if a retardant drop was ordered. If so, the tech-
nician would go to the flight operations room
and meet the pilot as he left the briefing. The
technician would then attach with an elastic
strap the stainless steel plate ECG electrodes
across the lateral chest wall, give the pilot a
lubricated rectal thermistor probe and a urine
collection bag. The pilot would then go to the
Men’s Room where he would insert the rectal
probe and make a urine collection after which
the technician and he went to the airplane. The
pilot was then connected to the recording devices
and allowed to depart. The entire instrumenta-
tion procedure required less than three minutes,
maximally.

When tankers were dispatched to operate out
of distant airports closer to the fire, a technician
was flown to that site and remained there until
the pilot was ordered back to Missoula. Data
loss was minimized by this procedure.

Data reduction was carried out over a period
of months after the researchers returned to
Oklahoma City.

Some of the design goals were not met. The
subject-pilots were, at best, reluctant participants
in the study because they were not convinced
that the project was in their best interests. Urine
collections were seldom made according to sched-
ule and there was no way to enforce the collec-
tion schedule. Complete urinary data were
obtained on only two pilots. One pilot refused
to wear the rectal probe, claiming sensitivity;
another claimed to have amebic dysentery. The
monetary inducement was insufficient to make a
pilot delay his takeoff so that. he could be instru-
mented. The pilots readily explained that they
could not afford to compromise a chance for a
second drop by missing being “first off.” Some
in-flight data were thus lost.

III. Results.

About 100 hours of in-flight recordings were
made from subjects 1, 2, 3 and 4 on 130 flights
over 76 fires. Ground observations were made
on subject #5, also.

Taste I—Heart rate by Maneuvers

#1 Resting, 81 bpm

Mean SEM. % of Resting
Start 105.2 4.07 130
‘Taxi 96.9 1.59 120

Runup 107.0 5.22 132

T.O. 110.68 3.38, 137

Enroute 99.25, 6.65 122
Over Fire 99.25, 4,09 122
Drop 119.15 3.83 147
Return 101.2 6.72 125
T.D. 95.91 4.39 119
Taxi 97.08 2.75 120
#2 Resting, 76 bpm

Mean S.E.M. % of Resting
Start 102.96 2.43 136
Taxi 105.74 2.54 139
Runup 110.20 6.40 145
T.O. 112.42 3.46 147
Enroute 99.04 1.40 130
Over Fire 106.36 1,96 139
Drop 122.67 3.76 162
Return 100.68 1.67 133
T.D. 107.15 2.84 141
Taxi 104.89 3.14 138

Tate I (Con't)—Heart rate by Maneuvers

#3 Resting, 90 bpm

Mean S.E.M. % of Resting
Start 101.57 4,52 113
Taxi 95.86 3.62 107
Runup
T.O. 111.58 2.52 124
Enroute 99.63 138 111
Over Fire 113.25 3.01 126
Drop 120,80 4.49 134
Return 108.25, 4.82 120
T.D. 115.80 9.50 129
Taxi 110.25 8.20 122
#4 Resting, 83 bpm

Mean S.E.M. % of Resting
Start 97.79 2.46 118
Taxi 96.56 2.21 117
Runup
T.O. 100.16 2.25 120
Enroute 92.19 1.58 1
Over Fire 100.52 2.65 122
Drop 111.25 2.65 134
Return 91.89 2.00 111
T.D, 99.91 2.92 120
Taxi 93.94 3.55 113

(1) Heart rate: a. Events giving rise to high-
est rates; Invariably, the routine in-flight event
associated with the highest rates with all of the
subjects was the retardant drop over the fire
(Fig. 4, Table I). Two emergencies (hydraulic
line rupture) gave rise to higher rates of 152
(#1) and 158 (#4).

b. Relationship of heart rate to daily flight
hours: The operant hypothesis was that incre-
ments in daily flight hours engendered equivalent
increments in stress and fatigue and that the
latter increments would be reflected in increased



about 90 bpm, the industrial workers about 110
bpm and the lumberjacks about 125 bpm. The
pilots averaged 91, 86, 105 and 104 bpm in flight.
Thus, their work, when based on this one cri-
terion, falls between office workers and industrial
workers.

Andrews? has related heart rate to metabolic
rate in people undergoing physical activities of
various intensities. For arm work, Andrews’
regression line, when applied to these pilots,
shows that the energy expenditure of pilot #1
would be increased by 0.8 kcal/min. or 384 keal/
8 hr.; the energy expenditure of pilot #2 by the
same amount; #3 by 576 keal/8 hr.; and #4 by
769 keal/8 hr. Assuming a baseline metabolic
rate of about 920 keal/8 hr. and a maximum
metabolic rate of about 5500 keal/8 hrs., the total
energy expenditure of pilot #1 would be 1304
keal/8 hr. (24% maximum); 1304 keal/8 hr.
(24% of maximum) for #2; 1496 keal/8 hr.
(27%) for #3; and 1689 keal/8 hr. (31%) for
#4, These values are close to those reported as
allowable for day to day expenditure of energy
for men in good physical condition (25% of
maximum). It is to be re-emphasized, however,
that these figures overestimate the in-flight energy
expenditure of the tanker pilots since the cor-
respondence between heart rate and metabolic
rate was established under conditions of physical
exercise. It must also be remembered that these
pilots seldom flew 8 hours per day.

The heart rate data may be summarized by
stating that the heart rates in flight are generally
those of men engaged in light to moderate physi-
cal work. Certainly, the moderate increases in
heart rate in-flight do not indicate a great degree
of fear or anxiety by these pilots in the execution
of these hazardous missions. Student pilots have
in-flight heart rates that commonly average more
than the maximum rates shown by the tanker

pilots’. It is doubtful that the student pilots
actually do more physical work than the tanker
pilots; the heart rates are a reflection of the great
anxiety of students and the virtual absence of
it in the tanker pilots. The tanker pilots’ voice
transmissions, also, indicated their relaxed atti-
tude by singing, joke telling, etc. en route to
fires. However under conditions of a genuine
emergency, as happened twice when hydraulic
lines broke, the heart rate went as high as any
ordinary pilot’s would under similar circum-
stances. This serves to underscore the pilots’
attitude toward retardant missions which they
apparently view as routine. To the untrained
and unskilled their job may appear almost sui-
cidal, but to them the task is one of which they
have a thorough understanding and mastery.

The urinary data are almost too scanty to be
of value. Many of the values are for single speci-
mens only. The conclusion that all metabolites
are elevated on flight days is probably indicative
only of a slightly greater activity. Tables II &
III and Figure 7 compare the pilots in this study
with themselves, with pilots from other studies
and with control non-flying people. These re-
sults, weakly valid only for #1 and 32, show
that their adrenal activity is increased on flight
days but within the range reported for the normal
population.#:$2°

One great difficulty in drawing conclusions
from the urinary data is that literature values
are not reported in standard units. One investi-
gator may report excretion products on the basis
of 100 mg of creatinine, another as mg per 24
hours, another as wg per kg body weight per
24 hours, and another as yg per milliliter. In
bringing all figures to common units, unavoid-
able errors are introduced in assuming a value
for creatinine excretion or in assuming a body
weight or in multiplying values per hour to ob-

Taste II.—Urinary 17-OHCS Excretion

Aireraft Non-Flight Days
B-29 8.9 mg./24 hrs.
B-52 6.0 mg./24 hrs.
F-104 384 pg/100 mg. creatinine
F-100 & F--104 280 wg/100 mg. creatinine
Normals 1.25-19.95 mg./24 hrs.
Tanker Pilots

1 5.5 mg./24 hrs.

#2 4.1 mg./24 hrs,

#3 12.0 mg./24 hrs,
*H4 7.0 mg./24 hrs.
"HD 14.2 mg./24 hrs.

*Incomplete Data

Flight Days Ref.
15.2 mg./24 hrs. (11)
8.5 mg./24 hrs. (12)
344 pg/100 mg. creatinine (9)
373 & 298 ng/100 mg. creatinine (13)

7.40 mg./24 hrs.
6.50 mg./2+4 hrs.
10.10 mg./24 hrs.



Avg daily in fit. HR

Minutes of fit. 80 30 100 HO 120

96
Subj #! 297
372
378

260
Subj #2 350
363
367
413
469

64
Subj #3 127
146
300
360
4i8

186
Subj #4 225
300
350
360
450
500

Fieure 5, Average daily in-flight heart rate graphed
against the daily accumulated number of minutes of
flight. For each pilot, the average heart rates are

#2 averaged 6.8 hours, with a range of 3.0-9.5;
#3 averaged 6.0, range 4.0-7.0; #4 averaged
7.7, range 4.0-9.0 (Fig. 8). Reported hours of
sleep were examined with reference to the num-
ber of hours flown prior to a given night and
with reference to the hours flown after each
night. The rationale behind this approach was
that if fatigue was present, the pilots should
seek rest and that fatigue should increase in
proportion to the duration of flying. Thus, the
hypothesis was that a greater amount of flying
should be followed by a greater amount of sleep.
There is no apparent relationship between the
hours flown and subsequent amounts of sleep
(Fig. 8). Likewise, there was no apparent rela-
tionship between anticipated flight hours and
duration of sleep (Fig. 8).

IV. Discussion.

This project is similar to many others that
have been underway in this laboratory as well
as at other installations’ * 47 All of these
projects are based on the assumption, probably
valid, that fatigue is accompanied by or causes
a performance decrement**. In fact, most tests
for fatigue involve the measurement of some
function, a decrement in which is referred to as

lower on the days of greatest flight activity than fatigue. Thus, the cause is defined in terms of
on the days of least flight activity. its effect.
% PSYCHOMOTOR PERFORMANCE

pre FLT
mm POST FLT

MINUTES 96 {86 335 367 372 378 399 NO FLY 380 413 469 NO FLT
OF FLT

Subj #1 Subj # 2

Figure
flight and on no-flight days.

A good definition of fatigue is still lacking
because fatigue is a sensation common to many
causative factors. Commonly, one hears differ-
entiations made between “physical” and “mental”

37 55 300 300 300 360 NO FLT

3. Psychomotor performance in percent of the possible score plotted

65 210 300 350.500 NO FLL 63. NO FLT

Subj #3 Subj #4 Subj #5

against the number of minutes of

fatigue. As Bartley** points out, after the per-
son has stated the distinction he feels better for
having said something but he has shed no light
on the problem. .A person may experience just



HEART RATE AVERAGE BY MANEUVER

160 ¢ H/- HYDRAULIC LINE BROKE DO subj #1
r WE subj #2
50 b / HYDRAULIC LINE BROKE Subj # 3
| (3 subj # 4
140 5
130 F
120 +
HOF
100 F E
90 : : a a
CLEAR TAX! OUT RUNUP TO ENROUTE OVEPFIRE DROP RETURN TD TAXI IN

Ficure 4. Heart rate averages for each subject shown by tyne of in-flight activity (maneuver).

For each pilot the

minimum heart rate occurred en route and the maximum occurred at retardant drop.

heart rates. The data were examined to deter-
mine if heart rate changed with the number of
daily flight hours (Fig. 5). The data showed
that the average heart rates were invariably
lower on the days of greatest flight hours than
they were on the days of least. flight hours.

ce. In-flight heart rate compared with resting
heart rate: Heart rates for the entire period of
the study showed increases of (#1), 12%; (2),
13% ; (#3), 17%; and (#4), 25% in-flight over
resting.

(2) Psychomotor performance: In earlier
studies by Fiorica, et al.? it was shown that
physiological parameters changed insignificantly
during 86 hours of sleep deprivation but that
psychomotor performance was a good indicator
of the fatigue brought on by the sleeplessness.
For that reason the “Kugelmaschine” test was
incorporated into this study. Figure 6 shows
that in 82% of the cases post-flight performance
was better than pre-flight performance. In 90%
of the cases the afternoon performance was better
than the morning performance on non-flight
days. In 64% of the cases, post-flight perform-
ance was better than the afternoon non-flight-day
performance.

(3) Urine Chemistry: The original high hopes
for the value of urine chemistry faded when it
was realized that so many urine specimens were
not collected. Values for all four specimens on
flight days and non-flight days were obtained
only on subjects #1 and #2. Meaningful state-
ments thus cannot be made about #8, #4 and
#5 (Fig. 7). Pilot #1 showed an increase in
excretion of all metabolites, except norepine-
phrine in the third specimen which was un-
changed. Pilot #2 showed an increase in
epinephrine excretion on all flight days in all
four specimens; he showed a decrease in norepine-
phrine excretion on flight days, except for the
second specimen which was elevated; an increase
in 17-OH corticosteroid excretion in the first
three specimens on flight days and no change
in #4.

In summary, the urinary excretion of adrenal
medullary and adrenal cortical products was in-
creased on flight days.

(4) Miscellaneous observations: Cockpit tem-
peratures ranged from 63°F on the ramp in the
morning to 125°F over the fires when rectal tem-
perature reached 101°F. Pilot #1 averaged 6.5
hours of sleep per night with a range of 5.0-9.0;



HOURS OF SLEEP

BEFORE FLT AFTER FLT
3.94 5 6 7 8 9 10 4 5 6 7 8 9 10 1
Minutes of Flt. TTT TT rn a | 1-1
96 85
Subj #1 i86 96
297 352
335 367
352 370
367 378
370 399
372 404
378
399
We 45
Subj #2 2249 84
280 229
350 280
363 350
ate 394
382 469
413
469
37 55
Subj #3 55 127
300 360 ——s
300 380
300
360
65 65
Subj #4 186 300
210 350
300 360
300 450
350
360
450
500
63 63 ————
Subj #5 89 149
90

Frever 8. Reported hous of sleep the night before flights plotted against the accumulated num-
ber of minutes of flight eaeh day and the reported hours of sleep plotted against the minutes of
flight on the preceding day.

The heart rates registered in-flight during the — Cauca:
project were also not consistent. on a comparative — offiee work (sedentary), industrial work (inter-
basis, with great physical effort or emotional — mediate), and lumbering (heavy work). The
extremes. Andersen? has plotted heart rates for office workers showed an average heart rate of

n men representing three professions—



AM 68-26

PHYSIOLOGICAL STUDIES ON AIR TANKER PILOTS
FLYING FOREST FIRE RETARDANT MISSIONS

C. E. Melton
Marlene Wicks
J. T. Saldivar, Jr.
Jack Morgan
Florence P. Vance

Approved by Released by

eo
Kha tte [USge€ wb
P. V. Smcen, M.D.

J. R. Drie, M.D.
Cuter, Crvi, AEROMEDICAL Feperat Arr Surcron
InstTITUTE

October 1968

Department of Transportation

FEDERAL AVIATION ADMINISTRATION

Office of Aviation Medicine
24848


project that these same pilots continue their work
year after year. Activities that are now insig-
nificant in terms of a compromise with safety
may in later years become significant.

While the accident potential would seem to be
high in this flight activity, the safety record
is impressive. It is reported that there have
been only 26 accidents and incidents for all

agencies in over 50,000 flying hours in the years
1961-1967, for a rate of about one accident or
incident per 2000 hours. These figures include
mechanical failures as well as pilot errors. Fig-
ures are not available that would give an esti-
mate of how many accidents are believed to be
fatigue-related.

REFERENCES

am"

. ALTMAN, Puiuip R. and D. 8. Drrrmer. Biology
Data Book. USAF AMRL-TR-64-100, 1964.

2, ANDERSEN, K. L, “Work Capacity of Selected Popu-
lations” Ch. 4 of The Biology of Human Adapta-
bility, Paul T. Baker and J. S. Weiner, Clarendon
Press, Oxford, 1966.

. ANDREWS, R, B. “Estimation of Values of Energy
Expenditure Rate from Observed Values of Heart

Rate.” Human Factors 9: 581-586, 1967.

| Batxe, B. C, E. MELToN, Je, and C. Brake.

“Physiological Stress and Fatigue in Aerial Missions

for the Control of Forest Fires.” Aerosp. Med. 37:

221-227, 1966.

Barttry, S. H. Fatigue, Mechanism and Manage-

ment, Charles C. Thomas, Springfield, Ill., 1965.

. Bartiey, S. H., and Erorse Cxute. Fatigue and Im-
pairment in Man, McGraw-Hill, New York and
London, 1947.

. Frorica, Vincent, E. A, Hiccrns, P. F. IaMPIerro,
M. T. Latecona, and A, W. Davis. “Physiological
Responses of Men During Sleep Deprivation.” Jour-
nal of Applied Physiology 24: 167-176, 1968.

8. Fox, H. M., B. J. Murawsk, A. F. BartHotomay,

and S. Grrrorp, “Adrenal Steroid Excretion Pat-

terns in Eighteen Healthy Subjects.” Psychosom.

Med, 23: 31-40, 1961.

e

2

a

10

9. Hare, H. B, J. ©. Durry, J. P. Exzis, and E. W.
Witiams, “Flying Stress in Relation to Flying Pro-
ficiency.” Aerosp. Med. 36: 112-116, 1965.

Lone, C, Biochemist’s Handbook. D. Van Nostrand
and Company, Inc., Princeton, N.J., 1961.
Marcupanxs, V. H. “Effect of Flying Stress on
Urinary 17-Hydroxycorticosteroid Levels.” J. Aviat.
Med. 29: 676-682, 1958.

-...“Flying Stress and Urinary 17-Hy-
droxycorticosteroid Levels During Twenty-Hour Mis-
sions.” Aerosp. Med. 81: 639-643, 1960.

. Marcrpanks, V. H., H. B, Harz, and J. P. Ets,
“Stress Responses of Pilots Flying 6-Hour Missions
in F-100 and F-104 Aircraft.” Aerosp. Med. 34:
15-18, 1963,

“Medical Aspects of Aircraft Pilot Fatigue with
Special Reference to the Commercial Jet Pilot.”
Aerosp. Med. 87: Sec. IT: 1-44, 1966.

Mexron, C. E., and M, Wicks. “In-Flight Phys-
iological Monitoring of Student Pilots.” OAM Re-
port AM 67-15, 1967.

Murpny, T. M. and W. A. Youne.
tion In Aircraft Pilots.”
1968,

Rowan, J., H. Oxper, and W. L. Jonzs, Jn. “Flight
Research Program : VII. Medical Monitoring of Navy
Carrier Pilots in Combat.” Aerosp. Med. 38: 133-
139, 1966,

10.

i.

ot

ia

1.

16. “Hyperventila-

Aerosp. Med. 39: 463-466,

17.



tain 24 hour excretion figures. The urine values
from the tanker pilots must be cautiously inter-
preted since the data are too scanty to permit
statistical treatment that might reveal the sig-
nificance of flight day vs. non-flight day dif-
ferences,

‘Taste III—Urinary Catecholamine Excretion

pe2/100 mg. Creatinine
Epi

Tanker Pilots Nor Epi

No Fit Fit ‘No Fit Ref.
#1 2.06 0.86 7.08 3.95
#2 1.96 0.86 4,12 5.70
#3 1.46 11g* 8.52 5.19
#4 1.01 119 31 6.84
#5 1.59 2.75 2.30 4.87*
F-100 & F-104 Pilots
1.28- 0.25 357-123 (13)
1.82
Non-Flying
Civilians 0.006 1.49 (1, 10)

*Incomplete Data

Heart rate patterns show much the same things
that have been shown in other studies. Events
that are associated with highest heart rate are
low altitude, low airspeed maneuvers; in this
case, the retardant drop is associated with maxi-
mum heart rates, emergencies excepted. Student
pilots show maximum heart rates during short
field landings. Navy carrier combat pilots
show maximum heart rates at launch and re-
covery, being lower than those during actual
combat bombing runs". Pulmonary ventilation
in light plane pilots increases during takeoff and
landing**, With the tanker pilots it is probable
that physical work controlling the heavy TB-M
at low airspeeds and the heat. over the fire also
contribute to the increased heart rate during
drops.

The post-flight improvement in psychomotor
performance deserves some comment. Insofar as
this measurement is indicative of fatigue in
other circumstances, one would conclude that the
tanker pilots were not fatigued sufficiently to
cause a decrement in psychomotor performance.
Since performance improved in the afternoon of
non-flight days, one cannot ascribe the improve-
ment to flight itself. All that can be said is
that flight does not prevent the improvement.

The pilots seldom complained of fatigue post-
flight nor did they admit to it on query. Pre-
flight questionnaires in the mornings revealed an
occasional admission of fatigue ascribed to the
previous night’s social activities and lack of

sleep. The amount of sleep that they sought,
however, did not appear to be related to the
number of hours of flying that day.

Systolic blood pressure decreased 53% of the
time post-flight. On non-flight days the systolic
blood pressure decreased 40% of the time in the
afternoon.

The general evaluation of these pilots based
on the data, observation and interview is that
they do not appear to be fatigued by their oc-
cupation, This is borne out by estimates of
energy expenditure and by their psychomotor per-
formance. Their urinary output of steroids and
catecholamines is consistent with a mild stress.
This latter statement should not be taken to
mean stress in excess of a normal “rate of living,”
for their values are within the normal range.

Bartley®* views fatigue as a sensation rather
than a metabolic entity. Common to all causa-
tions of fatigue is some form of conflict. Con-
flict occurs when any contradictory conditions or
negative motivations exist, including pain, bore-
dom, physical exertion, anxiety or frustration.

The tanker pilots comprise a rather unique
group, distinctly different from military or air-
line pilots primarily on the basis of the method
of their payment. No system could be devised
that would inspire stronger positive motivation
to fly than the per flight hour method of pay-
ment coupled with the short season within which
much of their yearly income must be earned.
Thus conflict exists for these pilots when no
flight task exists rather than when one does
exist. This outlook is underscored by their
eagerness to be first off in order that they may
get to make an additional drop and by their
rather ambivalent attitude toward forest fires.
They, as citizens, are concerned about the de-
struction of forests but as professional tanker
pilots they cannot help but hope for thunder-
storms.

On the basis of this study and recognizing
that there are unmeasurable factors involved, it
can only be said that there is no indication
for reduction of allowable flight hours of these
pilots. Questions may be logically raised about
off-duty activities contributing to fatigue, the
quality of the aircraft, the presence of carbon
monoxide in the cockpit and the willingness of
the pilots to wear oxygen masks, and the effect
of all factors on these pilots as they get older.
It is the impression of the researchers on this


y
w Zz
Z é
F
é &
@ 4.500 2
5 &
& 3.500 i
uw So
8
2.800
1.300
0.500
0.000,
She
Subj # | 2 3 4 5

1.800

 FUr pay
mmm NO FLT vay

1,600

1.200

1,000

0.800

0.600

0.400

0.200

0.000

Fieure 7. Urinary excretion of adrenal products in yg/br. for catecholamines and in mg/hr. for steroids for

each subject.

as intense a sensation of fatigue from dealing
with problems from behind a desk as from deal-
ing with problems from behind a lawnmower.
The paradox is that the sum of the efforts, desk
and lawnmower, may not produce twice the
amount of fatigue.

Stress is likewise elusive of good definition
and is usually described in terms of the stressor
such as cold, heat, injury, ete. Again, differen-
tiations are made between physical and emotional
causes. The responses to stress are well recog-
nized and all, at least initially, involve an in-
creased output of adrenal medullary and adrenal
cortical hormones.

Thus, the terms “stress” and “fatigue” have
the common property of vagueness. However,
intuitively they seem to be related in that a
continued stress gives rise to fatigue. That as-
sumption also underlies this project as well as
the ones mentioned above.

The design of this project was such that indi-
vidual “little stresses” would be identified by
heart rate increases. This measurement is prob-
ably the best that is currently available when all
factors are considered. It is easily obtained and
recorded; the recording of it interferes min-
imally with the subject and it correlates well
with other measurements such as galvanic skin
response, pupillary response and pulmonary
ventilation.” Balke, et al. used heart rate as
an index of energy expenditure The assump-
tion in that case was that the observed increases
in heart rate reflected the same increase in meta-

bolic rate as did increases in heart rate caused
by exercise. This assumption is probably not
valid precisely, but the error would lead to an
over-estimation of energy expenditure by the
pilot and is thus a safe assumption. Since this
over-estimation failed to indicate an accumula-
tion of fatigue, then the valid conclusion could
be reached that the allowable flight hours of the
pilots in that study did not need to be reduced.
Applying the same criteria to the heart rates
obtained in this study, the conclusion would be
the same; ie, metabolic rates would only be
elevated 12-25% over the resting rate. All of
these pilots were lean men in apparently good,
and certainly in average, physical condition.
They should have been able to perform at a rate
of 25% of their maximum capacity for aerobic
work without incurring fatigue that would not
have been reversed in 16 hours off duty. Ap-
plying the criteria of Balke, these pilots should
have been able to add 1250 keal of energy ex-
penditure to their resting metabolic rates within
eight hours. If a baseline (but not basal) meta-
bolic rate of 115 keal/hr is assumed for these
men, then simple calculations, based on their in-
flight heart rate increments, show that their total
energy expenditure during 8 hours of flying
would range from 1030 to 1150 kcal. In short,
their flight activities probably called for less
expenditure of energy than almost any other
non-flying activity. It must be kept in mind,
however, that these pilots did not often sleep
eight hours and their off duty energy expenditure
must be added to that expended in flight.



Fievre 1. TB-M (Pilot #4) leaving the slurry pit for a
retardant mission.

Ficure 2.
tating cylinder, bored to receive steel balls of five

“Kugelmaschine.” Device consists of a ro-
different sizes, Balls are placed in holes in the steel
cover over the cylinder, as shown, When the hole
in the cylinder is aligned with the hole in the cover,
the ball will drop, activating a switch and reg-
istering a hit. If the hole passes empty or if the
wrong sized ball is placed in the hole, a miss is reg-
istered. The cylinder rotates at different speeds
that are pre-programmed. Scores are expressed as
a percent of the possible score.

resting specimen upon arising, a pre-flight speci-
men, an in-flight or during-flight specimen, and
a post-flight specimen. The collected samples
were analyzed for epinephrine, norepinephrine,
17-OH corticosteroid and creatinine.

The rationale behind the selection of these
measurements was that heart rate would serve
as an instantaneous indicator of stressful events
while urinary excretion of catecholamines and
17-OH steroids would indicate the longer term
or total effects of stress. Voice transmissions
were used to identify the various episodes during
a mission. Rectal and cockpit temperatures were
used to evaluate one parameter believed to con-
tribute to the overall job stress. Psychomotor
performance was selected as an indicator of fa-
tigue, since it had been shown to be the most
sensitive measurement in this regard in earlier
studies’, Other measures would have been de-
sirable but were not feasible or possible, such as
determination of turbulence, quality of job per-
formance, galvanic skin response, in-flight blood
pressure and pulmonary ventilation.

In-flight measurements were recorded on two
Lockheed 411-C four track instrumentation tape
recorders. The recorders, associated amplifiers

and sensors were mounted in the two lead tankers
at the slurry pit each night in anticipation of
flight the next morning (Fig. 3).

Figure 3, Lockheed 411-C four track tape recorder in
position in TB-M rear cockpit. A 10 hour NiCad
battery for operation of the recorder is shown upper-
most in the picture. Recordings were made at 3%
ips.

The pilots were instructed to come to the
trailer-laboratory each morning when they re-
ported for work. At that time they were to
submit their first urine specimen and undergo
pre-flight testing. When a fire call came in, the
technical personnel at the trailer were informed


PHYSIOLOGICAL STUDIES ON AIR TANKER PILOTS FLYING
FOREST FIRE RETARDANT MISSIONS

I. Introduction.

The causes of forest. fires are many and varied,
including sparks from trains, airplane crashes,
campfires and unextinguished cigarettes. How-
ever, most forest fires are caused by lightning
strikes when thunderstorms pass over the great
coniferous forests. Since these storms are ran-
domly distributed geographically, probability
factors dictate that most of the fires will be in
remote areas where they cannot be readily reached
with surface vehicles.

Attacks on fires in remote or wilderness areas
are primarily by aerial means. Men and equip-
ment are dropped by parachute near the fire to
attack it from the ground and retardant solutions
(thick, brick-red ammonium phosphate solutions
called “slurry”) are dropped from air tankers
on or near the fire to reduce it and retard its
spread.

In order for the retardant to be placed effec-
tively on the fire, the air tankers must be flown
at approach speed at tree-top altitude while
loaded to near maximum gross weight. Fires
are commonly located in canyons that are filled
with smoke. Turbulence over the fires is said
to range from moderate to severe. These condi-
tions are considered to create a high potential
for accidents, The risk is considered to increase
in proportion to the length of time that these
factors impinge upon the pilot and cause fatigue
to develop.

In recognition of these stressors, the U.S.
Forest Service has set empirical limits for flight
duty. These limitations provide that a pilot
may not fly more than 8 hours in any one day
if no more than 4 hours were flown the previous
day. No more than 6 hours may be flown in any
one day if the preceding day’s flight time ex-
ceeded 4 hours. No more than 38 hours of flight
time may be accumulated in any 6 day period.

Pilots are required to have 1 day of rest if 26
hours or more were flown in the previous 6 days.
No pilot is allowed to fly more than 6 hours with-
out a 1 hour rest period, exclusive of ground
duties related to flight.

This study represents an attempt to test ob-
jectively the validity of those regulations.

In the summer of 1964 a project was designed
to evaluate stress and fatigue in pilots flying
forest fire control missions. That project was
carried out in July and August of that year with
Forest Service pilots and FAA pilots serving as
subjects. The conclusion drawn from data col-
lected during simulated missions was that the
fatigue incurred by the pilots flying 8 hours per
day was not cumulative over a period of 3 days
and that no alteration of flight hour limitations
was necessary*. Because there were few fires
calling for air tanker operations in 1964, a plan
was tentatively made to return for further studies
under actual fire conditions. The project de-
scribed here was carried out in August 1967, in
conjunction with the Missoula Equipment De-
velopment Center, U.S. Forest Service, at the
Aerial Fire Depot, Missoula, Montana.

Il. Methods.

Five TB-M (Fig. 1) air tanker pilots were
subjects in the experiment. These pilots were
contract pilots and were induced to participate
in the project by offering them a bonus of
$5/flight hour and $10/day.

Necessarily, this was a project of opportunity
so that no pre-set design specifying degrees of
freedom was possible. The in-flight parameters
selected were (1) heart rate, (2) rectal tempera-
ture, (8) cockpit temperature and (4) voice
transmissions. Ground studies included pre- and
post-flight, (1) a questionnaire, (2) blood pres-
sure, and (3) psychomotor performance (Fig. 2).
Urine collections were planned to provide for a



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