NASA/TM–2010-216026

Preliminary Human-in-the-Loop Assessment of 

Procedures for Very-Closely-Spaced Parallel Runways 

Savita Verma, Sandra C. Lozito, and Deborah S. Ballinger

Ames Research Center, Moffett Field, California

Greg Trot

Raytheon Company, Marlborough, Massachusetts

Gordon H. Hardy, Ramesh C. Panda, and Ronald D. Lehmer

Science Application International Corporation (SAIC) 

Ames Research Center, Moffett Field, California

Thomas E. Kozon

Perot Systems

Ames Research Center, Moffett Field, California

April 2010
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NASA/TM–2010-216026

Preliminary Human-in-the-Loop Assessment of 

Procedures for Very-Closely-Spaced Parallel Runways 

Savita Verma, Sandra C. Lozito, and Deborah S. Ballinger

Ames Research Center, Moffett Field, California

Greg Trot

Raytheon Company, Marlborough, Massachusetts

Gordon H. Hardy, Ramesh C. Panda, and Ronald D. Lehmer

Science Application International Corporation (SAIC)

Ames Research Center, Moffett Field, California

Thomas E. Kozon

Perot Systems

Ames Research Center, Moffett Field, California

April 2010

National Aeronautics and

Space Administration

Ames Research Center

Moffett Field, California 94035-1000
Available from:

NASA Center for AeroSpace Information National Technical Information Service

7115 Standard Drive 5285 Port Royal Road

Hanover, MD 21076-1320 Springfield, VA 22161

(301) 621-0390 (703) 487-4650

Acknowledgments

Funded by NASA’s ARMD, Airspace Systems Program, NextGen-Airportal Project.

Team members: Savita Verma, Sandra Lozito, Deborah Ballinger, Greg Trot, Gordon Hardy, Ramesh 

Panda, Diane Carpenter, Ronald Lehmer, Thomas Kozon.
iii

TABLE OF CONTENTS 

NOMENCLATURE ............................................................................................................................. v

INTRODUCTION ................................................................................................................................ 1

BACKGROUND .................................................................................................................................. 1

HUMAN-IN-THE-LOOP EXPERIMENT .......................................................................................... 4

Objectives and Hypotheses ............................................................................................................... 4

Approach ........................................................................................................................................... 4

Test Facility .................................................................................................................................. 4

Airport and Airspace Design ........................................................................................................ 5

TACEC Procedures....................................................................................................................... 5

Arrival Traffic Flow...................................................................................................................... 5

Traffic Scenario ............................................................................................................................ 7

Cockpit Display of Traffic and Wake Information ....................................................................... 7

Experimental Matrix and Independent Variables ............................................................................. 9

Dependent Variables ......................................................................................................................... 9

Participants...................................................................................................................................... 10

Test Scenarios ................................................................................................................................. 10

Protocol ........................................................................................................................................... 10

Tools Used for Data Collection ...................................................................................................... 10

RESULTS ........................................................................................................................................... 11

Post-Interaction Survey................................................................................................................... 11

Feature Comparison ........................................................................................................................ 13

Situational Awareness..................................................................................................................... 14

Observer Notes and Group Discussions ......................................................................................... 16

CONCLUSIONS ................................................................................................................................ 16

FUTURE WORK ................................................................................................................................ 17

REFERENCES ................................................................................................................................... 18

APPENDICES .................................................................................................................................... 19

Appendix A – Schedule and Test Matrix for March 27–29, 2007 ................................................. 19

Appendix B – Demographic Survey ............................................................................................... 20

Appendix C – Post-Interaction Survey ........................................................................................... 21

Appendix D – Feature Comparison Survey .................................................................................... 23

Appendix E – Observer Form ......................................................................................................... 24

Appendix F – List of Questions for Group Discussion .................................................................. 26

Appendix G – Layout and Design of SRT Airport ......................................................................... 27
iv

LIST OF FIGURES 

Figure 1. Wake-safe zone for following aircraft. ............................................................................... 3 

Figure 2. SRT airport diagram. .......................................................................................................... 5 

Figure 3. Final approach geometry for TACEC. ................................................................................ 6 

Figure 4. Primary flight display on straight-in parallel final. ............................................................. 7 

Figure 5. Navigation display on straight-in parallel final. ................................................................. 8 

Figure 6. Ratings (mean and Standard Error (SE)) for ease of deriving information 

from the displays. .............................................................................................................. 12 

Figure 7. Pilots’ subjective ratings (mean and SE) on statements regarding the 

concept and displays. ........................................................................................................ 13 

Figure 8. SA responses for 10- vs. 5-sec distance between the two aircraft. ................................... 14 

Figure 9. SA responses for aircraft on straight-in vs. slewed approach. .......................................... 15 

Figure 10. SA responses on clear day vs. Category IIIB visibility. .................................................... 15 

Figure G-1. Current DFW Airport layout. .......................................................................................... 27 

Figure G-2. SRT Airport layout. ......................................................................................................... 27 

LIST OF TABLES 

Table 1. Matrix where the Distance Between the Lead and Trailing Aircraft is 10 sec ................. 9

Table 2. Distance between the lead and trailing aircraft is 5 sec .................................................... 9

Table G-1. SRT Runway Positions .................................................................................................... 28

Table G-2. Runway Configurations by Procedure ............................................................................ 28

Table G-3. Runway Configurations by Operation (A = Arrival, D = Departure) ............................ 28
v

NOMENCLATURE 

4-D four-dimensional 

ACFS Advanced Cockpit Flight Simulator 

ADS-B Automatic Dependent Surveillance–Broadcast 

AGL above ground level 

AILS Airborne Information for Lateral Separation 

ATL Hartsfield-Atlanta International Airport 

BOS Boston/General Edward Lawrence Logan International Airport 

cg center of gravity 

CDTI cockpit displays of traffic information 

C-LNAV Coupled Lateral Navigation 

C-SPD Coupled Speed 

C-VNAV Coupled Vertical Navigation 

CVSRF Crew Vehicle Systems Research Facility 

DEN Denver International Airport 

DFW Dallas Fort Worth International Airport 

EICAS Engine Indicating and Crew Alerting System 

FAA Federal Aviation Administration 

FMS flight management system 

GPS Global Positioning System 

ILS instrument landing system 

JAL Japan Airlines 

JFK John F. Kennedy International Airport 

KSRT fictitious airport used for the simulation; based on current DFW layout and operations 

LAX Los Angeles International Airport 

LSI longitudinal situation indicator 

ND navigation display 

nmi nautical miles 

NTZ no-transgression zone 

ORD O’Hare International Airport 

PFD primary flight display 
vi

NOMENCLATURE (cont.) 

PRM Precision Runway Monitor 

RVR runway range visual 

SA situation awareness 

SART Situational Awareness Rating Technique 

SEA Sea-Tac Airport 

SFO San Francisco International Airport 

SIDs standard instrument departures 

SOIA Simultaneous Offset Instrument Approaches 

SRT airport used for the experiment 

STARs Standard Terminal Arrival 

TACEC Terminal Area Capacity Enhancing Concept 

VAST Virtual Airspace Simulation Technologies 

VCSPR very-closely-spaced parallel runway 

VFR visual flight rules 

VMC visual meteorological conditions 
1

PRELIMINARY HUMAN-IN-THE-LOOP ASSESSMENT OF PROCEDURES 

FOR VERY-CLOSELY-SPACED PARALLEL RUNWAYS 

Savita Verma,1 Sandra C. Lozito,1 Deborah S. Ballinger,1 Greg Trot,2 Gordon H. Hardy,3 

Ramesh C. Panda,3 Ronald D. Lehmer,3 and Thomas E. Kozon4

Ames Research Center

INTRODUCTION 

Demand in the future air-transportation-system concept is expected to double or triple by 2025 

(ref. 1). Increasing airport arrival rates will help meet the growing demand that could be met with 

additional runways, but the expansion airports are met with environmental challenges for the surrounding communities when using current standards and procedures. Therefore, changes to airport 

operations can improve airport capacity without adding runways. 

Building additional runways between current ones, or moving them closer, is a potential solution 

to meeting the increasing demand, as addressed by the Terminal Area Capacity Enhancing Concept (TACEC). TACEC requires robust technologies and procedures that need to be tested such 

that operations are not compromised under instrument meteorological conditions. The reduction of 

runway spacing for independent simultaneous operations dramatically exacerbates the criticality of 

wake vortex incursion and the calculation of a safe and proper breakout maneuver. 

The study presented here developed guidelines for such operations by performing a real-time, 

human-in-the-loop simulation using precision navigation, autopilot-flown approaches, with the 

pilot monitoring aircraft spacing and the wake vortex safe zone during the approach. 

BACKGROUND 

The Federal Aviation Administration (FAA) has successfully conducted independent approaches 

to parallel runways for over 40 years using the instrument-landing-system (ILS) navigation and 

terminal radar monitoring (ref. 2). The simultaneous approaches that utilize standard radar are 

conducted on parallel runways that are separated by at least 4300 ft. It is possible to conduct independent approaches on runways separated by as little as 3000 ft, but it requires a Precision Runway Monitor (PRM) with an update rate of 1 sec. The separation standards between the aircraft on 

 

1

 Ames Research Center, Moffett Field, CA, 94035-0001. 2

 Raytheon Company, Marlborough, MA 01752. 

3

 Science Application International Corporation (SAIC), Ames Research Center, Moffett Field, CA 94035-0001. 4

 Perot Systems, Ames Research Center, Moffett Field, CA 94035-0001. 
2

these parallel approaches are 1000-ft vertical separation. Additionally, a 2000-ft-wide “notransgression zone” (NTZ) was placed equidistant from the centerlines of the approach paths on 

the two parallel runways. Some airports, like San Francisco International Airport (SFO), can support approximately 60 landings per hour on its two parallel runways that are 750 ft apart by using 

simultaneous offset instrument approaches (SOIA) (ref. 3). SOIA approaches require the trailing 

aircraft in the paired approach to obtain a visual sighting of the lead aircraft with at least a 1200-ft 

ceiling with 4-nmi visibility. As weather degrades, the current navigation and surveillance system, 

as well as the existing procedures, lack the accuracy to support SOIA approaches, reducing the 

landing rate to half the visual-flight-rules (VFR) capacity. 

Several researchers have investigated alternative procedures for very-closely-spaced parallel runway (VSCPR) operations. Studies have focused on the technologies required to enable the VCSPR 

operations. Several different requirements have been identified from these studies, such as cockpit 

displays, collision-prevention systems, and precision navigation, communication, and surveillance 

systems (refs. 6, 7, and 8). Another critical component that is necessary for the safe execution of 

VSCPR procedures is the ability to predict the wake vortices for the aircraft nearby and provide 

wake information to the affected aircraft. 

Previous research has also evaluated procedures for VCSPR approaches, but most of them have 

used fast-time simulation to investigate the performance of the procedures. Pritchett & Landry 

(ref. 6) identified the various parameters related to VCSPR operations, such as separation responsibility and different separation and spacing objectives between the paired aircraft. 

Few human-in-the-loop studies have been conducted for VCSPR operations. A study to investigate 

pilot response to VCSPR operations for the Airborne Information for Lateral Separation (AILS) 

concept is one such example. NASA developed the AILS concept to further examine independent 

parallel runway operations for runways as close as 2500 ft. The concept requires technologies that 

enable the use of precise navigation and surveillance data. Automation is presumed to detect 

blunders or situations that may require the aircraft to perform a breakout maneuver (ref. 4). 

The AILS experiment was designed to study three variables: 1) intruder geometry, 2) runway separation (3400 or 2500 ft), and 3) flight control mode (autopilot versus manual prior to the warning 

for breakout). The dependent variables were pilot reaction time and miss-distance in off-nominal 

situations that required the pilot to perform an escape maneuver. The study found that pilot reaction time to detect and perform breakout maneuvers was not affected by runway separation. Across 

all conditions the average pilot reaction time was 1.11 sec, with a standard deviation of 0.45 sec. 

The experiment found a statistically significant effect for the flight control mode, with autopilot 

use prior to the emergency escape maneuver leading to longer reaction times. The current study is 

different from the AILS experiment because it considers wake, and dynamically generates breakout maneuver. 

TACEC aims to fly paired approaches on runways that are 750 ft apart in instrument meteorological conditions (ref. 5). A ground-based processor will identify aircraft that could be paired 

approximately 30 minutes from the terminal boundary. The aircraft are selected for pairing based 

on several parameters, such as aircraft performance, arrival direction, relative timing criteria, and 

aircraft size-of-wake considerations. The ground-based processor then assigns four-dimensional 
3

(4-D) trajectories to the aircraft in the pair. It is assumed that all aircraft will use differential 

Global Positioning System (GPS)-enabled and high-precision 4-D flight-management-system 

(FMS) capabilities for the execution of these trajectories. Enhanced cockpit displays that depict 

both traffic and wake information will also be a requirement for these operations. These operations 

guarantee a wake-free region by positioning a following aircraft sufficiently close to the lead aircraft on the parallel approach so that the vortex does not have time to spread into the path of the 

following aircraft (fig. 1). When the paired aircraft reach 12 nmi from the airport, their autopilot 

systems become “coupled” via a longitudinal spacing control mode. In this mode, a speed-control 

algorithm on the following aircraft uses state data broadcast by the lead aircraft to precisely maintain the separation between the two aircraft until touchdown. 

The TACEC concept envisions nearly completely automated approaches and landings. Advanced 

4-D-capable FMSs execute the assigned 4-D trajectories, and an integrated coupling system maintains safe spacing between the paired aircraft during the final 12 nmi of flight. The pilot is responsible for approving the engagement of coupling and monitoring safe progress using cockpit displays of traffic information (CDTIs) that include display of predicted wake location, alerts for 

wake hazards, display of ownership and traffic assigned trajectories, and indication of navigation 

performance relative to assigned trajectories. 

Little data exist regarding the use of VCSPR technologies and procedures. The objective of the 

current study was to develop guidelines for the procedures defined by the TACEC using a humanin-the-loop simulation study. Thus the objective of this simulation also included exploring the usefulness and usability of the cockpit displays and procedures associated with this new concept. 

Figure 1. Wake-safe zone for following aircraft. 
4

HUMAN-IN-THE-LOOP EXPERIMENT 

Objectives and Hypotheses 

The objective of the study was to assess and develop preliminary guidelines for the procedures for 

the Terminal Area Capacity Enhancing Concept (TACEC) by performing a real-time, human-inthe-loop simulation to conduct human-factors studies of prototype displays and to investigate 

procedures. This process accelerates development of a far-future (2025) concept through early 

implementation. The effort required development of a simulated airport with parallel runways 

750 ft apart, and designing the airspace around this generic airport to facilitate very-closely-spaced 

parallel runway (VCSPR) approaches. The concept was implemented in the Advanced Cockpit 

Flight Simulator (ACFS) by integrating displays that depict wake and traffic information. The 

participants of the study flew the simulator under various conditions and provided feedback on 

changes in roles and responsibilities, new procedures, and their opinions about the concept. The 

report describes all aspects of the study, starting with the approach. 

Appendices A through D give pilot schedule, demographic, and survey information, appendix E 

gives observer feedback, appendix F lists questions for group discussion, and appendix G discusses the layout of the airport used in the study. 

Approach 

Test Facility 

The human-in-the-loop study conducted to assess the paired TACEC approaches used the ACFS, a 

full-mission simulator that resides in the Crew Vehicle Systems Research Facility (CVSRF). The 

ACFS simulates a generic commercial transport aircraft, and it can be reconfigured to represent 

future aircraft. Currently, the ACFS can simulate two aerodynamic aircraft models, narrow-body 

transport aircraft (similar to a Boeing 757) and a C-17 transport. The simulator, as it stands, 

includes fly-by-wire flight controls, touch controls, touch-sensitive electronic checklists, schematics of aircraft systems, a customizable FMS, and graphical flight displays. The cab is mounted on a 

six-degree-of-freedom synergistic motion system and uses side stick controllers for aircraft control 

in the pitch and roll axes. The simulator is run from Silicon Graphics, Inc, (SGI) computers, which 

provide the simulator flight systems and programmable flight displays. In this study, the CDTI 

described in the “Background” section was integrated with the flight-display systems in the cockpit. The ACFS motion capabilities were also used for the study. 

The visual systems in the ACFS offer a 180-degree horizontal and a 40-degree vertical field of 

view. The ACFS visual databases can depict as many as nine airports (SFO, Los Angeles International Airport (LAX), John F. Kennedy International Airport (JFK), Denver International Airport 

(DEN), Dallas Fort Worth International Airport (DFW), Sea-Tac Airport (SEA), HartsfieldAtlanta International Airport (ATL), O’Hare International Airport (ORD), and Boston/General 

Edward Lawrence Logan International Airport (BOS). For the VCSPR study, the SRT airport 

visual database was created, which is a modification of the DFW airport, as described in appendix 

G on the DFW layout. 
5

Airport and Airspace Design 

The airport and airspace used to investigate procedures for the TACEC concept used a fictitious 

airport that was based on the current DFW’s layout and operations. The airport used for the simulation was referred to as “KSRT.” The simulation focused on studying TACEC approaches to very 

closely spaced parallel runways. Since a south air traffic flow was used for the simulation scenarios, the SRT airport utilized only runways 18R, 18L, 17R, and 17C (renamed to 17L). All four 

runways were assumed to be equipped to a Category IIIB (CAT-IIIB) level. Both 18R and 17L 

(see figure 2) were moved to within 750 ft of their inboard runways, 18L and 17R, respectively, 

requiring an adjustment of 464 ft from their current DFW positions. The layout of the DFW is 

described in detail in appendix G. 

TACEC Procedures 

The TACEC concept calls for TACEC-assigned 4-D arrival trajectories for both of the aircraft to 

be paired at meter fixes located near the edge of the terminal airspace, normally 40–60 nmi from 

the airport (ref. 5). Flights in the simulation began 25 nmi from the airport, assuming they were 

already paired. Routes to the KSRT airport included approach and departure routes and procedures 

similar to those for DFW airport. This study focused upon arrivals; no departures were included. 

Arrival Traffic Flow 

South flow of traffic was simulated for the generic airport KSRT. All of the four runways (18R, 

18L, 17R, 17L) were used for arrival operations. The concept allows for any aircraft arriving from 

any of the four arrival meter fixes (NE, NW, SE, and SW) to be paired for a simultaneous parallel 

landing, based on aircraft characteristics and relative timing criteria. 

Figure 2. SRT airport diagram. 
6

Paired aircraft must fly their assigned 4-D trajectories with a high level of accuracy in order to 

meet timing constraints at the coupling point and ensure wake safety throughout the approach. The 

4-D trajectories were carefully designed to provide safe wake-avoiding routes from the arrival 

meter fixes to the runways. Each route consisted of three segments, and each one of the first segments provided vortex-free 4-D routes extending from the meter fix to the coupling point at 12 nmi 

from the runway. The second segment began at the coupling point and ended 2 nmi from the runway. During the second segment, one route was straight in, aligned with the runway centerline, 

while the other was at a 6-degree slew angle from the straight-in route (see fig. 3). At the coupling 

point, the aircraft were laterally separated by slightly more than 1 nmi. Each of the final segments 

was aligned with the runway centerlines, extended 2 nmi from the runway threshold, and was 

about 600 ft above ground level (AGL) in order to provide a straight-in flight path to touchdown. 

Once the aircraft reached the coupling point, the following aircraft precisely maintained spacing 

behind the lead aircraft in order to avoid the wake of the lead aircraft. This operation was accomplished by an automated speed-control algorithm on board the following aircraft that maintained 

the assigned time-based spacing relative to the lead based on state information broadcasted via 

Automatic Dependent Surveillance – Broadcast (ADS-B) by the lead aircraft. Figure 3 shows the 

geometry of the final approach portion of the arrivals (i.e., the final 12 nmi before landing. 

Figure 3. Final approach geometry for TACEC. 

Coupling 

Point 
7

Traffic Scenario 

The traffic scenario had two aircraft in the simulation: the following aircraft in the pair, as 

represented by the ACFS, and the lead aircraft, which was recorded or scripted for this study. The 

ownship was always the following aircraft, and the recorded one was always the leader aircraft in 

the closely spaced parallel runway approach. The leader aircraft was a Boeing 747 heavy aircraft 

representing Japan Airlines (JAL). Based on the wind condition, the ownship was either on the 

slewed approach landing on runway 18R or on the straight-in approach landing on runway 18L. 

Cockpit Display of Traffic and Wake Information 

The primary purpose of the displays used for the TACEC evaluation was to provide the flight 

crews with information to ensure that adequate separation was being maintained with the lead aircraft and its hazardous wake area. While not evaluated in the present simulation, the displays also 

provide “breakout” annunciation and guidance if adequate separation is not maintained with the 

lead aircraft or its wake. The primary flight display (PFD) and the navigation display (ND) are 

modifications of standard current-generation transport flight displays with added lead-aircraft 

position and wake information. Figure 4 shows the PFD on the straight-in parallel final at 532-ft 

radar altitude, while figure 5 shows the ND for the same location. Lateral spacing of the flight 

paths at this part of the approach was 750 ft. The displays are adaptations of those previously 

developed by Hardy and Lewis (ref. 8). 

Lead-Aircraft Position 

The position of the simulator was shown on the ND with the conventional triangular icon (solid) at 

the lower center of the ND. The lead-aircraft position was shown with the open icon at the upper 

left of the ND. The triangular lead aircraft with the same perspective was shown on the PFD at the 

left of the display. With augmented GPS navigation, it was assumed that position information was 

known, with ADS-B to be within a few ft. 

Figure 4. Primary flight display on straight-in parallel final. 
8

Figure 5. Navigation display on straight-in parallel final. 

Hazardous-Wake-Area Depiction 

The shaded white area on the ND and the wake frames on the PFD depict the hazardous wake area. 

This area was defined as that volume of airspace such that if the apex or center of gravity (cg) of 

the following aircraft (simulator) remains outside the wake area, no noticeable wake activity would 

be detected. This area was predicted in real time from aircraft characteristics and onboard sensors 

of crosswind and atmospheric turbulence. The prediction algorithms were conservative to account 

for model and sensor errors (ref. 9). The shaded area on the ND and the wake frames on the PFD 

turn amber if the cg of the following aircraft moves to within one wingspan of the hazardous area, 

and they turn red if its cg penetrates it. 

Predictor Dots 

Five 2-second predictor dots, for a total of 10 seconds, were added to the ND for both aircraft (see 

slightly to the right of the nominal path for the simulator in fig. 5) and also were presented on the 

PFD (aligned with the position icon of the lead aircraft). These dots show flight path trend information to help the pilot determine the future location of the aircraft. 

Longitudinal Situation Indicator 

To maintain the position of the aircraft in the “safe” zone, as shown in figure 4, a longitudinal situation indicator (LSI) was added. The LSI is flagged on the ND and shows the nominal location (in 

this case 5 seconds behind the lead aircraft) that the auto-throttle is attempting to keep. For this 

example, the simulator is approximately 400 ft behind its nominal location. The same LSI information is shown on the deviation scale added on the left side of the PFD (fig. 4). 

Display Scaling 

A conventional PFD has a field of view of about 40 deg. To be able to see the lead aircraft position 

and wake information, this field was increased to 80 deg. This increase decreases the resolution of 

the display, but with future larger display hardware it may not be objectionable. A conventional 
9

ND has a maximum zoom-in capability of a 10-mi. range scale. To have adequate resolution for 

this task, the maximum zoom-in range scale is 0.25 nmi. The display zoomed in increments of 

10-, 5-, 2-, 1-, and 0.5-nmi scales. 

Experimental Matrix and Independent Variables 

The three variables examined in the study were visibility conditions, direction of the wind, and the 

distance between the lead and follower aircraft. The visibility conditions were a clear day, or Category IIIB. The study aimed at exploring an adverse cross wind on the follower (ownship), thus the 

direction of winds was coupled with the follower (ownship) landing on the left or right runway 

(18L or 18R runways in this study), as shown in figure 5. The approach to runway 18R is referred 

to as the slewed approach, and the one to 18L is the straight-in approach. The third variable 

examined in the study was the distance between the lead and follower aircraft at initialization 

points, which was either 10 or 5 sec. The matrix for the study is shown in table 1, where the gap 

between the lead and trailing aircraft was 10 sec, and table 2, where the gap between the lead and 

trailing aircraft was 5 sec. In addition, an additional run led to the consideration of a potential 

escape maneuver due to the location of the wake and traffic. This situation was observed by the 

pilots for purposes of preliminary discussion, and the identification of procedures for off-nominal 

situations. 

Dependent Variables 

The dependent variables collected during the study included subjective data on situation awareness, comparison of features provided by the displays, and other subjective questions asked about 

the usefulness and usability of the displays in a post-interaction survey. 

TABLE 1. MATRIX WHERE THE DISTANCE BETWEEN THE LEAD AND TRAILING AIRCRAFT 

IS 10 SEC 

Straight Approach (18L) Slewed Approach (18R) 

Clear day Run 1 Run 4 

Low visibility (Category-III b) Run 2 Run 3 

TABLE 2. DISTANCE BETWEEN THE LEAD AND TRAILING AIRCRAFT IS 5 SEC 

Straight Approach (18L) Slewed Approach (18R) 

Clear day Run 5 Run 6 

Low visibility (Category-III b) Run 8 Run 7 
10

Participants 

The participants of the study were three retired pilots from commercial airlines; all of them had 

experience with glass cockpits and some experience flying SOIA approaches in San Francisco. 

Their mean age was 65 years, and their mean total years of experience as a pilot was about 40 

years. They had an average about 16,500 hours of flying. Their average number of years since 

retirement was 6.5 years. 

Test Scenarios 

The study was run for three days, with one pilot participating each day. At the beginning of the 

day, the pilot was familiarized with the project, the concept, and the new displays in the cockpit. 

Next, the pilot was taken to the ACFS, where the pilot received a demonstration of the simulator, 

and more hands-on training on the CDTI and related procedures. The schedule for the study is 

included in appendix A. The schedule included the eight runs specified earlier (see tables 1 and 2 

and appendix A) and an off-nominal escape maneuver run mentioned in the “Observer Notes and 

discussion” section. 

Protocol 

The procedures for VCSPR were being explored in this study, so each pilot flew the ACFS as a 

captain. The role of the pilot, in general, was to fly in autopilot mode, and monitor the displays to 

check separation with the lead aircraft and wake. At the coupling point the pilots heard a chime, 

saw the acknowledgement button light up, and a message on the lower Engine Indicating and Crew 

Alerting System (EICAS) appeared that read “TACEC Coupling.” At this point the pilots pressed 

the acknowledgement button, and continued to monitor the separation between the two aircraft. 

The traffic scenario in the next section describes the tow aircraft that were simulated for the study. 

Tools Used for Data Collection 

Several tools were used for collecting subjective data from the pilots. All participants completed a 

demographic survey before the simulation runs were conducted. It collected information about the 

pilots such as their age, experience as a pilot, and number of hours flying different aircraft types, 

any experience with SOIA, and experience using personal computers. 

Each pilot was asked to complete a Post Interaction Survey at the end of all the runs. It collected 

information on the pilot-rated usefulness and usability of the displays. Similarly, a feature comparison survey was administered at the end of all of the runs. The pilots had the opportunity to rate 

the importance of different features in the displays on a scale of 1 to 5, where 1 was equivalent to 

“very unimportant” and 5 was equivalent to “very important.” 
11

Pilots also completed the Situational Awareness Rating Technique (SART) (ref. 10). The SART 

gathers a participant’s rating of his/her situational awareness (SA) for the preceding period of time 

on 10 different scales. Each scale has 7 points, with the end points representing the opposite ends 

of the construct. Participants circled the point on the scale that most closely represented their 

experienced level of SA. The 10 SART ratings were gathered from every participant at the end of 

each run—a total of 8 ratings per participant were collected. 

RESULTS 

This section reports results that focus on the data captured by the tools mentioned in the above 

paragraph . Results of the post-interaction survey, feature comparison, situation awareness, and 

observer notes are described in the following section. 

Post-Interaction Survey 

The post-interaction survey was administered to each pilot at the end of the eight trial runs. Since 

the questions were administered after the completion of the simulation, there were no distinctions 

among the different experimental conditions. The questions instead queried the participants about 

the general experiences of using VCSPR procedures and tools. Also, because of low statistical 

power for testing, tests for significance were not conducted. 

The pilots responded to the question on the overall utility of the displays for VCSPR approaches as 

highly useful (average of 3, on a scale of 1 to 5). The questions focused on the ease of using the 

displays to derive information for some of the functions handled by the pilots using the displays. 

The pilots found that the overall level of ease for extracting information from the displays was 

very high (M = 5 on a scale of 1 to 5, where 1 was very hard and 5 was very easy). A detailed 

analyses of ease of deriving information is shown in figure 6. In general, on average the pilots 

found that the displays provided enough information, and that it was relatively easy to extract for 

most of the functions. The mean value was greater than or equal to 4 for all functions except flying 

in low visibility. During the group discussions, the pilots mentioned that they would like to see the 

tool deployed in clear weather conditions for a period of time to allow the pilots to develop enough 

trust in the automation before it is used for flying under Category IIIB visibility conditions. They 

felt that this trust could be improved with more familiarity and use of this type of automation. 

Also, the pilots mentioned that deriving information about wake characteristics was very easy in 

this simulation (M = 5). One can infer that the pilots were able to effectively monitor separation of 

the aircraft from the wake. 

All the pilots reported that they were able to effectively monitor the lead aircraft, mostly by using 

the ND. Also, none of the pilots were confused by the interface. On the ability to zoom on the ND, 

the pilots reported that having a separate zoom capability for the pilot flying and pilot not flying 

will enable them to maintain both a strategic and tactical view at the same time. The ND zoom 

capability was handled by a toggle switch on the center console and was available as a function 
12

Figure 6. Ratings (mean and Standard Error (SE)) for ease of deriving information 

from the displays. 

only to the pilot flying. The pilots were asked which aspects of the concept they liked the best, and 

which aspects they liked the least. The pilots liked the system and the new displays because they 

will greatly enhance safety in today’s air traffic environment. They also agreed that the system will 

enhance capacity at the airports. In contrast, the pilots repeated that this automation needs to be 

implemented in good visibility conditions before the pilots will trust the automation for use during 

instrument meteorological conditions (IMC). They were all concerned about procedures for breakout maneuvers, and definition of standards for proximity. They also wanted more flexibility with 

maneuvering throttles without disengaging the auto throttles. One pilot also mentioned that all 

procedures, including airspeed requirements between the coupled aircraft, must be agreed upon by 

the pilots and controllers involved in the procedures prior to flying. 

The pilots were also asked to rate some statements regarding the concept and displays (fig. 7). 

They all agreed that automation is required for VCSPR approaches, and that there was little confusion about the displays. They responded with above-average ratings for ease of monitoring separation from the lead aircraft. The participants also found the wake information on the ND and the 

predictor dots very useful, and they valued being able to visualize the trajectory of the lead aircraft. 

They rated their level of confidence in the concept as average, and they did not indicate concern in 

their responses about the role of the pilot in this concept. 

1.00

2.00

3.00

4.00

5.00

Zoom ND

Monitor separation

Positional awareness fo lead

Flying low visbility

Flying clear weather

Intent line of lead

Intent for trailing

Wake awareness

Trajectory progress awareness
13

Figure 7. Pilots’ subjective ratings (mean and SE) on statements regarding the concept 

and displays. 

Feature Comparison 

The participants were asked to rate the various features on the displays provided to them in the 

simulator. They rated most features as having above-average importance (ranging from 4 to 4.5 on 

a scale of 1 to 5) except the lead aircraft and the LSI on the PFD. Those were rated at an average 

of 3.5 on a scale of 1 to 5, where the higher number indicates higher level of importance. The LSI 

on the ND was not always visible, and all participants complained about not being able to visually 

track the LSI because it was hidden under the solid white icon of the aircraft. The LSI on the PFD 

provided the information about the actual position versus expected position of the simulator in 

terms of distance, whereas the LSI on the ND provided temporal information as referenced by the 

2-sec predictor dots. Despite its poor visibility at certain times, most pilots preferred the LSI on the 

ND. The predictor dots on the lead aircraft were considered to have an average level of importance, because the pilots always flew the follower aircraft in the approach, and they were concerned with their own trajectory predictions to monitor separation from the lead aircraft and its 

wake. Similarly, the feature “out-of-the-window visibility” received a 3.5 rating, and the acknowledgement button used for accepting the coupling between the paired aircraft received a 2.6 average 

rating. During the group discussion, the pilots suggested that pressing the acknowledgment button 

should arm the coupling of the two aircraft, before they are actually at the coupling point, to keep 

it consistent with other standard displays. The pilots also mentioned that the flight-mode annunciation should have a visual indicator that is white, depicting that the system is armed before 

coupling. Eventually it should turn green when actual coupling occurs, at the coupling point. In the 

present experimental setup, the acknowledgement button changed the flight-management-system 

(FMS) annunciation to “coupled” and did not give the pilots a chance to “arm.” This situation 

created some confusion and led to the comments the pilots made. 

1.00

2.00

3.00

4.00

5.00

automation needed for VCSPR

confused about displays

monitor separation was easy

usefulness of wake info ND

usefuleness of wake on PFD

usefulness predictor dots

concerned about role of pilot

value lead's trajectory

have confidence in future of concept
14

Among other concerns and suggestions for improving the design of the system, some pilots had 

difficulty with interpreting the wake depiction and monitoring the lead aircraft on the PFD. Other 

pilots felt that when the aircraft starts deviating from its longitudinal position, the procedure 

should allow for the pilot to adjust the throttles or speed without disengaging the autopilot. 

Situational Awareness 

The situational awareness questionnaire, SART was administered to the pilots after every simulation run. They rated 10 SART elements on a scale of 1 to 7, where 1 is “low” and 7 is “high.” Thus 

the data have been analyzed for all the conditions for each of the three pilots. Because of low statistical power for testing, significance tests were not calculated. The SA ratings have been depicted 

on a line graph to enable better trend comparisons for the conditions. Figure 8 shows that the SA 

trends for the different sub-elements are the same for the aircraft starting with 10- or 5-sec temporal separation between them. The pilots did not feel that any of these situations were unstable, 

and level of variability and complexity was similar in the two conditions. In the group discussions, 

the pilots mentioned that they preferred their aircraft to be ahead rather than behind on the LSI 

because being behind increased the chances of the aircraft getting into the wake zone and out of 

the safe zone. 

Pilots’ responses on SA for the simulator flying on the straight-in path (landing on 18L) or on the 

slewed path (landing on 18R) (fig. 9) show similar trends. The pilots considered the slewed path 

slightly more unstable, variable, and complex, but they also felt that a higher level of concentration 

and familiarity was required with the situation. 

Figure 8. SA responses for 10- vs. 5-sec distance between the two aircraft. 

1

2

3

4

5

6

7

Instability

Variability

Complexity

Alertness

Spare capacity

Concentration

Division-attention

Information Quantity

Information quality

Familiarity

Scale of 1-7

( low to high)

10 sec 5 sec 
15

The SA responses for the visibility condition (fig. 10) showed that the pilots experienced similar 

levels of awareness in the clear versus poor visibility condition. In general, they felt that the poor 

visibility condition was slightly more variable, unstable, and complex. The pilots required slightly 

more alertness, and they had slightly less spare mental capacity in the poor visibility condition as 

compared to clear visibility condition. The information quality, information quantity, and familiarity with the situation were about the same for both of the visibility conditions. 

Figure 9. SA responses for aircraft on straight-in vs. slewed approach. 

Figure 10. SA responses on clear day vs. Category IIIB visibility. 

1

2

3

4

5

6

7

Instability

Variability

Complexity

Alertness

Spare capacity

Concentration

Division-attention

information quantity

Information-quality

Familiarity

Scale 1-7 

( low to high)

1

2

3

4

5

6

7

Instability

Variability

Complexity

Alertness

Spare capacity

Concentration

Division-attention

Information Quantity

Information Quality

Familiarity

Scale 1 to 7 

(low to high)

Straight-in Slewed 

Clear day CATIII B 
16

Observer Notes and Group Discussions 

The observer data yielded some interesting findings. Comments during and after the simulation 

runs from the three participants pertained to issues related to the tools and procedures for closely 

spaced parallel approaches, wake avoidance, and nonnormal events. In addition, many comments 

were associated with the interface of the concept elements, in particular the alerting and display 

features. 

The three pilot participants had several comments about what they perceived were the critical 

aspects of the closely spaced parallel approach concept as it was represented in this study. Pilots 

felt the high degree of automation required for the closely spaced tasks was necessary for the precision of the procedure; however, they all expressed the need for some opportunity to intervene or 

“fine tune” the automation. For example, the ability to manually adjust the speed was recommended by two of the participants. In four of the eight scenarios, pilot participants flew these procedures with visibility at the KSRT airport down to about 600 ft of runway visual range (RVR). 

Another opinion that had general consensus was that flying these types of closely spaced procedures had a higher risk in these low-visibility surface environments. The comments indicated that 

although the pilots understood that automation tools would be necessary for navigation guidance 

and the avoidance of wake vortices, they preferred attaining a visual of the other aircraft to detect 

any cues that may indicate wake-vortex threat or the threat of a possible unexpected escape 

maneuver. Pilots also helped identify factors necessary to create and fly an escape maneuver such 

as traffic, terrain and rest of the airspace. The other four scenarios were in clear weather, and were 

generally found to be more acceptable conditions for the approaches. 

The pilot participants had many comments about the display of the wake information. In general, 

they found the wake depiction and the display locations acceptable. They preferred wake depiction 

on the ND versus the PFD. One pilot stated that it took him some time to understand wake on the 

PFD, raising the issue of the limited training the pilots received for this simulation. As the previous 

comments indicated, there were some concerns about the ability to predict wake responses during 

low-visibility conditions. In addition, all three pilots stated that they did not fully understand the 

nature of wake characteristics, and how these characteristics may impact their own aircraft in 

closely spaced parallel approaches like those flown in our scenarios. They welcomed aircraft 

automation that provided information on wake behaviors and their impact on these procedures. 
17

CONCLUSIONS 

This study investigated a concept that incorporates wake information and new technologies to 

allow for the use of very-closely-spaced parallel runways in all-weather conditions. The airport 

and 25 nmi of surrounding airspace were created and simulated as a part of this effort. A highfidelity full-motion simulator with the emulation of a four-dimensional (4-D) flight management 

system (FMS) was used to implement the concept, and several displays were enhanced to enable 

simultaneous approaches. 

The pilots provided feedback through their responses to the questionnaires and debriefings. The 

three pilots had similar results, and their suggestions were consistent. In general, they were marginally more comfortable with very-closely-spaced parallel runway (VCSPR) approaches and 

automation in visual meteorological conditions (VMC) rather than Category IIIB visibility conditions, even though their situational awareness (SA) ratings showed similar responses for both 

conditions. In addition, they indicated that they preferred 10- versus 5-sec spacing between the 

lead and follower aircraft. The participants felt it was important for them to be able to deploy gear 

and flaps manually, and influence speed and throttles without disengaging the autopilot. All the 

pilots were concerned about potential breakout procedures, and they all think automation will play 

a large role in the determination of the procedures, with direct involvement of the air traffic 

controller necessary for safe procedures. 

FUTURE WORK 

The study provides future research ideas and guidelines for developing procedures for VCSPR. 

Future research efforts by NASA and Raytheon could examine the safety and viability of the procedures and technologies associated with breakout or escape maneuvers under conditions where 

a simultaneous approach needs to be abandoned. In addition, the representation of more airport 

traffic and structures are included so that the implications of surrounding constraints could be 

explored. The possibility of providing more flexibility in the system where pilots could, for example, deploy gears or use throttles for speed control without disengaging the autopilot could also be 

explored. 
18

REFERENCES 

1. Joint Development and Planning Office: The Next Generation Air Transport System 

Integration National Plan. Dec. 12, 2004. 

2. Magyratis, S.; Kopardekar, P.; Sacco, N.; and Carmen, K.: Simultaneous Offset Instrument 

Approaches –Newark International Airport: An Airport Feasibility Study. DOT/FAA/CTTN02/01, 2001. 

3. Massimini, V.S.: Simultaneous Independent and Dependent Parallel Instrument 

Approaches. Assumptions, Analysis, and Rationale. Mitre Report MP 06W0000127, 2006. 

4. Abbott, T.S.; and Elliot, D.M.: Simulator Evaluation of Airborne Information for Lateral 

Spacing (AILS) Concept. NASA/TP-2001-210665, 2001. 

5. Miller, M.E.; Dougherty, S.; Stella, J.; and Reddy, P.: CNS requirements for precision 

flight in advanced terminal airspace. Aerospace, 2005 IEEE Conference, pp. 1–10, 2005. 

6. Pritchett, A.R.; and Landry, S.: Operational Concepts for Closely-Spaced Parallel 

Approaches. Proc. Digital Avionics Systems Conf. (DASC00), St. Louis, Mo., pp. 4.C.2-1, 

Oct. 1999. 

7. Houck, S.; Barrows, A.; Parkinson, B.; Enge, P.; and Powell, D.: Flight Testing WAAS for 

Use in Closely-Spaced Parallel Approaches. Proc. ION-GPS 1999 Meeting, Nashville, 

Tenn., 1999. 

8. Hardy, G.H.; and Lewis, E.K.: A Cockpit Display of Traffic Information for CloselySpaced Parallel Approaches. AIAA-2004-5106, AIAA Guidance, Navigation, and Control 

Conference and Exhibit, Providence, R.I., Aug. 16–19, 2004. 

9. Rossow, V.J.; Hardy, G.H.; and Meyn, L.A.: Models of Wake-Vortex Spreading Mechanisms and Their Estimated Uncertainties. AIAA-2005-7353, ATIO Forum, Arlington, Va., 

Sept. 26–28, 2005. 

10. Durso, F.T.; Hackworth, C.A.; Truitt, T.R.; Crutchfield, J.; Nikolic, D.; and Manning, 

C.A.: Situation Awareness as a Predictor of Performance for En Route Air Traffic Controllers. Air Traffic Control Quarterly, vol. 6, no. 1, pp. 1–20, 1998. 

 
19

APPENDICES 

Appendix A – Schedule and Test Matrix for March 27–29, 2007 

8:30–9:00 Introduction to project 

9:00–9:30 Introduction to concept 

9:30–10:00 Classroom training 

10:00–10:15 Break 

10:15–10:25 Motion briefing 

10:30–10:45 Demo run 

10:45–10:55 Run 1 

11:00–11:10 Run 2 

11:15–11:25 Run 3 

11:30–11:40 Run 4 

11:45–12:45 Lunch break 

12:45–12:55 Run 5 

1:00–1:10 Run 6 

1:15–1:25 Run 7 

1:30–1:40 Run 8 

1:40–2:00 Break 

2:00–2:30 Breakout 

2:30–4:00 Debrief 
20

Appendix B – Demographic Survey 

Personal Information 

1. Name 

2. Age 

Pilot Experience 

3. Total years of experience as a pilot 

4. Airlines you have worked with 

a. 

b. 

c. 

5. Types of aircraft flown/hours flown 

Type of aircraft No. of hours flown 

 

6. Do you have any experience flying closely spaced parallel approaches such as SOIA? 

If yes, please describe. 

 

 

 

7. If retired as a pilot, state number of years since retirement: Years 

8. Please list all computer systems, displays, and other technology aids you used or had 

access to as a pilot. 

 

 

 

9. Please indicate your years of personal computer experience. 

1 2 3 

Less than 2 years 2–4 years 5+ years 
21

Appendix C – Post-Interaction Survey 

Participant # 

VCSPR Post-Interaction Survey 

1. Overall how would you rate the utility of the displays for very-closely-spaced parallel 

approaches: 

Not useful at all Somewhat not 

useful 

Neutral Somewhat 

useful 

Very useful 

1 2 3 4 5 

1. What aspects of the concept are you most excited about or think are most worthy of future 

implementations? 

 

 

 

2. What aspects of the concept are you the least excited about or think are unworthy of future 

implementations? 

 

 

 

3. Is there some information that should be included here but isn’t? Please list. 

 

 

 

4. Were you able to effectively monitor the lead aircraft? 

Yes No If No, please explain: 

 

5. Did any aspect of the interface confuse you at any time? 

Yes No If Yes, please explain: 

 

6. Overall how would you rate the apparent ease to derive information from the displays? 

Very 

difficult 

Somewhat 

difficult 

Neutral Somewhat 

easy 

Very 

easy 

1 2 3 4 5 

 
22

7. Looking at the interfaces in the displays in the cockpit, please rate the ease of deriving 

information from the displays for the following tasks: 

 Very 

difficult

Somewhat 

difficult

Neutral Somewhat 

easy

Very 

easy

Zooming the navigation display 1 2 3 4 5 

Monitoring separation from lead 

aircraft 1 2 3 4 5 

Maintaining positional awareness 

of lead aircraft 1 2 3 4 5 

Flying in low visibility after 

coupling point 1 2 3 4 5 

Flying in clear weather day after 

coupling point 1 2 3 4 5 

Viewing the trajectory/intent line 

of the lead aircraft 1 2 3 4 5 

Viewing trajectory/intent line of 

the trailing aircraft 1 2 3 4 5 

Wake-vortex hazard awareness 1 2 3 4 5 

Trajectory progress awareness 

 1 2 3 4 5 

8. Please state your agreement/disagreement with each of the following statements (check one 

number in each row) 

 Strongly 

disagree

Somewhat 

disagree

Neutral Somewhat 

agree 

Strongly 

agree

This automation concept is 

needed for the pilots. 1 2 3 4 5 

I did not understand what I was 

looking at most of the time. 1 2 3 4 5 

Monitoring separation with the 

lead aircraft was easy. 1 2 3 4 5 

Seeing wake information on ND 

was useful for me. 1 2 3 4 5 

Seeing wake information on PFD 

was useful for me. 1 2 3 4 5 

Seeing the predictor paths was 

useful for me. 1 2 3 4 5 

I am concerned about the role of 

the pilot in the use of this 

automation. 

1 2 3 4 5 

I value being able to see the 

route of the lead aircraft. 1 2 3 4 5 

I am confident that this concept 

can be integrated into flight 

operations in the future. 

1 2 3 4 5 

9. Please list any concerns you may have about very-closely-spaced parallel approaches. 
23

Appendix D – Feature Comparison Survey 

Participant #:______________ 

The following survey is intended to capture your value ratings for various features and design 

elements of the new very-closely-spaced parallel approach runways. Please rate how much you 

value each of the following features. 

 Very 

unimportant 

Somewhat 

unimportant 

Neutral Somewhat 

important 

Very 

important 

Ownship on navigation display 

(ND) 

1 2 3 4 5 

Lead aircraft on ND 1 2 3 4 5 

Lead aircraft on primary flight 

display (PFD) 

1 2 3 4 5 

Waypoints on ND 1 2 3 4 5 

Intent line or route of ownship 1 2 3 4 5 

Intent line/route of Lead 

aircraft 

1 2 3 4 5 

Zooming capability on ND 1 2 3 4 5 

Longitudinal situation indicator 

(LSI) on ND 

1 2 3 4 5 

LSI on PFD 1 2 3 4 5 

Predictors of path information 

for lead aircraft on ND (dots) 

1 2 3 4 5 

Predictors of path information 

for trailing aircraft on ND (dots) 

1 2 3 4 5 

Predictors of path information 

for lead aircraft on PFD (dots) 

1 2 3 4 5 

Out-the-window visibility of 

lead aircraft in a clear day 

1 2 3 4 5 

Wake hazard zone of lead 

aircraft on ND 

1 2 3 4 5 

Wake hazard zone of lead 

aircraft on PFD 

1 2 3 4 5 

Changes in FMS/PFD 

annunciation after coupling 

1 2 3 4 5 

Acknowledgement button for 

coupling 

1 2 3 4 5 

Datalink message showing 

“TACEC Coupling “ on EICAS 

1 2 3 4 5 

1. Do you have suggestions for improving the design, presentation, or behavior of any of the 

elements listed in these questions? If so, please describe below. 
24

Appendix E – Observer Form 

TACEC March Study 

Date: Run # Condition: 

Scenario: Observer: Time: 

Describe the incident: 

 

 

 

Time Describe the incident 

 

 

 

 

Time Describe the incident 

 

 

 

 

Time Describe the incident 

 

 

 

 

Time Describe the incident 

 

 

 

 

 
25

TACEC March Study (continued) 

Date: Run # Condition: 

Scenario: Observer: 

Did the pilot appear to notice the TACEC coupling immediately (e.g., hit “accept”)? 

Did you see any events or hear any comments from the pilot regarding the TACEC alerting? 

Did you see any events or hear any comments from the pilot regarding situational 

awareness? 

Did you see any events or hear any comments from the pilot regarding the display? 

Did you see any events or hear any comments from the pilot regarding workload? 

Were there any events that you thought were significant? (Please include description of any 

malfunctions, display distortions, motion problems, etc.)?

 
26

Appendix F – List of Questions for Group Discussion 

1. What information would you require from the lead to perform a breakout maneuver? 

2. Would you like to see zoom feature change the size of the aircraft icon? 

3. Would you like to see a forward boundary of safe flying zone on display? 

4. Would you like to see the number of seconds in trail added to the display somewhere? 

5. Are we scaling the wake display to the icon size in the way you would like? 

6. Do we want predictors (dots) past 10 seconds? 

7. Was the datalink message showing the flight trajectory at the start of the simulation to be 

flown useful? Would you like to see it differently? 

8. Was the acknowledgement button before coupling useful? 

9. What do you like about the concept? 

10. Discuss breakout maneuvers based on a scenario as shown 

11. Discuss low-visibility problems. Are the displays sufficient? 

12. Discuss questions from the post-interactive survey. 

13. What do you think about the jurisdiction of the tower controller? Where should it start and 

end? What will be the responsibilities of the controller before and after the coupling point? 

14. What did you think about the display changes that occur after coupling of aircraft? FMS 

annunciation? Dashed magenta line for lead aircraft? 

15. What do you think about having no manual control over the system? 

16. If you are in manual control, could you be at the coupling as accurately as with automation? 

What kind of cues will you need? 

 
27

Appendix G – Layout and Design of SRT Airport 

As stated previously, the SRT airport is based on the current Dallas/Fort Worth International Airport (DFW) layout. Figure G-1 illustrates the current DFW airport configuration, and figure G-2 

illustrates the modifications made for the Virtual Aerospace Simulation Technologies (VAST) 

Terminal Area Capacity Enhancing Concept (TACEC) simulation. 

Figure G-1. Current DFW Airport layout. 

Figure G-2. SRT Airport layout. 

 
28

Because the simulation focused on studying TACEC approaches to very-closely-spaced parallel 

runways, and because of the decision to have a south air traffic flow for the simulation scenarios, 

the SRT airport utilized only runways 18R, 18L, 17R, and 17C (renamed to 17L). All four runways could be used for arrivals and departures, and all were assumed to be equipped to a Category 

IIIB level. Both runways 18R and 17L were moved to within 750 ft of their inboard runways, 18L 

and 17R, respectively, requiring an adjustment of 464 ft from their current DFW position. See 

table G-1 for the DFW runway position changes made for the simulation. 

In order to support a variety of scenarios, five runway configurations and associated airspace 

routes were developed. These configurations are summarized in tables G-2 and G-3. Configuration 

#2 is the only configuration that the DFW airport currently supports. For this configuration, the 

airspace design matches the current DFW design. The other four configurations were based on current DFW operations (Standard Terminal Arrivals (STARs), Standard Instrument Departures 

(SIDs), and Approach Plates), but had to be modified to accommodate both the desired runway 

configurations and the TACEC concept. 

TABLE G-1. SRT RUNWAY POSITIONS 

Runway Old Latitude/Longitude New Latitude/Longitude 

18R 32-54-56N / 097-03-17W 32-54-56N / 097-03-12W 

18L 32-54-56N / 097-03-03W same 

17R 32-54-56N / 097-01-47W same 

17L 32-54-56N / 097-01-34W 32-54-56N / 097-01-39W 

TABLE G-2. RUNWAY CONFIGURATIONS BY PROCEDURE 

Name Paired Arrivals Single Arrivals Paired 

Departures 

Single 

Departures 

Configuration #1 18R and 18L 17L – 17R 

Configuration #2 – 18R and 17L – 18L and 17R 

Configuration #3 – 17L 18R and 18L 17R 

Configuration #4 17R and 17L 18R – 18L 

Configuration #5 – 18R 17R and 17L 18L 

TABLE G-3. RUNWAY CONFIGURATIONS BY OPERATION 

(A = ARRIVAL, D = DEPARTURE) 

Name 18R 18L 17R 17L 

Configuration #1 A A D A 

Configuration #2 A D D A 

Configuration #3 D D D A 

Configuration #4 A D A A 

Configuration #5 A D D D 
29

The TACEC concept calls for TACEC-assigned four-dimensional (4-D) arrival trajectories to 

begin at meter fixes located near the edge of the terminal airspace, normally 40–60 nmi from the 

airport. Flights in the VAST TACEC simulation began 25 nmi from the airport. Routes in the SRT 

airspace were designed to work both with and without TACEC tools and procedures. In order to 

facilitate a comprehensive design, an effort was made to reuse as much of the existing DFW traffic-flow operations as possible, including: STARs, SIDs, Approach Plates, Arrival Meter Fixes, 

Departure Meter Fixes, and Standard Operating Practices.