A Flight Data Console (FDC) was developed to allow simulation of a digital communications link to replace the current voice communication system used in air traffic control (ATC). The voice system requires manipulation of radio equipment, read-back of clearances, and mental storage of critical information items, all contributing to high workload, particularly during single-pilot operations. This was an inflight study to determine how a digital communications system might reduce cockpit workload, improve flight proficiency, and be accepted by general aviation pilots. Results show that instrument flight, including approach and landing, can be accomplished quite effectively using a digital data link system for ATC communications. All pilots expressed a need for a back-up voice channel. When included, this channel was used sparingly and principally to confirm any item of information about which there might be uncertainty

Christensen, D. G.

Duffy, J. W.

Parker, J. F.

English

NASA Technical Reports Server

A FLIGHT INVESTIGATION OF SIMULATED DATA LINK COMMUNICATIONS 
DURING SINGLE-PILOT IFR FLIGHT 
J. F. Parker, J. W. Duffy, and D. G. Christensen 
BioTechnology, Inc. 
ABSTRACT 
A Flight Data Console (FDC) was developed to allow simula- 
tion of a digital communications link to replace the current 
voice communication system used in Air Traffic Control. The 
voice system requires manipulation of radio equipment, read-back 
of clearances, and mental storage of critical information items, 
all contributing to high workload, particularly during single- 
pilot operations. This was an inflight study to determine how 
a digital communications system might reduce cockpit workload, 
improve flight proficiency, and be accepted by general aviation 
pilots. 
Results show that instrument flight, including approach 
and landing, can be accomplished quite effectively using a 
digital data link system for ATC communications. All pilots 
expressed a need for a back-up voice channel. When included, 
this channel was used sparingly and principally to confirm any 
item of information about which there might be uncertainty. 
Workload for single-pilot flight, using the FDC, matched that 
found when a qualified copilot was present. Comments by subject 
pilots identified a number of human factors issues (placement, 
size, message format, etc.) which influence the acceptance of 
a data link system. 
211 
https://ntrs.nasa.gov/search.jsp?R=19840003978 2020-03-22T07:55:33+00:00Z
PROJECT OBJECTIVES 
The safety record of general aviation is not excellent, 
with 1200 to 1500 fatalities occurring regularly each year. 
In general aviation, single-pilot instrument flight operations 
are known to be very demanding, with cockpit data management 
(information processing) representing a key issue. 
The objective of this project was to study data management 
during single-pilot IFR. The initial project period was spent 
in developing an item of cockpit instrumentation, the Flight 
Data Console (FDC), which could be used to simulate use of a 
digital data link to replace the current voice communications 
system used in ATC. In the second project period, an inflight 
evaluation was conducted using the FDC. Results led to a number 
of recommendations for improvements in cockpit data management 
in general aviation. 
0 STUDY PROBLEMS OF DATA MANAGEMENT DURING 
GA SINGLE-PILOT IFR FLIGHT 
0 DESIGN AND CONSTRUCT A COCKPIT FLIGHT DATA CONSOLE (FDC) 
- PRESENT ATC REFERENCE AND COMMAND DATA 
- REMOVE PILOT FROM ATC VOICE LOOP 
0 CONDUCT AN INFLIGHT EVALUATION 
0 PREPARE RECOMMENDATIONS ON 
- IMPROVED COCKPIT DATA MANAGEMENT 
- USE OF AN FDC-TYPE SYSTEM IN A FUTURE 
ATC ENVIRONMENT 
212 
FLIGHT EVALUATION PLAN 
The flight evaluations were conducted in two phases. 
Phase 1 used only terminal area approaches to airports in the 
Washington, DC area. In this phase, four kinds of flight were 
flown: 
Copilot - In this flight, which provided baseline data, 
the subject pilot flew with an instrument-rated copilot and was 
free to use the copilot in any way desired. This flight was 
considered optimum in terms of reducing workload and making the 
flight as proficient and safe as possible. 
Flight Data Console/Memory - Here the subject pilot used 
the FDC as an electronic data storage system (memory aid) solely 
to assist during each instrument approach. 
Single-Pilot IFR - This is the customary single-pilot 
instrument flight. A safety pilot was present but did not 
participate in any way. The FDC was not used. 
Flight Data Console/ATC - In this flight, all approaches 
were flown using Air Traffic Control information provided through 
the Flight Data Console. 
FLIGHT EVALUATION PLAN 
PHASE 1 NO. OF SUBJECTS 
0 TERMINAL AREA APPROACHES 8 
- CO-PI LOT 
- FLIGHT DATA CONSOLE / MEMORY 
- SINGLE-PILOT IFR 
- FLIGHT DATA CONSOLE 1 ATC 
PHASE 2 
0 TERMINAL AREA APPROACHES 
- FLIGHT DATA CONSOLE / ATC 
(VOICE BACK-UP) 
9 
0 ENROUTE WO n.mi., FULL IFR) 
- SINGLE-PILOT IFR 
- FLIGHT DATA CONSOLE / ATC 
(VOICE BACK-UP) 
4 
213 
COMPONENTS OF FLIGHT DATA CONSOLE 
The Flight Data Console is made up of three principal-parts: 
a front seat display and data entry panel for use by the pilot, 
a rear seat display and data entry panel whereby a console 
operator serves as a transducer for ATC instructions (entering 
ATC commands and immediately transmitting these commands to 
the front seat display), and a battery power unit which makes 
the system independent of the aircraft. 
214 
PILOT'S DISPLAY AND KEYBOARD 
The unit which presents ATC information uses liquid crystal 
displays, each of which can present up to eight digits. The 
right column presents and stores flight data items as entered 
by the pilot. Using this capability, the FDC can serve as a 
memory aid and, in essence, 
kneepad. 
take the place of a paper and pencil 
The left column presents command information from 
Air Traffic Control. This includes instructions for changes in 
heading (including direction of turn), changes in altitude, 
frequencies, 
new 
updated altimeter settings, and, as shown in the 
bottom two display windows, "Cleared for Approach" and "Cleared 
to Land" instructions. When the pilot receives this information 
from ATC, he depresses the acknowledge key, completes the in- 
struction, and presses another key to indicate completion. 
ATC 
COMMAND 
e 
- .-. 
LEFT/RIGHT LIGHTS 
REFERENCE DATA DISPLAY: 
_ ~~DE!NDICATING 
APPROACH 
LtGHT 
ADJUSTABLE KEY BOARD - 
-EDGE 
FRONT CONSOLE 
215 
INSTALLATION OF FLIGHT DATA CONSOLE 
The Flight Data Console was installed in a twin-engine Piper 
Aztec aircraft used for all flight evaluations. Because the 
system could not be permanently installed, the FDC display was 
positioned just behind the throttle quadrant with the data entry 
keyboard just right of the pilot's elbow position. This install- 
ation proved workable although far from optimal in terms of 
ease of viewing and operation. 
216 
WORKLOAD 
At the completion of all terminal area approaches, subject 
pilots ranked the four flight conditions in terms of workload 
imposed. Based on these rankings, the presentation of ATC 
instructions through the Flight Data Console results in a cock- 
pit workload equal to that found when flying with a fully 
qualified instrument copilot. Workload is substantially heavier 
both for the single-pilot IFR condition and for those flights in 
which the FDC is used simply as an electronic memory aid. 
AVERAGE 
RANKING 
WORKLOAD 
4 = LIGHTEST WORKLOAD 1 = HEAVIEST WORKLOAD 
A 
COPI LOT 
B C 
FDc/ SINGLE-PILOT 
MEMORY IFR 
FLIGHT CONDITIONS 
D 
FDCI 
ATC 
217 
ACCEPTANCE OF FLIGHT DATA CONSOLE 
(Positive) 
One project objective was to determine the extent to which 
a data link communications system would be accepted by general 
aviation pilots. Many comments and recommendations were re- 
ceived. It was found that the Flight Data Console was well 
received, with its acceptance seeming to involve three basic 
dimensions. These are (1) communications effectiveness, (2) 
workload reduction, and (3) an improvement in cockpit conditions. 
ACCEPTANCE COMMENTS 
ON FLIGHT DATA CONSOLE 
ACCEPTANCE 
0 COMMUNICATIONS EFFECTIVENESS 
“NO MIXUP ON WHO THE INSTRUCTION IS FOR” 
“NO MISUNDERSTANDING OR FORGETTING NUMBERS” 
“DON’T MISS CALLS” 
0 WORKLOAD REDUCTION 
“NO FUMBLING WITH PENCIL, KNEEBOARD, MIKE OR 
VOLUME CONTROL” 
0 COCKPIT CONDITIONS 
“LIKE THE QUIET OF THE RADIO-FREE ENVIRONMENT” 
218 
ACCEPTANCE OF FLIGHT DATA CONSOLE 
(Negative) 
A number of problems were identified with use of the Flight 
Data Console. Many of these were a function of it being a 
temporary installation. The human engineering aspects were 
far from optimum. This means that a number of human factors 
issues must be addressed if-a data link system is to achieve 
its potential. Care must be taken in placing the system in 
the cockpit. Message content must be matched to pilot needs, 
instrument scan must be considered, and display complexity 
should not be great. 
A second negative comment deals with the information 
restriction imposed through use of a data link system. In some 
measure, these comments were relieved by the incorporation of a 
backup voice channel for later project flights. 
ACCEPTANCE COMMENTS 
ON FLIGHT DATA CONSOLE 
NON-ACCEPTANCE 
0 HUMAN ENGINEERING 
“POSITION OF FDC DETRACTS FROM SCAN” 
“EVERY TIME I USED IT, I HAD TO SCREW MY BODY 
INTO A WIERD CONTORTION” 
“DIFFICULT TO READ IN DAYLIGHT” 
0 INFORMATION RESTRICTION 
“VOICE SECURITY BLANKET IS SIGNIFICANT” 
“FDC TENDS TO FORCE GREATER RELIANCE ON ATC 
THAN I’M READY TO GIVE” 
“NOT ABLE TO QUESTION ATC” 
219 
VOICE CHANNEL 
The consensus of pilots who flew in the Phase I program 
was that a backup voice channel was needed with the Flight Data 
Console. This backup system was included in the Phase II 
flights. During the terminal area evaluations, the voice channel 
was used sparingly and principally to obtain confirmation of 
flight data provided through the Air Traffic Control system. 
USE OF BACK-UP VOICE CHANNEL 
IN TERMINAL AREA OPERATIONS 
NUMBER 
OF USES INFORMATION 
4 REQUESTED ATIS INFORMATION 
4 VERIFIED TYPE OF APPROACH 
3 CHECKED WIND CONDITIONS 
1 CONFIRMED ALTITUDE AND VECTOR COMMANDS 
1 VERIFIED MINIMUM ALTITUDE 
1 VERIFIED CLEARANCE 
220 
SINGLE-PILOT INSTRUMENT FLIGHT 
Four pilots flew IFR missions under full instrument weather 
conditions over routes on the order of 250 nautical miles. The 
purpose was to develop a typical flight scenario as an aid in 
studying problems of pilot workload and information acquisition. 
The performance ratings given the subject pilots by the 
safety pilot, who was a qualified instrument flight instructor, 
ranged from eight (quite a good score) to one (marginally above 
unsatisfactory). The number of unsafe occurrences noted, each 
of which would have been disqualifying in a flight test, ranged 
from zero to eleven. The differences in the evaluation data 
among the four pilots were considerable: a much wider disparity 
than expected. In an attempt to account for this, several 
variables were examined, principally dealing with flight time. 
The correlation between "rating by safety pilot" and "instrument 
time - last six months" was quite high. Since this measure of 
time ranged from eight to 40 hours, it is apparent that main- 
tenance of instrument proficiency requires that one fly quite 
frequently under instrument conditions. 
COMPARISON OF PERFORMANCE 
AND EXPERIENCE FOR SUBJECT PILOTS 
(ENROUTE FLIGHTS) 
SUBJECT PILOTS 
(N=4) 
RATING BY SAFETY PILOT’ 1 - 8 
TOTAL TIME (HRS.) 425 - 2000 
TOTAL INSTRUMENT TIME 30 - 250 
INSTRUMENT TIME- LAST SIX MONTHS 8- 40 
UNSAFE OCCURRENCES (NO.) o- 11 
‘10 = EXCELLENT, 0 - UNSATISFACTORY 
221 
SINGLE-PILOT IFR VERSUS FDC WITH VOICE 
The performance of the four pilots who flew IFR missions 
under full instrument weather conditions with no aid (FDC or 
copilot) was compared to their performance in four comparable 
flights over different routes using the Flight Data Console with 
the backup voice channel. In all, a measure of improvement was 
seen when the FDC was used. Performance ratings improved on the 
low end from a rating of one to three. The number of unsafe 
occurrences noted in any one flight decreased from 11 to five. 
ENROUTE FLIGHT PERFORMANCE COMPARING 
FLIGHT DATA CONSOLE WITH 
VOICE AGAINST SINGLE-PILOT IFR 
SUBJECT PILOTS 
SINGLE-PILOT IFR (N=4) 
PERFORMANCE RATING BY SAFETY PILOT’ 1 - 8 
UNSAFE OCCURRENCES (No.1 0 - 11 
FDC WITH VOICE 
PERFORMANCE RATING BY SAFETY PILOT 3 - a 
UNSAFE OCCURRENCES (No.) 1 - 5 
‘10 - EXCELLENT, 0 = UNSATISFACTORY 
222 
COMPARISON OF THREE FLIGHT CONDITIONS 
At the completion of the final full-mission flight, the 
four subject pilots were asked to rank the three flight condi- 
tions, shown in this Table, along the three dimensions of 
safety, workload, and pilot preference. Some caution must be 
expressed with respect to the validity of these relative 
rankings. Subjects were asked to compare flight conditions for 
which their recency of experience varied greatly. In one case, 
they had just completed a certain flight condition (Flight Data 
Console/Voice) and could judge it with some validity. With the 
other two conditions, the evaluation was based on long-term 
memory and is open to some question. In any event, the results 
did show that the flight condition represented by the use of 
the Flight Data Console with a backup voice channel was consider- 
ed to be safest, to impose the lightest workload, and to be most 
preferred by these pilots. 
RANKINGS OF THREE FLIGHT CONDITIONS 
FOLLOWING FULL-MISSION IFR FLIGHTS 
FLIGHT CONDITION SAFETY WORKLOAD PREFERENCE 
FLIGHT DATA CONSOLE / VOICE 3.0 1.3 3.0 
FLIGHT DATA CONSOLE 1.5 2.0 1.5 
SINGLE-PILOT IFR 1.5 2.8 1.5 
SAFETY: 3 = MOST, 1 - LEAST 
WORKLOAD: 3 = HEAVIEST, 1 = LIGHTEST 
PREFERENCE: 3 - MOST, 1 - LEAST 
223 
CONCLUSIONS 
The current voice communications system used in Air Traffic 
Control requires manipulation of radio equipment, read-back of 
clearances, and mental storage of critical information items, 
all of which contributes to high workload and an excessive error 
rate, particularly during single-pilot operations. This study 
indicates that use of a data link communications system has 
considerable potential for alleviating these problems and 
improving cockpit data management during general aviation 
operations. The specific conclusions of this project are 
presented in succinct form below. 
DATA LINK COMMUNICATIONS 
0 WELL RECEIVED AND USED BY GA PILOTS 
0 SHOULD IMPROVE PROFICIENCY OF SINGLE-PILOT IFR SIGNIFICANTLY 
0 REQUIRES BACK-UP VOICE CHANNEL 
0 RESEARCH NEEDS 
- HUMAN ENGINEERING 
- INFORMATION SELECTION AND FORMATTING 
SINGLE-PILOT IFR 
0 WORKLOAD HEAVIEST DURING LANDING APPROACH 
I 0 DIFFICULT TO ACCOMPLISH SAFELY WITHOUT CONSIDERABLE PROFICIENCY FLYING 
224 


A flight investigation of simulated data link communications during single-pilot IFR flight

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