DOT/FAA/AM-02/5

O. Veronika Prinzo

Civil Aerospace Medical Institute

Federal Aviation Administration

Oklahoma City, OK 73125

April 2002

Final Report

This document is available to the public

through the National Technical Information

Service, Springfield, VA 22161.

Automatic Dependent SurveillanceBroadcast / Cockpit Display of

Traffic Information: Innovations in

Pilot-Managed Departures Office of Aerospace Medicine

Washington, DC 20591
NOTICE

This document is disseminated under the sponsorship of

the U.S. Department of Transportation in the interest of

information exchange. The United States Government

assumes no liability for the contents thereof.
i

Technical Report Documentation Page

1. Report No. 2. Government Accession No. 3. Recipient's Catalog No.

DOT/FAA/AM-02/5

4. Title and Subtitle 5. Report Date

Automatic Dependent Surveillance -Broadcast Cockpit Display of Traffic

Information: Innovations in Pilot-Managed Departures

April 2002

6. Performing Organization Code

7. Author(s) 8. Performing Organization Report

No.

Prinzo, O.V.

9. Performing Organization Name and Address 10. Work Unit No. (TRAIS)

FAA Civil Aerospace Medical Institute

P.O. Box 25082

Oklahoma City, OK 73125 11. Contract or Grant No.

12. Sponsoring Agency name and Address 13. Type of Report and Period

Covered

Office of Aerospace Medicine

Federal Aviation Administration

800 Independence Ave., S.W.

Washington, D.C. 20591 14. Sponsoring Agency Code

15. Supplemental Notes

This work was performed under Task AM-B-00-HRR-516

16. Abstract:

Avionics devices that provide a cockpit display of traffic information (CDTI) enable pilots to acquire, verify, and

maintain pre-defined spacing intervals from other aircraft. It is of interest to the Federal Aviation Administration to

determine how the use of these displays influences pilot/controller operational communications. The operational

evaluation of the CDTI in October 2000 provided an opportunity to examine some of these issues. Departure

profiles (13 without CDTI, 32 with CDTI) were established to evaluate the ability of flight crews and air traffic

controllers to manage long (6 nm) and short (4.5 nm) spacing intervals between departing aircraft during 3 day and

2 night operations. Subject-matter experts evaluated 15 hours of verbatim transcripts and audiotapes for benefits

that may have resulted from pilot use of the ADS-B/CDTI. They also evaluated these communications for

communication problems associated with misidentified aircraft, confusions, uncertainties, and operational

concerns. Computed for each departure was the time the aircraft was under local control, runway ownership time,

and the number and duration of messages. Approximately 4% of the departures conducted when CDTI was not

used, and 9% when it was, involved communication problems. In particular, for pilot messages during CDTI

departures, aircraft call signs were misstated or incorrect. However, when CDTI was not used, controller messages

included the correct flight identifier but the wrong company name. In addition, more messages were exchanged

during the short spacing interval. In contrast, when pilots executed CDTI departures, there was an overall increase

in time on frequency, more time was spent under local control during the day, and departures were completed in

less time when assigned the short spacing interval. Communication problems were associated with the call sign

procedure that was designed to distinguish between aircraft being talked to versus talked about. Fortunately,

controllers and pilots detected and corrected these problems in mid-stream, and statistically, communication

efficiency was not affected. In light of the findings and comments from the controllers and pilots, alternative call

sign procedures will be constructed and evaluated for the departure spacing application.

17. Key Words 18. Distribution Statement

Pilot Communication Document is available to the public through the

ATC Communication National Technical Information Service

Air Traffic Control Springfield, Virginia 22161

19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price

Unclassified Unclassified 14

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized

1

AUTOMATIC DEPENDENT SURVEILLANCE - BROADCAST / COCKPIT DISPLAY OF

TRAFFIC INFORMATION: INNOVATIONS IN PILOT-MANAGED DEPARTURES

“You on the cutting edge of technology

have already made yesterday’s impossibilities

 the commonplace realities of today”

— President Ronald Reagan,

White House, February 12, 1985

INTRODUCTION

The Automatic Dependent Surveillance-Broadcast

(ADS-B)1

 is a data link application that will transmit

from aircraft and vehicles equipped to emit surveillance data (such as position and identification) by

means of a broadcast-mode to users who can receive

these data. The Federal Aviation Administration (FAA)

anticipates that ADS-B will provide many benefits —

from extending the range and coverage of current

ground-based secondary surveillance radar (especially

around airport surfaces) to increasing air-to-air situational awareness. The FAA envisions that enhanced

airborne and ground capabilities would provide for

specific surveillance functions that would encourage

co-operative air traffic management and collaborative

decision-making among its users (Prinzo 2001).

ADS-B may also offer some innovative technology

that could remove the delays attributed to low-ceiling/reduced visibility weather that currently restricts

departure operations. For example, with improved

airport surface surveillance, ADS-B supported avionics may provide synthetic or virtual digital-imaging of

other aircraft, vehicles, or obstacles to the operator

that would not be visible otherwise. This capability

could potentially enhance safety.

Avionics devices that provide a cockpit display of

traffic information (CDTI) enable pilots to acquire,

verify, and maintain pre-defined spacing intervals

from other ADS-B equipped aircraft. It is of interest

to the FAA to determine how the use of these displays

influences pilot/controller operational communications. For example, a pre-determined spacing interval

could be included as part of an aircraft’s (i.e., Ownship)

pre-departure clearance (PDC). Following route taxi

instructions, the pilot could taxi into position and

monitor the distance between the nose of Ownship

and the tail of the immediately departing aircraft

using a CDTI. Once the spacing interval specified in

the PDC was achieved, the pilot would begin the takeoff roll and the next aircraft would taxi into position

and hold. Under varying weather conditions, different aircraft types or sequences (e.g., a B727 behind a

B757), and runway layouts, different spacing intervals might be desirable. The second operational evaluation of CDTI (OpEval-2) occurred in October 2000

and provided an opportunity to examine some of

these issues.

The stated purposes of OpEval-2 were to develop

and evaluate specific ADS-B air-air and air-ground

applications, to evaluate controller use of ADS-B, and

to demonstrate ADS-B technology.2

 Both the pilot and

controller based concepts of departure spacing/clearance were assessed. Before proceeding any further, it

must be pointed out, as it was during OpEval-1, that

OpEval-2 provided an opportunity to demonstrate

new air- and ground-based capabilities and systems at

an FAA-controlled airport tower and terminal radar

approach control facility. With that in mind, it is

important to note that it was not possible to apply true

experimental and control conditions comparable to

that of laboratory-based experiments. In addition, the

training that pilots and controllers received was uneven — making it impossible to exercise any statistical

control over the data (e.g., treating the number of

hours of training as a co-variant).

However, OpEval-2 provided an opportunity to

gather field data that could be used to guide the

development of ADS-B applications (e.g., approach

spacing, departure spacing/clearance, runway and final approach occupancy awareness, and airport surface situational awareness). During that five-day event,

objective and subjective data were collected from

controllers and pilots, and a comprehensive report of

1

 In 1998, RTCA SC-186 completed Minimum Aviation System Performance Standards for ADS-B. In addition to describing ADSB, this document also provides information on applications that may use ADS-B information.

2

 This was cited in the Flight Crew Mission Guide that was developed for OpEval-2 by the Operational Evaluation Coordination

Group (OCG 2001).
2

the findings was prepared by the Operational Evaluation Coordination Group (OCG, 2001). Joseph,

Domino, Battiste, and Bone (under review) provide a

summary of the subjective flightdeck observer data.

Reported here is a summary of several analyses performed on the audiotaped communications between

pilots flying aircraft equipped with a CDTI device

and local controllers who provided them with air

traffic services. The objective of the voice tape analysis

was to identify any change in operational communications, workload, or both that resulted when pilots were

flying with and without the benefit of CDTI. This report

provides a general description of the communication

findings for the departure spacing application.

METHOD

Participants

Sixteen pilots, serving as a captain or first officer,

flew aircraft equipped with CDTI while a local and

ground controller along with a coordinator served as

the OpEval-2 tower team who provided them with air

traffic control (ATC) services. The pilot participants

were paid volunteers who received briefings and participated in proficiency training exercises prior to the

evaluation. The controllers, also volunteers, were on

a temporary detail during training and on a regular

schedule during the evaluation.

Materials

The Louisville (Standiford) International Airport

(SDF) Radar Approach Control (TRACON) facility

provided five, digital audiotapes (DAT), one for each

test period. Each DAT contained separate voice records

of all the transmissions made to the radio frequency

assigned to the Ground East, Local West, or Final

Radar West position on the left channel. The right

channel contained the Universal Time Coordinated

(UTC) time code expressed in date, hour (h), minute

(min), and whole second (s). The NiceLoggerTM Digital Voice Reproducer System (DVRS) decoded and

displayed time and correlated it with the voice stream

in real time. The data consisted of 15 hours of digitized voice communications of which 6 hours were

from the Local West position.

Procedure

Training on the Departure Spacing Application.

Before OpEval-2, pilots and controllers participated

in several pre-OpEval-2 simulations conducted at the

Integration and Interaction Laboratory (I-Lab) of the

MITRE Corporation Center for Advanced Aviation

System Development (CAASD). During these

simulations, pilots were instructed on how to respond

to various types of ATC messages and listened to a

combination of ATC and pseudo-pilot communications over a party line. They were to abide by the same

requirement for pilot-managed and ATC controlled

departure spacing. That is, at brake release, pilots were

to say “MARK” on the tower radio frequency for data

collection purposes.

Experimental OpEval-2 Departures. During the preflight briefings at the Air Guard (for pilots) and Tower

(for controllers), all of the participants reviewed the

flight scenarios and scripts. The facilitators reminded

them to follow the established procedures and communication protocols. Afterwards, the pilots proceeded to

their respective aircraft and the controllers went to their

air traffic control positions in the tower or radar room.

For each flight period, the departure profiles were

set up to evaluate the ability of the flight crew and

controllers to manage a pre-determined spacing interval between departing aircraft. Typically, pilots taxied

their aircraft along the assigned routes, held short of

the active runway, and, following the receipt of the

departure clearance flew a pre-determined pattern,

landed the aircraft, taxied to the runway and departed

again. The sequence of aircraft in the taxi pattern

varied for each departure. Enumerated below are the

procedures used to attain the OpEval-2 goals and

ensure compliance with standard ATC procedures.

For the purpose of this study, the departure spacing

interval was the distance between a pair of aircraft

when the leading aircraft began its take-off roll down

the runway. Each departure scenario defined the spacing interval as 6 nautical miles (nm, long) or 4.5 nm

(short) between each pair of departing aircraft. Pilots

managed the spacing interval between all but the final

aircraft in the departure sequence. The local controller managed that aircraft.

Pilot-Managed Departure Spacing Interval. All participants used scenario cards that defined the departure

spacing interval to be achieved for the flight period. As

shown in Figure 1, once the lead aircraft was 6000 ft

above the runway (Point A), local control provided a

take-off clearance to the aircraft that was holding short of

the active runway using standard phraseology and communication practices. The pilot positioned the aircraft

onto the runway. By using information displayed on the

CDTI (e.g., Ownship was 2.5 nm from the departing

aircraft and it was at R=6000 feet elevation), the pilot

determined when the scripted distance (either 4.5 nm or

6 nm) would be achieved and then began the aircraft’s

take-off roll down the runway. Local control protected

the runway during the time the flight crew delayed the

take-off roll.
3

Speaker MESSAGE

N123 1. ACADEMY TOWER NOVEMBER ONE TWENTY-THREE' S HOLDING IN TURN

BEHIND NOVEMBER FOUR FIFTY-SIX

ATC 2. NOVEMBER ONE TWENTY-THREE {NAME} TOWER ROGER

ATC 3. NOVEMBER ONE TWENTY-THREE RUNWAY ONE SEVEN RIGHT TURN RIGHT

HEADING ONE NINER ZERO CLEARED FOR TAKE-OFF

N123 4. CLEARED FOR TAKE-OFF NOVEMBER ONE TWENTY-THREE

N123 5. NOVEMBER ONE TWENTY-THREE MARK

ATC 6. NOVEMBER ONE TWENTY-THREE CONTACT DEPARTURE

N123 7. NOVEMBER ONE TWENTY-THREE

Figure 2. Example of a Pilot-Managed Departure Communication Set.

Figure 1. Departure Spacing Interval Criteria between Participating Aircraft.

✈ 6000 ft

✈

Interval Criteria (4.5 or 6 nm) 2.5

R = 6.0

2.5nm

A

CDTI Display

Speaker MESSAGE

N123 1. ACADEMY TOWER NOVEMBER ONE TWENTY-THREE ZERO READY FOR TAKEOFF HERE ONE SEVEN RIGHT AT BRAVO

ATC 2. NOVEMBER ONE TWENTY-THREE {NAME} TOWER RUNWAY ONE SEVEN

RIGHT TAXI INTO POSITION AND HOLD TRAFFIC STARTING SIX MILE FINAL

N123 3. POSITION AND HOLD ONE TWENTY-THREE

ATC 4. NOVEMBER ONE TWENTY-THREE RUNWAY ONE SEVEN RIGHT CLEARED FOR

TAKE-OFF TURN RIGHT HEADING TWO FIVE ZERO WIND ONE EIGHT ZERO AT

FIVE

N123 5. CLEARED FOR TAKE-OFF NOVEMBER ONE TWENTY-THREE AND TWO FIVE

ZERO ON THE HEADING

ATC 6. NOVEMBER ONE TWENTY-THREE CONTACT DEPARTURE

N123 7. OVER TO DEPARTURE

Figure 3. Example of a Controller-Managed Departure Communication Set.
4

As shown in Figure 2, a pilot-managed departure

communication set generally began when a pilot initiated the initial call up, as illustrated by message 1.

When the runway was clear the controller issued the

take-off clearance, and in some instances, issued a

vector, or climb-out-instruction as was the case in

message 3. The pilot taxied onto the runway and upon

release of the break, responded with “MARK” (or

similar words such as “Rolling”) as in message 5. The

inclusion of “MARK” indicated that the aircraft had

begun its acceleration down the runway. The communication set ended when the local controller instructed

the pilot to contact departure as illustrated by message 6.

Controller-Managed Departure Spacing Interval.

Again, as with the pilot-managed departures, for the

controller-managed departures all of the participants

followed the scripted scenarios that defined the to-beachieved departure spacing interval for the flight

period. As shown in Figure 3, a controller-managed

departure communication set generally began when

the pilot initiated the initial call up, as illustrated by

message 1. The local controller determined when to

instruct the pilot to “taxi into position and hold.”

Then, when in the controller’s judgment the anticipated scripted distance of 4.5 or 6 nm would be

achieved, the take-off clearance was issued using standard phraseology and communications procedures.

Similarly, the controller-managed communication set

ended when the local controller instructed the pilot to

contact departure, as illustrated by message 6.

Experimental Design

The TRACON and tower were divided into two

sections, with the West portion of the airspace dedicated to OpEval-2. In addition, a portion of the

airfield was set apart from normal operations and the

tower controllers limited access to the West runway to

participating aircraft. The OpEval-2 flight periods

were scheduled during normally low airport activity.

The participating aircraft made 69 departures that

resulted in 54 departure pairs, of which two were lost

to equipment failure and one to a loss of data.

This study used a two-factor within-subjects design. The within-subjects factors were Time of Day

(Day, Night) and Spacing Interval (Short, Long). A

between-groups comparison (Pilots, Controllers) was

not attempted since there were more pilot participants

than controllers, and pilots had access to ADS-B

information and controllers did not.

Independent Variables. Departure profiles were

established to evaluate the ability of flight crews and

air traffic controllers to manage the 31 long (6 nm)

and 20 short (4.5 nm) spacing intervals between

departing aircraft during 3 day (flight periods 1, 2,

and 4) and 2 night (flight periods 3 and 5) operations.

The departure spacing application was performed by

the pilots with the use of ADS-B distance information

displayed on a CDTI or by the Local West controllers

without benefit of ADS-B information. Forty-five

departures began in initial contact and ended in a

hand-off to the departure controller. Analyses were

performed on 32 pilot-executed departures conducted

with ADS-B/CDTI and 13 controller-managed departures conducted without ADS-B/CDTI.

Dependent Variables. To measure changes in

workload and operational communication, (the primary variables of interest), the communications between local control and each aircraft for each departure

were grouped into departure communication sets.

Presented in Figure 4 is an example of one of the pilotmanaged departure communication sets. Measures of

workload included efficiency of communications and

duration measures for communication sets. Measures

of operational communication included communication problems and operational concerns. These measures were designed to provide the cost benefits

subgroup of the OCG with a metric to help estimate

the operational impact and the benefits of CDTI.

They are described below.

Efficiency of Communications. Less time spent on

frequency coupled with fewer departure-related transmissions to perform the departure spacing task may

reflect improved efficiency in operational communication and a reduction in objective workload. Thus,

efficiency of communications included the number of

messages in a communication set that contained departure information and the duration of each of those

calls. The duration of individual calls was the time

spent on frequency (TOF) communicating. As shown

in the example in Figure 4, TOF for the first message

was 2s.

Duration Measures for Communication Set. Additional measures of objective workload were frequency

occupancy time (FOT), runway ownership time

(ROT), and the amount of time the aircraft was under

local control (TLC). They were computed for each

communication set that began with initial contact

and ended in transfer of communication to the departure controller. Frequency occupancy time was the

sum of all of the TOF for each communication set and

in the example, FOT was 12s (FOT = S TOF =

2+2+4+2+0+2+0).

ROT was computed as the time lapsed from the

onset of a message by local control that included a

take-off clearance to the onset of a message by the

controller for transfer of communication to the depar-
5

ture controller. In the example shown in Figure 4,

151s lapsed from the issuance of the take-off clearance

in message 3 (078s) to the transfer of communications

in message 6 (229s). During this time, the runway is

active and, therefore, unavailable to local control for

other vehicle movement or aircraft operations (runway crossing, landings, etc.). It is during this time that

workload increases: For the local controller, additional

effort is required to scan the airport surfaces for a

potential runway incursion when there is a delay in

the take-off roll. For pilots, monitoring the supplementary CDTI display may add workload while performing routine station-keeping tasks and preparing

for take-off. Runway ownership time, as a by-product

of ADS-B/CDTI use for pilot-managed departures

task, was included as a measure of objective workload.

For each aircraft, the total time under local control

(TLC) was computed as the time lapsed from the

onset of the pilot’s initial call-up in message 1 (at

007s) to the closing of the transaction in message 7 (at

232s). In the example TLC was 225s (232s-007s).

Communication Problems. SMEs identified communication problems as “any disturbance of routine

communication, where controllers and pilots do not

follow standard procedures, and/or where they must

interrupt information transfer in order to clarify the

communication” (Morrow, Lee, and Rodvold, 1990

pp. 36). Communication problems included inaccuracies, procedural deviations, and non-routine transactions that involved misunderstandings or other

problems related to successful information transfer.

The use of the traffic-flight identifier in trafficrelated messages by controllers during the Initial/

Final Approach Spacing Application and Visual Acquisition Evaluation may have encouraged pilots to

include it as part of their responses to those messages.

Pilots who received messages in the form of “NOVEMBER ONE TWENTY-THREE TRAFFIC

TWELVE O’CLOCK ... NOVEMBER FOUR

FIFTY-SIX” may have responded with ... “NOVEMBER FOUR FIFTY-SIX IN SIGHT. ” In fact, of the

889 pilot responses to traffic-related messages, 45%

included either the full (362) or partial (40) call sign

of the aircraft called as traffic (Operational Evaluation

Coordination Group, 2001). Accordingly, inclusion

of the traffic-flight identifier may have inadvertently

migrated into pilots’ communications with the local

controller during the departure spacing application.

Consequently, use of the traffic-flight identifier may

have contributed to communication problems and

added workload.

Time (in seconds)

Speaker MESSAGE Start End TOF ROT TLC

N123 1. AND GOOD EVENING TOWER NOVEMBER ONE

TWENTY-THREE IS IN SEQUENCE

 007 009 2 151 225

ATC 2. GOOD EVENING NOVEMBER ONE TWENTY-THREE

ACADEMY TOWER ROGER NUMBER TWO

011 013 2

ATC 3. NOVEMBER ONE TWENTY-THREE ACADEMY

TOWER RUNWAY THREE FIVE LEFT FLY HEADING

THREE THREE ZERO CLEARED FOR TAKE-OFF

 078 082 4

N123 4. CLEARED FOR TAKE-OFF THREE FIVE LEFT THREE

THREE ZERO NOVEMBER ONE TWENTY-THREE

083 085 2

N123 5. MARK 176 176 0

ATC 6. NOVEMBER ONE TWENTY-THREE CONTACT

DEPARTURE

 229 231 2

N123 7. NOVEMBER ONE TWENTY-THREE 232 232 0

LEGEND: TOF = Time on frequency per transmission

ROT = Runway occupancy time per aircraft

TLC = Time under local control per aircraft

Figure 4. Example of a Departure Communication Set.
6

Operational Concerns. SMEs also identified and

categorized operational concerns into the “Traffic

Advisory”, “Position Operation”, or both categories.

For example, when pilots reported seeing traffic on

the CDTI but not out-the-window, SMEs encoded

these reports as a concern that the pilots may not be

maintaining compliance with traffic advisory procedures. Similarly, SMEs encoded pilot self-separation

from traffic as a concern in flight deck operation. As

SMEs listened to the audiotapes and read the transcripts, they encoded their concerns and provided

brief comments.

In summary, message counts, contents, and duration were the objectively derived measures of workload

and communication extracted from the time-stamped

voice tapes. They were used to compute descriptive

statistics expressed as means (M) and standard deviations (SD) that summarized CDTI use versus non-use

on operational efficiency between ATC and the participating flight crews. Operational communication

in the form of phraseology, communication problems, and operational concerns provided some insights and implications for future air traffic operations,

workload, and communications procedures.

Data Extraction, Training, and Data Encoding

Procedures

This section begins with a description of the qualifications of the Subject Matter Experts (SMEs), continues with the data extraction procedures and is

followed by the procedures used by the lead SME to

train the other SMEs. The section ends with an

explanation of the data encoding process.

Qualifications of the Subject Matter Experts. The

lead Air Traffic Subject-Matter Expert was an instrument-rated pilot and former controller who had worked

as a FAA Academy instructor for 8 years and for 12

years in FAA supervision and management. Two

additional air traffic SMEs had been instructors (Terminal Option) at the FAA Academy in Oklahoma

City. The pilot subject matter expert was a recently

retired airline pilot with 31 years of experience. Prior

to serving as a SME, the pilot’s duties included instructor on the B-727 and DC-8 aircraft; check airman

on the DC-9 aircraft; pilot of the CV-880, DC-8, B727, DC-9, L-1011, B-757, and B-767 aircraft.

Data Extraction Procedures. Five sets of audiocassette tapes were dubbed from each digital audio tape

(DAT). The transcribers used one copy to generate

five sets of verbatim transcripts, and each message was

typed onto an electronic copy of the Aviation Topic

Speech Act Taxonomy-Coding Form (ATSAT-CF)

like the one presented in Figure 5 (Prinzo, Britton, &

Hendrix, 1995). Each message was preceded by its

onset and offset time represented in hour (HH) minute

(MM) and seconds (SS) and was followed by a column

to record comments and a column to code operational

concerns. Unlike the identifiers “N123” and “N456”

that are presented in Figure 5, true aircraft identifiers

and flight numbers were included as part of the

OpEval-2 transcripts for all the aircraft that were

present on the DAT.

Training Subject Matter Experts. The lead SME

provided the other SMEs with 16 hours of training on

the data encoding process to achieve consistency and

conformity in identifying communication transactions and evaluating the accuracy of content. Since

OpEval-2 imposed minor operational constraints,

SMEs received instruction on how to evaluate communications in light of those modifications. Furthermore, the lead SME encouraged the other SMEs to

direct their attention to the detection and codification of any benefits that may have occurred from the

pilots having access to a CDTI. In addition to commenting on positive outcomes, they also were to

comment on any situation involving a potential or

real loss of separation or situation awareness, misunderstanding, or communication problem (missed

readback of the identifiers, routes, altitudes, etc.).

Finally, the SMEs received instruction on how to select

and enter their codes onto the OpEval-2 ATSAT-CF.

Data Encoding. Once taught, each SME received a

complete set of audiocassettes, transcripts, and the

code and instructional manual. The audiotapes and

transcripts aided the SMEs in the identification of

departure clearance (DC) communication sets. Each

SME worked independently to identify and code the

efficiency and accuracy of communications. However,

they met on a weekly basis to discuss their encoding and

resolve any differences. Once the SMEs reached consensus, the data entry clerks received the final copy and it was

entered into the database for final analysis.

RESULTS

Changes in operational communication that may

have resulted from ADS-B/CDTI during OpEval-2

were evaluated from verbatim transcripts and digitized voice recordings provided by the TRACON

facility. Although requests for the inclusion of baseline

circuits during OpEval-2 were made during the planning of the event, none were conducted. Consequently, routine and OpEval-2 operational

communications could not be compared since the

baseline data necessary for comparison were not included as part of OpEval-2.
7

LINE HH MM SS HH MM SS Speaker Receiver MESSAGE COMMENT CODE

1 16 5 46 16 5 49 N123 ATC ONE SEVEN RIGHT POSITION

HOLD FOR NOVEMBER ONE

TWENTY-THREE

2 16 6 38 16 6 40 ATC N456 NOVEMBER FOUR FIFTY-SIX

CONTACT DEPARTURE

3 16 6 40 16 6 41 N456 ATC FOUR FIFTY-SIX

4 16 7 3 16 7 6 ATC N123 NOVEMBER ONE TWENTYTHREE RUNWAY ONE SEVEN

RIGHT TURN RIGHT HEADING

ONE NINER ZERO CLEARED

FOR TAKE-OFF

5 16 7 7 16 7 11 N123 ATC CLEARED FOR TAKE-OFF

RUNWAY ONE SEVEN RIGHT

HEADING ONE NINER ZERO

NOVEMBER ONE TWENTYTHREE

6 16 8 28 16 8 30 ATC N123 NOVEMBER ONE TWENTYTHREE CONTACT DEPARTURE

7 16 8 31 16 8 31 N123 ATC ONE TWENTY-THREE

Figure 5. Example of a Transcript.

Table 1. Pilot-Managed Departures Executed with ADS-B/CDTI

Time (in seconds)

Source (a) N Messages (b) TOF (c) FOT (d) ROT (e) TLC N Sets

Time of Day

Day 6.38 (2.83) 2.47 (.64) 15.44 (7.06)* 135.81 (22.04) 201.00 (097.38)* 16

Night 5.13 (1.31) 2.19 (.53) 10.75 (2.02) 146.00 (12.26) 168.50 (045.24) 16

Spacing Interval

Short Spacing 5.69 (1.70) 2.51 (.68) 14.12 (6.05) 128.81 (18.39)* 170.81 (080.46) 16

Long Spacing 5.81 (2.76) 2.15 (.44) 12.06 (5.17) 153.00 (06.43) 198.69 (072.14) 16

* statistically significant at p ≤ 05

Table 2. Controller-Managed Departures Executed without ADS-B/CDTI

Time (in seconds)

Source (a) N Messages (b) TOF (c) FOT (d) ROT (e) TLC N Sets

Time of Day

Day 7.57 (1.72) 2.34 (.11) 17.71 (4.07) 60.14 (10.29) 213.29 (118.42) 7

Night 6.83 (1.72) 2.21 (.58) 14.67 (3.20) 77.17 (39.89) 184.00 (050.97) 6

Spacing Interval

Short Spacing 8.67 (1.37)* 2.14 (.28) 18.67 (4.32) 58.17 (06.05) 224.50 (128.58) 6

Long Spacing 6.00 (0.58) 2.40 (.45) 14.29 (2.06) 76.43 (37.12) 178.57 (041.68) 7

* statistically significant at p ≤ 05
8

The local controller and pilots on the flight deck

exchanged 278 messages. These messages comprised

45 departure clearance (DC) communication sets

(one for each departure) that began with the pilot

checking in (e.g., initial contact) and ended with a

pilot acknowledging the hand-off (e.g., transfer of

communications to departure control). For all practical purposes, the number of DC communication sets

was approximately equal for day (n=23) and night

(n=22) departures using a short or long spacing interval. Analyses were performed for pilot executed departures conducted with ADS-B/CDTI (32 departures)

and for the controller-managed departures that were

conducted without ADS-B/CDTI (13 departures).

Efficiency of Communications. As mentioned earlier, the measures of communication efficiency for the

departure communication sets were (a) number of

messages (N messages) and (b) mean time on frequency per message (TOF). To evaluate the effects of

CDTI on communication efficiency during departure spacing, a Time of Day (Day, Night) by Spacing

Interval (Short, Long) Analysis of Variance (ANOVA)

was performed on the local control communicationdata for Flight Periods 1-5. The results were evaluated

using a criterion level set to p =.05. Presented in Table

1 and Table 2 are the mean (M) and standard deviation (SD) for each dependent variable.

The results of the separate ANOVAs revealed that

when pilots executed ADS-B/CDTI departures, it did

not matter whether they flew with a short or long

spacing interval [F(3,28)=2.40] or if they flew during

the day or night [F(3,28)=2.37] (see Table 1 columns

a and b). When ADS-B/CDTI departures were conducted, pilots were instructed to say “Mark” as an

indication that they were starting to move down the

runway. These additional transmissions may have

added to the number of messages transmitted and

inflated the time data. However, upon re-analysis, the

results did not change and only decreased the M and

SD by a fraction of a second.

When ADS-B/CDTI was not in use, as was the case

for controller-managed departures, the results revealed

an increase in workload for controllers as indicated by

more messages exchanged between local controller

and the pilots on the flight deck during the short (but

not long) spacing interval [F(1,12)=16.54] (see Table

2 column a). Time of day did not exert a statistically

significant effect on controller workload when measured by either the number of messages exchanged or

their mean duration (Table 2 columns a and b).

Duration Measures for Departure Clearance Communication Set. The duration measures of DC Communication Sets were c) total frequency occupancy

time (FOT); (d) runway ownership time (ROT); and

(e) total time that the aircraft was under local control

(TLC). As shown in Table 1 for the time of day factor,

the results indicated that for pilot-managed departures using ADS-B/CDTI, in addition to an increase

in radio frequency occupancy time per departure

(column c) [F (1,28)=4.95], longer periods of time

were spent under local control (column e) during day

but not night operations [F (1,28)=4.24]. For the

spacing interval factor, flight crews executed the takeoff clearance in less time (column d) when they were

on a short, rather than long, spacing interval [F (1,28)

= 19.26]. The absence of any significant interaction

between spacing interval and time of day for the pilotmanaged departures suggests that spacing interval

alone accounted for the more than 20-second savings

in transfer from local to departure control.

Displayed in Table 2 are the means and standard

deviations of the duration measures for controllermanaged departures conducted without ADS-B/

CDTI. The results of the ANOVA revealed no statistically significant differences in workload for the time

of day factor, the spacing interval factor, or their

interaction.

Communication Problems. Using transcripts and

cassette tapes, SMEs identified communication problems such as inaccuracies, procedural deviations, and

non-routine transactions involving misunderstandings or other problems related to information transfer. Illustrated in Figure 6 are several examples. While

these types of problems can contribute to frequency

congestion and increase workload, they do not necessarily lead to operational errors or incidents.

An evaluation of the 278 messages involving the

departure spacing application for ADS-B/CDTI revealed that approximately 2% contained communication problems involving five departures. When ADS-B/

CDTI was in use, there were two departures in which the

aircraft call sign was either misstated or incorrect and one

departure in which the pilot requested a “say again.”

As seen in Figure 6, the controller detected a

communication problem of either a misspoken call

sign or the potential for a stolen clearance. The problem was quickly resolved through the exchange of two

additional messages. In another departure clearance

readback, the pilot transposed the assigned heading

with the numbers in the call sign, quickly discovered

the problem and restarted the readback. “NOVEMBER THREE TEN OR UH NOVEMBER ONE

TWO THREE TO THREE TEN ON A HEADING

CLEARED FOR TAKE-OFF THREE FIVE LEFT.”

The last communication problem involved a pilot

request for the controller to repeat the preceding
9

ADSB IN USE

Speaker Incorrect Call Sign

1. NOVEMBER ONE TWENTY-THREE ... CLEARED FOR TAKEOFF

PILOT 2. ... CLEARED FOR TAKEOFF ... NOVEMBER ONE TWENTY-FIVE

CONTROLLER 3. AND VERIFY THAT WAS ONE TWENTY-THREE

PILOT 4. UH NOVEMBER ONE TWO THREE UH CLEARED FOR TAKEOFF ...

Call Sign Midstream Correction

CONTROLLER 1. NOVEMBER ONE TWENTY-THREE ... TAXI POSITION AND HOLD

PILOT 2. POSITION HOLD ... NOVEMBER ONE TWENTY-THREE

CONTROLLER 3. NOVEMBER ONE TWENTY-THREE ... TURN LEFT HEADING THREE ONE

ZERO CLEARED FOR TAKEOFF

PILOT 4. NOVEMBER THREE TEN OR THREE ONE THREE TO THREE TEN ON A

HEADING CLEARED FOR TAKEOFF ...

Say Again

CONTROLLER 1. NOVEMBER ONE TWENTY-THREE RUNWAY

PILOT 2. SAY AGAIN FOR NOVEMBER ONE TWENTY-THREE

CONTROLLER 3. NOVEMBER ONE TWENTY-THREE DISREGARD HOLD SHORT ...

PILOT 4. HOLDING SHORT ...

ADS-B NOT IN USE

Speaker Call Sign Midstream Correction

CONTROLLER 1. NOVEMBER ONE TWENTY-THREE ... CORRECTION DECEMBER ONE

TWENTY-THREE ... TAXI INTO POSITION AND HOLD

PILOT 2. POSITION AND HOLD ... DECEMBER ONE TWENTY-THREE

Call Sign Midstream Correction

CONTROLLER 1. DECEMBER ONE TWENTY-THREE ... TAXI INTO POSITION AND HOLD

PILOT 2. POSITION AND HOLD ... DECEMBER ONE TWENTY-THREE

CONTROLLER 3. NOVEMBER CORRECTION DECEMBER ONE TWENTY-THREE ... CLEARED

FOR TAKEOFF

PILOT 4. CLEARED FOR TAKEOFF ... DECEMBER ONE TWENTY-THREE

Figure 6. Examples of Communication Problems and Their Resolutions
10

transmission. When ADS-B/CDTI was not in use,

there were several occasions when the controller referred

to the aircraft with the correct flight numbers but with

the wrong company name. Upon self-discovery of the

problem, the controllers restated these transmissions

using the correct call sign as shown in the lower half of

Figure 6. No additional transmissions were required to

clarify the misstated call signs since they were identified

and corrected midstream by the controllers.

DISCUSSION

The analysis of voice communications from the departure spacing application suggests that neither the

pilots who used the ADS-B/CDTI nor the controllers

who applied current ATC procedures without the benefit of ADS-B information experienced a notable increase in workload. In particular, when pilots executed

the ADS-B/CDTI assisted departures, neither the number nor duration of the messages exchanged between the

flight deck and local control resulted in inefficient

communications. In fact, the procedural changes instituted for the departure spacing application eliminated

the instruction for the pilot to “taxi into position and

hold, ” without a decrease in total radio frequency

occupancy time per departure. Unfortunately, OpEval2 did not include conditions that would provide comparisons between this procedure and those used currently

at the local control position. Consequently, a need exists

for research to document the implications of eliminating

the “position and hold” procedure on aircraft movement

and airport capacity.

The findings from the duration measures indicated

that pilots succeeded in using ADS-B/CDTI information to adjust their departure spacing interval from

4.5 to 6.0nm. Importantly, these specific spacing

distances, as defined in the scripts and on pilot flight

cards, were well coordinated and orchestrated. In fact,

controllers managed the traffic in a manner that fully

supported the local operation and the flight period

spacing requirements to the extent possible. At times

the operational priorities restricted the ability of the

controllers to allow full conformance to scripted patterns, planned spacing intervals, or both. Fortunately,

these occurrences were minimal.

Once the tower is provided with a display that

includes ADS-B information, the departure spacing

application will provide local controllers with a means

of issuing take-off clearances that could specify variable wake-vortex minimums between aircraft equipped

with ADS-B/CDTI. With the availability of an ADSB/CDTI system onboard their aircraft, pilots could

accept these clearances and begin their take-off roll at

these prescribed minimums. The distance (or time

interval) used to space aircraft for departures vary with

the category of aircraft (Category I, Category II, or

Category III), same runway versus intersecting or

parallel runways, the potential for wake turbulence,

and other factors.3

 ADS-B/CDTI systems developers

could include these parameters as part of their algorithms and further optimize runway use with the

added benefit of increased safety.

At noted earlier, controllers used standard phraseology to perform the departure spacing task (e.g.,

cleared for take-off) without specifying the pre-determined spacing interval to be established or maintained between aircraft. For some of the other

applications that were evaluated, the controllers’ inclusion of traffic flight identifiers was in accordance

with FAA Order 7110.65, where “additional information” is allowed at the end of traffic information

messages.4

 The controllers received flight strips that

denoted the type of ADS-B equipage installed on the

participating aircraft. Not surprisingly, on several

occasions, pilot-use of the traffic flight identifier

migrated to their communications with the local

controller. For example, “TOWER {Ownship’s}

HOLDING IN TURN BEHIND NOVEMBER

ONE TWENTY-THREE, ” and “TOWER

{Ownship’s} READY BEHIND ONE NINER.”

During preparation for this event, facility, regional and

headquarters personnel focused on developing a phraseology and procedural environment that would address the

issues noted in OpEval-1. This included a prototype phraseology that included the call signs of participating aircraft in

all traffic calls and met the basic requirements of the

operational environment. Unfortunately, a comprehensive

evaluation of the operational concept for the departure

spacing application and phraseology was not attainable

during this operational event. Not surprisingly, significant

work remains to address phraseology issues and safety

concerns with flight crews occupying a runway for an

extended time.

The lack of standardization in voice communications procedures was one of the operational concerns

noted by the subject matter experts. To realize the full

3

 See FAA Order 7110.65M Air Traffic Control Section 8, Spacing and Sequencing for FAA authorized air traffic control

procedures and phraseology for use by personnel providing air traffic control services.

4

 FAA Order 7110.65M Air Traffic Control Section 4 Para. 2-4-20 Aircraft Identification NOTE: “Air carrier and other civil

aircraft having FAA authorized call signs may be pronounced using single digits if necessary for clarity.”
11

benefits from ADS-B/CDTI, a more concise lexicon

of air traffic phraseology would be helpful. A consideration of a data link for more routine communications, similar to what occurs for pre-departure

clearances, would help keep the voice channel available should problems occur. Although pilots are encouraged to use the phraseology outlined in the

Aeronautical Information Manual (FAA 2001) and

FAA Order 7110.65 The Handbook of Air Traffic

Control (FAA 2000), they are not required to use the

phraseology. Air traffic controllers and pilots would

benefit from precise, consistent, and standardized

communications. Communication capability, pilot

and controller workload, and system capacity all benefit from concise, standardized phraseology.

In addition to the phraseology and communication

analysis, the subject matter experts expressed an operational concern that centered on the installation and

commissioning of ADS-B at various airports. In particular, the pilot SME felt strongly that operational,

procedural, and human factors considerations involving ADS-B/CDTI use for pilot-managed departures

task and its affects on airport capacity, airport surface

movement, and safety need a thorough evaluation. In

particular, research is needed to determine the affect

of increased “runway ownership time” on system

safety and airport capacity. Specifically, runway ownership time represents the time the flight crew expends

maneuvering the aircraft onto the runway, determining when the specified distance is achieved between

Ownship and the preceding aircraft, and executing

the take-off clearance. During this time, the runway is

active and, therefore, unavailable to the controller for

other vehicle movement or aircraft operations (e.g.,

runway crossing and landing).

More research is required to determine the affect of

increased “runway ownership time” on airport movement, capacity, and safety during departure spacing.

If the ADS-B/CDTI departure spacing application is

implemented then a clear understanding is needed of

the roles, responsibilities, procedures, and phraseology for pilots and controllers who use it.

REFERENCES

Federal Aviation Administration. (2000). Air Traffic

Control (7110.65M). Washington DC: U.S. Government Printing Office.

Federal Aviation Administration. (2001). Aeronautical

Information Manual. Washington DC. U.S. Government Printing Office.

Guidance for Initial Implementation of Cockpit Display of

Traffic Information. Washington DC: RTCA, Inc.

(February 1998). (Prepared by SC-186). RTCA/

RTCA/DO-243.

Minimum Aviation System Performance Standards for

Automatic Dependent Surveillance Broadcast (ADSB). Washington DC: RTCA, Inc. (February 1998).

(Prepared by SC-186). RTCA/RTCA/DO-242.

Joseph, K.M., Domino, D. Battiste, V., and Bone, R.

(in progress). A Summary of Flightdeck Observer

Data from SafeFlight 21 OpEval-2. Federal Aviation Administration, Office of Aerospace Medicine Technical Report, Washington, DC.

Minimum Aviation System Performance Standards for

Automatic Dependent Surveillance Broadcast (ADSB). Washington DC: RTCA, Inc. (February 1998).

(Prepared by SC-186). RTCA/DO-242.

Morrow, D.G., Lee, A., and Rodvold, M. (1990).

Analysis of routine pilot-controller communication. In: Managing the Modern Cockpit: Third

Human Error Avoidance Techniques Conference

Proceedings. Warrendale PA: Society of Automotive Engineers, Inc.

Operational Evaluation Coordination Group (2000).

CAA/FAA/Safeflight21 Phase 1 - Operational

Evaluation Final Report. www.faa.gov/safeflight21/

orv/opeval_1/index.html

Operational Evaluation Coordination Group (2001).

CAA/FAA/Safeflight21 Operational Evaluation-2

Final Report. www.faa.gov/safeflight21/orv/

opeval_2/index.html

Prinzo, O.V. (2001). Innovations in Pilot Visual Acquisition of Traffic: New Phraseology for Air Traffic

Control Operational Communication. Federal Aviation Administration, Office of Aerospace Medicine Technical Report DOT/FAA/AM-01/19,

Washington, DC.

Prinzo, O.V., Britton, T.W., and Hendrix, A.M. (1995).

Development of a Coding Form for Approach Control/Pilot Voice Communications. Federal Aviation

Administration, Office of Aerospace Medicine

Technical Report DOT/FAA/AM-95/15, Washington, DC.
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