VERTICAL

of eyes during
shift of gaze.

(from Braus ~1946)

"B

ATTITUDE ovro? |
(artificial Horizon)

Sinatrument
Panel

“CLIP" BOARD
(On lop)

Fieure 19. Vertical viewing angles associated with performance of

“two-task” patterns—flying aircraft and solving
mathematical problems on a lap-supported clip board. Cue lights

were within vertical angles of 82-34 degrees,

18


ment was 22.7% (p=0.01). Also, there was a
direct correlation between flight performance and

number of computations completed; the correla-
tion of mean scores was 866,

Instrument Ponel Percent Time*
‘ond Cue Light Foveal Vision
Display Mode: on Extra Task

Percent Diffe
B-A
CA

rence: | Percent increase of
Time Foveal Vision
Devoted to Extra Task

A (No Lights) 49.3

B (with Lignts)| 65.6

16.3 33.0%

(16.3749.3)

C tishts ony} 653

16.0 32.4%

(16.0749.3)

* Percent of total time available.

Froune 12. Visual attention to extra task as a function of use of peripheral cue lights,

Direction of Visual Attention. The amount of
time the subjects’ eyes were directed toward the
mathematical task, (as compared to time look-
ing elsewhere), is shown in Figure 12; the means
are 49.3%, 65.6%, and 65.3% for display Modes
A, B, and ©, respectively. Statistical analyses
indicated that significantly (p=0.05) more time
was spent looking elsewhere (primarily at the in-
strument panel) in Mode A ag compared with
Mode B and Mode C; the latter two did not differ
significantly from each other.

A summation of the flight and mathematical
task performance is shown in Figure 13. When
the peripheral cue lights were added to the nor-
mal instrument panel display (top line), flight
performance for a given task mode was better
than for the other display modes. Extra task
performance, as revealed by the vertical bars at
the bottom of the chart, demonstrates the varia-
tions in improvement as they relate to various
display modes and use of the peripheral cue
lights.

The means, standard deviations, and observed
ranges of flight performance are shown in Figures
14 and 15 for patterns 10/11, and 13/14, Tespec-
tively. As indicated by the shift of the lower
bars to the right in each diagram, the addition
of peripheral cue lights improved performance
in both task modes. When the task was con-
fined solely to flying the aircraft, the perform-

12

ance range was condensed by addition of the cue
lights, reducing the spread between the lowest
and highest scores.

Heading Variation, Although a maximum
heading variation of 20° was considered an

appropria:
on the out

te performance “target” during flight
‘bound legs of the patterns, 385 (85.5%)

of the 450 patterns were flown within a smaller

range of
@ variatiot

10 degrees. Eleven percent involved
nm from 11 to 20 degrees; about 216%

deviated as much as 30°, Less than 1% (the
remainder) exceeded 31 degrees of heading varia-

tion.

The number of legs involving heading varia-
tions in excess of 10° ig shown in Figure 16;
in each case, it is evident that the least number

of deviati

‘ons occurred in patterns in which the

peripheral cue lights were available for use with
the normal instruments (patterns 2, 5, 8, 11, and

14). Intl

he 11°-20° and the 21°-30° ranges, de-

viations occurred 39% and 20% less often, re-
spectively, in Mode B (with cue lights) than in

Mode A.

The number of legs in which deviation in ex-
cess of 10° occurred averaged 6.5 for the single
task (flight only) patterns and 17.3 in the two-

task (flig]
However,
A in whi
available.

‘ht and mathematical tasks) patterns,
almost 80% of the latter were in Mode
ich the peripheral cue lights were not


Ficure 2. The attitude indicator (artificial horizon)
provides pitch and roll information simultaneously.
The horizon bar (arrow #1) moves vertically in
relation to the fixed aircraft symbol (arrow #2)
to indicate an up of down nose (pitch) attitude.
‘The bar rotates to the left or right to show bank
(roll). Angle of bank is shown by relationship of
the moving pointer (arrow #3) to the fixed indices
on the periphery of the instrument face.

available, a pilot has no trouble in keeping his
aircraft on an even keel, even when diverting
his attention to tasks within the cockpit. Ap-
parently, some visual reference is maintained
peripherally with the outside world, providing
the pilot with information to correct any un-
desired change in the aircraft’s roll or pitch at-
titude. (Although the degree to which peripheral
vision cues are used to correct or maintain air-
craft attitude during “contact” weather is un-
known, some preliminary research information
recently obtained in this laboratory has demon-
strated that controlling aircraft attitude by visual
reference to the outside world becomes more dif-
ficult when the pilot’s peripheral vision is re-
stricted to a subtended angle of less than 5°).
Unlike contact flying, peripheral cues are non-
existent during instrument flight conditions, due
to loss of reference to the outside world—and
because of the nature of contemporary instrument
design, This forces the pilot to depend on central
vision to obtain accurate roll and pitch infor-
mation from the attitude indicator.

From the foregoing, it is apparent that instru-
ment flying involves two sets of visual tasks that
are basically in conflict with each other; ie,
(1) obtaining continuous information on aircraft
attitude by use of foveal vision, and (2) per-
forming other cockpit duties that also require
use of foveal vision. Obviously, any major varia-
tion in apportionment of visual attention may
detract from the total efficiency of the overall
flight task. If an emergency occurs, such as
failure of an engine, attention probably will be
diverted from the flight instruments, further ran-
domizing the attitude data received through the
pilot’s eyes. As the acquisition of these discrete
data becomes less frequent, the pilot’s response
may become erratic, further complicating the
task of flying the aircraft in a smooth and safe
manner.

Ideally, the solution to the problem may be to
cue the pilot continuously—rather than intermit-
tently—on all functions of the aircraft. From a
practical point of view, this would appear to be
an impossibility. However, jf none other than
roll data were absorbed continuously, this alone
would serve to make the flight task easier and less
fatiguing.

There are several ways in which continuous
roll information could be fed to the pilot: e.g., by
aural signals; presure against the body (such as
on the side of the shoulders or hips, or against
the legs or feet) ; rotary or lateral displacement
of the control wheel or stick; differential expan-
sion of the hand grips on the wheel or stick;
and/or visual signals acting peripherally and/or
foveally. Since, as mentioned previously, pe-

Ficune 3, Pilot response to peripheral vision cues was
studied using two sets of small colored lights at-
tached to pilot’s control wheel in aircraft simulator.
Upper bulbs were red, lower ones green. (Installa-
tion shown here is in Boeing 720 simulator.)



3.

a

n

2

10.

11.

12.

13.

4.

15.

. Ferree, ©. D., & RAND,

BIBLIOGRAPHY

. Bamey, R. W.: Color Vision Deficiencies in Army

Fliers. USA Aeromedical Research Unit, Ft. Rucker,
Ala, USAARU Report No. 65-2, April, 1965.

Bartarp, J. W., & Hessinarr, R.W.: Human Engi-
neered Electro-Mechanical Tactual Sensory Control
System, Elec. Mfg., 1954, 54, No, 4, 118.

CHapanis, A.: How We See: A Summary of Basic
Principles. A Survey Report on Human Factors in
Undersea Warfare. Committee on Undersea Warfare.
National Research Council, Wash., D.C., 1949.

Com, B. 1, Mrtron, J. L, & Motnsoss, B. B.:
Routine Maneuvers Under Day and Night Conditions,
Using an Experimental Panel. USAF, WADC TR-
58-220, March, 1054.

Datsow, T. L.:AC-105, Civil Aeromedical Institute,
Federal Aviation Administration : Personal communi-
cation.

G.: Chromatic Thresholds of
Sensation from Center to Periphery of the Retina and
heir Bearing on Color Theory. Psychol. Rev., 1919,
26, 16-41; 150-163.

Firts, P. M., & Jones, R. E.: Psychological Aspects
of Instrument Display: 1: Analysis of 270 Pilot
Error Experiences in Reading and Interpreting Air-
craft Instruments. Memorandum Report TSEAA-
694 12A, USAF, AMC, ‘Aeromedical Lab., Wright-
Patterson AFB, Dayton, Ohio, October, 1947.

Froyp, W. F., & WELFoRp, A. T.: Symposium on
Human Factors in Equipment Design. H. K. Lewis
& Co., Ltd., London, 1954.

Garner, C. A., & OBERMAYER, R. W.: Pilot Eye Fixa-
tions While Flying Selected Maneuvers Using Two
Instrument Panels. Bunker-Ramo Corp., Canoga
Park, California, October, 1964.

GuraTHewoBL, S. J.: Conspicuity of Steady and
Flashing Light Signals: Variation of Contrast. J.
Opt. Soc. Amer., 1953, 48 567-571.

Conspicuity of Flashing Light
J.

GeraTHEWworL, S. J.:
Signals of Different Frequency and Duration.
Exp. Psy., 1954, 48, 247-251.

GeraTHEWoORL, S. J.: Conspicuity of Flashing Light
Signals: Effects of Variation among Frequency, Du-
ration, and Contrast of the Signals. J. Opt. Soc.
Amer, 1957, 47, 27-29.

Gortne, S. M.: MS-250, Information & Statistics
Division, Office of Management Services, Federal
Aviation Administration: Personal communication.

Hoveson, D. A.: Preliminary Studies of Auditory
Flight Control Displays. The Boeing Company, Air-
plane Division, Renton, Wash. Report #D6-57104
1966,

Horxrn, V. D.: A Selective Review of Peripheral
Vision. Flying Personnel Research Committee, In-
stitute of Aviation Medicine, Royal Air Force, Farn-
borough, June, 1959.

19

16.

Ww.

18.

19.

20.

21.

22.

25.

26.

27.

29.

30.

Minroy, J. L., & Fitts, P. M.: Fre-
quency, Duration, and Sequence of Fixations During
Routine Instrument Flight. AF-TR-5975. USAF,
AMC, Wright-Patterson AFB, Dayton, Ohio, 1949,

Kugin, G. S.: The Relation Between Motion and
Form Acuity in Para-Foveal and Peripheral Vision
and Related Phenomena. ‘Arch. Psychol., 1942, 275,
m1.

Low, F. N.: The Peripheral Visual Acuity of 100
Subjects. Dept. of Anatomy, School of Medicine,
Univ. of N. Carolina, Chapel Hill, June, 1943.

McCormick, B, J.: Human Engineering. New York:
McGraw-Hill, Inc., 1957.

Jonzs, R. E.,

Merron, ©. B., Hicorns, B. A. Satotvar, iT, &
Wicks, S. M.: Exposure of Men to Intermittent
Photic Stimulation Under Simulated IR Conditions.
OAM Report No. 66-39, Oklahoma City, Okla., 1966.

Muon, J. L, Jones, R. B., & Frits, P. M.: Fre-
quency, Duration, and Sequence of Fixations When
Flying Selected Maneuvers During Instrument and
Visual Flight Conditions. ‘AF-TR-6018, USAF, AMC,
Wright-Patterson AI'B, Dayton, Ohio, 1950.

Minton, J. L., McInros#, B. B., & Com, EB. L.: Fixa-
tions During Day and Night GCA Approaches Using
an Experimental Instrument Panel Arrangement.
AF-TR-6709, USAF, AMC, Aeromedical Lab.,
‘Wright-Patterson AFB, Dayton, Ohio, February, 1952.

Mitton, J. L., & WOLFE, F. J.: Fixations During
Zero-Reader Approaches in a Jet Aircraft. WADC-
|TR-52-17, USAF, AMC, Wright-Patterson AFB,

Dayton, Ohio, February, 1952.

. Runpe, ©. A.: Retinal Chromatic Fields as a Fune-

tion of Wave Length. J.
833-856.

Opt. Soc. Amer., 1982, 22

varrerm, L. L.: Displays for Seeing Without Look-
ing. Human Factors, 1966, 8 No. 6.

waire, W. J.: Acceleration and Vision. Wright Air
Development Center Report 58-833, Air Research &
Develop. Command, Wright-Patterson AFB, Ohio.

ASTIA Document No. AD 208147, Nov., 1958.

wrraMmson, W. R.: A Prototype Peripheral Vision
Aircraft Attitude Display. Report #AFFDL-TR-66-
91. Air Force Flight Dynamics Lab., Wright-Patter-
son AFB, Ohio, October, 1966.

. Woopson, W. E., & Conover, D. W.: Human Engi-

neering Guide for Equipment Designers.
Univ. of Calif. Press, Berkeley, 1964.

Los Angeles :

‘WoopworTH,
Psychology,
8-106.

R. S., & ScutosneRs, H.: Bsxperimental
Henry Holt and Co. New York, 1965,

Wotreck, J. W., Ws1sz, A. & Razen, M. W.: Vision
in Military Aviation, WADC TR-58-399, Wright-
Patterson AFB, Ohio, 1958, 180; 211; 296.



Rint
tight
r

ights mounted on contro! whee!)

‘88°

EYE FIXATION
TARGET

Right light ~
Lett aye

LEFT EYE VISION

=e

ROTATION

Ficvre 17, Head rotation and

angles of peripheral cue discrimination (left eye) ;

testing of lateral discrimina-

tion of peripheral cues indicated cues were recognizable by the left eye at a maximum of 90° when central

vision was fixated to the right,

speed, heading indicator, and attitude indicator)
occupied more than % of the pilots’ visual atten-
tion. Thus, it is possible that with experience in
the use of peripheral cues for bank angle control,
pilots might reduce their fixation time on the
instrument panel by at least half.

Two interesting aspects of the study were (a)
the quick manner in which the subjects adapted
to the use of peripheral vision cues and (b) the
angles within which the light cues were recogniz-
able (Figures 17, 18, and 19). However, despite
these and other apparent advantages of using
this “secondary” visual sense, research should be
conducted in actual flight to determine whether
any in-flight factors (e.g., acceleration) might
significantly change the results found in the
Present study. If such factors do not prove to
be a problem, consideration might then be given
to adding a peripheral vision cue system to the
pilot’s information display.

IV. Summary.
1. During contact (or good weather) (VFR)

16

flight, many of the visual cues used by a pilot
to control his aircraft are received through his
peripheral vision receptors.

2. During instrument flight, on the other hand,
central vision is used to obtain discrete data,
necessitating numerous eye movements and fixa-
tions,

4. When peripheral vision cues are added. to
the instrument display environment, flight per-
formance is improved, particularly when addi-
tional tasks are added to the pilot’s flight duties.

V. Recommendation.

Additional research should be undertaken to
explore more effective means of utilizing human
Sensory capabilities for the reception and use of
aircraft orientation information,


instrument panel (without the attitude indicator)
was available and in which the peripheral lights
were the only source of information on bank
angle.

TASKS
arsruar “Shromaitin” — owt Tums veer ‘oHT TURNS
Mooe —_Provoen ar: UTS tins

aTtituoe | =e oe RT Te
A | woicator 1 I fa, 71 to) | hts
ONLY I |
ATTITUDE 1 il
B | inoicator 8) is & i) &
8 LIGHTS
+ t
wens A) IS 1 fe) tf
Cl mw 8 i € 8'4

FLIGHT With
MATHEMATICAL PROBLEMS

Fieure 7. Experimental design, Each subject flew 15
“race-track” holding patterns in the direction and
in the numbered Sequence shown. The three types
of bank angle cues available to the subjects are
shown at the left and are referred to in the text
as Modes A, B, and C. Mathematical problems were
worked simultaneously while flying the aircraft in
Patterns 4 through 12,

The turn and slip indicator was covered during
the entire experiment, since this instrument is not
routinely used by most instrument pilots.

Twelve of the 15 patterns involved turns to
the right; the remainder (Nos. 7, 8, and 9) were
to the left. During the first three and last three
patterns the subjects were not required to accom-
plish any mathematical task in conjunction with
the flight task, Thus, the first three patterns
(No. 1, 2, 3) were utilized primarily to establish

a minimum flight performance baseline; data .

from the last three (Nos. 13, 14, 15) were used to
obtain the end point of any learning curve that
might become evident. The middle nine patterns
(Nos. 4, 5, 6, 7, 8, 9, 10, 11, and 12) provided
data on the ability of the subjects to perform
the flight and mathematical tasks simultaneously.

Experimental Procedure. The patterns were
flown in the order shown in Figure 8. Each pat-
tern consisted of four parts: (1) a 60-second in-
bound leg* in which the aircraft was flown on a
north heading and at an altitude of 4,000 feet,
(2) a level turn (a turn in which a given altitude
is maintained), utilizing approximately 20 de-

* Data recorded from this segment of each Dattern were not
used because this Dortion of the pattern was utilized to stabilize

the simulator at the proper airspeed, heading, and altitude prior
to entry into the first turn.

grees of bank and involving a 180 degree change
of direction, (8) a 60 second outbound leg on a
south heading, and (4) a final, 20° banked turn,
with another 180° change of direction.

At the completion of the last turn of each
pattern, the alterations necessary to change from
one instrument display mode to another were
made rapidly by the observer; the peripheral cue
lights were activated for patterns No. 2, 3, 5, 6,
8, 9, 11, 12, 14, and 15 by operation of a switch
located at the right of the observer's seat, and the
attitude indicator was covered with an adhesive
plate for patterns No. 3, 6, 9, 12, and 15.

Also, the clip board with the appropriate math-
ematical test sheet was handed to the subject by
the observer during the first (inbound) leg of pat-
terns No. 4 through 12. The subject worked as
many problems as he felt he could do safely
while flying the aircraft through the first turn,
the southbound leg, and the final turn. After

used for patterns No, 4, 7, and 10; sheet No. 18
for Nos. 5, 8, and 11, and sheet No. 19 for pat-
terns No. 6, 9, and 19.

For a record of ey® movement (and unbe-
knownst to the subjects) the observer maintained
constant visual surveillance on the subjects’ eyes;
when their gaze was directed toward the work
sheet, the observer depressed a concealed switch
button, activating the recorder stylus. The same
individual was used to record the data on all 30
subjects,

After completion of the last pattern (No. 15),
each subject. was required to recover from steep
turns in each of two display modes; ie, (a) using
the normal panel (including attitude indicator)
but without the peripheral cue lights, and (b)
using only the cue lights (with all instruments
covered). In each instance, the subject kept his
hands off the control wheel and his eyes closed
until, after placing the aircraft in a bank of at
least 80° (direction of turn was unknown to the
subject), the observer rapidly centered the con-
trol wheel, removed his hands from the wheel
and instructed the subject to take control. The
subject then endeavored to place the aircraft in
a level flight attitude. These recoveries completed
the subject’s tasks; no subject was used more
than once in the study.


ripheral vision is used routinely during “contact”
or good-weather flying, it was decided to conduct
a study of pilot response to this type of visual
function as it might relate to controlling aircraft
roll attitude during instrument flight conditions.

II. Methodology.

Peripheral Cue Lights. Two sets of small
lights were used as cueing devices (Figure 8);
each set consisted of a red bulb and a green bulb.
One set was installed near the lower left corner
of the pilot’s control wheel ; the other was near
the right-hand corner. Activated by a camming
device connected to the roll servo of an aircraft
simulator computer (Figure 4), the left-hand
lights illuminated during left turns, and the
right-hand ones operated during right turns.

Jn contemplating the use of lights for periph-
eral cues, several factors are evident; first, the
lights should not add to the pilot’s perception
problems; second, their operation should not pro-
duce an irritating effect except when such an
effect is desired as a warning; and third, they
should produce the desired response as a rela-
tively natural function. Based on this, a “nega-
tive” cue (lack of any cue light illumination)
was used to inform the pilot when he was in rela-
tively level flight. To prevent continuous opera-
tion of the cue lights during level flight in rough
air, the non-illumination range involved a total
roll-angle range of six degrees—from zero to 8°,
left or right. Between 3° and 10° of roll, the
green light was set to flash once per second; from
40° to 18° the green light rate was doubled to
two flashes per second. To provide for turns in
the holding patterns, the green light illuminated
steadily in a 4° range from 18° to 22° of bank.
From 22° to 90° of bank, the green light was
extinguished and the red light flashed four times
per second.’

Flash durations of the lights were as follows:

Green—(1 flash/sec.) =0.185 sec. duration per
flash.
Green—(2 flashes/sec.) =0.125 sec. duration
per flash.
Red—(4 flashes/sec.) =0.100 sec. duration per
flash.
Thus, when the green light was flashing at a rate
of one flash per second, about 4 of each second
involved incandescence (exclusive of nigre-
scence) ; when the flash rate was two per second,

the bulb was lit for 44 of each second. When
the red light flashed, light radiation was ap-
parent for almost 4% of the total time (Figure 5).

FLASH FLASH FLASH FLASHES
COLOR TIMING DURATION PER SEC
GREEN EL] 0.185 SEC ONE
GREEN (Bf | 0.125 Sec TWO
reo @ EHH] 0.100 Sec FOUR

leet sec—el

FLASH (ILLUMINATION)
No ILLUMINATION

Ficure 5, Flash timing and duration of cue light il-
jumination was controlled by electro-mechanical
camming device installed in simulator computer
equipment.

Cockpit Illumination. General luminance
within the cockpit was the same for all subjects
but varied by areas, ranging from approximately
—2 log. foot lamberts (ft.-LL.) at the instru-
ment panel (under the glare shield) to 8 log.
ft.—-L. at the windshield. At the center of the
cockpit the luminance was about —.1 log ft.-L.
and at the side window it was .75 log. ft.-L. In
the pilot’s lap area it was about 2 log. ft—L.
The bulbs used for the cue lights were G. E.
4327's, using 0.04 amps at 28 volt, D.C., inserted
in Dialco 425-101-8830 transparent colored units
of 0.5 inch diameter. Luminance measurements
of the cue light sources indicated-a maximum of
2.6 log. ft.—L. for the green bulb and 3.2 log.
ft.—L. for the red.

Research Apparatus. A Curtis-Wright
Dehmel Convair 340 flight simulator was used.
In order to obtain performance charactertistics
similar to those of a light twin, such as a Cessna
310 or Beech Twin Bonanza, the simulator’s
speed and flight characteristics were altered by
appropriate changes in flap and power settings.

Data Recorded. Data recorded during the
flights consisted of the following, in relation to
time: (a) altitude—(feet), (b) bank angle (left
or right), in degrees, (¢) magnetic heading—
(degrees), (d) duration, flash rate and left/right
indication of green light, (e) duration, flash rate
and left/right indication of red light, (f) eye
movements (up or down) of subject, and (g)
number and accuracy of mathematical problems



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{ 43.5"
PILOT'S FLIGHT INSTRUMENT PANEL |
Sa a 3
|
|
!
|
EYE, FIXATION
TARGET |
Hy 1
i
|
RIGHT
LIGHT |
“(lights mounted on control wheel) 1
|
|
|
|
|
|
|
|
\

ROTATION

Ficure 18. Head rotation and angle of peripheral cue discrimination (right eye); lateral discrimination of
peripheral cues (Figure 17) was @ maximum of 62° for the right eye when fixated to the right.

17



Froure 6, Attitude indicator was covered

who had little or no instrument experience (the
subject with the least amount of flying time, for
example, also had no experience using an atti-
tude indicator). These limits consisted of main-
taining the inbound and outbound headings with-
in plus or minus 10 degrees, and altitude within
300’-& of the 4,000’ desired cruising altitude; an
approximate bank angle of 20° was designated
for the turns.

During a rest period in the cockpit (after the
familiarization flight and prior to flying the 15
patterns) each subject was given a page of simple
mathematical problems to solve (number facility
test forms #16, #17, #18, and #19 of the Louis
J. Moran Repetitive Measurements Battery) 3
each paper sheet, on a clip board, was kept on
the subject’s lap during this task. He was in-

(arrow) during five of the
shown covered (an extra heading indicator and a remote radio co!
strument flight and were not used during the study. In this photo,
forming mathematical task.

15 patterns, The two other instruments
mpass indicator) were not essential to in-
subject is maintaining level flight while per-

structed to solve the problems at his normal work-
ing rate. Data from these pre-flight sheets were
used during subsequent analyses to compare error

and working rates with

those of similar tasks

accomplished while flying the aircraft.
Instrument Display Modes. The patterns were

flown alternately in three instrument

modes (Figure 7) :

display

(a) Five patterns in which the full instrument
panel (including the attitude indicator) was
available, but in which the peripheral lights were

deactivated.

(b) Five patterns in which the full instrument
panel (including the attitude indicator) was
available and in which the peripheral lights also

provided bank angle information, and
(c) Five patterns in which only a

“partial”


AM 68-11

PILOT RESPONSE TO PERIPHERAL VISION CUES
DURING INSTRUMENT FLYING TASKS

A. Howard Hasbrook
and
Paul E. Young

Approved by Released by

J. Rosert Diz, M.D. P. V. Srecen, M.D.

Omir, Crvm Azromenican Insrrrurs Feperat Air Surckon
February 1968

DEPARTMENT OF TRANSPORTATION
FEDERAL AVIATION ADMINISTRATION

Office of Aviation Medicine



Eye Movement Data. “Eye-down”
jects’ eyes directed downward toward
matical task) in the various patterns
lated as a Percentage value of the total
for all three segments of each pattern,

time (sub-
the mathe-
was calcu-
time used

TIL. Results and Discussion.

Flight Performance. The mean flight perform-
ance scores, standard errors, standard deviations,
and observed ranges for each of the 15 patterns
are shown in Table 2. To determine whether
learning was a significant factor in producing the
flight performance scores shown in Figure 8,
appropriate F tests and t tests were conducted
on the scores for patterns 1 and 13; 4 and 7; 4
and 10; 2 and 14; 5 and 11; 3 and 15; 6 and 9;
6 and 12; and 9 and 12. No significant differ-
ences were found; thus, no learning factor ap-
peared to be present.

Tests were then applied to the differences be-
tween patterns 4 and 6; 4 and 12; 10 and 5;
10 and 6; 10 and 11; 10 and 12; and 13 and 14.
All patterns in which the peripheral cue lights
were available demonstrated performance scores
significantly better (p=.05 or greater) than those
without the lights (Table 3). The difference be-
tween patterns 6 and 10 was particularly interest-
ing since the subjéct was confronted for the first
time in pattern 6 with the task of flying the air-
craft with only the cue lights for bank angle
information while simultaneously solving arithe-
metical problems. In pattern 10, on the other
hand, the subject had already flown two similar
patterns while using the attitude indicator for
roll angle data. Despite his familiarity, flight
performance was better in No. 6 (with cue lights)
than in pattern 10 (without cue lights), further
indicating that learning was not a significant
factor.

Although the scores for the patterns involv-
ing turns to the left (Nos. 7, 8, and 9) were
slightly better than for the adjoining right-hand
patterns (perhaps due to roll bias in the simu-
lator), the differences were not statistically signi-
ficant. The data from both turns sets (Nos. 4,
7, 10; 5, 8, 11; and 6, 9, and 12) were thus com-
bined within the three respective display modes;
this resulted in mean scores for the patterns in-
volving the additional mathematical task of 55.9%
for Mode A, 67.2% for Mode B, and 64.3% for
Mode C.

10

ratios and level of
performance of 30

Tanue 3. Pattern comparisons, “t'?
Statistical significance of flight
subjects.

Pattern comparisons “

86
1.61
2.44
1.52

+90
2.99
3.33

+18
1.40
1.75

144

+93
3.35
2.30
3.76

+80
+58

Similarly, for those patterns in which no addi-
tional task was performed, data from patterns
1 and 18, 2 and 14, and 3 and 15 were grouped
together in their respective display modes. The
resulting mean scores for these were 78.1% for
Mode A, 84.6% for Mode B and 68.5% for
Mode ©.

These scores, shown in Figure 9, disclose a de-
crement in flight performance when another task
(one that takes the pilot’s visual attention away
from his instrument panel) is added to the flight
task. In Mode A, for example, flight perform-
ance decreased 23.5%; in Mode B (light cues
plus the attitude indictor), flight performance
decreased 20.6%. However, in Mode C (cue
lights only), flight performance decreased only
6.1%. In fact, this performance was only 8.8%
less than that when the subjects had only the
single task of flying the aircraft and could de-
vote continuous visual attention to the flight
instruments.

The effect of the use of peripheral cues on
flight performance for a given task mode is fur-
ther demonstrated in Figure 10. When the single
task of flying the aircraft is examined, it is evi-
dent that flight performance was improved by
15.7% when the cue lights were utilized. When
the mathematical task was added to the flight


Performance Criteria. The primary criterion ‘Tasur 2, Mean flight performance scores, standard

used for appraisal of flight performance was the
amount of time each subject was able to maintain

errors, standard deviations, and observed ranges of
30 subjects for each of the 15 holding patterns.

the desired bank angle in relation to the total

time available. For example, if the time available Display | Pat- |Mean Standard| Standard | Range
for maintaining the desired bank angle in the mode | tern error | deviation
two turns and the southbound leg was a total of
180 seconds (excluding “yo}]-in” and “roll-out” 1] 7.7 + 270 14.86
time, ie, the time used to roll from level flight 2 | 93.9 £ 1.89 10.39
to the desired bank angle of 20° and then, near 3 | 65.5 + 2.77 15.23
the end of the turn, to return to level flight), 44 51,8 + 2.54 13.96
and the subject maintained the desired bank angle 5 66.3 + 2 ° ° 85
for a total of 120 seconds, his flight performance ae ae = 3 3 11,83
for that pattern would be 66.6% (120/180= gt] 68.5 £ 2.46 13.54
0.666). Additional factors available for further 9*| 67.6 + 2.59 14.24
modification of the flight performance scores jn- 10*| 54.9 4 2.28 12,57
eluded variations of heading. altitude, airspeed, 114] 66.8 & 2.70 14.86
+ 12*| 63.8 + 3.08 16.97
and excessive bank angles. 413} 74.5 + 2.45 43.49
Secondary Task Criterion. Secondary task per- 14 | 85,3 + 1.45 8.00
formance during the middle nine patterns was based 15 | 71.6 + 2.54 18.96 | 35.6-89.4
onthenumber of mathematical problems completed
in each pattern, corrected to a baseline time period. *Patterns involving flight and mathematical tasks.

DISPLAY MODE

ean
A mf (\
i! ') vy

|

|

>a ra

(0

(NO LIGHT Ss) YU
717% 51.8% 56.9% 54.9%

BOG

(WITH LIGHTS)

C

(LIGHTS ONLY)

aC 2)
C2

o
©
a
x
o
a
©
x

Ce)
C2)
Cs)

65.5% 61.8% 67.6% 63.7% |

\ J

FLIGHT WITH
MATHEMATICAL PROBLEMS

d

a

74.5%

B

85.3%

a

71.6%

Figure 8. Mean flight task scores (percent of time at desired bank angle) of 30 subjects, each of whom flew the

45 holding patterns in the numerical sequence shown

9



completed. All but the last item were recorded
on a Sanborn 800 recorder; these data were then
transferred to punch cards for statistical
analyses.

Subjects. Since pilots of widely varying fly-
ing experience are involved in weather accidents,
thirty pilots with flight time ranging from 52
hours (this subject had only 11% hours of instru-
ment flight training) to 12,000 hours were used
as subjects (Table 1). Sixteen of the 30 were
qualified to fly by sole reference to instruments;
the others met only “visual flight rules” require-
ments. Eleven held private licenses, another
eleven were commercial pilots, and the remaining
eight held ATR ratings. All had a normal field
of vision as well as normal color vision accord-

TaBLE 1. Total flight hours of 30 subjects used to study
Pilot response to peripheral vision cues in aircraft

simulator.
Subject number | Hours Subject number | Hours

50 |] 16___ 900

54 1,200

55 1,400
115 1,500
145 2,500
154 4,600
160 4,000
170 -| 7,000
200 -| 7,400
221 -| 7,900
250 -| 8,000
300 -| 9,000
350 -| 9,000
400 -| 8,950
550 -| 12,500

ing to their FAA physical examination records,
Chosen in as random a manner as practicality
permitted, the group was divided almost equally
between pilots with less than 1,000 hours flying
experience and pilots with more than 1,000 hours.
The youngest subject was 19 years of age; the
eldest was 60 (mean, 38.6 years; standard devia-
tion, 10.8) resulting in a range of 27.8 to 49.4
years for % of the subjects. This compares fa-
vorably with the mean age and standard devia-
tion of all airmen certificated by the FAA in
1966 (35.1 and 10.8 years, respectively) of whom
approximately 66% ranged between 24.3 and 45.9
years.°

Each subject was given an identical one-hour
familiarization flight in the simulator; during
this time and while the subject flew the aircraft
in moderately banked turns and level flight,
maintaining an altitude of approximately 4,000’,
the observer (in the co-pilot’s seat) described the
use of the peripheral cue light system. At ap-
propriate times during the familiarization flight,
the instrument panel and peripheral lights were
used in the same three combinations (or modes)
subsequently used during the test runs; i.e. (a)
normal instrument panel with no lights, (b) nor-
mal panel with lights, and (c) panel with lights
but without the attitude indicator (Figure 6).
Just before the end of the familiarization flight,
the simulator was flown for five minutes by sole
use of the peripheral lights—with all of the
Hight instruments covered,

Simulator Test Standards. Prior to each
flight, all control functions and settings of the
simulator were standardized. Center of gravity,
gross weight, outside air temperature, barometric
pressure, flap angle, power and rpm, oil cooler
shutter position, trim tab settings, and all other
adjustments that might effect the aircraft’s per-
formance and feel were set the same for each
subject. Also, longitudinal trim was adjusted so
the aircraft would not normally diverge through
a range of more than 600 feet of altitude and/or
20 knots of airspeed during “hands-off” flight.
In addition, the pilot seat was adjusted so that
each subject’s eye position was at about the same
point in space.

Flight Patterns. Each subject was given two
tasks: (1) to fly 15 holding patterns within cer-
tain desired limits, and (2) to solve a series of
mathematical problems while flying nine of the
15 patterns. These patterns consisted of the
standard “race-track” holding type involving
(a) an approximate one-minute inbound leg, (b)
a 180° change of direction (using a 20° angle of
bank), (c) a one-minute outbound leg, and (d)
another 180° change of direction with 20° of
bank. Because of the speed (140 kts) and bank
angle, each turn required approximately 90 sec-
onds (when performed optimally); thus each
pattern consumed about five minutes—or a total
of about one hour and 15 minutes for all 15
patterns,

Two of the desired limits of operation were
purposely made rather “loose” to ‘accommodate
the assumed lesser flying ability of those subjects


Ficure 1. Flight instrument layout in Convair 340 airline type aircraft, Arrows point to pilot’s primary flight in-
struments (co-pilot has duplicate set on right side of panel). Attitude indicator is under top-center arrow.

where the aircraft may be subjected to high rates
of roll, this lapse of time can result in excessive
bank angles if the pilot is delayed in resuming
his scan pattern after performing some other task
in the cockpit. For this and other reasons, some
private plane owners spend relatively large sums
of money (as much as $13,000) to install auto-
matic flight control devices in their aircraft.
However, since only a small percentage of light-
planes are equipped with these devices, most pri-
vate pilots must keep their aircraft “right-side-
up” during turbulent IFR conditions by manual
means alone,

The attitude indicator is the only instrument
capable of providing pitch and roll cues simul-
taneously. It has a fixed, symbolic aircraft with
a moving horizontal bar that represents the real
horizon; these depict the angular relationship

between the actual horizon and the real aircraft,
If the attitude indicator is not observed every
few seconds—virtually to the exclusion of many
of the other flight instruments—it is difficult to
maintain desired aircraft attitude, particularly
in rough air. This is due to the roll character-
istics of many aircraft; even in smooth air, few
airplanes will fly “hands-off” for any length of
time without banking to one side or the other.
Of the three axes around which an aircraft can
rotate, control of the roll axis (bank angle) is
usually the most critical and the most important
in relation to control of speed and heading. Dur-
ing VFR* ( contact) flight, when visual reference
to the real world outside the cockpit is constantly

* “Visual Flight Rules.” A commonly used term meaning
that the weather conditions permit fight by visual reference

to the ground or natural horizon.


S LIGHTS & GYRO
LIGHTS ONLY
== GYRO (NO LIGHTS)

“7 1BUonr" rasn onty
i «FLIGHT @ MATH TASKS
= PATTERN NUMBI
sor fe) NUMBER 6
g
°
3
¢
s
8
8
x
%
g
=
.
5
2
ba
2
30r
e
8
g
$ Y Z
$ 7 y
rf ) 7
3 y) 7
Fed Z J
8 Z )
Fe Z Z
8 20+ Z 7
F 7 y
= J y
z 7 q g
= ~ az
| y)
aoe 788 Oui
PATTERNS

Fieuar 13. Flight and mathematical task performance
relationship; flight performance (solid and dashed
lines) decreased with addition of mathematical task
(bars). Least relative decrement occurred when
peripheral cues were used solely for roll angle in-
formation (middle line). Mathematical task per-
formance was lowest with conventional panel (no
peripheral cues) in Patterns 4, 7, and 10. (The word
“gyro” as used. herein refers to attitude indicator
instrument.)

Altitude Variation. Twenty-four of the 30 sub-
jects remained within an altitude range of 200
feet throughout all patterns; the remaining six
(20%) exceeded this range a total of nine times
but stayed within a range of 400 feet. Of these
nine events, seven occurred in turns, indicating
that level flight was less conducive to altitude
variation.

Flight Performance and Instrument Flying
Qualification. Of the 30 subjects, 18 (60%) were
qualified to fly solely by use of their normal flight
instruments without visual reference to the

13

PATTERN: CONDITION:

oR $0.50 OR
10 A No Lights (Gyro only)

1) CORNWZ— B osore

192036 40 50 60 70 80 90 100
FLIGHT TASK SCORE (%)

°

Ficure 14, Means, standard deviations, and observed
ranges of subjects’ flight task score while visual at-
tention divided between two tasks. (“Gyro” refers to
attitude indicator.)

PATTERN: CONDITION:

13

OR, $0.7 $0. OR,

A No Lights (Gyro only}

14

B Lights ond Gyro

o710 20 3040 86 60 70 80 90 100

FLIGHT TASK SCORE (%)

Figure 15. Means, standard deviations, and observed
ranges of subjects’ flight task score while visual at-
tention devoted solely to flight task. (“Gyro” refers:
to attitude indicator.)

ground or horizon. The remaining 12 did not
possess this qualification. The flight perform-
ance scores of these two groups are shown in
Table 4. Although there appears to be several
notable differences between the flight performance
of the two groups in several patterns (No. 6. 11,
18, and 15), no conclusions are drawn at this time
because of the small size of the sample and the
need for further study of other factors which
might bias the performance capabilities of two
such diverse groups.

Flight Performance and Total Flying Time.
The total flying time of each subject is shown in
Table 1. To obtain a clean division between so
called “low-time” and “high-time” pilots and still
maintain equal sample numbers, data for subjects
No. 15 and 16 were removed. This resulted in a
range of 50-400 hours for the low-time group
and_1,200-12,500 hours for the high-time group.

The flight performance scores for these two
groups are displayed in Table 4. Again, the
small size of the sample and the division of the
subjects into two arbitrary flight time groups
calls for additional study before any conclusions
might be drawn from the differences shown.



HEADING VARIATION

MODE (ie — 20°)
A 6) a cat He} He

\ 9 7 1 = 23
Biz 15 ei ll hal

1 3 1 4 o7 9
Cc 3 16 ot 2 Ht

6 4 5 3 o = 18

(21° — 30°)

A ) \4 7} 10 43)

1 2 1 1 Oo- 5
Bi 15 Cn Na

° ° 0 1 o-l
Cc 1 16 9} 2 45

2 ' 1 1 Oo 5

(31° +)

A ti 4 7 Hie) 413)

° 1 i Lo) Oo 2
Biz i) 8} Ma Na

0 fo ° Lo) Oo: 0
C is} ts En

fo fe fe) 1 1s 2

Froune 16, Number of heading variation events In ex
ress of 10 degrees during flight on outbound leg is
Shown on the right, ‘The least number of deviation
svents occurred in Mode B (peripheral cues added
to normal instrument display).

The dependence on vision for effective manual
control of aircraft during instrument flight—or
when precise but non-automatically stabilized
Aight is required—has necessarily centered on
the use of central vision. The reason for this is
evident upon examination of any instrument
panel in the average commercial airliner, general
aviation plane or military aircraft. Because of
design features, small size, and color and con-

15

trast combinations, precise information can be
obtained from aircraft instruments only by use
of central vision. In fact, only a portion of an
instrument dial can normally be perceived clearly
during a single fixation because of the decrease
in visual acuity at angles increasingly divergent
from the central axis of the eye.ot1® For ex-
ample, relative acuity is decreased by about 50%
at an angle of five degrees to the central axis, and
about 90% at 20°. At 40°-50° it is only about 5%
of central acuity.

In recognition of the pilot’s visual discrimi-
nation problem, some proposals have been made
for the use of auditory and pressure” (touch)
signals as possible means of reducing the visual
burden of the pilot. However, little attention
has been given to the possible use of peripheral
vision as a sensory aid for instrument flying ex-
cept by (a) Vallerie?> who studied the use of
peripheral vision as a means of eliminating time
normally spent. switching fixations between var-
jous instruments, (b) the development of the
British-Collins “Barber Pole” system now used
jn some highly sophisticated business aircraft, and
(c) a proposed device?’ that projects a lighted
image of a large horizon bar across the instru-
ment panel.

‘As the present study shows, use of peripheral
vision not only permitted a reduction in the work-
Joad imposed on the pilot’s central vision, but
also may have simplified the act of discrimina-
tion of direction of turn to a relatively auto-
matic function. This may be of operational sig-
nificance, when one considers the proportion of
time pilots normally spend looking at various
instruments during instrument flight; in a study
involving climbs while holding constant head-
ings, by Cole et al. 48% of the pilots’ visual at-
tention was devoted to looking at only two in-
struments—the heading indicator and the attitude
indicator. Since heading change is a function
of bank angle for a given speed, it becomes ob-
vious that if bank angle control can be maintained
with reasonable accuracy without the necessity of
looking at the attitude indicator, the proportion
of visual attention normally given to the head-
ing indicator may also be reduced. Also, if the
premise is accepted that a stabilized heading
induces constant airspeed—for a given power and
trim condition—it may be assumed that the air-
speed indicator would require less attention. As
shown by Cole’s study* three instruments (air-



PILOT RESPONSE TO PERIPHERAL VISION CUES DURING
INSTRUMENT FLYING TASKS

I. Introduction.

Flying an aircraft. by visual reference to the
ground or horizon is a relatively natural func-
tion compared to flying by sole reference to the
cockpit instruments. During instrument flying,
stimuli produced in the inner ear and deep
muscles of the lower torso are often in conflict
with visual cues provided by the flight instru-
ments. When this conflict occurs, the pilot may
disregard his visual sense in favor of the strong
sensations of balance and feel, and inadvertently
place his aircraft in an abnormal or hazardous
attitude.

In order to minimize the chances of such an
occurrence, instrument flight training stresses the
requirement for absolute dependence on the visual
senses, with almost total disregard for the sensa-
tions of balance and kinesthesia. This complete
dependence on vision requires nearly continuous
scanning of the flight instruments to assure con-
stant input of attitude information. Because of
this conflict between the senses, instrument flying
can be considered, from the physiological point
of view, as an “unnatura * human function, To
overcome the effects of this conflict requires a
great deal of initial training,* followed by pe-
riodie—recurrent—training.** In fact, ATR
(Air Transport. Rating) pilots employed by
scheduled airlines must also undergo an instru-
ment flight check every six months to demon-
strate an acceptable level of performance in flying
safely by sole reference to their instruments (US
PAR 191.441(b) (24)). Also, it may well be that
the additional time and expense involved in learn-
ing to fly by instrument has been a major factor
in deterring most private pilots from seeking this
additional training, for according to the FAA,

*“An applicant for an instrument rating must have at least
40 hours of instrument time under actual or simulated condi-
tions, including time acquired in @ synthetic trainer. ‘That time
must include at least 20 hours of flight time of which at least
15 hours must be instrument flight instruction given by a flight

instructor with an appropriate instrument rating on his flight
instructor certificate.” (US FAR 61.35,(¢) Amendment #24).

less than 3% of all U.S. private pilots held in-
strument ratings as of December 31, 1965."

The principal instruments used by a pilot to
control his aircraft during actual or simula’
instrument flight consist of six dial-type indi-
cators (Figure 1) which provide information on
airspeed, attitude, altitude, vertical speed (rate
of climb/descent), magnetic heading, and rate of
turn. Of the six instruments, the attitude indi-
cator (Figure 2) is the most important because
it is the only instrument that provides simul-
taneous information on both the pitch and bank
attitude of the aircraft.

However, the scanning of these flight instru-
ments must be expanded periodically to include
other instruments such as fuel flow meters, tem-
perature gauges, etc. Also, the scanning may be
interrupted for several seconds periodically to
study navigational charts, change radio fre-
quency, copy an ATC clearance and to perform
other tasks not directly associated with control-
ling the attitude of the airplane.

Because of the nature of contemporary instru-
ment design,?®”* little useful information can be
obtained from these displays unless direct vision
is employed. In present day cockpits, the pilot
must look directly at each indicator to obtain
accurate information. Because of this, minimal
scanning of the instruments js almost a full-time
job, even during routine IFR conditions.

Response of the pilot to visual stimuli requires
at least 1/5 second ;** in some cases, the time re-
quired to react muscularly may be as high as two
seconds.° ‘Thus, when two or three instruments
are viewed in succession, three to six seconds may
elapse from the time the pilot begins to scan the
instruments until the aircraft starts to respond
iv the pilot’s manual input. In severe turbulence

V+ "A pilot may not act as pilotin-command of an alreraft
under IFR (Instrument Flight Rules) or in weather conditions
Tues than prescribed VFR (Visual Flight Rules) minimume
Natess, in the preceding six calendar months, he has had st

Jeast six hours of instrument time under actual or simulated
instrument conditions... .” (US FAR 61.47(4))-



ACKNOWLEDGMENT

Many persons gave unstintingly of their time to bring this study to a
successful conclusion. Bart B, Cobb, AC-118, deserves first mention and our
gratitude for his assistance in statistical matters.

The pilots who cheerfully served as subjects were:

Gerald P. Abler Gordon Funkhouser John W. Mehew
Beuford E. Barnum Doyle Gregg William A. Morton
Dudley J. Bell, Jr. Ann M. Grissom Jack G. Myers
Hope Biggers Nelson Hall Rick Myers

E. E. Callaway Francis T. Hill C. D. Rea, Ph.D.
Don Catlin Spencer F. Houghton James M. Simpson
William C. Catlin Allan W. Hunting Richard P, Skully
R. H. Delafield, M.D, George Lotz, Jr. Eugene Trainer
George W. Dove Clark M. Mauldin Jim L. Turner

Jerry W. Forsythe Eugene L. Maulding Billy P. Updegraff

We are grateful to the personnel of the Aircraft Flight Simulation Sec-
tion, AC-959, FAA Academy, who kept the aircraft simulator and its asso-
ciated equipment and systems operating throughout the study.

Data reduction was completed on schedule by the combined efforts of:

Mary Ann Hatcher Joyce K. Mallory Michael D. Roe
Elizabeth Ann Hurst Rosalie J. Melton

A note of appreciation is extended to Theodore L, Dalbow, AC-130,
and Mrs. Margaret F. Shackelford, who spent many hours coordinating and
evaluating the data; and to Clyde C. Snow, Ph. D., AC-119, for his many
manuscript suggestions.

Grateful acknowledgment is also made to Eugene H. Barker, William
V. Flores, Betty P. Gatliff, William E. Geyer, and Gregg Winters for their
work in preparing the illustrative material for the report.

Qualified requesters may obtain Aviation Medical Reports from Defense Documentation
Center. The general Public may purchase from Clearinghouse for Federal Scientific and
Technical Information, U.S. Dept. of Commerce, Springfield, Va. 22151


instrument Panel

Flight Performance

Percent

Reduction In

‘ond Cue Light Without with Difference
Display Mode: Extra Tosk | Extra Task Flight Performance
(172/731)
A wo tints) | 73.1 | 55.9 | 17.2 23.5%
(17.4 184.6)
B twith cists) | 84.6 | 67.2 17.4 | 20.6%
(4.2 /68.5)

Cc (Lights Only)

68.5

64.3

42 6.1%

Figure 9. Flight performance as a function of additional task requirement.

Flight Performance Scores |
Task Mode Normal instrument Panel Display And: pitterence | Percent Increase in
Flight Performance
No Cue Lights | With Cue Lights
is/730
WITHOUT
9
mmo | 73,1 | 846 | 11.5 | 15.7%
71.3 758.9)
WITH
9
ge | BED | 672 | ILS | 20.2%

Froure 10. Flight performance as a function of use of peripheral cue lights.

task (lower line of chart) the use of peripheral
cues improved flight performance by 20.2%.
Mathematical Task Performance. As shown in
Figure 11, the means for the mathematical task
scores for display Modes A, B, and C were 22,

28, and 27, respectively. With cue lights added
to the normal panel (Mode B), task perform-
ance improved 27.2% (p=0.01) over that for
Mode A; when roll information was provided
solely by the lights, task performance improve-

Instrument Panel

i, Average Number Of Percent Increase In

and Cue Light Problems Worked Difference Problems Worked

Display Mode:

A\ (No Lights) 22
(28-22) (6/22)

B (with Lights) 28 6 27.2%
(27-22) (5/22)

Cc (Lights Only) a7 5 22. Th

Fieure 11.

Mathematical task performance as & function of use of peripheral cue lights.

it



Tanta 4. Mean scores of pilot flight performance in each of 15 holding patterns arranged according to qualification for

instrument flight and total flight hours.
Total flying hours
Qualified for Not qualified for
Display mode Pattern instrument flying | instrument flying
(N=16) (N=14) 1, 200-12, 500 50-400
“High Time” “Low Time”
1 73.4 69.1 71.7 70.2
2 85.3 81.8 86.1 80.0
3 64.5 67.2 61.4 68.9
4 51.2 52.8 49.4 52.9
5 65.2 68.1 64.8 67.8
6 58.7 66.3 57.9 67.1
7 57.4 56.1 56.4 58.1
8 67.0 70.7 65.1 70.1
9 67.3 68.1 64.0 71.5
10 54.8 54.9 54.2 54.6
ul 62.4 73.4 60.3 72.4
12 63.7 64.0 62.3 67.2
13 77.8 70.5 76.8 72.4
14 86.5 83.5 86.7 83.3
15 69.2 75.2 67.4 75.7
General Discussion, Many studies**.2422.22 have than

documented the large
which occur in insti
qualified instrument pilot may, at
100 or more eye movement
routine IFR flight.

that about 50% of a p:
primarily to viewing
tude indicator and th
another report*°

number of eye movements
Tument flying;

ts per minute during
Another study*® indicates
ilot’s eye movements relate
two instruments, the atti-
@ heading indicator. Still
shows that, on the average, more

the average
times, make from

little

tasks
the p
come

horizon—Table 5).
these findings that the average pilot has
time for additional visual duties during

routine instrument flight, and when non-routine

such as unexpected loss of power require
ilot’s attention, his visual channels can be-
overburdened. If this occurs, the pilot’s

overall performance may deteriorate.

Taptz 5. Percentage of eye fixation time devoted to individual instruments under various flight conditions,

Flight conditions

Instrument
Straight | Level turn | Climb | Ctimb turn| Descent | Descend ILAS GCA
and level ing turn | approach | approach

Directional Gyro. 37 26 20 21 24 25 49
Gyro Horizon. 25 29 24 22 25 15 19
Airspeed 7 12 24 24 10 17

13 2 3
Rate of Climb_ 2 5
Turn and Bank 1 2
Engine Instruments. 2 4
ILS Cross Pointer... 41 |. -