3.3.4 Request. Figure 8 presents the percentage of
Request communication errors. Generally, request
communication errors clustered around airspeed,
route/position, and approach topics. Pilots who flew
in airspace controlled by TRACON-I displayed more
request communication errors related to airspeed
(48%) and approach (24%) topics; pilots who flew in
TRACON-2 airspace had more request communica-
tion errors pertaining to airspeed (50%) and ap-
proach/departure (38%) topics; and pilots who flew
in airspace controlled by TRACON-3 made more

70

An Analysis of Approach Control/Pitot Voice Communications

request communication errors involving airspeed (36%)
and route/position (36%) than approach (21%) topics.

For TRACON-1 controllers, 54% of the request
communication errors pertained to airspeed, with the
remaining communication errors equally distributed
across the other topics. TRACON-2 controller re-
quest communication errors occurred only in air
speed (68%) and approach (32%) topics. Finally, the
majority of TRACON-3 controller request commu-
nication errors were in altitude (53%) and route/
position (24%) topics.

60

20

30 [----.-

qm TRACON-1: Pilot
CITRACON-2: Pilot
ma TRACON-3: Pilot

E3TRACON-1: Controller
EXTRACON.-2: Controller
&ITRACON-3: Controller

Figure 7. Proportion of Aviation Topics Within the Advisory Speech Act That Contained
Communication Errors Made by Pilots and Controllers at Each TRACON Facility

15


An Analysis of Approach Control/P:lor Voice Communications

Prinzo, O. V. & Britton, T. W. (1993). ATC/Pilot Voice
Communications - A Survey of the Literature. Wasb-
ington, DC: FAA Office of Aviation Medicine
Report, DOT/FAA/AM-93/20.

Prinzo, O. V. & Britton, T. W (1994). A Taxonomic
Analysis of Terminal Air Traffic Control/Pilot
Communications. In: Aerospace Systems Integra-
tion Through Technology and Training (SP-1051),
pp. 71-75. Warrendale, PA: Society of Automo-
tive Engineers, Inc.

Prinzo, O. V., Britton, T. W., & Hendrix, A. (1995).
Development of a coding form for approach controlf
pilot voice communications. Washington, DC: FAA
Office of Aviation Medicine Report. DOT/FAA/
AM-95/15.

Searl, J. R. (1969). Speech Acts. London: Cambridge
University Press.

32


An Analysis of Approach CencraliPilar Vaice Communications

TABLE 4. Types of Communication Errors in ATC/Pilct Transcripts

Communication Error
Types

Definition

Message Content Errors

Grouped

Sequential

(Non-grouped)

Omission

Substitution

Transposition

Excessive
Verbiage

Partial Readback’

Delivery Technique Errors
Dysfluency

Misarticulation

Grouping of numerical information contrary to
paragraph 2-85, FAA Order 7110.65G.

Failure ‘c group numbers in accordance with
paragraphs 2-37, 2-88, 2-90, and non-use of the
phonetic aiphabet in accordance with paragraph 2-
84, FAA Order 7110.65G.

Leaving out number(s), ietter{s), word(s), prescribed
in| communication requirements in FAA Order
7110.65G.

Use of word(s) or phrases(s) in iieu of
communication outlined in FAA Order 7110.65G
(e.g., “verify altitude” vs. “say altitude”).

Number(s} or word(s) used in the improper order
{e.g., "Universal six forty-five" instead of “Universal
five forty-six").

Adding word(s) or phrase(s) to communication
outlined in FAA Order 7110.65G, and = the
communication suggested in the Airman’s Informa-
tion Manual (e.g., "Universal the number one airline
six forty-five").

Pilot report or readback that does not include
specific reference to a topic subject (i-e., altitude
topic “out of six for four” would be recorded as a P).

Pause(s}, stammer(s), utterance(s), that add no
meaning io the message (e.g., “uh," “ah,” or "OK"
when noi used as a genera! acknowledgment.

Improperly spoken words {i.e., slurs, stutters,
mumbling, etc.).

* Note: A verbatim readback of a controtier’s instruction or advisory would not be recorded as a P, nor would a readback

containing a general acknowledgment and the aircraft identifier,


An Analysis of Approach Control{Pilot Voice Communications

Mmmifesding
. Exp Altitude

KB AppsDep.
CATS
ORV Position

wa [---------------P}-------------------------- We --4

ame Traffic

. Ul

_

Figure 12. TRACON-1: Distribution of Controller Advisory Communication Errors

YN *

ped
‘mmam Tieading,
Speed
OA App Dep.
we [o----------..--------4 _ o 2  - - LESSER Pesition —
ws fo. .------------------ Fee e+ -

we p-pa-------- 0-2-2. ------]----------- ao eee ee wees

m [-Fo------------------4 . -- veeeee

Ui el

SON OS

Figure 13. TRACON-1: Distribution of Controiler Request Communication Errors

%, 2, Ae,
My ee _ %,

om
% %,

3.4.1.3 Request. As shown in Figure 13, most of 3.4.2 TRACON-1 Facility (Level 5): Pilot

the airspeed communication errors resulted from sub- | Communications

stitution (24%) and excess verbiage (22%). Speaking 3.4.2.1 Instruction. The samc analyses were per-
numbers in a grouped format contributed an 2ddi- formed on pilot instruction transmissions (i.e.,
tional 10%. For example, “...and ah just verify that readbacks of controller generated transmissions); the
you’re at a hundred and ninety on the speed....” results are displayed in Figure 14. The Instruction



TABLE GF CONTENTS

SECTION
1.0 INTRODUCTION...
2.0) METHODS onn...cccseeeesccssssssssseneecesssssnesescsessssuanseseeseesasausceceessassuuesecsessnsousssseesssnnnasegeessesssartecesessniness 7
24 Materials 0... .escecsessessesssssessecneeneess sseveeesesarsnessesseesecsssnseaceresessneaneseeaceacssetveresceseeseeeacsneeneeey 7
2.1.1 Aviation Topics Speech Act Taxonomy Coding Form sisssssssse-scssssssscusntsnssnee 7
2.1.2 Audiotapes 0... ceccssssssssesssssussessssaeecsnsnesccssssensnnesssnneeecssssesesisneessnnecsesaneeessenseets 8

3.0

40
5.0

6.0

2.2 Procedure ..

RESULTS, ooo. eeceseee eee ee eceseeescesenseeeacsseveneeesssanesseeescecsnecesscsssuassnararssausanseasesusaenanetegeessueasaesnessaeses li
3.1 Data Analysis... .csccssssessceceeseseesssnssessesesessasccneecsseessesnesesereeassnseeseesensceseseaaseesssesnauessenees i

3.2 Analysis of Speech Act Communication Errors ..

3.3 Analysis of Aviation Topic Communication Erroms «.....1..sc.ssssecsesssssesssesesteccsnsesseeeseeessnsees 13

3.4 Analysis of Communication Error Types .........ssssssssssessessnssnesesetentsnessnensassaeeseessseeacssseeness 1G:

3.4.1 TRACON-I Facility (Level 5) Controller Communications ...........cceceeeeeeeees 18
3.4.2 TRACON-I Facility (Level 5) Pilot Communications .........ccsecseseeecetcneseeeees 19
3.4.3. TRACON-2 Facility (Level 5) Controller Communications ..........c.ccccsessesseereeee 22
3.4.4 TRACON-2 Facility (Level 5) Pilot Communications.........ccssssssecseceesessessneenes 24
3.4.5 TRACON-3 Facility (Level 4) Controller Communications ......c..c.ccsceeseeeceeseeees 25
3.4.6 TRACON-3 Facility (Level 4) Pilot Communications .0.....ccccsscseessescesseseeeeeees 27

DISCUSSION ....e.sescsssscsscoseessseseesessesssssusansnssenesneeceeecanesesnsacsnssecssssesesueasseesesecssessesesseueecseventavanees 29

CONCLUSIONS .0..escscececssseesscctsesesnsseseseeseaussesecosscsnssesnseagqecessesussesssusseseenanenuquenegeeneneeseaeneeesneneass 31

REFERENCES

APPENDICES

Appendix A. caccnssstmnsuninetstinintsieiimeintntieieintntsnaneueieienntntinatetsnenenensnassn A3

Appendix B .cccsscsssccssusesessssusesssesasstnnetissetneetnsesussetnessesssistsisestse suuestisansuanetnseeaneeeet B-l



An Analysis of Approach Control/Pilot Voice Communications

TRACON-2, it pertained to traffic; and for TRACON-
3, it involved both traffic and route/position Adviso-
ries. Pilots experienced the most difficulty responding
to altitude Advisory communications. Their altitude
communication errors generally fel] into 3 types:
excess verbiage, partial readback, and grouped format.
Only the pilots at the TRACON-2 facility made more
substitution communication errors involving traffic
Advisory information.

Only the TRACON-i and TRACON-3 facilities
had Request communication errors. The form of their
errors were facility specific. The preponderance of
TRACON-1 controllers’ communication errors cen-
tered around airspeed, and involved substitution,
excess verbiage, and grouped format. Although “...and
ah just verify that you’re at a hundred and ninety on
the speed ...” conveys the same intended meaning as
“say airspeed,” it requires substantially more time to
transmit. Additionally, the message is wordy and
contains both grouped and omission communication
errors. “...and ah just verify that you're at a hundred
and ninety on the speed...” is more likely to be
misunderstood or misinterpreted than “say airspeed”
if the transmission is clipped or garbled. Pilot trans-
missions also contained grouped format, partial
readback, and excess verbiage involving airspeed. At
TRACON-3, controllers made the most communica-
tion errors involving altitude. Their errors stemmed
from substitution, excess verbiage, and grouped for-
mat. Pilots’ route/position and approach/departure
transmissions contained excessive verbiage.

It is intuitively obvious that excess verbiage length-
ened the amount of time required to transmit, under-
stand, and respond to a message by pilots and
controllers. Yet, an examination of the verbal content
of requests revealed that requests such as “say again,”
ied who was on frequency, who was the

often clari
incended recipient of a transmission, and improved
overall understanding. However, these additional
communications also contributed to frequency con-
gestion by increasing the number of transmissions
needed to create a mutual understanding (or common
ground) of the pilor’s intentions. Without these addi-
tional communications, the pilot and controller would

not have reached a mutual belief, called the “ground-
ing criterion,” that the receiver had understood what
the speaker meant (Clark & Schaefer, 1989; Clark &
Wikes-Gibbs, 1986). These types of errors can result
in trade-offs berween frequency congestion and fai)-
ure to reach a common understanding; both of which
can lead to problems.

Effective and accurate communications are crucial
to air safety. As aircraft approach their destination
airport, they converge and operate under reduced
separation minima'!, Commercial aircraft may be
flying at speeds in excess of 380 knots during their en
route phase of flight and reduce eo speeds of 180 knots
(i.e., traveling at speeds greater than 3.5 nautical miles
per minute) in the terminal environment. Under these
circumstances, there is little margin for error. When
ambiguities arise from poorly constructed messages, it
is critical for pilots and controllers to transfer infor-
mation to one another as quickly and as efficiently as
possible so as to maintain or re-establish a common
ground of understanding and to maintain their mar-
gins of safety.

If air safety is dependent upon efficient and accu-
rate communications, then we should be able to
measure how safe the system is from a simple math-
ematical equation. For example, safety could be deter-
mined from an equation that uses “total number of
faulty communications” as the numerator, and “total
number of communications,” or “total number of
operations,” as the denominator in a simple ratic. In
such a case, the concfusions drawn by Cardosi (1993)
and Morrow and co-authors (1993) are borne out:
Miscommunications seem to be rare events and spo-
ken communications do not present a problem to air
safety (but then again, operational errors, pilot devia-
tions, and NMACs also are rare when total number of
operations serve as the common denominator). On
the other hand, if an equation is developed that
reflects the number of communication errors occur-
ring per hour, then the data are more startling. Cardosi
(1993) reported that 27 communication errors were
found in 47 hours of ARTCCs’ recorded radio com-
munications. This translates to about 13 communica-
tion errors per day; or about 1 error every 2 hours.

‘In the terminal environment, separation minima are 3 miles and 1,000 feet and within the en route envitonment it is 5 miles and 2 thousan:
2

feet. However, sec FAA Order 7110.65} Par.5-5-3d-f for exceptions.

30


An Analysis of Approach Controi!Pilot Voice Communications

3.4 Analysis of Communication Error Types

The percentage of the types of communication errors
associated with each aviation topic within speech act
categories was computed for each TRACON facility and
speaker. For example, the distribution of communica-
tion error types within the Address speech act made by
controllers at TRACON-1 equal 100 percent. To mini-
mize clutter, communication error types equaling less
than 1% of each aviation topic classification were not
included in the figures.

The analyses of Address communication errors for the
3 TRACON facilities are presented collectively. As
shown in Figure 9, the majority of controller message
content errors resulted from omission of number(s),
letter(s), or word(s) contained in the receiver address
(ie., an aircraft call sign). Substitution of “oh” for “zero,”

70

“nine” for “niner” as part of an aircraft call sign and other
similar switches occurred, although infrequently. Addi-
tionally, there were problems in delivery technique, as
noted by controllers generally adding pause(s),
stammer(s), “ub,” “ah,” or “OK” to the receiver call sign.

As shown in Figure 10, the majority of pilot commu-
nication errors resulted from pilots omitting a portion of
their aircraft call sign when communicating. Although
controllers often use a pilot's voir. quclities and radar
displayed call sign to aide in speaker identification (when
less than full speakex address t* provided), pilots should
use their full call sign to avoid confusion. Use of the full
call sign when communicating with ATC would elimi-
nate additional transmissions made by the controller to
determine the speaker's address. Ne other Address com-
munication errors were notable.

N

3]

aus

as

WS

<2

3S

ue

oe

OER

30

ROE

au

20

se

POSS

PSSe5e5250

Re
3

MS

~
“aS

SKS

2

05

OOO.

x

xX

ox,

y
%
%

S
%,
&

mm TRACON-1: Pilot
(CITRACON-2: Pilot
gmTRACON-3: Pilot

E|TRACON-2: Controller
EXTRACON-2: Controlter
EITRACON-3: Controller

Figure 8. Proportion of Aviation Topics Within the Request Speech Act That
ContainedCommunication Errors Made by Pilots and Controllers at Each TRACON Facility

16


An Analysis of Approach Controlf Pils: Voice Communications

25%
= imp Heading
= T3Speed
= CEAppDep.
= A
20% f4.-------..--- _ 2. LSE RePosition
i
15% } -F4-- -- - wee eee eee Hee ens a
= Ry
E
10% -fy-- - ante re eee ee eee ee ee ence ee eee eee eee
sm |-foy..--...--------- 2 ------------ - --
: y
» LE Ei NI 3
& 3
7 a a
% %, es, ey ey

Figure 16. TRACON-1: Distribution of Pilot Request Communication Errors

due mostly to excess verbiage (17%), grouped format
(15%), and partial readback (11%). Additional alti-
tude errors resulted from dysfluency (4%), substitu-
tion (2%), and omission (1%). Approach/deparcure
errors were due to partial readback (11%), grouped
format (3%), dysfluency (3%), and omission (2%).

3.4.2.3 Request. As shown in Figure 16, pilor
Request communication errors involved grouped for-
mat (24%), partial readback (24%), and excess ver-
biage (20%) - more than omission (4%), substitution
(10%), or dysfluency (12%). Airspeed errors resulted
from grouped format, partial readback, and rarely
omission, substitution, or excess verbiage (1% each).
Approach/departure request communication errors
resulted from excess verbiage and dysfluency - more
than substitution or partial readback. Route/position
and heading communication errors were rare.

22

3.4.3 TRACON-2 Facility (Level 5): Controller
Communications

3.4.3.1 Instruction. As shown in Figure 17, 76%
of the controllers’ Instruction communication errors
resulted from omission within the heading (10%),
altitude restriction (10%), speed (20%), approach/
departure (21%), frequency (9%), and route/position
(6%) aviation topics. Only radio frequency errors
resulted from a grouped format (8%). Substicution,
excess verbiage, and dysfluency had only a minor
impact on: the remaining Instruction aviation topic
communication errors.

3.4.3.2 Advisory. Figure 18 displays the distribu-
tion of controller Advisory communication errors, In
this analysis, omission (22%) and excess verbiage
(56%) predominate and 65% of all of che communi-
cation esrors involved traffic advisory. For example,


An Analysis of Approach ControliPilot Voice Communications

3.4.1 TRACON-i Facility (Level 5): Controller
Communications

A total of 2,878 lines of communication, each corre-
sponding to a single transmission, make up the data set
from which the accuracy of controller and pilot commu-
nication was determined. The data consisted of 3,777
controller communication elements and 3,626 pilot
communication elements.

3.4.1.1. Instruction, As shown in Figure 11, most of
the controllers’ Instruction communication errors re-
sulted from omissions (47%) and excess verbiage (22%).
Most radio frequency errors involved omissions (24%).
For example, controllers generally omitted the word
“point” ina radio frequency when handing off an aircraft
to an adjoining sector or facility tower. Airspeed errors
resulted primarily from omissions (9%) of the words
“knots” or “speed” as part of the airspeed? clearance.
Route/position and approach/departure errors each ac-
counted for 4% of the detected omission, and heading
and altitude errors each contained 3% of the total
Instruction communication errors.

Excess verbiage occurred most for airspeed (7%)
and radio frequency (5%) errors. Errors involving
heading, altitude, approach/departure, and route/po-
sition accounted for the remaining 9% of the Instruc-
tion communication errors. Although excess verbiage
rarely alters the meaning of a transmission, it can
increase frequency congestion by preventing others
from making transmissions.

3.4.1.2 Advisory. As shown in Figure 12, 2 mes-
sage content communication error types prevail: those
arising from omissions (31%) and excessive verbiage
(32%). Errors of omission involved runway informa-
tion (18%) and weather conditions (13%). Priraary
among runway errors was controllers failing to in-
clude the word “approach” as part of the advance
approach information'®. Excess verbiage was most
prevalent for route/position (13%), weather (8%),
ATIS (6%), approach/departure (5%), and traffic
(5%) information.

25%
A tam Beading
. exo Altitude
= OVAL Restrict.

we [----------.-------- A... ----..-----------4 CaSped ftw ee
H EDAppDep.
ri —1F requency
a T—3Rt/Position

15% }----------- -- 4 weee --- wee ee eee eee
H

w% f--------.-----------4 i - --- were ee ween neeee- -

S% - - - []------- -2 ee nee Ee ee eee eee

a HH L,

Yo, ey

Figure 11. TRACON-1: Distribution of Controller Instruction Communication Errors

> FAA Order 7110.65] Par.5-7214 states “Increase ot reduce toa specified speed ora specified number of knots.” For example, “Reduce speed

cwenty knots.,” and “Maintain onc eight zero knots.”

"’ Phrascalagy was evaluated in accordance with FAA Order 7110.65G Par. 4-72a): but see Advance Approach Information Par. 4-65.

18


5.0 CONCLUSIONS

The results suggest that controllers and pilots need
to improve their operational communication prac-
tices. The AIM provides pilots with an 8-page section
on radio communications and communication tech-
niques, which stress the importance of pilots and
controllers reaching the same understanding of their
transmissions. “Brevity is important, and contacts
should be kept as brief as possible, but the controller
must know what you want to do” (AIM, 1994, par 4-
31b). Pilots may be using omission and grouping as
strategies to create brief, yet concise ATC communi-
cations. However, these strategies could create mis-
communications and increase frequency congestion.
Using established communication procedures and prac-
tices could eliminate some ambiguity and confusion.

A reduction in the frequency of operational errors,
pilot deviations, and near midair collisions might be
attainable if piiots and controllers used standard com-
munication operational procedures and practices. t's:
example, standard communications, such as “say
speed,” “say altitude,” and “verify assigned altitude”
meet the requirement for brevity on the part of the
controller. Pilots need to reply only with “[one two
three] knots” or “[one rwo} thousand [three] hun-
dred.” Use of words such as “knots,” “speed,” “de-
grees,” “point,” “flight level,” and “runway” constrain
the possible meaning of communication elements in
a message. Controllers should practice transmitting
complete radio frequency, airspeed, and approach/
departure Instructions and be less verbose when deliv-
ering traffic 1nd route/position Advisories. Pilots
should practice constructing and transmitting alti-
tude information to air traffic control — and would
also benefit from additional practice in responding to
traffic Advisories.

The ATSAT was used to analyze ATC/pilot com-
munications from 3 TRACON facilities. It could be
used to evaluate the corimunications skills of individual
speakers and to identify the types and frequency of
communication errors in their transmissions. For ex-
ample, weaknesses in a pilot’s or controller's existing
communications skills could be identified by the ATSAT;
instruction, training, and practice then could be imple-
mented to correct the identified deficiency.

An Analysis of Approach Control/Pilot Voice Communications

31

6. REFERENCES

Airman’s Information Manual, Official Guide to Basic
Flight Information and ATC Procedures. (June,
1992). Washington, DC: U.S. Government Print-
ing Office.

Airman’s Information Manual, Official Guide to Basic
Flight Information and ATC Procedures. (1994).
Washington, DC: U.S. Government Printing Of-
fice.

Cardosi, K. (1993). An analysis of en route controller-pilot
voice communications. Washington, DC: FAA Of-
fice of Research and Development. DOT/FAA/
RD-93/11.

Clark, H. H., 8 Clark, E. V. (1977). Psychology and
language. New York: Harcourt Brace Jovanovich.

Clark, H. H., & Schaefer, E. F. (1989). Contributing to
discourse. Cognitive Science, 13, pp. 259-294.

Clark, H. H., & Wilkes-Gibbs, D. (1986). Referring as
a collaborative process. Cognition, 22, pp. 1-39.

FAA Order 7110.65 Air Traffic Control. (March, 1992).
Washington, DC: Air Traffic Rules and Proce-

dures Service.

Kanki, B. G., 8& Foushee, H. C. (1989). Communica-
tion as group process mediator in aircrew perfor-
mance. Aviation, Space, and Environmental Medi-
cine, 60, pp. 402-410.

Monan, W. P. (Mar., 1986, Nov., 1988). Human factors
in aviation operations: The hearback problem.
Moffett Field, CA: NASA Conrractor Report
177398.

Morrow, D., Lee, A. & Rodvold, M. (1993). Analysis of
problems in routine controller-pilot communica-
tion. /nternational Journal of Aviation Psychology,
3, pp. 285-302,

Morrow, D., Clark, H. H., Lee, A., & Rodvold, M.
(Nov., 1990). Collaboration in Controller-Pilor
Communications, Presented at the 1990 Meeting
of the Psychonomic Society, New Orleans, LA.

Morrow, D., Rodvold, M., & Lee, A. (1990). Nonroutine
transactions in controller-pilot communicazion. Un-
published manuscript.



3.3 Analysis ef Aviation Topic Communication
Exrors
The first set of analyses was performed to identify

how communication errors were distributed within

each speech act’s aviation topics. For example, the
previous analysis determined that 19% of the 444
communication errors made by pilots at TRACON-
1 involved Addresses. This set of analyses examined
how contreliers’ and pifots’ communication errors
were distributed in the speaker and receiver identifi-
cation. Thus, the percentages of communication er-
rors presented in this section were computed by
grouping the errors according to TRACON facility,
speaker, and speech act category.

100

An Anatysis of Approach Controlfi

3.3.1 Address. The data presented in Figus
clearly indicate that regardless of TRACON facil
approximately 80% of the Address communicat
errors made by controllers and pilots involved

cai] signs, and not sector! position names.
altogether surprising since aircraft call signs contain
muir alpha/numeric information and they are spoken
less frequently than cector addresses. Also, there are
only a handful of ATC sector names, which must be
learned, such as Tower, Terminal, and Center that are
prefaced with location or facility names and sector
functions (e.g., ground, local, departure, approach),
compared to the number of call signs assigned to daily

flights.

60

40

26

Speaker ID

Recerver ID

ma TRACON-E: Pitot
CATRACON.2: Pilot
GaTRACON-3: Pilot

ESTRACON-1: Controtier
@3FRACOD
GIFRACON-3: Controller |

Controticr |

Figure 5. Proportion of Aviation Topics Within

Communication Errors Made by Pilots

the Address Speech Act That Contained

and Controllers at each TRACON Facility



An Analysis of Approach Control/Pilot Voice Communications

TABLE 2. ATC / Pilot Transactional Communication Set

Trans-  Trans- Time Transaction Communication
action mission Participants Elements
1 1 03:32 Universal [Name] Approach, Universal Seven Forty-four, Leaving six
744 thousand five hundred, maintain three thousand,
information Echo
2 03:35 ATC Universal Seven Forty-four [Name] Approach, Roger,
descend and maintain two thousand, say airspeed
3 03:40 Universal Seven Forty-four, Speed two five zero
744
4 03:43 ATC Universal Seven Forty-four, Roger
2 5 04:14 ATC Universal Seven Forty-four, Turn right heading zero six zero
vector to final approach course
6 04:16 Universal Seven Forty-four, turn right heading zero six zero
744
3 7 05:11 ATC Universal Seven Forty-four, Traffic twelve o’clock one three

miles, westbound, Heavy Delta L ten eleven descending
through four thousand niner hundred to maintain four
thousand, expedite descent through three thousand

8 05:27 Universal Universal Seven Forty-four, Reducing speed to one niner
744 zero
4 9 05:56 ATC Universal Seven Forty-four, Turn left heading three four
zero
10 06:01 Universal Universal Seven Forty-four, Turn feft heading three four
744 zero
5 VW 06:27. ATC Universal! Seven Forty-four, Descend and maintain two
thousand
12 06:32 Universal Universal Seven Forty-four, Leaving three thousand
744 maintain two thousand
6 13 07:16 ATG Universal Seven Forty-four, Seven miles from outer marker,

maintain two thousand until established on the localizer,
cleared ILS runway three one right approach, reduce speed
to one seven zero until outer marker
14 07:22 Universal Universal Seven Forty-four, Cleared ILS runway three one
744 right approach, maintain two thousand until established on
the localizer, speed one seven zero unlil cuter marker

7 15 08:33 ATC Universal Seven Forty-four, Contact [Name] Tower one one
niner point one
16 08:37 Universal Universal Seven Forty-four, Tower one one niner point one

744



D

An Analysis of Approach ControliPilot Voice Comn:unications

15%

0%

CotAltieude
EZSIAppMep.
ESORtJPasition
cows
wesSight woe ee |
mes Traffic

Figure 25. TRACON-3: Distribution of Pilot Advisory Communication Errors

nice day” and “Two three point four good day” are
two examples of partial readback frequency errors.
The first example also contains a grouped format
error. Altitude errors resulted from substitution (4%)
and partial readback (8%). The phrase “down to” was
substituted for “descend to” in the readback of an
ATC instruction.

3.4.6.2 Advisory. As shown in Figure 25, most of
the pilot communication errors resulted from grouped
format (18%), substitution (13%), excess verbiage
(21%), and partial readback (22%). Communication
errors occurred to a greater extent within the aviation
topics altitude (49%), traffic (11%), route/position
(9%), and sighting (7%). Altitude communication
errors resulted from grouped format (16%), partial
readback (13%), excess verbiage (12%), dysfluency
(5%), and misarticulation (1%). For example, “...[call
sign] sir with you going through eighteen hundred”
contained grouped format, partial readback, and ex-
cess verbiage communication errors, The majority of
the traffic Advisory errors resulted from substitutions
(8%) like: “Gor the traffic,” “We're looking for him,”
and “...we’re looking for both those traffics....” Route/

28

position communication errors stemmed from excess
verbiage (5%), dysfluency (2%) and grouped format
(2%). For example, “...we're thirry-two and a half
miles north of [tower] uh with echo...” suggests that
pilots had some difficulty constructing and delivering
a position report. Speakers recognize thar most pre-
sentations have an ideal delivery — one that is fluent,
correct, and optimal for identification (Clark & Clark,
1977). If they foresee an unavoidable delay or inter-
ruption, they use “uh” and “um” ro warn addressees
about the size of the interruption. They use “uh” to
signal short interruptions, and “um” to signal more
lengthy ones.

3.4.6.3 Request. As shown in Figure 26, pilot
Request communication errors involved excess ver-
biage (36%), substitution (18%), and dysfluency
(18%), more than partial readback (15%), or grouped
format (9%). Route/position communication errors
(39%) resulted from excess verbiage (21%). dysfluency
(9%), partial readback (6%), and grouped format
(3%). Approach/departure Request communication
errors resulted more from excess verbiage (15%) than
substitution (6%), dysAuency (6%), partial readback


De

An Analysis of Approach Control{Pilor Voice Communications

18%

16%

0%

‘wus Heading
C=UAItitude
To7Speed
EDAppDep.
mam Sight
ama Traffic

Figure 20. TRACON-2: Distribution of Pilot Advisory Communication Errors

10%

a,
yO,

oe

14%

10%

8%

6%

‘maa Heading
7

CBApp/Dep.
(Frequency
CURL Position
tT. Code

4%
2%
0%
%y, % "a “ee
. * % ONY
Figure 21. TRACON-3: Distribution of Controller Instruction Communication Errors

3.4.5 TRACON-3 Facility (Level 4): Controller
Communications

3.4.5.1 Instruction. See Figure 21. Within the
Instruction speech act category most of the communi-
cation errors occurred within the aviation topics fre-

quency (29%), heading (16%), approach/departure
(16), and route/position (13%). Once again, many of
the errors resulted from excess verbiage (34%) and
omission (31%). Extra words were added to heading
(14%), approach/departure (5%), frequency (5%),


An Analysis of Approach Control/Pilot Voice Communications

TABLE 1. Pilot /Controller Communications as a Factor in Incidents During 1993-94

Type of Incident Total Number Number of incidents Percent of Incidents
With With
Communications Communications
Involved* Involved

Year of Incident 1993*

Operational Errors 747 205 27%

Pilot Deviations 1423 573 40%

Near Midair Collisions 255 38 15%
Year of incident 1994**

Operational Errors 476 122 26%

Pilot Deviations 794 327 41%

Near Midair Collisions 147 20 14%

*Total flight operations Jan-Dec 1983 = 142952693
“Total flight operations Jan-Oct 1994 =122669848

Citing the Cardosi example on page 3, “United
123, fly heading 090” was considered 1 element;
whereas, “United 123, turn left heading 090” was
counted as 2 elements because the pilot could turn right
by mistake.

Morrow and Rodvold (1993) analyzed terminal
radar approach control - pilot voice radio transmis-
sions using the speech act as a global unit of analysis
to examine communication as a collaborative process
between the controller and the pilot. A speech act
“Roughly corresponds to an utterance serving one dis-
course function” (Morrow, Clark, Lee, & Rodvold,
1990, p. 4). Morrow and Rodvold might have coded
the above mentioned transmission as follows: “United
123” might be coded as an address, and “Turn left
heading (or fly heading) 090” as a command.

Prinzo and Britton (1994) adopted the speech act
and aviation topic as basic units of analysis and would
have concluded that the transmission, “United 123,
Sly heading 090” contair.ed 2 speech acts and 2 avia-
tion topics. “United 123” would be coded as an
address that identified the recipient of the transmis-

sion, and “Turn left heading (or fly heading) 090°

‘Aircraft communication equipment malfunction is excluded.

would be coded as an instruction to the pilot to fly a
particular heading.

What do the communications research data indi-
cate? Morrowand co-authors’ (1993) analysis of ATC/
pilot routine and non-routine communications from
each of 4 level-5 TRACONs revealed that incorrect,
partial, or missing readbacks were infrequent events
when compared to daily communications. Cardosi
(1993) reported that 27 communication errors were
found in 47 hours of voice tapes analvzed from 8
different ARTCCs indicating that less than 1% of the
analyzed total transmissions that involved clearances
contained readback errors. Of the 3,576 ATC clear-
ances received, 3% were not acknowledged by the
pilot recipient, and an additional 2.7% required rep-
etition. Collectively, the data indicate that faulty
communication is rare when it is compared to the
total number of communications making up the ana-
lyzed sample.

While the base rate of communication errors is low,
the consequences might still be significant. But, with-
out the benefit or use of a standard metric and repre-
sentative measures, it was difficult to accurately


AN ANALysIs OF APPROACH ConTROL/PILOT VOICE COMMUNICATIONS

AND THE LORD SAID, “BEHOLD THE PEOPLE ARE ONE, AND THEY ALL
HAVE ONE LANGUAGE...COME, LET US GO DOWN AND THERE CONFUSE THEIR
LANGUAGE, THAT THEY MAY NOT UNDERSTAND ONE ANOTHER’S SPEECH.”

1.6 INTRODUCTION

Do spoken communications present a problem to
air safety? The answer depends, in part, on how the
question is framed. Various government agencies tra-
ditionally have inspected verbal communications as
they related to filed incident reports, whereas commu-
nications researchers have analyzed and described
non-eventful, routine verbal communications (Mor-
row, Lee, & Rodvold, 1993; Morrow, Rodvold, &
Lee, 1990; and Cardosi, 1993).

In operational error, pilot deviation, or accident
investigations communications often are reported as
an apparent weak link. Aviation investigators scruti-
nize preliminary safety reports and obtain additional
information, as needed, to determine if Federal Avia-
tion Regulations (FAR) were violated, and to reporc
the factors underlying each certified incident. For the
investigator, the total number of communications or
operations that occur on a daily basis may be neither
important nor particularly interesting; that an inci-
dent report was filed and an investigation undertaken
is sufficient.

What do the investigation data indicate? As shown
in Table 1', communications problems were cited as
causal or contributing factors in approximately 27%
of the confirmed operational errors, 40% of the pilot
deviations, aud 15% of the near midair collisions
(NMAC5) reported in 1993 and 1994. Although the
total number of each type of incident has decreased in
1994 from 1993 levels’, the percentage of incidents with
communications involved appeared to be constant.

— Genesis 11:6-7

Air traffic control specialists (ATCS) and pilots
have implicated faulcy communications in airspace
incidents reported to safety investigators. Thirty-six
percent of the total number of full-form incident
Aviation Safety Reporting System (ASRS) reports
filed by pilots and controllers between 1988 and 1991
listed faulty communications as contributing or causal
factors in airspace incidents. Collectively, the ASP-
100 and ASRS data indicate that faulty communica-
tion is a significant factor in safety related incidents.

Unlike investigators who examine one incident at
a time, communications researchers rely upon large
amounts of information from many sources to draw
generalized conclusions or describe a typical event.
For these researchers, the total numbers of communi-
cations or operations that occur on a daily basis are
important and interesting data for analysis. One im-
Portant step in such analyses is the development of a
framework or methodology for analyzing aviation-
based communications. For example, Cardosi’s (1993)
analysis of Air Route Traffic Control Center (ARTCC)
controller-pilot voice communications focused on
message complexity. Message complexity was defined
as the number of separate elements contained in a
single transmission.

Each word, or set of words, the controlier said that
contained a new piece of information to the pilot, and
was critical to the understanding of the message was
considered to be an element. An element could be
considered as an opportunity for error.

~pp. 3

‘The data presented in Table 1 were obtained from the operational error, pilot deviation and neat midair collision databases maintained by

the FAA Office of Safery Information and Promotion {ASP-100).

"Ic is unlikely that the number of each type of incident for the first 9 months will double in the remaining 3 months of the calendar year.
> The words “Air traffic contro! specialist,” “controller,” and “ATCS” will appear interchangeably in this document to refer to the individual

(8) authorized to provide air traffic control services to pilots.



An Analysis of Approach Control/Pilot Voice Communications

3.3.2 Instruction. Figure 6 reveals that, for pilot
transmissions, the majority of the identified Instruc-
tion communication errors involved heading (28-
31%), radio frequency (16-26%), air speed (1-22%),
or altitude (13-21%) information. For controllers,
the majority of the identified communication errors
involved radio frequency (16-32%), air speed (0-
26%), heading (12-20%), or approach/departure (4-
10%) topics. There was no systematic pattern in
communication errors that could be attributed to a

Level 4 versus a Level 5 TRACON.

35

25

15

10

pilot Advisory communication errors involved alti-
tudes (37-56%), and only pilots who flew through
airspace controlled by TRACON-2 had a high advi-

sory communication error rate pettaining to traffic

(29%) and traffic (24%) topics.

ores

ran

wes

ore

0:

©

ex

SL

@:

~

ox

x2

=

i:

~o

ox

~~

were

0

an

KA
bd s
——s ‘4
5 hy
bs $
Py Md
bY 4
s

<x

or

raxexers

xX

on

mi TRACON-1: Pilot
CITRACON-2: Pilot
ga TRACON-3: Pilot

E53 TRACON-1: Controller
COTRACON-2: Controller
COTRACON 3: Controller

Figure 6. Proportion of Aviation Topics Within the Instruction Speech Act That Contained

Communication Errors Made by Pilots and Controliers at Each TRACON Facility

14

3.3.3 Advisory. As shown in Figure 7, most of the

(31%). For TRACON-2 controllers, advisory com-
munication errors exceeded 65% for traffic and
TRACON-1 controllers had 53% advisory com-
munication errors represented in approach/departure


An Analysis of Approach Control{Pilor Voice Communications

A transactional communication set is a collection
of sequential transactions that occur between a con-
troller and pilot. Presented in Table 2 is an example of
acontroller/pilot transactional communication set. It
consists of 7 transactions that contain between 2 and
4 transmissions. In the first transmission, Universal?
744 initiates a
Upon initial call-up, the pilot states the aircraft’s call
sign, its current and target altitudes. The transaction
is established once the controller acknowledges the
pilot’s initial transmission. The transactional com-
munication set is completed when communication
and radar service for that aircraft are transferred to the

transaction with Approach Control.

next controller or radar service is terminated. The

As shown in Figure 2, Transaction 1 is made up of
4 transmissions. In transmission 1, the pilot makes the
initial call-up to begin the transaction. Pilot transmis-
sion 1 consists of 3 communication elements that
have been placed into their corresponding aviation
topic and speech act category. For example, [Name]
Approach and Universal 744 are the names of the
participants of the transaction; each are tagged with
the speech act category Address. The aviation topic
places a constraint on the communication clement by
serving to distinguish one Address from another

In the example, {Namej Approach is a communica-
tion element that identifies the intended receiver of
the transmission and it is tagged with the aviation

words “good day,” “see ya,” and “bye” offen are used _ topic labeled “receiver.” Likewise, Universal 744 is a
to indicate closure. communication element that provides the name of
. Pilot Transmission 1: Initial Call-up
Transmission 1
my Speech Actt Lh ‘Speech Act 2. ‘Speech Act 3
‘Aces Roques Report
= : RSET
Aviation Topic 2 Aviation Topic 2, “Altitude °
Receiver 1D 1D 4
ub (ame Approach) (Waiversal 748) wees
a. Air Traffic Control Transmission |
Transmission 2
qj Seach Af Speech Act 2 Spec At Speech Ac 4 Lv Speech Ac 5
— ‘ties FV) insnecice Secnntion L "eas
I cc I i
rae | AJ Aviston Topic? ‘station Topie 3 ‘Aviation Topic 5
3 asa | EE
memde) 74) Roger) «Say your speed}
. Pilot Transmission 2
Transmission 3
— ‘Speech Act t i, Spe Act 4
Ropes FN) Seeochan2 NY Spesch Ac — Request
RARE TFET) r i =
me an Tei? ‘Aviation Topic 3 ‘Aviation Top 4
V7 Sar > versal 744) [~~ ¥’} (Operate at 2600) > (250 knots)
Air Traffic Control Transmission 2
Transmission 4
0 Speech Act] LN] Speech Act?
address = Roques.
I I
Aviaaen Topic I ‘Avision Tapic2
Racer ID ‘Speed
xy Roger)

Figure 2. An Exampie of an ATC/Pilot Transaction.

> Universal is the name of a fictitious ait carrier. It is used for illustrative purposes only.


An Anatysis of Approach Control/Pilot Voice Communications

ae
Hy ‘amet Heading
Py Ta atinnde
A AppsDep.
cATIS
186 en © ee . . SURUPosition 7
cow.
eee Traitic
i
10% wee ee ~--f -H- ---4
a fe. woe PLA - ed
. i
zs ;
cs Be — Me

28
waa Hcadigy
Speed
SZAppsDep.

a aeee eee awe nee eee -- - ~fot-- ee. SOR Position

5 -

Pe oe = +4.

Figure 13. TRACON-1: Distribution of Controller Request Communication Errors

communication errors are distributed across partial
readback (56%), grouping (24%), and substitution
(9%). For pilots, heading erross resulted primarily
from partial readbacks (22%,) and grouped format
(6%); for example, “one thirty out of [intersection]
Radio frequency errors also resulted from partial
readbacks (14%) and grouped format (10%). Altitude
errors were due mostly to substitutions (6%) and
partial readbacks (6%). Airspeed errors resulted from

20

partial readbacks (8%), grouped format (8%), and
substitutions (3%). Acomposite readback error might
sound something like, “...one seventy, for six, twenty-
one twenty...”

3.4.2.2 Advisory. As shown in Figure 15, pilot
Advisory communication errors involved grouped
format (19%), excess verbiage (21%) and partial
readback (26%) more than omission (3%), substitu-
tion (3%), or dysfluency (9%). Altitude errors were


DOT/FAA/AM-96/26

Office of Aviation Medicine
Washington, D.C. 20591

19961105 080

An Analysis of Approach
Control/Pilot Voice

Communications

©. Veronika Prinzo

Civil Aeromedical Institute
Federal Aviation Administration
Oklahoma City, Oklahoma 73125

October 1996

Final Report

This document is available to the public
through the National Technical Information
Service, Springfield, Virginia 22161.

@ DTIC QUALITY INSPECTED 3

U.S. Department
of Transportation

Federal Aviation
Administration


specified in FAA Order 7110.65, or suggested pilot
communication in the Airman’s Information Manual,
were identified using the error code categories in-
cluded in the ATSAT.°

2.0 METHODS

2.1 Materials

2.1.1 Aviation Topics Speech Act Taxonomy
Coding Form (ATSAT cr). The ATSAT Coding Form
is a tool for categorizing ATC/pilot communication
elements according to their purpose and for labeling
various types of communication errors. As shown in
Table 3, the speech act categories are Address, Couz-
tesy, Instruction, Advisory, Request, and Non-
Codable. The Address is the “who” of the transmission.

An Analysis of Approach ConzrolfPilot Voice Communications

It references either an air traffic control facility posi-
tion/sector or an aircraft. In addition to showing a
level of respect, a Courtesy often signals the end of a
transactional communication set between the air traf-
fic controller and the pilot, in much the same way that
a “good-bye” signals the end of a telephone conversa-
tion. The Instruction, Advisory, and Request speech
act categories represent the “what” of the communica-
tion element - the action to be undertaken. They
represent the “do something,” “tell something,” and
“ask something” of an utterance. The complete ttles
of the speech act categories are: Address/Addressee,
Instruction/Clearance—Readback/Acknowledgment,
Advisory/Remark—Readback/Acknowledgment, Re-
quest-——Readback/Acknowledgment, Non-Codable
Remarks, and Comments.

TABLE 3. Aviation Topics/Speech Acts Taxonomy

Speech Act Category Aviation Topics
Address/Addressee Speaker, Receiver
Courtesy Thanks, Greetings, Apology

Instruction/Clearance--Readback/Acknowledgment

Advisory/Remark--Readback/Acknowledgment

Request--Readback/Acknowledgment

Non-Codable Remarks

Heading, Heading Modification, Altitude,
Altitude Restriction, Speed,
Approach/Departure, Frequency, Holding,
Rouie/Position, Transponder Code,
General Acknowiedgment

Heading, Heading Modification, Altitude,
Altitude Resiriction, Speed,
Approach/Departure, Route/Position,
NOTAM, ATIS, Weather, Sighting,
Traffic, General Acknowledgment

Heading, Altitude, Speed,
Approach/Departure, Route/Position,
Type, NOTAM, Traffic, Weather, Say
Again, General Acknowledgment

Equipment, Delivery, Other

° Pilots are not required to use the same standard phraseology as conttollers when communicating. To achieve a standard for comparison
between pilocs’ and controllers’ communications, the following rule was established: If a pilot attempted a verbatim readback of a controller's
transmission, then the same coding procedures that were used on controllers’ transmissions were applied to the pi! :'s verbatim readback.,

7


An Analysis of Approach Control/Pilot Voice Communications

the speaker of the transmission, and it is tagged with
the aviation topic labeled “speaker.” “leaving 6 thou-
sand 5 hundred, maintain 3 thousand” is a communi-
cation element idencifted as a Report of the aircraft's
current altitude. Thus, the communication element
would be tagged with the speech act Advisory/Remark
and its aviation topic label is altitude.

Presented in Figure 3 is a schematic representation
of the 7 transactions making up the transactional
communication set between Universal 744 and a con-
troller at the Approach Control facility. The number of

transactions that make upa transactional communication

set will depend on the number of transmissions needed
to facilitate an aircraft’s movement through the

controller's sector/position.

The purpose of the present study was to develop a
database of controller and pilot voice communica-
tions. Copies of TRACON andiviapes of ATC/pilot
communications were provided to the authois and
transcribed by a subject-matter-expert (SME). The
aviation topic-speech act taxonomy (ATSAT, Prinzo,
et al., 1995) was used to categorize and code ATC/
pilot verbal communications. Con:munications that
deviated from the standard communications form

Transaction 1: Initial Ca

xi Establish Air Craft Position

‘Transmission 1:
Als Craft Initial
Call up

OPEN TRANSACTIONAL
COMMUNICATIONSET.

7

‘Transmission 7- ont | Transmission 4:
ATC Butabiishes Transemsssion 2 ATO
Arcee > Pitet provided ATC ‘acknowledgment
ntal Approoch Piet provided ATC F-—> | acknewlodgm
ungarstanding

‘Transection 2: Change in Air

Craft Heading

‘Transmission 1:
ATC instructs Pilot
to change heading

‘Tremmussion 2:
Pilot nveys
‘acceptance

‘Transaction 3: Issue Traffic Advisory
[|] fecoos |
ASelaacteate =}

LY

‘Tyancinission 2
Pitot reduces speed

Transaction 4:

r
Transmission 1°
ATC istacs course
change

TRANSACTIONAL
‘COMMUNICATION
‘SET

Change Air Craft Heading

‘Trancmission 2-
Pilot confirms
course change

‘Transaction 5:

Change Air Craft Altitude

‘Fran mission
ATC inves attitude,
change

Tranemistion 2:
Pilot confirms
alutude change

Transaction 6:

Runway Assignment Issued at Final Approach Fix

n

Ly

anentoson |
marmisien? |

‘Fransaction 7:

Transfer Authority to Tower

Teanemssion |
ATC mtace change
im exie7 and hand-
fnorvice

CLOSE TRANSACTIONAL
COMMUNICATION SET

changes frequency.

Figure 3. An Example of an ATC/Pitot Transactional Communication Set


An Analysis of Approach Control/Pilot Voice Communications

25%
mae Heading
em Altitude
EBApp Dep.
28% ee eee ~ -] S2aFrequency ~ -@-.--4
CORtJPosition
3Tra. Code
BE P----~-------------- 0-022 - e ee --------------------9f ----4
5
by
KI
He
i
KI
tem f------------------------------------- +--+. --- KY
R}
be
by
by
IS
S% fb --Hy---------- ee eee ee eee eee eee eee =
a nani
4,

Figure 24. TRACON-3: Distribution of

errors involved use of non-standard communication,
such as “...go direct to [fix]” and “make it straight in
runway one two.”

3.4.5.2 Advisory. Figure 22 displays the results of
the analysis performed on Advisory communication
errors. Most of the errors resulted from excess verbiage
(41%), omission (14%), and dysfluency (13%). Traf-
fic (26) and route/position (18%) information con-
tained most of the communication errors. Traffic
information errors resulted from grouped format (4%),
substitution (5%), excess verbiage 14%), and
dysfluency (3%). In the following example ATC is
providing a traffic advisory, “Yeah, the [aircraft] is at
uh eieven to ten o'clock now and....” Like traffic,
route/position and weather advisory errors resulted
from omission (2%, 4%), excess verbiage (12%, 6%)
and dysfluency (4%, 4%). General sighting errors
resulted from omission (2%), substitution (2%), ex-
cess verbiage (7%), and dysfluency (2%).

3.4.5.3 Request. The results of the analysis per-
formed on Request communication errors are pre-
sented ‘n Figure 23. The largest percentage of errors
resulted from substitution (36%), followed by excess
verbiage (31%). Fifty-three percent of the Request

communication errors involved altitude, 21%

% %, % we,
Ye, *ag , we Xe,

Pilot instruction Communication Errors

pertained to route/position, and 8% involved ap-
proach/departure aviation topics. Altitude communi-
cation errors resulted from grouped format (11%),
substitution (21%), and excess verbiage (21%). Ex-
amples include, “...and what’s the on course heading to
[town]?,” and “...say your altitude now out of forty-

eight.”

3.4.6 TRACON-3 Facility (Level 4): Pilot
Communications

3.4.6.1 Instruction. See Figure 24. The majority of
pilot Instruction errors resulted from partial readback
(59%) and grouped format (15%). The aviation top-
ics heading (29%), frequency (25%), and altitude
(17%) contained the most communication errors.
Pilot heading errors resulted from grouped format
(45%), dysfluency (2%), and partial readback (23%).
“Three five zero [call sign} to the right” and *...three
fifty one the heading down to four [call sign]” are
examples of partial readback, excess verbiage, and
grouped format. In contrast, there were more fre-
quency communication errors that involved partial
readback errors (14%) than grouped format (8%),
with substitution and excess verbiage rarely involved
(1% each). “Twenty-three four {call sign} you have a



An Analysis of Approach ControtiPilot Voice Communications

16%

16%

2%

10%

8%

6% f---------------------

4%

2%

0%

EaApp Dep.
CSRLPositioa

Figure 22. TRACON-3: Distribution of Controller Advisory Communication Errors

25%

cAltitude
ESAApp Dep.
CORt/Position
20% =f --------------------Beap-----------fb------------------------4
S% P----------~+-------~-Be----~------BReb- --------------------
0% oN eee > eee - weed
N
5% fel--------.-.-------fee- AY------ wont eee
0% |
& 3, 4
a,
; i, ey,
“oy “ey, “a
22 % ag
ee

Figure 23. TRACON-3: Distribution of Controfier Request Communication Errors

route/ position (5%), and transponder code (4%) avia-
tion topics that did not improve the comprehensibil-
ity of the transmission. For example, “...turn right to
a heading of three two zero” adds time on frequency
compared to “...turn right heading three two zero.”
Omission errors (10%) were common in approach/

26

departure clearances. Controllers omitted the word
“runway” in “...cleared ILS one two left approach.”
Radio frequency errors often involved grouped for-
mat (4%) and omission (15%) of numbers and/or
words “...contact [name] tower one twenty-three four”
or “...contact tower twenty-three four.” Substitution


ascertain the impact of how the current voice-radio
communicatioas system affects air safety (Prinzo &
Britton, 1993). Although incident report forms are
well documented by government agencies, and con-
trollers are required to use FAA Order 7110.65 Air
Traffic Control when communicating with pilots, re-
searchers traditionally have not used FAA Order
7110.65 to guide their analyses of ATC/pilot voice
communications.

Prinzo, Britton, and Hendrix (1995) developed the
aviation topics speech acts taxonomy (ATSAT) to
analyze communication elements in accordance with
FAA Order 7110.65 and the Airman’s Information
Manual (AIM). As shown in Figure 1, the ATSAT is
ahierarchical order of communication elements, which
combine to form messages that are transmitted over
voice :adio or data link communications systems (i.e.,
transmissions). The communication element is con-
ceptualized as a fundamental unit of meaningful ver-
bal language. In the ATSAT, communication elements
are arranged by their functionality; that is, their pur-
pose, operation, or action. A commonly referenced

An Analysis of Approach Control{Pilot Voice Communications

communication element is the speech act (Searle,
1969; Kanki and Foushee, 1989}. Aviation topics are
the subject matter of the speech act (Prinzo et al.,
1995).

As new, digitized communication systems, such as
data link appear, ATC communications may be pre-
sented as either oral or written verbal language. To
reflect these changes, the Morrow and co-authors’
definition of a speech act has been modified to reflect
these changes. In this report, the speech act is defined
as an utterance, either spoken or written, which de-
scribes one discourse function.

Atransaction begins when 2 people agree to partici-
pate in meaningfal, interactive communication. In a
transaction, 1 person is the speaker and the other is the
receiver of the transmitted message. A change in the
role of the persca from speaker to receiver signals that
a new transmission (or turn) has begun. The transac-
tion terminates once the speaker and receiver indicate

that a mutual understanding was achieved. Often,
words such as “roger” and “wilco” are used to indicate
understanding.

‘Transactional Communications Set

‘Transaction 1

=

Message 2 i

7
—
! |

SL |

i



An Analysis of Approach Control/Pilet Voice Communications

60% —_—
fas TRACON-1: Speaker ID
[I TRACON-1: Receiver ID
50% f-------
#@% f------------------- ' cee ee ee eee eee eee eee eee eee eeee
30% f------ pil - - -----------------------------
we f--...........9-... Ree. 22-22-22 eee ee --
10% }----- s goon ce
0% %
fo Me
Figure 9. Distribution of Controller Address Errors
80%
tus TRACON-1: Speaker ID
TM% j|Y--------------- ween _. .- --] SYTRACON-4: Receiver ID
. [“ITRACON.2: Speaker ID
E-ITRACON-2: Receiver 1D
0% |---------------4 CEITRACON-3:SpeakerID sf
—— ans xa TRACON-3: Receiver ID
50% f--------------.4 LE} -------------- 2-2-2 5-e eee eee eee eee ee ees
@
aay
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ow Oe | ae
a, %, 4, $ 4
Sy iy % “a, ey,
*& s, “Gy Fy, "ep
y %» %, %, iy,
“ee ty

Figure 10. Distribution of Pilot Address Communication Errors


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An Analysis of Approach Conzrol{Pilor Voice Communications

‘mm Hicading
tap Altitude
ESpAk. Restrict.
20% pee eee eee --jESped Lee
ECBApp Dep.
EoFrequency
COR?Position

ve be | an
. | |. anno tL

% &, * <q 2) 4
te _ a, “ey we “ey “ey ee ey,
“ rn %, a
%, “4,

Figure 17. TRACON-2: Distribution of Controlier Instruction Communication Errats

$0%
CESApp/Dep.
SIRLPasition
ema Sight
40% Looe . wee eee we eee eee eee Sen Traffic
Wie f ------------- -----+-+------- were
W% }---------------------.------- 2-0-4
9% [--- - - wat tenn -BBJ----------------
0% faved aa
Pay ee Fee “iy, a %, 3, %,
, %
“ey “ey om a Say “es,
ee %

Figure 78. TRACON-2: Distribution of Controller Advisory Communication Errors

23


ACKNOWLEDGMENTS

This research was sponsored by the Federal Aviation Administration’s Offices of Aviation
Safety Analysis (ASY-200), and the Quality Assurance Division of Air Traffic System
Effectiveness (ATH-200). We thank Robert Dye, James Buckles (AEA-501), and James
Woods (retired) for their support. We also acknowledge Shana Reed and Thomas Britton for
the many hours of monotonous and tedious effort that they devoted to transcribing and
coding the data presented in this report.

iii


An Analysis of Approach Control/Pilot Voice Communications
y: ‘PP’

TABLE 5S. Exampie of an Air Traffic Control Transmission that was Segmented into
Cc:amunication Eflemenis, Placed into Speech Act Categories,
Labeled by Aviation Topics, and Communication Error-Coded

“Universal Seven Forty-four, [Name] Approach, Roger, Descend and maintain two thousand, Say your

speed”
Communication | Universal; [Name] Roger/ Descend and} Say your speed/
Element: Seven | Approach/ maintain two
Forty-four! thousand/

Speech Aci Address | Address {| Advisory/Report | instruction | Advisory/Report
Aviation Topic: Receiver | Speaker Gnl Ackn Altitude _Speed
Location No.: 4 2 3 4 5
Communication
Error Code: Es

Aviation Topic 1,
Aviation Topic 2,
Aviation Topic 3,
Aviation Topic 4,
Aviation Topic 5,

“Universal Seven Forty-four," is the receiver identification.

“Iname] Approach," is the speaker identification.

“Roger,” is a general acknowledgment to the previous transmission.

“Descend and mainiain two thousand" is an instruction pertaining io a change in altitude.
"Say your speed" is a request for the aircraft's current speed with an excess verbiage and a

substitution error designated by the letters “E”and “S.”

placed under the General Acknowledgment column
under the “Advisory/Report” speech act category, and
so on until the location of each communication ele-
ment was recorded on the ATSAT,. For example, the
“Roges” in communication element 3 was placed in
the “Advisory/Report” speech act category and la-
beled as a General Acknowledgment because the con-
troller was letting the pilot know that the entire
transmission was received. The previous transmission
was the initial call-up.

Then, each communication element was evaluated
for proper phraseology usage. Ifincorrect phraseology
was used, the coder copied onto ATSAT, the alpha-
bet letter code corresponding to that type of commu-
nication etror (see Table 4) next to the location
number of the communication element that was spo-
ken incorrectly. Aviation Topic 5, “Say your speed”

contains both an excess verbiage and a substitution
error. Excess verbiage results with the presence of the
additional word “your” in the request and the word
“speed” was used as a substitution for the word “air-
speed.” The transmission should have been spoken as,
“Universal Seven Forty-four, descend and maintain
two thousand, say airspeed.” Each step was repeated
for each line of transcribed communication.
Intercoder reliability was assessed by computing
the percent agreement between the segmentation and
codification made by the SME and one of the ATSAT
authors for a sample of 25 randomly-selected trans-
missions. There was 97% agreement for segmentation
of the entire message into identical communication
elements, 90% agreement for placement of the same
tovation number associated with each communica-
tion element onto the ATSAT,,,, both in the proper

7 In FAA Order 7110.65 “Roger” is defined as “{ have received all of your last sransmission.”

8 This is in reference to FAA Order 7110.65G Par. 5-101.


An Analysis of Approach ControllPilos Voice Communications

The same analysis was performed on pilor trans-
missions. Of the 5,900 pilot communication ele-
ments, 3,500 contained at least 1 communication
error (5950). For pilots, 96% of the communication
errors involved communication elements within the
Instruction (53%), Address (25%), and Advisory
(18%) speech acts categories.

3.2 Analysis of Speech Act Communication
Errors

Figure 4 presents the proportion of all speech act
communication errors made hy pilots and controllers
at each TRACON facility. Thus, 100% of the 2,255
communication errors made by pilots from TRACON-
1 are distributed across Address (19%), Courtesy
(0%), Instruction (61%), Advisory (17%), Request
(2%), and Non-Codable (1%).

7

As shown in Figure 4, most of the pilot and control-
ler communication errors from all 3 TRACON facili-
ties involved Instructions. Pilots made more errors
involving Address than controllers, and both pilots
and controllers made comparable communication
errors involving Advisory transmissions. TRACON-
land TRACON-2 (Level 5) made more errors involv-
ing Instructions and TRACON-3 (Level 4) made
more Address communication errors.

Aseries of analyses were performed on the commu-
nication errors associated with specific aviation topics
in each of the speech act categories. The analyses were
performed separately according to TRACON facility
and speaker.

50

40

30

eo

a

2

ae

20

S
seetete

x

S

.
So

ist

10

wi

8

LOX

Address

Courtesy

Instruction

Request Non-Codable

mm TRACON-1: Pilot
COTRACON-2: Pilot
@BTRACON-3: Pilot

COTRACON-1: Controller
COTRACON
&aTRACON-3: Controfler

+ Controller

Figure 4. Proportion of All Speech Act Communication Errors Made by Pilots and
Controllers at Each TRACON Facility

12


Technical Report Documentation Page

T. Report No. 2. Government Accession No. 3. Recipient's Catalog No.
DOT/FAA/AM-96/26

4, Title and Suotitie 5. Report Date

An Analysis of Approach Control/Pilot Voice Communications October 1996

7, Author) 8. Performing Organization Report No.

O. Veronika Prinzo

9. Pesforming Orgonization Name and Address 30. Work Unit No, (RAIS)

FAA Civil Aeromedical Institute
P.O. Box 25082

Oklahoma City, OK 73125 11. Contract or Grant No.
DIFA02-91-C-91089

12. Sponsoring Agency name and Address 13. Type of Report and Feriod Covered
Office of Aviation Medicine
Federal Aviation Administration
800 independence Ave., $.W.

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

15. Supplemental Notes
This work was performed under Task AM-D-94-HRR-117

16. Abstract

This report consists of an analysis of air traffic control and pilot voice communications that occurred at 3 terminal air traffic control
facilities (TRACONSs). Each transmission was parsed into communication elements. Each communication element was assigned to a
speech act category (¢.g., address, instruction, request, advisory) and aviation topic (e.g., heading, altitude, speed, readback) and
evaluated using the aviation topic-speech act taxonomy (ATSAT, Prinzo, et al., 1995). A total of 12,200 communication elements in
4,500 transmissions make up the database. Communication elements appeared most frequently in the address and instruction speech
act categories. Of the 2,500 controller communication elements, 40% contained at least 1 communication error. The number and
types of communication errors (message content and delivery technique) located within each speech act category were determined
and separate communication error analyses are reported for pilots and controllers by TRACON facility. Of the 5,900 pilot
communication elements, 59% contained at least 1 communication error. More than 50% of controllers’ and pilots’ communication
errors occurred in the instruction speech act category. Generally, controllers omitted key words that pertained to radio frequency,
airspeed, or approach/departure instructions. Pilots orly partially read back instructions involving heading, radio frequency, and
airspeed aviation topics and grouped numbers in a radio frequency, airspeed, or heading. Pilots’ and controllers’ communications
became more conversational and verbose when their transmissions included advisory or request speech acts. Omitting and grouping
numbers in transmissions may be strategies used to minimize time on frequency. Ironically, these strategies may create the problems
thar pilots and controllers are trying to prevent. Frequency congestion may occur from additional transmissions that are made to
resolve ambiguities or repair misunderstandings due to incomplete transmissions.

17. Key Words 18. Distibution Statement
ATC communications

Discourse processes
Communication taxonomy

19. Security Classif. (of this report) 20. Security Classif. (OF this page) 21, No. of Pages BD. Price
Unclassified Unclassified 41

Form DOT? 1700.7 (8-72) ‘Reproduction of compieted page authorized



APPENDICES

Al



An Analysis of Approach Control/Pilot Voice Communications

Was Heading
fr Altitude
COAL. Restrict.
COSpred

Eu AppDep.
= 3Frequency
ECURL/Position

18% f--

5% “A es
0% i
%
te

Figure 14, TRACON-1: Distribution of Pilot Instruction Communication Errors

‘vam Heading
ma Altitude

CZ3AppDep,
EAATIS
tmowWx

15%

10%

8%
{|
om
Se,
*e,
“
Ma,

ee


NOTICE

This document is disseminated under the sponsership of
the U.S. Department of Transportation in the interest of
information exchange. The United States Government
assumes no liability for the contents or use thereof.


An Analysis of Approach ControlfPilot Voice Communications

10%

S%

‘tan Altitude
xB App/Dep.
SURL Position
cow.
eaaSight

Figure 26. TRACON-3: Distribution of Pilot Request Communication Errors

(6%), or grouped format (3%). In response to ATC
asking which runway the pilot would like, the pilot
states, “OK, [call sign], I'd just as soon come on
thirteen one three no problem on that.” Altitude
request errors resulted mainly from substitution (12%)
although grouped format, dysfluency, and partial
readback each contributed 3%. Pilots substituted the
word “lower” in a request or in a readback, “Can you
approve a lower for [call sign],” and “Yeah level six
we'll take lower when it’s available.”

4.0 DISCUSSION

The purpose of this study was to develop baseline
data on typical controller and pilot voice communica-
tions. Although other researchers have analyzed ATC/
pilot communications, what made this study unique
is that FAA Order 7110.65 guided the development of
the ATSAT, which was used to categorize the commu-
nication elements in their transmissions. The analyses
focused on verbal communications that deviated from
the standard specified in FAA Order 7110.65G (or
suggested pilot communication in the Airman ’s infor-
mation Manual). Problematic communications

29

involved mode C malfunctions, call sign ambiguity,
call sign confusion, controller confusion, pilot confu-
2

sion, 2 aircraft on frequency talking to each other,
report of an ELT, open mike, traffic, weather, and so
on.

Do spoken communications present a problem to
air safety? Knowing that communication errors are
cited time and time again in operational errors, pilot
deviations, and near midair collisions, that the errors
occur with regularity, and that the errors can create
frequency congestion, the answer is yes.

An examination of the aviation topic communica-
tion errors revealed that controllers often omitted key
words that pertained to frequency, airspeed, or ap-
proach/departure Instructions. Often, pilots only par-
tially read back Instructions involving heading, radio
frequency, and airspeed aviation topics, and grouped
the numbers in a radio frequency, airspeed, or head-
ing. Pilots’ and controllers’ communications became
more conversational and verbose when their transmis-
sions included Advisory or Request speech acts. Advi-
sory communication errors that resulted from excess
verbiage was facility specific: For controllers at

TRACON-1, it involved routes/position; for


°

An Analysis of Approach Contrel{Pilot Voice Communications

“|-you'll need to stay at seven for about the next ten
miles for traffic at six....” Approach/departure com-
munication errors were due to omission (8%), excess
verbiage (3%), and dysfluency (8%). Route/position
and sighting errors were uncommon.

3.4.3.3 Request. There were not encugh commu-
nication errors to analyze meaningfully.

3.4.4 TRACON-2 Facility (Level 5): Pilot
Communications

3.4.4.1 Instruction. See Figure 19. Most of the
pilot communication errors were distributed in
grouped format (21%), substitution (11%), and par-
tial readback (55%) involving communication errors
pertaining to heading (26%), altitude (14%), speed
(21%), approach/departure (8%), and frequency
(15%) aviation topics. Heading errors resulted from
partial readback (20%) and grouped format (6%),
whereas airspeed errors resulted from grouped format
and partial readback equally (9%); substitution errors
were infrequent (3%). Frequency errors involved
grouped format (6%) to a lesser degree than partial

readback (7%). Altitude errors were more likely to
resuls from substitution or partial readback (5% each)
than from transposition, excess verbiage, dysfluency,
or misarticulation (1% each).

3.44.2 Advisory. See Figure 20. In this analysis,
most of the pilot advisory communication errors
oceurred within the aviation topics traffic (30%) and
altitude (36%). Heading (6%), speed (6%), approach/
departure (7%), and sighting (6%) accounted for an
additional 23% of the advisory pilot errors. Most
communication errors resulted from partial readback
(28%) and substitution (24%). Traffic advisory com-
munication errors resulted from substitution (18%),
dysfluency (7%), and partial readback (4%). For
example, “yea, ah, I got him....” Altitude errors were
due to grouped format (7%), excess verbiage (10%),
dysfluency (4%), and partial readback (15%). For
example, in response to ATC “maintain four thou-
sand” the pilot readbacks, “...ckay, we'll maintain
four till advised...”

3.4.4.3 Request. There were insufficient commu-
nication errors to produce meaningful results.

28%
Tews Heading
EaarAltitude
IrESAIt. Restrict.
mm p-------------------- we eee ee eee _ 2 - ~~~ |S Speed
(3AppsDep.
(Frequency
TSRt/Position
ro one eee eee ee eee wee eee eee eee eee eee eee
a veneer etter en eee ee eee eee) 2+ -------
S% - ee een gee ee eee eee
% O
&, %, %, Se 4%,
ia Ge, “ey aA
Ye

Figure 19. TRACON-2: Distribution of Pifot Instruction Communication Errors


An Analysis of Approach Contrel/Pilor Voice Communications

Within each speech act categoty are specific avic-
tion topics that define the subject of each communi-
cation element. The aviation topics are listed next to
their speech act category in the body of Table 3. The
aviation topic constraints the communication ele-
ment by imposing a restriction on its identified speech
act category (who, what). For example, there are only
Z types of aviation topics fisted next to the Address
speech acy category. Generally, there only can be 1
speaker and 1 receiver of a transmission. There are 3
types of aviation topics listed in the Courtesy speech
act category: “Thanks,” “Greetings,” and “Apology.
The aviation topics listed in the Instruction, Advi-
sory, and Request speech act categories are not ex-
haustive, but represent the most frequently uttered
messages that we heard from field tapes.

The communication error types and their defini-
tions are listed in Table 4. The coder labels non-
standard communications according to the type of
error present in the communication element. There
are 2 categories of communication errors: message
content and delivery technique. Message content er-
rors pertain to non-standard communication usage;
delivery technique errors refer to stammes, stutters,
or misspoken words. The types of message content
errors are: grouped, sequential, omission, substitu-
tion, transposition, excessive verbiage, and partial
readback. Dysfluency and misarticulation are delivery
technique errors.

2.1.2 Audiotapes. Copies of audiotaped record-
ings of ATC/pilot communications were obtained
from 2 Level 5 TRACON facilities (TRACON-1 and
TRACON-2) and 1 Level 4 TRACON (TRACON-
3). Bach facility included a brief description of the
tape’s contents. For example, “This side of the tape
includes f hour of heavy traffic on the [name] position at
{Terminal Air Traffic Control] Airport.”

A total of 9 hours of transcribed communications,
representing approximately 4,500 ATC/pilot voice
radio transmissions, were analyzed. There were 2,878
transmissions from TRACON-I represented in 6
hours of normal communications recorded from the
feeder and arrival ATC positions. TRACON-2 audio-
tapes had 654 transmissions and represented } hour of
normal communications from the final approach po-
sition. TRACON-3 audiotapes contained a rotal of

1,250 communications that represented 2 hours of
transmissions from the arrival and departuze posi-
tions. Presented in Appendix A is a table of the total
number of communication elements by speech act
category; presented in Appendix B is a table of the
total number of communication errors made by pilots
and controllers at each approach control facility.

2.2 Procedure

The audiotapes were transcribed, and the accuracy
of the transcripts was verified and, when necessary,
corrected by the SME. Using the ATSAT, the SME
segmented each line of transcribed communications
inte communication elements, numbered each one
according to the order in which it was spoken, and
then classified each according to its content and
purpose. The encoding of communication elements
into speech acts and aviation topics was not per-
formed on transmissions in isolation. Rather the con-
text in which a transmission was spoken was vital to
how it would be encoded.

Since pilots are not required to use the same stan-
dard phraseology contained in FAA Order 7110.65 as
are controllers, a rule was developed by which com-
parison could be made between pilot and controller
transmissions: Ifa pilot attempted a verbatim readback
of a controiler’s transmission, then the same coding
procedures used on controllers’ transmissions were
applied to pilots’ verbatim readbacks.

Once the communication elements were placed
into their respective speech act categories, those verbal
communications which deviated from the standard
specified in FAA Order 7110.65, or suggested pilot
communication in the Airman’s information Manual,

were identified using the error code categories in the
ATSAT. Presented in Table $ is an example of 1 line
of communication thar was segmented, numbered,
and communication etror-coded.

Using the example on Table 5, the coder
segmented the transmission into communication ele-

ments and then determined their corresponding avia-

tion topic and speech act category membership. The
coder placed a “1” in the Recei
column under the “Address” speech act c:

+ Identification

gory, a2”

was placed under the Speaker Identification column

under the “Address” speech act category, 2 “3” was


speech act category and in the proper aviation topic,
and finally, 70% agreement for selection of the same
communication error type associated with that com-
munication element.

3.0 RESULTS

3.1 Data Analysis

A total of 12,200 communication elements in
4,500 transmissions was analyzed in accordance with
the ATSAT , procedures. Presented in Appendices A
and B are tables of the total number of communica-
tion elements and types of communication errors
made by pilots and controllers. Presented in Table 6
is the distribution of communication elements within
each speech act category derived from all of the ATC/
pilot transmissions. Communication elements

An Analysis of Approach Control/Pilot Voice Communications

appeared most frequently in the Addruss (37%) and
Instruction (36%) speech act categories for both groups
of speakers. Rarely was the Request speech act in-
cluded in a transmission (2%).

The number of communication errors located
within each speech act category was calculated and
those values are reported as percentages. Separate
communication error analyses were performed on
each of the audiotapes. For example, 2,500 of the
6,300 controller communication elements con-
tained at least 1 communication error (40%). The
distribution of those 40% communication errors
within each speech act category is presented in
Table 7. For controllers, 93% of these errors in-
volved communication elements located in the
Instruction (55%), Advisory (24%), and Address
(14%) speech act categories.

TABLE 6. Distribution of Controiler and Pitot Communication Elements

Within Each Speech Act Category
Speech Act Category Controller (n=S,300) Pilot (n=5,960)
Address 37% 37%
Instruction 36% 35%
Advisory 16% 18%
Courtesy 5% 5%
Request 2% 2%
Non-Codable 4% 3%

TABLE 7. Distribution of Controller and Pilot Communication Errors
Within Each Speech Aci Category

Speech Act Category Controller (n=2,500) Pilot (n=3,500)
Address 14% 25%
Instruction 55% 53%
Advisory 24% 18%
Courtesy 0% 0%
Request 4% 3%
Non-Codabie 3% 1%