than did the other two display systems.
However, the lack of any statistically significant
difference between the scores for modes B and C
suggests that use of peripheral vision cues,
with or without availability of the attitude indi-
cator, provides comparable glide slope perform-
ance. In the latter case, control of the aircraft’s
pitch attitude had to be based on the pilot’s inte-
gration of data obtained visually from three in-
struments—the airspeed indicator, the vertical
speed indicator, and the glide slope/localizer in-
dicator.

Below Glide Slope. A rather unexpected find-
ing shows up with respect to time flown within
one dot below glide slope in the three display
modes; these were 43.30% in mode A, 39.30%
in mode B, and 31.10% in mode C. The mode C
time was significantly less (28%) than the
time flown below glide slope while using the
command bar/attitude indicator display in mode
A. In examining this difference of “below-
glide-slope” performance between modes A and
C, it is interesting to note there is little difference
between the times flown within one dot above
versus one dot below glide slope (c¢ vs. e) in
modes B and C (Figure 13). The scores are
32.80% (above) and 39.30% below in mode B,
and 33.50% above and 31.10% below in mode C.
On the other hand, there is a large, statistically
significant difference between the two in mode
A—26.95% above vs. 43.30% below.

Constant observation of the subjects’ eye move-
ments during the approaches showed a reduced
scan rate of the instrument panel in mode A
compared to mode C. In mode A, the subjects
tended to fixate on the command bar/attitude
indicator to the exclusion of other instruments.
In mode C appreciable visual attention was de-
voted to the vertical speed indicator, the glide
slope/localizer needles, the direction indicator,
and the airspeed.

A factor that may have accounted in part
for the extra time spent below glide slope in
mode A is the relatively large mass of the Boeing
720 (in this case, 170,000 pounds) in combination
with the relative movement between the command
bar and the aircraft symbol in the attitude indi-
cator. When this large mass descends below the
intended flight path the pilot must raise the real
aircraft’s nose for an appreciable time to arrest
the unwanted descent until the aircraft again
intercepts the glide slope. Such a pitch change

12

increases drag, slows the aircraft, and causes
nose “heaviness ;” this, in turn, causes the air-
craft to gradually pitch downward unless the
pilot holds sufficient back-pressure on the control
wheel to counteract this pitching moment. If
he fails to do so, the aircraft again descends
below the desired flight path. The difficulty of
accurately perceiving the small amount of pitch
change required to hold a proper pitch attitude
(sometimes as little as 4g inch relative movement
between the small symbolic aircraft and the com-
mand bar) may contribute to this error in per-
formance. On the other hand, movement of the
glide slope needle and vertical speed indicator
needles—necessarily used for pitch reference in
mode C—are much larger, permitting quicker
visual recognition of developing errors in pitch
control, thereby perhaps inhibiting excessive
decents below glide slope.

The means, standard errors, and standard
deviations for glide slope performance are shown
in Table 4.

Taste 4. Means, standard errors, and standard devia-
tions of glide slope performance relative to maintain-
ing aircraft within a total range of one-dot-deviation
above and below glide slope centerline.

Pattern | sean | S.D.
93,143.13 13.98
81.54:4,58 20.46
73,647.71 34.47
96.021. 45 6.50
84,644.07 18.18
77,747.43 33.22
94,941.91 8.55
87.444. 28 19,14
74,545.93 26.49

Localizer Performance. Performance related
to localizer path adherence is shown in Figure
14. As indicated in the column labeled “Com-
bined Means,” the average time “on” localizer*
in mode A was 58.25%; values for modes B and
C were 29.00% and 34.70%, respectively. The
differences between A and B, and A and C were
significant at the .01 level of confidence. There
was no significant difference between modes B
and C.

*Localizer needle within confines of “bulls-eye” circle
on instrument face.


Taste 1. Age and total flying time of 20 subjects.
(Mean age, standard error (S.E.), and standard
deviation (S.D.) were 45.7 years, £0.95, and 4.26.
Mean Flying Time, S.E., and S.D. were 9,795 hours,
895.4, and 4,002.5, respectively.]

Subject Age Total flight time
43 8,000
47 7,000
48 18, 400
45 9,000 Fraure 8a. In mode A, the peripheral cue lights were
48 6,800 deactivated and the primary flight instruments
45 12,000 shown here (including the “V” command bar
53 11, 000 (arrow)) were utilized during the ILS approaches.
48 8,000
34 7,200
43 12, 000
45 7,000
44 8,000
49 12, 000
47 5,700
46 8, 200
48 5,600
54 19, 500
43 15,000
44 9, 500
41 6,000

Ficurr 8b, In mode B, the peripheral cue lights were
available with the instruments shown (note that “V”
command bar was not available in this display
mode).

Ficure 2. Various flash rates (or steady state illumina-
tion) of green cue light (arrows) were used to indi-
cate different ranges of bank angle; flashing red
light (located above green bulb) indicated any bank
angle in excess of 26°. Right turns (banks) were
indicated by illumination of a right-hand light and
left turn by a left-hand light.

In display mode B, the V bar was deactivated,
requiring use of the Collins 331A~7 course devia-

tion indicator (CDI) to determine the relation- Fieure 3c. The attitude Indicator was covered in mode

ship between the real aircraft and the localizer c neces ating ne airspeed oe ne the vertical

- . . speed indicator ‘or pitch information, and the

and glide slope. See Figure 5. CDI (c) for glide slope and localizer data; the

In mode C, the attitude indicator was covered, peripheral vision cue lights (d) provided the only
necessitating use of the airspeed instrument (a, available information on bank angle.



REFERENCES

1. Hasproox, A, H., and Youna, P. E.: Pilot Response 2. Jacosus, Winr1aM. Collins Radio Company, Cedar

to Peripheral Vision Cues During Instrument Flying Rapids, Iowa. Personal communication, October 1967.
Tasks, Report AM 68-11, Oklahoma City, Okla., 3. United States Flight Inspection Manual. OA P
1968. 8200.1, Ch. 5, April 1965, 217-2 pp.

16


relationship of these one- and two-dot “cate-
gories” of performance to distance from the
centerline of the localizer and glide slope is shown
in Figure 8, where a vertical “slice” of a typical
localizer/glide slope “beam” is depicted at the
middle marker (about 3,500 feet from the runway
threshold). Here the beam is approximately 920
feet wide and 80 feet deep with its “floor” about
150 feet above ground (the beam is approxi-
mately 2,920 feet wide, 475 feet deep and 1,200
feet above runway elevation about 4 miles
further out from the runway). At the middle
marker, there are only 80 feet vertically between
the points represented by two dots above glide
slope and two dots below.

If a pilot keeps his aircraft within “tighter”
limits, such as between one dot above and one
dot below glide slope, his deviation would amount
to less than 40 feet vertically at the middle
marker. At the outer marker, the same deviation
would involve about 240 feet.

\

TYPICAL CROSS SECTION OF
BEAM AT MIDDLE MARKER

LOCALIZER CENTER LINE

The two hatched blocks in the beam in Figure
8, show the areas used in this study for compari-
son of pilot performance while flying the ILS
approaches. The center (dark) hatching repre-
sents the approximate range of “on” localizer,
“on” glide slope performance. The lighter
hatching shows the limits of the one-dot per-
formance range.

Bank Angle Performance. Comparison of the
percentage of time the aircraft was flown in a
wings-level attitude during the nine instrument
approaches (Figure 9, Tables 2 and 3), indicates
there might be significant differences between
subsequent runs in each of display modes A and
C (1 vs. 4 vs. 7 and 3 vs. 6 vs. 9). In fact, at
first glance, it would seem that learning was defi-
nitely related to the differences between ap-
proaches 3 and 6 in mode C, since use of the
peripheral cue lights, as the only available means
of ascertaining bank angle, was a relatively un-
familiar task. Also, there appears to be a large

ILS

2 doTs
ABOVE
GLIDE SLOPE

CENTERLINE
wy
“ont

GLIDE
SLOPE

\

a

We

} 2 bots
e BELOW
e GLIDE SLOPE
2 DOTS LEFT RUNWAY CENTERLINE
| OF CENTERLINE —“ON* LOCALIZER
GROUND

Frieure 8. Glide slope and localizer CDI display indications are shown relative to various locations within

the ILS “beam.”

At the middle marker, the aircraft shown here is approximately 20 feet below and 230

feet to the right of the glide slope/localizer centerline; the CDI display for this location indicates a one-dot

deviation (large arrow).


c. Ten minutes with the attitude indicator
covered and the pilot reading text material held
on the lap. This was done while simultaneously
flying the aircraft and making all bank angle
corrections only by means of the peripheral vision
cue lights.

The last portion of this familiarization flight
consisted of flying six standard holding patterns
while using the three instrument display modes
described earlier. While flying the last three
patterns, each subject also performed the second-
ary task of solving and writing answers to a
series of mathematical problems. These problems
were on a clipboard held on the subject’s lap.

Experimental Procedure. After completion of
the last pattern of the familiarization flight, each
subject was given a 5-minute rest period while
the copilot-observer positioned the aircraft 9
nautical miles from the outer compass locator on
the localizer path, in preparation for the instru-
ment landing approaches.

Nine ILS approaches were performed by each
subject in the sequence shown in Figure 6, with
each of the instrument/cue light display modes
used during the previous holding patterns. No
landings were made; instead, after descending to
an altitude of between 100 and 150 feet, the sub-
ject executed a “go-around,” climbing up to the
original approach altitude. The aircraft was
then immediately “backed-up” by a simulator
technician to the original starting point for the
next approach.

After completing the approaches, each subject
attempted to recover from a series of four
steeply-banked turns, in each of two instrument/
cue light display modes; ie., (a) with all flight
instruments available (including the attitude in-
dicator) but without the peripheral cue lights,
and (b) using only the cue lights (all flight in-
struments covered). In each case, while the air-
craft was being put into the unusual attitude by
the observer, the subject kept his hands and feet
free of the controls, and his eyes closed and
covered. After the control wheel was quickly
centered by the observer—without decreasing the
bank angle—the subject was told to take control.
He then attempted to roll the aircraft into level
flight attitude as rapidly as possible.

The sequence and details of the four recovery
maneuvers are as follows:

Power: 1.8 EPR.

Flaps: 30°.

Landing Gear: Retracted.

Recovery #1. Initiated from an attitude of:
Left wing down 60°
Nose up 10°.

Recovery #2. Initiated from an attitude of:
Right wing down 80°
Nose level.

Recoveries #1 and 2 made with all instruments
available (no peripheral vision cue lights).

Recovery #3. Initiated from an attitude of:

Right wing down 60°
Nose up 10°.
Recovery #4. Initiated from an attitude of:
Left wing down 80°
Nose level.

Recoveries #3 and 4 made by sole use of
peripheral vision cue lights (all instruments
covered).

"These recovery maneuvers completed the tasks.
No subject was used more than once in the study.

Performance Criteria. Three flight perform-
ance measures were used to compare the effects
of the three different instrument display modes
on pilot performance during the instrument ap-
proaches. These criteria were: (1) glide slope
deviation (2) localizer path deviation and (3)
bank angle—from the outer marker to the middle
marker, Flight time between these two geo-
graphical points was approximately 80 seconds
for each ILS approach. :

For purposes of analysis, variation of per-
formance on each criterion was categorized as
follows:

(1) Glide slope:

(a) “On course.”

(b) Above glide slope, to Ist dot.

(c) Below glide slope, to 1st dot.

(d) Between 1st and 2nd dot (above or be-
low glide slope).

(e) Beyond 2nd dot (above or below glide
slope).

(2) Localizer :

(a) “On course.”

(b) Left or right of “on course” to ist dot.
(c) Left or right between 1st and 2nd dot.
(d) Beyond 2nd dot (left or right).

(3) Wing attitude (bank angle) :

(a) “Level” (not more than 114° of bank,
left or right).

(b) Between 114° and 10° of bank, left or
right.



Figure 3c), and the vertical speed indicator (b)
for pitch information, the CDI (c) for glide
slope and localizer data, and the peripheral cue
lights (d) for bank angle information.

The CDI was available for use in all three dis-
play modes, providing glide slope, localizer, and
heading information. The “bulls-eye” and the
two dots above and below on the left side of the
instrument (Figure 5) are used to indicate the
relationship of the real aircraft to the centerline
of the glide slope “beam.” As shown in Figure
5, the glide slope needle (arrow #1) indicates
the aircraft is below glide slope by one dot. The
localizer on-course “bulls-eye” and off-course
“dots” on either side of the bulls-eye are at the
center of the instrument; the localizer needle
position (arrow #2) indicates the aircraft is to
the right of centerline by one dot. The relation-
ship of instrument readings to the physical posi-
tion of an aircraft with regard to magnitude of
deviation from glide slope and localizer is dis-
cussed in the results and discussion section.

Simulator Test Standards. Prior to each
flight, all applicable aircraft functions and set-
tings were standardized. Such variables as cen-

0

Figure 4. The “V" bars (arrow #1) in the Collins FD
108 attitude indicator provide the pilot with “com-
mand” information; i.e., “mating” the delta aircraft
symbol (arrow #2) with the “V” bars by appro-
priate pressure and displacement keeps the real air-
craft close to, or on, the centerline of the localizer
and glide slope.

ter of gravity, gross weight, outside air tempera-
ture, barometric pressure, fuel quantity, flap
angle, and power and trim settings were initially
set the same for each subject. The pilot’s seat
was also adjusted so that each subject’s eye posi-
tion was at about the same point in space.

Familiarization Procedure, Each subject flew
the “aircraft” for one hour prior to the simulated
instrument landing approaches. The “flight” was
conducted at an altitude of 3,000 feet above the
ground at approximately 170 knots; power was
1.8 engine pressure ratio (EPR) and the flaps
were extended 30°. The landing gear remained
retracted. Flight maneuvers were divided about
equally between level flight and turns with bank
angles up to 30°. The first portion of the flight
was conducted purely for familiarization pur-
poses with instrument and peripheral vision cue
light displays as follows:

1. Ten minutes without the peripheral cue
lights, divided equally between use of the attitude
indicator with and without the “V” command
bar.

2. Twenty minutes with peripheral cue lights.
This was subdivided into:

a, Five minutes using the attitude indicator
without the “V” bar.

b. Five minutes with the attitude indicator

Fravre 5, The Collins 381A~7 course deviation indica-
tor (CDI) provides glide slope, localizer, and head-
ing information. According to the positions of the
glide slope needle (arrow #1) and the localizer
needle (arrow #2), the aircraft is below glide slope
and to the right of the localizer by one dot.


APPENDIX

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17



(c) Between 10° and 22° of bank, left or
right.
(d) Between 22° and 26° of bank, left or
right.
(e) Beyond 26° of bank, left or right.
Measures are expressed as a percent of the
total transition time between the outer marker
and middle marker. Performance during re-
covery from the unusual attitudes (steeply-
banked turns) was related to the actual time re-
quired to roll the aircraft to less than 114° of
bank.

Ill. Results and Discussion.

The ILS Approach., In a perfectly executed
ILS (instrument) approach, an aircraft descends
along the line of intersection of the localizer
beam and glide path * (Figure 7). Also, assuming
no cross wind, the wings would remain level and
the aircraft’s heading would not vary from the
localizer heading.

However, few pilots can consistently execute
an instrument approach this perfectly because
of variations in pilot technique and experience,
fatigue, delays in aircraft response to control
inputs, and other such variables. Because of
these variables, a wide range of pilot performance
levels may be observed which are measurable as

VHE RUNWAY LOCALIZER
‘ TRANSMITTER

uNway
LENGTH
‘7000 FT.
(rypicat)

POINT OF INTERSECTION
RUNWAY AND GLIDE
PATH EXTENDED

.
UNF LIE sLoPE Sa,
TRANSMITTER

deviations above, below, and to either side of the
center of the localizer/glide-slope path.

For purposes of analysis, pilot performance
was evaluated in categories that would be mean-
ingful to pilots as well as to designers of instru-
ment display systems. For example, the ability
to hold the aircraft in a relatively wings-level
attitude (not more than 114° of bank) is indica-
tive of better performance than if the pilot allows
bank angle to vary widely and often; similarly,
a majority of the time spent “on glide slope”
constitutes better performance than if most of
the time is used flying above or below glide slope.
Also, flight above glide slope is more desirable
than flying an equal distance below glide slope,
because the latter places the aircraft closer to
the ground. Flight within one dot on either
side of the localizer centerline is preferable to
flying beyond one dot. Even less desirable
would be operation beyond the two-dot range,
for at the middle marker, the aircraft would be
too far to the side of the runway to be landed
successfully. Similarly, two dots above glide
slope might require a go-around, loss of time,
and another approach attempt. Two dots below
glide slope, on the other hand, places the air-
plane about 150 feet above ground at the middle
marker—lower than desirable and less safe. The

INSTRUMENT LANDING SYSTEM

OUTER MARKER

FROM 08° TO 1.5*
WITH FULL SCALE
YMMETRICAL
‘ABOUT AXIS.

INTERSECTION OF
LOCALIZER AND
GLIDE SLOPE
HORIZONTAL | *EAMS"
«ry!

Figure 7. Typical instrument landing system configuration.” Approach data used in study was obtained in area
between middle and outer markers.

7



AM 68-12

PERIPHERAL VISION CUES: THEIR EFFECT ON PILOT
PERFORMANCE DURING INSTRUMENT LANDING
APPROACHES AND RECOVERIES FROM UNUSUAL

ATTITUDES

A. Howard Hasbrook
Civil Aeromedical Institute

and
Paul E. Young
FAA Academy

(with the technical
assistance of N. S. Daniels,
T. L. Dalbow, and R. J. Melton)

Approved by Released by
S AA Z Sy PY C2 A PVT 9)
J. Roperr Ditir, M.D. P. V. Sreeer, M.D.
Cuter, Civin ArROMEDICAL Feveran Air Surcron
InstrruTE
May 1968

Department of Transportation

FEDERAL AVIATION ADMINISTRATION
Office of Aviation Medicine



MEAN BANK ANGLE SCORES
INSTRUMENT BANK ANGLE || APPROACH | MEANS || APPROACH | MEANS |} APPROACH | MEANS SoMeINED,
DISPLAY MODE : (DEGREES) |} SEQUENCE % SEQUENCE % SEQUENCE % Tens, of
lo) - 172 485 463 ait 43.70
WN to) 172 - 51.4 53.5 58.4 55.95
(A) iN ic) 10- 22 O.1 4 0.2 7 0.5 0.35
(a) 22-26 0.0 0.0 0.0 0.00
le) 26+ 0.0 0.0 0.0 0.00
(0) O- 172 47.7 51.2 53.8 52.50
fb) 1 172-10 49.5 46.9 44.5 45.70
(B) A ie) 10-22 2 2.5 5 1.9 8 7 1.80
(a) 22-26 0.3 0.0 0.0 0.00
le) .264 0.0 0.0 0.0 0.00
a) O- 1/2 44.6 55.9 55.5 55.70
tb) 11/2-10 48.8 40.5 44 40.80
(C) k: F ic) 10-22 3 6.0 6 3.2 9 3.4 3.30
(6) 22- 26 0.3 0.2 0.0 0.10
te) 26+ 0.3 0.2 0.0 0.10
LEGEND : ARTIFICIAL HORIZON WITH V COMMAND BAR ARTIFICIAL HORIZON CUE LIGHTS ONLY
° (no peripheral cue lights) WITH CUE LIGHTS (no artificial horizon)

Fieure 10. Mean

114° for substantially longer periods of time
when peripheral cue lights were available for
bank angle indication, than when using the atti-
tude indicator with the “V” command bar. For
example, the improvement in performance in ap-
proach #8 compared to that for approach #7 is
30.9% ; performance in approach #9 (cue lights
only) compared to approach #7 is even greater,
35.0%. (Figure 11).

The reason for this becomes apparent when
the two systems are compared in relation to re-
quirements for visual discrimination. The con-
ventional system in mode A requires the use of
central (foveal) vision for discrimination of
changes in bank angle. If the aircraft begins
to bank inadvertently while the pilot is looking
at other instruments, or is otherwise distracted,
the increase in bank angle will not be detected
until the pilot focuses directly on the attitude
indicator; by this time the bank angle may be
excessive. On the other hand, in modes B and
C, flashing of a peripheral cue light at banks in
excess of 114° causes the pilot to initiate cor-
rective action regardless of where his vision may
be directed at the moment.

The scores related to bank angles between 114°
and 10° (b, Figure 10) also demonstrate major

percentages of time flown at various bank angles during ILS approaches are shown in rela-
tion to three different instrument/cue light display modes.

"LEVEL" FLIGHT PERFORMANCE AS FUNCTION OF
INSTRUMENT DISPLAY MODE
pispLay | APPROACH | TIME IN DIFFERENCE | INCREASE
move: | Shomaer | eve ONT cy) om
aR 7 41.1
(53.8-41.1) (2.7741)
8 Ay 8 53.8 12.7 30.9
(55.5-41.1) (4.4/4)
Cc key 9 55.5 14.4 35.0
Ficure 11. Time in level flight (bank angles less than

144°) increased with use of peripheral vision cues.

differences; i.e., significant differences (p= <.01)
appear between the scores for 7b and 8b (58.4%
vs. 44.5%), and 7b and 9b (58.4% vs. 41.1%).
This strongly suggests that the peripheral cue
lights were useful in reducing the amount of
time the aircraft operated at bank angles between
114° and 10°.

For banks in excess of 10°, mean time was less
than 1 second in mode A and 2.8 seconds in mode
C (Figure 12).

10


reduction in performance in approach 7, as com-
pared to approach 1 (in which the most sophisti-
cated instrument display equipment was avail-
able to the pilot). However, appropriate ¢ tests
indicate there was no significant difference be-
tween the scores in any one display mode at the
p=<.05 probability level. Therefore, it is as-
sumed that learning did not contribute signifi-
cantly to the variation in scores in mode C, nor
could any significance be attributed to the ap-
parent decrease in performance shown in mode A.

However, statistically significant differences do
appear when the performance scores for the dif-
ferent instrument display modes are compared

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(Qi A) ARTIFICIAL HORIZON WITH CUE LIGHTS.
Lusty CUE LIGHTS ONLY (no artificial horizon).

Fieure 9. Mean scores of time in level flight (zero to

144° of bank) resulting from use of three different
display modes, Although there appears to be wide
differences between scores for approaches #8 and
#6 in mode C, #2 and #8 in mode B, and
#1 and #7 in mode A, the differences within any
one display mode were not statistically significant.
‘There were, however, significant differences between
modes; i.e, between approaches #7 and #8, and
between #7 and #9.

Taie 2. Means, standard errors, and standard devia-
tions for level flight (ero®—1.5°) between the outer
and middle markers during nine ILS approaches.

Approach number anne Standard

and display mode (sees. deviation
48,542.93 13.13
47,THA.58 20.48
44,645.74 25.69
46,342.98 13,32
51,244, 21 18.82
55.944, 56 20.40
41.143, 83 17.15
53, 843,95 17, 66
55,544.46 19.97

Tasie 3. Inter- and intra-display mode comparisons
of level flight performance (zero°—1.5° bank angle).

Approach and Significance
display mode “e Level
comparisons

3C-6C. 1.55
9C-3C. 1.49
6C-4A 1.77
9C-7A. 2.44
8B-7A. 2.30
2.49
1.77
1.07
1A-7A. 1.53
5+8B-4+7A_ 1.68
6+9C-4+7A_ 2.11
6+9C-5+8B-__-.-- 0.53 —

with each other (Figure 10). For example, there
is a significant difference (p=<.05) between the
scores for “level” flight in approach #4, mode
A with no cue lights (46.8%), and approach #6,
mode C with cue lights only (55.9%), The same
holds for approach #7 mode A (41.1%) and
#9 mode C (55.5%). Also, significant dif-
ferences are found between approach #7 mode
A (41.1%) and approaches #5 mode B (51.2%)
and #8 mode B (53.8%)—in which the pe-
ripheral cue lights were added to the attitude
indicator display.

It is apparent that, on the average, the pilots
were able to maintain a bank angle of less than



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Frecre 1. The instrument panel in the B-720 simulator used for the study of pilot response to peripheral vision
cues is typical of that in many airline aircraft.

left/right green and red (cue) light illumination,
and time of passage over outer and middle
markers (geographical points along the approach
path).

Subjects. Twenty pilots, all with air trans-
port ratings (ATR’s) with flight time ranging
from 5,600 hours to 19,500 hours were used as
subjects (Table 1). Ten were qualified in the
Boeing 720 airplane; the rest were qualified
either in the Convair 580 (turbo-prop model)
or in the Lockheed Electra L-188. Fourteen of
the 20 subjects reportedly had no familiarity
with the particular attitude indicator (Collins
108 with “V” command bar) installed in the
simulator.

Instrument Display Modes. The instrument
approaches were flown alternately in three dis-
play modes:

Mode A. “Full” instrument panel* (including

*The turn and slip indicator (‘T&B) was covered dur-
ing the entire experiment.

“command” bar in attitude indicator) but with
peripheral vision cue lights deactivated (Figure
Ba).

Mode B. Full instrument panel* (eacluding
command bar), with functioning peripheral cue
lights (Figure 3b).

Mode C. “Partial” instrument panel* (without
attitude indicator) with the peripheral cue lights
as the only source of bank angle information
(Figure 3c).

Attitude Indicator and Course Deviation In-
dicator Instruments. The attitude indicator in
the simulator was a Collins FD 108 (Figure 4).
In instrument display mode A, the inverted “V”
bar (arrow #1) provided the pilot with “com-
mand” information; i, in the “glide slope”
mode, “mating” of the delta aircraft symbol
(arrow #2) with the V bar by appropriate man-
ual control pressure and displacement keeps the
real aircraft on, or close to, the centerline of the
localizer and glide slope.


Differences between standard deviations for
on localizer performance were small, ranging
from a high of 24.37% (approach 6—mode C)
to a low of 20.93% in approach 9—mode C.

Maintenance of the aircraft within the con-
fines of one dot on either side of the localizer
path (including time “on” course) was accom-
plished with no significant difference between the
three display modes. However, as shown in
Table 5, there were wide variations in standard
deviation. In approaches 4 and 7 (mode A)
there was no variation but in approaches 5 and 8,
(mode B) the standard deviations were 7.14 and
11.87, respectively. In 6 and 9 (mode C) stand-

from similar bank angles while using the periph-
eral cue lights as the only flight display; mean
time for all subjects was 16.9 seconds with a
standard deviation of 2.8 seconds.

Of even greater interest was the fact that no
reversals (attempting to recover in the wrong di-
rection due to incorrect interpretation of avail-
able cues) occurred while using the peripheral

‘Tante 5. Means, standard errors, and standard devia-
tions of localizer performance relative to maintain-
ing aircraft within a total range of one-dot-deviation
on either side of localizer centerline.

ard deviations were 2.68 and 4.78, about one- Pattern xtS.B. x S.D.
third of those in mode B in which the attitude (sees.)
indi i «wy : i
indicator without the “V” bar was utilized. 99.640.40 1.79
. Recoveries from Unusual Attitudes. Time re- 92,444.69 20.97
quired to return the aircraft from 60° and 80° 88.346, 23 27.87
banks to a wings-level attitude is shown in Table 100 oO °
6. When the conventional instrument display 99. er 59 ses
was used (without assistance of peripheral cues) 100.04 0.00
the mean recovery time was 20.6 seconds with a 96. 542.65 11.87
standard deviation of 5.5 seconds, A significantly 98,941.06 4,78
lesser time (p=<.01) was required for recoveries
MEAN LOCALIZER SCORES
instrument |ROSITION.9 A/SI) approach | means || approacH | means || apPRoacH | MEANS || JeAeNG
pispLay Mope: | OF COCALIZER || SEQUENCE % SEQUENCE % SEQUENCE % (4 thru 9)
@ ~¢ 0.00
& © 9,00
(A) WN Ite 4 7 13.70
om
2 te)
= (f)
*@
fo) i
i od
m (b)
gg
a (ch
8) ys | 2 5 8 |
— 2 (e) °
= (f)
1 @
@
- Oe
go
4 &)
(C) fea oO 3 6 9
2B (e) 28.35
3 —e 0.55
xine 0.00
r DOTS LEFT OF
LEGEND: + CENTERLINE JX ARTIFICIAL HORIZON WITH V ARTIFICIAL HORIZON CUE LIGHTS
' 1 DOT RIGHT OF COMMAND BAR (no peripheral WITH CUE LIGHTS ONLY (no
iy CENTERLINE cue lights) artificial horizon)

Frcure 14. Mean scores of time flown “on” and to either side of the localizer centerline in relation to use of

three instrument/cue light display modes.

Time spent “on” localizer was significantly less in modes B and C,
but scores for flight within the confines of one dot to either side of center

were close in all three display modes;

Le,, mode A—100.00% ; mode B—96.90% ; and mode C—99.15%.

1B



to wings-level flight, and (2) pilot reaction, re-
covery technique and direction of initial and sub-
sequent recovery attempts.

Statistical tests of the data showed that use
of peripheral vision cue lights resulted in:

1, Improved performance in maintaining
wings-level flight ;

2. Less time flown below glide slope as com-
pared to that when all instruments (includ-
ing the command bar function of the Collins
108 system) were used ;

8. Comparable performance in maintaining
position within one dot of the localizer/glide
slope centerline, with or without the attitude
indicator;

4, Safe instrument approaches with a “failed”
attitude indicator using vertical speed indicator
primarily for pitch control; and

5. Improved performance in recoveries from
unusual attitudes with smoother control appli-
cation, less pitch oscillation, reduced airspeed
and altitude variation and less time required to
return to a wings-level attitude, with no reversals.

The improved performance in maintaining a
wings-level attitude during the instrument ap-
proaches was not unexpected, since the peripheral
vision cue lights alert the pilot to inadvertent
banks sooner than would normally occur while
using the conventional attitude indicator. This,
of course, serves to reduce variations in heading,
and in turn, allows more visual time to be de-
voted to other instruments.

The findings that a disproportionate amount
of time was spent below glide slope while using
the complete “108” instrument display system
was surprising and may have been due, in part,
to a lack of complete familiarity with the 108
instrument. Further investigation of this prob-
lem in flight might be desirable to determine
whether this occurs during actual instrument
approaches with pilots who are completely fa-
miliar with the display system.

The close similarity of performance in the two
display modes utilizing the peripheral vision
cues—with and without the attitude indicator—
presents several interesting questions. Since the
peripheral cues relate directly to bank angle only,
how were the subjects able to consistently make

15

safe ILS approaches without the customary
pitch angle cues normally obtained from the
attitude indicator? It may be assumed that this
was accomplished by using information obtained
from either the vertical speed indicator, the glide
slope needle, the air-speed, or all three. Could
the same results have been achieved with cues
from only one of these three instruments? Ad-
ditional research will be in order to answer these
and other closely related questions for, in the
opinion of these investigators, much remains to
be done in developing a display system that more
closely fits the psychophysiological demands made
on the pilot. Centainly, it is most interesting
that pilots with little or no previous experience
in making ILS approaches without an attitude
indicator were able to do so—easily and safely—
by use of a relatively strange display system.

Lack of reversals while using only peripheral
vision cues for recoveries from unusual attitudes
(compared to the occurrence of reversals with the
conventional instrument display) suggests a
human factors design deficiency in present day
attitude indicators, even in those with a marked
color differentiation between sky and ground on
the face of the instrument. In addition, the
demonstrated lack of hesitation in recovering in
the proper direction wheri using peripheral vision
cues implies a very definite need for improving
present methods of providing the pilot with air-
craft attitude information.

Also, it is of interest that when the subjects
were concerned only with rolling the airplane
to a wings-level attitude (by use of the peripheral
cues and without the necessity of monitoring
pitch attitude, airspeed, and altitude) recovery
technique was smoother with less “manhandling”
of the controls.

In final summation, it may be said that this
study has demonstrated that peripheral vision
cues can be a useful aid in making instrument ap-
proaches and recovering from unusual attitudes.

V. Recommendation.

It is recommended that further research be con-
ducted to find means of more fully utilizing the
peripheral vision capabilities of flight crew
members.



PERIPHERAL VISION CUES: THEIR EFFECT ON PILOT PERFORMANCE
DURING INSTRUMENT LANDING APPROACHES AND RECOVERIES
FROM UNUSUAL ATTITUDES

I. Introduction.

A recent study’ showed that peripheral vision
cues displayed in the cockpit of an aircraft
simulator significantly improved pilot perform-
ance while flying high altitude holding patterns.
In considering other operational phases, the
question arises as to whéther such cues would be
useful as an aid in achieving the more precise
control required in making instrument ap-
proaches through a 200-foot cloud ceiling. To
answer this question, a study was conducted in
a jet-engine air transport simulator. Also in-
cluded in the study was a test to determine if
such cues could be used solely for bank angle
control—during instrument approaches—as a
safety “backup” in case of failure of the attitude
indicator (artificial horizon). Also, since severe
turbulence has, on occasion, prevented flight
crews from focusing on their instruments—re-
sulting in loss of control—the pilot-subjects were
tested to determine if they could safely recover
from unusual attitudes with no instrument dis-
play other than the peripheral cue lights.

II. Equipment and Methodology.

Research Device. A Boeing 720 aircraft simu-
lator with two degrees of freedom (pitch and
roll movement capability) was utilized; the in-
strument panel (Figure 1) was typical of that
in many airline aircraft.

Peripheral Cue Lights. Two pairs of small
lights were used as cueing devices; each pair con-
sisted of a red light positioned vertically above
a green one. One pair was installed near each of
the lower corners of the pilot’s control wheel.
(Figure 2). Activated by relays and a switch
card connected to the roll servo of the simulator
computer, the left-hand lights illuminated when
the left wing was down more than 114°, and the

right-hand ones illuminated when the right wing
was banked more than 114° below the horizontal.

Operation of the lights was as follows: during
wings-level flight (between 114° left bank and
114° right bank) the lights did not illuminate;
between 114° and 10° of bank, the green light
on the appropriate side flashed once per second;
from 10° to 22° the green light rate doubled to
two flashes per second. To signify a standard
rate turn, the green light illuminated steadily
in the 4° range between 22° and 26° of bank.
From 26° to 90° the green light was extinguished
and the red light flashed three times per second.
Flash durations, with equal nonillumination
periods between, were approximately as follows:

Green—(1 flash/sec.) =0.50 second.
Green—(2 flashes/sec.) =0.25 second
Red—(3 flashes/sec.) =0.166 second

The bulbs used for the cue lights were G.E.
#327’s using 0,04 amps at 28 volts, D.C., inserted
in Dialco 425-101-3830 transparent colored units
of 0.5-inch diameter. Luminance measurements
of the cue light sources indicated a maximum
of +1.4 log ft.-lamberts for the green bulbs and
+1.7 log ft.-lamberts for the red. See Appendix
for details of cue light circuitry.

Cockpit Illumination. General luminance
within the cockpit was the same for all subjects
but varied by areas ranging from approximately
—0.7 log ft.-lamberts at the instrument panel to
+1.1 log ft.-lamberts at the windshield.

Data Recorded. Two Sanborn 850 recorders
were interconnected to appropriate simulator
circuitry to provide a record of the following
data: airspeed, altitude, roll (bank) angle, mag-
netic (compass) heading, control wheel rotation
(in degrees), control column movement (fore
and aft), path of aircraft relative to glide slope
and localizer “beam,” flash rates and durations of



ACKNOWLEDGMENT

The authors wish to express their appreciation to the personnel of the
Aircraft Flight Simulation Section, AC-959, for their interest and assistance
in keeping the aircraft simulator and its associated equipment and systems
operating in a uniform manner. The authors also wish to thank the pilot
subjects for their interest and cooperation which contributed so much to the
success of this research study.

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.


Glide Slope Performance. The mean percent-
age scores of time flown “above,” “on,” and
“below” glide slope during the nine approaches
are shown in Figure 13, As with the roll angle
data, only information from the last six ap-

BANK ANGLE RELATIONSHIPTMTO
INSTRUMENT/CUE LIGHT DISPLAY MODE

Bank Angie:
100, meee | — s----- More than
90 10°
w ke ee Between
2 70 18 810°
F 60
&
G 50
= 40 SS Between |
2 30 |-- —— wr ale
20 SS Level")
10
°
cy) (8) «© * approaches 4 thru 9

Ficure 12, As expected, time in excess of 10° bank was
greatest when attitude instrument was unavailable
for reference. However, total time in excess of
114° of bank was least in display mode C, indicating
peripheral vision cues were useful in maintaining
“Jevel” flight.

proaches (No. 4 through 9) was used for statisti-
cal analysis of differences between display modes.

The combined mean scores for on glide slope
(maintaining the aireraft close enough to the
centerline of the glide slope to keep the cross
pointer needle within the “bulls-eye” circle on
the instrument) are 25.20%, 13.85%, and 11.55%
for modes A, B, and ©, respectively. The dif-
ferences between A and C, and A and B are
statistically significant (p=<.01); there was no
significant difference between modes B and C.

Similarly, when the scores for within “one-
dot-above,” “on,” and within “one-dot-below”
(ctd+e) are combined, significant differences
again appear between modes A and C (95.45%
vs. 76.15% — p=<.01), and modes A and B
(93.45% vs. 85.95% — p=<.05). As before, no
significant difference was found between modes
B and C. These differences represent a 9.9%
performance decrement for mode B (compared
to A) and 20.2% for mode C. Comparing B
and C! with each other, we find that C was 11.4%
less than mode B. This indicates that use of the
“Vy” command bar with the ‘attitude indicator
resulted in better glide slope performance

MEAN GLIDE SLOPE SCORES

APPROACH
SEQUENCE

INSTRUMENT MEANS

DISPLAY MODE i

POSITION "ABOVE *
“ON" & "BELOW"
GLIDE SLOPE

DS

APPROACH
SEQUENCE

COMBINED
MEANS (%)
(4 thru 9)

APPROACH
SEQUENCE

(0)
1)
ro)
cy
3)
)
(a)

(a)
(b)
te)
(¢)
te)
(f)
(9)

(a)
(b)
te)
(@
)
(ft)

() Ka

—@ 2 DOTS ABOVE GLIDE SLOPE

—e- 2 voTs

LEGEND: -e | 00T ARTIFICIAL HORIZON WITH V ARTIFICIAL HORIZON CUE LIGHTS
com ont . COMMAND BAR (no peripheral WITH CUE LIGHTS. ONLY (no
Te= | DoT BELOW * * cue lights) artificial horizon)

Ficure 18. Mean scores of time flown above,

ment/cue light display modes during nine ILS approaches.
while using the flight director “V” bar (mode A). Surprisingly,

mode © (36.20% versus 44.50% in mode A).

il

‘on, and below glide slope in relation to use of three different instru-

‘As expected, time “on” glide slope was greatest
time spent below glide slope was least in



cue lights. On the other hand, six (30%) of the
20 subjects rolled the airplane in the wrong di-
rection while using the conventional instrument
display without peripheral cue lights. One of
these six maintained the wrong direction of roll
for such an extended period of time he would
have crashed inverted, had he been in an actual
airplane. This is particularly significant when
the experience and skill level of the subjects are
considered.

IV. Summary and Conclusions.

To provide information on the effect of pe-
ripheral vision cues on pilot performance during
instrument flight, 20 ATR pilots flew nine ILS
(instrument) approaches in a Boeing 720 jet
aircraft simulator using three different instru-
ment displays; ie, (1) all instruments* includ-
ing flight director system (“command” bar with
attitude indicator), (2) peripheral vision cue

lights with all instruments*, including attitude
jndicator but without “command” bar, and (3)
peripheral cue lights—as sole source of bank
angle information—with all instruments* eacept
the attitude indicator.

The three principal performance categories
investigated during the ILS approaches were
aircraft deviation from: (1) wings-level flight,
(2) glide slope centerline, and (3) localizer
centerline,

Effects of peripheral cue lights on pilot per-
formance in recovering from steeply banked,
unusual attitudes were also investigated; recov-
eries were made with (1) all instruments* avail-
able (no cue lights), and (2) with peripheral
vision cue lights only.

The performance data obtained during these
recoveries included: (1) time required to recover

*With exception of turn and slip indicator which
was covered during entire study.

Tanz 6. Recovery to a wings-level attitude from 60- and 80-degree left and right banks was accomplished significantly
faster when using only peripheral vision cues. Maneuvers #1 and #4 were to the left with 60° and 80° banks re-
spectively; #2 and #3 were to the right at 80° and 60°, respectively. (All times given in seconds.)

Subject Conventional instruments Total time Peripheral cues only Total time
1* 2* 3* 4a*

1 5.5 10.0 15.5 5.0 6.5 11.5
2. 11.5 15.0 26.5 9.0 10.0 19.0
3. 8.0 12.5 20.5 7.0 9.0 16.0
4. 6.0 5.5 11.5 6.0 11.0 17.0
5. 14.0 11.0 25.0 5.5 12.0 17.5
6. 5.5 9.0 14.5 6.5 5.5 12.0
7 7.5 7.0 14.5 7.0 8.5 15.5
8. 12.5 10.0 22.5 12.0 9.5 21.5
9. 6.0 6.5 12.5 7.0 8.5 15.5
5.0 19.5 24.5 5.5 6.5 12.0
10.0 12.5 22.5 7.0 7.5 14.5
9,5 10.5 20.0 12.0 7.5 19.5
8.5 17.0 25.5 10.0 9.0 19.0
13.0 21.5 34.5 7.5 8.0 15.5
11.0 7.0 18.0 7.0 9.0 16.0
10.5 8.0 18.5 8.0 10.0 18.0
8.0 12.0 20.0 9.0 11.0 20.0
10.0 10.0 20.0 7.5 12.5 20.0
11.0 14.0 25.0 11.5 75 19.0
10.0 11.5 21.5 10.5 8.5 19.0
9.1 11.5 20.6 8.0 8.9 16.9

Standard errors. 0.59 0.94 1,23 0.48 0.41 0. 64

Standard deviations. 2,67 4,24 5.50 2.17 1.84 2.87

*Maneuver sequence number (recovery from unusual attitudes).

14