control Tower Training Manual, from the Runway 
configuration Usage Survey presented in Tables 3-6 and 3-7, and from discussions 
with control tower personnel. Based on the runway configuration usage statistics, 
an estimate of the relative time in operation of the various arrival configurations 
is presented in Column 3; and an estimate of the relative usage of the departure 
configurations, associated with each arrival configuration, is presented in Column 9. 
Comparing these usage figures to the eleven primary configurations identified by 
ATCT personnel, Column 12, there is general agreement. 

The estimates indicate that the clear and calm weather configurations 
are operated approximately 65 percent of the time and, of this time, the airport 
operates in the arrival from the East, West, and Mixed Modes roughly 40 percent, 
10 percent, and 15 percent, respectively. The predominance of time spent in the 
East Arrival Mode will be shown in Section 5 to be due in large part to the smooth- 
ness of traffic flow both on the runways and in the taxiways. The six remaining ar- 
rival configurations are used in unclear and/or windy weather. The 14L/14R run- ays a 
ways are certified for Cat II operations and make up the dominant arrival configura- 
tion for closing weather situations in which Cat II conditions are possible as well as for 
the low visibility operations themselves. These six parallel arrival pairs permit op- 
erations directly into the wind for each 45 degrees of the compass with the exception 
of winds directly out of the North or South. These six configurations together operate 
approximately 35 percent of the time. Of this percentage, the arrival from the East 



3-18 



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3-20 



configurations operate 15 percent and the arrival from the West configurations 
operate 20 percent of the time — there is no Mixed Mode under these conditions. 
The West configurations dominate due to the inclusion of the low visibility arrival 
configuration — 14L/14R . 

The various runway configurations operated on the south and north 
sides of the airport are classified in Columns 10 and 11, respectively. There are 
five classes of runway configurations, Single runway and Near-Near, Near- Far, 
Far- Far, and Quasi-Independent crossing runways. Table 3-10 presents an estima- 
tion of the relative time each configuration is in operation on one of the two sides 
of the airport. This estimation is based on the statistics presented in Tables 3-6 
and 3-7. The table indicates that, in clear and calm weather, there is no prefer- 
ence between the crossing runway configurations; but in cloudy and/or windy con- 
ditions, the airport is primarily operated in the Quasi-Independent runway con- 
figuration, which is the safest crossing runway configuration since arrival aircraft 
do not routinely cross the departure runway before turning off. 



3-21 



Table 3-10. Relative Usage of Various Runway Configuration 
Classes at O'Hare 



Arrival Runway 
Configurations 


Arrival/Departure 

Runway Configurations 

Class (Table 3-1) 


Relative Usage 
of Classes (%) 


Clear and Calm 
Weather 


Near-Near 


36 


Near-Far 


36 


Far-Far 


31 


Quasi-Independent 


27 


Single 


7 


Unclear and/or 
Windy Weather 

I 


Near-Near 


10 


Near-Far 


4 


Far-Far 


4 


Quasi-Independent 


31 


Single 


14 



Note: Since two sets of runways operate at O'Hare, the 
total usage is 200%. 



3-22 



3. 3 TAXI FLOW PATTERNS 

The general flow of ground traffic at O'Hare is primarily related to 
the runways in use which determine the entry points into the taxiway network (i.e. , 
runway turnoffs) and the exit points (i. e. , departure queues). The orientation and 
primary use of runways is such that arrival aircraft generally land heading in the 
direction of the terminal while most departure queue locations are at the end of the 
runway nearest the terminal. Arrivals on 32R and departures on 14R, 14L, and 
4R are exceptions. 

The flow on the Inner and Outer circulars is directly related to the 
mode of runway operations. In the Arrivals from the East mode the Inner is clock- 
wise and the Outer counterclockwise. These flows are reversed in the Arrivals 
from the West mode of operations. For the most part, departure traffic flows on 
the Outer and arrival traffic on the Inner. One major exception is that heavy air- 
craft cannot use the Inner due to space limitations. 

The information presented here was acquired in discussions with ATCT 
personnel at O'Hare for the eleven runway configurations (including alternate de- 
parture runways for two configurations) considered the most commonly used pat- 
terns. Figures 3-2 to 3-5 depict the major flow patterns and alternates used in each 
configuration and a brief description of each is provided. The normal handoff areas 
used by Departure Ground Control are presented in Figure 3-2 along with the typical 
departure queue configurations used by Local Control for various departure runways. 

While the information included here represents the primary patterns, 
it is important to note that many other runway configurations are also used depend- 
ing on weather conditions, noise abatement procedures, airport conditions, and 
other factors. Of course, the surface traffic patterns will vary when these other 
configurations are in effect. Also, even in the major configurations presented, 
many other surface paths are possible in addition to those shown in the diagrams. 
The specific path for each individual aircraft is generally assigned according to 



3-23 



the specified flow patterns; however, depending on analysis of conditions, the con- 
trollers may, and often do, assign other paths in order to assure the most 
expeditious, orderly, safe flow of traffic. The surface traffic environment is an 
extremely dynamic one in which general flow patterns are constantly adjusted to 
changing conditions. 

In addition to the flow of aircraft between the runways and terminal 
area, there are secondary aircraft traffic flows between the hangar and terminal 
areas, between the cargo area and the runways, and between the USAF area and the 
runways. The routes commonly used by these secondary traffic flows are shown 
in Figure 3-3. Superimposed on the taxiway network are 26 miles of service roads. 
The sections of the road interconnecting the hangar, terminal, and cargo areas 
are heavily traveled and require the flow of trucks and cars to cross the taxiway 
network at numerous places. Some of these intersections are also heavily traveled 
by aircraft, creating potentially hazardous situations, particularly during low 
visibility operations. In addition to this main artery, the service road network 
also permits access to the USAF area and to the various equipment sites on the 
airport surface. The service road network is presented in Figure 3-4. 

3. 3. 1 Configuration 1 

3. 3. 1. 1 Runways 

In this configuration, shown in Figure 3-5, runways 27R and 32L are 
used for arrivals with some VFR/STOL flights on 22R. Departures are on 32R for 
flights to the north and east, and also for flights to the west (DBQ departure fix) 
when traffic to the west is heavy. Runway 27L is used for flights to the south, 
west, and southwest. Runway 36 is available for general aviation flights. 

3. 3. 1. 2 Arrivals 

Flights landing on 27R will generally turn off directly onto the Outer 
and go counterclockwise until reaching their ramps and then turn left across the 
Inner to the gate. Any flights landing on 22R will turn off at the Old Scenic onto 



3-24 




NOTES I. Runway^ 
22 R nev 

2. Handoff 

3. Depart u 



Figure 3-2. 



Location of Departure Queues 
and Ground Control Handoff 
Areas at O'Hare 

3-25/3-26 



the specified flow patterns; however, depending on analysis of conditions, the con- 
trollers may, and often do, assign other paths in order to assure the most 
expeditious, orderly, safe flow of traffic. The surface traffic environment is an 
extremely dynamic one in which general flow patterns are constantly adjusted to 
changing conditions. 

In addition to the flow of aircraft between the runways and terminal 
area, there are secondary aircraft traffic flows between the hangar and terminal 
areas, between the cargo area and the runways, and between the USAF area and the 
runways. The routes commonly used by these secondary traffic flows are shown 
in Figure 3-3. Superimposed on the taxiway network are 26 miles of service roads. 
The sections of the road interconnecting the hangar, terminal, and cargo areas 
are heavily traveled and require the flow of trucks and cars to cross the taxiway 
network at numerous places. Some of these intersections are also heavily traveled 
by aircraft, creating potentially hazardous situations, particularly during low 
visibility operations. In addition to this main artery, the service road network 
also permits access to the USAF area and to the various equipment sites on the 
airport surface. The service road network is presented in Figure 3-4. 

3. 3. 1 Configuration 1 

3. 3. 1. 1 Runways 

In this configuration, shown in Figure 3-5, runways 27R and 32L are 
used for arrivals with some VFR/STOL flights on 22R. Departures are on 32R for 
flights to the north and east, and also for flights to the west (DBQ departure fix) 
when traffic to the west is heavy. Runway 27L is used for flights to the south, 
west, and southwest. Runway 36 is available for general aviation flights. 

3. 3. 1. 2 Arrivals 

Flights landing on 27R will generally turn off directly onto the Outer 
and go counterclockwise until reaching their ramps and then turn left across the 
Inner to the gate. Any flights landing on 22R will turn off at the Old Scenic onto 



3-24 




NOTES I. Runways 4R and 22L very seldom used for Arrivals, 
22 R never a Departure Runwoy. 

2 Handoff Areas = (h) 

3. Departure Queue =1 



Figure 3-2. Location of Departure Queues 
and Ground Control Handoff 
Areas at O'Hare 



3-25/3-26 




Figure 3-3. 



Aircraft Routes at O'Hare 
Hangar, Cargo and Air 
Force Areas 



3-27/3-28 




NOTE: 

Aircraft flow for the Hangar, Cargo, and USAF Areas 
is completely dependent upon runway configurations. 
No aircraft were observed going directly from Hangars 



Figure 3-3. Aircraft Routes at O'Hare 
Hangar, Cargo and Air 
Force Areas 



3-27/3-28 




Figure 3-4. Main Service Vehicle Roads 
at O'Hare Airport 



3-29/3-30 




Service Vehicle Roads 



Figure 3-4. Main Service Vehicle Roads 
at O'Hare Airport 



3-29/3-30 




VFR 



Y>X?^ 



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V 



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N xx% Ngs 



LEGEND 

■■• ■• •■• Arrivals 

• •••••••■ Departures 

• ■• • mmmm Combined 

Fine lines represent alternate 
routes 



o> 




Figure 3-5. Configuration 1 



3-31 



the Outer and then proceed as above. From 32L arrival flights will turn off at T5 
or T5 reverse and take the northwest parallel down to T3 or Tl. Flights going to 
ramps A through E will cross to the Inner at T3 and proceed in a clockwise direc- 
tion to their ramps. Flights on the east side of ramp E will cross to the Outer at 
Tl and join the counterclockwise flow to their ramps. When the Outer is congested 
flights from 32L going to ramps east of ramp F may be sent down the 14R/32L 
parallel to the 9R/27L parallel and then east to the stub or north-south taxiways 
where they will turn in toward the terminal area. General aviation flights landing 
on 32L may use the bypass and New Scenic to their terminal as an alternate. 

3. 3. 1. 3 Departures 

Departure flights on 32R will go directly to the Outer upon leaving their 
ramp and proceed in a counterclockwise direction around the terminal area and 
over the Bridge. Flights leaving ramps west of the E concourse may be sent clock- 
wise on the Inner and the 9L/27R parallel. When there is a backup at the Bridge, 
this alternate will also be used for flights with in-trail restrictions at the Depar- 
ture Fix. General aviation flights for runway 36 will use the 9L/27R parallel. 
Flights for 27L will use the Outer and then the cargo taxiway. If in-trail restric- 
tions are in effect at the departure fix, the 9R/27L parallel will be used instead of 
the cargo taxiway. 

3. 3. 2 Configuration 2 

3. 3. 2. 1 Runways 

The arrival runways in this configuration, shown in Figure 3-6, are 32L 
and 32R. Runway 32R is also used for departures going to the north and east while 
27L is used for west, south, and southwest departures. General aviation flights 
may also use runway 36. 






3-32 



V. 




/rx v 



1 s v "x> V\ ^w 






X 



X 



v. 



s \\ X V %-\ 



LEGEND 

<■■«»•■■» Arrivals 
• •••«••• Departures 

«■» • «■■» Combined 
Fine lines represent alternate 



routes 






\\ V AV ( 



Jft^X 



\\ YJ?) \\ 

■*-">-' X/ \\ .// -' 




~-y<c- 



y / 



Figure 3-6. Configuration 2 



3-33 



3. 3. 2. 2 Arrivals 

Flights landing on 32L will follow the same basic path as in Configura- 
tion 1. However, the alternate routing along the 9R/27L parallel will not be used. 
Arrivals on 32R will turn off either at runway 22R or at the Scenic taxiway and 
travel southwest to the Old Scenic where they will turn on to the Outer and proceed 
in a counterclockwise direction to their ramps. 

3. 3. 2. 3 Departures 

Flights departing on 27L and 32R will follow the same basic paths and 
alternates as in Configuration 1. 

3. 3. 3 Configuration 3 

3. 3. 3. 1 Runways 

This configuration, shown in Figure 3-7, uses runways 27R and 27L 
for arrivals with some STOL flights on 22R. Departures to the west and south use 
32L while those to the north and east use 32R. 

3.3.3.2 Arrivals 

Flights landing on 27R or 22R will follow the same paths as in Config- 
uration 1. 

Flights landing on 27L will turn off and go toward the terminal area on 
either the north-south taxiway or the stub. They will turn onto the Outer if they 
must travel counterclockwise to their ramps or onto the Inner to go clockwise. 

3.3.3.3 Departures 

Flights departing on 32R will follow the same basic pattern and alter- 
nates as in Configurations 1 and 2. 

On runway 32L departures will generally begin takeoff at intersection 
Tl, rather than the end of the runway to avoid interference with arrivals on 27L. 
Aircraft at the west side of the terminal area will travel counterclockwise along 



3-34 



:3*r" 




VFR 



Figure 3-7. Configuration 3 



3-35 



the Outer to T3 and then turn onto the 14R/32L parallel and proceed down to Tl. 
Other flights will use the Inner in a clockwise direction to Tl and cross the Outer 
and the parallel at that point to get to the Tl intersection on the runway. When 
there is heavy congestion crossing to the runway at T3 or Tl, some aircraft may 
be routed via the New Scenic, the Bypass, and the 14L/32L parallel down to the Tl 
intersection. This alternate path is also used for flights with in-trail restrictions. 

3. 3. 4 Configuration 4 

3. 3. 4. 1 Runways 

In this configuration, shown in Figure 3-8, runways 22R and 27L are 
used for arrivals, runway 27R is used for departures to the north and east, and 
runway 22L is used for departures to the south and west. 

3. 3. 4. 2 Arrivals 

Flights arriving on 22R cross to the Outer at the Old Scenic and travel 
in a counterclockwise direction on the Outer to their ramps. Flights from 27L use 
the north-south taxiway and then either turn east on the Outer or west on the Inner 
depending on the location of their ramps. Another turnoff is the 14R/32L parallel 
to Tl and then the Inner or Outer as appropriate. 

3. 3. 4. 3 Departures 

Flights departing on 27R travel in a counterclockwise path around the 
terminal area, over the bridge and across the end of 32R to get to 27R. Flights to 
22L use the Outer and the cargo taxiway. As an alternate, flights with in-trail 
restrictions may be sent to 22L along the 9R/27L parallel rather than the cargo 
taxiway. 



3-36 




LEGEND 

tm mm aaau Arrivals 

Departures 
warn • «dbm» Combined 
Fine lines represent alternate 
routes 






Figure 3-8. Configuration 4 



3-37 



3. 3. 5 Configuration 5 

3. 3. 5. 1 Runways 

Runways 14L and 9R are used for arrivals in this configuration, shown 
in Figure 3-9. Departures to the north and east use 9L while departures to the 
west, south or southwest taxi to either 9R or 14R, whichever is in use. 

3. 3. 5. 2 Arrivals 

Flights arriving on 14L will turn off at and taxi down 22R to the Old 
Scenic, cross to the Inner and proceed in a counterclockwise direction to their 
ramps. They may also turn off at and taxi down 18 to the 9L/27R parallel and 
proceed west on parallel and on to the Inner. As an alternate, 747s leaving 14L 
at 18 will take the 14L/32R parallel down to the bridge and onto the Outer since 
they cannot travel on the Inner. Some American Airlines flights will also use this 
path. A third path is followed mainly by 747 flights that go to the end of 14L, over 
the bridge and onto the Outer in a clockwise direction. Aircraft landing on 9R will 
take the north-south taxiway and then either the Outer clockwise or the Inner coun- 
ter clockwise to the ramps. Some flights may turn off at the second high speed or 
the end of the runway and will travel west on the 9R/27L parallel to the north- 
south taxiway. 

3. 3. 5. 3 Departures 

Departures on 9L travel clockwise around the terminal area on the 
Outer and across the New Scenic. When traffic on Outer becomes backed up and 
arrivals are light or arrivals on 14L are not turning off on 22R, an alternate is to 
continue some traffic on the Outer to the Old Scenic, up to the 9L/27R parallel and 
west to the runway. 

Departures on 9R will travel clockwise on the Inner or counterclock- 
wise on the Outer to Tl and then follow Tl across 14R to the 9R/27L parallel. 
These flights also may cross at the stub to the 9R/27L parallel and travel west to 
the runway, crossing 14R. 



3-38 










m ^M 






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-7 Z" J 









v i 



LEGEND 
P9M»mb Arrivals 

Departures 
mm • «■■» Combined 
Fine lines represent alternate 
routes 



Figure 3-9. Configuration 5 



3-39 



When 14R is used for departures the path is via T3 to the 14R/32L 
parallel up to the end of the runway. 

3. 3. 6 Configuration 6 

3. 3. 6. 1 Runways 

Both 14L and 14R are used for arrivals in this configuration, shown in 
Figure 3-10, with 9L used for departures to the north and east and 9R for departures 
to the south and west 

3. 3. 6. 2 Arrivals 

Flights arriving on 14L will use the same basic pattern and alternatives 
as in Configuration 5. 

Arrivals on 14R will take the 14R/32L parallel down to T3 and across 
to the Inner (counterclockwise) or to the Outer (clockwise) to their ramps. 

3. 3. 6. 3 Departures 

Flights departing on 9L will use the Outer clockwise to the New Scenic. 
For 9R, Tl will be used across 14R and onto the 9R/27L parallel. As alternates, 
the stub or north-south taxiway may be used to get to the 9R/27L parallel when the 
outer is congested. 

3. 3. 7 Configuration 7 

3. 3. 7. 1 Runways 

In this configuration, shown on Figure 3-11, 14L and 14R are used for 
both arrivals and departures. Flights departing to the north and east use 14L and 
flights to the south and west use 14R. 






3-40 




LEGEND 
■»•»«■» Arrivals 

Departures 
warn • «m» Combined 
Fine lines represent alternate 



Figure 3-10. Configuration 6 



3-41 







x // 



X\V XX 

\X xx X 



XX x. 



x. x 



«mmmmm» Arrivals 
• ••••••• Departures 

«■* • mmm Combined 
Fine lines represent alternate 



routes 



XX 



'X. ^rvcx 



i 



~%: 



tc-xx )x» 



J3 



I> 



IS 



Figure 3-11. Configuration 7 



3-42 



3. 3. 7. 2 Arrivals 

Aircraft landing on 14L will turn off at either 22R or 18 and then take 
the 14L/32R parallel down to the bridge or go to the end of the runway and turn onto 
the bridge. From there, they proceed in a clockwise direction on the Outer to their 
ramps. 

Flights arriving on 14R turn off and take the 14R/32L parallel to T3 
and then go to the Inner (counterclockwise) or the Outer (clockwise) to their gates. 

3. 3. 7. 3 Departures 

All departures travel clockwise on the Outer and then take the New 
Scenic, the bypass and the 14R/32L parallel to the end of 14L, or the Old Scenic, 
the Scenic and the 14L/32R parallel to the end of 14R. 

3. 3. 8 Configuration 8 

3. 3. 8. 1 Runways 

In this configuration, shown in Figure 3-12, runways 9L and 9R are used 
for arrivals with 4L for departures to the north and east, and 4R for departures to 
the west and south. 

3. 3. 8. 2 Arrivals 

Flights landing on 9 L will turn off at runway 18 and take the 9L/27R 
parallel to the 14L/32R parallel or turn off directly onto the 14L/32R parallel. In 
both cases they go via the bridge to the Outer and proceed clockwise around the 
terminal area to their ramps. 

Arrivals on 9R turn off and take the north-south taxiway. If they exit 
at the second high speed or go to the end of the runway, they will travel west on the 
9R/27L parallel to the north-south. From there they will take the Inner (counter- 
clockwise) or the Outer (clockwise) to their gates. 



3-43 




Figure 3-12. Configuration 8 



3-44 



3. 3. 8. 3 Departures 

Flights going to 4L will travel clockwise around the Outer to the New 
Scenic directly to the end of the runway. 

Departures on 4R will go counterclockwise on the Inner and then take 
the cargo taxiway and the 4R/22L parallel to the end of the runway if arrivals are 
clearing early on 9R. If arrivals on 9R are clearing late (i. e. , at the second high 
speed or at the end of the runway) departures for 4R will use the north-south taxi- 
way to the 4R/22L parallel instead. As an alternate, some aircraft from gates 
west of the E concourse may use T3 and then go down the 14R/32L parallel and the 
north-south to the 4R/22L parallel to get to 4R. 

3. 3. 9 Configuration 9 

3. 3. 9. 1 Runways 

This configuration, shown in Figure 3-13, is similar to Configuration 
6 except that 4L replaces 9L as a departure runway. 

3.3.9.2 Arrivals 

Except for the fact that arrivals on 14L cannot turn off on 22R because 
4L is being used for departures, the arrival patterns for this configuration are the 
same as for Configuration 6. 

3. 3. 9. 3 Departures 

The basic departure patterns and alternates in this configuration are 
identical to those in Configuration 6. 



3-45 



•"£•**' 





-V>J^x 
xx V xo„ 

XX. \ \\\ 

^y^x 

J?%Xx ;X 



LEGEND 

B»«f»«Bi0 Arrivals 
• ••••••• Departures 

■■» • «■» Combined 
Fine lines represent alternate 



V" 



Figure 3-13. Configuration 9 



3-46 



3.3.10 Configuration 10 

3. 3. 10. 1 Runways 

This configuration, shown in Figure 3-14, is used when there are strong 
northeast winds. Runways 4L and 4R are used for arrivals, with 9L and 9R used 
for departures. 

3. 3. 10. 2 Arrivals 

Flights landing on 4L turn off at and go down 18 onto 14L to the bridge 
or turn off directly on to 14L. From the bridge they go clockwise around the Outer 
to the ramps. An alternate path is down 18 to the 9L/27R parallel, westward to the 
Inner, and around counterclockwise to the ramp. This is used for flights to gates 
west of the E concourse when there is heavy traffic on the Outer. It is not used by 
747s. 

On 4R, arrivals turn off at the end of the runway and take the cargo 
taxiway westward to the Outer. As an alternate they may take the high speed turn- 
off to the 4R/22L parallel to the cargo taxiway. 

3. 3. 10. 3 Departures 

Flights departing on 9L go clockwise around the Outer to the New 
Scenic and across to the end of the runway. For 9R, flights proceed on the Inner 
or Outer to the north-south taxiway and on to the 9R/27L parallel westward to the 
runway. 

3. 3. 11 Configuration 11 

3. 3. 11. 1 Runways 

Runways 14R and 22R are used for arrivals with 27L and either 9L and 
14L for departures in this configuration, shown in Figure 3-15. 



3-47 




! r? 






,->> 










LEGEND 
■»«■»«■• Arrivals 

Departures 
am • «■» Combined 
Fine lines represent alternate 
routes 



Figure 3-14. Configuration 10 



3-48 



J***' 




! \\X 7/P 










LEGEND 

n»«n»iin» Arrivals 
»••••••• Departures 

■bb • 9mmm Combined 
Fine lines represent alternate 
routes 



Figure 3-15. Configuration 11 



3-49 



3. 3. 11. 2 Arrivals 

From 14R, arrival flights use T3 to cross to the Inner (counterclock- 
wise) or the Outer (clockwise) to their gates. From 22R the Old Scenic is used to 
cross to the Inner. For 747s an alternate turnoff is the 9L/27R parallel and then 
eastward and over the bridge to the Outer. 

3. 3. 11. 3 Departures 

Departures for 27L travel counterclockwise on the Inner and cross to 
the cargo taxiway opposite the H-K ramp area and then eastward to the runway. 
The Outer (clockwise) and the New Scenic is the path used for 9L departures. The 
same path is used for 14L departures which continue across 9L on to the Scenic up 
to the 14L/32R parallel and to the runway. 



3-50 



3. 4 TERMINAL CONFIGURATION DESCRIPTION 

3. 4. 1 Terminal Gate Layout 

The basic configuration of the terminal area at O'Hare consists of a 
series of alternating "straight" and "Y" shaped concourses originating from the 
main passenger terminals. A schematic representation of the terminal area with 
each concourse and the gate numbering scheme currently employed is shown in 
Figure 3-16. The gate assignments for the various carriers as well as the type 
of gate equipment physically existing at each gate area are also indicated. 

Terminal area configuration drawings previously available from TSC 
were found to be outdated in terms of the actual gate facilities now existing. There- 
fore, the data shown in Figure 3-16 was obtained by physical inspection of each of 
the concourses by project staff personnel during the ramp data collection phase of 
this program. 

It should be noted that, while some gates were served by two jetways, 
most of the gates operate with only a single jetway or other means to facilitate en- 
planing and deplaning of passengers. Since certain gates are exclusively assigned 
to wide-bodied aircraft, while others usually used for these aircraft may under 
varying circumstances be re-assigned temporarily to smaller aircraft, the pre- 
cise number of gates available at any time for traffic operations is difficult to de- 
fine. 

In general, the "normal" number of gates which are considered to be 
available to each airline in the various ramp areas has been tabulated and shown in 
Table 3-11. Of the total of 94 gates normally available, 48 are assigned to either 
AAL, TWA, or UAL. Factors which influence the utilization of these gates are: 

1. The type of aircraft, if any, planned for the neighboring gate. 

2. Whether the aircraft planned for neighboring gates are to be 
angled or pointed normally to the finger. 



3-51 



,§&"■«»<** -© 






LEGEND 




• 


Jetway 




A 


Stairs 




a 


Stairs and Lower Jetway 


m 


Abbreviated 


Jetway 


• 


Helicopter 




LL 


Lower Level 





AIRLINES 



AAL 


American 


EAL 


Eostern 


AC 


Air Canada 


NOR 


North Central 


AL 


Allegheny 


NWA 


North West Orient 


BNF 


Braniff 


OZA 


Ozark 


CAL 


Continental 


TWA 


Trans World 


DAL 


Delta 


UAL 


United 



Figure 3-16. Gate Assignments 



3-52 



Table 3-11. Gate Assignments Vs Ramp Areas at O'Hare 



Carrier 


Ramp Area 


Totals 


B 


B-C 


CD 


DE 


EF 


FG 


GH 


HK 


K 


AAL 














2 


3 


9 


14 


AC 














1 






1 


AL 
















1 




1 


BNF 






2 














2 


CAL 






1 


1 












2 


DAL 














5 


3 




8 


EAL 








6 












6 


NOR 














3 


3 




6 


NWA 






5 














5 


OZA 










2 










2 


TWA 












6 


5 






11 


UAL 








8 


7 


8 








23 


International 


5 


3 


5 














13 


TOTALS 


5 


3 


13 


15 


9 


14 


16 


10 


9 


94 



3-53 



3. The fuel port location in the ramp surface. 

4. Type of fuel available in the fuel port. 

5. Whether the scheduled aircraft will need fuel . 

6. Whether gate jetways are required by the aircraft under consider- 
ation. 

7. If gate jetways are required, what is the required jetway extension 
capability from the terminal finger. 

Further discussions on the typical gate restrictions and the allowable 
aircraft configurations may be found in Section 4. 3 describing airline gate schedul- 
ing and control functions. 

3. 4. 2 Aircraft Docking at the Gates 

Aircraft dock at the gates at various angles relative to the finger and, 
with very few exceptions, are in a "nose-in" position during the gate occupancy 
period. The aircraft, therefore, usually require a pushback from the gate upon 
departure. The major exception to these procedures is practiced by Ozark Air- 
lines which operates with a fleet of smaller aircraft. All enplaning and deplaning 
is done from the surface of the ramp area via aircraft cabin access ladders. Al- 
though Ozark has only two nominal gate allocations, as many as seven aircraft 
were observed parked at these "two" gates. Thus, the number of aircraft docking 
spaces is somewhat of a variable and can be in excess of 100 as a result of the 
Ozark operation. 

3. 4. 3 Aircraft Movements and Control 

In general, aircraft movements within the ramps bounded by the fingers 
are either inbound or outbound. However, aircraft were observed to pass each 
other in the ramp areas between G/H, G/F, and E/D concourse if the aircraft 
equipments were of the smaller categories, i. e. , 727 or smaller. Multiple oper- 
ations were quite common and non- conflicting in the Y ramps between H/K and F/E 
concourse due to the large ramp openings provided by these Y configurations. 



3-54 



Only American Airlines and United Airlines have ramp control towers 
with ramp controllers exerting their influence on company operations in the K and 
H/K ramp areas (American), and G/F, F/E, and E/D ramp areas (United). Ex- 
cluding the Y ramps, which appear to offer no particular problem, only the K ramp 
is wholly controlled by one company ramp controller. 

As may be noted from Figure 3-16 and Table 3-11 the ramp area between 
the G/H concourses serves six carriers: Air Canada, American, Chicago Airways 
(helicopter), Delta, North Central, and TransWorld. Aircraft movements in this 
area are not usually controlled by the airlines as noted above for American and 
United. * Asa result conflicts between movements in this area were observed as 
being rather numerous. 

At times the helicopter was "trapped" by sudden pushback movements. 
As the helicopter is very light and literally flies about 2-3 feet above the ramp 
surface, helicopter operations in this ramp appear to be hazardous in the presence 
of jet engine blast. Some conflicts were also observed between TWA and United in 
the G/F ramp but virtually no inter-company conflicts were noted for the D/E ramp 
due primarily to the low level of operations of Eastern and Continental. Again, con- 
flicts were noted in the D/C ramp between international carriers and Continental, 
Northwest, and Braniff. 

The most numerous conflicts were evident for the H/G and G/F ramps 
which is consistent with the high traffic volume borne by these two ramps. 

3. 4. 4 Impact of Terminal Configuration on ASTC System Operation 

Conflicts involving blocking the movements of imminent arrivals to the 
ramp areas and departures from the ramp areas impact on the operations of the 



♦American control of aircraft for the HI and H2 gates is performed with respect 
to intra-company or company- Chicago Airways operations since the ramp con- 
troller does not have visibility of the gates unless he leaves his work station. 



3-55 



ATCT Ground Control positions. Blocking of arrivals may result in the aircraft 
having to hold on the Inner /Outer taxiways until they can enter the ramp area or 
taxi to another exit point and wait off the ends of the concourses, if the type of air- 
craft equipment permits. Several such situations were observed. Alternately, 
blockage of a departure by another departure (pushing back) or by an arrival to the 
ramp area will delay the taxi for the aircraft if it has received its taxi clearance. 
In either, these situations are likely to cause additional controller communications 
to the aircraft involved (refer to Section 4. 2). In the case of departures, it is 
possible that the Outbound Ground Controller may delay issuing the taxi clearance 
to the flight until its way is clear. 

Another factor that should be noted is that five of the airlines listed 
have gate assignments in more than one of the ramp areas identified in Figure 3-16. 
The Inbound Ground Controller must, therefore, ascertain the particular gate 
(actually the ramp area) assigned to that aircraft. For other carriers (with the 
exception of international flights and CAL whose gates are on the outer edge of the 
D concourse) the controller needs only the identity of the airline since this will 
determine the ramp area to which the "arrival" must be routed. 



3-56 



SECTION 4 - FUNCTIONAL DESCRIPTION OF THE 
O'HARE ASTC SYSTEM 

4.1 GENERAL 

The purpose of this section is to provide a comprehensive functional 
description of the current O'Hare ASTC System in terms of the roles played by 
all parties involved in the operations of the airport. The material in this section 
is divided into descriptions of the functional responsibilities and procedures em- 
ployed by FAA ATCT, airline gate management, airport management personnel. 

4. 2 FAA AIRPORT TRAFFIC CONTROL TOWER (ATCT) FUNCTIONS 

4.2.1 General Responsibilities 

The responsibilities of the FAA ATCT is to provide control of air 
traffic operations in the Chicago Terminal Control Area (TCA). This includes 
responsibilities for: 

1. Arrival and departure control for flight operations for O'Hare 
Airport and North Satellite (NAS Glenview) and South Satellite 
(Midway and Meigs) airports as well as VFR operations for 
other airports within the TCA. 

2. Arrival and departure operations and ground traffic control 
at O'Hare airport. 

3. Control of non-arrival/departure flights operating within the 
TCA. 

Execution of these responsibilities is divided between the TRACON 

and Tower Cab with the latter responsible for airport surface operations. The 

balance of this section is devoted to the description of the functional operations 

of Tower Cab personnel and to brief descriptions of the operations of TRACON 

as it interfaces with surface traffic operations. 



4-1 



4.2. 2 Tower Cab 



4.2.2.1 Tower Cab Position Descriptions 

Seven positions are manned in the tower during normal busy hour 
operations (0700-2300). These include: 

1 . Flight Data 

2. Clearance Delivery 

3. Outbound (Departure) Ground 

4. Inbound (Arrival) Ground 

5. Local Control #1 

6. Local Control #2 

7. Watch Supervisor 

The layout of the tower cab is shown in Figure 4-1, including the loca- 
tion of the controller stations. The layout of the individual controller stations 
identifying the various equipments is presented in Figure 4-2 (six sheets). Photo- 
graphs of these stations are shown in Figure 4-3 (six sheets). Tables 4-1 through 
4-5 provide summary descriptions of the responsibilities of these positions, asso- 
ciated duties, and equipments used in discharging these responsibilities. 

As indicated in these tables, the Flight Data position serves primarily 
as an assistant to the Clearance Delivery position in discharging its responsibilities 
for delivering ARTCC clearances to departure aircraft. The FDEP printer and 
Flight Strip Bay located between the Flight Data and Clearance Delivery Positions 
are the major equipments employed to accomplish this. One of the major duties 
associated with this function is annotating the flight strips to reflect local restric- 
tions and to assist the subsequent employment of the strips by the controller posi- 
tions. The other major responsibility of this position is to disseminate informa- 
tion on the status of the operating conditions to both airport users and other con- 
troller positions. This is accomplished through employment of the Telautograph 
equipment to receive U.S. Weather Service reports and NOTAMs and to transmit 
operational status reports (e.g. , Gate Hold Procedures are in effect) to similar 



4-2 




4-3 







Figure 4-2. Tower Cab Detail (Sheet 1 - Key for Orientation) 



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Figure 4-3. Tower Cab Photographs (Sheet 1 - Key for Orientation) 



4-10 




Photograph 1 




Photograph 2 



Figure 4-3. Tower Cab Photographs (2 of 6) 



4-11 




Photograph 3 




Photograph 4 
Figure 4-3. Tower Cab Photographs (3 of 6) 



4-12 




Photograph 5 




Photograph 6 



Figure 4-3. Tower Cab Photographs (4 of 6) 



4-13 




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Figure 4-3. Tower Cab Photographs (5 of 6) 



4-14 




Photograph 9 



Figure 4-3. Tower Cab Photographs (6 of 6) 



4-15 



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equipments at airline and Butler Aviation operations desks. In addition, the weather 
reports are posted for other tower personnel and in conjunction with changes in air- 
port runway configuration to prepare revised ATIS recordings. 

The major responsibility of the Clearance Delivery position is to de- 
liver the ARTCC IFR clearance to departure aircraft and to verify that the flight 
crew has properly received the clearance. In accomplishing this the FlightStrip Bay/ 
flight strips and VHF radio serve as his primary equipments. In the case of VFR 
departures, the duties associated with this responsibility also include ascertain- 
ing the desired direction and altitude of exit from the TCA and preparation of 
a VFR flight strip. The other responsibility of this position is to receive notifica- 
tion that aircraft are ready for taxi or for pushback, where the situation requires 
clearance to do so, and to turn these aircraft over to the appropriate ground con- 
trol position for these aircraft. The particular position will depend on whether or 
not the aircraft is a normal departure or a cargo/hangar area flight, whether or not 
the aircraft requires a pushback clearance, and the level of traffic at the time push- 
back is required. 

The Outbound Ground position is responsible for issuing taxi clearances 
to departure aircraft, including the assignment of the departure runway and route 
to the runway, and assuring the safe and expeditious flow of the aircraft along the 
assigned route. The one exception to this responsibility for departure taxi clear- 
ance is helicopter flights which are the responsibility of the Inbound Ground position. 
During both the transmission of the taxi clearances and maintenance of the traffic 
flow, the Outbound Ground controller is responsible for monitoring the traffic flow 
through visual observations or pilot position reports and to transmit the necessary 
control instructions or traffic advisories to resolve potential conflicts between 
aircraft. This position is also responsible for turning these aircraft to the Local 
Control position responsible for the assigned runway when the aircraft is safely 
established on the taxi approach to the runway. This point will vary for various 
runways depending on the runway configuration in use and traffic flow associated 



4-27 



with this configuration. Under certain configurations this will require this position 
to assume responsibility for safely seeing aircraft across an active runway before 
the turnover is accomplished. 

Similarly, the Inbound Ground position is responsible for issuing taxi 
clearances to arrival aircraft, including the route to their airport destination, and 
assuring the safe and expeditious flow of the aircraft along the route. In discharg- 
ing this responsibility, this position is responsible for accommodating aircraft 
whose terminal gate is not available for occupancy. This requires ascertaining 
the availability of aircraft gates and routing affected aircraft to interim holding 
areas most suitable for rapid access to their gates when they become available. 
As noted above, this position has the responsibility for ground taxi of helicopter 
traffic, both departures and arrivals. In addition, the Inbound Ground position 
has responsibility for control of traffic between the passenger terminal and the 
hangar and cargo areas, in either direction. Similar to the Outbound Ground posi- 
tion, this position will monitor aircraft movements through visual observation or 
position reports to identify potential conflicts or delays in traffic flow and issue the 
control instructions and/or traffic advisories necessary to resolve them. However, 
unlike the Outbound Ground position, the Inbound Ground position has no flight strips 
for his traffic and has no responsibility for turning the aircraft over to another con- 
trol position. 

The major responsibility of the Local Control position is the establish- 
ment and maintenance of a safe and expeditious runway operations sequence. The 
Local Control #1 position has this responsibility for runways on the south side of 
the passenger terminals and the Local Control #2 position for runways on the north 
side of the terminals. The Local Control #2 position actually operates at the Local 
Control #4 work station. * In discharging this responsibility these positions are 



*The tower cab layout provides a number of additional work stations to allow for 
future expansion of the tower staff in the event that it becomes necessary. 



4-28 



required to monitor the movements of arrival and departure aircraft visually or 
through position reports to determine that safe separations between arrivals and 
departures on the same or different runways are achieved without undue delays to 
these operations. This requires assuring that these operations will be completed 
taking the necessary control actions to maintain traffic flow whenitbecomes neces- 
sary to abort an operation. The second major responsibility of the Local Control 
position is to turn landed aircraft over to the Inbound Ground position for taxi to 
their airport destination when they are safely clear of other runway operations. 
In certain runway configurations this requires the Local Control position to main- 
tain control of aircraft and provide the necessary taxi instructions to see the air- 
craft across the last active runway under his responsibility. This is more fre- 
quently required of the Local Control #2 position. 

The Watch Supervisor is generally responsible for monitoring the 
status of surface operations and supervising the activities of the preceding control 
positions. Specifically, the Watch Supervisor is responsible for monitoring the 
local conditions affecting airport surface operations, selecting the most suitable 
runway configuration for use under these conditions, and coordinating this decision 
with the TRACON Watch Supervisor and tower cab controllers. In addition, under 
situations where weather or other conditions (local or external to O'Hare) result 
in problems of delay and surface congestion, the Watch Supervisor will determine 
whether departure aircraft must be held at their gates, arrivals held, or these 
operations carefully metered until the congestion is reduced. This decision will 
be coordinated with the TRACON Watch Supervisor and transmitted to tower cab 
personnel. 

4.2.2.2 Visibility Constraints of Tower Operations 

The operations of tower cab control positions are influenced by visi- 
bility conditions. The limits of visual coverage of surface operations are illus- 
trated in Figure 4-4 under VFR and Category I conditions. Locations at which 
controller visual observation of aircraft movements or position on the surface 



4-29 




Blind Spots 
Perception Difficulty 



Figure 4-4. Visual Surveillance Limitations 



4-30 



is physically blocked by airport facilities are indicated. In addition, areas in which 
controller visual perception of the position of aircraft is reduced because of their 
location relative to the tower are also indicated. 

The limits of visual coverage under Category II conditions are not indi- 
cated in this figure because of their variability. Under the best conditions when 
the fog is patchy, limited areas around the terminal gates may be visible. Under 
the worst conditions all visibility of operational areas may be lost. In addition, 
the visibility to flight crews of other aircraft around them may become quite 
limited as noted on one occasion during observations at O'Hare. 

The limits of radar coverage of airport traffic available to the tower control 
positions via ARTS Brite and ASDEBrite displays are illustrated in Figure 4-5. The 
limits of ARTS coverage represents the ranges at which beacon tracking is terminated 
by the ARTS system. With respect to the ASDE coverage , the areas in which this cover- 
age, has been classified as unreliable or of limited reliability are indicated. This 
determination was made through field tests by ATCT Operations and Airways Fa- 
cilities Sector personnel. In addition, the height at which ASDE coverage is lost 
was indicated by the Airways Facilities Sector to be 20 feet at the extreme range 
of the O'Hare radar. 

Essentially, the limits of visual coverage illustrated in Figure 4-4 
have no impact on O'Hare operations. Aircraft movements within the cargo or 
hangar areas are not normally under control of Ground Control positions. The 
term normally is used because infrequently it may become necessary to move air- 
craft waiting for departure on 14R to another runway. Under these conditions, the 
aircraft may be routed through the hangar area if that is the most feasible path to 
the other runway, e.g. , 14L. Where the visibility of the aircraft becomes blocked 
on the cargo taxiway, this situation exists only momentarily. Tower controller 
personnel have indicated that this blockage lasts only for about two seconds. 

The major impact of lowered visibility conditions on the ASTC system 
occurs at lower end of Category I and during Category n. This impact is reflected 



4-31 




LEGEND 



I I Unreliable ASDE Coverage 
I | Limited ASDE Coverage 



Figure 4-5. Radar Coverage 



4-32 



in the initiation of requests for position reports by both Ground and Local Control 
positions and the requirement for a transmission of runway RVR and/or rollout 
by Local Control. This is discussed in further detail in the following descriptions 
of controller procedures. 

4.2.2.3 Controller Operational Procedures 

Descriptions of the operational procedures employed by the various 
tower cab personnel, with the exception of the Watch Supervisor, are provided 
below. Flow diagrams for the major functional tasks performed by these positions 
are presented and serve as a reference for the discussion of the impact of weather 
and traffic conditions on controller operations. 

4.2.2.3.1 Flight Data 

Figure 4-6 illustrates the flow of the two major functional tasks of the 
Flight Data position. 

The task activities shown in Figure 4-6 (a) for the Posting of Flight Strips 
occupy the predominant part of the Flight Data position's time. Flight Strips are 
printed out approximately one hour before the Estimated Time of Departure (ETD) 
for the aircraft. Normally several flight strips are printed out at one time as well 
as notices for removal of strips for cancelled flights. The strips are removed 
from the printer and separated. Removal notices are set aside. The strips are 
then mounted in Flight Strip Holders so that they may be mounted in the Flight 
Strip Board. 

Before posting, the strips are marked by Flight Data. Marking nor- 
mally includes the following: 

1. Correction of the flight level to 240, the clearance limit for 
O'Hare, for any flight with a ARTCC clearance above 24,000 
feet. 

2. Correction of the first fix to reflect the appropriate clearance 
limits for the ATCT. 



4-33 



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3. Underlining the first fix to facilitate its recognition and use by 
the remaining controller positions. 

4. Underlining or circling the aircraft type data item when the air- 
craft is a heavy, i. e. , takeoff weight over 300,000 lbs. This is 
indicated by an H in front of the equipment type (e. g. , "H/DC86/A" 
indicates a DC8-60 series aircraft. Aircraft considered as 
heavies include the B747, DC-10, L1011, DC8-60 series, and over- 
water versions of the B707. 

In the case of United Airlines aircraft additional marking is performed 
by Flight Data. The Clearance Delivery position is required to mark the gate 
number for departures on the flight strips. Because United operates a substantial 
number of departures from gates in both the E and F terminal courses, Flight Data 
marks an F in the position where the gate is recorded. If the departure is from a 
gate in the F concourse, then Clearance Delivery is only required to record the gate 
number. If the departure is from an E concourse gate, then Clearance Delivery 
need only add the last stroke to complete the E and record the gate number. That 
has the effect of minimizing the activity of the Clearance Delivery position who 
may have to handle calls from aircraft in close succession at the expense of the 
Flight Data workload. 

The annotated flight strips are posted in the Flight Strip Board. The 
strips are posted on the left side of the Board by Operator and Call Sign. For 
domestic passenger flights, the strips are ordered roughly alphabetically by air- 
line and then in numerical order by flight number. The strips for Cargo, Butler 
Aviation, local commuter airlines and general aviation, and International Terminal 
Departures are posted in separate areas reserved for these operations also by 
alphanumeric flight identification. 

When Flight Data has completed the posting of the departure flight 
strips, the strips for cancelled flights are removed from the Board and the Strip 
Holder is disposed of. 



4-35 



Figure 4-6(b) illustrates the task sequence when Flight Data is called 
upon to assist Clearance Delivery in obtaining a clearance for a flight which has 
not been received and posted by the time the pilot calls for his clearance and in 
obtaining a ATCRBS code for VFR departures. With respect to obtaining a 
clearance, Flight Data enters the flight ID on the FDEP keyboard and requests a 
clearance. If a clearance for the flight is in the ARTCC computer, a strip will 
be printed and Flight Data will perform the strip mounting and marking as de- 
scribed above. When there is no clearance in the computer, Flight Data must 
call the ARTCC via the interphone and request a clearance. He will then manually 
prepare a flight strip and pass it to Clearance Delivery. If the flight has not called 
for taxi by the time a printed strip is received, Flight Data will process the 
printed strip in the normal manner and replace the written strip with it. 

When Flight Data is requested to obtain an ATCRBS code for a VFR 
departure, the code must be obtained from the ARTS computer. This requires 
Flight Data to walk over to the ARTS keyboard at the Local Control #1 position and 
enter a code request. Clearance delivery is then advised of the code for transmis- 
sion to the departure. To minimize the requirements for repeated transit to the 
ARTS keyboard and the associated delay in providing the code to the departure, 
it is standard procedure for Flight Data to obtain several codes (normally 10 are 
requested) at one time. The list of available codes is given to Clearance Delivery 
for his use as required. When the list nears depletion or is depleted, Flight Data 
obtains another. 

A third task of the Flight Data position not illustrated in Figure 4-6 
is maintaining the currency of the ATIS. Weather reports are periodically re- 
ceived from the U. S. Weather Service via the Telautograph. These are normally 
received hourly but will be received more frequently (e.g. , every 15 minutes) 
under Category I and Category II conditions or when special conditions exist. 
Flight Data will review these reports to determine whether a new ATIS recording 
is required. In addition, when a decision is made to change the runway 



4-36 



configuration, the Watch Supervisor will advise Flight Data to prepare anew ATIS. 
Criteria requiring the preparation of a new ATIS include: 

1. Ceiling changes of 1000 feet and all changes below 6000 feet. 

2. Changes in visibility below six miles. 

3. Changes in approaches or arrival runways. 

4. Changes in departure runways. 

5. Temperature changes of three degrees or more when the 
temperature is above 70° F. 

6. Altimeter changes of three points. 

Flight Data manually prepares the new ATIS and operates the ATIS 
console to make the new recordings. ATIS recordings are made for both de- 
parture and arrival operations. 

Among Flight Data's other duties are: 

1. Posting and advising other controller positions of newly received 
weather reports. Telautograph received weather reports are 
placed on the central column of the tower cab for review by 
other controllers. 

2. Posting and advising other controller positions NOTAMs re- 
ceived, including confirmation of run way /taxi way closings for 
snow removal or maintenance operations and removal of these 
restrictions. 

3. Dissemination of airport operations status information to air- 
craft operators. When operating conditions are such that air- 
craft operators must be advised of decisions regarding 
traffic operations (e. g. , gate holds have been instituted for all 
departures), Flight Data will transmit the advisory via the 



4-37 



Telautograph to similar equipments at the airlines and Butler 
Aviation operations desks. 

4. 2. 2. 3. 2 Clearance Delivery 

Figure 4-7 illustrates the flow sequence for the three functional tasks 
of the Clearance Delivery Position. 

The task activities illustrated in Figure 4-7(a) for IFR Clearance De- 
livery occupy the predominant part of the Clearance Delivery position's time. 
The major portion of this time is spent in relation to air carrier passenger flight 
operations and is outlined in the figure in a reasonably straightforward manner. When, 
infrequently, no flight strip can be found for an aircraft, Clearance Delivery will 
advise the pilot "Standby . Your clearance is on request" and request assistance 
from Flight Data. 

Normally the pilot will advise Clearance Delivery of the terminal 
gate from which the flight is departing. If this information is not given it will be 
requested. The gate number will be recorded on the flight strip to the right of 
the flight call sign and aircraft type. It should be noted that the gate number is 
not recorded for all departures. For airlines having a limited number of gates 
the number is not recorded. Table 4-6 summarizes the nature of gate marking 
for various airlines. This gate recording activity is shown sequentially in the 
figure for ease of illustration, but is actually performed in parallel with the 
reading/pilot repeat of the clearance. 

The flight strip is then placed in the right hand bays of the Flight 
Strip Board. As in the case of the original strip posting by Flight Data, the 
strips are ordered alphanumerically by airline and flight number to facilitate 
their retrieval when the pilot calls for taxi. 

In the case of commuter airlines or general aviation IFR departures, 
Clearance Delivery will advise the pilot to "Monitor Ground Control on 121. 75 
(or point 75)" and the strip placed in the left side of the Outbound Ground Flight 
Strip Board. 



4-38 



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4-40 



Table 4-6. Clearance Delivery Gate Marking 



Airline/Operator 


Gate Locations 


Marking Format 


No. 


Concourse 


American 


12 


K 


Number only 




2 


H 


H and Number 


Air Canada 


1 


G 


None 


Allegheny 


1 


K 


None 


Braniff 


2 


Between C&D 


None 


Continental 


2 


D 


None 


Delta 


8 


H 


Number only 


Eastern 


6 


D 


Number only 


North Central 


6 


H 


Number only 


Northwest Orient 


5 


D 


Number only 


Ozark 


2 


F 


None 


Trans World 


11 


G 


Number only 


United 


23 


E & F 


E or F and Number 


International Carriers 


13 


B & C 


B or C and Number 


Commuter 


- 


Butler 


None 



4-41 



The task sequence VFR Clearance Delivery is also reasonably straight- 
forward as illustrated in Figure 4-7 (b). For these flights Clearance Delivery must 
obtain the general heading and altitude at which the pilot wishes to fly out of the 
TCA. Normally, the departure will be cleared in accordance with the pilot's re- 
quest except where the altitude is below or above the VFR clearance limits for 
the TCA (3000 and 8000 feet respectively) or where the general direction of flight 
is in conflict with the current flight operations pattern. Clearance Delivery 
manually prepares a flight strip including the: 

1. Call sign 

2. Aircraft type 

3. ATCRBS code assigned 

4. Direction of flight 

5. Letters VFR in the center of the strip. 

This is generally accomplished in parallel with the deli very /pilot repeat of the 
clearance. In the event that the ATCRBS code is not received by Clearance De- 
livery before the flight is turned over to Outbound Ground, he will advise Out- 
bound Ground of the code for transmission to the pilot. 

The task sequence followed for Handover to Ground Control is illus- 
trated in Figure 4-7(c). When departures are ready for taxi Clearance Delivery 
is again called. In most cases the departure does not require pushback clearance 
and therefore has already pushed back. Clearance Delivery simply advises the 
pilot to monitor the Outbound Ground frequency and places the strip in the Out- 
bound Ground Strip Board. 

In those cases where a pushback clearance is required there is some 
variability in the actual procedure followed by Clearance Delivery. If traffic on 
the inner circular is light but Outbound Ground is busy and the individual manning 
this Clearance Delivery position has been checked out in the Outbound Ground 
Position, he may issue the pushback clearance and turn the aircraft over to Out- 
bound Ground in the usual manner. Otherwise, with light traffic on the inner, he 



4-42 



instructs the pilot to monitor the Outbound Ground frequency and gives the strip 
to Outbound Ground, advising him that the aircraft needs a pushback clearance. 
However, if traffic on the inner is heavy, he will instruct the pilot to monitor the 
Inbound Ground frequency and gives the strip to Inbound Ground, advising him 
that the aircraft needs a pushback clearance. This is done because traffic on the 
inner is likely to be primarily arrival traffic and, therefore, delays caused by 
the departures pushback blocking the inner will impact primarily on Inbound Ground 
operations. 

In each of the task sequences illustrated in Figure 4-7 it is shown that 
Clearance Delivery records the time (to the nearest minute) at which the aircraft 
calls for taxi. This activity is not performed for any specific traffic control 
function but for statistical recordkeeping purposes. The ATCT maintains records 
on the number of departures whose total operations time from ready-to-taxi to 
takeoff exceeds 30 minutes*. 

An infrequent diversion from the procedures described above occurs 
in the case of the Chicago Airways Helicopter departures from gate HI. Normally 
the clearance for these operations is a standing one and the aircrafts make initial 
contact with Inbound Ground for taxi. However, under conditions where there are 
delays, the normal clearance for these operations may become invalid. In this 
situation the procedure for a general aviation IFR aircraft departure is followed. 

Another infrequent diversion from normal Clearance Delivery opera- 
tions occurs under low visibility conditions. When calling for clearance or taxi, 
air carrier pilots may request information on the current general visibility and 
RVR/rollout levels for the runway anticipated, and the prognosis for lifting of 



*When the flight strip is subsequently received at a Departure Control position he 
will reference the recorded time to the current clock time and, allowing seven 
minutes for taxi (in accordance with current policy) , determine whether the de- 
parture time exceeds the 30-minute criteria. 



4-43 



current conditions. If Clearance Delivery is not busy, as is usual under these 
conditions, he will try to oblige the pilot as this information may be important 
in the decision to depart the gate. * In doing so Clearance Delivery must walk 
over to the Local Control position for that runway to determine this information 
from the weather instrumentation at the position. 

4.2.2.3.3 Outbound Ground 

The flow of the major functional tasks performed by the Outbound 
Ground position is illustrated in Figure 4-8. 

Figure 4-8 (a) presents sequence of activities for the task of Issuing 
Taxi Clearance. Upon receiving the flight strip from Clearance Delivery, the 
Outbound Ground position will review the strip to determine the first fix, aircraft 
type and departure gate as the basis for selection of the departure runway and the 
primary basis for the selection of the routing to that runway. Although the review 
of other flights and visual check of aircraft positions are illustrated in the figure 
as sequential activities, they are essentially accomplished in parallel with the re- 
view of the new strip and contribute to the runway and routing selection, respec- 
tively. The reason for presenting these activities as sequential is that the de- 
parture runway assignment is essentially automatic based on the first fix and 
routing to that runway is dictated by the runway configuration. As indicated 
earlier in Section 3. 2 aircraft departing to the north and east utilize the north- 
side departure runway while aircraft departing to the south, west, and southwest 
utilize the southside departure runway. Since each first fix is associated with a 
particular direction of flight, it serves as the primary basis for runway assign- 
ment. However, when review of the other strips (or the controllers recollection) 



*Differences in airport and airline operating minimums frequently result in de- 
cisions to cancel at the gate or may result in the inability of the flight to take off 
when it reaches the departure runway. The latter effect is discussed in para- 
graph 4.2.2.3.5. 



4-44 











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4-46 



indicates a particular heavy level of departures to the west, westbounds with a 
Debuque (DBQ) first fix may be assigned to the northside departure runway. 

As previously discussed in Section 3.3 routings to departure runways 
are basically standard for particular operating configurations. However, in cer- 
tain configurations potential alternate routings to the departure runways exist as 
described in Section 4. 3 (e. g. , to 32R counterclockwise via the outer circular and 
9L-27R parallel). Where these alternatives exist and traffic is heavy via the 
standard route, Outbound Ground may select the alternate routing for the new de- 
parture. The selection of this alternative depends on the location of departure 
gate and type of aircraft. For the above example of 32R departures the primary 
routing is via the outer and bridge. However, aircraft departing from the west- 
side of the E concourse and the B-D concourses could be routed via the inner and 
9L/27R parallel alternate with one exception. Since 747s are not permitted on 
the inner, such aircraft from these gates would have to be routed via the primary 
route. Another factor contributing to the routing selection is the existence of 
in-trail restrictions for departures in a particular direction. When such condi- 
tions exist, and the runway /taxi way usage configuration permits, Outbound Ground 
normally routes the affected flights to the runway via an alternate that separates 
them from the non-restricted departures. Using 32R departures again as an example, 
non-restricted departures would be sent via the primary route and restricted de- 
partures would be sent via the alternate. The alternative routings for the various 
major runway configurations have been previously described in Section 3. 3 and 
will not be repeated here. 

The first fix also is a primary factor in the establishment of the air- 
craft sequence to the departure runway via the route selected. Although it is not 
prescribed for Outbound Ground to establish the sequence, it is normally performed 
as a means of assisting the Local Control positions for the departure runways. 
This is based on the fact that alternating departures by direction of flight after 
takeoff (e.g. , northbound, eastbound, northbound for the northside runways) 



4-47 



contribute to the separation of traffic and, thereby, increase the operations rate 
for the departure runway. Since the first fix basically determines the direction 
of flight, it is utilized by Outbound Ground in sequencing or fitting the departure in- 
to position in the traffic flow to the aircraft. Thus, the first fixes for the aircraft 
already in the sequence, and their positions relative to the point at which the new 
departure will enter the inner /outer taxi ways after taxiing out from this gate, are 
referenced to determine where in the sequence the aircraft may be fitted to main- 
tain the alternating directions without adversely affecting the flow on the taxiway. 
When in-trail restrictions are in effect for particular directions of flight and 
where the runway /taxiway usage configuration does not easily permit the use of 
alternate routing for the restricted departures, Outbound Ground may attempt to 
sequence these aircraft in a manner that assists Local Control in achieving the 
restrictions (e.g. , northbound, northbound, eastbound where eastbounds are 
restricted). This may be particularly important, e.g. , in the case of northside 
departures on runway 4L where there is no runup pad in which Local Control #2 
can pull off the restricted aircraft until it is appropriate to release them for 
takeoff. However, when traffic is heavy and Outbound Ground cannot afford the 
time, or when delaying the aircraft's entry into the flow will block arrival aircraft 
entry into the gate area from which it is departing, Outbound Ground would forego 
any attempt to accomplish this type of sequencing. 

As indicated in Figure 4- 8(a), when aircraft movements cannot be 
visibly observed during Category II conditions, position reports may be requested 
from other departure aircraft on the taxiways to determine their locations as an 
input to the sequencing decision. 

When the runway, routing, and sequencing for the departing aircraft 
have been decided upon, Outbound Ground issues the taxi clearance for the air- 
craft. The clearance includes the destination runway and route, as a minimum, 
and then any control instructions pertinent to its entry into the taxi flow or holding 
at active runway crossings, where required by the operational configuration. The 
taxi clearance transmission may also include traffic advisories intended to facilitate 



4-48 



the compliance with the instructions provided. The clearance is provided tersely 
to minimize transmission time per aircraft. A few illustrative examples of typical 
taxi clearances are given below: 

United 108 Heavy . Your runway is 32 Right via the outer and bridge. 
Hold short of the outer. Follow a Northwest trijet coming from 
your right. 

Eastern 411 . Runway 27 Left. Left on the outer. Right turn on the 
North-South and East on the 27 Parallel. If you taxi now you won't be 
blocked by a company heavy coming from the right. 

Delta 112 . Runway 4 Right. Via the North-South. Pass behind an 
Ozark DC -9 coming from your left. Hold short 9 Right. 

During low visibility conditions, Outbound Ground may request position 
reports at selected checkpoints to assist him in maintaining cognizance of the traf- 
fic flow. Specific checkpoints are preferential to the individual manning the 
position. However, interviews with a number of controller personnel indicated 
a significant consistency among these reporting points. The predominant re- 
porting points given for taxi to the various departure runways are identified in 
Table 4-7. 

The runway to which the aircraft has been assigned is recorded by 
Outbound Ground in the lower right hand corner of the flight strip. If the departure 
has been sent to the runway by an alternate route, this is also recorded on the strip 
for use by Outbound Ground and subsequently by Local Control for that runway. 
The indication of alternate routing is marked next to the runway, e. g. , for air- 
craft routed to 32R or 27L on parallel taxiways the runway recording would 
appear as 32R 11 or 27L 11. 

The flight strip is positioned in the Outbound Ground Strip Board on 
either the left or right side of the Board: left if the departure is going to a south- 
side runway, right if the departure is going to a northside. The strip is positioned 



4-49 



Table 4-7. Predominantly Preferred Checkpoints for Position Reporting 
During Low Visibility Conditions 



Destination 




Runway 


Preferred Checkpoints 


4L 


Outer and T3 Intersection 


4R 


Outer and Past 9R on N-S Taxi way 


9L 


Outer and T3 


9R 


Outer and Holding # 1 on T 1 at 14R/32L 


14L 


Outer and T3 


14R 


Outer and T3 


22L 


Outer and On the Cargo Taxi way 


22R 


Short of 14L/32R 


27L 


Outer and On the Cargo Taxi way 


27R 


Outer and At the Bridge or 9L/27R Parallel 




(for alternate route) 


32L 


Outer and Holding #1 on N-S at 27L 


32R 


Outer and At the Bridge or 9L/27R Parallel 


36 


9L/27R Parallel 



4-50 



among the others on that side in accordance with its location in the sequence to 
the runway (with the bottom strip corresponding to the first flight in sequence. ) 
By ordering the strips in this manner, Outbound Ground has a rapid reference to the 
order of the aircraft and to their call signs when they must be subsequently contacted. 

The functional approach taken by Outbound Ground to the Maintenance 
of Safe and Expeditious Traffic Flow is illustrated in Figure 4-8 (b). Visual ob- 
servations of traffic movements and/or position reports received during low 
visibility conditions provide a basis for determination of potential conflict at an 
intersection or delays in the movement of his traffic (e. g. , an aircraft forced 
to stop momentarily behind an arrival aircraft waiting to turn off to its gate). 
Observation at O'Hare and review of communications recordings indicated that two 
distinctly different types of control approaches are employed by Outbound (as well 
as Inbound) Ground positions. The first may be considered to be singular control 
in which the controller unilaterally provides the separation or movement control 
required. This is accomplished by the controller issuing a "hold short" instruc- 
tion to which the pilots respond by stopping their aircraft at the designated inter- 
section. The second approach may be considered to be joint control in which both the 
controller and pilots share the responsibility for separation or movement control 
required. This is accomplished by the controller issuing a "yield type" instruc- 
tion to which the pilots respond by adjusting their speed of taxi rather than stopping 
their aircraft. These instructions normally include the type of control response 
desired by the controller, identification of the aircraft to which the desired 
maneuver is referenced, and an advisory of the direction from which the aircraft 
is approaching the instructed pilot. Examples of such instructions include: 

1. Yield to 



2. Give way to 

3. Follow 



4. Pass behind 



4-51 



Interviews with controller personnel and review of communications 

recordings indicate a strong preference for the joint control approach. A major 
factor in the preferential use of the "yield" type instructions is that only one 
communication to the aircraft is required. In the case of the singular control 
approach the pilot must be instructed to begin taxiing again. 

As indicated in the figure the major criteria in the decision to issue a 
hold or yield type instruction is the degree of certainty with which the aircraft 
arrivals at the intersection involved can be ascertained. When Outbound Ground 
is not sure of the intersection arrival time for an aircraft he may issue a hold 
instruction in place of a yield instruction. This same approach is followed in the 
inclusion of control instructions in the taxi clearances to departures. 

Once the control instructions have been given or simultaneously 
with their transmission, the positions of the strips in the Flight Strip Board will 
be adjusted to reflect the new order of aircraft in the sequence to the runway. 

The task sequence for aircraft handover to Local Control is illustrated 
in Figure 4-8 (c). The basic philosphy underlying the performance of this task is 
that the turnover is made whenever there is no longer any requirement for Out- 
bound Ground to work the aircraft, i. e. , it has a clear roll to the runway or end 
of the departure queue. Table 4-8 summarizes the specific points at which, or 
general areas inwhich, the aircraft are likely to achieve this status and turnover 
can be made for the various runways. 

Based upon this philosophy, the major determinants in the process 
are whether or not the departure must cross an active runway under the particu- 
lar operating configuration or whether or not there is any conflicting (or blocking) 
traffic in its way. When a runway crossing is required, Outbound Ground observes 
the operations of the Local Control responsible for that runway and determines 
when it is appropriate to clear the departure across the runway. The pilot is nor- 
mally advised to monitor Local Control frequency "when across" as part of the 



4-52 



Table 4-8. Specific Points or General Areas at Which Turnover to 
Local Control May be Made by Outbound Ground 



Departure 
Runway 


Specific Point 


General Area 


4L 


Passing T3 




4R 


Crossing 9R 




9L 


New Scenic/4L Intersection 




9R 


T1/14R Intersection 


On 9R/27L Parallel if 14R not in use 


14L 


Crossing 9L 


On 14L/32R Parallel or on New Scenic 


14R 


Old Scenic/Bypass Intersection 


Bypass or 14R/32L parallel if 14R 
not used for arrivals 


22L 


Outer/ Cargo Intersection 


On cargo 


22R 


Across 14L 


National Guard Ramp or Parallel 


27L 


Outer /Cargo Intersection 


On cargo 


27R 


Bridge 


On 9L/27R Parallel or 32R Pads 


32L 


Crossing 27L if departing from 
end of 32L 

Outer /Tl Intersection other- 
wise 




32R 


Bridge 


On 9L/27R Parallel if alternate route 


36 


Inner/9L/27R Parallel 


On 9L/27R Parallel 



4-53 



clearance transmission. Based upon the major runway configurations employed, 
this requirement mostly affects southside departures on runways 4R or 9R. 

Observations in the tower cab indicated a significant distinction in the 
handling of traffic departing from a location northwest of the cab (i. e. , on runways 
4L, 9L, 14L/R). From his work station location Outbound Ground cannot readily 
observe the movements of aircraft in the area in which the Old Scenic, New Scenic, 
and 9L/27R parallel taxiways intersect the inner/outer taxiways. Outbound Ground 
was observed to pick up the flight strips for aircraft routed to these runways via 
the Old or New Scenic and walk over to a position in the northwest part of the cab 
(usually behind the Local Control #1) from which he can observe that the traffic 
has complied with his taxi instructions. This action becomes particularly impor- 
tant when operating conditions are at the lower end of Category I and when aircraft 
are being sent to both 9L and 14R for takeoff. In the latter, departures for both 
runways use the Old Scenic until those for 14R can turn left at the Bypass taxiway 
to taxi to the 14R/32L parallel. 

When Outbound Ground is assured that the traffic is free of any inter- 
ference (e. g. , 14R departures turned onto the Bypass), he advises the pilot to 
monitor the appropriate Local Control frequency. Observations in the tower cab 
also indicated that this assurance involves a last check of the flight strip, usually 
with the controller holding the strip in his hand. 

In passing the flight strips to the appropriate Local Control position, 
Outbound Ground is required to momentarily move away from his work station. 
He must walk over to the Local Control #1 position to place the strip in the Flight 
Strip Board. For the Local Control #2 position which is located diagonally across 
the cab from him, Outbound Ground must walk over to and place the strip on the 
Strip Slide behind him and to his right. In instances where he has walked over to 
the northwest part of the cab to observe the traffic, the strip is placed on the 
Flight Strip Board or Strip Slide on the way back to his position. 



4-54 



In discharging his duties as described above, Outbound is also respon- 
sible for assuring the separation of his traffic from vehicular traffic traveling on 
or crossing the taxiways. Since such vehicular traffic is under the control of 
Inbound Ground and normally yields to aircraft, Outbound Ground may issue an 
advisory. In addition, he must monitor the movements of his traffic to ensure 
that they do not enter areas closed for snow removal or maintenance operations. 

4.2.2.3.4 Inbound Ground 

The flow of the major functional tasks performed by the Inbound Ground 
Position are illustrated in Figure 4-9. 

The sequence of activities for the task of Issuing Inbound Taxi Clear- 
ances is presented in Figure 4-9(a). 

When Inbound Ground is contacted by arrival aircraft an inbound taxi 
clearance is issued. Under normal circumstances this includes the route to the 
aircraft gate and any control or sequencing instructions that are necessary to 
accomplish this taxi. Although it is not specifically included in the figure, in order 
to simplify the illustration, the determination of the position of the aircraft and 
other traffic by visual observation and/or position report is an input to the routing and 
control/sequencing instructions given. Existing traffic conditions on the Inner/ 
Outer taxiways and the type of aircraft (particularly 747s and general aviation) 
may be factors in selecting an alternate route for the arrival, in much the same 
way they influenced the route selection by Outbound Ground. The routing alterna- 
tives for the various major runway configurations have been described in Section 
3. 3 and will not be discussed further here. 

In addition, the relative positions and certainty of arrival at intersec- 
tions are considerations in the nature of the control instructions given to the 
arrival. As an example, for an arrival on runway 32L exiting the runway at T5 
or T6, the normal routing is south on the parallel, left on T3 to the outer, andthence 
by the inner or outer to its gate. If Inbound Ground is not certain of the time at 



4-55 



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4-56 



which the aircraft will reach the T3/Outer intersection to mix with the other traffic, 
he will instruct the aircraft to hold short of the Outer. 

Although sequencing or ordering of arrivals in the traffic flow is not a 
requirement for Inbound Ground, it is performed by many of the controller personnel 
at O'Hare. When it is feasible to accomplish this, Inbound Ground attempts to 
reverse the order of the arrival traffic at which the aircraft will reach the points 
where they would exit the Inner/Outer to their gates. The object is to allow the 
aircraft to peel off from the traffic as they reach their gate exits and, thus, 
minimize the number of aircraft that might have to stop behind an arrival if its 
exit from the Inner/Outer is blocked momentarily by other traffic, primarily in the 
ramp area in which their gate is located. Observations and data collected at O'Hare 
have indicated that this is not an infrequent occurrence and in one instance resulted 
in six aircraft being stopped on the inner taxi way. 

Ordinarily the Inbound Ground is provided by the arrival pilot with an 
indication of his location at the time initial contact is made. However, the con- 
troller interviews and analysis of communications revealed that such position reports 
must be obtained occasionally, and more often than infrequently, because they are 
not provided by the pilot. Under this situation the typical contact message is 
"O'Hare Ground. This is (aircraft call sign) with you off (runway) . " When this 
occurs nearly simultaneously for two aircraft from the same airline the problem 
is compounded. 

Aircraft destination gate and the availability of that gate are important 
factors in the taxi clearance and routing for arrivals. It is particularly important 
for those airlines which operate gates in more than one terminal building concourse 
or ramp area or which by experience are most likely to have gate unavailability problems 
during peak traffic periods and during or following periods of traffic delays due to 
poor weather/visibility. These airlines include American, Trans World, United, 
Delta, North Central and internationals, with the first three frequently subject to 
gate delays. If the pilot directly advises Inbound Ground that his gate is 



4-57 



unavailable, the aircraft will be routed to an appropriate holding area. If the gate given 
the arrival is one for the three major airlines subject to gate delays of if for other 
airlines there are aircraft already holding for gates, Inbound Ground normally 
checks to see that the gate is available. If the gate is not given, he will request the 
pilot to advise him of the gate. If the identified gate is observed to be occupied, 
he will ask the pilot to verify its availability and advise him. If the pilot then 
responds that there will be a delay the aircraft is routed to an appropriate holding 
area. Normally, the taxi instructions are given to start the aircraft toward its 
gate and the above inquiries made while he is taxiing. 

The basic philosophy applied in assigning aircraft to particular waiting 
areas is to hold the aircraft as close to their gates as possible for the conditions 
and operating configurations. Therefore, within the framework of this philosophy, 
an attempt is made to reserve the use of the T3 penalty box for use for aircraft 
going to the gates at United and west of the United E concourse and to use the 9R/27L 
parallel stub and North-South taxiways for use for aircraft going to gates east of 
the United terminal, primarily American and Trans World. Where the operating 
configuration does not permit this approach or where the pilot has advised Inbound 
Ground that the delay will be lengthy, other locations may be used as holding areas. 
These areas include the run-up pads at 9L, 32R, 32L, 14R and the hangar area 
depending on the operating configuration. The one major rule followed in select- 
ing a holding area for waiting aircraft is to avoid an area from which the aircraft 
must cross an active runway to taxi to his gate. 

Because there are no flight strips for arrivals, Inbound Ground records 
the flight call sign and assigned gate, if pertinent, on a scratch pad. Two lists 
are maintained on the pad, one for arrivals from the southside runways and one 
for arrivals from the northside runways. In the event that it is necessary to hold 
an aircraft for a gate, the location at which it is holding is also recorded. For 
aircraft holding in the T3 penalty box, a box is simply drawn around its call sign. 
For aircraft waiting at other locations the specific location is recorded next to the 
call sign. 



4-58 



The functional sequence followed in the task of Maintaining Safe and 
Expeditious Traffic Flow is presented in Figure 4-9(b). Essentially, Inbound 
Ground operation observes the same principles in controlling the traffic flow as 
discussed for Outbound Ground, including the use of hold versus yield type instruc- 
tions. The major difference in their performance of this task relates to the exiting 
of aircraft from the Inner /Outer taxiways to their gates. As noted earlier for this 
position, the aircraft's exit may be blocked by other aircraft, most frequently air- 
craft departing from gates in the same ramp area as the arrivals gate. The two 
factors influencing the actions taken by the Inbound Ground are the estimated time 
for which the blockage will exist and the amount of traffic behind the arrival. If 
the departure has already pushed back or is taxiing out, the delay is likely to be 
short and, if traffic behind the arrival is light, it may be instructed to hold or 
yield to the other aircraft at the exit intersection. However, if there is heavy 
traffic behind the arrival it may be instructed to taxi to and exit at the next inter- 
section, if feasible for reaching its gate. When the departure is just pushing back 
or there are a number of departures in the ramp area, the delay is likely to be more 
lengthy and Inbound Ground may provide additional taxi instructions to take the air- 
craft in a circular path on the Inner and Outer or to take the aircraft to an area 
where it can hold momentarily out of the way of other traffic (e. g. , the stub or 
North-South taxiways between the Outer and 9R/27L Parallel). 

When the arrival has cleared the Inner taxiway and entered the ramp 
or when under Category II conditions the pilot reports docking at the gate as re- 
quested, the aircraft is eliminated from the active lists on the scratch pad by In- 
bound Ground by striking out its call sign. 

There are three other functions which are performed by Inbound that are 
not illustrated in Figure 4-9. The first is providing control of aircraft taxiing 
between the terminal gates and the cargo and hangar areas in either direction. 
Essentially, aircraft taxiing to the terminal are treated as if they are arrivals 
and are provided routing and control instructions, as appropriate, to their 



4-59 



destination gate as well as a control enroute. Aircraft taxiing from the terminal 
building are treated essentially as if they are departures with the exceptions that 
they are given clearances to the cargo or hangar area rather than a runway and 
fitted into the Inner /Outer traffic whenever and as soon as it is feasible to do so 
and controlled enroute. 

The second additional function is issuance of pushback clearances. As 
previously explained in paragraph 4. 2. 2. 3. 1 this task is performed when the traffic 
on the Inner, which under normal conditions is predominantly arrivals, is heavy. 
In accomplishing this task Inbound Ground observes the traffic movements on the 
Inner visually, or may obtain a position report as required under Category II condi- 
tions, to determine where there is a sufficient gap in the traffic to permit the push- 
back without significantly delaying other traffic. The clearance to push back is given 
and the pilot advised to monitor the Outbound Ground frequency for taxi instructions. 
The flight strip for the aircraft is then placed in the Outbound Ground Flight Strip 
Board and Outbound Ground advised that the aircraft is pushing back. 

The third additional function is assuring the separation of aircraft 
and vehicular traffic traveling on or crossing the runways. In most circumstances 
this will involve airport vehicles enroute or returning from snow removal or other 
maintenance operations on particular runways or taxiways or traveling from one 
work area to another. Since individual vehicles or at least the lead vehicle in an 
operating crew must be radio equipped, control instructions regarding these move- 
ments are provided via the radio channel. When the vehicles have reached or are 
within their work area, control is not normally exercised since the area will have 
previously been closed to aircraft traffic. However, Inbound Ground must monitor 
the movements of his traffic to ensure that they do not in error enter the closed 
area. 

4. 2. 2. 3. 5 Local Control 

The performance sequence for the major functional tasks of the Local 
Control position is illustrated in Figure 4-10. 



4-60 










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4-62 



The functional sequence for the task of Clearing Arrivals for Landing 
is shown in Figure 4-10(a). 

The approach of arrivals is monitored on the ARTS Brite Display. De- 
pending on the activities of the Local Control the call sign of next arrival in the 
sequence may be recorded on the Arrival Log from this display prior to the pilot's 
contact at the outer marker or simultaneous with this contact. Where the aircraft 
is a "heavy" this fact is also recorded. When the approach is made under Category 
II conditions this fact is also recorded. This log is primarily maintained for statis- 
tical record-keeping purposes of the ATCT since no flights strips are available 
for arrivals. However, for this reason it is likely that at least the call sign and 
heavy indication would be recorded by Local Control to keep track of the aircraft 
he is working just as does the Inbound Ground position. 

The operations of Local Control in performing this task are reasonably 
straightforward under good visibility conditions as shown in the figure. At the in- 
bound contact the pilot is cleared to land and advised of local runway conditions such 
as winds (if sufficient to warrant it) and turbulence resulting from the immediately 
preceding landing or departure by a heavy aircraft. When the runway is wet or 
there is snow or ice the advisory may indicate poor braking conditions. Local 
Control visually monitors the landing to assure that it canbe safely completed and if not 
to execute a missed approach. This would be required under the following conditions: 

1. The preceding arrivals will not clear the runway in sufficient time. 

2. The required separation between the preceding departure on 
the same runway or a crossing runway will not be achieved. 

3. A departure on the runway was delayed because of late clearing 
by the preceding arrival and cannot itself clear the runway. 

4. An aircraft crossing the runway will not clear in sufficient time. 

With the exception of a missed approach, Local Control may not have 
further communications with the arrival unless, and until, he makes a request of 
the aircraft to clear the runway at a desired exit point. This request is usually made 



4-63 



only when the runway is being used for both arrivals and departures. In addition, 
this request is normally made after the aircraft has touched down. 

If a missed approach is given by Local Control or declared by the pilot, 
Local Control issues the standard heading and altitude for the maneuver and advises 
the pilot to contact Departure Control. A minimum flight strip must be manually 
prepared and dropped down the Flight Strip Tubes to Departure Control. 

As the visibility decreases, performance requirements for this task 
significantly increase. When Local Control can no longer visually observe the ap- 
proach to the runway from the tower cab, he will begin requesting pilots to "Report 
the runway lights in sight during the initial contact. " This situation may exist at 
low Category I as well as Category II conditions. The rationale given by controllers 
for this is that when the pilot can report seeing the lights he is more likely to be 
able to complete the landing and conversely when he cannot the potential for a 
missed approach increases. 

In addition, when the RVR decreases below 6000 feet Local Control is 
required to advise the pilot of the measured RVR. When visibility further decreases 
and the measured rollout (RVR at other end of the runway) is below 2000 feet and 
less than the RVR it too must be given to the pilot. These advisories are also given 
during the initial contact. 

At low Category II conditions another problem develops. Many of the 
airlines have established operating minimums which are below the permissible 
operating minimums for the aircraft. Thus, it is not unlikely for the pilot to 
inform Local Control thatthe advised minimums are below those of the airlines. When 
this occurs Local Control normally requests the pilot's intentions. If he indicates 
that he wants to wait for better conditions, Local Control will execute the missed 
approach procedure outlined above. Because the RVR and rollout can change 
rapidly this does not usually occur. Local Control usually, then, advises the pilot 
to "continue the approach and I will keep you advised". At about 1 mile from the 
runway, and usually before the aircraft disappears from the ARTS Brite, Local 



4-64 



Control will advise the pilot of the current RVR and rollout at which the pilot will 
elect to complete or abort the landing. 

Under the lower visibility conditions Local Control may repeat the 
clearance to land when the pilot reports the lights or when the conditions have risen 
sufficiently to permit him to land. 

The task activities in the next phase of the handling of arrivals by 
Local Control, Handover to Inbound Ground, is shown in Figure 4- 10(b). Under 
normal conditions Local Control will visually observe the arrival clear the run- 
way. The pilot is not required to report clear, although many do. Under Category II 
conditions Local Control may observe the aircraft clear on the ASDE Brite. How- 
ever, because of the low reliability of the ASDE presentation as described in para- 
graph 4. 2. 2. 2, most controllers request the aircraft to report clearing. 

The manner in which the arrival is handled after clearing the runway 
differs depending on whether it must cross an active runway to taxi to the terminal 
gate or other destination. In those instances where there will be no runway cross- 
ing, Local Control, depending on the runway, may issue limited taxi instructions 
to the arrival to start it moving toward the terminal and avoid its blocking of that 
runway exit for the next arrival. At the same time the pilot is advised to contact 
Inbound Ground. As an example of this procedure, aircraft landing on 32L would 
be told "South on the parallel. Contact Ground on 121. 9" after clearing the runway. 

Where no limited taxi instructions are required the pilot would be 
advised simply to contact Ground after it has cleared. Frequently, Local Control 
may advise the pilot of the frequency change while the arrival is decelerating on 
the runway, e. g. , " (Aircraft Call Sign) . Contact Ground Control on 121. 9 when 
clear. " 

Where a runway crossing is required Local Control retains the arrival 
until it clears the last active runway under his control. This situation most 
frequently is faced by the Local Control #2 position when the airport is operating 



4-65 



in an "arrivals from the west, departures to the east" mode with 14L as the arrival 
runway. In this situation, the arrival is given instructions for taxi to and to hold 
short of the runway. In addition, Local Control normally advises the aircraft to 
remain on his frequency. An example of such instructions is "( aircraft call sign) . 
Taxi south on 22 (or 18). Hold short of 9L. Stay with me. " 

When Local Control determines that it is safe to cross the arrival he 
clears it across the runway and advises the pilot to contact Inbound Ground when 
across. 

The functional sequence for Clearing Departures for Takeoff is pre- 
sented in Figure 4- 10(c). When flights are received from Outbound Ground, Local Con- 
trol will r e view them to identify the first fix, aircraft type, and whether the aircraft 
are taxiing to a runway by an alternate route. This action and visual observation 
of the aircraft movements serve as inputs to establishing the runway usage or 
takeoff sequence for the various departures. Taxi instructions are given as necessary 
to aircraft to establish the sequence and the flight strips are ordered in accordance 
with that sequence, with the order being from bottom to top in the Flight Strip 
Board. 

Under normal visibility conditions, the manner in which the departures 
are handled is reasonably straightforward. The most significant consideration 
is whether the runway is being used for arrivals. In such situations, Local 
Control will check the positions of the arrivals to determine whether there will be 
time for the takeoff before instructing the pilot to position and hold on the runway. 
At the time the lead aircraft is given this instruction, the second aircraft in the 
sequence may be told to followthis aircraft. A procedure followed by most of the con- 
trollers observed to note they have given these instructions is to make a small 
mark next to the runway designation on the strip or the upper right hand corner of 
the strip. 

When the pilot is instructed to position and hold he is also advised of 
local runway conditions as required by the situation, including turbulence from 
the preceding arrival on the runway or the crossing arrival runway. 



4-66 



The positions of arrival are checked to determine when the departure 
can be cleared for takeoff. When the runway is being used for arrivals and de- 
partures, the check is made to determine that the preceding arrival is clearing 
the runway in sufficient time to permit the takeoff with the required separation 
between the departure and succeeding arrival. If this is not the case, Local Con- 
trol instructs the departure to taxi off the runway, if feasible, to allow the arrival 
to land or, if not feasible, instructs the arrival to execute a missed approach. When 
it is safe to do so the departure is cleared for takeoff. 

The issuance and recording of the departure heading are shown in 
Figure 4- 10(c) as sequentially following the takeoff clearance for ease of illustra- 
tion. In actuality, the point at which this instruction is given to the departure or 
the heading recorded will vary with the operating situation and controller. When 
the departure is being used for departures only, the heading may be given to the 
pilot with the local conditions or as part of the takeoff clearance. The heading 
may be recorded on the strip (to the right of the runway notation) prior to or during 
its transmission. In some cases Local Control was observed recording the heading 
even before the departure was instructed to position and hold. However, if the run- 
way is being used for mixed operations, it is more likely that the heading will be 
issued as part of the clearance to takeoff or when the departure is in the air (if the 
time available for takeoff is short) and the heading recorded at that time. In the 
latter case, Local Control normally advises the pilot "I will have a heading for 
you in the air" as part of the positioned hold/local conditions advisory communi- 
cation. 

Local Control monitors the takeoff visually to determine that it is being 
completed safely. In situations where the takeoff is aborted before the aircraft 
becomes airborne, he will determine from the pilot if an emergency exists and 
immediately initiate the necessary action. If there is no emergency he will instruct 
the pilot to taxi clear of the runway and after ascertaining the pilot's intentions either 
issue the necessary instruction to take the aircraft back into line for departure or 
start it back to the terminal. 



4-67 



As in the task of Clearing Arrivals for Departure, the performance re- 
quirements for this task increase significantly as the visibility conditions decrease. The 
first effect noted is that, when the departure runway is being used for arrivals as 
well, the pilot of the lead departure aircraft may be requested to advise Local 
Control "when the arrival is by" in order that he can instruct the pilot to position and 
hold. In addition, he is likely to request the pilot to report when in position. Under 
lowered visibility conditions RVR and rollout must be given to the pilot as part of 
the local conditions advisory. For the same reason discussed with respect to arrivals, 
the departure pilot may not be able to take off under the existing conditions. In this 
case, the flight is treated similarly to an aborted takeoff as shown in Figure 4- 10(c). 
If the takeoff can be made, Local Control is most likely to request the pilot to 
report rolling, becoming airborne, and starting the turn to the departure heading 
as a means of monitoring the progress of the takeoff. 

The task sequence for the next phase in the handling of the departure, 
Handover to Departure Control, is presented in Figure 4-10(d). Under normal 
visibility conditions, Local Control visually observes the aircraft climb out and 
turn maneuvers, issuing the departure heading if not given previously. Under low 
visibility conditions he will receive the airborne and starting turn reports from the 
pilot as a substitute. The latter report is most significant as it serves as cue to 
the issuance of the handover instructions. 

When the aircraft is determined to be started toward its designed de- 
parture heading and no further attention is required, the pilot is instructed to con- 
tact Departure Control and the flight strip dropped down the Flight Strip Tubes to 
the Departure Control position in the TRACON. Observations in the tower cab 
indicated that, under normal visual operations, most controllers will pick up and 
hold the strip for a final check when issuing the frequency change. 

Further attention may be required for a departure when there may be some 
possibility of safe separations between departures not being achieved. This may occur 
because of an unusual takeoff for the aircraft or where the departure path will take the 



4-68 



aircraft across the path of the departure for the other Local Control positions. This 
latter situation may occur, for example, where a westbound departure has been routed 
to the northside runway for reasons discussed earlier in connection with the Out- 
bound Ground position. Where further attention is best provided by Departure 
Control, Local Control coordinates with Departure Control via the interphone when 
the aircraft is turned over. Otherwise, Local Control will request the necessary 
reports and/or issue the necessary instructions to resolve the problem and, where 
the situation requires, coordinate with the other Local Control position. A par- 
ticularly significant situation in which this additional Local Control attention is re- 
quired is that in which an arrival on the same runway or crossing runway must 
execute a missed approach and in which the heading for the standard missed approach 
is in roughly the same direction as the heading for the previous departure. In such 
situations, Local Control would be required to obtain frequent reports of the altitude 
status of the aircraft involved, with particular emphasis on the departure, to ensure 
that safe separations are maintained. 

Quantitative measurements of the communications and physical task 
activities described in the preceding paragraphs are provided in Section 5. 4. 

4.2.3 TRACON 

The TRACON includes 23 operating positions. The positions are 
basically divided into Departure Control and Approach Control. Associated with 
the Approach Control position is the Parallel Approach Monitor position. Its 
function is to monitor aircraft making parallel approaches on Runways 14, 32, 
and 27 when such approaches are in effect. Figure 4-11 is an illustration of the 
TRACON Room layout depicting the positions of the various controller positions. 

Tables 4-9 through 4-11 illustrate the responsibilities and duties of 
arrival, departure and parallel monitor positions as they interface with O'Hare 
Airport operations. 



4-69 




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4-73 



4.3 AIRLINE FUNCTIONS 

4.3.1 General Responsibilities 

The airlines are the major source of aircraft traffic at O'Hare. The 
manner in which they discharge their responsibilities can significantly impact the 
operations of the overall ASTC System, and the performance requirements placed 
on control positions in the ATCT. This is particularly true in the case of the 
major airlines that contribute more than 50 percent of the traffic (i. e. , United, 
Trans World, and American) and those other airlines that operate a significant 
number of flights (i. e. , Delta, Eastern, North Central, Northwest Orient, and 
Ozark) from the passenger terminal. As an example, the impact of airline opera- 
tions on the ASTC System is most felt when disruptions of flight schedules are 
experienced or delays in the scheduled departure of flights result in the unavail- 
ability of gates for arrival aircraft. The effect of gate unavailability on inbound 
ground operations was discussed in the previous section. Therefore, the following 
discussion is addressed primarily to these major organizations, with exceptions 
noted. 

The responsibilities of the airlines include: 

1. Establishment of a plan and schedule for the allocation of passen- 
ger terminal gates for departure and arrival operations (with the 
exception of Ozark which does not use nose-in parking at their 
two gates). 

2. Monitoring adherence to this plan with respect to the basic flight 
operations schedule and the existing conditions and adaptation of 
the gate assignment plan as required. 

3. Advising pilots on arriving flights of their assigned gates and 
occupancy availability. 

4. Controlling the pushback and start-up departures and the move- 
ments of departure and arrival aircraft within the ramp areas. * 



*This applies to all airlines. 



4-74 



5. Establishing contact with the ATCT for entry into and passage 
through the system. * 

6. Advising the ATCT of the status of aircraft equipment and airline 
facilities that impact on the requirements for control of the air- 
craft. * 

7. Adherence to control instructions provided by the ATCT. * 

8. Adherence to rules governing the movements of service vehicles 
on the airport surface. * 

Responsibilities 1 to 4 are discharged by operations personnel located 
within the terminal facility or at the gates. Responsibilities 5 to 7 are discharged 
by aircraft flight deck (cockpit) personnel. Responsibility 8 is discharged by the 
operators of service vehicles. 

The remainder of this discussion of airline functions is related to 
terminal operations and flight deck personnel. The information related to terminal 
operations planning and control was obtained through interviews with the major 
carriers and observations of their facilities. Therefore, it may not reflect in all 
details the operations of other carriers. The information related to flight deck 
functions was also obtained through interviews with pilots for the major carriers. 
However, it is believed that the description of these functional operations reason- 
ably reflects the operations of flight deck personnel in most respects. 

4.3.2 Airline Terminal Operations 

The airline terminal operations functions which are directly related to 
the planning and control of aircraft operations are gate scheduling and control and 
gate operations. These functions are normally performed by separate operating 
organizations whose activities are coordinated with one another by procedural 
methods. The performance of these functions by the various personnel involved 
is described below. 



*This applies to all airlines. 



4-75 



4.3.2.1 Gate Scheduling and Control 

Flight scheduling is essentially accomplished by schedule analysts 
working with information provided by the Marketing Department and with specific 
facilities criteria provided by the individual stations served by the carrier. The 
information thus developed provides the necessary input to determine the type of 
aircraft to be utilized and the specific schedules to be implemented for the various 
routes. 

The operating units responsible for gate assignment atO'Hare are the 
Ramp Service Departments. These units are essentially responsible for planning 
and day-to-day management for the activities related to the various gate areas. 
Typical of these activities are passenger and cargo planning, gate/flight planning, 
load planning (weight and balance), passenger flight processing (including updating 
of the flight information displays within the terminals), advanced departure proc- 
essing (including updating of the flight information displays within the terminals), 
advanced departure processing, maintaining and updating a gate assignment board, 
inbound flight monitoring, and ramp control operations. 

Gate assignment/schedule planning is accomplished by manual means 
and, except for minor differences in requirements due to holidays, weekends, 
etc. , these schedules remain essentially constant for extended periods of time. 
Major revisions have, in the past, been effected in the spring and fall when day- 
light saving time changes are instituted. Figure 4-12 illustrates a typical gate 
assignment plan for the hours 1400 to 2400 provided by United Airlines for the 
period beginning January 3, 1974. * The plan indicates the flight number, type of 
equipment (by the letters following the flight number), and whether the flight is an 
originating, terminating, or through flight. Originating flights are shown with 
no closing bracket on the right, terminating flights with no closing bracket on the 
left, and through flights with closing brackets on both ends. Where the aircraft 



*Provided through the cooperation of United Airlines. 



4-76 



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4-77 



equipment for a terminating flight remains at the gate for an extended period and 
then is used for an originating flight a dashed line is shown. 

Examination of this schedule reveals that the predominant number of 
flights are through flights. This is true for the other major and significant car- 
riers. Further examination of the schedule reveals that flight operations are 
scheduled around particular hours of the day. O'Hare Airport is referred to as a 
"bank station"; that is, aircraft operations are scheduled in banks to provide: 

1. Service at the hours determined to be most desirable for passenger 
travel by the Marketing Department. 

2 . Optimum interconnection of flights to retain a desired share of the 
estimated interconnecting passenger market. 

This "bank" operation is also characteristic of the schedules of the 
other major and significant carriers at O'Hare as well as United. 

The factors considered to be most important in the planning of gate 
assignments are: 

1. Aircraft size. 

2. Preceding or next airport for the flight (with preferred market 
airports served primarily from the gates closest to the entrance 
of the concourse). 

3. Aircraft servicing time (which is dependent on whether the flight 
is originating, terminating, or through). 

Other factors which are considered in gate planning are gate size 
restrictions, spacing between departure and arrival aircraft at a specific gate, 
extra sections for holiday traffic, placement of connecting flights at gates in close 
proximity to each other, and passenger convenience. 

Minimum time intervals between the scheduled departure of one air- 
craft and the scheduled arrival of another are currently on the order of 15 to 20 
minutes for all except wide-bodied aircraft. For the latter, the interval is 



4-78 



generally scheduled for 25 to 30 minutes to allow for variations in the processing 
time of the large numbers of passengers involved. Prior to the reduction of 
flights in January due to the energy crisis, the schedules were somewhat tighter, 
with minimums ranging between 10 and 15 minutes. 

Due to physical limitations in the availability of space in the gate areas 
and the general configuration of the lobby and gate equipment installations, a 
number of restrictions in the gate assignment procedures are necessary. These 
restrictions vary in complexity depending on the mix of aircraft types utilized by 
an airline and the number and physical configurations of the gate areas from which 
the airlines operate. Table 4-12 illustrates the considerations that are involved 
in gate planning by American Airlines based on aircraft size. * This tabulation 
pertains to American gates in the H and K ramp areas and indicates the allowable 
gate usage for various types of aircraft, the type of parking required, and the 
type of deplaning/enplaning employed at each gate under the various possible gate 
combination schemes. Similar plans of varying degrees of complexity are also 
in effect for the TWA and UAL gate areas. 

4.3.2.2 Gate Operations 

Management of gate operations and the organization of the units involved 
varies from airline to airline. At AAL, the Marketing Department is responsible 
for gate operations. The Passenger Services Division coordinates such activities 
as passenger processing, jetway operators, and closeup of aircraft. The Ramp 
Service Division is responsible for cargo and baggage loading, fueling, cabin 
servicing, and for providing weight and balance information. The Operations Depart- 
ment is responsible for aircraft maintenance, pushback operations for departing 
aircraft, and the parking of arrival aircraft. 

The Ramp Services Department at TWA is responsible for gate opera- 
tions. The individuals involved are the Manager of Ramp Services, Flight 



*Provided through the cooperation of American Airlines. 



4-79 



Table 4-12. Authorized Aircraft Parking - O'Hare 

Passenger Terminal - American Airlines 



Gate 



Type 
Parking 




H-l 



Guide - 
man 



H-2 



Nose-in 



K-l 



Nose-in 



K-2R 



All 
weather 



K-2 



Nose-in 
Boom/Tgt 



K-2A 



Nose-in 
Boom/Tgt 



K-3 



Nose-in 
Boom/Tgt 



K-5 



Nose-in 
HOLDS 



K-6 



Nose-in 



K-7A 



Nose-in 
Boom/Tgt 



K-7B 



Nose-in 
Boom Tgt 



K-8 



Nose-in 
Boom/Tgt 



K-9 



Nose -in 
Boom Tgt 



K-10 



Nose-in 



K-ll 



Nose-in 
Boom Tgt 



Simultaneous occupancy of K-9, K-ll by DC -10s not preferred if other gates 
available. 

B747 A/C use nose-in precision parking of fixed boom. 

When B747 A/C use K-ll, it is using both K-9 and K-ll facilities, hence is 
considered using one gate, K-ll. 

See explanatory notes on next page. 



4-80 



Table 4-12 NOTES 

1. If K-2A not occupied. 

2. Requires wingman if B747 on K-8. 

3. If K-7B not occupied. 

4. If K-7A not occupied. 

5. If K-9 not occupied by B707 or DC- 10, or, if K-7A not occupied by B707. 

6. If K-ll not occupied by DC-10. 

7. If K-7B not occupied by B727 A/C. 

8. If K-9 not occupied by B727 A/C or B747. 

9. If K-9 not occupied by B747. 
K-9 gate is considered K-ll for B747 use only. Thus K-ll must be vacant. 

11. DC-10 uses all WX parking. 

12. If K-8 not occupied by B747. 

13. Okay, but preferred on another B727 gate if available. 



10 



4-81 



Information Coordination (FIC) and Manager- on- Duty. Upon completion of the 
loading processes and if no prior decision has been made by either the Manager- 
on-Duty or the FIC to hold an aircraft for connection passengers, the engines are 
started and the aircraft is dispatched. The FIC is then notified that the gate is 
ready for reassignment and a new aircraft is then assigned to the vacant gate. 

At UAL, the operating unit responsible for gate operations is the Gate 
Operations Unit. The tower operator has an overview of all three ramp areas 
from which UAL operates and in this capacity he represents the "eyes" of opera- 
tions under normal operating conditions. The tower operator is in radio contact 
with the aircraft and coordinates specific requests between the pilot and various 
operations in the gate area. For example, if an arriving passenger requires a 
wheelchair for deplaning, the tower operator passes on the request from the pilot 
to the appropriate personnel. He provides pushback clearance upon request from 
the pilot, or will delay the clearance if he observes other activity (arrival or de- 
parture) which will interfere with the pushback of that aircraft. 

When gate problems become difficult due to excessive delays in re- 
leasing an aircraft, reassignments are handled by the Operations Agent working 
with Passenger Operations and the Irregularity Operations Message Position 
(located in the Planning Center in the main terminal building). 

A Ramp Operations Supervisor is normally responsible for several 
gates and the operations at that gate and a Passenger Service Supervisor is respon- 
sible for two agents at an active gate. Maintenance Planning is in contact with the 
aircraft mechanic crews. However, Ramp Operations does not have good com- 
munications contact with the mechanics. Consequently, no single individual is 
cognizant of the full status of the aircraft at any given time. 

Since aircraft delays can represent a significant cost element to an 
airline as well as inconvenience to the passengers, a number of steps have been 
taken by the airlines in an attempt to improve the efficiency of their operation by 



4-82 



minimizing controllable delays. AAL, TWA, and UAL have indicated that records 
are kept to indicate both the amount of delay and the causative factors. The most 
common causes of delay are attributed to late equipment arrival and maintenance 
activities as well as passenger services including cargo loading and passenger 
boarding. 

Adherence to departure schedules and aircraft status checks are 
monitored either by means of radio or intercom facilities and by visual observa- 
tion from the ramp control tower at AAL and UAL. If the scheduled departure 
time passes (within a minute or two) and the aircraft is still at the gate, calls are 
normally initiated to Ramp Operations or Passenger Services to determine the 
problem and to ascertain the estimated length of the delay. This is performed 
because any significant delay may have a serious impact on gate availability for 
arriving aircraft. 

Both TWA and UAL indicated that their normal procedures for providing 
gate assignment information to arrival aircraft is some 20 to 30 minutes prior to 
landing. The gate assignment is confirmed once the aircraft has landed. At AAL, 
the normal procedure is to inform the pilot of the gate assignment only after he has 
landed and called in to the ramp control tower. It should be noted that AAL has a 
manned position for Inbound Flight Monitoring which permits the derivation of 
estimated arrival times as well as which runway will be utilized by an arriving 
aircraft. Thus, any difficulties in gate availability can be anticipated and usually 
resolved prior to the aircraft's landing and requesting of a gate number by the pilot. 
All three airlines attempt to provide information as to expected delays or firm 
gates at the initial contact from the aircraft. 

Once the aircraft have landed, the pilots are advised if a gate is tem- 
porarily blocked. Judgment is used in estimating the difference in time between 
the expected availability of the gate and the amount of time required by the aircraft 
in taxiing from the runway to the ramp area. The pilot is advised of this condition 
for use in his communications with the ATCT. 



4-83 



In the event it is necessary to assign a different gate than originally 
scheduled, the impact of aircraft size, type of flight (terminating or through), 
final requirements, interconnection flight status and projected turn-around time 
of the aircraft are all evaluated before a new gate is assigned to ensure a minimum 
disruption to the overall operation. Observations of the activities in the AAL tower 
and UAL Planning Center indicated that rescheduling of gate assignments generally 
involves the need to adjust the schedule for several aircraft at a time. 

4.3.3 Flight Deck (Cockpit) Operations 

The flight deck functions which are directly related to the operations 
of aircraft within and in relation to the ASTC system include: pre-flight checkout, 
company communications, ATC communications, and aircraft movement control. 
Responsibility for the performance of the functions are shared between the flight 
officers. 

On most jet aircraft, including any larger in size than the Boeing 727, 
there are three flight officers; that is, the Captain (Pilot), the First Officer 
(Pilot), and Second Officer (Flight Engineer). In most cases the Flight Engineer 
is also qualified as a pilot. On smaller aircraft there are generally only two 
flight officers, except where union agreements require a third officer. 

The Captain is responsible for all functions performed on the aircraft. 
However, specific tasks are delegated in accordance with standard operating pro- 
cedures or upon specific command by the Captain. Either the Captain or the First 
Officer will fly the aircraft. In cases of multileg flights (i. e. , flying between 
more than just two airports) or where the flight or crew returns to the previous 
departure airport, it is a common practice for the Captain to operate one leg 
and the First Officer to operate the next or return leg. The Second Officer is 
primarily concerned with assuring and maintaining the fitness of aircraft before, 
during, and after flight, and with company radio communications. For the purpose 



4-84 



of the following description of the activities of the flight officers, the discussion 
is presented in terms of the pilot-flying and pilot-not-flying. 

Prior to pushback extensive check-out procedures are performed. 
The check-out requirements and procedures vary with the type of aircraft. How- 
ever, in general they are accomplished by pairs of flight officers with one reading 
off the checklist and the other performing the checks. In aircraft with three 
officers, one set of checks is made by the First Officer and Second Officer and 
another by the two pilots. Following pushback and engine start additional checks 
will be made. Further pre-flight checks may be made during taxi to the runway 
and prior to takeoff, the latter primarily related to engine performance and 
setting of control surfaces. After takeoff another set of checks is made in relation 
to performance, flight settings, and wheels retracted. 

During the arrival phase of flight other checklists are run through 
prior to landing (e.g. , performance, settings, flight control surfaces, wheels 
down and locked), after landing (e.g. , engine settings, flight control surfaces), 
and after docking at the gate (e.g. , engine shutdown, brakes locked, remaining 
fuel). Radio communication is accomplished with the cockpit via two tunable VHF 
radios, both of which can be alternately switched to two pretuned frequencies as 
shown in Figure 4-13. Typically, the pilots operate on Set 1 which is used for 
ATC and navigation purposes, while the Second Officer operates on Set 2 which is 
used for company communications and navigation backup. 

SET I SET 2 



ATC NAV 




Freq. X^ / Freq 
Tune SEL Tune 





CO 




SEL 




NAV 
































Freq. 

• 
Tune 


\ 


/ 


Freq. 

• 
Tune 





Figure 4-13. VHF Radios in Cockpit 



4-85 



A primary exception to this procedure occurs during pushback phase 
at which time the pilot-not-flying communicates with the company on Set 2. Ordi- 
narily, this communication is performed to obtain clearance to push back. How- 
ever, when the scheduled departure time has passed and equipments indicate that 
one or more of the aircraft doors (i.e. , cabin entrance, belly, service) are still 
open, the company may be called to determine what is delaying the departure and 
to obtain a new departure time. Interviews with pilots and observation in the cock- 
pit clearly indicated that the flight officers are normally completely unaware of 
whether or not the flight will depart on schedule, except for those instances where 
the delay is due to equipment failures reported by them. 

In addition to the radio equipment, there is a PA system on board 
which enables the pilot-flying to talk to the ground crew mechanic during push- 
back. It also allows internal communications with the flight attendants and the 
passengers. 

Except for the pushback situation, both pilots will monitor the ATC 
frequency on Set 1 during taxi, takeoff, flight, and landing. The pilot-not-flying 
will acknowledge and initiate all communications transmitted from the aircraft. 
If the pilot-flying wishes to contact ATC, he will generally request the pilot-not- 
flying to do so. 

The Second Officer maintains communications with the company for 
such purposes as gate status information and maintenance coordination during 
flight. As noted in the previous discussion of terminal operations, the company 
may be initially contacted when the aircraft is 20 to 30 minutes from arrival at 
O'Hare. However, during in-flight cockpit observations on UAL flights from 
O'Hare to Newark, it was noted that this contact was not made until later in the 
arrival phase. The reason given by the Second Officers was that, because of the 
interconnection flight planning at O'Hare, substantial information related to con- 
necting flight gates is received at this time for announcement to the passengers. 
Since this situation does not exist at Newark pre-arrival contact was not necessary. 



4-86 



The pilot-flying is responsible for controlling the movements of the 
aircraft during ground taxi, takeoff, landing, and in-flight phases of operation. 
However, during all phases of the flight he may issue commands for actions by the 
pilot-not -flying required to control the movement and request readings of instru- 
ments being observed by the other officers. During ground phases the aircraft is 
normally taxied with the engines at idle power. Steering and forward movement 
is accomplished by the pilot-flying. However, both pilots share responsibilities 
for obtaining visual references external to the cockpit such as traffic conditions, 
lights, markers, signs, and building lines for use in controlling the movement of 
the aircraft and assuring the necessary forward and/or wing-tip clearance to 
other aircraft moving on the taxiways or parked at the terminal. 

During takeoff the pilot-flying normally concentrates his attention on 
maintenance of the runway centerline and controlling the liftoff with the pilot-not- 
flying providing assistance in monitoring the engines and calling out the critical 
speeds. During landing the pilot-flying similarly concentrates his attention on 
maintenance of approach glide path and runway centerline and then on steering of 
the aircraft off the runway. The pilot-not-flying again provides assistance in 
engine/speed control. During the departure (climb and vector), enroute, approach 
(descent and vector) phases both pilots and, where necessary, the Second Officer 
share responsibility for visually locating aircraft for which the flight receives 
traffic advisories. 

During in-flight observations the pilot -not-flying was observed to be 
controlling the throttle settings. In addition, a number of in-flight observations 
were made aboard DC- 10 aircraft, including one landing at Newark under very 
poor visibility (i.e. , early evening and heavy blowing snow conditions) during 
which fully automated landings were made. 

More detailed descriptions of the activities of flight officers are pre- 
sented in Section 5. 5 in relation to the cockpit crew workload analysis. 



4-87 



4.4 AIRPORT MANAGEMENT FUNCTIONS 

4.4.1 General Responsibilities 

O'Hare International Airport is an operating division of the Department 
of Aviation of the City of Chicago. The airport management itself is neither a 
source of aircraft traffic or involved in the direct control of their movements. 
However, it is responsible for the maintenance of major physical components of 
the operating environment (i.e. , runways, taxiways, ramps, lighting, signs). It 
is also a major source of vehicular traffic on the airport surface. Thus, the 
manner in which it discharges its responsibilities does have a significant impact 
on the operations of the ASTC system. 

The overall operation of the airport is divided into four distinct areas 
of responsibilities: administration, aeronautical operations, skilled maintenance, 
and heating and refrigeration systems. These four areas function directly under 
the First Deputy Commissioner/Airport Manager and the Assistant Airport Man- 
ager. In addition, the Chicago Fire and Police Departments perform their re- 
spective functions for the airport on a daily basis and coordinate their activities 
with the Department of Aviation. 

The various functions performed in each of these areas of respon- 
sibility as well as the overall organization chart for the airport operation is shown 
in Figure 4-14. The authorized personnel assignment levels in effect for the 
calendar year 1972 are shown in parentheses for each function. 

The activities shown crosshatched in the figure are those which are 
primarily involved in operations that impact on the movement of aircraft through 
the airport and are the subject of the discussions that follow. 

4.4.2 Airport Personnel Position Descriptions 

The following are descriptions of key positions for both the Department 
of Aviation and the O'Hare Airport. 



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4-89 



Commissioner of Aviation is a highly responsible position in the 
executive branch of City of Chicago government. The person 
holding this position reports directly to the Mayor and the City 
Council. He directs the overall fiscal, operational, and engineer- 
ing activities of three airports as well as his department. He 
negotiates directly or through his representatives with airlines, 
other tenants, and local, state and federal officials in all matters 
relative to the airport. He also provides advice and recommenda- 
tion on all aviation matters that affect the City of Chicago. 

First Deputy Commissioner of Aviation assists the Commissioner 
and acts for him in his absence. He provides executive direction 
on aviation matters relative to the City of Chicago. At the present 
time he is also acting manager of Chicago O'Hare International 
Airport. 

Chief of Aviation Planning is responsible for master planning of all 
airport facilities owned and operated by the City of Chicago. He 
directs preliminary design functions on all airport projects and 
initiates and monitors requests for Federal and State aid. He is 
responsible for reviewing all tenant plans that add to or modify 
existing airport facilities and monitors all tenant construction or 
alterations as they occur. He supervises all phases of engineering 
relative to airport maintenance and renders professional assist- 
ance to the skilled trades personnel as the need arises. He directs 
all surveys and studies directly related to airport facilities. 

Chief of Aviation Operations coordinates all safety practices and 
procedures for the airports owned and operated by the City and 
all heliports licensed by the City of Chicago. He provides recom- 
mendations relative to airport security, emergency procedures 
and custodial maintenance practices and coordinates the acqui- 
sition and applicable use of equipment required by security, emer- 
gency, maintenance, and operation functions at each airport. He 
supervises the inventory control function at each airport and is 
responsible for the maintenance of all traffic and accident records 
and reports. 

Aviation Safety Director assists the Chief of Aviation Operations 
in the performance of his duties. He performs specific functions 
relative to safety practices and procedures, recommendations on 
security, emergency procedures, and custodial maintenance prac- 
tices, acquisition and application of equipment, recommendations 
to improve services, traffic and accident reports, or airport reg- 
ulations as directed. 



4-90 



Airport Manager (O'Hare) , under the direction of the Commis- 
sioner of Aviation, and with staff assistance, advice, guidance 
and functional direction, is responsible for the operation of 
Chicago-O'Hare International Airport. He is primarily responsi- 
ble for (1) regulating all airport users for compliance with appli- 
cable laws and airport regulations, and (2) directing the procedures 
and practices necessary to ensure all facilities are well main- 
tained and in excellent repair. 

Assistant Airport Manager (O'Hare) assists the Airport Manager 
(O'Hare) and acts for him in his absence. Performs those func- 
tions designated by the Airport Manager (O'Hare). 

Airport Operations Supervisor II assists the Assistant Airport 
Manager (O'Hare) in direction and supervision of the functional 
operations and facilities maintenance. He is responsible for the 
physical condition of runways, ramps, and taxiways and coor- 
dinates the inspection and maintenance of airfield and terminal 
facilities. He supervises the operation of the airport security 
section. He maintains information regarding all field conditions 
for airmen, insures that airport tenants adhere to pertinent codes, 
rules, and regulations. He coordinates the work of lower level 
operations and maintenance personnel . 

Airport Operations Supervisor I assists the Airport Operations 
Supervisor II in supervision of the functional operations and facil- 
ities maintenance. He inspects facilities and equipment for needed 
maintenance, alteration, or repair. He issues notices of field 
conditions, maintains condition records for airlines and airport 
referral, and checks work of maintenance crews and lower level 
operational personnel. 

Supervisor of Skilled Maintenance directs and supervises all 
skilled trades except those mechanical trades assigned to the 
heating and refrigeration system. He assists in planning and 
schedules all maintenance work performed by the skilled trades 
he directs and supervises. 

Construction Superintendent assists in the planning and scheduling 
of all maintenance and construction work or projects undertaken 
at O'Hare. He reviews tenant plans for modification of existing 
facilities and monitors all tenant construction or alterations as it 
occurs. He monitors all airport construction projects. 



4-91 



• General Foreman of Motor Truck Drivers is responsible for 
allocating and assigning duties to subordinates in the automotive 
equipment section. He conducts training programs for snow re- 
moval operations and makes recommendations to the Airport 
Operations Supervisor II regarding personnel and equipment needs. 
He directs, supervises, or coordinates all functions that require 
the use or application of equipment or vehicles assigned to the 
automotive equipment section. 

• Foreman of Electrical Mechanics (in Charge) directs, supervises, 
and coordinates the maintenance and repair of all electrical and 
related systems on the airport and makes recommendations to the 
Airport Manager (O'Hare) regarding personnel and equipment 
needs. He is responsible for allocating and assigning duties to 
subordinates in the electrical maintenance section. He assists 

in planning and scheduling construction, modification and main- 
tenance projects that affect electrical and related systems. 

• Lieutenant (Police Detail) directs, supervises, and coordinates all 
police activities and duties at the airport. He acts as liaisonbetween 
the Airport Manager (O'Hare) and the Chicago Police Department 
and makes recommendations to the Airport Manager (O'Hare) re- 
garding personnel and special equipment needs . 

• Division Fire Marshal plans , organizes and directs airport fire 
and crash rescue activities, allocating duties and assigning sub- 
ordinates to specific duties. He establishes crash and rescue 
procedures and techniques and conducts on-the-job training for 
fire and crash rescue personnel. He arranges for and directs the 
inspection of all airport premises from a standpoint of safety and 
fire potential, recommending corrective action where necessary. 
He monitors the operational status of fire fighting and rescue 
vehicles and provides prompt notification of inoperable vehicles 
and he coordinates the assignment of emergency duties. 

4.4.3 Functional Operations Descriptions 

This section of the report provides descriptions of the functional pro- 
cedures employed in the coordination of airport operations within the airport 
organization and between the airport operations and the ATCT. 



4-92 



4. 4. 3. 1 Coordination Center 

O'Hare maintains an Airport Operations Coordination Center to serve 
as the monitoring and coordination arm of the Airport Operations Supervisor (AOS). 
The Coordination Center operates from the former ATCT which is located between 
gates D-3 and D-5 in the ramp area. The Center receives daily status information 
relative to runway and taxiway conditions and any discrepancy reports which neces- 
sitate deviations from normal operating procedures. Such discrepancies are re- 
ported to the AOS who initiates actions to correct them. Typically, any failures 
in the lighting systems and directional signs are reported to Electrical Maintenance, 
while deterioration of runway or taxi surfaces are reported to Construction for 
action. Field condition reports are also issued every two hours during normal 
conditions and every hour during snow conditions. 

Any work activities being performed in operational areas are mon- 
itored to determine status and estimated completion time. The Center directs all 
snow removal operations as well as emergency situation operations and performs 
similar status monitoring functions during these operations. 

The Center is normally manned by two people with a third position 
made active during snow conditions (Snow Desk). The facility is equipped with 
three telephone lines as well as two-way radio equipment for field activities. Two 
channels are currently in use; one is for general field communications and the 
other for operations involving city police, emergency, and snow removal. A third 
channel is being implemented and is expected to be operational by July 1974. This 
channel will permit the separation of snow removal and emergency operations 
from those requiring police coordination. 

4. 4. 3. 1. 1 Coordination Center Interaction with Other Activities 

The Center receives outage reports from the ATCT and, in the case of 
an emergency, is notified immediately after the situation is reported by the ATCT 
to Crash Rescue operations. The Center verifies when an out-of-service runway 



4-93 



or taxiway is ready to be returned to service and notifies the ATCT when normal 
service can be resumed. 

Emergency operations advises the Center whether or not a particular 
incident requires that specific operational areas be closed to further operations. 
This is reported to the AOS who then initiates actions to notify the ATCT of the 
closing. 

Maintenance operations notifies the Center when planned maintenance 
activities are to commence and status of the maintenance progress is monitored. 

Contact with airline operations or other aircraft operators is estab- 
lished by means of telephones when particular problems arise due to their opera- 
tions. 

4.4.3. 1.2 Impact of Visibility Conditions on Center Operations 

The Coordination Center currently maintains moderate visual contact 
with airport operations vehicles. Consequently, visual obstructions between the 
Center and various parts of the airport surface as well as operations during low 
visibility conditions have no significant bearing on vehicle movement and operation. 
Radio contact is maintained with all vehicles or, in the case of a group of vehicles 
engaged in an activity in the same area, with a designated radio-equipped lead 
vehicle. 

4.4.3.2 Snow Removal Operations 

The responsibility for the movement of snow from runway and taxiway 
surfaces and the immediately adjacent areas rests with the Airport Manager and 
is delegated to the AOS. Based on weather forecasts which indicate that an appre- 
ciable accumulation is probable, the Airline Snow Advisory Committee is contacted 
by the Airport Manager or AOS on duty. They jointly determine when snow re- 
moval operations should commence and establish a priority in which the various 
areas are to be cleared. 



4-94 



The ATCT is advised of these decisions by telephone and the appropriate 
runways and taxiways closed down for snow operations. A written NOTAM is also 
issued describing existing conditions. The ATCT is advised as to both estimated 
and actual completion times for these operations which are directed by the Coor- 
dination Center. An information center (Snow Desk) is established to maintain 
regular inspections of the field conditions and to advise on the progress of snow 
removal operations to the airport users. 

The vehicle complement employed in a single snow removal operation 
consists of a lead car and from six to seventeen snow removal vehicles. Per- 
sonnel in the lead vehicle assign positions to each vehicle. These vehicles are 
normally based at the city maintenance yards. 

Vehicle movements are coordinated with the control tower when vehi- 
cles are ready to leave the base area for the designated runways and taxiways as 
well as when moving from one operational area to another or returning to the base 
area. Movements within specified operations areas and within the ramp area are 
not under tower control. The operations are directed from the Snow Desk by 
means of a radio communications channel specifically for this type of operation. 
The lead car has two-way communications equipment while the remaining vehicles 
have only receiving equipment. 

Typical problems encountered in snow removal operations are damage 
to centerline and touchdown zone lights and buried or damaged directional signs or 
edge lights. Existence of such problems is determined by a supervisor who makes 
a physical inspection of the cleared area after operations are completed. 

4.4.3.3 Surface and Equipment Maintenance Operations 

There are approximately one hundred radio equipped maintenance 
vehicles and eight grass cutters with radio equipment available for various main- 
tenance activities at O'Hare. These vehicles are normally based at the automotive 
garage. In addition, contractor vehicles ranging from light pickup trucks to heavy 



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construction equipments may be brought in to facilitate maintenance activities. 
These vehicles must also be equipped with radio equipment or else must have an 
extra vehicle with radio equipment assigned to the same immediate work area. 

Requirements for maintenance of airport surface areas are determined 
on the basis of daily surface condition reports or, in certain circumstances, based 
on notification by airport users of unusual conditions. Maintenance of visual ground 
aids are generally scheduled so as to have a minimum impact on traffic during 
these activities. These activities are not scheduled for Mondays, Fridays, and 
Sunday nights due to the higher traffic levels existing at these times. 

When maintenance operations are scheduled for certain areas of the 
airport which impact on air traffic operations, the ATCT is advised by telephone 
and NOTAM as early as practical and advisories of progress and estimated com- 
pletion times are issued at appropriate intervals. The Coordination Center moni- 
tors progress of the operations while active. For routine maintenance activities, 
the operations are directed by either the electrical maintenance or construction 
sections, depending on the nature of the work being performed. In the case of 
major projects, a Public Works Project Engineer maintains liaison with Opera- 
tions. Operating crews maintain continuing communications with the Coordination 
Center as necessary for progress reporting and verifying that a NOTAM has been 
issued and is still in effect during the particular operation in progress. 

As with the snow removal operations, all maintenance vehicle move- 
ments between the base and the maintenance area, between maintenance areas, 
and from the last maintenance area back to the base area are under ATCT control. 
Movements within a specific maintenance area are not controlled by the ATCT. 
The vehicles are required to travel on designated roads or taxiways and runways 
as necessary. 



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4.4.4 Emergency Operations 

In accordance with Federal Aviation Regulations, Part 139. 55, an 
Emergency Plan for the O'Hare Airport has been published as part of the Airport 
Operations Manual. This Emergency Plan enumerates the specific responsibil- 
ities of the various organizational elements and their employees and provides 
instructions as to the actions that are to be taken in the event of any of the emer- 
gencies identified in the Regulations. This Emergency Plan has been coordinated 
with law enforcement and firefighting and rescue agencies, medical resources, 
principal tenants at the airport, and a number of government and non-government 
organizations that may become involved in the event of an emergency. 

A Central Control Point (CCP) will be established in the Airport Opera- 
tions Office at the direction of the Manager in the event of a major emergency. 
The Airport Manager or his senior representative present will become the Emer- 
gency Control Officer (ECO) and directs the operation of the CCP in cooperation 
with the Senior Fire Officer at the scene. 

The CCP will: 

• Direct and/or coordinate all emergency response activities at the 
airport. 

• Close the airport or runway (s) as appropriate or necessary. 

• Ensure that the various departments and agencies involved have 
been notified and are performing their assigned functions. 

• Relay or initiate requests for additional help or service as needed. 

• Restore airport operations to the maximum extent possible after 
the emergency area is isolated; restore normal operations com- 
pletely as soon as possible. 

• Establish liaison between news media and representatives of de- 
partments or agencies involved in the emergency proceedings. 



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A Check-In Point will be established by the Manager, in the event of a 
major emergency. The operation of the Check-In Point will be the responsibility 
of the Chicago Police Department as directed by the ECO. The purpose of this 
Check-In Point is to: 

• Insure that only authorized persons are admitted to the scene of 
emergency. 

• Assist authorized persons to reach and return from their duty 
posts safely and quickly. 

• Provide (from the Manager, if necessary) vehicles or convoys 
which can receive clearance from the ATCT to move authorized 
persons and equipment to where they are needed safely, quickly, 
and with minimum interference with airport operations. 

An Emergency Communications Center will be established at the 
Central Control Point in the Airport Operations Office. A Mobile Communications 
Center will be located at the scene if the emergency is localized rather than general 
as would be the case in an aircraft incident as opposed to a snow storm. The 
Mobile Communications Center shall be Chicago Police Department patrol car 
"City 13" and/or the 2 5th Battalion Chief's car. The Mobile Communications 
Center shall be directed by the ECO. 

The following paragraphs provide a brief synopsis of the emergency 
procedures followed for aircraft accident and bomb (Suspicious Material Threat) 
incidents. Since the promulgation of the emergency plan and direction of re- 
sponses to incidents is the responsibility of the airport management, the descrip- 
tions include the procedures to be followed by the ATCT and airlines in relation 
to the airport management operations. 

4. 4. 4. 1 Aircraft Accident Emergency Procedures 

In the event of aircraft incidents and accidents within the confines of 
O'Hare Airport, emergency procedures are initiated to alert the appropriate or- 
ganizations and to take action in their specific areas of responsibility. The alert 



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will be initiated by various organizations depending on the nature of the incidents. 
Aircraft accidents on the surface or crashes may usually be first noted or reported 
by pilots to the ATCT. Alerts for airborne aircraft may be initiated by the ATCT 
or airline, whichever is first notified by the crew of the aircraft involved. The 
following outlines some of the more pertinent actions that are to be taken by the 
major elements involved. 

4.4.4.1.1 ATCT 

In the event of emergency situations first noted by or reported to the 
ATCT, the ATCT will first alert the Chicago Fire Department (Airport Battalion) 
and the Air Force Fire Department by use of the emergency drop line phone lo- 
cated in the tower cab. It will: 

1. Advise the type of alarm - ALERT or CRASH- FIRE. 

2. Advise, if it is an ALERT alarm, the runway which the airport 
will use. 

3. Spot the scene of the accident on the airport. If it is a CRASH- 
FIRE alarm, the official grid map of the airport should be used 
in describing the location. 

4. Request confirmation of the information transmitted. 

5. Provide as much pertinent information as is available, and/or 
obtained from the aircraft operator or airline involved: 

Aircraft identification 
Type aircraft 
Nature of emergency 
Quantity of fuel on board 
Runway to be used for landing 
Number of occupants - passenger and crew 
Presence of hazardous cargo or explosives 

The location and, if appropriate, the estimated time of arrival 
of the aircraft. 

6. Establish radio contact, 121.9, with the emergency equipment 
and monitor at all times during an emergency. "Charlie Fox Dog" 



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is used as the call sign for all communication with the Chicago 
Fire Department emergency crew after they have left their station. 
"Air Force Emergency" is used for such communication with the 
Air Force Fire Department. 

After emergency personnel have been notified, the ATCT will then 
alert the Airport Operations Office Coordination Center using the phone located in 
the Tower cab. The Airport Operations Office is responsible for alerting other 
Department of Aviation personnel. Following this the ATCT will notify the air- 
craft operator or the airline involved by calling the appropriate flight dispatch 
office. Subsequently the ATCT will direct other air and ground traffic so as to 
avoid conflicts in the area of the emergency. 

4. 4. 4. 1. 2 Chicago Fire Department (Airport Battalion) 

The Fire Department will alert the ATCT if the ALERT was not re- 
ported by the ATCT. It responds to all emergency alerts on the airport. This 
includes: 

1. Emergency Alert - upon being advised of this type of alarm , the 
emergency equipment proceeds directly to the scene by the most 
direct route. 

2. Standby Alert - upon being advised of this type of alarm, the emer- 
gency equipment will take the standby positions for the runway to 
be used as prescribed by Headquarters, Chicago Fire Department 
directive dated June 12, 1972. 

Fire Department leadership and operating vehicles will coordinate 
with ATCT Ground Control by means of two-way radio (121. 9). "Charlie Fox 
Dog" will be used in all radio communications. The Department will assume 
primary responsibility at the immediate scene of any incident involving a civilian 
aircraft. (The Air Force Fire Department Chief will be in command if a military 
aircraft is involved. ) It will perform the following functions: 

1. Direct and control rescue and firefighting activities during the 
period of actual emergency. 



4-100 



2. Determine need for and request ambulance service and medical 
assistance as required. 

3. Request additional firefighting and rescue or other equipment as 
needed. 

4. Support the Chicago Police Department as needed in incidents for 
which they have responsibilities. 

5. Confer with Tower and Emergency Control Officer regarding 
status of emergency, as appropriate. 

6. Provide Battalion Chief's Car as a mobile communication center 
if required. 

Off-Airport fire department emergency equipment responding to an 
emergency will be met by vehicles equipped with proper radios and will be escorted 
to the scene. 

4.4.4.1.3 Airport Management 

Upon notification of a major emergency situation the airport manage- 
ment will establish and operate the Central Control Point as previously described. 
The following functions will then be performed: 

1. Notify the following of the location and nature of the emergency: 

OED Control Tower if the alert was not given by the Tower 
Chicago Police Department (Airport Division) 
Commissioner of Aviation 
Aviation Safety Director 

Airport Manager and other airport operations personnel as 
appropriate. 

2. Dispatch the AOS to the scene and maintain overall control. 

3. Secure and arrange for other City services as required. 

4. Maintain a log of the emergency and any resulting actions at the 
duty desk at the CCP. 



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4. 4. 4. 1.4 Chicago Police Department (Airport Division) 

The Police Department responds to all emergencies on the airport 
with Police Squad Car, "City 13", which will take a position with the Chicago 
Fire Department equipment. This unit will function as a mobile communication 
center for all ALERT and CRASH- FIRE emergencies. 

The Police Department will perform the following functions: 

1. Notify and coordinate all emergency activities with the Airport 
Manager or Airport Operations Supervisor on duty. 

2. Control crowd and traffic in the vicinity of the accident and lead- 
in roads to the airport. The highest ranking officer of the Chicago 
Police Department at the scene will be in charge. 

3. Assist the movement of emergency vehicles and authorized per- 
sons to and from the crash or emergency site. 

4. Secure the scene of the emergency from spectators and others not 
authorized to be there. 

5. Establish and operate the Check-In Point to control the movement 
of people and equipment needed at the scene. 

6. Provide temporary security for wreckage or any other property 
at an incident scene pending assumption of responsibilities by 
properly identified owner or other investigative agencies. 

7. Request and coordinate the activities of other law enforcement 
agencies as needed. 

8 . Consult with the Emergency Control Officer regarding termination 
of the emergency. 

Off-Airport Police Department emergency equipment responding to an 
emergency on the airport will be met by vehicles equipped with proper radios 
and will be escorted to the scene. 



4-102 



4. 4. 4. 1. 5 Airlines and Other Aircraft Operators 

The individual airlines and operators are responsible for establishing 
their own emergency procedures in accordance with the O'Hare Emergency Opera- 
tions Manual. 

In the event that the airline /aire raft is first notified of the emergency 
situation it will alert the ATCT giving the following essential information: 

1. Type of aircraft 

2. Amount of fuel on board in gallons 

3. Number of lives on board 

4. Any unusual cargo on board, such as explosives, nuclear materials, 
etc. 

5. Pilot intentions 

The airline/aircraft operator will then perform the following functions: 

1. Provide manpower and equipment for towing or other support as 
needed in incidents involving aircraft. 

2. Provide for unloading, transportation, and accommodation of pas- 
sengers, baggage, and cargo (including cattle and animals). 

3. Notify the National Transportation Safety Board (NTSB). 

4. Assure that only authorized personnel and equipments are sent to 
the scene of the incident. Each airline and operator will be re- 
sponsible for securing and issuing identification (arm bands or 
other) to their personnel. Personnel proceeding to the scene will 
use service roads and taxiways wherever possible. 

5. Provide for security and removal of equipment or wreckage upon 
termination of emergency and upon clearance from appropriate 
authorities. 



4-103 



4.4.4.1.6 Chicago Board of Health 

The Chicago Board of Health is responsible for the coordination of all 
emergency medical services. In cooperation with the Chicago Fire Department 
and the Chicago Civil Defense Agency, it will mobilize a staff of physicians and 
nurses, with medical supplies, and arrange for hospitalization to care for victims 
requiring such treatment. 

4.4.4.2 Bomb Incident Emergency Procedures 

In the event bomb threats to aircraft are received, the ATCT or Air- 
line immediately alerts the Fire Department. The ATCT then designates the 
search area to be used based on traffic patterns in effect at the time the informa- 
tion is received. The aircraft is moved at once to the designated area which can 
be one of the following: 

1. Warmup pad adjacent to Runway 32 L 

2 . Warmup pad and ramp between Runway 32R and the old Military 
Alert Hangars 

3. Warmup pad adjacent to Runway 9L, especially for wide-bodied 
aircraft, if possible 

4. Involved airline hangar area 

5. Involved airline cargo area 

Unlike the situation involving an aircraft accident, the vehicular 
activity in this case will be significantly less and can generally be expected to be 
confined to police, fire, and security departments stationed at the airport whose 
drivers are familiar with the airport ground traffic procedures to reach the desig- 
nated areas. 

4. 4. 4. 3 Other Emergency Procedures 

In the event of other emergencies such as structural fires, natural 
disasters, sabotage and radiological incidents, the degree of activity on the airport 



4-104 



surface and the extent of the affected areas can vary from a rather localized to a 
very complex and widespread level of effort. As with the previously described 
situations, vehicles will be required to have radio communications capability with 
the tower and varying degrees of control by tower personnel are needed to insure 
maximum operational capability during the particular event. 



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