AIR COMMAND AND STAFF COLLEGE

AIR UNIVERSITY

Fatigue Management for Aerospace

Expeditionary Forces Deployment

and Sustained Operations

MICHAEL A. LECLAIR

Major, USAF

Air Command and Staff College

Wright Flyer Paper No. 12

MAXWELL AIR FORCE BASE, ALABAMA

April 2001
Disclaimer

Opinions, conclusions, and recommendations expressed or implied within 

solely those of the author and do not necessarily represent the views of Air 

versity, the United States Air Force, the Department of Defense, or any othe

government agency. Cleared for public release: distribution unlimited.

ii

This Wright Flyer Paper and others in the serie

are available electronically at the Air Universi

Research Web Site http://research.maxwell.af.m

under “Research Papers” then “Special Collections
Foreword

It is my great pleasure to present another of the Wri

Flyer Papers series. In this series, Air Command and S

College (ACSC) recognizes and publishes the “best of 

best” student research projects from the prior academ

year. The ACSC research program encourages our s

dents to move beyond the school’s core curriculum in th

own professional development and in “advancing ae

space power.” The series title reflects our desire to perp

uate the pioneering spirit embodied in earlier generati

of airmen. Projects selected for publication combine so

research, innovative thought, and lucid presentation in 

ploring war at the operational level. With this broad p

spective, the Wright Flyer Papers engage an eclectic ra

of doctrinal, technological, organizational, and operatio

questions. Some of these studies provide new solutions 

familiar problems. Others encourage us to leave the fam

iar behind in pursuing new possibilities. By making th

research studies available in the Wright Flyer Pape

ACSC hopes to encourage critical examination of the fi

ings and to stimulate further research in these areas.

John T. Sheridan, Brig Gen (Sel), US

Commandant

iii

Preface

Having flown in a single-seat cockpit more than 

hours deploying to Southwest Asia, I am familiar with 

negative effects of long duration flights as well as the 

pact transmeridian sorties have on an aircrew’s circad

rhythm. Any attempt to make that experience less pain

for the aviators climbing into their jets during future 

ployments deserves pursuit and further investigation. U

fortunately, a great deal of the information available for 

operational aircrews is either underemphasized at best 

totally ignored by the personnel that the data is intend

to support, the aviators. Typically, fatigue and circad

rhythm disruption are assumed as “necessary evils” t

aviators have no choice but to accept. Yet fatigue can b

significant factor in terms of performance degradation a

must no longer be overlooked. I have amassed the m

current research regarding fatigue and its associa

countermeasures, and I strongly recommend both co

manders and aircrews apply the information presented 

this research paper if they are to continue to safely m

the challenges of an Expeditionary Aerospace Force.

I thank my research advisor for his guidance and c

structive criticism. I thank the flight surgeons at Bro

Air Force Base, Texas, for their contributions of valua

background material as well as drafts for their upcom

revision to the Flight Surgeon’s Checklist.

v

Abstract

Under the new Expeditionary Aerospace Force (E

concept, the US Air Force is capable of deploying and e

ploying in 72 hours or less. Furthermore, the US miss

frequently requires 24-hour activities to meet operatio

demands. Because of its commitment to project pow

with such a rapid fighting force, aviators on contingen

operations will regularly face fatigue-related challen

inherent in sustained and continuous operations, 

well as those from rapid, transmeridian travel. The p

pose of this research paper is to extract all relevant m

terials pertaining to fatigue and aircrews in order to p

vide a plan for equipping Aerospace Expeditionary For

(AEF) commanders and personnel with a historical p

spective, critical information, and new technologies 

enable effective fatigue management. This informat

was attained via an extensive literature search and 

view, primarily utilizing the Internet and the Air Univ

sity Library.

Existing comprehensive scientific literature provi

important physiological information about aviators t

can be used to guide operations and policy. Many ale

ness management strategies aid aircrews and deploy

personnel as well as help them to cope with the ch

lenges of sleep loss and circadian disruption. Both ph

maceutical and nonpharmaceutical countermeasures 

presented. Although valuable, the challenge is for the s

entific information to make its way down from the bo

to the cockpit and be incorporated into flight/duty/r

regulatory considerations. Additionally, new means 

combat fatigue can give AEF commanders insight into 

ture benefits of fatigue research. Commanders, safety 

ficers, and aviators are well advised to familiarize the

selves with the causes of impaired alertness a

countermeasures that can keep chronic fatigue from 

coming a problem. Sufficient knowledge will make it e

ier to predict dangerous situations related to on-the-

sleepiness, recognize warning signs of excessive fatig

in aviation personnel, and take action to prevent fatig

related hazards in the air. This paper concludes with 

vii
recommendation that the USAF AEF Battlelab develo

commander’s handbook as a reference tool for leaders 

make better decisions concerning alertness managem

strategies and fatigue countermeasures.

viii
PART I

Methodology

Introduction

We will continue to hone and improve the EAF concept as we

implement it, incorporating lessons learned from ongoing AEF

deployments.

––US Air Force Posture Statement 2000

The Expeditionary Aerospace Force (EAF) will regula

face fatigue-related challenges inherent in sustained a

continuous operations, as well as those from rapid, tra

meridian travel. Fortunately, there are new techniq

that can blunt fatigue, especially for the first few days 

intense activity required of the Aerospace Expedition

Forces (AEF). Reduction of fatigue and circadian disr

tion will be extremely important to the success of A

goals. The challenges of fatigue must be dealt with a

planned for to maximize human performance and miss

success. A historical analysis of the operations and av

tion will provide the defense for pursuing an initiative t

targets logistical management of fatigue prevention stra

gies through crew rest, sleep countermeasures, and ot

means as crucial as managing bullets and gasoline to 

crease the likelihood of mission success.

The United States Air Force (USAF) doctrine of an ex

ditionary aerospace force and a demand for an accelera

operations tempo increases the likelihood of around-t

clock operations in order to sustain its constant presenc

By flying at night—under greater stress—and in differ

time zones, fatigue has a greater opportunity to impact 

mission. Factors such as exposure to cockpit noise and 

bration, day-to-day stress, lengthy flights, irregular w

schedules, circadian disruption, and inadequate amou

of sleep can compromise aviator performance by prod

ing dangerous levels of fatigue. Although the initial effe

of fatigue often go unnoticed, vigilance, judgment, sit

tional awareness, and crew coordination all may suffer

The methodology applied during this research consis

of a comprehensive review of available materials conce

ing sleep deprivation and fatigue countermeasures. T

author pursued a detailed literature review via the Inter

and the Air University Library, whereby the focus was 

the most current information available. After a detai

3
database was established, the information was cons

dated into a coherent reference source in order to assist 

USAF AEF Battlelab to develop a handbook for comma

ers to use for guidance during AEF deployments. This 

search paper begins by developing a fundamental und

standing of the EAF concepts followed by an explanation 

the basic physiology behind sleep, circadian rhythms, a

fatigue. Once a baseline knowledge of the core mechanis

behind fatigue is established, current countermeasure

both pharmaceutical and nonpharmaceutical—are p

sented. Next, future alertness management strategies 

discussed. Finally, recommendations are made for the B

tlelab to develop its handbook.

There is a wealth of information regarding fatigue a

alertness management strategies. By presenting the m

current pharmaceutical and nonpharmaceutical strateg

available, commanders can make better choices conce

ing ways to enhance personnel’s transition to deployed 

cations and combat the inevitable fatigue associated w

sustained and continuous operations. In order to impr

the EAF concept’s effectiveness, the US Air Force Post

Statement 2000 asserts that servicemen must incorpor

the lessons learned from AEFs currently deployed. T

paper intends to assist in the learning process by show

what can be done to counter fatigue.

Notes

1. Carol S. Ramsey and Suzanne E. McGlohn, “Zolpidem as a Fat

Countermeasure,” Aviation, Space, and Environmental Medicine, Oct

1997, 926–31.
PART II

Background: Historical Perspectiv

Aerospace Expeditionary

Forces Concepts

EAF organizationally links forces in geographically separated

units into standing air expeditionary forces. These forces

would deploy from Air Force installations and be ready to fight

or deliver humanitarian supplies on very short notice.

––Expeditionary Aerospace Force Press Briefing

––4 August 1998

The US national security strategy explicitly states t

the military must maintain our overseas presence to p

mote regional security. The ability to project power gl

ally is “essential for providing options for responding 

potential crises and conflicts, even when we do not h

any permanent presence or a limited infrastructure i

region.”1 The EAF concept answers this country’s need 

a rapid, deployable force to project our nation’s will a

protect its interests. The concept also addresses the 

Force vision to organize, train, equip, and sustain its To

Force through enhanced sustainability, readiness and 

sponsiveness, and through fostering an expedition

warrior mindset.2 The EAF structure can be summari

in four statements.3 The rotational structure cent

around 10 AEFs—employed two at a time for 90 days o

a 15-month cycle. Additional manpower is made availa

to support each EAF component. The deploying units 

be lighter and leaner—capable of deploying in 72 hours 

less. The deployment forces must be organized a

trained to meet the requirements of the contingency op

ation they will perform.

Figure 1 describes the AEF format by highlighting 

key components necessary to sustain an EAF. Some of 

issues confronted by a force that is capable and comm

ted to putting bombs on target anywhere in the world 

72 hours or less is the disruption of circadian rhythm

operations tempo-induced fatigue, and the potential ill 

fects these stressors place upon aviators.

Fatigue and Aviation Safety Relationship

With a basic knowledge of the EAF concept and the f

that AEFs might face difficulties adjusting to their deplo

7
environment, the impact fatigue has on safety can now 

scrutinized; and the potential danger areas for AEFs c

be established.

Mishap Rates. Maintaining safe aviation operations 

complex task. For the foreseeable future, aircrews rem

essential to safe, efficient, and reliable aviation activit

Therefore, the importance of addressing human-rela

error—which accounts for approximately 70 percent of a

ation accidents—remains critical to maintaining and 

proving safety.4 Fatigue generated by operational requ

ments can degrade human performance capability a

reduce the safety margin. Estimates suggest that 75 p

cent of night workers experience sleepiness on every ni

shift; and for 20 percent of them, sleepiness is so sev

that they actually fall asleep.5 Approximately one of five 

ports to the National Aeronautics and Space Administrat

(NASA) Aviation Safety Reporting System (ASRS) ment

Expeditionary Aerospace Force

Source: Headquarters USAF/XOPE, EAF Implementation Division, Aerospace E

ditionary Forces, 1 October 1999.

Figure 1. What Are AEFs?
fatigue-related factors.6 Between 1974 and 1992, 

USAF Safety Agency attributed 25 percent of night tact

fighter class A mishaps to fatigue. Mishaps are categori

into five classes: A, B, C, D, and E. Class A is the most 

vere. The Naval Safety Center attributed 12.2 percent of 

class A mishaps between 1977 and 1990 to fatigue.7 T

Presidential Commission on the Space Shuttle Challen

Accident identified sleep loss as at least contributory 

senior managers’ poor decision making regarding launc

It is apparent from the historical data presented that 

tigue can have a negative impact for AEF operations if i

not correctly managed.

Causal versus Fatigue-related Factors. Author Jo

A. Caldwell claims that many of the human errors 

counting for more than one-half of all aviation accide

are probably the direct result of fatigue-related pilot in

tentiveness and failures to respond to critical informat

in the cockpit.9 Decreased performance related to sl

loss and circadian disruption has been implicated in so

major disasters, such as the Exxon Valdez, Three-M

Island, and Bhopal accidents.10 However, fatigue 

quently is not cited as a causal factor in air carrier a

dents despite evidence pointing to its role in misha

Examples of mishap-related “behavioral factors” listed 

the ASRS include “motivational and attitudinal problem

complacency, distraction, sensory illusions, and resou

utilization inadequacies,” all of which can result from 

crew sleepiness and fatigue.11 However, the first time t

the National Transportation Safety Board (NTSB) cited 

tigue as probable cause in an aviation accident was a

the DC-8 crash at Guatánamo Bay in 1993.12

Physiological Aspects of Sleep

Modern sleep research began in the mid-1950s with 

discovery of two distinct states of sleep. Over the past 

years, there has been extensive scientific research on sle

sleepiness, circadian rhythms, and the effects of these f

tors on waking alertness and performance.13 Following 

brief overview of some of the relevant scientific informat

regarding human sleep, fatigue, and circadian rhythms
Rapid Eye Movement versus

Nonrapid Eye Movement

Historically, sleep has been viewed as a condition wh

the human organism is turned off. Scientific findings h

clearly established that sleep is a “complex, active phy

ological state that is vital to human survival.”14 Contr

to popular belief, sleep is not a homogeneous state.15 

stead, sleep is composed of two distinct phases: nonra

eye movement (NREM) and rapid eye movement (RE

sleep. These two sleep states are significantly differ

from each other.

To begin with, NASA studies revealed that NREM sl

is divided into four stages, with the deepest sleep occurr

during stages three and four. There is usually very li

mental activity during these stages. During NREM sle

physiological and mental activities decelerate (e.g., he

rate and breathing rate slow and become regular). If aw

ened during this deep sleep, an individual may take so

time to wake up and then continue to feel groggy, slee

and perhaps disoriented for 10 to 15 minutes. This p

nomenon is called sleep inertia.16

Conversely, REM sleep is associated with an extrem

active brain that is dreaming and with bursts of rapid 

movements (probably following the activity of the drea

During REM sleep the major motor muscles of the body 

paralyzed. If awakened during REM sleep, individuals c

often provide detailed reports of their dreams.17

Sleep Cycle

Over the course of a typical night, NREM and REM sl

occur in a repetitive 90-minute cycle, with about 60 m

utes of NREM sleep followed by about 30 minutes of R

sleep. Figure 2 shows this cyclical pattern.

From the histogram it is important to make note t

most deep sleep (i.e., NREM stages three and four) occ

in the first third of the night, and REM periods are shor

early in the night and then become longer and occur m

regularly later in the sleep period. Overall about 25 perc

of sleep time is spent in REM sleep, and about 50 perc

is spent in NREM stage two.18
Circadian Rhythms

Over evolutionary time, the daily cycles in the phys

environment (produced by the earth’s rotation) have 

come hard-wired into our neuronal circuitry in the form 

a biological clock in the “suprachiasmatic nucleus of 

hypothalamus.”19 Circadian rhythms govern sleep 

wakefulness, motor activity, hormonal processes, b

temperature, performance, and many other factors.20 T

circadian (circa = about; dies = day) enforces an appro

mately 25-hour cycle in many functions. Unless timing 

formation is received from the environment, the hum

circadian clock tends to run slow to account for this 

hour cycle. The specific environmental time cues that s

chronize it to a 24-hour day are known by the Germ

term zeitgebers, meaning time-givers. Currently two ty

of zeitgebers have been identified: exposure to bright li

and social factors.21 Moving to a new light or dark sched

Source: M. R. Rosekind et al., NASA Technical Memorandum 1999-208780, sub

Crew Factors in Flight Operations X: Alertness Management in Flight Operat

Moffett Field, Calif., Ames Research Center, 1999.

Figure 2. Histogram of Normal Sleep
(e.g., night work or time zone change) can create inter

and external desynchronization.22

Scientific studies have revealed that—based upon 

cadian factors—there are two periods of maximal slee

ness during a normal 24-hour day. One occurs at ni

roughly between 0300 and 0500, with many functio

demonstrating reduced levels from 0000 to 0600.23 T

other occurs midday roughly between 1500 and 17

M. R. Rosekind and associates concluded that this aft

noon increase in sleepiness occurs whether a meal h

been eaten or not, though the meal may aggravate the u

derlying sleepiness.24

Effects of Sleep Debt

Sleep loss is common and can be acute or cumulat

In an acute situation, sleep loss can occur either totally 

as a partial loss. Total sleep loss involves a complet

missed sleep opportunity and continuous wakefulness 

about 24 hours or longer. Partial sleep loss occurs wh

sleep is obtained within a 24-hour period but in 

amount that is reduced from the physiologically requi

amount or habitual total.25 Sleep loss can also accumul

over time into what is often referred to as “sleep de

Sleep loss—whether acute or cumulative—results in s

nificantly degraded performance, alertness, and mood.

On average most humans physiologically require ab

eight hours of sleep per night.26 However, individual 

quirements vary, so long as the required amount equa

to “the amount of sleep necessary to achieve full alertn

and an effortless level of functioning during wak

hours.”27 Individual sleep needs vary, although m

adults require about eight hours as mentioned abo

Some people need six hours, but others require 10 ho

to feel wide-awake and to function at their peak level d

ing wakefulness.28 Unfortunately, as the data will illustr

later, individual efforts to assess their true level of slee

ness can sometimes be grossly inaccurate. An individ

who requires eight hours of sleep and obtains only 

hours on a particular night is essentially sleep deprived 

two hours. If that individual sleeps only six hours ea
night over four nights, then the two hours of sleep loss 

night would accumulate into an eight-hour sleep debt.2

Estimates suggest that in the United States today, ma

adults obtain one to 1.5 hours less sleep per night th

they actually need.30 During a regular workweek t

would translate into the accumulation of a five to se

and one-half hours of sleep debt going into the weeken

hence, the common phenomenon of sleeping late on we

ends to compensate for the sleep debt accumulated dur

the week. Sleep loss also can result in some extension 

the usual sleep duration. However, this extension is mu

less than would be required to “make up” the lost hour

sleep. Both an increased amount of deep sleep and 

creased sleep duration can indicate a sleep debt.31 A

sleep loss, recovery is not accomplished through an ho

for-hour restitution. Rather, recovery is accomplish

through an increase in deep sleep (NREM slow-wave sle

starting on the first night of regular sleep. Typically, 

nights of recovery sleep are needed to return to a norm

baseline of waking performance and alertness.32

Physiological Aspects of Fatigue

The term fatigue has been used to describe many dif

ent experiences: sleepiness, physical tiredness, inability 

focus mentally, and others. However, flying fatigue is 

fined as “a decrease in skilled performance related to 

ration or repetitive use of that skill, aggravated by phy

cal, physiological and psychic stress.”33 Table 1 illustra

common signs and symptoms of fatigue.

Table 1

Fatigue Signs and Symptoms

Forgetful Slowed Reaction Time

Poor Decisions Apathetic

Fixated Lethargic

Reduced Vigilance Bad Mood

Poor Communication Nodding Off

Source: M. R. Rosekind et al., “Managing Fatigue in Operational Settings I: Ph

logical Considerations and Countermeasures,” Behavioral Medicine 21, 1996.
Caldwell also described other indicators of insuffici

sleep. They include the following difficulties:

• awakening without the aid of an alarm clock;

• repeatedly pressing the snooze button when 

alarm sounds;

• feeling that a nap during the day is necessary to a

viate sleepiness;

• consistently looking forward to weekends or ot

times for the purpose of “catching up on sleep”; an

• frequently experiencing an inability to stay awake 

meetings, while watching television, or during ot

sedentary activities.34

The effects of fatigue that concern the operatio

community—specifically those that affect crewmem

alertness and performance—stem primarily from sl

loss, circadian rhythm disruption, and the interaction 

the two.35 Figure 3 shows the link between the variab

that result in fatigue.

Sleep Loss Circadian

Rhythms

Effect of flight

operations on sleep and

circadian physiology

FLIGHT

CREW

FATIGUE

Source: M. R. Rosekind et al., NASA Technical Memorandum 1999-208780, sub

Crew Factors in Flight Operations X: Alertness Management in Flight Operat

Moffett Field, Calif., Ames Research Center, 1999.

Figure 3. Causes of Fatigue
Effects on Performance

Unfortunately, individual aviators and their comma

ers often underestimate the impact of fatigue on perfor

ance. The biological limits imposed by fatigue will imp

the performance of even the most highly skilled and m

vated individuals, and the effects of fatigue cannot 

overcome by training or experience; one cannot train o

self to overcome the physiologic need for sleep. Nor c

the impact of fatigue be negated by monetary or other 

centives.36 In any event, restricting sleep to less than 

hours per day produces noticeable deteriorations in p

formance. Furthermore, remaining awake for prolon

periods can create difficulties in accomplishing even s

ple tasks. Caldwell revealed that just 17 hours of cont

uous wakefulness degrades aspects of performance to 

same extent as a blood alcohol concentration (BAC) 

0.05 percent, the proscribed level of alcohol intoxicat

in many countries. After 24 hours awake, performanc

reduced to the level of what would be observed with a B

of 0.10 percent.37 The performance of drowsy pilots 

comes less consistent, especially during the night hou

Sleepy pilots often fail to respond appropriately to cock

demands, and they are at serious risk for missing ta

related details. Problem solving, reasoning, and con

accuracy degrade. Overall the aviator’s ability to pay 

tention to flight instruments and to manage radio co

munications, crew coordination, and navigational task

severely impaired.38

Physiological versus Subjective Sleepiness

It is usually difficult for most individuals to reliably 

timate their own sleep or their waking alertness, especi

if they are already sleepy. Overall there is a tendency 

individuals to subjectively overestimate how long it ta

to fall asleep and underestimate total sleep time; peo

fall asleep faster and sleep longer than they think. So wh

an individual experiences a bad night of sleep, it may 

be as bad as it seemed. Nevertheless, the tendency is 

individuals to subjectively rate themselves as more a

than is indicated by physiological measures. That is, m

individuals are more likely to be sleepier than they rep
or experience.39 Data from an international study of fli

crews illustrated that the highest subjective rating of al

ness occurred at a time when physiologically the indiv

ual was falling asleep within six minutes (an indicator 

severe sleepiness).40

Jet Lag

Jet lag can be defined as “the condition where the cir

dian clock is out of step with the environment.”41 The Am

Research Center asserts that crossing time zones produ

an additional zeitgeber disruption regularly encounte

by flight crews. The circadian clock resynchronizes o

gradually to a new environmental time. Circadian rhyth

in different bodily functions—such as hormone secretio

basal temperature, and blood pressure—adjust more 

less quickly, depending on the tightness of their pairing 

the clock and on their interactions with other physiolog

functions, with each adapting at its own rate. Thus, a

a transmeridian flight, not only is the circadian clock 

of step with the local zeitgebers but also different phys

logical functions are out of step with one another.42 T

typical guidance given is to provide a 24-hour recovery 

riod for each time zone traveled. Frederick W. Rudge c

siders this to be a very conservative estimate. Instead, 

believes that six hours of recovery per time zone is a

quate.43 E. L. Co and associates point out several fact

that might affect an individual’s ability to adapt to a n

schedule:

• Individuals differ in their bodies’ ability to adapt 

schedule changes.

• The ability to adapt decreases with increasing age

• The direction of the shift affects the ability to ada

Westward travel is more natural to the circadian cl

and is, therefore, easier than eastward travel.

• The more time zones crossed, the longer the adap

tion takes.44

To help ensure that interruption in circadian rhyt

will not affect performance on trips to distant places, 

International Civil Aviation Organization (ICAO) has dev

oped the following travel time formula.45
Rest period in tenths of days = travel time (hours) 

vided by 2 + time zones in excess of 4 + departure ti

coefficient (local time) + arrival time coefficient (lo

time). The departure time coefficient (DTC) and arrival ti

coefficient (ATC) are given in the following table.

In applying the formula, the following rules are obser

by ICAO:

• The value obtained for rest periods, in tenths of da

is to be rounded to the nearest higher half-day. R

stops that add up to less than a day before round

will not be scheduled unless the journey involves 

overnight flight on mission travel.

• “Travel time, in hours” means the number of hour

elapsed time required for the journey, rounded of

the nearest hour.

• “Time zones” are computed in increments of 15 

grees of longitude from Greenwich, England.

• “Departure time” and “arrival times” are local time

Notes

1. William J. “Bill” Clinton, A National Security Strategy for a 

Century (Washington, D.C.: The White House, December 1999), 11.

Table 2

Departure and Arrival Time Coefficients

Period (hour) DTC ATC

0800–1159 0 4

1200–1759 1 2

1800–2159 3 0

2200–0059 4 1

0100–0800 3 3

Source: USAF, “Flight Surgeon Checklist,” draft for residency for aerospace med

course material, Brooks Air Force Base, Texas, March 2000, chap. 3.
2. Headquarters USAF/XOPE, EAF Implementation Division, A

space Expeditionary Forces, 1 October 1999.

3. F. Whitten Peters and Michael E. Ryan, US Air Force Posture St

ment 2000, 30–31.

4. M. R. Rosekind et al., “From Laboratory to Flightdeck: Promo

Operational Alertness,” Royal Aeronautical Society, 1997, 7.1–7.14.

5. M. R. Rosekind et al., “Fatigue in Operational Settings: Exam

from the Aviation Environment,” Human Factors, 1994, 36(2).

6. M. R. Rosekind et al., NASA Technical Memorandum 1999-208

subject: Crew Factors in Flight Operations X: Alertness Managemen

Flight Operations, Moffett Field, Calif.: Ames Research Center, 1999.

7. Carol S. Ramsey and Suzanne E. McGlohn, “Zolpidem as a Fat

Countermeasure,” Aviation, Space, and Environmental Medicine, Oct

1997, 926–31.

8. Rosekind et al., “From Laboratory to Flightdeck.”

9. John A. Caldwell, “Fatigue in the Aviation Environment: 

Overview of the Causes and Effects As Well As Recommended Coun

measures,” Aviation, Space, and Environmental Medicine, October 1

932–38.

10. M. R. Rosekind et al., “Fatigue in Operational Settings.”

11. Caldwell.

12. Rosekind et al., NASA Technical Memorandum 1999-208780

13. M. R. Rosekind et al., “Managing Fatigue in Operational Sett

I: Physiological Considerations and Countermeasures,” Behavioral M

cine 21, 1996, 157–65.

14. Ibid.

15. E. L. Co et al., “Fatigue Countermeasures: Alertness Managem

in Flight Operations, Proceedings of the 11th Annual International Airc

Cabin Safety Symposium, Long Beach, Calif., 1994.

16. Rosekind et al., NASA Technical Memorandum 1999-208780

17. Ibid.

18. Ibid.

19. Ibid.

20. Rosekind et al., “Fatigue in Operational Settings.”

21. Rosekind et al., NASA Technical Memorandum 1999-208780

22. Rosekind et al., “From Laboratory to Flightdeck.”

23. Rosekind et al., NASA Technical Memorandum 1999-208780

24. Rosekind et al., “From Laboratory to Flightdeck.”

25. Ibid.

26. Ibid.

27. Rosekind et al., “Managing Fatigue in Operational Settings I.

28. Ibid.

29. Ibid.

30. Ibid.

31. Ibid.

32. Rosekind et al., “From Laboratory to Flightdeck.”

33. USAF, “Flight Surgeon Checklist,” draft for residency in aerosp

medicine course material, Brooks Air Force Base, Tex., March 20

63–67.
34. John A. Caldwell, “Sleepiness in the Cockpit,” Combat Edge, 

gust 1999.

35. Co et al.

36. Caldwell, “Fatigue in the Aviation Environment,” 932–38.

37. Caldwell, “Sleepiness in the Cockpit.”

38. Ibid.

39. Rosekind et al., NASA Technical Memorandum 1999-208780

40. Rosekind et al., “From Laboratory to Flightdeck.”

41. Rosekind et al., NASA Technical Memorandum 1999-208780

42. Ibid.

43. Frederick W. Rudge, “Operational Considerations,” USAF F

Surgeon’s Guide, chap. 14.

44. Co et al.

45. “Flight Surgeon Checklist.”

46. Ibid.

PART III

Issue Analysis

Current Fatigue Countermeasures

Sleep, rest of nature, O sleep, most gentle of the divinities,

peace of the soul, thou at whose presence of care disappears,

who soothest hearts wearied with daily employments, and

makest them strong again for labour!

––Ovid (43 B.C.–A.D. 18)

Ovid’s insight into the importance of sleep helps str

the significance sleep has on performance. Consequen

alertness management strategies must be developed wh

the environment or setting precludes a good night’s re

such as those often found on AEF deployments. Alertn

management strategies can “minimize the adverse effe

of sleep loss and circadian disruption and promote o

mal alertness and performance in operational setting

The application of “strategic countermeasures” invol

three components:

• Understanding the physiological principles related 

sleep and circadian rhythms.

• Determining the specific alertness and performa

requirements of a given operation.

• Taking deliberate actions to apply the physiolog

principles to meet the operational requirements.2

Alertness Management Strategies

Rosekind has differentiated alertness managem

strategies into two components: preventive strategies a

operational strategies. Preventive strategies are used pr

to duty or on layover to minimize the adverse effects of 

underlying physiological factors (i.e., sleep loss and cir

dian disruption). These strategies include obtaining ma

mal quantity and quality of sleep prior to duty, schedul

sleep periods during layover, accounting for fatigue fact

during trip scheduling, napping, maintaining good sl

habits, exercising, maintaining balanced nutrition, a

others.3 Preventive strategies address the major physiol

ical causes of fatigue in flight operations, namely sleep l

and circadian rhythm disruption. Sleep loss, whatever 

origins, has detrimental effects on performance. Circad

23
rhythm disruption is an inevitable consequence of prov

ing around-the-clock services and of transmeridian flig

P. H. Gander and associates propose that it can comp

mise cockpit performance in two ways. First, it may 

quire crew members to be on duty during the part of 

circadian cycle when their performance capacity and al

ness are lowest. Second, it might displace crew memb

sleep to parts of the circadian cycle when sleep quan

and quality, and therefore subsequent waking functi

are compromised.4

Operational countermeasures are used in flight to ma

tain alertness and performance during operations. Gen

ally, these strategies may be more short acting and se

to mask or conceal underlying physiological sleepine

These countermeasures include physical activity, strate

caffeine use, and social interactions.5 In general, ope

tional countermeasures do not address the underly

physiological causes of fatigue. Instead, Rosekind poi

out that they are meant to enhance alertness and p

formance temporarily so that operational safety and e

ciency are maintained.6

Both types of alertness management strategies used 

counter the effects of fatigue can be organized into ph

maceutical and nonpharmaceutical means. Some stra

gies, such as the consumption of caffeine, can be cate

rized in both types depending upon the time 

administration.

Pharmaceutical

To enhance performance in a smaller and aging milita

the National Research Council and others have sugges

that “greater consideration be given to the use of pharm

ceuticals during extended flight missions and sustain

operations.”7 K. M. Belland and C. Bissell found that d

ing Operations Desert Shield and Desert Storm the US

used performance maintenance medications (amphe

mines and temazepam), and these medications showed 

adverse effects and helped to maintain performance lev

during flight operations.8 Additionally, they noted that 

Air Force stimulant and sedative protocols emphasi

prudent planning and recognition of human performa
parameters, as well as the necessity for flight surgeons 

closely monitor the physiologic and psychologic status 

aircrew personnel.9 When operational constraints prev

the use of behavioral strategies for the alleviation of 

crew fatigue, pharmacological countermeasures may 

the only option for maintaining aviator performance. 

Force Instruction (AFI) 48-123, Medical Examination a

Medical Standards, 1 January 2000, is the primary sou

for the rules regarding medications that can be waive

for flying duties. As a general rule, the use of medicati

will usually require approval by the appropriate waiver 

thority. Waiver action for any medication cannot be c

sidered until “control of the condition has been dem

strated and the absence of side effects has be

determined and documented.”10 Table 3 gives a summ

of three typical medications and their associated effects

Restoril. Temazepam (Restoril) was, until recently, 

only hypnotic approved by the USAF for aircrew use. A 

hour grounding period following administration is requi

due to its long elimination half-life of 8.4 +/- 0.6 hours. 

the number of continuous hours awake contributes sig

icantly to a decrease in alertness, if Restoril is used for p

mission or in-flight napping, theoretically it could wor

fatigue toward the end of a mission. Carol S. Ramsey a

Suzanne E. McGlohn reported that the drug causes p

sistent drowsiness in some individuals.11

Dexedrine. Recent studies indicate that dextroamph

amine (Dexedrine) has been effective in aviation contex

EF-111A Raven jet crews administered five milligrams (m

of Dexedrine during an Air Force strike on Libya in A

1986 experienced positive effects in terms of overcom

the fatigue of the mission itself and the sleep deprivat

which occurred during mission preparations.12 Air Fo

pilots effectively used dextroamphetamine during Ope

tion Desert Storm to maintain acceptable performa

during continuous and sustained missions. The medi

tion was found to be beneficial in terms of overcoming 

tigue without producing unwanted side effects.13 In 

study the beneficial effects of Dexedrine were particula

apparent from early morning until noon after a night 

sleep loss, although drug-related performance enhan

ments were seen later as well.14 A major finding was t
Zolpidem Triazolam Temazepam (Ambien) (Halcion) (Restoril) Usual dose 10 mg 0.25 mg 15 mg Peak effect 1.6 h 2 h 1.5 h Avg. elimination half life 2.6 h 3.1 h 8.4 h Active metabolites No No No Impact on sleep Slight absolute increase Increased Stage 2, Increased Stage 2, architecture in Stage 4 (NREM) Reduced Stage Reduced Stage 3–4, 3–4, Reduced REM Reduced REM Rebound insomnia No Yes +/–

Anterograde amnesia No Yes YesPersisting AM drowsiness No +/– Yes (Drug accumulation

(hangover) after 3 doses)Tachyphylaxis No High (>7–10 d) ModerateAcute withdrawal effects No Yes (Similar to alcohol and Yes (Similar to alcohol and

phenobarbital) phenobarbital)

Drug interactions Phenothiazines Alcohol Alcohol

Haliperidol Oral Contraceptives Oral ContraceptivesSSRI's (?) Ciprofloxin Ciprofloxin

Erythromicin ErythromicinINHOmeprazol INHCimetidine Omeprazol

Cimetidine

Use in Pregnancy Category B (Maturation defects in Category X (Teratogenic in Category X (Teratogenic in

 animal studies at high doses first trimester) first trimester)

Table 3

Comparative Profiles of Zolpidem, Triazolam, and Temazepam
Dexedrine was valuable when given prophylactically to 

lots for the prevention of performance decrements asso

ated with sleep deprivation.15

Zolpidem. Ramsey and McGlohn confirmed that Zo

dem appears to be a preferable agent to benzodiazepi

for use in aviators because it is relatively free from deb

tating side effects and does not cause tolerance or prom

drug dependence. It preserves normal sleep architect

and shows promise in providing restorative sleep in sit

tions not normally conducive to sleep: troop transp

napping during extended missions, permission or pres

napping, and crew rest during circadian “forbidden p

ods.”16 Acute and chronically fatigued individuals m

gain a strategic advantage if they are able to obtain ph

maceutically aided restorative sleep.

Caffeine. Caffeine—present in coffee, cola drinks, a

chocolate—is considered to be habituating at a level of 

mg/kilograms per day. Since one eight-ounce cup of co

contains approximately 100 mg of caffeine, somewhere 

tween six to 10 cups of coffee per day would produce t

level.17 Caffeine is also known to sustain overnight p

formance and improve performance during the day a

has been used in air operations. However, it may distu

recovery sleep, and there is some evidence that it may 

pair performance at higher doses. Caffeine stimulates 

central nervous system (CNS), generally effective in 15 

45 minutes after ingestion. It usually remains active 

three to five hours, although the effects can continue 

up to 10 hours in sensitive individuals.18 In addition, A

thony N. Nicholson and Claire Turner advise that caffe

may increase feelings of nervousness and tension; a

there may be considerable individual differences in the 

fects of the drug, often depending on levels of dietary 

take.19 Regardless of the level of habitual consumpti

caffeine before sleep leads to lighter sleep with more aw

enings and reduced total sleep time. Some conserva

recommendations suggest no caffeine consumption 

much as six hours before bedtime.20 Although caffeine h

been cleared of an association with initial myocardial 

farcts, Rudge stresses that its stimulant effects on the C

are of concern. During a temporary withdrawal from c

feine, as might occur during a deployment, the result
restlessness and disturbed sleep could add unnecess

burdens to an already fatigued crew. Caffeine is a kno

diuretic, and it can sensitize the heart to the developm

of irregular heartbeats. Neither of these side effects is 

sirable, particularly in pilots of high-performance 

craft.21 Caldwell adds that caffeine should not be c

sumed throughout the duty period, but rather wh

drowsiness becomes apparent.22

Nicotine. Nicotine has much the same effects as c

feine on nocturnal sleep and subsequent daytime slee

ness and performance. Like caffeine, nicotine consum

tion (either tobacco smoking or patch) should not oc

within several hours prior to the desired onset of sleep

Nonpharmaceutical

Four nonpharmaceuticals that may affect sleep or al

ness are noted in this research paper. There is consid

able interest in minimizing sleep loss, crew rest guidelin

environment, and exercise and diet—all of which may 

fect the circadian cycle.

Minimizing Sleep Loss. There is no substitute fo

good night of sleep. Caldwell maintains that the most 

fective strategy for minimizing fatigue on the job is for 

crew members to obtain adequate sleep prior to the d

period.24 On working days, it is desirable to get at least 

many hours of sleep as a normal night of sleep on a n

working day. If the work schedule requires wakefuln

during the part of the circadian cycle normally p

grammed for sleep, it may not be possible to obtain 

usual daily quota of sleep in a single episode.25

At certain times in the circadian cycle, it is easy to 

asleep; and at other times, the brain is programmed to 

awake. For this reason, it is important to take advant

of feeling sleepy by sleeping if circumstances permit. C

versely, it is impossible to force sleep! Trying unsucce

fully for 15 to 30 minutes to fall asleep is a signal to ab

don the effort for the time being and to get out of bed.2

Crew Rest Guidelines. Adequate crew rest is norm

seven to eight hours of uninterrupted sleep, which utili

the sleep hygiene principles. It is important to distingu

between the officially designated crew rest times and 
actual amount of sleep the crew gets.27 AFI 11-202V

General Flight Rules, discusses crew rest and flight d

limitations. Air Force aircrews require at least eight ho

of continuous, uninterrupted rest during the 12 hours 

mediately prior to the beginning of the flight duty perio

If an aircrew member remains after flying to perform o

cial duties, the crew rest period begins after termination 

these duties. The flight duty period is defined as “a per

that starts when an aircrew reports for a mission, briefi

or other official duty and ends when engines are s

down at the end of a mission, mission leg, or a series 

missions.”29 The minimum crew rest period is 12 hou

and when only one pilot is aboard, the maximum fli

duty period is also 12 hours.30 The duty period drops to 

hours at night for single-seat aircraft.31

Environment. Physical aspects of the environment 

also affect sleep. A dark, quiet room is preferable. Eyesha

are a simple and portable solution to the problem of lig

Unless it is necessary to be available to be awaken

earplugs can also be helpful to reduce noise. Sudd

sounds can disturb sleep, so providing continuous ba

ground “white” noise can be helpful. One suggestion fr

flight crews is to set the radio between two stations for t

purpose. In general, sleep quality is better if the envir

ment is cooler rather than hotter. A comfortable sleep s

face is also important.32 Aviators should make every effor

make the environment as comfortable as possible. Moreo

Caldwell recommends carrying a family picture, one’s o

pillow, or some other small, familiar object on deploymen

make the new environment more familiar and relaxing.3

Exercise and Diet. Exercise has been demonstrated 

facilitate circadian adaptation in animals, though th

has not yet been a demonstration in humans.34 In labo

tory studies with rodents, an exercise bout in the morn

advances the circadian clock, whereas an exercise bou

the evening delays it.35 The discomfort associated w

being hungry, or with having eaten too much, may int

fere with falling asleep. If one is hungry or thirsty at b

time, a light snack or a small drink is preferable.36 Th

is also considerable interest in possible dietary c

stituents that might be able to promote sleep or alertne
or to reset the circadian clock. It has been suggested t

foods rich in carbohydrates (e.g., legumes, pastas, po

toes) may induce sleep by elevating serotonin levels. C

versely, foods high in protein (e.g., meats, dairy produ

eggs) and certain amino acids are proposed to prom

wakefulness by enhancing catecholamine activity.37

Depending upon where the AEF is deployed, alco

consumption might be an issue of concern. Alcohol is 

putedly the most commonly used sleep aid in the Uni

States.38 It can promote relaxation and thereby help a p

son to fall asleep; but it also produces easily disrupt

lighter sleep. It suppresses REM sleep in the first hal

the night, leading to REM rebound and withdrawal effe

in the second half.39 It is advisable to finish drinking s

ficiently early to allow the blood alcohol level to return 

zero before sleep. Even then, “sympathetic arousal follo

the decline of blood alcohol levels, and may persist for 

to three hours after the blood alcohol concentration 

turns to zero.”40

Future Fatigue Countermeasures

There is considerable interest in chronobiotics—that 

“drugs, hormones (e.g., melatonin) and other treatme

(e.g., bright light) that are potentially capable of acceler

ing the adaptation of the circadian clock to a n

duty/rest schedule or time zone.”41 However, there ar

number of practical considerations that Gander and as

ciates expose that—for the moment—limit the poten

usefulness of chronobiotics for flight crews. The time in 

cycle at which a chronobiotic is administered is criti

and opposite effects can be achieved by displacing the d

by several hours. Chronobiotics used in everyday life m

act against a background of all the other environmen

time cues to which an individual is exposed. While th

are ways of minimizing these extraneous cues (e.g., we

ing dark glasses to reduce the effects of sunlight or m

mizing contact with the local social environment), cr

member acceptance of and compliance with fatigue cou

termeasures that require such discipline is a real issue. 

nally, none of the chronobiotics currently being conside
has been shown to be effective in field tests in any aviat

environment.42

Pharmaceutical

The following drugs—melatonin, tyrosine, and pemolin

deserve a word of caution concerning their availabil

Many medications available by prescription in the Uni

States can be obtained over the counter, without prescr

tion, in many overseas locations and in some cases at y

local drug store. Presently, none of these medications h

been approved for use by aircrews. The information p

vided here is intended only to give a basic understand

of their effects.

Melatonin. Melatonin is a hormone produced in 

pineal gland. Bright light suppresses melatonin secreti

while darkness causes the pineal gland to release me

tonin, causing drowsiness. Unfortunately, as Susan 

Northrup points out, when more than three time zones 

crossed, the cycle continues with the body clock—which 

the primary regulator of melatonin, not the local ti

zone.43 However, the proper use of melatonin tablets m

not only resolve sleeping problems (sedative effects) afte

long flight but can also actually speed up the resynch

nization of the body clock to a new time zone.44

Tyrosine. Tyrosine is a large, neutral amino acid fou

in dietary protein. It has recently been considered as a 

tential countermeasure to stress in humans. David F. N

observed decreases in psychomotor performance, v

lance, and auditory attention, and increases in react

times and response lapses in sleep-deprivation stud

However, with the administration of tyrosine, significan

smaller performance lapses were observed. Consequen

he concluded that this relatively benign substance mi

prove useful in countering performance decrements d

ing episodes of sustained, stressful work coupled w

sleep loss.45

Pemoline. Pemoline—a dopamimetic drug that acts 

a stimulant—has the potential to improve alertness a

performance in well-rested and sleep-deprived subjec

and its stimulant activity does not appear to be depe

ent on the time of day or the duration of prior wake
ness. It is relatively free of adverse effects on recov

sleep and of dependence.46

Nonpharmaceutical

The following nonpharmaceutical strategies are bri

discussed to provide a basic understanding of their cir

dian adaptation.

Bright Lights. Bright light has been shown in labo

tory studies to facilitate rapid circadian adaptation. Two 

three hours of bright light (i.e., 2,500–10,000 lux) adm

istered at the appropriate phase of the temperature cy

for three successive days may facilitate an eight- to 

hour shift of the circadian clock. Separate from its effe

on the circadian clock, bright light may also have an in

pendent alerting effect.47 As stated earlier, in addition to 

capacity to reset the circadian clock, light of this intens

suppresses secretion of the pineal hormone, melaton

and appears to have an alerting effect—although 

mechanism of this is not clear.48

Strategic Naps. Generally, studies have demonstra

that naps maintain performance compared to basel

conditions or improve performance compared to con

tions of prolonged wakefulness without naps.49 A nap 

duces the length of continuous wakefulness before a w

period and can be especially beneficial before a period 

night work, when the challenge of working through the 

cadian low point is also a factor.50 Caldwell discusses 

factors that affect the advantage of napping.

• The feasibility of creating a suitable nap environm

which is close to the workplace.

• The appropriate placement of the nap in the 24-h

period—during the nighttime period that normally 

incides with sleep.

• The appropriate placement of the nap relative to 

sleep deprivation period—prior to anticipated sl

deprivation.

• The length of time which should be allowed between 

end of the nap and the beginning of the next work ta

• The appropriate nap duration so as to maintain or 

cover performance during periods of continuo

wakefulness.51
Current perspectives on napping suggest that 

minute naps (short nap) or naps of about three to f

hours (long nap) are much more restorative than naps 

any other lengths of time. These two strategies, the sh

nap and the long nap, are designed to miss the singly s

wave sleep period associated with stages three and f

sleep.52 The napping strategies are designed to provide 

adequate rest while dramatically shortening the time 

takes for someone who was asleep to reach useful c

sciousness. Sleep inertia is shorter after REM, perhaps 

short as a minute or two.53

Rosekind suggests that naps can be a useful strategy 

both a preventive and an operational manner. As a p

ventive strategy, naps can be used as a protective meas

to maintain alertness and performance during a sub

quent period of prolonged wakefulness. A nap can also 

used to reduce the hours of continuous wakefulness bef

a shift or duty period and the total hours awake at the e

of the subsequent work period. As an operational strate

naps can be used to interrupt sustained periods of wa

fulness during a continuous operation to maintain 

level of subsequent performance and alertness.54

In addition to the two strategies, Rosekind identified 

major domains that should be addressed in an integra

program to manage fatigue in operational settings: edu

tion and training, hours of service, scheduling practic

countermeasures, design and technology, and research

Education and Training. Development and implem

tation of education and training materials will establish 

knowledge base for all other activities. Rosekind sugge

that the materials should provide information on the ph

iological mechanisms that underlie fatigue, address som

the misconceptions about fatigue, and make specific r

ommendations for countermeasures.56 In 1994 NASA Am

Research Center’s Fatigue Countermeasures Program, 

collaboration with the Federal Aviation Administrat

(FAA), developed an education and training module tit

Alertness Management in Flight Operations. The modul

distributed to the aviation industry through two-day wo

shops held at the NASA Ames Research Center.57

Hours of Service. The number of hours that indivi

als work can be regulated. Rosekind also recommends t
the specific guidelines include approaches that maint

operational flexibility. Whenever possible, these guideli

should rely on scientific data balanced with the ope

tional demands of the units.58

Scheduling Practices. Whenever possible, schedul

approaches should attempt to incorporate scientific 

search on fatigue. Some European approaches involve 

tating shift schedules over a matter of days (i.e., fast ro

tion) compared to the usual US practice of rotating s

schedules over weeks (i.e., slow rotation). The Europe

approach is based on data suggesting that shift workers 

not adjust to a rotated schedule and therefore sho

spend minimal time rotating their schedule.59 Person

who transition to a new time zone or work schedule 

only brief periods should not attempt to readjust their 

cadian rhythms but should try to remain on their origi

meal and activity or rest schedules as much as possibl

Countermeasures. There are a wide range of strateg

available that include personal, unit, and regulat

means. The specific strategies are discussed in other s

tions of this paper. However, Rosekind emphasizes that 

dividuals have a personal responsibility to incorpor

these strategies into their own lives.61

Design and Technology. Although technology in 

military continues to evolve with great speed, the hum

operators in the center of the advancing technology h

not evolved at all in their need for sleep and circadian s

bility. Potential technological areas include scheduling 

gorithms and alertness monitoring/management system

One example of using technology to address fatigue iss

is in an alertness warning system that Boeing has 

cluded as an option on its 747 and 767 aircraft. This s

tem alerts the flight crew when no interaction with 

flight-deck computers has occurred during a certain p

grammable time period.62

Research. Although a tremendous amount of scient

information is now available on fatigue, sleep, and circad

physiology, much is still unknown. This is especially true 

the application of this scientific knowledge to operational 

sues. More research will be required to identify and gen

ate data that address specific operational issues, such 

regulatory, scheduling, and countermeasure questions.6
Notes

1. M. R. Rosekind et al., “Alertness Management: Strategic Nap

Operational Settings,” Journal of the Sleep Research Society 4, 62–66

2. Ibid.

3. M. R. Rosekind et al., “Alert Management in Long-Haul Flight 

erations,” Proceedings of the 39th Annual Corporate Aviation Safety S

nar, Flight Safety Foundation, St. Louis, Mo., 1994.

4. Philippa H. Gander, Mark R. Rosekind, and Kevin B. Greg

“Flight Crew Fatigue VI: A Synthesis,” Aviation, Space, and Environme

Medicine, September 1998, B49–B60.

5. Rosekind et al., “Alert Management in Long-Haul Flight Operatio

6. M. R. Rosekind et al., “Managing Fatigue in Operational Settin

Physiological Considerations and Countermeasures,” Behavioral Medi

21, 1996.

7. Carol S. Ramsey and Suzanne E. McGlohn, “Zolpidem as a Fat

Countermeasure,” Aviation, Space, and Environmental Medicine, Oct

1997, 926–31.

8. K. M. Belland and C. Bissell, “A Subjective Study of Fatigue du

Navy Flight Operations over Southern Iraq: Operation Southern Wat

Aviation, Space, and Environmental Medicine, June 1994, 557–61.

9. Ibid.

10. Frederick W. Rudge, “Drugs and the Flier,” USAF Flight Surge

Guide, chap. 13.

11. Ramsey and McGlohn.

12. John A. Caldwell et al., “Sustaining Helicopter Pilot Performa

with Dexedrine during Periods of Sleep Deprivation,” Aviation, Space, 

Environmental Medicine, October 1995, 930–37.

13. Ibid.

14. Ibid.

15. Ibid.

16. Ramsey and McGlohn.

17. Rudge.

18. Rosekind et al., “Managing Fatigue in Operational Settings I.

19. Anthony N. Nicholson and Claire Turner, “Intensive and S

tained Air Operations: Potential Use of the Stimulant, Pemoline,” Avia

Space, and Environmental Medicine, July 1998, 647–55.

20. Rosekind et al., “Managing Fatigue in Operational Settings I.

21. Rudge.

22. John A. Caldwell, “Fatigue in the Aviation Environment: 

Overview of the Causes and Effects As Well As Recommended Coun

measures,” Aviation, Space, and Environmental Medicine, October 1

932–38.

23. Rosekind et al., “Managing Fatigue in Operational Settings I.

24. Caldwell, “Fatigue in the Aviation Environment.”

25. Rosekind et al., “Managing Fatigue in Operational Settings I.

26. Ibid.

27. Frederick W. Rudge, “Operational Considerations,” USAF F

Surgeon’s Guide, chap. 14.
28. Air Force Instruction (AFI) 11-202, General Flight Rules, vo

June 1998, 42–45.

29. Ibid.

30. Ibid.

31. Ibid.

32. Rosekind et al., “Managing Fatigue in Operational Settings I.

33. Caldwell, “Fatigue in the Aviation Environment.”

34. Rosekind et al., NASA Technical Memorandum 1999-208

subject: Crew Factors in Flight Operations X: Alertness Managemen

Flight Operations, Ames Research Center, Moffett Field, Calif., 1999.

35. Rosekind et al., “Managing Fatigue in Operational Settings I.

36. Ibid.

37. Ibid.

38. Ibid.

39. Ibid.

40. Ibid.

41. Gander, Rosekind, and Gregory.

42. Ibid.

43. Susan E. Northrup, “Melatonin and Aircrew,” Safetyliner ’96, 

7, issue 2, 16.

44. Ibid.

45. David F. Neri et al., “The Effects of Tyrosine on Cognitive Per

mance During Extended Wakefulness,” Aviation, Space, and Environm

tal Medicine, April 1995, 313–19.

46. Nicholson and Turner.

47. Rosekind et al., NASA Technical Memorandum 1999-208780

48. Rosekind et al., “Managing Fatigue in Operational Settings I.

49. Rosekind et al., “Alertness Management.”

50. Rosekind et al., “Managing Fatigue in Operational Settings I.

51. Caldwell, “Fatigue in the Aviation Environment.”

52. V. A. Convertino et al., “Health, Fitness, and Nutrition,” U

Flight Surgeon’s Guide, chap. 14.

53. Ibid.

54. Rosekind et al., “Alertness Management.”

55. M. R. Rosekind et al., “Managing Fatigue in Operational Sett

II: An Integrated Approach,” Behavioral Medicine 21, 1996, 166–70.

56. Ibid.

57. Ibid.

58. Ibid.

59. Ibid.

60. Caldwell, “Fatigue in the Aviation Environment.”

61. Rosekind et al., “Managing Fatigue in Operational Settings 

166–70.

62. Ibid.

63. Ibid.
PART IV

Conclusions and Recommendation

Conclusions and Recommendations

My mind clicks on and off . . . I try letting one eyelid close at a

time while I prop the other open with my will. But the effort’s

too much. Sleep is winning. My whole body argues dully that

nothing, nothing life can attain, is quite so desirable as sleep.

My mind is losing resolution and control.

––Charles A. Lindbergh

––Spirit of St. Louis

Global demand for AEF presence continues to outp

our military’s resources. Therefore, the safety and ope

tional issues of managing fatigue will remain, and pot

tially worsen, with increasing demand. Attempts to de

minimize, or distract fatigue as a dangerous operatio

issue will only delay effective action while the associa

risk continues or increases. Other transportation mo

have fully acknowledged fatigue as a safety issue that 

serves attention and creative management solution

Clearly no single “cure” or magic bullet can eliminate 

tigue from 24-hour operational settings. Operational 

mands, human physiology, and individual differences 

too complex for a simple mechanistic approach. By exa

ining each component of the system, however, one c

identify areas in which to incorporate current scient

knowledge regarding fatigue. It will be critical to deve

and use approaches to maintain operational flexibility 

meet 24-hour global requirements. The challenge is to 

corporate fatigue-related knowledge while balancing 

need to meet operational demands. As long as around-t

clock operations are required to maintain military comm

ments, the effects of sleep loss and circadian disrupt

must be considerations in any operational setting. H

these factors affect the physiological and performance 

pabilities of the human operator will be critical to 

safety, performance, and productivity.2

Kelly J. Neville and associates advise that adequ

training about the impact of fatigue and sleep loss on saf

and effectiveness—and the fact that fatigue cannot be ov

come through willpower or motivation—should be provid

to every aircrew member.3 This training—combined w

knowledge of effective strategies for avoiding fatig

through proper sleep management and attention to cir

39
dian factors—should enable aviators and their comma

ers to maintain safe and effective air operations even in 

ficult circumstances. Literature suggests schedules co

be adjusted to be more compatible with circadian rhyth

and special circumstances. Layover periods for transp

aircrews must coincide with periods of peak sleepin

(early morning and midafternoon), and peak worklo

should coincide with periods of maximal alertness.4

The predominant cause of chronic sleep difficulties 

otherwise healthy individuals is poor sleep hygiene. Pil

can substantially improve daytime alertness by adher

to a proper sleep routine each night. This sequence 

cludes going to bed every night at a consistent time, avo

ing caffeine and alcohol prior to bedtime, establishin

healthy exercise routine, and avoiding mental associati

that are inconsistent with initiating and maintain

sleep.5 The USAF Flight Surgeon’s Guide offers seve

techniques for improving sleep hygiene.6

• Get rid of sleep debt (allow eight to 10 hours of sl

for a few days before a long mission or period of nig

time vigilance).

• Avoid excessive alcohol (a blood alcohol of more th

the legal limit before you go to bed can cause p

found insomnia; drink water before bed but not 

much that you will have to get up later to urinate)

• Avoid large meals before you go to bed (leave ab

six hours before sleep for digestion).

• Sleep as comfortably as possible in a quiet and 

dark as possible environment.

• Don’t prop the pillows up too high if you sleep on y

back as this can block the airways when REM aton

the lack of muscular tension, occurs.

• Personal hygiene helps sleep. Brush your teeth a

shower and dress comfortably for sleep and a

awakening.

• Avoid caffeinated beverages three to four hours bef

bed. You might not think that it hurts your sleep, 

it will cause a restless sleep.

• Use short nap (<30 minutes) or long nap (three to f

hours) strategies.
• Avoid strenuous exercise about three to four ho

before bed.

• Get to bed at the same time each night as closely 

possible.

• Consistency in sleep habits (time, procedures) is v

important to maintaining biological cyclicity.

• Try deep breathing and muscle relaxation techniq

to help with stress reduction and sleep onset.

Rosekind and associates identify four core operatio

issues where scientific data are available to support p

cies.7 The first issue involves the fact that the “crit

foundation for optimal performance and alertness dur

operations is established by an appropriate quantity a

quality of sleep prior to duty.”8 Are there individual dif

ences and can individuals in certain circumstances op

ate on less than eight hours of sleep? The answer to b

questions is yes. However, policies should address aver

requirements and not rely on the “extra” effort required 

cope with sleep loss in nominal operations. As previou

addressed, reported and habitual sleep amounts are 

necessarily indicators of an individual’s actual sleep ne

Therefore, one core operational issue is establishing a m

imum rest that provides for an eight-hour sleep oppor

nity every 24 hours.9

The second issue involves the length of continuo

wakefulness. Complementary to an appropriate minim

rest is the length of continuous wakefulness, tradition

identified as the duty period. Data from NTSB aircraft 

cident investigations indicate an increased risk exists 

yond the 12-hour duty period. Analysis of a national oc

pational-injury database showed a constant accident 

injury rate through nine consecutive hours of work a

then a progressive increase to three times the rate at 

hours of work.10

The third issue addresses circadian factors or time 

day. This powerful modulator of human performance a

alertness affects three aviation operations: night flyi

time zone changes, and day and night duty shifts. The 

cadian trough (0300 to 0500) and night in general (00

to 0600) are associated with significant degradation 

performance and alertness and increases in errors a
accidents.11 Therefore, the time of day that an operat

occurs should be a consideration. The stability of perfor

ance during a 14-hour daytime duty period is not the sa

as during a 14-hour nighttime duty period.

The fourth issue includes minimizing the cumulative 

fects of fatigue. It is important to maintain an optimal sl

opportunity every 24 hours and also to address the pot

tial for cumulative effects. Therefore, appropriate recov

time should be allowed per week (days or rolling hours

When the author was deployed in support of an operat

that flew seven days a week, the commander made s

that supervisors gave their personnel a day off every 

weeks. While the intent can be commended, it still f

short of nullifying the cumulative effects of fatigue.

While flight, duty, and rest policies are one necess

component of addressing fatigue in aviation operatio

they are not sufficient. The operational environment 

complex and diverse and thus precludes a single and s

ple solution to managing fatigue. An integrated, multico

ponent approach to managing fatigue in aviation ope

tions offers more comprehensive improvements a

potential flexibility.

Literature strongly suggests that the following factors 

considered before implementing naps or other alertn

management strategies in real-world operational settin

• An identifiable benefit: An alertness managem

strategy should provide a clear and identifiable be

fit to the aviator and the operational environm

(e.g., increased safety margin). It should minim

some adverse consequences or promote a particu

positive outcome.

• Opportunity: An appropriate opportunity for imp

mentation should be identified. In some operatio

circumstances it may not be appropriate to consi

a certain strategy (e.g., napping during a flight i

single-seat fighter).

• Unit climate/culture: Some strategies may be exp

itly or implicitly supported, while others are activ

suppressed.
• Operational demands: The specific work deman

and circumstances of a particular work environm

may exclude some potential strategies.

• Safeguards: Alertness management strategies are 

tended to promote safety and productivity. Spec

safeguards should be employed to ensure that stra

gies do not negatively affect the safety margin.13

In the preceding sections the latest scientific data w

presented to aid commanders and aviators in combat

the fatigue anticipated and associated with AEF depl

ments, as well as while employing under stressful, un

miliar circumstances. However, there is more informat

that needs to be addressed. The author, having been op

ational for more than 12 years, is fully aware of the “r

world” issues concerning fatigue. The reality of the sit

tion is that fatigue and its negative consequences are

general, downplayed at best and completely ignored in 

treme circumstances. First, when a squadron deploys, 

flight surgeon typically is not given adequate time to 

dress all of the topics and countermeasures covered in t

research. The doctors are usually limited in the amoun

time they are given to address a wide variety of deploym

concerns, with fatigue and circadian factors being only 

of them. Consequently, many pilots are uninformed ab

the potential dangers linked with fatigue. Second, th

seems to be a stigma associated with fatigue, especi

true in the fighter community, whereby aviators are 

pected to “gut it out” if they feel tired. Many flyers treat 

tigue as a joke or as a sign of hard work rather than a

signal that their bodies are in need of rest. Third, wh

medications are given to keep pilots awake on long depl

ments, some aviators misuse the drugs by saving them 

for when they land instead of using them during flight 

the onset of fatigue symptoms, as directed.

The challenge for commanders is to shatter the ster

types of fatigue and emphasize the importance of pro

sleep habits and appropriate countermeasures. Elimin

ing the images among aviators that fatigue is a sign 

weakness, laziness, or lack of motivation will be one of 

commander’s most difficult tasks. It all begins, howev

with allotting the flight surgeon enough time to addr
the problems of sleep debt and its effects upon perfor

ance and safety. Giving the doctors more equitable ti

with other support agencies such as weather, intelligen

and mission planners creates a mindset among the fly

that this topic is important and demands attention. F

thermore, a commander who personally stresses fatig

related concerns to his or her troops sends a message t

it is all right to get tired and that rest is an option. Four

commanders must be aware that change can be a s

process, and that they must remain proactive in ident

ing those aviators who refuse to back down. If they beli

that the flyer is fatigued, they must act responsibly by 

moving them from the flying schedule or emphasize to s

ordinate supervisors to do the same. Relying upon indiv

uals to make the right decision when they are tired can 

a formula for disaster.

There are many ways to combat the effects of fatig

and circadian disruption. Many of these strategies are p

sented in this paper. However, it is up to commanders 

be responsible to this insidiously dangerous risk and to 

corporate them into their decision-making process. 

order to assist commanders with dealing with the imp

fatigue might have on deploying units, the author reco

mends that the USAF Battlelab use the information fr

this research to pursue the development of a command

handbook. This guide should provide commanders w

useful data concerning alertness management strateg

as well as fatigue countermeasures. The handbook 

allow commanders to place increased emphasis on 

tigue’s impact on performance and safety with the aviat

on AEF deployments. Many—if not all—pitfalls of fatig

can be prevented or managed more effectively.

Notes

1. M. R. Rosekind et al., “From Laboratory to Flightdeck: Promo

Operational Alertness,” Royal Aeronautical Society, 1997, 7.1–7.14.

2. M. R. Rosekind et al., “Fatigue in Operational Settings: Exam

from the Aviation Environment,” Human Factors, 1994, 36(2).

3. Kelly J. Neville et al., “Subjective Fatigue of C-141 Aircrews du

Operation Desert Storm,” Human Factors 36(2), 1994, 339–49.

4. Ibid.
5. John A. Caldwell, “Fatigue in the Aviation Environment: 

Overview of the Causes and Effects As Well As Recommended Coun

measures,” Aviation, Space, and Environmental Medicine, October 1

932–38.

6. V. A. Convertino et al., “Health, Fitness, and Nutrition,” USAF F

Surgeon’s Guide, chap. 14.

7. Rosekind et al., “From Laboratory to Flightdeck.”

8. Ibid.

9. Ibid.

10. Ibid.

11. Ibid.

12. Ibid.

13. M. R. Rosekind et al., “Alertness Management: Strategic Nap

Operational Settings,” Journal of the Sleep Research Society 4, n

62–66.

PART V

Glossary, Definitions,

and Bibliography

Glossary

AEF Aerospace Expeditionary Force(s)

AEG Aerospace Expeditionary Group

AES Aerospace Expeditionary Squadron

AFI Air Force Instruction

ASRS Aviation Safety Reporting System

ATC arrival time coefficient

BAC blood alcohol concentration

CINC commander in chief

CNS central nervous system

EAF Expeditionary Aerospace Force

FAA Federal Aviation Administration

ICAO International Civilian Aviation Organization

NASA National Aeronautics and Space Administrati

NREM nonrapid eye movement

NTSB National Transportation Safety Board

REM rapid eye movement

USAF United States Air Force

49

Definitions

Aerospace Expeditionary Force. A cross section of ca

bilities that can be tailored to meet theater CINC ne

(http://www.af.mil/eaf/faq).

Air Force Instruction (AFI). A regulation governin

particular aspect of duty-related functions.

Aircrew. The full complement of officers and enlis

members required to operate an aircraft and to comp

an assigned mission (AFI 11-202, General Flight Ru

vol. 3, June 1998, 42–45).

Class A mishap. The most destructive class of mishaps 

terms of loss of life or damage to aircraft. It is defined 

a total mishap cost of $1,000,000 or more, a fatality 

permanent total disability, or destruction of an Air Fo

aircraft (AFI 91-204, Safety Investigations and Repo

29 November 1999, 45).

Crew rest period. The crew rest period is the nonduty 

riod before the flight duty period begins (AFI 11-202, 

3, 42–45).

Expeditionary Aerospace Force. The way the US Air Fo

will organize, train and equip to create a mindset and c

tural stat that embraces the unique characteristics 

aerospace power—range, speed, flexibility, precision—

all that we say and do. It is made up of AEFs, AEGs, a

AESs (http://www.af.mil/eaf/faq).

Flight duty period. A period that starts when an airc

reports for a mission, briefing, or other official duty a

ends when engines are shut down at the end of a missi

mission leg, or a series of missions (AFI 11-202, vol. 3

51

Bibliography

Air Force Instruction (AFI) 11-202. General Flight Ru

Vol. 3. June 1998.

AFI 48-123. Medical Examination and Medical Standar

1 January 2000.

AFI 91-204. Safety Investigations and Reports. 29 Nove

ber 1999.

Clinton, William J. “Bill.” A National Security Strategy fo

New Century. Washington, D.C.: The White House, 

cember 1999.

Caldwell, John A. “Fatigue in the Aviation Environme

An Overview of the Causes and Effects As Well As R

ommended Countermeasures.” Aviation, Space, and 

vironmental Medicine, October 1997.

———. “Sleepiness in the Cockpit,” Combat Edge, Aug

1999.

Caldwell, John A., et al. “Sustaining Helicopter Pilot P

formance with Dexedrine during Periods of Sleep Dep

vation.” Aviation, Space, and Environmental Medici

October 1995.

Co, E. L., et al. “Fatigue Countermeasures: Alertness M

agement in Flight Operations.” Proceedings of the 1

Annual International Aircraft Cabin Safety Symposiu

Long Beach, Calif.: Southern California Safety Institu

1994.

Convertino, V. A., et al. “Health, Fitness, and Nutritio

USAF Flight Surgeon’s Guide, chap. 14.

Neri, David F., et al. “The Effects of Tyrosine on Cogni

Performance during Extended Wakefulness.” Aviati

Space, and Environmental Medicine, April 1995.

Neville, Kelly J., et al. “Subjective Fatigue of C-141 A

crews during Operation Desert Storm.” Human Facto

1994, 36(2).

Nicholson, Anthony N., and Claire Turner. “Intensive a

Sustained Air Operations: Potential Use of the Stim

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Northrup, Susan E., “Melatonin and Aircrew,” Safetyli

’96. Vol. 7, issue 2, 16.

53
Peters, F. Whitten, and Michael E. Ryan. US Air Force P

ture Statement 2000.

Ramsey, Carol S., and Suzanne E. McGlohn. “Zolpidem 

a Fatigue Countermeasure.” Aviation, Space, and En

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Flight Operations,” Proceedings of the 39th Annual C

porate Aviation Safety Seminar, Flight Safety Foun

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———. “Alertness Management: Strategic Naps in Ope

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———. “Fatigue in Operational Settings: Examples fr

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———. “From Laboratory to Flightdeck: Promoting Ope

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———.“Managing Fatigue in Operational Settings I: Phy

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———. Headquarters USAF/XOPE, EAF Implementat

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