cormetiots

fd ek cnmranes
> @. 2220

Bene Herero)

249 race *

The illustration above shows the complex coordinator and decision task device, used at the Civil Aeromedical
Research Institute in pilot-fatigue studies. The device is placed in altitude and environmental chambers for the
assessment of the effects of these factors and also measures performance decrements resulting from various schedule “
regimens, sleep losses, and other circumstances. It has been transported to various locations for field studies.

12


rules and procedures, interrupted family life,
family medical and social problems, personality
clashes with coworkers and supervisors, nature
of punishment for omissions and commissions,
monotonous and boring circumstances, and minor
discommoding afflctions (pruritis ani, refractive
error in spectacles, periodontal neuralgia, certain
allergies, etc.).

III. Flight-Time Limitations.

To refresh our minds concerning the specific
wording of Part 40.320 of Title 14 of the Code
of Federal Regulations, we note that it states :°”

(a) An air carrier shall not schedule any
flight crew member for duty aloft in scheduled
air transportation or in other commercial flying
if his total flight time in all commercial flying
will exceed the following flight time limita-
tions :

(1) 1,000 hours in any year,
(2) 100 hours in any month,
(3) 80 hours in any seven consecutive days.

(>) An air carrier shall not schedule any
flight crew member for duty aloft for more
than 8 hours during any 24 consecutive hours,
unless he is given an intervening rest period at
or before the termination of 8 scheduled hours
of duty aloft. Such rest period shall equal twice
the number of hours of duty aloft since the
last preceding rest period, and in no case shall
the rest period be less than 8 hours.

(c) When a flight crew member has been on
duty aloft in excess of 8 hours in any 24 con-
secutive hours he shall, upon completion of
his assigned flight or series of flights, be given
at least 16 hours for rest before being assigned
any further duty with the air carrier.

(a) Time involved in transportation, not local
in character, required of a flight crew member
by an air carrier and provided by the air carrier
for the purpose of transporting the flight crew
member to an airport at which he is required
to serve on a flight as a crew member, or from
the airport at which he was relieved from duty
as a crew member to return to his home sta-
tion, shall not be considered as part of any re-
quired rest period,

(e) Each flight crew member engaged in
scheduled air transportation shall be relieved
from all duty with the air carrier for at least
24 consecutive hours during any seven consecu-
tive days.

(f) No flight erew member shall be assigned
any duty with an air carrier during any rest
period preseribed by this part.

(g) A flight crew member shall not be con-
sidered to be scheduled for duty in excess of
prescribed limitations, if the flights to which
he is assigned are scheduled and normally ter-
minate within such limitations, but due to ex-

as adverse weather conditions, are not at the
igencies beyond the air carrier’s control, such
time of departure expected to reach their des-
tination within the scheduled time.

These duty and flight-time limitations are con-
cerned with scheduled air-carrier interstate oper-
ations within the continental U.S. Part 41 gov-
erns flight-time limitations with reference to such
operations concerning flights involving points
outside of the U.S., and Part 42 covers limita-
tions in supplemental air carriers, cargo-only
operations ,and other special activities.

Since 1931, when Wiley Post discovered that
cutting through time-zones resulted in certain
body functions becoming asynchronous with the
celestial and social periodicity characterizing the
destination, it has become increasingly apparent
that “circadian (circa for about,and dian for
dies—a day) periodicity” is a contributor to “air-
travel fatigue.” ® Individuals vary in their
initial susceptibility to this phenomenon and also
in their length of time to “fall in step” with the
destination period subsequent to arrival. Certain
recent CARI findings in this respect will be de-
scribed later in this paper.

In Great Britain, civil jet-aircrew task-loading
factors that contribute to fatigue have been an-
alyzed by Dr. H. P. Ruffell Smith, and cockpit
environmental factors have been assessed by Dr.
A. J. Barwood. ® In France, Dr. Gerard Juin
has been concerned with jet-pilot fatigue and has
published extensively.*®

In the U.S., Dr. James Crane has been investi-
gating medical leads to what have appeared to be .
contributing factors in jet-pilot fatigue.» *
Also, Dr. Spealman of the CAA investigated pos-
sible environmental factors in certain cases of
task fatigue in jet-flight engineers.

The 1960 paper by Captain A. D. Reedy of Pan
American World Airways borders on being a
classic in the aviation-fatigue literature.** Prior
to that, the 1946 compendium by Viteles, Brim-
hall, et al, of the aviation fatigue literature,
stands as a landmark.

More than 100 years ago, fatigue in lighter-
than-air activities was a well-known phenom-
enon.* In 1914, a top pilot of the day published
for physicians information bearing on certain
in-flight environmental phenomena that predis-
pose to fatigue.* In 1918, the U.S. Army Air
Service Medical Research Laboratory at Mineola
(the predecessor of todays School of Aerospace



VII. Selected Comments.

Steady but slow progress is being made in
gaining control of the fatigue matter on various
fronts. Assisting to alleviate the problem are
several occurrences that have materialized inde-
pendently of direct efforts to mitigate fatigue.
For example, since 1959 many airport runways
have been lengthened, fan jets have been intro-
duced, certain types of air-traffic assistance have
markedly improved, and runway lighting systems
have been augmented, all of these developments
helping to ease the stress of the jet-pilot’s
occupation.

Also, in a number of locations, the “parkway
syndrome” has diminished as a factor relative to
its 1959-60 significance. Additionally, the jet
pilots, as a group, have now become so familiar
with the operational characteristics of the jets,
and have become so intimately acquainted with
their craft, that any earlier existing “fatigue of
transition” has essentially vanished. Another con-
sideration is that the earlier “bugs” that plagued
the newly introduced jets, notably hydraulic fail-
ures, have apparently been pretty well eliminated,
again helping to diminish the overall number
of occupational stresses to which jet pilots are
subjected.

Interestingly, certain of the newer jets have
such improved handling characteristics and oper-
ational features that trips are concluded with
less physical and mental demands on the pilots
than was the case with other craft.

Recently, a longtime airline Captain in his
early fifties, with thousands of piston flying
hours, who now makes the run between Dallas
and Miami in the new Boeing 727, told the author
that the 727 is considerably less demanding and
fatiguing to him than the older piston craft. The
short-field characteristics of the 727, its simplified
cockpit displays and pilot tasks, and its ease of
landing, coupled with other factors such as the
virtually vibration-free cabin, are undoubtedly
factors producing the Captain’s experience. Ac-
tually, to project into the future for a moment,
there is no reason why the same “antifatigue”
qualities cannot be obtained in the evolving super-
sonic transport (SST), a consideration that will
weigh in such questions as the retention of older
pilots for SST’s, the nature of SST scheduling
practices, etc.’*

Various types of air transports differ in their
“fatigue-promoting” qualities, as was pointed out

by Mr. Jerome Lederer in the 1930’s, who noted
that the new-style all-metal aircraft (Boeing
247’s, DC-2’s, and Northrops), had “less vibration
and infinitely more comfort than previous air-
planes (except the Curtiss Condors).” ® The in-
stallation of autopilots did much to relieve the
fatigue of pilots, and the use of flight-stability
augmentation and automatic throttles on future
craft such as the SST should have similar bene-
ficial consequences.

Mr. Lederer’s observations were made at a time
when “biological engineering” was coming into
being and, bit by bit, began to find its way into
the features of production-line aircraft and as-
sociated equipment.”

One could scarcely locate a manufacturer today
who does not, to ene degree or another, incor-
porate biological or “human-engineering” data in
his designs.“ ‘* 7° Much remains to be accom-
plished, however. For example, the comfort of
certain jet-pilot oxygen masks, as reported by
many pilots, can stand improvement. The de-
velopment of skeletal dimension data on today’s
air-transport pilots so that design engineers can
tailor the cockpits, seats, and associated apparatus
to the present pilot population would be valuable.

Various populations are “selected” and are not
representative of the general public. Air-trans-
port pilots are physically superior as a group,
with good executive health programs and fre-
quent physical exams, and cannot be character-
ized by physical anthropological data obtained
from the general population or from studies
conducted years ago. CARI anthropologists have
obtained data on air-traffic terminal and enroute
controllers that is finding its way into improv-
ing the environmental circumstances of the con-
troller, enabling him to accomplish his duties
under more convenient circumstances.

The same can be accomplished with today’s
air-transport pilots, and CARI is working with
ALPA with respect to obtaining the data for
the design engineers. A useful application will
be in restraint-system design, since there exists
today certain combinations of shoulder harnesses
and seats that, if the pilots wore the harnesses
during takeoff and landing, would, by virtue of
undue body-motion restrictions with respect to
certain controls, create a greater hazard with
reference to potentiating possible accidents than
the safety protection afforded by wearing the
harnesses. Anthropological data, placed in the


result in the manifestation of these advanced

psychosomatic signs of protracted fatigue and /
stress. It should also be noted that among the
persons who are most susceptible to developing the
conditions noted above are persons who appary/
ently “internalize” their emotions and thus pro-
duce prolonged internal gastrointestinal, cardio-
vascular, and biochemical rearrangements that
turn into disease. Not infrequently, these indi-
viduals appear outwardly calm and placid while
on the job (perhaps even while at home).

Parenthetically, we should be aware that the
prevalence (percentage of cases) of these diseases. *
found among airline pilots at a given time may
not be helpful to us in our analysis, since, should
an individual develop a condition that progresses
to an advanced degree, the chances are he will not
continue in the pilot population, and a spuriously
low percentage will be found. The “incidence”
is, therefore, the key point of interest. The in-
cidence of a condition is defined as the number
of new cases of the given condition arising within
a given period of time in a given population.
Incidence is, therefore, a rate quantity and is of
primiary interest to us with respect to the fatigue
question in a given situation.

As a point of consideration, the indications
are that relatively short-term physical and men-
tal fatigue is not “cumulative,” if adequate
rest and recreation follow the activity yielding
the fatigue. Thus, repeated bouts with fatigue, vA
do not produce certain irreversible changes that
accumulate over a period of time (as is the
case with repeated bouts with ionizing radia-
tion), and proper postfatigue activity or inac-
tivity can, insofar as modern medical techniques
allow us to ascertain, result in complete “biologi-
cal erasure” of the fatigued state.

Of course, the apparent “price” charged by
nature in return for the privilege of living is the
gradual development of a “loss of vitality”
(termed by some the “force of mortality”), and
as the years pass by, living tissue gradually loses
its ability to “bounce back” rapidly after a bout
with fatigue through the life-long ultimately ir-
reversible process of senescence.** It is well-
documented, however, that those who frequently
subject their body to certain kinds of fatigue-
yielding activities develop a “resistance” to fa-
tigue through physical and mental conditioning
and may, in fact, live longer than otherwise
would have been the case.”* Actual lowering of

the “physiological age” of individuals has been
accomplished through graded, properly applied,
conditioning programs.*

Lack of adequate physical activity (to the
point of yielding fatigue) has been recorded as
producing insomnia, loss of skeletal- and heart-
muscle mass and work efficiency, loss of capillary-
bed mass and efficiency, loss of skeletal calcium,
and obesity.”® Once these conditions begin to
advance in degree, they tend to further discour-
age the host from undertaking increased physical
activity, since, when he does so, the results are
general discomfort, breathlessness, and other un-
pleasant sensations. The consequence is a vicious
cycle known as the “white-collar workers’ and
executives’ decline.”

Since no serious person would dismiss poten:/
tially detrimental consequences of fatigue to avi-
ation, continuing studies of fatigue are being con-
ducted. Times change, equipment changes, and
responsible monitoring of altered conditions in
relation to fatiguing factors is a “communal”
requirement of those engaged in aviation.

Where fatigue may jeopardize safe operations,
remedial action is'mandatory. The FAA, rec-
ognizing this, has issued a Notice of Proposed
Rule Making with respect to the possibility of »
adjusting the existing regulations relative to air-|
carrier-crew flight-time limitations in keeping
with technological and operational alterations
that have occurred in air transportation.‘ 4 \
Constructive comments and suggestions have been
received from a number of quarters, and are un-
dergoing evaluation.

V. New Developments—Intercontinental
Flights.

Recent findings by Drs. Hauty and Adams of
the Civil Aeromedical Research Institute are
showing increasing promise relative to mitigation
of fatigue problems. Their study, an example
of the fruit that can be harvested through inter-
disciplinary research (in this instance, collabora-
tion between psychologists and physiologists),
involves an investigation of interrelationships
between biochemical, physiological, and psycho-
logical factors before, during, and after a flight
from the U.S. to Japan. Following a period in
Japan, the same parameters were measured with
respect to the consequences of the return trip
to the U.S. A scientific partner in this study is



Medicine at Brooks Air Force Base) published
certain factors concerned with fatigue. A year
later, the Air Service Medical contained infor-
mation on fatigue, and in the 1920’s, Lindbergh
became acquainted at first hand with its detri-
mental effects on flight proficiency. °°

In the 1930’s, Amelia Earhart described factors
in cockpit design that foster the onset of fa-
tigue.** In the same decade, Dr. Armstrong
called attention in his textbook to fatigue, and
in the 1940’s, Dr Bauer and Dr Kafka discussed
it in their respective aviation-medicine texts." %

In recent years, Lavnikov of the U.S.S.R. has
commented on aspects of pilot fatigue.’ Also,
the January 31, 1964, report by Captain Richard
Beck of Trans World Airlines presents a credita-
ble summary of present information relative to
jet-crew fatigue.*

An excellent report by the Australians Cam-
eron and Cumming describes the fatiguing effects
of certain cabin environmental factors.*

IV. Indicators of Excessive Fatigue.

The first indication of excessive fatigue in an
occupation may appear as what may be termed
_/ psychosomatic symptoms. These can include:
headaches, burning eyes, sweating, heartburn,
chronic constipation or chronically loose bowels,
chronic loss of appetite, nightmares, and short-
ness of breath.

In advanced stages, the symptoms would show
as periodic job absenteeism, since they would
have progressed to the point of illness, best
treated by rest. In one study of jet-pilot absen-
teeism in a major airline, no increase in absen-
teeism on the part of pilots was found, appar-
ently indicating that, in general, and with re-
spect to this airline, any fatigue that is present
has not progressed to this point of impact on
the pilots’ work experience.®*

hs Another indication of excessive fatigue is per-
formance decrement. In this case the picture is
clouded somewhat, since pilots and other crew
members can exhibit an “end spurt,” which,
coming at the end of a long period of flying,
can temporarily erase the effects of fatigue that
accumulated during the trip. ** This study,
by Dr. David Simons and his colleagues at the
School of Aerospace Medicine, is quite revealing
with respect to the complex nature of the fatigue
question. It should be pointed out, however, that,
although an end spurt may temporarily erase

subjective fatigue effects, the period of rest that
follows is essential to full recovery from the fa-
tigue. Also, if the number of end spurts re-
quired of a scheduled civil air craw attains a
certain frequency, full recovery following each
individual incident may not be achieved, result-
ing in a gradual “cumulative fatigue state,”
which is known colloquially as being gradually
“beat down” over a period of time.

Performance decrement due to fatigue may be
manifested as “sloppy flying” by a pilot who
previously was more meticulous. His own ac-
ceptable margins for precision and accuracy be-
come wider.* Ultimately, he may be involved
in a number of minor incidents or a major ca-
tastrophe. It may be that the fatigue state led
him to make an error (the number of errors in-
creases with fatigue, especially errors made un-
der adverse weather or other circumstances) or
to fail to respond rapidly and properly in an
emergency situation.

There are ways in which these performance
decrements can be measured, but great care must
be taken in interpreting the measurements and
in ascribing a “cause” to an “effect.”

_- A final medical indicator of long-term ex-

posure to fatigue (and stress) is felt by public-
health authorities to be the development of clin-
ical illnesses, such as essential hypertension, pep-
tic ulcer, migrane headache, certain skin rashes,
and certain other conditions. Of course, not all
persons having these conditions necessarily ob-
tained them from stressful occupations. There
does, however, seem to be a connection in a sub-
stantial number of cases. Do certain airline
pilots (for example, jet pilots on East-West
runs) have a higher incidence (number of new
cases per unit time) of these conditions than they
would in the absence of circumstances suspected
of producing excessive fatigue? For example, -
the incidence of these conditions can be deter-
mined in piston pilots on North-South runs,
matched for age and other factors with the above
mentioned jet pilots. Also, how do jet: pilots
compare with piston pilots, all other factors
equal except for the nature of the aircraft and
related operational aspects?

It should be noted that only now has the ex-
posure to jets been sufficiently long to begin to

* Precision is how closely several maneuvers (or tasks) exe-
cuted by a given pilot match with each other. Accuracy is how
closely a given maneuver (or task) matches with the “ideal”
standard aimed for by the pilot.


extent) during the first day in Tokyo, and to a
lesser extent, during the first day of return to
Oklahoma.

This data, the first ever collected in the civilian-
aviation context with respect to human biological
time/time-zone interrelationships, performance
alterations through the associated fatigue, and
trip-recovery times, will be amplified through the
findings of subsequent studies. An example is a
recent study, also accomplished by Drs. Hauty,
Adams and Charles Crane (a CARI biochemist),
which is concerned with another group of sub-
jects transported to the Philippines. The investi-
gators will report their data in subsequent
months, which include information obtained with
a newly developed “evaporative water loss” de-
vice designed and constructed by Dr. Adams to
measure the water loss through the skin (a proc-
ess intimately associated with skin blood-vessel
tonus, this latter condition reflecting in large
measure—environmental factors accounted for—
upon the state of “nervous tension”).

VI. New Developments—Forest Service
Flights.

Another recent interdisciplinary CARI study,
conducted by Drs. Balke and Melton (a medical
doctor and a neurophysiologist), with the assist-
ance of Dr. O’Connor (a psychologist), and
other CARI investigators (including CARI’s
flight-research pilots Messrs. Hasbrook and Burn-
worth), in cooperation with U.S. Forest Service
Personnel of the Department of Agriculture, in-
volves the use of inflight telemetry techniques as
developed at CARI. Certain biomedical data is
telemetered during flight from the pilots being
studied and recorded on tape in receivers carried
by an accompanying aircraft. The studies are
being made in Montana on Forest Service fire-
fighter pilots, using single- and multi-engine air-
craft. The pilots are at times subjected to long
periods of demanding flight tasks, with the de-
velopment of varying degrees of fatigue. Cor-
relation of the various biomedical factors during
specific portions of the flight task are made pos-
sible by CARI’s biomedical telemetry techniques.

As a side dividend, since this type of “borate-
bomber” aerial-applicator work does not involve
the organophosphate and highly toxic substances
often utilized in crop-control activities, the find-
ings will help us separate out the effects of
fatigue per se generated by stress-flight perform-

ance from the combined picture of fatigue effects
plus toxic factors seen in crop control.

Inflight stresses and the resulting fatigue were
measured in Forst Service pilots recently near
Missoula, Montana. Prescribed missions were
flown continuously for 8 hours (with short refuel-
ing breaks), involving low-altitude “canyon runs”
that require a high degree of vigilance and flight
proficiency on the part of the pilot. Among the
aircraft used was CARI’s custom-equipped Beech-
craft T-34B Mentor.

The telemetered information was picked up by
a flying receiver-platform (a specially modified
Beechcraft Twin-Bonanza with special receivers
and tape-recording equipment), and by CARI’s
portable ground-telemetry equipment contained in
a specially designed van.

Included in the preflight and postflight assess-
ments of the pilots are such items as the physio-
logical-response pattern during standardized ex-
ercise tasks (bicycle ergometer) and response
patterns to a psychological-performance test
(complex coordinator—an improved version of
the device reported by Mashburn**). Inflight mea-
surements included heart rate, blood pressure,
pulmonary ventilation, and other psychophysio-
logic parameters.

The canyon runs (reminiscent of United Artists
633 Squadron) and U.S. Army “knap of the
earth” flights demand a great deal of the pilots.
Should vigilance deteriorate in these activities
below a certain point, the consequences are tragic.
The study, therefore, represents an attempt to
determine the psychophysiologic cost of flying
these missions.

Among the check-pilot’s observations in the
study are an increase in “roughness” on the con-
trols during the latter part of the 8 hours, includ-
ing the development of a certain degree of
sloppiness.

These inflight-performance observations are be-
ing correlated with the psychomotor task tests.
Also, a degree of cardiovascular system fatigue
was detected. At times, pilots who had pulses
in the 60- to 70-beat-per-minute range while fly-
ing routine profiles, demonstrated 120 beats per
minute or more during certain portions of the
canyon runs and at later periods during the flight
day.

The complete analyses of the study will be
published by the investigators in the following
months.



AM 65-13

FATIGUE IN AVIATION ACTIVITIES

Stanley R. Mohler, M.D.

Approved by Released by
Stentor A “erN\e-hhew yy wh Wale
Srantey R. Mouter, M.D. M. S. Wuirs, M.D.
Dreecror, CARI Feperat Arr SuRGEON
March 1965

FEDERAL AVIATION AGENCY

Office of Aviation Medicine
Civil Aeromedical Research Institute
Oklahoma City, Oklahoma



ford on civil air-crew fatigue effects on perform-
ance,?0?

Studies relating to the above areas of inquiry
may be found in the early aeromedical literature,
including the 1918 report by Wilmer,!* the 1918
report by Henderson and Seibert,** the 1918 re-
port by Dunlap,’* the 1920 report by Cruchet,%*
and the 1939 report by Barmack.®

Recent newspaper and magazine reports have

~ brought to general attention the subject of pilot
fatigue.® + 1.65 The occupational circumstances
of today’s air-transport pilot has been reported by
various pilots themselves. ® Fahnestock pre-
dicted certain fatigue problems in air-transport
pilots at the Second National Clinic for Domestic
Aviation Planning held in 1944 in Oklahoma
City, and recommended appropriate research.*?

out in its Advance Notice of Proposed Rule
Making—Notice 63-34, noted that crew fatigue at
the time of an emergency (including stewardess
fatigue) can impair the efficiency of emergency
escape.” 7

ALPA’s response to the Notice reflects con-

* siderable thought, and the imaginative develop-

Jordanoff, a year earlier, at the 1943 clinic, dis-

cussed the topic also.**

Figures on airline-pilot inflight incapacitations
have been prepared by Mr. Orlady, and continued
observation of these statistics may prove valuable
in estimating the role played by fatigue in avia-
tion activities (by a study of the types of in-
capacitations in relation to the job circum-
stances) 3% 8

Fatigue in non-air-carrier flying can become
quite serious if the pilot (for example, an execu-
tive pilot) is frequently called at irregular hours
for flights to unfamiliar fields, often under IFR
conditions. Billings et al. have recently discussed
this matter:

Recently, Betty Miller (who, with her husband
Charles Miller, owns the Santa Monica Flyers),
just-announced Harmon-trophy winner for her
solo California to Australia flight, told the author
that fatigue was her main concern on the hop
from Honolulu to the continent. Fatigue, thus,
pervades all aviation activities, and the FAA has
recently made available (primarily aimed at gen-
eral aviation pilots) the booklet, free of charge,

< Medical Facts for Pilots."* Thousands of copies
have been individually requested by general avia-
tion pilots, pilot organizations, and aircraft com-
pénies. It has already been translated into
Spanish, and the demand for this information,
containing comments on fatigue, illustrates the
widespread interest in the subject in all parts of
the world.

Also, the FAA recently published emergency
evacuation information and, as was also pointed

10

ment of a “duty time” hand computer bears
serious study.*

The future will bring forth new achievements
in the mitigation of fatigue. As pointed out by
Dr. Schwichtenberg, new miniaturized portable
medical equipment, which measures “rates” of
change in psychobiological parameters in real
time under actual work conditions through the
use of miniaturized computers, stands to revolu-
tionize the practice of aviation medicine.” The
impact of these developments on scheduling and
other aspects of aircrew activities will be
immense.

; VII. Recommendations.

It is recommended that the following seven
approaches be aggressively pursued:

A. The accomplishment of an accurate monitor-
ing system of the incidence (as opposed to preva-
lence) of appearance of new stress-related symp-
toms and conditions in specific pilot populations
(identified in relation to aircraft, route, and
schedule). In this manner, fatigue and stress-
producing situations can be pinpointed in an
early stage and corrected.

B. The incorporation of recently evolving bio-
logical-engineering data in cockpit construction,
layout, and environment, including more comfort-
able oxygen masks, enhanced seat comfort, de-
creased noise and glare, improved restraint-
system efficiency and comfort, and better tempera-
ture and humidity control (factual body-dimen-
sion figures on present airline pilots—as opposed
to existing data on nonpilot populations—should
be obtained in order that the cockpits can be
engineered for the actual persons who will use
them).

C. The individualization, insofar as possible, of
scheduling regimens, so that those who are least
susceptible to East-West time-zone biological
asynchrony are assigned to these routes (there is
apparently a wide individual variation in sus-
ceptibility to this effect).

D. The continuation of close rapport on the
subject of fatigue among pilots, manufacturers,
airline management, and flight surgeons, nation-


hands of the engineers, plus cockpit and seat di-
mensions, coupled with range of motion require-
ments, would preclude such unhappy situations
and further decrease the annoying circumstances
that enhance the evolution of fatigue states.
Fruitful studies of the conditions that can
foster occupational fatigue and fatigue-related
symptoms have been accomplished by CARI
psychologists in cooperation with air-traffic con-
trollers. These studies involve various scheduling
procedures, VFR versus IFR situations, and
other considerations, including age.** Among the
interesting findings were the detrimental effect of
rotating from one shift to another in 8 hours
or less, the increased incidence of stress-related
symptoms with years of experience (from which
the investigators are now attempting to separate
the factor of aging), and the finding that a wide
difference existed in all of these considerations
between certain facilities. The long-term level of
morale in a given component appears to be highly
significant with respect to the degree of symp-
toms, and it is beginning to appear that aging
alone, as a factor in this respect, is not as signifi-
cant as “occupational exposure,” or “experience.”
A point for all of us to keep in mind, however,
is, as Richard Pearson has noted, that there is
no necessary relationship between performance
and subjective fatigue.** In other words, work-
decrement criteria do not always demonstrate a

performance deterioration with fatigue. "This is ,

an important matter, since, although a given occu-
pational population continues to turn out a
creditable service, it may be doing so under ad-
verse circumstances that ultimately take a toll
in terms of permanent protoplasmic alterations.
The physician in industrial health is, thus,
through considerations associated with his Hip-
pocratic Oath, obligated to remain cognizant of
the long-range medical consequences of occupa-
tional stresses on his patients and to do what
he can to alleviate the evolution of functional or
organic untoward conditions.’ * % 1 105

Similarly, the individual has the reciprocal

obligation to avoid detrimental activities during

off-duty hours that compromise the industrial
physician’s efforts. For example, the mind and
body are inseparable, and a certain amount of off-
duty time should be devoted to physical condi-
tioning. The better the individual is in this re-
spect, the less susceptible is he to the onset of
fatigue.

x

Numerous observations on the above topic in
the aviation context have been made, including
those by Turner in 1910, Grahame-White in
1912, #* Hamel in 1914, * Scott in 1922, Grow
in 1936,* Balke in 1962,’ and Dill in 1963.

Since the factor of aging (biological versus
chronological) is intertwined within this total
picture, several efforts are bearing fruit in the
aviation context. Among them are the “physio-
logic-age ratio” study of disease-free pilots made
at the Lovelace Foundation, the studies by the
various airlines (notably United Airlines, at its
Washington, D. C., medical facility) and the
FAA studies.® *% 7 *

For the first time, timely data is now quickly
available concerning the total numbers of active
pilots in all age groups in all types of aviation
(this is made possible through the utilization of
modern computer techniques—IBM 7040—as a
tool by the FAA’s Aeromedical Certification Di-
vision in Oklahoma City—active pilots have cur-
rent medical certificates)

This data is of value to all interested in avia-
tion activities and is especially useful with respect
to the continuing review of aeromedical stand-
ards The older, continuously active pilot has
survived in large measure because of ability,
judgment, good physical condition, and good
equipment, and the more we can do to enhance
these conditions, the better for all concerned.

Among the existing studies to assist in accom-
plishing this latter aim are those by Barron on
decompression protection and negative-ion elec-
trostatic-field effects on pilots,® 10 by Cohen on the
measurement of pilot mental effort,?* by Diamond
on the fatiguing effects of red light, by Ganslen
et al.‘ on certain antifatigue drugs, by von
Gierke on vibration and noise,!* by Graybiel on
flicker-fusion in fatigued aviations,° by Hawny-
lewicz and Blair on fatigue recovery,* by
Hornick on helicopter vibration,** by Bourne on
inactivity effects,’ by Jackson on longrange air-
crew fatigue,’ by Lowenstein (the inventor of
pupillography—an excellent means of measuring
eye fatigue) on psychosensory restitution,** by
Marchbanks et al., on overwater missions,” by
McFarland on wartime pilots, by Miller on sero-
logic changes in flight fatigue, by Stegall on
tilt-table cardiovascular alterations,” by Tyler on
the drug alleviations of fatigue,’* by Pierson and
Lockhardt on fatigue in women, and by Wel-



Dr. Halberg of the University of Minnesota and
certain of his associates.

Six healthy subjects were intensively studied
with respect to the effects of intercontinental-jet
flight on day-night biological cycling and per-
formance. They received 3 consecutive days of
biomedical assessment in Oklahoma City at
CARI, wihch yielded a reference of biological
time (geared to the Central Standard Time
zone), and were flown to Tokyo (an 18-hour
trip) for a 10-day layover. The biomedical
measurements were repeated on alternate days,
and the subjects returned to Oklahoma City
(again, a trip of about 18 hours). Assessments
were continued for 3 consecutive days.

Among the measurements made were rectal
temperature (continuously worn thermistor
probe—30-minute-interval recordings), reaction
time (speed of manual reaction time to an au-
ditory stimulus and certain visual stimuli—peri-
odic intervals), subjective fatigue (a scaled list
is checked—periodic intervals) and critical
flicker-fusion thresholds (determined periodically
each day).

The subjects left Oklahoma City at 0810 CST
(2310 Tokyo time) and, following a 1-hour 40-
minute wait in Anchorage, landed in Tokyo at
0200 CST (1700 Tokyo time). When they left
Tokyo 10 days later, it was 0930 Tokyo time
(1830 CST) and, once again, after a wait in
Anchorage (this time 2 hours and 30 minutes),
the subjects arrived in Oklahoma City at 0200
Tokyo time (1100 CST).

The researchers will report the results of this
study through the usual scientific and aviation
media. Preliminary findings indicate that, for
the group average, the body-temperature cycle
peaked about 4 hours early on the first day in
Tokyo with reference to Tokyo time (at 1200
Tokyo time—2100 CST—instead of peaking be-
tween 1400 and 1700 hours Tokyo time as is the
case of those living in Tokyo—the 1400 to 1700
hours temperature local-time peak is character-
istic of persons living in a given time zone with
reference to their local time—note also that
circadian-periodicity studies represent an example
of studies wherein the use of Greenwich time
can, under certain circumstances, complicate
rather than simplify the analyses). By the third
day in Tokyo, however, the body-temperature
eycle was adjusted to Tokyo time and peaking
in phase with Tokyo.

Also, the reaction times were substantially
slower during the first day in Tokyo, with return
to the earlier “quickness” level by the third day.
Mental-decision time as measured with a special
technique was impaired to a still greater degree
on the first day in Tokyo, with return to the
preflight level by the third day.

Subjective fatigue, as felt by the subjects, rang-
ing from extremely alert to extremely tired, hit
its low point on the first day in Tokyo but was
at the preflight level by the third day. By the
fifth day, the feelings of fatigue began to return,
possibly indicating that too long a layover can
have adverse effects in this respect.

Critical flicker-fusion thresholds did not change
significantly in the present subjects, possibly be-
cause they did not have actual psychomotor
flight-task responsibilities while enroute.

Following the return to Oklahoma City, the
investigators found certain surprising things. The
subjects’ average temperature returned rapidly to
CST time with respect to peaking. In fact, in
this respect, the subjects were back on schedule
in 1 day. There was, however, some depression
on the first day in the amplitude of the body-
temperature swing of the subjects (the full re-
port will discuss this in detail).

An increase in reaction time occurred on the
first day of return to Oklahoma City, greater in
extent than on the first day in Tokyo. Decision
time increased only slightly, however. Subjective
fatigue showed a decrease on the first day “back
home” in Oklahoma, perhaps because of relief
from the boredom that apparently arose toward
the end of the long layover in Tokyo. Fatigue
feelings did develop on the second day home,
however, but began to disappear on the third
day. Critical flicker-fusion thresholds showed
little change.

The mean for all subjects with respect to rectal
temperature demonstrated that biological time
had shifted from Oklahoma City to Tokyo time
within 3 days. On the return trip, only 1 day
was required for the shift to Oklahoma City
time. Drs. Hauty and Adams report that there
is a considerable variation in individual response
in adjusting to local times. One subject shifted
to Tokyo time in 1 day, while another had not
accomplished a phase shift on any of the days in
Tokyo. The proficiency in accomplishing task
functions was adversely affected (to a substantial


rest, but we are not concerned with these latter
matters here.

There is a nebulous nature in the conceptualiz-
ation held in various quarters of this fatigue
matter. Just as some might define increasing
amounts of cold in terms of decreasing amounts
of heat, fatigue has been thought of as the deple-
tion of some physiological substance. Others
have conceived of fatigue as resulting from the
gradual increase of some substance during the
work period. Actually, all this is now known
‘to be too simple and is remiscent of the ancient
Greek attempt to explain the events of nature in
terms limited to earth, air, fire, and water.

IL. Definitions and Considerations.

The word fatigue is derived from Latin and

French origins, and is defined as “weariness from

. bodily labor or mental exertion.” *° Weariness is
defined in the same reference as “the state of be-
ing tired, having lassitude, or exhaustion of
strength.”

Physical fatigue, which may be objectively
measured (increased reaction time, decreased
strength, increased blood lactic acid, decreased
blood glucose, increased lag in pupillary response
time to light, decreased ability for rapid binocu-
lar fusion, increased time of visual accommoda-
tion to alternating near and far points of vision,
decreased muscle tonus, increased loss of electro-
lytes through cutaneous excretory organs, de-
creased circulating blood volume, increased uri-
nary corticosteroids and catecholamines, de-
creased muscle glycogen, increased instability of
neuromuscular coordination, etc.), is well docu-
mented as resulting from alterations of such en-
vironmental factors as: temperature, humidity,
color, light intensity, noise, vibration, odors,
gases, barometric conditions, and ozone. Several
references cover these points.

In addition, physical fatigue results from pro-
tracted immobility, excessive loss of sleep, ill-
nesses, and advanced aging changes.

Interestingly, since the mind cannot be sep-
arated entirely from the “whole” individual, the
mind is, therefore, the end “receptor” for the
perception of the degree of physical fatigue.
Consequently, although certain pharmacologic
agents (amphetamines, ethyl, alcohol, certain
tranquilizers, Spartase,* (see footnote) and other
drugs) ) may modify the perception of the degree

*Spartase is the Wyeth Laboratories trade name for the
potassium and magnesium salts of aspartic acid.

“jective, aspect of fatigue.

wo

“ingestion, and metabolic-waste removal.

of physical fatigue (and, in the case of Spartase,
may actually diminish certain objectively meas-
ured physical-fatigue states), the physical results
of expending kinetic, chemical, thermal, and
electromagnetic energy, from potential energy
stores, are biologically inevitable.*

Biological restitution of the above conse-
suences of physical effort follows rest, sleep, food
Any-
_ thing interfering with these restrictive processes

(cutting too many time-zones, inadequate accom-

modations, outside disturbances, etc.), will
heighten the unresolved sequelae of physical fa-
tigue.

Physical fatigue is, therefore, but one side
of the mind-body “biological coin,” since re-
siding within the head side is the mental, or sub-

Mental fatigue can,
as is clear from the above, be the result of physi-
cal fatigue or can exist as the primary entity in
an individual whose physical baseline is within
“rested state” limits.

“ «Symptoms of mental fatigue include increased
irritability, decreased attention span, increased
susceptibility to err (therefore of vital conse-
quence in aviation-accident causation), decreased
libido, increased anxiety, decreased recent mem-
ory, increased tendency to insomina, decreased
cooperativeness, increased susceptibility to de-
pressive states, decreased acceptability to con-
structive criticism, increased tendency to with-
drawal from avocational social undertakings and
hobbies, decreased (sometimes paradoxically in-
creased to an excessive point) interest in per-
sonal care and hygiene, increased tendency to
use pharmacologic crutches (ethyl alcohol, chain
smoking, tranquilizers, barbituates, bromides,
nerve tonics, etc.) and decreased gastrointestinal
efficiency which may result in indigestion, con-
stipation, or in some cases, diarrhea (spastic in-
testinal states).

Serious performance decrement is likely to re-
sult from one or more of the above symptoms.
Causes of mental fatigue may be: repeated sleep
inadequacies, excessive psychosensory task de-
mands, “time-pressure” stresses (too short a time
to accomplish the task, frequent unanticipated
interruptions of work procedures, excessive task
loading with trivia, frequent emergencies or
false alarms) inadequate compensation for task,
inadequate recognition of accomplishments, in-
adequate task challenge and interest, ambiguous


10.

11.

13.

14,

15.

16.

17.

18.

19,

|. Adams,

. Balke, Bruno.

REFERENCES

Thomas, Funkhouser, Gordon E., and
Kendall, Warren W. “A Method for the Measure-
ment of Physiologic Evaporative Water Loss,”
CARI Report 68-25, 1963, pp 1-15.

Albéts, William “Present Philosophy of Aeromedical
Standards Development,” Aerospace Medicine, June
1968, pp 515-519.

. ALPA . “Flight Time—Duty Time Regulations,”

ALPA Presentation to FAA, October 1963, pp 1-12.

. Armstrong, Harry G. Principles and Practive of

Aviation Medicine, Williams and Wilkins, Baltimore,
1939, pp 1496.

Atherton, John. “Do Pilots Get Jet Fatigue-” Herald
Melbourne, Melbourne, Australia, March 31, 1964.
“Experimental Evaluation of Work
Capacity as Related to Chronological and Physio-
logical Aging,” CARI Report 63-18, Oklahoma City,
1963, pp 1-6.

Balke, Bruno. “Human Tolerances,” CARI Report
26-6, 1962, pp 1-15.

. Barmack, J. E, “The Length of the Work Period

and the Work Curve,” Journal of Experimental
Psychology, 25, 1939, pp 109-115.

. Barron, Charles. “Effects of Slow and Rapid De-

compression on Humans at 45,000 Feet,” Final
Report, FAA Contract FA-3082, Lockheed Aircraft
Company, Burbank, California, 1963.

Barron, ©. L, and Dreher, J. J. “Effects of Electric
Fields and Negative Ion Concentrations on Test
Pilots,” Aerospace Medicine, January 1964, pp 20-23.
Barwood, A. J. “Independent Investigation of Work-
Load and Working Conditions of British European
Airways’ Pilots,” Flying Personnel Research Com-
mittee, Air Ministry, G. B., November 1961, pp 1-15.

. Bauer, Louis Hopewell. Aviation Medicine, Oxford

University Press, New York, 1943, pp 1-501.
Beck, Richard. “Jet Crew Fatigue,” ALPA Presenta-
tion, January 31, 1964, pp 1-26.

Bennett, Edward, Degan, James, and Spiegel, Jo-
seph. Human Factors in Technology, McGraw-Hill
Co., New York, 1963, p 178.

Bert, Paul. Barometric Pressure (translation of
Bert's 1877 book into English by Hitchcock and
Hitchcock), College Book Company, Columbus, Ohio,
1943, pp 1-1054.

Billings, Charles, et al. “Medical Aspects of Business
Aviation,” Aerospace Medicine, August 1964, pp
788-798.

Bourne, Geoffrey H. “Neuromuscular Aspects of
Space Travel,” Physiology of Man in Space (Ed.
J. H U. Brown), Academic Press, New York, 1963,
pp 1-59.

Bryant, Samuel W. “What Jet Travel Does to Your

Metabolic Clock,” Fortune, November 1963, pp
160-164,
Byrne, Don. “What's Being Done About Crew

Fatigue,” American Aviation, February 1964, pp
65-66,

). Cameron, C., and Cumming, R. W. “A Preliminary

Study of the Effects of Cabin Temperatures on
Pilot Performance in R.A.A.F. Fighter Aircraft,”

13

21.
22.
23.

25.
26.

27.

29,

30.

31.

36.
37.

40,

A.

. Civil

. Cohen, S. I., and Silverman, A. J.

. Crane, James E,

. Dunlap,

Human Engineering Note 16, Aeronautical Research
Laboratories, Australian Defence Scientifie Service,
Melbourne, December 1963, pp 1-30.
Civil Aeronautics Board. Docket 2-2068,
Civil Aeronautics Board. Docket 2-2969,
Civil Aeronautics Board. Docket 2-3636,
‘Aeronautics Board. Docket 24365, 1962.
Civil Aeronautics Board. Docket 2-4867, 1962,
Civil Aeronautics Board. Report SA-375, File No.
1-0012, Washington, D. C., June 24, 1964, pp 1-8.
Code of Federal Regulations. “Flight Time Limita-
tions,” Title 14—Aeronautics and Space, Part 40-
$20, G.P.O., Washington, D. ©. January 1, 1964,
pp 89-90.

1962,
1962.
1962.

“Measurement
of Pilot Mental Effort,” AGARD Report 148 May
1957.

Comfort, Alex. The Biology of Senescence, Rinehart
and Company, New York, 1956, pp 1-257.

Cone, Howard M, “Pilots as One Pilot Sees Them,”
Printed Presentation to Seminar on Aviation Medi-
cine, Guggenheim Center for Aviation Health and
Safety, Harvard School of Public Health, February
1, 1961, pp 1-6.

Crane, Janiés E. “Survey of Fatigue and Tension
Among Jet Crews,” Office: Stamford, Connecticut,
August 16, 1961.

“The Time Zone Fatigue Syn-
drome,” The Flying Physician, Vol 7, No. 4, October
1963, pp 19-22.

. Cruchet, Rene, and Moulinier, Rene. Air Sickness:

Its Nature and Treatment, John Bale, Sons, and
Danielsson, London, 1920, pp 1-96.

. Diamond Stanley. “Effects of Red Lighting on Ac-

commodation in Aircrew Personnel,”
Medicine, November 1963, pp 1005-1006.
Dill, D. B., Robinson, S., and Newton, J. L. “Work
Tolerance: Age and Altitude,” CARI Report 63-33,
Oklahoma City, 1963, pp 1-8.

Downie, Don. “A New Flying Concept: the Pinch-
Hitter,” OAPA Pilot, December 1963, pp 23-28.
DuBoise, Eugene F. “The Anatomy and Physiology
of the Airplane Cockpit,” Aeronautical Engineering
Review, April 1945, pp 1-8.

Knight. “Psychologic observations and
Methods,” Journal of American Medical Association,
October 26, 1918, p 1392.

Aerospace

. Earhart, Amelia, Last Flight, Harcourt Bruce and

Company, New York, 1957, pp 1-226.

FAA. “Flight Time Limitations,” Advanced Notice
of Proposed Rule Making, 14 Code of Federal Regu-
tions, Part 42, Notice 63-34; Docket No. 1927,
August 27, 1963.

FAA. “Ground Rest Periods and Duty ‘Time Limita-
tions for Flight Crews of Three or More Pilots
and Additional Airmen, as Required,” 14 Code of
Federal Regulations, Part 42, Notice 64-13; Docket
No. 4028, March 3, 1964.

. Fahnestock, M. K. “Aviation Education in Colleges

and Universities,” in The Second National Clinic
for Domestic Aviation Planning, Harlow Publishing
Co., Oklahoma City, November 1944, pp 281-282.



FATIGUE IN AVIATION ACTIVITIES

I. Introduction.

On October 14, 1963, an air-transport heli-
copter operating on a regular schedule crashed
on Long Island. Fatigue failure of the drive
quill shaft is given as the probable cause of the
accident by the Civil Aeronautics Board.**

This is an example of “structural fatigue,” a
circumstance clearly detrimental to air safety.
But how about the role of “biological fatigue” in ~
air safety? Biological fatigue is less readily
measured after the fact than is structural fatigue
and is more difficult to relate as a casual factor
to accidents.

The Civil Aeronautics Board has listed fatigue /
as a causal factor in a number of relatively re-
cent accidents. For example, on September 26,
1962, an air transport-category aircraft (not on
a regularly scheduled flight landed at Spartan-
burg, South Carolina, during the night in light
rain conditions. While swinging into position at
the ramp, the tail of the airplane hit a large
object in the ramp area, substantially damaging
the stabilizer and elevator.

The investigation revealed that the Captain
and his copilot had been on duty for almost 19
hours at the time the accident occurred and that
“impaired efficiency of the pilots caused by fa-
tigue” was a probable cause of this incident.”

It is not unusual to find fatigue listed as a
probable cause in aerial applicator accidents. In
one example as a probable cause in aerial appli-
cator accidents. In one example, a pilot stalled
in a procedure turn to the left and reported later
that he had sprayed 700 acres between 8:00 a.m.
and 6:00 p.m. just prior to the accident, and was
“just plain tired.”* In another example, the
pilot over-controlled on takeoff and caused his
landing gear to fail. He had been flying for a
considerable time on the day of the accident and
was “very tired.”*! Another pilot veered his
plane off the runway during the landing roll. Tt
nosed over. Investigation showed that the pilot
had had only 8 hours sleep during the 48-hour
period preceding the accident.*

*CAB Docket 24442.

Among  light-aircraft business or pleasure
flights, fatigue is listed as a probable cause on
one case of “leveling off too high.” ** In another
case, fatal to all three occupants, which occurred
during poor-visibility weather conditions near
Pinta, Arizona, “reduced physical and mental
efficiency of the pilots caused by fatigue,” is listed
as a probable cause.”

It is clear, therefore, that the deleterious effects
of excessive fatigue continue to take a toll in
general aviation activities, since all of the above
examples occurred relatively recently. Not so
clear is the true impact of fatigue in air-carrier
activities.

Fatigue is a concomitant of all protracted hu-
man endeavor. In general, fatigue is produced
more readily by more demanding tasks. It may
also be markedly heightened through the imposi-
tion of “time pressure” on the operator. At some
point in the buildup of fatigue in a given person,
rest, becomes mandatory. At an earlier point,
the developing fatigue results in a degree of
deterioration in the quality of performance that,
of itself, makes task discontinuation desirable.

This all sounds very simple and has Jed, from
time to time, to an oversimplification of the fa-
tigue matter as it is found intertwined today in
aviation activities. For reasons given later, fa-

tigue should neither be dismissed as an unim- /

portant entity nor conveniently embraced as the
culprit in various untoward situations in air-
carrier activities.

Definitions of fatigue in humans are often
stated in general terms and may include the term
“weary.” They may primarily reflect physiolog-
ical changes (as occur during heavy physical ex-
ertion) or may focus on “subjective” changes, as
produced by stressful mental demands, lack of
sleep, or monotony, and include biochemical and
yeaction-time measurements. Of course, fatigue
can also arise as a result of certain medical con-
ditions (anemias, cardio-vascular defects, etc.),
advanced aging changes, and even enforced bed





ally and internationally, so that all practicable
means can be utilized to keep fatigue at a mini-
mum under the requisite operational circum-
stances.

E. The continuation of interdisciplinary aero-
medical research on fatigue in aviation activities,
since there exists a distinct problem (more ap-
parent in the non-air-carrier segments of aviation
as revealed by Civil Aeronautics Board accident
reports) from which airline pilots are by no
means immune.

F. During its investigation of air-carrier acci-
dents, the accomplishment of a more detailed
assessment by the Bureau of Safety of the Civil

il

Aeronautics Board of the possible role of fatigue
in relation to the accident under scrutiny.

G. The designation within each airline (sched-
uled and nonscheduled and with or without a
medical department) of one person who will
have the responsibility of keeping his finger on
the “fatigue pulse” of the aircrews, maintaining
a repository of crew observations of apparent
fatigue-promoting circumstances associated with
the respective airline equipment, routes, operating
practices, and schedules. In this way, periodic
scrutiny of the data relative to respective equip-
ment, schedules, etc., would afford a clearer
picture of specific fatigue-promoting circum-
stances and enhance remedial activity.



43.

44.

45.

46.

47,

4

49.

50.

Bt.

8

g

56.

3

59.

60,

61.

6la.

2

. Jackson, K. F.

Fogel, Lawrence J. Biotechnology: Concepts and
Applications, Prentice-Hall, Englewood Cliffs, New
Jersey, 1963, pp 203-209.

Ganslen, R. V., Balke, B., Nagle, F. J., and Phillips,
E. EB. “Effects of Some Tranquilizing Analeptic and
Vasodilating Drugs on Physical Work Capacity and
Orthostatic Tolerance,” CARI Report 63-34, Okla-
homa City, 1963, pp 1-8.

Gierke, von Henning E. “Transient Acceleration,
Vibration and Noise Problems in Space Flight,” in
Bioastronautics (Hd. Karl B. Schaefer), The Mac-
Millan Co., New York, 1964, p 61.

Graybiel, A. Lilienthal, J. L., and Horwitz, 0.
“On Flicker Fusion Tests as a Measure of Fatigue
in Aviators,” Aviation Medicine, May 1948, pp
356-859,

Grahame-White, Claude, Aviation, Collins Clear-
type Press, London, 1912, pp 1-262.

Grow, M. C. “A Study of Fatigue,” Mititary Sur-
geon, 78, 1936, pp 103-119.

Halaby, N. E. “FAA Develops Unique Studies to
Determine True Age,” The Air Line Pilot, February
1962, pp 4-7.

Hamel, Gustav, and Turner, Charles. Flying, Some
Practical Experience, Longmans, Green and Co., New
York, 1914, p 382.

Hartman, Bryce O., Simons, David G, and Ball,
Thomas P. “Fatigue Effects in 24-Hour Simulated
Air Transport Flights: Changes in Pilot Profici-
ency,” presentation to Aerospace Medical Associa-
tion, April 29, 1963, Los Angeles, California.

. Hauty, G. T., and Adams, T. “Pilot Fatigue: Inter-

continental Jet Flight. I. Oklahoma City—Tokyo,”
Preliminary Summary Report, Civil Aeromedical
Research Institute, July 1964, pp 1-8.

(1. Incidence of Self-reported Symptoms, 2. Experi-
Biomedical Survey of Air Trafic Control Facilities

. Hauty, G. T., Trifes, D. K., and Berkley, W. J.

ence and Age), Civil Aeromedical Research Insti-
tute, Oklahoma City, 1964.

. Hawnylewiez, B. J., and Blair, W. H. “Physiological

in a
Chi-

Measure of Training Fatigue and Recovers
Human,” Armour Research Foundation Repor
cago, Illinois, 1963.

Henderson, Yandell, and Seibert, E. G. “Organiza-
tion and Objects of the Medical Research Board,
Air Service, U.S. Army,” Journal of American Medi-
cal Association, October 26, 1918, pp 1382-1400.
Hornick, Richard J. “Human Exposure to Helicopter
Vibration,” Bostrom Research Laboratory Report
138, Milwaukee, February 1961, pp 1-7.

“Aircrew Fatigue on Long Range
Reconnaissance,” FPRC Report 907.2, Air Ministry,
London, 1956,

Jordanoff, Assen. “Technical Aviation Training,” in
The First National Clinic of Domestic Aviation
Planning, Harlow Publishing Co., Oklahoma City,
November 1943, pp 173-179.

Juin, Gerard. “Causes of Fatigue,” presentation to
Committee B of IFALPA, March 8, 1961, pp 1-8.
Juin, Par. Gerard. “Les Decalages Horaires,”
Archives des Maladies Professionnelles, T. 24, 1963,
pp 112-116,

Kafka, M. Martyn. Flying Health, Military Service
Publishing Company, Harrisburg, Pennsylvania, De-
cember 1942, pp 1-248.

Kidera, G. L, “Aeromedical Aspects of Commercial
Jet Operation,” Aerospace Medicine, July 1963,
pp. 601-605.

14

62.

65.
66,
67.

69.

70.

a
8

74.

5.
7

e

77.

3

79.

80.

81.

&

83.

84.

. Ovington, Earle L. “The

Lavikov, A. A. Aviatsionnaya Meditsina, Moscow,
1961, pp 1-275.

Lederer, Jerome. Safety in the Operation of Air
Transportation, The Lane Press, Burlington, Ver-
mont, 1989, pp 1-68.

Lindberg, Charles. The Spirit of St. Louis, Charles
Scribner's Sons, New York, 1953, pp 1-498.
Lodeesen, Marius. “Tired Jet Pilots,” Flying, March
1963, p 33.

Lowenstein, Otto. Ezperimentelle Hysterielenre,
Verlag von Friedrich Cohen, Bonn, 1923, pp 1-412.
Marchbanks, Vance H., Hale, Henry B., and Ellis,
James P. “Stress Responses of Pilots Flying 6-Hour
Overwater Missions in F-100 and F-104 Aircraft,”
Aerospace Medicine, January 1963, pp 15-18.
Mashburn, N. C. “Mashburn Automatic Serial Re-
action Apparatus for Detecting Flying Aptitude,”
Journal of Aviation Medicine, V, 1934, p 155.
McFarland, Ross A. “Fatigue in Aircraft Pilots,”
War Medicine, Philosophical Library, New York,
1942.

McFarland, Ross A. Human Factors in Air Trans-
portation, MeGraw Hill Book Company, New York,
1953, pp 1-830.

. McFarland, Ross A. “Selected Problems in Civilian

Jet Air Transportation,” Printed paper at World
Congress of Aviation Medicine, Louvain, Belguim,
September 25, 1958, pp 1-8.

Miller, W. H. Ginsberg, A. M. “Metabolic and
Serologic Changes in Flight Fatigue,” Journal of
Aviation Medicine, II, 1981, p 155.

Mohler, S. R. “Aging and Pilot Performance,”
Geriutries, February 1961, pp 82-88.

Mohler, S. R. “Select Mach Medical Matters and the
SST,” Proceedings of the Airlines Medical Directors
Association, May 9, 1964, pp 1-29.

Mohler, S. R. “Wiley Post's Aerospace Achieve-
ments,” Airpower Historian, July 1964, pp 66-70.
Mohler, Stanley R., and Siegel, P. V. Medical Facts
for Pilots, Federal Aviation Agency, P. 0. Box 1082,
Oklahoma City, Oklahoma, January 1964, pp 1-8.
Mohler, Stanley R., Swearingen, John J., McFadden,
Ernest B., and Garner, J. D. “Human Factors of
Emergency Evacuation,” SAB-ASME Publication
851 B, April 1964, pp 1-11.

Mohler, Stanley R. “The General Biology of
Senescence,” Postgraduate Medicine, December 1961,
pp 527-537.

Morgan, Clifford T., Cook, Jesse S., Chapanis,

Alphonse, and Lund, Max W. Human Engineering
Guide to Equipment Design, McGraw-Hill Co., New
York, 1963, p 31.

Nagle, Francis J., Balke, Bruno, Ganslen, Richard
V., and Davis, Audie W. “The Mitigation of Physi
cal Fatigue with Spartase,” CARI Report 63-
Oklahoma City, 1963, pp 1-10.

Orlady, Harry. “Sudden Tiness in Flight,” presenta-
tion to Advanced Aviation Medical Examiners
Seminar, Federal Aviation Agency, San Francisco,
California, February 6, 1964.

2,

‘hie Factors in Avia-
Medical Association,

tion,” Journal of American
August 1, 1914, pp 419-420.
Pearson, Richard G. “Task Proficiency and Feelings
of Fatigue,” School of Aviation Medicine Report,
57-7, April 1957, pp 1-5.

Pierson, William, and Lockhardt, Aileene. “Fatigue,
Work Decrement, and Endurance of Women in a
Simple Repetitive Task,” Acrospace Medicine, Au-
gust 1964, pp 724-725,