NASA/TM–1999-208780

Crew Factors in Flight Operations X:

Alertness Management in Flight Operations

Mark R. Rosekind, Philippa H. Gander, Linda J. Connell, and Elizabeth L. Co

April 1999

DOT/FAA/RD-93/18
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NASA/TM–1999-208780

Crew Factors in Flight Operations X:

Alertness Management in Flight Operations

Mark R. Rosekind

Ames Research Center, Moffett Field, California

Philippa H. Gander

San Jose State University Foundation

Ames Research Center, Moffett Field, California

Linda J. Connell

Ames Research Center, Moffett Field, California

Elizabeth L. Co

April 1999

National Aeronautics and

Space Administration

Ames Research Center

Moffett Field, California 94035-1000

San Jose State University Foundation

Ames Research Center, Moffett Field, California

DOT/FAA/RD-93/18
Available from:

NASA Center for AeroSpace Information National Technical Information Service

7121 Standard Drive 5285 Port Royal Road

Hanover, MD 21076-1320 Springfield, VA 22161

(301) 621-0390 (703) 487-4650

Acknowledgments

We thank the many pilots, air carriers, and individuals who have participated in or otherwise

supported the activities of the NASA Ames Fatigue Countermeasures Program. We wish to

acknowledge particularly the hundreds of volunteer pilots who have made the program possible;

the air carriers that have provided resources, support, and access to flight operations; and the

pilot unions that have continually pushed to highlight and support this area for scientific

research. Along with John Lauber and Charlie Billings, many of the original contributions and

program activities were due to the efforts of R. Curtis Graeber (Boeing) and Clay Foushee

(Northwest Airlines); James Jenkins at NASA Headquarters; Anthony Broderick, William White,

and Ronald Simmons at the FAA; Donald Hudson (Aviation and Preventive Medicine Associates); and academic colleagues: David Dinges (Institute of Pennsylvania Hospital and University

of Pennsylvania School of Medicine), William Dement (Stanford School of Medicine), Margaret

Moline (Cornell School of Medicine), and Timothy Monk (University of Pittsburgh School of

Medicine). Sharon Keenan (School of Sleep Medicine) provided helpful guidance in establishing

the structure of workshops to implement this module. Activities have included the International

collaboration of the following: Hans Wegmann, Alex Samel, and Alex Gundel (DLR Institute of

Aerospace Medicine, Germany); Anthony Nicholson and Peta Pascoe (Royal Air Force Institute

of Aviation Medicine, United Kingdom); Barbara Stone (Army Personnel Research Establishment, United Kingdom); Roderick Barnes and Geoffrey Bennett (Civil Aviation Authority,

United Kingdom); and Mitsuo Sasaki (Japan Air Lines and the Jikei School of Medicine,

Japan). The Fatigue Countermeasures Program has been fortunate to receive tremendous

support from many individuals at NASA Ames Research Center, especially William Reynard.

J. Victor Lebacqz, former Chief of the Flight Human Factors Branch at Ames, has recently

made invaluable contributions to all aspects of the program. Finally, the NASA Ames Fatigue

Countermeasures Program is an entity very much defined by the energetic, hardworking, and

dedicated people actively involved in the program: Donna Miller, Kevin Gregory, Roy Smith,

Lissa Webbon, Keri Weldon, Julie M. Johnson, Ray Oyung, Roxanne M. Johnson, Ron Anguilar,

and Malachi Boyle.

This publication is dedicated to John K. Lauber, Ph.D., and Charles E. Billings, M.D., for their

significant contributions to this subject and to aviation safety.
iii

CONTENTS

Foreword ...................................................................................................... v

Introduction ................................................................................................... vii

Presentation Materials with Text ............................................................................ 1

Appendix A: Brief Introduction to Sleep Disorders and Sleeping Pills ............................... 55

Appendix B: Brief Introduction to Relaxation Skills .................................................... 61

Appendix C: NASA Ames Fatigue Countermeasures Program

Representative NASA Technical Memoranda Operational Summaries ................ 63

Appendix D: NASA Ames Fatigue Countermeasures Program

Representative Publications ................................................................ 83

Appendix E: General Readings ............................................................................ 87

v

FOREWORD

This report is another in a series of research reports from Ames Research Center on the subject of

fatigue and jet lag in airline flight operations. However, the focus of this report is a bit different from

that of the others—rather than being a scientific study of the causes and effects of fatigue and jet lag, it

is a compendium of useful tips and personal management strategies for better coping with such causes

and effects. The information provided here is intended to be used by airline flight crew members to

help them develop effective countermeasures for the debilitating effects of flight schedules like the

following one, which provided me with my first glimpse of such operations. The report’s basic

premise is that in the modern world, there will always be a requirement for 24-hour flight operations,

and that it is possible for individual crew members to more effectively manage rest and sleep periods,

diet, exercise, and other personal factors in such a way that adverse performance effects of such

operations will be minimized. It is another tool that can be used by the professional pilot to further

enhance both the quality of performance and the quality of life.

I remember well my first practical exposure to fatigue and jet lag in airline flight operations. The year

was about 1975, and this trip was a “sunrise special.” I joined the crew of the DC-8 freighter at

dispatch at SFO for the all-night one-stop trip to JFK via DTW. Scheduled departure was to be about

2200 local, but some loading delays resulted in a takeoff closer to midnight. Sunrise (and it was

special—it always is from FL310) came just east of the Mississippi, and it was beautiful, bright, and

for about 30 minutes, shining directly into our eyes. Then we descended into the gloom that

surrounded DTW, landed in the rain, and stayed on the airplane for the scheduled hour or so that

turned into two or so, before making the last leg of the journey to New York, which we reached late in

the morning. I also remember the crew meals—well, the three crew members had crew meals, but for

me, the NASA observer, there was a cold deli sandwich with a big garlic dill. I can’t describe how I

felt when I found out what my “breakfast” consisted of at around 0300 that morning somewhere over

Nebraska.

About 2 hours after landing, our crew transport dropped us at a Manhattan hotel, where we had the

remainder of the day to rest, prior to departing for SFO about 2100 that night. The hotel was nice, but

noisy with vacuum cleaners and people in the hallways, and light was leaking through the curtains.

And the bed was definitely not my own. My light, fitful sleep did not really restore me to normal, and I

felt groggy and slightly disoriented when we reported to the hotel lobby for pickup.

Strong headwinds made a normally long trip even longer, and it seemed like the lights of SFO would

never come into view. But somehow they did and we landed about midnight, just about 24 hours after

we had left. Bad as I felt on the airplane, it was nothing compared to my hour-long drive home—I

don’t think I have ever experienced more difficulty trying to stay awake while driving, and I was

fortunate that nothing happened that required either quick thinking or quick reaction.

And then to bed, about 0200, but, alas, not to sleep—I was simply too “wound up” to fall asleep, and

my mind was swimming with imagery from the trip. As a result, the next day was a loss, and it wasn’t

really until the following day that I felt refreshed and recovered from my experience. It is fair to say

that I gained a whole new appreciation for what the life of an airline pilot is all about from that brief

exposure to “back of the clock” flying.

JOHN K. LAUBER, Ph.D.

Member

National Transportation Safety Board

December 1994

vii

INTRODUCTION

In 1980, in response to a congressional request, NASA Ames Research Center created a Fatigue/Jet

Lag Program to examine whether “there is a safety problem, of uncertain magnitude, due to transmeridian flying and a potential problem due to fatigue in association with various factors found in air

transport operations.”1 Since 1980, the Program has pursued the following three goals: (1) to determine the extent of fatigue, sleep loss, and circadian disruption in flight operations; (2) to determine the

effect of these factors on flight crew performance; and (3) to develop and evaluate countermeasures to

reduce the adverse effects of these factors and to maximize flight crew performance and alertness. It

has been a priority since the Program’s inception to return the information acquired through its

extensive research to the operators—the line pilots, air carriers, and others. In 1991, the Program

underwent a name change, becoming the NASA Ames Fatigue Countermeasures Program, to highlight

the increased focus on the development and evaluation of fatigue countermeasures. (For a more complete description of the Program, see footnote 2 below.) With this increased emphasis on countermeasures, it became important to organize and disseminate what had been learned about fatigue, sleep,

and circadian rhythms in flight operations.

Although data continue to accumulate, there is now enough scientific and operational data to create this

Education and Training Module on strategies for alertness management in flight operations. The overall purpose of this module is to promote aviation safety, performance, and productivity. It is intended

to meet three specific objectives: (1) to explain the current state of knowledge about the physiological

mechanisms underlying fatigue; (2) to demonstrate how this knowledge can be applied to improving

flight crew sleep, performance, and alertness; and (3) to offer strategies for alertness management.

This module is presented in three distinct parts. The first part addresses fatigue factors in flight

operations. It provides basic information on sleep, sleepiness, circadian rhythms, and how flight

operations affect these physiological factors. The second part identifies some widely held misconceptions and shows why they are false. Finally, the third part provides recommendations for alertness

management strategies in flight operations. This Education and Training Module is intended to be

offered as a live presentation by a trained individual. Its interactive format will provide a forum for

discussions of how this information and the recommended strategies can be applied in specific flight

operations.

This NASA/FAA document was developed to complement the live presentation of the Module. It

includes a foreword by Dr. John K. Lauber, one of the original investigators who started the NASA

Ames Fatigue/Jet Lag Program and a former Member of the National Transportation Safety Board.

The information contained in the presentation slides constitutes the main body of this publication.

 

1Pilot Fatigue and Circadian Desynchronosis. (1980). Report of a workshop held in San Francisco, CA, on

August 26–28,1980. NASA Technical Memorandum No. 81275. Moffett Field, CA: National Aeronautics and Space

Administration.

2Rosekind, M.R., Gander, P.H., Miller, D.L., Gregory, K.B., McNally, K.L., Smith, R.M., and Lebacqz, J.V. (1993).

NASA Ames Fatigue Countermeasures Program. FAA Aviation Safety Journal, 3(1), 20–25.
viii

Brief introductions to sleep disorders and to relaxation techniques are presented in appendixes A

and B, respectively. Appendix C contains summaries of relevant NASA publications, including

studies in short-haul, long-haul, and helicopter operations, and the NASA/FAA study on planned

cockpit rest in long-haul flying. The last two appendixes provide a list of representative publications

from the NASA Ames Fatigue Countermeasures Program (appendix D) and a list of general readings

on sleep, sleep disorders, and circadian rhythms (appendix E).

The format of this publication is designed for two purposes: (1) to facilitate training and (2) to provide

a reference for those who use the information. For trainers, the slides provide presentation material,

while the text provides some guidelines as to what information should be addressed when presenting

the Module. For those applying the information, the text elaborates on the slides for later reference.

This is the first formal step taken by the NASA Ames Fatigue Countermeasures Program to provide

education and training information on fatigue, sleep, and circadian rhythms in flight operations, and to

recommend strategies for managing alertness on the flight deck. As future scientific and operational

advances are made, this module will evolve to incorporate the latest findings, information, and recommendations. Therefore, any comments, questions, or requests regarding this module would be greatly

appreciated. Please address them to: Fatigue Countermeasures Program, NASA Ames Research

Center, MS 262-4, Moffett Field, California 94035-1000.
1

Fatigue Countermeasures Program

Alertness Management in Flight Operations

NASA Ames Research Center

Human Factors Research and Technology Division
2

Fatigue Countermeasures Program

Objectives

• Explain the current state of knowledge about

the physiological mechanisms underlying fatigue

• Demonstrate how this knowledge

can be applied to improving flight crew

sleep, performance,and alertness

• Recommend alertness management strategies

In response to a 1980 congressional request, NASA Ames Research Center

initiated a Fatigue/Jet Lag Program to examine fatigue, sleep loss, and circadian

disruption in aviation. Research has examined fatigue in a variety of flight

environments using a range of measures (from self-report to performance to

physiological). In 1991, the program evolved into the Fatigue Countermeasures

Program, emphasizing the development and evaluation of strategies to maintain

alertness and performance in operational settings. Over the years, the Federal

Aviation Administration (FAA) has become a collaborative partner in support of

fatigue research and other Program activities.

From the inception of the Program, a principal goal was to return the

information learned from research and other Program activities to the operational

community. The objectives of this Education and Training Module are to explain

what has been learned about the physiological mechanisms that underlie fatigue,

demonstrate the application of this information in flight operations, and offer some

specific fatigue countermeasure recommendations. It is intended for all segments

of the aeronautics industry, including pilots, flight attendants, managers, schedulers,

safety and policy personnel, maintenance crews, and others involved in an

operational environment that challenges human physiological capabilities because

of fatigue, sleep loss, and circadian disruption.
3

Fatigue Countermeasures Program

Overview

• Fatigue Factors in Flight Operations

• Common Misconceptions

• Alertness Management Strategies

• Discussion

The presentation is divided into three parts, followed by a discussion. First,

there is a description of fatigue factors in flight operations, including a demonstration

that fatigue is of national interest and a discussion of the principal causes of fatigue

(i.e., sleep and sleep loss, circadian rhythms and their disruption, and the effects of

flight operations on these physiological factors). Second, several examples of common

misconceptions regarding fatigue in aviation are presented, and application of the

information provided in the first part demonstrates why these notions are incorrect.

Third, a variety of countermeasures are presented, including preventive approaches that

can be used before going on duty or on layovers, as well as operational countermeasures

to use during duty periods. Finally, a critical component of this module is the

application of the information provided to the specific demands of the audience’s or

reader’s flight activities. The discussion is intended to demonstrate and give specific

examples of how this information can be applied to different types of flight schedules,

individual physiological differences, and the varying operational requirements of a given

audience. It is intended to be highly interactive with specific examples provided by

participants.
4

Fatigue Countermeasures Program

Fatigue Factors in

Flight Operations

The first two sections of this part will discuss the two main physiological factors

that affect fatigue: 1) sleep and sleep loss, and 2) circadian rhythms. With the principles

of these physiological factors as a background, a third section will then discuss the

effects of flight operations on fatigue.
5

Fatigue Countermeasures Program

Is Fatigue a Concern in Flight Operations?

• NASA Aviation Safety Reporting System (ASRS)

– 21% of reported incidents mention fatigue-related factors

• National Transportation Safety Board (NTSB)

– “...it is time for an aggressive Federal program to address the

problems of fatigue and sleep issues in transportation safety”

– “...educate pilots about the detrimental effects of fatigue and

strategies for avoiding fatigue and countering its effects”

– Fatigue cited as probable cause in Guantanamo Bay aviation accident

• Federal Aviation Administration (FAA)

– An objective of the National Plan for Aviation Human Factors

The following three sources indicate that fatigue is a concern acknowledged at

a national level.

Approximately one of five reports to the NASA Aviation Safety Reporting

System (ASRS) mention fatigue-related factors. Fatigue may be a contributory

factor in 21% of these incident reports.

The National Transportation Safety Board (NTSB) has stated the following in

Safety Recommendations I-89-1, I-89-2, and I-89-3: “Based on its experience in

accident investigation, the Safety Board believes it is time for an aggressive Federal

program to address the problems of fatigue and sleep issues in transportation

safety.” On January 19, 1994, based on a Safety Study Review, the NTSB

recommended that the FAA “Require U.S. carriers operating under 14 CFR Part

121 to include, as part of pilot training, a program to educate pilots about the

detrimental effects of fatigue, and strategies for avoiding fatigue and countering its

effects.” A parallel recommendation was made regarding Part 135 carriers. For the

first time, the NTSB cited fatigue as a probable cause in the Guantanamo Bay

aviation accident. Through the research and other activities of the NASA Ames

Fatigue Countermeasures Program, the FAA, and the NTSB, aviation is ahead of

most other modes of transportation in examining the issue of fatigue and,

especially, in developing potential countermeasures.

The FAA’s National Plan for Aviation Human Factors identifies fatigue as an

area for continued basic and applied research. These are only three examples of

highly visible national agencies that acknowledge and call for continued activities

addressing the issue of fatigue in aeronautical operations.
6

Fatigue Countermeasures Program

What Can Be Done About Fatigue?

• Change the FARs—takes an act of Congress (almost)

• Research fatigue issues that support FAA efforts

• Apply strategies to better cope with the current situation

This presentation will clearly demonstrate that fatigue in flight operations is a

complex issue with no one simple answer. Rather, every component of the aviation

system that can be addressed to improve alertness and performance in flight operations

should receive attention. Several examples are provided here.

The Federal Aviation Regulations (FARs) could provide one means of incorporating

what is now known about the physiological mechanisms that produce fatigue. This can

be a long process and one that can be complex in its own right. The FAA recently

established an Aviation Rulemaking Advisory Committee working group that examined

current flight/duty/rest requirements. The working group evaluated current FAR

requirements, and their interpretation and application within the aviation industry. Also,

the FAA has established a rulemaking team to examine flight/duty/rest requirements.

Another approach is to conduct research that provides scientific data to be used by

policymakers concerned with regulatory issues or interpretation of the FARs. The

research can be the basis for a variety of actions, including the production of Advisory

Circulars.

In another possible approach, the information provided in this presentation can be

used right now by any individual challenged by the physiological demands of flight

operations. The basic information and countermeasure recommendations can be used by

all in the aviation industry who want to improve their ability to cope with the existing

situation.
7

Fatigue Countermeasures Program

NASA Fatigue Countermeasures Program

• Since 1980, research on fatigue, sleep, and circadian

rhythms in different types of flight operations

• Testing and implementation of alertness strategies

• Input to FAA

Example: In-flight test of naps as a strategy in

3-person long-haul crews; FAA in NPRM process

• Scientific and technical publications

This information provides some insight into the research and activities that created

the foundation for the development of this Education and Training Module. Since 1980,

the NASA Ames Fatigue Countermeasures Program, in collaboration with the FAA, has

conducted fatigue research; recently, it has emphasized the testing and implementation

of countermeasures. An example of these activities is the recent NASA/FAA study of

planned cockpit rest, which demonstrated the effectiveness of a controlled in-flight nap to

improve subsequent alertness and performance during critical phases of flight. The FAA

is currently in the Notice for Proposed Rulemaking (NPRM) process for “Controlled Rest

on the Flight Deck.” Another important ongoing Program contribution is the production

of scientific and technical publications, as well as industry articles, reporting study results

and other information related to fatigue and potential countermeasures. Some representative Program publications suggested for further reading are provided in appendix D.
8

Fatigue Countermeasures Program

Causes of Fatigue

Effect of flight operations on

sleep and circadian physiology

FLIGHT

CREW

FATIGUE

Sleep loss Circadian

rhythms

Fatigue is really a catchall term for a variety of different subjective experiences,

for example, physical discomfort after overworking a particular group of muscles,

concentration difficulties during a monotonous task, difficulty appreciating potentially

important signals following long or irregular work hours, or simply difficulty staying

awake. In the context of flight operations, crewmember fatigue becomes important if it

reduces efficiency or otherwise impairs crew performance. Subjective fatigue can be

affected by motivation or by the amount of stimulation coming from the environment.

However, there are two systematic physiological causes of fatigue (and poorer

performance)—sleep loss and circadian rhythms—both of which are affected by flight

operations. It is also important to note that inadequate rest can result in sleep loss and

circadian disruption, and can therefore be a source of fatigue in its own right. The

NASA Fatigue Countermeasures Program focuses on these factors.
9

Fatigue Countermeasures Program

Fatigue Factors in Flight Operations:

Sleep and Sleep Loss

This section provides basic information about the complex physiological process of

sleep and the effects of sleep loss and sleepiness.
10

Fatigue Countermeasures Program

Sleep Physiology: Two States of Sleep

• NREM (non-rapid eye movement) sleep

Physiological and mental activity slowed

Light sleep (stages 1 and 2); deep sleep (stages 3 and 4)

• REM (rapid eye movement) sleep

Physiological and mental activity increased

An active brain (dreaming) in a paralyzed body

It is widely believed that sleep is a time when the brain and the body shut off and

then re-engage upon awakening. Actually, sleep is a highly complex physiological

process during which the brain and body alternate between periods of extreme activity

and quiet, but are never “shut off.” Sleep is composed of two distinct states: NREM, or

non-rapid eye movement, and REM, or rapid eye movement, sleep. These two sleep

states are as different from each other as they are from wakefulness.

During NREM sleep, physiological and mental activities slow (e.g., heart rate and

breathing rate slow and become regular). NREM sleep is divided into four stages, with

the deepest sleep occurring during stages 3 and 4. There is usually very little mental

activity during NREM stages 3 and 4. If awakened during this deep sleep, an individual

may take sometime to wake up and then continue to feel groggy, sleepy, and perhaps

disoriented for 10–15 minutes. This phenomenon is called sleep inertia.

REM sleep is associated with an extremely active brain that is dreaming, and with

bursts of rapid eye movements (probably following the activity of the dream); during

REM sleep, the major motor muscles of the body are paralyzed. If awakened during

REM sleep, individuals can often provide detailed reports of their dreams.
11

Fatigue Countermeasures Program

Sleep Architecture: NREM/REM Cycle

• NREM and REM alternate throughout each sleep period

• Most deep sleep occurs in the first half of the sleep period

• REM periods are longer and more regular later in the

sleep period

Over the course of a typical night, NREM and REM sleep occur in a cycle, with

about 60 minutes of NREM sleep followed by about 30 minutes of REM sleep. This

90-minute cycle repeats itself throughout a typical sleep period. However, most deep

sleep (i.e., NREM stages 3 and 4) occurs in the first third of the night, and REM periods

are shorter early in the night and then become longer and occur more regularly later in

the sleep period. Overall, about 25% of sleep time is spent in REM sleep and about 50%

is spent in NREM stage 2.
12

Fatigue Countermeasures Program

Histogram of Normal Sleep

Wake

REM

Stage 1

Stage 2

Stage 3

Stage 4

Time

2400 0100 0200 0300 0400 0500 0600 0700

This graph portrays a typical night of sleep for a normal adult. It exemplifies the

sleep architecture discussed on the previous slide: REM (indicated by darkened bars)

and NREM alternating throughout the period; most deep sleep occurring in the first half

of the sleep period; and REM periods becoming longer and more regular later in the

sleep period.
Fatigue Countermeasures Program

Sleep Physiology

• Amount and structure of sleep changes over the life span

Sleep becomes less deep, more disrupted, and total nocturnal sleep decreases

Daily percentage sleep loss is 3.5 times greater in long-haul flight crewmembers

aged 50–60 than in those aged 20–30

• Quantity vs quality of sleep

Getting 8hr of disrupted sleep can have effects similar to too little sleep

After sleep loss, sleep is deeper rather than longer

The amount and structure of sleep change profoundly over the life span. With

increased age, sleep becomes less deep (most NREM stages 3 and 4 disappears) and

more disrupted (awakenings increase), and the total amount of nocturnal sleep decreases.

It is not that older individuals need less sleep, but it appears that with age, our ability to

obtain a consolidated and continuous period of nocturnal sleep decreases. These

changes can be seen in individuals starting as early as 50 years of age. This normal part

of the aging process is reflected in a recent finding from a NASA study. Long-haul

flight crewmembers aged 50–60 had a daily percentage sleep loss 3.5 times greater

during trip schedules than those aged 20–30 years.

The quality of sleep can be as critical as the quantity of sleep in restoring an

individual. If an individual obtains 8 hours of sleep but the sleep is disrupted tens or

hundreds of times, then upon awakening, the individual may feel as if only a few hours

of sleep were obtained. There are many diverse reasons for disrupted sleep, from

environmental causes (e.g., noise, light) to physical sleep disorders. For example, there

is a sleep disorder called “periodic leg movements during sleep” that involves one or

both legs twitching throughout sleep (see appendix A for further information). With

each leg twitch, the sleeper is awakened briefly. Hundreds of these brief awakenings can

occur during one sleep period. The sleeper can be completely unaware of the twitches or

awakenings but feel sleepy and tired even after 8 hours of this fragmented sleep.

Another commonly held belief is that after sleep loss, an individual has to “make up”

that sleep by sleeping a number of hours equal to those lost. Scientific laboratory studies

have demonstrated that following sleep deprivation, recovery sleep is deeper (more

NREM stages 3 and 4), rather than extended. During recovery sleep, an individual

might sleep somewhat longer, but the most notable feature is the increase in deep sleep.

13
14

Fatigue Countermeasures Program

Sleep Physiology

• Effects of alcohol

Suppresses REM, leads to withdrawal effects and more disrupted sleep

Short-haul pilots increase consumption threefold on trips

Can interact with sleep loss to increase sleepiness

• Effects of medications

Can delay sleep onset, disrupt sleep structure, alter total sleep time

• Effects of environmental factors

Noise, temperature, light, etc. may interfere with good sleep

Alcohol has a profound effect on the usual sleep cycle. After more than a

couple of glasses of wine or a couple of beers (with individual variations), alcohol

can essentially eliminate all of the REM sleep in the first half of a sleep period.

This can lead to subsequent alcohol withdrawal effects in the second half of the

sleep period, including sleep fragmentation. Unfortunately, the most widely used

sleep aid in the United States is alcohol. Ironically, although often used to

promote relaxation and the ability to fall asleep, it will generally have major

disruptive effects on the subsequent sleep. One NASA study found that short-haul

pilots increased their alcohol consumption threefold during trips compared with

home consumption. The pilots used alcohol within FAR guidelines to unwind

after long duty days that included multiple flight segments and to promote sleep

onset before an early wake-up for the subsequent duty day. Alcohol also interacts

in a synergistic fashion with sleepiness. A sleep-deprived individual who is

already sleepy will demonstrate more severe performance and alertness

impairment following alcohol consumption.

There are many medications (non-sleeping pill), both prescribed and over-thecounter, that can adversely affect sleep. Depending on the specific action of these

medications, they may delay sleep onset, disrupt the sleep structure, or alter total

sleep time.

Environmental factors may also interfere with good sleep. Noise, light, low

or high temperatures, and a variety of other factors can decrease the quantity and

quality of sleep. With FAA support, NASA has examined the effects of

environmental factors on sleep in on-board crew rest facilities.
15

Fatigue Countermeasures Program

Sleep Physiology

• Sleep disorders can disturb sleep and waking alertness

Sleep problems can be diagnosed and treated by sleep-disorder specialists

• Sleeping pills

Some help you fall asleep, stay asleep, which may improve your waking alertness

Some alter sleep structure, create dependency, have carryover effects that

may decrease waking alertness and performance

Only recommended at the prescribed dose for short periods of time

May have potentially serious side effects

There are physical sleep disorders that can disturb sleep and impair waking

alertness and performance. (See Appendix A for some examples, such as sleep

apnea.) These sleep disorders can have profound effects on waking function, and yet

occur with the sleeper essentially unaware of their existence. Sleep problems can be

diagnosed and treated effectively by accredited sleep disorders specialists and clinics.

Appendix A also provides some general information about sleeping pills. Some

prescription sleeping pills may facilitate falling asleep and staying asleep, with

subsequent improvements in waking alertness and performance. However, many

sleeping pills alter sleep structure dramatically, create drug dependence, and have

carryover effects that decrease waking alertness and performance. Proper use of these

medications typically means taking the lowest dose, and that for only a few days.

Many sleeping pills can have potentially serious side-effects, and none should be

taken except under the care and guidance of a physician.
16

Fatigue Countermeasures Program

Sleep is a Vital Physiological Function

• Sleep loss is additive and results in a cumulative sleep debt

• Sleep loss leads to increased sleepiness

• Consequences of sleepiness

Decreased physical and mental performance

Decreased positive and increased negative mood

Increased vulnerability to performance decrements

 Like food and water, sleep is a physiological need vital to human survival and critical to

human existence. Sleep loss can be additive and can result in a cumulative sleep debt. Estimates

suggest that in the United States, most people get 1–1.5 hours less sleep than they need. During a

regular 5-day work week a typical individual might accumulate a 7.5-hour sleep debt, equal to a full

night of sleep loss, going into a weekend. In today’s society, many individuals actively attend to

their nutrition and exercise to promote good health. Unfortunately, the first physiological need that

suffers when individuals are faced with everyday pressures and demands is sleep. Losing sleep

becomes a way of squeezing more hours and minutes into the day, which demonstrates a lack of

concern for meeting this vital physiological need.

 Sleep loss leads to increased waking sleepiness. Many people equate sleepiness with

being lazy or acknowledge it only humorously. Sleepiness can have severe consequences for us

as individuals and as a society. Sleepiness can degrade essentially every aspect of human

performance. Sleep loss and sleepiness can decrease physical, psychomotor, and mental

performance, and can increase negative mood and decrease positive mood. Therefore, a principal

consequence of sleepiness is an increased vulnerability to performance decrements. It is important

to consider this as a performance vulnerability because, like the effects of alcohol on performance

and memory, sleepiness can lead to a reduced safety margin and an increased potential for

operational incidents and accidents. Sleep loss and sleepiness resulting from extended duty or

altered work/rest schedules have been suggested as contributory factors in many accidents and

catastrophes. As individuals, many people put themselves at personal risk by driving when too

sleepy, sometimes experiencing a near incident or an actual accident.

 Sleep loss can result in a cumulative sleep debt and waking sleepiness. Sleepiness should

be taken seriously. Its profound effects on waking performance, mood, and alertness can create a

vulnerability to operational incidents and accidents. That vulnerability can be minimized, thus

potentially avoiding an incident or accident.
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Fatigue Countermeasures Program

Sleepiness: Two Distinct Components

• Physiological sleepiness

– Lose sleep, get sleepy

– Underlying biological process

– Only reversed by sleep

• Subjective sleepiness

– How you feel; what you report

– Can be concealed or altered by environmental

stimulation, physical activity, caffeine, etc.

Two distinct components of sleepiness have been described. Physiological

sleepiness parallels other vital physiological functions like hunger and thirst. Deprived

of food or water, the brain signals that these vital physiological needs have not been met

by developing feelings of hunger and thirst. When physiologically deprived of sleep, the

brain’s signal is sleepiness. Just as the only way to reduce or eliminate hunger or thirst

is to eat or drink, when an individual is physiologically sleepy, only sleep will reverse

this vital need.

Subjective sleepiness is an individual’s introspective assessment of the feeling and a

self-report of that status. An individual can rate current sleepiness on a scale from “wide

awake and alert” to “extremely sleepy, ready to nod off.” However, this self-reported

rating can be strongly affected by a variety of factors, such as environmental stimulation.

The level of underlying physiological sleepiness can be concealed by an environment in

which an individual is physically active, has consumed caffeine, or is engaged in a lively

conversation. Whereas these factors may affect the self-reported rating of sleepiness

(usually individuals will report greater alertness than is warranted), they do not affect the

underlying sleep need expressed by the level of physiological sleepiness.
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Fatigue Countermeasures Program

Subjective vs Physiological

Sleep and Alertness

• It can be difficult to reliably estimate your own sleep

and alertness, especially if you are already sleepy

• The good news:

Tendency to overestimate time to fall asleep and underestimate total sleep time

It may not be as bad as you think

• The bad news:

Tendency to report greater alertness than indicated by physiological measures

It may be worse than you think

It is usually difficult for most individuals to reliably estimate their own sleep or their

waking alertness, especially if they are already sleepy.

Overall, there is a tendency for individuals to subjectively overestimate how long

it takes to fall asleep and underestimate total sleep time, relative to physiological

measures. Generally, people fall asleep faster and sleep longer than they think. So

when an individual experiences a bad night of sleep, it may not be as bad as it seemed.

However, the tendency is for individuals to subjectively rate themselves as more

alert than is indicated by physiological measures. That is, most individuals are more

likely to be sleepier than they report or experience.
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Fatigue Countermeasures Program

Factors Affecting Sleepiness

• Prior sleep/wakefulness

• Circadian phase

• Age

• Medical conditions

• Medications

• Alcohol

• Environmental/work conditions

These factors have been demonstrated to affect waking sleepiness and therefore

could be considerations in worsening or improving sleepiness.
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Fatigue Countermeasures Program

Sleepiness

• In a usual 24-hour day, there are two times of

increased sleepiness: 3–5 a.m. and 3–5 p.m.

• Performance and alertness can be affected

during a 2 a.m. to 6 a.m. window

We are physiologically programmed for two periods of maximal sleepiness in a

usual 24-hour period. The period 3–5 A.M. is a circadian low point for temperature,

performance, and alertness. During this time, the brain triggers sleep and sleepiness.

The other period of increased sleepiness is roughly 3–5 P.M. Most individuals have

experienced an afternoon wave of sleepiness. These windows can be used to schedule

sleep periods or naps because the brain provides a period of maximal sleepiness and an

increased opportunity for sleep.

Performance and alertness can be decreased during the nocturnal window, which is

from 2 A.M. until 6 A.M. For some, the afternoon window of sleepiness may occur

between 2 P.M. and 4 P.M. This highlights some of the differences among individuals.
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Fatigue Countermeasures Program

Fatigue Factors in Flight Operations:

Circadian Rhythms

This second section provides basic information about circadian rhythms and

how they apply to fatigue, jet lag, and shift work. Circadian rhythms are the second

physiological factor that affects fatigue in flight operations.
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Fatigue Countermeasures Program

Circadian Rhythms

• Circa = about; dies = day

• A circadian clock in the brain coordinates daily cycles:

Sleep/wake Performance

Temperature Hormones

Digestion Etc.

• Without any timing information from the environment,

the biological day is about 25 hours

Over evolutionary time, the daily cycles in the physical environment (produced by

the Earth’s rotation) have become hard-wired into our neuronal circuitry in the form of a

biological clock in the suprachiasmatic nucleus of the hypothalamus. However, since

the beginning of the industrial revolution, we have developed a cultural environment in

which there is ever-increasing pressure for round-the-clock operations and services. The

expedient (but incorrect) assumption that we can and do function equally at any time of

the day or night underlies many activities in our society, from medical diagnosis and

treatment to many hours-of-service regulations.

When people live alone in environments from which all possible time cues have been

carefully excluded (deep caves, underground bunkers, or specially designed apartments),

they begin to live “days” that are generally longer than 24 hours. Regardless of how

long someone’s subjective “day” becomes in a time-free environment, however, the

circadian clock still enforces an approximately 25-hour cycle in many functions. Some

people even develop “days” as long as 50 hours with, for example, 36 hours of

wakefulness followed by 14 hours of sleep.

The circadian clock can be thought of as analogous to the conductor of a symphony

orchestra. Many different systems in the body, down to the level of individual cells, are

capable of generating circadian rhythms independently, just as the members of an

orchestra must each be capable of playing their own part. However, if they are not all

synchronized appropriately, the harmony rapidly degenerates into cacophony.
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Fatigue Countermeasures Program

Circadian Rhythms of a DC-9 Pilot

Sleep period

Duty period

 Pre-trip Trip

day 1

Trip

day 2

 Trip

day 3

 Post-trip

day 1

 Post-trip

day 2

0

35

70

105

140

0.0

1.0

2.0

3.0

35

36

37

38

39

20

40

60

80

Temperature

Physical activity

(actigraphy)

Fatigue

(subjective)

Activation

(subjective)

This figure shows a number of different circadian rhythms measured simultaneously in

a 46-year-old DC-9 First Officer before, during, and after 3 days of scheduled commercial

short-haul flying in the eastern United States. To obtain these data, the pilot wore a

portable biomedical monitor which recorded his core body temperature, level of physical

activity (measured using actigraphy), and average heart rate every 2 minutes. He also

carried a logbook in which he rated his fatigue and mood, including subjective activation,

every 2 hours, and kept detailed records of all his activities, including when and how well

he slept.

Vertical shaded bars indicate times when the pilot reported being asleep. Since he

was flying during the day and sleeping at night, his circadian rhythms during the trip

maintained their normal relationships to one another and to the environment.

This figure illustrates an important feature of the circadian temperature rhythm. The

pilot’s temperature reached a minimum during his daily sleep period, and began to rise well

before he awakened. This spontaneous rise in temperature is not the result of increased

physical activity. It reflects the action of the circadian clock, which is envisaged to drive a

cyclic variation in the setpoint of the temperature-regulating system. In general, changes in

heart rate closely paralleled the changes in the level of physical activity. As expected, by

the end of the day the pilot felt more fatigued and reported less activation.
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Fatigue Countermeasures Program

Circadian Rhythms

The circadian clock is synchronized (reset) daily by:

• Bright light (sunlight)

– In the morning advances the circadian clock

– In the middle of the day has little effect

– In the evening delays the circadian clock

• Work/rest schedules

• Regular social interaction

Unless timing information is received from the environment, the human circadian clock

tends to run slow. The specific environmental time cues which synchronize it to a 24-hour

day are known by the German term “zeitgebers,” meaning “time-givers.” Currently, two

types of zeitgebers have been identified: exposure to bright light and social factors.

Bright light (more than about 2500 lux—normal indoor light is generally less than 500

lux) affects the circadian clock by means of a direct neural pathway from the eye. The

principle behind synchronization of the circadian clock by light/dark cycles is reasonably

well understood and can be summarized as follows.

1. Light exposure in the subjective morning advances subsequent circadian cycles.

2. Light exposure in the middle of the subjective day has minimal effect.

3. Light exposure in the subjective evening delays subsequent circadian cycles.

To synchronize a circadian clock with an innate period of 25 hours to a 24-hour day

requires that the clock be advanced by 1 hour per day. An appropriate exposure to sunlight

every morning would achieve the necessary resetting. Conversely, to synchronize a clock

with an innate period of 23 hours would require a delay of 1 hour per day, in other words, an

appropriate exposure to sunlight every evening. These examples are intended to illustrate

the mechanism of synchronization (also known as “entrainment”). Clearly, however, they

are highly simplistic. In everyday life, synchronization of an individual’s circadian clock to

a 24-hour day depends on a complex combination of different zeitgeber inputs.

There is some evidence that the human circadian clock may be synchronized by certain

social factors, including the work/rest schedule. However, the specific aspects of the social

environment that constitute time cues have not yet been identified, and the mechanisms by

which they affect the clock remain unknown.
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Fatigue Countermeasures Program

Circadian Rhythms

The circadian clock cannot adapt immediately to a new

environmental time or to a duty/rest schedule change

We cannot, as yet, reset our circadian rhythms at will, as we do our wrist watches.

However, this is the aim of most circadian countermeasures.

It may take days to weeks for all rhythms to synchronize to a new time zone after

one transmeridian flight. During commercial long-haul operations, flight crews usually

have 1–2 days at each layover destination before they operate another transmeridian

flight. Thus, they seldom become fully synchronized to local time during layovers.

Similarly, shift workers are rarely, if ever, fully adapted to one work/rest schedule

before they switch back to normal daytime activity and nighttime sleep on their next

days off. In the case of rotating shift workers, going back to work then means trying to

adapt to yet another work/rest schedule. Two different approaches have developed for

scheduling rotating shift workers. With rapid rotations (changing hours of work every

few days), circadian adaptation to any one work/rest pattern is minimal, and workers

revert easily to being day-active on their days off. This approach is more common in

Europe. With slower rotations (changing the hours of work every 1–2 weeks), the

circadian clock has more time to synchronize to a given work/rest schedule. Sleep and

performance are thus expected to improve progressively, at least until the next day off.

This approach is generally preferred in the United States.

The problems engendered by the slow adaptation of circadian rhythms to new time

zones and duty/rest schedule changes are examined in the following slides.
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Fatigue Countermeasures Program

Shift Work

• Night work: any schedule that requires someone to be

awake and active when they would normally be asleep

• Requires overriding the circadian clock which

pre-programs daytime activity and nighttime sleep

• Creates conflict between environmental synchronizers:

– Work/rest schedules

– Day/night cycles

– Day-oriented society

• People switch back to daytime activity on days off

The basic problem with shift work is that it requires people to somehow override

the circadian clock, which pre-programs us for daytime activity and nighttime sleep.

The work/rest schedule itself may reset the clock of the shift worker to some extent.

However, the competing zeitgeber inputs from the day/night cycle and our predominantly

day-oriented society continually push it back toward its usual diurnal orientation. Thus,

at best, the circadian rhythms of shift workers usually are only partially adapted to their

current work/rest schedule. In addition, most shift workers revert to being day-active on

their days off. This continuously changing orientation can result in chronic desynchronization of the circadian clock relative to the environment, and persistent internal

desynchronization among different physiological systems.

The conflicting zeitgeber environment typical of shift work is further confounded in

aviation operations by the day-to-day instability of the duty/rest cycles and by the element

of unpredictability (associated with weather, mechanical problems, system delays, and

other operational factors).
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Fatigue Countermeasures Program

Jet Lag

• Abrupt change in environmental time:

The circadian clock is out of step with the environment

• Gradual and uneven adaptation of different circadian rhythms:

Different physiological functions are out of step with one another

Crossing time zones produces an additional zeitgeber disruption regularly

encountered by flight crews. The circadian clock resynchronizes only gradually to a

new environmental time. Circadian rhythms in different functions adjust more or less

quickly, depending on the tightness of their coupling to the clock and on their

interactions with other physiological functions, each adapting at its own rate. Thus,

after a transmeridian flight, not only is the circadian clock out of step with the local

zeitgebers, but also different physiological functions are out of step with one another.

During commercial long-haul operations, crewmembers rarely stay long enough in

one time zone for their circadian clocks to become synchronized to local time. Rapid

sequences of transmeridian flights present continuously changing zeitgeber signals

to the clock, which is buffeted back and forth and unable to stabilize.
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Fatigue Countermeasures Program

Symptoms of Shift Work and Jet Lag

• Disturbed sleep (inability to fall asleep or stay asleep)

• Increased waking (work-time) sleepiness

• Decreased physical or mental performance

• Increased reports of fatigue

• More negative mood

• Gastrointestinal problems

Recent overviews of studies with shift workers indicate that 60% of them have sleep

complaints, whereas only 20% of day workers have similar complaints; 75% of night

workers experience sleepiness on every shift, and 20% report falling asleep.

Shift workers (particularly rotating shift workers) have a higher incidence of sick

leave, more frequent visits to health care facilities at the work site, and more general

health complaints than day workers. Night shift workers have higher incidences of

gastrointestinal disorders, including general stomach discomfort and ulcers, than do

day workers. These symptoms probably result from the interaction of several factors,

including circadian desynchronosis and the increased domestic and social stresses that

often accompany shift work.
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Fatigue Countermeasures Program

Factors Affecting Circadian Adaptation

• Takes longer the more time zones are crossed

• Faster after a westward flight (delay direction) or

with progressively later duty times because the

biological day is usually longer than 24 hours

• Different people adapt at different rates

• “Evening-types” adapt faster than “morning-types”

• Ability to adapt decreases with age

Circadian adaptation in flight crews after transmeridian flights has been examined in

only a few studies.

Klein and colleagues at the DLR (the German Aerospace Establishment) found that

flying skills of 12 German fighter pilots tested in an F-104 simulator were less impaired

after a westward flight (as passengers) crossing eight time zones than after the return

eastward flight.

A joint study conducted by NASA and the Royal Norwegian Air Force Institution of

Aviation Medicine examined adaptation of 9 crewmembers operating Orion P-3 aircraft

during eastward and westward flights across nine time zones. Adaptation of sleep and

the temperature rhythm to local time was faster after westward flights.

In an international study coordinated by NASA, sleep of long-haul flight crews

during the first layover of scheduled international trips was less disturbed after westward

flights crossing eight to nine time zones than after eastward flights crossing eight time

zones. In the same study, crewmembers who scored as more evening-type showed lower

levels of daytime sleepiness after an eastward flight crossing eight time zones (TokyoSan Francisco) than did more morning-types.

A NASA study of the effects of aging found that as flight crews get older, they

become more morning-type and the amplitude of their circadian temperature rhythm

declines. Daily percentage sleep loss during trips was 3.5 times greater among long-haul

crews aged 50–60 than among long-haul crews aged 20–30.
30

Fatigue Countermeasures Program

Fatigue Factors in Flight Operations:

Effect of

Flight Operations

The previous two sections dealt with the principal physiological factors that create

fatigue. This section identifies how flight operations play a role in creating flight crew

fatigue.
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Fatigue Countermeasures Program

Effect of Flight Operations

Flight operations are not always conducive

to a regular sleep/wake schedule

Certain kinds of flight operations occur during the day, involve minimal time-zone

changes (and therefore minimal circadian disruption), and may have a minimal effect on

usual sleep/wake schedules. However, it is very clear that many flight operations are not

conducive to regular sleep/wake schedules.
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Fatigue Countermeasures Program

Effect of Flight Operations

Duty at unusual or changing times in the day/night

cycle, or time-zone crossings can lead to:

• Conflict between duty schedules,

environmental/local time, and body time

• Continuous circadian disruption

Flight operations can affect sleep and circadian factors in two main ways: first, by

occurring at unusual or changing times in the day/night cycle, and second, by requiring

time-zone changes. Either of these, and especially the two combined, can have two

basic effects: conflict between external time (environmental or local) and body time;

and continuous circadian disruption.

The body’s time can conflict with environmental time (in the case of unusual/

changing schedules) or local time (in the case of changing time zones). The first case

occurs because night flying is in direct opposition to the circadian clock’s natural

programming for sleep during nighttime, just as sleep during day hours is in opposition

to the circadian clock’s programming for wakefulness during daytime. The second case

occurs due to the wide range of required time changes resulting from successive westeast/east-west flights.

When the body is required to adjust continuously, continuous circadian disruption

can occur. Continual alternation between day and night schedules, for sleep or duty, can

cause the circadian clock to be constantly resetting itself. Successive time-zone changes

can also lead to symptoms of incomplete adaptation. There is currently no information

on the specific effects of continuously resetting the circadian clock in flight operations.
33

Fatigue Countermeasures Program

Effect of Flight Operations

• Extended duty periods

– Prolonged wakefulness

– Fatigue from continuous operations

– Boredom/complacency

• Restricted time available for sleep

– Cumulative sleep debt

An obvious contributor to sleep loss is a prolonged period of continuous wakefulness.

An extended duty period can create fatigue by extending wakefulness and decreasing

sleep, and can involve circadian disruption. Other fatigue factors that can emerge in

continuous operations are boredom and complacency. When a human is acting only as

a passive monitor (e.g., of relatively rare events in highly automated aircraft), there is an

opportunity for these factors to increase the likelihood for physiological sleepiness to

emerge (i.e., the person may fall sleep).

In many flight operations, the time available for sleep is restricted by a variety of

constraints. If an individual’s physiological timing for sleep does not coincide with the

scheduled sleep opportunity, then a cumulative sleep debt can result.
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Fatigue Countermeasures Program

Fatigue Signs and Symptoms

• Forgetful • Fixated

• Poor decisions • Apathetic

• Slowed reaction time • Lethargic

• Reduced vigilance • Bad mood

• Poor communication • Nodding off
35

Fatigue Countermeasures Program

Common

Misconceptions

There are many misconceptions about fatigue in flight operations. Several

commonly held misconceptions will be presented and then addressed using the

information previously presented and additional scientific data.
36

Fatigue Countermeasures Program

Common Misconceptions

“Scheduled rest period allows for required sleep”

• NASA short-haul field study

– The average layover was 12.5 hours long

– Pilots slept about 1hour less per night on trips than at home

– However, pilots had to wake up for duty more than 1 hr earlier than normal

– They could not fall asleep earlier to compensate for the early wake-up

• Sleep laboratory finding

– It is very difficult to fall asleep earlier than usual, except

when cumulative sleep debt overcomes circadian factors

The problem with having to get up earlier than usual is that it is very difficult, if not

impossible, to fall asleep sufficiently early the night before to compensate (even when

the duty schedule permits). It is not simply a question of discipline or motivation. The

circadian clock effectively opposes falling asleep earlier than the habitual bedtime. Just

as there are preferred times in the circadian cycle for falling asleep, there are also times

when sleep onset is very unlikely. These times have been labeled “wake maintenance

zones,” and one of them occurs just before the habitual bedtime. In addition, because

the “biological day” dictated by the circadian clock tends to be longer than 24 hours, it

is easier to go to sleep later than to go to sleep earlier. Going to sleep later also means

staying awake longer, which allows more time for the homeostatic “sleep pressure” to

build up.

An example of the phenomena described above is from a NASA short-haul field

study, which examined 44 pilots in the DC-9 and the B-737. The average layover was

12.5 hours. Yet, despite the fact that 12.5 hours seems an adequate amount of time for

8 or more hours of sleep, pilots slept about 1 hour less per night on trips than at home.

The pilots had to wake up for duty more than 1 hour earlier than usual, and they could

not fall asleep earlier to compensate for the early wake-up.
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Fatigue Countermeasures Program

Common Misconceptions

“Scheduled rest period allows for required sleep”

• NASA long-haul field study conclusions

– The circadian system influenced the timing and duration of sleep

(very similar to subjects living with no environmental time cues)

– There was a clear preference for sleeping during the local night

– The circadian system could not synchronize

to the duty/rest pattern and time-zone changes

• Physiologically, the time available for sleep

is usually less than duration of layover

The information on this slide is based on a NASA long-haul study that also

demonstrates the misconception that the entire rest period is available for sleep. The study

examined 29 pilots in B-747s (each series except 400) during four trip patterns that lasted

5–9 days. The average duty period was 10.3 hours, followed by an average layover of 24.8

hours, resulting in an average rest/duty cycle of 35.1 hours. There were usually two sleep

episodes (total 11.5 hr of sleep) per layover. A provocative finding here is that the average

temperature rhythm for these long-haul pilots was extended to 25.7 hours. This is longer

than the usual 24-hour circadian cycle and longer than the usual free-running rhythm of

24.9 hours. It suggests that after a period of time, the circadian clock could no longer

follow the many time-zone changes and irregular hours of work and rest.

This NASA field study confirms that the circadian clock cannot keep up with the timezone changes and non-24-hour duty/rest cycles experienced by long-haul flight crews. In

addition, a 24-hour sleep/wake cycle is impossible with the average duty/rest pattern of 10

hours of duty followed by a 25-hour layover.

This forced internal desynchronization has a number of important consequences. First,

the bi-circadian (twice per cycle) peaks in sleep tendency can occur in-flight, thus

increasing the risk of inadvertent napping in the cockpit. Second, the part of the circadian

cycle during which sleep normally occurs may or may not be contained within a layover,

and may or may not coincide with local night. The interplay of these factors will have a

major effect on how much sleep flight crewmembers are able to obtain en route and on

layover. Third, the circadian rhythms in digestive function may or may not coincide with

the patterns of meal availability in-flight and during layovers. Gastrointestinal problems

can result from repeatedly eating at inappropriate times in the circadian cycle.
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Fatigue Countermeasures Program

Sleep Loss in Different Flight Operations

6

7

8

9

Average sleep

duration (hr)

Long-haul

Short-haul

Overnight cargo

Pre-trip Trip Post-trip

This graph demonstrates that in each flight operation studied, sleep loss occurred

during trips. Three types of commercial flight operations are portrayed on this graph:

short-haul, long-haul, and overnight cargo. The average hours of sleep obtained pretrip are portrayed for each flight operation on the left. The middle three bars indicate

the reduced sleep obtained, on average, in each type of operation during a trip schedule.

The bars on the right display the average amount of sleep obtained posttrip. The

principal finding is that in most cases any of these three types of flight operations

will engender sleep loss during trip schedules.
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Fatigue Countermeasures Program

Common Misconceptions

• “I know how tired I am”

• “I’ve lost sleep before and I did just fine”

• “I’m motivated enough to just push through it”

Why not?

• It is difficult to reliably estimate your own

alertness and performance

One widely held belief is that individuals can accurately and reliably estimate their

alertness and performance. Many people believe that being motivated, well-trained, and

professional or having previous experience with sleep deprivation prepares them to

combat the physiological consequences of sleep loss. As previously presented,

individuals (especially sleepy individuals) do not reliably estimate their alertness and

performance. The following data from a long-haul pilot illustrate the point.
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Fatigue Countermeasures Program

Subjective vs Physiological Sleepiness

Sasaki et al., 1986

SSS

1

7

4

20

15

10

5

0

4 8 12 16 20

major sleep episode

A

B

MSLT score 

(min)

Local Time (hr)

100

1

50

1 22

Tense/Alert

scale (mm)

Alert

Tense

SSS

MSLT

(mean = 10.51)

2 3 5 6 7 9 10 11 13 14 15 17 18 19 21

These data were obtained in a NASA collaborative study that examined layover sleep

and waking sleepiness during layovers in international long-haul flight crews. This pilot was

asked to rate his overall level of sleepiness throughout the day while simultaneously having

it measured with an objective test of physiological sleepiness. The test of physiological

sleepiness is called the Multiple Sleep Latency Test (MSLT) and is a laboratory standard for

objective evaluation of physiological sleepiness. Essentially, the test defines sleepiness by

the speed of falling asleep: the sleepier the individual, the sooner sleep onset will occur;

the more alert the individual, the longer it will take for sleep onset to occur, if it does at all.

Measurements of brain, eye, and muscle activity can quantify the speed of falling asleep to

within half a second. Individuals have 20 minutes to fall asleep in a quiet, dark room. If they

do not fall asleep, their score is 20 and they are considered very alert. If they fall asleep

immediately, their score is 0 and they are considered very sleepy. This test has been used in

thousands of studies involving sleep-disorder patients and sleep deprivation. Individuals who

are sleep deprived experimentally or who have a sleep disorder that causes waking sleepiness

will fall asleep on this test in 5 minutes on almost every opportunity. This MSLT score of 5 or

less often is referred to as being in the “twilight zone”.

The pilot’s subjective sleepiness scores (SSS = Stanford Sleepiness Scale) are portrayed

on the top half of the graph. The letter A indicates the point when the pilot reported his

greatest level of alertness. The bottom half of the graph portrays his MSLT scores. The letter

B indicates the point directly under A. At this time (when the pilot reported being most alert),

his MSLT score is approaching the twilight zone, and on subsequent MSLT tests, it is clearly

in the twilight zone. This demonstrates the discrepancy between the self-report of sleepiness

and the level of physiological sleepiness. Although reporting peak levels of alertness, this

pilot was approaching the twilight zone and a high level of physiological sleepiness.
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Fatigue Countermeasures Program

Common Misconceptions

“The answer is simple...”

• “There is a quick fix, a magic bullet”

• “One cure will work for everyone, all aircraft, all flight schedules”

Why not?

• Sleep and circadian physiology are complex

• People are not the same

• Different flight schedules present different demands

A misconception that must be dispelled is that there is a “magic bullet” that will cure

the fatigue, jet lag, sleep loss, circadian disruption, and sleepiness engendered by flight

operations. The previous sections have demonstrated clearly the complexities of the

physiological systems and the diversity of effects created by the range of flight

operations. Also, people are not the same, and the range of individual differences in

response to these effects must also be considered.

The idea that there is no magic bullet should be remembered whenever assessing the

latest “cure” for jet lag. Be skeptical and weigh the claims in consideration of the

physiological information previously presented.
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Fatigue Countermeasures Program

Alertness

Management

Strategies
43

Fatigue Countermeasures Program

Important Considerations

• The following recommendations are intended

to help you apply what is currently known

• Tailor them to your own needs

• The best effects may result from combining multiple

strategies rather than relying on a single strategy

It will be continually emphasized that the following strategies are only

recommendations and should be tailored to an individual’s particular needs and

activities. You should experiment with different strategies and evaluate their

effectiveness in the context of your own physiology and specific flight operations.

The best effects may result from combining strategies rather than relying on an

individual strategy.
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Fatigue Countermeasures Program

Alertness Management Strategies

• Preventive strategies

Used before duty and on layovers to reduce adverse effects of

fatigue, sleep loss, and circadian disruption during flight operations

• Operational strategies

Used in flight to maintain alertness and performance

The following is an approach to differentiating alertness management strategies.

Preventive strategies focus on the underlying physiology by attempting to manage and

maximize sleep and promote circadian adaptation. These strategies are used at home

before a trip or during a layover. Operational strategies are in-flight measures that

help to maintain alertness and performance. These strategies do not necessarily affect

the underlying physiological mechanisms, but focus more on managing fatigue during

operations. Primarily, these short-term strategies help to conceal or attenuate

underlying physiological sleepiness.
45

Fatigue Countermeasures Program

Preventive Strategies:

Sleep Scheduling and Quantity

• At home

– Get the best sleep possible before starting a trip

• On a trip

– Try to get at least as much sleep per 24 hours

as you would in a normal 24-hour period at home

• Trust your own physiology

– If you feel sleepy and circumstances permit, then sleep

– If you wake spontaneously and cannot go back

to sleep within 15–30 minutes, then get up

 Prior sleep loss can be a significant factor in the severity of subsequent jet lag

symptoms. That is, individuals who are sleep deprived before a trip can experience

more difficulty than those who are well rested. Consider the previous information

regarding sleep debt and the expected sleep loss associated with flight operations. An

individual who begins a trip with a sleep debt, should expect that the it will only worsen

during the trip schedule. The recommendation is to begin a trip schedule as sleepsatiated as possible. Maximize the amount of sleep at least 1 and preferably 2 days

before departure.

As indicated previously, most flight operations are characterized by sleep loss during

trip schedules. Individuals should attempt to obtain at least as much sleep during a

layover as they would typically during a normal 24 hours at home. Knowing that

circadian and other factors will diminish the physiologically available windows for

sleep, attempts should be made to maximize these opportunities.

Learn to trust your own physiology. When struggling to stay awake, take the

sleepiness as a clear sign to get some sleep. Instead of fighting the sleepiness, take a

brief nap or a longer sleep time. The length of that sleep period will be discussed soon.

Also, if after awakening spontaneously you are unable to return to sleep within 15–30

minutes, then get out of bed. The principal message is that if your brain is giving you

clear signals that you are sleepy, then sleep. If you awaken and you are alert and unable

to return to sleep, get up. You can force wakefulness, but you cannot force sleep.
46

Fatigue Countermeasures Program

Preventive Strategies:

Strategic Napping

Before duty

• A nap can acutely improve alertness

• If immediately before a duty period, limit nap to 45 minutes

• If you sleep too long and go into deep sleep,

it may take longer for you to become fully awake

• Nap can be longer at other times

• A nap will decrease the length of continuous wakefulness

before a duty period; some sleep is better than none

An extensive scientific literature clearly demonstrates the effectiveness of naps in

improving subsequent alertness and performance. One important consideration when

napping close to a duty period is to minimize the chances of going into deep NREM

sleep (stages 3 and 4). If awakened out of deep sleep, an individual may continue to feel

groggy, sleepy, or disoriented for 10–15 minutes. This phenomenon is called sleep

inertia. Therefore, if taking a nap before a duty period, limiting its duration to 45

minutes or less will decrease the chances of having significant amounts of deep sleep.

A brief nap can be an important way to decrease the length of continuous wakefulness.

It is usually much better to get some sleep than none at all.

When you nap at times other than immediately before a duty period, then the nap can

be longer. In this case, a nap longer than 2 hours is likely to get an individual through at

least one NREM/REM cycle.

Strategic napping can be an extremely effective countermeasure in improving

subsequent alertness and performance. Some individuals call these “power” naps. In

flight operations, “NASA naps” have been demonstrated to be an effective acute fatigue

countermeasure.
47

Fatigue Countermeasures Program

Preventive Strategies:

Good Sleep Habits

• Keep a regular sleep/wake schedule; protect sleep time

• Develop and practice a regular pre-sleep routine

• Use bedroom only for sleep; avoid work, worry, exercise

• If hungry, eat a light snack; do not eat or drink heavily before bedtime

• Avoid alcohol or caffeine before going to bed

• Use physical/mental relaxation techniques as needed to fall asleep

• If you don’t fall asleep in 30 minutes, get out of bed

The following recommendations are generally considered important for maintaining

good sleep habits. They apply to everyone. First, keep a regular sleep and wake schedule

as much as possible. At home before trips, try to keep sleep time protected and minimize

other responsibilities. A regularly practiced pre-sleep routine can be used to teach your

mind and body that it is time to relax and fall asleep. A set of cues can be established to

condition pre-sleep relaxation and can then be used anywhere and anytime before going to

sleep. It is important to avoid work or worry in the bedroom and to prevent the association

of the bed with activities contrary to relaxation and sleep.

Going to bed hungry can delay falling asleep. Eating a heavy meal also can disrupt

sleep, for the stomach is busy digesting food. If hungry or thirsty at bedtime, eat a light

snack or have a small quantity of something to drink. As previously mentioned, alcohol

should be avoided immediately before going to bed because of disruptive effects on sleep.

Caffeine consumption should also be limited. Caffeine in coffee, tea, and colas can prevent

sleep onset and disrupt subsequent sleep. Some individuals are sensitive to the caffeine in

chocolate, and even a chocolate dessert after dinner is enough to interfere with their sleep.

Many mild pain relievers also contain caffeine; read the label for ingredient information.

Be sure to stop caffeine intake several hours before planned bedtime.

A variety of mental and physical relaxation techniques are proven to promote sleep

onset and good sleep. Appendix B describes some of these techniques in more detail. Like

any skills, these techniques can be practiced; then they can be used in a wide range of

applications, essentially anywhere. If unable to fall asleep in 30 minutes, don’t lie in bed

trying to fall asleep. Instead, get out of bed and engage in some activity conducive to

relaxation and sleep.
48

Fatigue Countermeasures Program

Preventive Strategies:

Good Sleep Habits

• Sleep environment

– Dark room (if necessary, use mask, heavy curtains)

– Quiet room (turn off phone, use earplugs)

– Comfortable temperature

– Comfortable sleep surface

• Lifestyle

– Exercise regularly (but not too near bedtime)

– Eat a balanced diet

Disruptive environmental factors should be minimized. Sleep in a dark, quiet,

temperature-controlled room, and on a comfortable sleep surface.

Laboratory studies suggest that regular exercisers may have increased amounts of

NREM stages 3 and 4. However, exercising too close to bedtime can disrupt subsequent

sleep. Although physically tiring, exercise elevates heart and breathing rates, and is

generally activating physiologically. Usually, it is not possible to immediately wind

down and fall asleep after exercise. A balanced diet and regular exercise are critical

components for overall good health.
49

Fatigue Countermeasures Program

Operational Strategies

• “...each required flight crewmember on flight deck

duty must remain at the assigned duty station with

seat belt fastened while the aircraft is taking off or

landing, and while it is en route” (FAR requirement)

• What can you do in your cockpit seat?

– Engage in conversations with others

– Do something that involves physical action

– Stretch

 Operational countermeasures are challenged by FARs that require crewmembers to

remain seated at their assigned duty stations with their seat belts fastened. This poses a

challenge because one of the most successful technique for combating sleepiness,

according to the earliest sleep-deprivation experiments, is physical activity. Whenever

possible, engage in physical activity, even if it is only stretching. Take regular stretch

breaks and while seated remain as active as possible—even writing helps. Engage in

conversations with others and be sure to participate; don’t just nod and listen.
50

Fatigue Countermeasures Program

Operational Strategies

• Strategic caffeine consumption

– Use caffeine to acutely increase alertness

– Don’t use it when already alert

(e.g., start of duty or after a nap)

– Avoid caffeine near bedtime

• Be sensible about nutrition and stay hydrated

Caffeine, a stimulant, can be consumed strategically to acutely increase alertness.

It is best not to continually consume caffeine before, during, and after a trip. Instead,

determine the potential periods when caffeine could be used to combat a specific

period of sleepiness (e.g., 3–5 A.M. or 3–5 P.M.). Avoid using it when already alert,

for example, when just beginning a daytime duty period or immediately after a nap.

Though affected by several variables (e.g., body size, previous food intake), caffeine

will usually take 15–30 minutes to take effect and then last for up to 3–4 hours.

Therefore, continually consuming caffeine throughout a flight could interfere with

subsequent sleep on layover. Stop caffeine consumption far enough in advance of a

planned bedtime so that it will no longer be active.

Be sensible about nutrition. Whenever possible, maintain a balanced diet.

Obviously, flight operations can interfere with regularly scheduled, balanced meals.

Try to carry appropriate snacks as needed. Drink plenty of fluids and stay hydrated.

Between reduced cockpit humidity and caffeine (a diuretic), it is easy to become

dehydrated.
51

Fatigue Countermeasures Program

Operational Strategies

• Planned brief nap during long-haul flights

– NASA/FAA study showed that vigilance and physiological

alertness improved after a brief, in-flight nap

– Planned for low-workload portion of cruise

– Up to 40 minutes in duration

– One crewmember at a time

– Three-person non-augmented flights

• Cockpit napping is not currently sanctioned;

Controlled Rest on the Flight Deck under review by FAA

It must be emphasized that controlled rest on the flight deck is NOT currently

sanctioned. A recent NASA/FAA study demonstrated the effectiveness of a brief inflight nap in improving subsequent alertness and performance. As a result, the FAA is

reviewing Controlled Rest on the Flight Deck. A planned brief in-flight nap would be an

operational strategy that directly reduces the physiological sleepiness engendered by

flight operations.
52

Fatigue Countermeasures Program

Future Considerations

• Bright light

– Facilitates rapid circadian adaptation and promotes alertness

– Provocative laboratory findings

– Operational effectiveness still being demonstrated

• Pharmacologic agents

– Continuing search for agents that safely and effectively promote

sleep and maintain alertness and performance during wakefulness

– Melatonin

Facilitates rapid circadian adaptation and promotes sleep

Studies to demonstrate operational effectiveness currently underway

Several potential countermeasures are at various stages of development. Watch for

their possible application to operational environments.

Bright light has been shown in laboratory studies to facilitate rapid circadian

adaptation. Two to three hours of bright light (i.e., 2,500–10,000 lux) administered at

the appropriate phase of the temperature cycle for three successive days may facilitate

an 8- to 12-hour shift of the circadian clock. Separate from its effects on the circadian

clock, bright light also can have an independent alerting effect.

There is a continuing search for pharmacologic agents that safely and effectively

promote sleep and help to maintain alertness and performance during wakefulness.

These agents include both sleeping pills to promote sleep and stimulants to promote

wakefulness.

Recent studies suggest that the hormone melatonin may be useful for facilitating

adaptation of the circadian clock and that it demonstrates sedative effects (i.e., may be

a useful sleep aid). However, there are known cautions associated with melatonin. For

example, it is not controlled by the Food and Drug Administration, and therefore there is

no guarantee of content, dosage, or effectiveness.
53

Fatigue Countermeasures Program

Future Considerations

• Exercise

– Research on animals suggests exercise may facilitate circadian adaptation;

applications in humans being studied

• Diet

– Recent scientific study demonstrated that the Jet Lag Diet

did not help adjustment after multiple time-zone changes

– However, the use of dietary countermeasures deserves more research

• “Anchor sleep”

– Obtaining a portion of layover sleep during your usual home sleep time

– Difficult to predict the anchor sleep “window”

– Currently no demonstration of operational effectiveness

Exercise has been demonstrated to facilitate circadian adaptation in animals, and

applications in humans are being studied currently.

Recent scientific studies have clearly demonstrated that the “Jet Lag Diet” is not

effective in facilitating circadian adaptation.

Anchor sleep may be useful when the usual home sleep period can be determined

reliably. However, it is difficult to predict the home sleep window for two reasons:

1) the individual differences in the circadian system, and 2) circadian resynchronization

after multiple flight segments shifts the window.

There is no one “magic bullet” for eliminating the fatigue, sleep loss, and circadian

disruption currently engendered by flight operations. It will be critical that potential

countermeasures be developed and evaluated in operational environments to demonstrate

their effectiveness. Individuals should be wary of unproved “cures.” These “cures” may

not only be ineffective, but may produce a false sense of security by causing individuals

to think they are managing their fatigue when, in fact, they are not.

However, potential countermeasures are currently being evaluated, and in the future

may provide additional strategies for overall alertness management in flight operations.
54

Fatigue Countermeasures Program

If You Remember Nothing Else...

• Physiological mechanisms underlie fatigue

• Improve current situation — do it yourself now

• Sleepiness can have severe consequences — take it seriously

• People are different — tailor this information to your own needs

• There is no one simple answer — these are recommendations;

find out what works for you

The critical messages to take home...
55

APPENDIX A

BRIEF INTRODUCTION TO SLEEP DISORDERS AND SLEEPING PILLS

Physical Sleep Disorders

There are several physical sleep disorders that can disturb sleep and cause excessive sleepiness during

wakefulness. Two examples are described that illustrate why it is important to know about the

existence of these medical disorders: sleep apnea and nocturnal myoclonus.

These are only two examples of sleep disorders, physiological conditions that can disrupt the quantity

and quality of sleep and can have subsequent consequences during wakefulness. Sleep disorders often

can exist without the knowledge of the individual sufferer and may produce waking difficulties that

one would not typically relate to a sleep problem (e.g., high blood pressure, morning headaches,

fighting sleep in many situations). It is imperative that health care professionals, especially accredited

sleep-disorder specialists, be used to accurately determine the cause of sleep disturbances or the related

waking difficulties, so that individuals receive appropriate and effective treatment.

Sleep Apnea

The sleep apnea syndrome (SAS) is a sleep disorder in which individuals cannot sleep and breathe

at the same time. Apnea (a = not, pnea = breathing) is a pause in the regular pattern of breathing.

Essentially, apneic individuals fall asleep and then periodically stop breathing. When this occurs, little

or no oxygen is available to the brain or body. Usually, when the oxygen level in the blood drops

below a certain level and carbon dioxide levels rise, the brain arouses the individual who then begins

to breathe again. This awakening is often associated with a gasp for air or a snore as the individual

resumes breathing. Depending on the severity of the disorder, this cycle of pauses in breathing and

awakening to breathe can continue throughout the sleep period. Sleep apnea is a potentially lethal

disorder—if the brain does not respond during an apnea, death can occur. There are two aspects of

apneic episodes that affect the severity of the disorder: the duration of the apnea and the frequency (the

number that occur during a given sleep period). Most apnea episodes usually last under 30 sec, though

they can range from 15 sec up to 2 or 3 min in duration. Apneas may occur only a few times per hour

of sleep or hundreds of times across a sleep period. In a very mild case, there may be only 5 or

10 apnea episodes per hour, whereas in a severe case there may be 50 to 80 per hour of sleep (i.e.,

300 or 400 episodes during an average sleep period).

Many physical and behavioral problems can be caused by sleep apnea, for example, excessive

sleepiness and cardiovascular difficulties such as hypertension. Currently, sleep-disorder specialists

believe that a combination of frequent arousals from sleep (which also results in little or no deep sleep)

and the oxygen deprivation lead to excessive sleepiness during wakefulness. Remember, the quality of

sleep is an important factor in how refreshed and alert an individual feels after sleep. So, although

someone with sleep apnea may sleep 8 hours, the sleep could be disturbed 300 or 400 times by apnea

episodes, and therefore the quality of sleep can be very poor. Very often individuals with sleep apnea

are completely unaware that they have the disorder. They may have high blood pressure during the day

or problems staying awake because of excessive sleepiness, but they often do not relate this to a sleep
56

problem. Thus, even persons who are awakened hundreds of times a night because of disturbed

breathing may awaken the next morning and be unaware of what has happened. Frequently, a bed

partner is the first to notice the repeated pauses in breathing during sleep and, depending on their

duration, may become quite concerned.

Epidemiologic studies suggest that 3–4% of the general population and 10–15% of males had sleep

apnea (depending on the definition used). The occurrence of the disorder and its severity appear to

increase with age. The textbook sleep apnea case is an overweight, middle-aged male who snores, has

high blood pressure, and has problems staying awake during the day (e.g., fighting sleep while in

meetings, reading, driving a car, watching a movie or TV). There are a variety of reasons unrelated to

sleep apnea that can cause people to snore, for example, colds, deviated septa (i.e., physical problems

with the structure of the nose), and allergies. However, snoring is also a primary symptom associated

with the occurrence of sleep apnea. Another caution is that alcohol, sleeping pills, and sleep loss can

worsen the severity of sleep apnea (both the duration and frequency of apnea events).

A number of options are available to effectively treat the sleep apnea syndrome. The treatment usually

depends on the severity of the disorder and can range from losing weight, to the continuous administration of oxygen during sleep, to surgery. It is critical that someone concerned about sleep apnea be

evaluated by an appropriate health care professional. An individual should first consult a personal

physician. Also, there are now sleep-disorder specialists who perform sleep-disorder evaluations,

make diagnoses, and prescribe treatments. There are also specialized sleep-disorder clinics (accredited

by the American Sleep Disorders Association) throughout the United States that provide full diagnostic

and treatment services for the range of sleep disorders. These clinics are located in many university

and community hospitals throughout the country.

Sleep apnea is an example of a medical disorder that can disturb sleep and cause excessive sleepiness,

heart and blood pressure problems, and other difficulties during wakefulness. An individual can be

completely unaware of the sleep disturbances and yet every night suffer from a disorder that can cause

pathological sleepiness during the daytime. Like any medical problem, sleep apnea should be evaluated

and treated by qualified medical specialists, using the approaches currently accepted for successful

treatment of the disorder.

Nocturnal Myoclonus or Periodic Leg Movements

Another physical sleep disorder that can disturb the quality of sleep is nocturnal myoclonus, or

periodic leg movements during sleep. This disorder is characterized by a twitching (or muscular

contraction) of the lower leg muscles during sleep (though typically found in the lower legs, the arms

could also twitch). The twitch can occur in one leg or both, typically last only about 0.5 sec, and

appear in periodic episodes across the sleep period. There can be several hundred twitches during any

given sleep period. Periodic leg movements constitute a sleep disorder because each muscular twitch is

usually associated with either an awakening or a shift from deep to light sleep. Again, someone could

be getting 8 hr of sleep but have that sleep interrupted 300 times with awakenings. This poor quality

sleep can translate into complaints of non-restorative sleep, awakening unrefreshed, tired, sleepy, etc.

This is another sleep disorder that can go unrecognized by the individual with the periodic leg movements and one that is often noticed first by a bed partner (often the recipient of multiple kicks during

sleep!). Again, it is very important that the disorder be diagnosed and treated by a knowledgeable
57

physician or accredited sleep-disorder specialist. Although not life-threatening like sleep apnea,

periodic leg movements during sleep can result in excessive daytime sleepiness.

Medications

Alcohol

The most widely used self-treatment for disturbed sleep is alcohol. As noted in the presentation

materials, alcohol is a very potent REM sleep suppressant. More than a couple of beers or glasses of

wine can totally suppress REM sleep in the first half of a sleep period. During the second half of the

sleep period, withdrawal effects can be seen, including awakenings, a REM rebound, and generally,

very poor, disrupted sleep. Although alcohol is often used to unwind, relax, and promote the ability to

get to sleep, its disruptive effects on the subsequent sleep will outweigh its usefulness in promoting

the onset of sleep.

Sleeping Pills

CAUTION

The other widely used approach to treating sleep disturbances is

prescription sleeping pills. The use of prescription sleeping pills close to

and during duty periods is not medically allowed. However, it is

acknowledged that many medications available only by prescription in the

United States can be obtained over-the-counter, without prescriptions, in

many overseas locations. Sleeping pills should only be used under the

supervision of a knowledgeable physician. The information provided here

is intended only to give a basic understanding about their effects.

There are several important characteristics of sleeping pills that should be considered. The primary

purpose of a sleep medication should be to promote sleep, either by facilitating sleep onset or by

helping to maintain sleep (e.g., reducing frequent or long awakenings). It should maintain this positive

therapeutic effect for the duration of its use (i.e., sleep should be as good on the fifth night of use as

on the first). The improvement in sleep should be associated with waking benefits (e.g., increased

alertness, better mood) and, at the very least, the sleeping medication should not impair waking

function. So the optimal sleeping pill should promote sleep and improve subsequent waking function.

A very important consensus statement (from physicians, sleep-disorder specialists, etc.) recommends

that the safest and most beneficial use of sleeping pills is obtained when they are taken for short

periods of time and at the lowest effective dose.

In the past, some of the most widely used prescription sleeping pills were in a class of drugs called

barbiturates. These include medications such as pentobarbital and seconal. Scientific studies in sleep

laboratories have shown that the barbiturates often lose their effectiveness to promote sleep within

7–10 days and can create tolerance to, and dependence on, the medication. It is important to keep in

mind that barbiturates have been found to be factors in accidental or intentional drug overdose. The

barbiturates are also potent REM sleep suppressants and, like alcohol, can disrupt the regular cycle of

NREM and REM sleep, creating fragmented and poor quality sleep. Eventually, these medications can
58

actually create an insomnia problem called drug-dependent insomnia. Only after careful tapering off and

eventual withdrawal of the medication can sleep return to a more normal pattern. As prescribing

physicians have learned more about these sleep laboratory findings regarding barbiturates, their use

as a primary sleeping medication has rapidly declined, and they are rarely used today.

Today, the most widely prescribed sleeping pills (often called sedative/hypnotic medications) are in a

class of drugs called the benzodiazepines. There are three that are commonly prescribed: Halcion

(triazolam), Restoril (temazepam), and Dalmane (flurazepam). Sleep-laboratory tests of these three

medications show that they promote sleep over many nights in sleep-disturbed patients. They are

usually considered safer than the barbiturates because, generally, it is more difficult to accidentally or

intentionally overdose with them and they can be more easily started and stopped with fewer negative

effects.

The benzodiazepines, like all medications, are not without their adverse side-effects. Although the

benzodiazepines do not suppress REM sleep, they can suppress NREM sleep stages 3 and 4 (the deep

sleep that occurs in the first third to half of the sleep period). Reports suggest that the benzodiazepines

can have side effects that affect short-term memory and, if withdrawn too rapidly, may cause a

rebound anxiety or insomnia. In spite of these considerations, the benzodiazepines are widely used

as safe and effective sleeping pills when prescribed by a knowledgeable physician.

There are properties of these three benzodiazepines that distinguish their effects from one another.

The primary factor is their half-life, that is, the amount of time the drug continues to work in an

individual’s body. Halcion is a short-acting benzodiazepine (about 2–4 hr) that helps to promote sleep

onset but is no longer active by the middle to end of a sleep period. In sleep laboratory studies,

Halcion has been shown to effectively improve nocturnal sleep and to be associated with improved

daytime alertness. There have been several scientific studies that showed Halcion to be effective for

travelers using it as an aid to improve sleep on trips that involve multiple time-zone changes. Restoril

is a medium-acting benzodiazepine (about 8 hr) that helps to maintain sleep throughout a night and is

no longer active by the morning awakening. Dalmane is a long-acting benzodiazepine (about 100 hr)

that effectively promotes sleep onset and maintains sleep throughout the night. However, if used over

several nights, the long half-life results in an accumulation of the medication in the body that can have

effects that carry over to wakefulness. Laboratory studies have shown that after several nights of

administration, the build-up of Dalmane metabolites can be associated with increased sleepiness during

wakefulness. It should be noted that the specific formulations of these medications can be different

overseas. For example, Restoril obtained in the United Kingdom has a half-life of 5–6 hr.

Recently, a new prescription sleep medication, Ambien (a non-benzodiazepine), has been receiving

attention as a safe and effective sleep aid.

The main message is that the benzodiazepines can be used effectively to help get to sleep and stay

asleep. They have different properties that should dictate the appropriate use of the medications for

different people in different circumstances. Finally, all of these are prescription medications that

should only be used under the care and guidance of a qualified and knowledgeable physician.
59

Note

The information provided here is intended only to provide examples of

sleep disorders and some of the medications used to promote sleep. You

should not use this information to diagnose, medicate, or treat yourself. If

you have any questions about your health, potential sleep disorders, or

medication, see your physician. As indicated, accredited sleep clinics and

sleep-disorder specialists are available for evaluation, diagnosis, and

treatment for the range of sleep disorders. Seek them out by contacting a

local university or community hospital for a referral. The general readings

in appendix E suggest other sources of information about sleep, circadian

rhythms, and sleep disorders.

61

APPENDIX B

BRIEF INTRODUCTION TO RELAXATION SKILLS

Flight operations can involve hectic schedules, significant responsibilities, and stressful events.

Outside of flight operations, many people’s lives also are affected by these factors. Scientific studies

have demonstrated that these “life stresses” can affect an individual’s physical and mental health.

People respond to the perceived demands and challenges of situations differently: some individuals

will become physically tense, others will worry, and so on. There are many situations in which pilots

need to “unwind” and relax after coming off duty. This is especially important when they are preparing

for a layover sleep period. As previously mentioned, alcohol is sometimes used to relax after duty, but

it can significantly disrupt the subsequent sleep period (see appendix A). However, there are alternatives to alcohol. Many people use exercise, hobbies, and many other strategies to physically and

mentally relax. This section is not intended to cover the full range of those options; entire books have

been written on the subjects of stress management and relaxation skills. However, it is intended to

briefly introduce some information about relaxation skills that may be useful in your efforts to relax

and promote sleep.

Relaxation skills can be powerful techniques for promoting physical and mental relaxation in almost

any situation or environment. Many relaxation skills have been scientifically tested and their effectiveness demonstrated in many different areas, from eliminating physical problems (e.g., tension

headaches) to decreasing worry and anxiety to promoting good sleep.

There are a wide variety of relaxation skills that are practiced and effectively used by many individuals.

Some relaxation techniques are primarily cognitive (i.e., involve focusing the mind, internally repeating phrases, etc.), others are primarily physical (e.g., tensing and relaxing the major muscle groups of

the body), though most involve both cognitive and physical components (e.g., after tensing and

relaxing a muscle, mentally focusing on the relaxation).

Examples of techniques that are primarily cognitive include meditation, positive imagery, and

autogenic training. Meditation is one of the oldest relaxation methods and involves sitting quietly,

repeating a phrase (individually chosen), and focusing on deep relaxation. Positive imagery often

begins with guided imagery; an individual chooses a specific, relaxing scene and is guided through the

pleasant images associated with the experience. Autogenic training involves repeating standard phrases

as an individual cognitively focuses on each of the major muscle groups of the body (e.g., “my right

hand is heavy and warm”).

Examples of techniques that involve more physical action include yoga, deep breathing, and

progressive muscle relaxation. Yoga is also a very old method for relaxing the body and mind; it

involves a set of standardized movements and a cognitive component. Rather than short breaths

primarily involving chest breathing, relaxation through deep breathing uses long, slow breaths that use

both the abdomen and chest. During the deep breathing a word or phrase associated with relaxation is

used to focus the mind and facilitate a deeper state of relaxation. Progressive muscle relaxation is a

technique that has received much attention and is effectively used in a wide range of applications. It

involves the systematic tensing and relaxing of the muscles, starting at the head and neck and moving
62

all the way to the toes. The mind focuses on the difference between the tension and the relaxation

associated with the release of the muscle.

It is important to think of these as relaxation skills. As skills, they can be taught, learned, and

practiced. Practice is critical! Too often people try to quickly learn some technique and then use it in

efforts to relax the next time they are in a highly stressful situation. Usually it does not work and the

individual decides that the technique, and relaxation skills in general, are ineffective. Only after a skill

has been mastered should it be applied, and even then it should be gradually tested for its effectiveness

and usefulness in different situations. Eventually, relaxation skills are most effective when they are

practiced on a regular basis and incorporated as a daily activity.

There are many different ways to learn relaxation skills and today many commercially produced

resources are available. It is often useful to first read about a technique and a description of the specific

skill. An external source (e.g., instructor, book, tape) that guides an individual through a particular

technique can be useful in learning the skill and in focusing attention on the relaxation. Eventually, it is

important to internalize and memorize the specifics of the skill. Once learned very well, an individual

should be able to use his or her favorite, most effective relaxation skills in different situations and

environments, without having to rely on an external source to help relax.

Relaxation skills can be a powerful tool to help individuals reduce physical tension, focus and relax the

mind, and promote good sleep. If you decide to try some of these new skills, keep an open mind,

practice, and enjoy learning to relax.

Note

There are many outrageous and unsubstantiated claims made regarding a

wide

range of techniques, devices, and approaches to relaxation. Please be wary!

Today, many local health care facilities, hospitals, and licensed health care

providers (e.g., physicians, psychologists, nurses, social workers) provide

classes on relaxation skills or stress management techniques. Do some

checking to be sure that reputable (e.g., accredited or licensed) practitioners

are providing the services and instruction.

The following references are recommended for further reading on relaxation skills and stress

management. This is not an inclusive list of available resources but it does provide some guidance for

a starting point. These books should be available at your local community library, college library, or

bookstores.

Recommended Readings

Benson, H. (1976). The relaxation response. New York, NY: Avon Books.

Bernstein, D.A. and Borkovec, T.D. (1973). Progressive relaxation training: A manual for helping

professions. Champaign, IL: Research Press.

Coates, T.J. and Thoresen, C.E. (1977). How to sleep better: A drug-free program for overcoming

insomnia. Englewood Cliffs, NJ: Prentice-Hall, Inc.
63

Farquhar, J.W. (1978). The American way of life need not be hazardous to your health.

Stanford, CA: Stanford Alumni Association.
64

APPENDIX C

NASA AMES FATIGUE COUNTERMEASURES PROGRAM

Relevant NASA Technical Memoranda Operational Summaries

from the “Crew Factors in Flight Operations” Series

This appendix comprises the operational summaries of five relevant NASA Technical Memoranda

(TMs) from the Fatigue Countermeasures Program.

Gander, P.H., Graeber, R.C., Foushee, H.C., Lauber, J.K., and Connell, L.J.

(in press). Crew factors in flight operations: II. Psychophysiological responses

to short-haul air transport operations. (NASA Technical Memorandum). Moffett

Field, CA: National Aeronautics and Space Administration. .................................. 65

Graeber, R.C. (Ed.) (1986). Crew factors in flight operations: IV. Sleep and

wakefulness in international aircrews. (NASA Technical Memorandum No. 88231).

Moffett Field, CA: National Aeronautics and Space Administration. ......................... 68

Gander, P.H., Barnes, R., Gregory, K.B., Connell, L.J., Miller, D.L., and

Graeber, R.C. (1994). Crew factors in flight operations VI: Psychophysiological

responses to helicopter operations. (NASA Technical Memorandum No. 108838).

Moffett Field, CA: National Aeronautics and Space Administration. ......................... 72

Gander, P.H., Graeber, R.C., Connell, L.J, and Gregory, K.B. (1991). Crew factors

in flight operations: VIII. Factors influencing sleep timing and subjective sleep

quality in commercial long-haul flight crews. (NASA Technical Memorandum

No. 103852). Moffett Field, CA: National Aeronautics and Space Administration......... 74

Rosekind, M.R., Graeber, R.C., Dinges, D.F., Connell, L.J., Rountree, M.S.,

Spinweber, C.L., and Gillen, K.A. (1994). Crew factors in flight operations IX:

Effects of planned cockpit rest on crew performance and alertness in long-haul

operations. (NASA Technical Memorandum No. 108839). Moffett Field, CA:

National Aeronautics and Space Administration................................................. 77
65

Crew Factors in Flight Operations II: Psychophysiological Responses

to Short-Haul Air Transport Operations

Gander, P.H., Graeber, R.C., Foushee, H.C., Lauber, J.K., and Connell, L.J. (in press). Crew

factors in flight operations: II. Psychophysiological responses to short-haul air transport

operations. (NASA Technical Memorandum). Moffett Field, CA: National Aeronautics and Space

Administration.

Operational Overview

This report is the second in a series on the physiological and psychological effects of flight

operations on flight crews, and on the operational significance of these effects. This overview presents

a comprehensive review and interpretation of the major findings. The supporting scientific analyses are

described in detail in the rest of the text.

To document the psychophysiological effects of flying commercial short-haul air transport

operations, 74 pilots from two airlines were monitored before, during, and after 3-day or 4-day trip

patterns. All flights took place on the East Coast of the United States and data were collected

throughout the year. Eighty-five percent of the pilots who had been awarded the trips selected for

study agreed to participate. The population studied was experienced (average age 41.3 yr, average

airline experience 14.6 yr) and averaged 68.6 hr of flying per month in all categories of aviation.

Subjects wore a portable biomedical monitor which recorded core-body temperature, heart rate,

and wrist activity every 2 min. They also rated their fatigue and mood every 2 hr while awake, and

recorded sleep episodes, naps, showers, exercise, duty times, food and fluid intake, voidings,

cigarettes, medications, and medical symptoms in a daily logbook. A background questionnaire was

administered which included basic demographic information, sleep and life-style habits, and four

personality inventories. A cockpit observer accompanied the crews on the flight deck and kept a

detailed log of operational events.

The trips studied were selected to provide information on the upper range of fatigue experienced by

pilots in predominantly daytime and evening operations. Common features were early report times and

long duty days with multiple flight segments (average 5.5 per day). Daily duty durations averaged

10.6 hr which included, on average, 4.5 hr of flight time. One third of all duty periods studied were

longer than 12 hr. The mean rest-period duration, as defined by the pilots in their daily logs, was

12.5 hr. The mean rest-period duration calculated from the last wheels-on of one duty day to the first

wheels-off of the next duty day was significantly longer (14.0 hr). Overnight layovers after successive

duty days occurred progressively earlier across most trips.

On trip nights, subjects reported taking about 12 min longer to fall asleep, sleeping about 1.2 hr

less, and waking about 1.4 hr earlier than on pretrip nights. They also rated their sleep on trips as

lighter and poorer overall, and reported significantly more awakenings. In contrast, in the laboratory,

sleep restriction results in more rapid sleep onset and more consolidated sleep. The longer sleep

latencies and more frequent awakenings reported by pilots on trips may reflect the commonly reported
66

need to “spin down” after coming off duty and the disruptive effects of sleeping in unfamiliar environments. The fact that sleep during trips was reported not only as shorter but also as more disturbed,

suggests that the effects of this sleep restriction on subsequent daytime sleepiness, performance, and

mood may be greater than those reported in laboratory studies with similar levels of sleep restriction.

The effects of duty demands on subjective fatigue and mood are most clearly seen in the

comparisons of ratings made pretrip, during flight segments, during layovers, and posttrip. During

layovers, fatigue and negative affect were rated as highest and positive affect and activation as lowest.

Positive affect was rated as highest during flight segments, even though fatigue ratings were higher

than for either pretrip or posttrip. Posttrip recovery was indicated by return of fatigue levels to

baseline, the lowest negative affect ratings, and the highest levels of activation. Significant time-of-day

variations were found in fatigue, negative affect, and activation. Fatigue and negative affect were low

in the first three ratings after awakening, and rose thereafter to reach their highest daily values in the

final rating before sleep. As expected, activation showed the opposite time-of-day variation. No

significant relationships were found between the timing, duration, or flight hours in a duty period and

the fatigue and mood during layovers. This may well have been because of the high levels of

individual variability in these ratings.

The use of tobacco did not change on trip days relative to pretrip and posttrip days. However,

significantly more caffeine and alcohol were consumed on trips. Additional caffeine consumption

occurred primarily in the early morning, associated with the earlier wake-up times on trips, and also

around the time of the mid-afternoon peak in physiological sleepiness. The urge to fall asleep at this

peak time would increase progressively with the accumulating sleep debt across trip days. The

additional alcohol consumption may be assumed to have occurred after coming off duty and before

going to sleep. The common practice of using alcohol to relax before sleep is not recommended.

Although alcohol may facilitate falling asleep, it has well-documented disruptive effects on sleep which

can adversely affect subsequent waking alertness and performance. There were no significant changes

in the use of medications, or in the number of reports of medical symptoms between trip days and

pretrip or posttrip days. Similarly, the number of exercise sessions reported was no different on trip

days than on pretrip or posttrip days.

The number and timing of meals on trip days was not significantly different from pretrip or

posttrip days. However, more snacks were eaten, and they were eaten earlier, on trip days. This

suggests that meals on trip days may have been smaller or less filling than meals on pretrip or posttrip

days.

Heart rates during takeoff, descent, and landing were compared with values during mid-cruise for

72 pilots during 589 flight segments. Increases in heart rate were greater during descent and landing

for the pilot flying. The difference between flying and not flying during descent was greater for first

officers than for captains. Heart-rate increases were greater during takeoff and descent under instrument flight conditions than under visual flight conditions. On the basis of similar findings, the number

of segments flown per day should be regulated.

A number of ways of reducing fatigue during short-haul air-transport operations are suggested by

this study. First, since daily duty durations were more than twice as long as daily flight durations, and

since about one third of all duty periods were longer than 12 hr, it would seem reasonable to limit duty
67

hours in addition to, flight hours in short-haul operations. There may also be some advantage to

defining the rest period more precisely, since significant variability is possible within the present

system of definition by contract negotiation. Second, the practice of requiring early report times

makes it more difficult for pilots to obtain adequate sleep, even during relatively long layovers.

This is because circadian rhythms impede falling sleep earlier than usual, except after major sleep loss.

Third, in the trips studied, duty began progressively earlier across the days of the trip. Because of the

difficulty of falling asleep earlier, this has the effect of progressively shortening the time available for

sleep across the days of the trip. In addition, because the innate “physiological day” determined by the

circadian system is longer than 24 hr, it adapts more readily to schedule delays than to advances.

Thus, where possible, successive duty days should begin progressively later. Fourth, the widespread

use of alcohol as a means of relaxing before going to sleep has deleterious effects on subsequent sleep.

It thus seems likely that the quality of sleep on trips could be improved in many cases by providing

pilots with information on alternative relaxation techniques which have been well-tested in the

treatment of sleep disorders.
68

International Cooperative Study of Air Crew Layover Sleep

Graeber, R.C. (Ed.) (1986). Crew factors in flight operations: IV. Sleep and wakefulness in

international aircrews. (NASA Technical Memorandum No. 88231). Moffett Field, CA: National

Aeronautics and Space Administration.

Operational Overview

The major goals of this research were to examine the changes in sleep associated with flights

across multiple time zones and, if necessary, to suggest recommendations for improving such sleep.

Flight crews were studied during the first layover after long flights crossing seven to nine time zones.

The basic findings can be best described in terms of flight direction and discussed with respect to

strategies used by crew members to obtain sufficient sleep before operating the return flight home.

Westward Flights

There was clear evidence that crew members experienced less sleep difficulties during layovers

following westward flights (LHR-SFO, FRA-SFO, SFO-NRT) than after eastward flights. Following

the westward flights almost all subjects went to bed soon after arrival. During the first night, sleep

appeared to be of generally good quality and not unduly disturbed except for increased wakefulness

during the second half of the night. In comparison with baseline, subjects generally fell asleep faster

and slept essentially the same amount as at homebase. Some even reported better sleep quality.

During the next day, the increase in alertness usually seen during the late afternoon in local

individuals was not observed. Instead, drowsiness continued to increase during the remainder of the

wake span. By the second night, there was already some adaptation of sleep to the new time zone as

indicated by even fewer awakenings occurring during the early morning hours.

Nevertheless, on the following day, the previous day’s pattern of increasing drowsiness was seen

in crews who were available for testing. Most crew members successfully attempted to take a preflight

nap in preparation for duty that afternoon. The same findings held for the one group of subjects whose

layover lasted approximately 25 hr instead of the usual 48 hr. The only major difference was that their

preflight nap occurred during the first afternoon after arrival.

The strategy of taking a nap before departure after a westward layover appears important in view

of the coming night flight with its prolonged period of wakefulness. Recent research suggests that

such a nap will help reduce in-flight drowsiness and avoid potential performance deficits. A second

aspect of planning strategies to cope with this flight schedule emphasizes the potential importance of

time of the latter part of flight in relation to the crew members’ circadian rhythms. Additional results

obtained from some crews during the eastward return flight suggest that alertness improves as the

circadian rhythms in body temperature and heart rate begin to rise. Therefore, certain schedules may be

more desirable if they facilitate a nap before night and take advantage of the circadian rise in alertness

during the latter part of the flight.
69

Eastward Flights

Sleep patterns were much more variable and fragmented after eastward night flights (NRT-SFO,

SFO-LHR, SFO-FRA) than after westward flights across an equivalent number of time zones. There

appears to have been a powerful influence which fractionated sleep, probably dependent on the

difficulty which individuals experienced in shortening their day. Furthermore, the consequences of

sleep pattern fragmentation were reflected in subsequent measures of daytime drowsiness.

Many crew members went to bed as soon as possible after arrival and fell asleep more quickly than

observed during baseline but slept a relatively short amount of time even after a long overnight flight.

Subjects tended to awake spontaneously at a time corresponding to the late morning of their home

time. Overall, this strategy can be beneficial; however, the onset of the next major sleep varied

considerably among individuals, with some crew members from each airline delaying sleep until it

coincided with their usual bedtime at home. Similar wide-ranging differences were seen in the second

night’s sleep and intervening sleeps. In spite of a high degree of variability, sleep duration was usually

shorter than baseline and subjectively worse.

Given the usual importance attributed by flight crews to obtaining “good” sleep immediately before

a flight, these data suggest that their chance of doing so could be substantially improved by adhering to

a more structured sleep schedule. In order to optimize sleep during an eastward layover of 24 hr or

multiples thereof. It would be important to limit sleep immediately after arrival and prolong the

subsequent wakeful period to end around the normal local time for sleep. This process would increase

the likelihood that the sleep immediately preceding the next duty period would be of adequate duration

for these operations. It appears that proper sleep scheduling during the first 24 hr is most critical and

that crew members should develop the discipline to terminate sleep even though they could sleep

longer.

Several subjects attempted the strategy of trying to maintain a sleep schedule based on home time.

For the schedules under study, this practice would appear to be less desirable since it would produce a

substantially shorter sleep span immediately before departure; however, this approach could not be

adequately evaluated due to the relatively small number of subjects who used it.

Unless layover sleep is arranged in a satisfactory manner by an appropriate sleep-wake strategy,

increased drowsiness is likely to occur during the subsequent long-haul flight. Other research suggests

that under acceptable operational circumstances. Limited duration naps can be a helpful strategy to

provide refreshment and improve alertness for a useful period of time. Although we do not have the

appropriate data to address this issue directly, flight deck napping could be an important strategy if

operationally feasible.

Individual Factors

While the subjects as a whole did not exhibit serious sleep problems, certain individual crew

members did experience some difficulty. Further investigation of these data is required before any

clarifying statement can be made regarding the factors responsible for this situation. Such work is

currently under way.
70

Age is one individual factor which appears to have been important in this study. Older persons

tend to experience more difficulties obtaining undisturbed sleep, and this was seen in the aircrew

during baseline and layover recordings. Less restful sleep is a feature of growing older and begins to

affect individuals in middle age. Surprisingly little is known about the nature and prevalence of less

restful sleep over this important span of life, but the data obtained from these flight crews has highlighted the need for normative data in a similar age group of individuals who are usually involved in

highly skilled and responsible occupations. These data are now being collected and may be helpful in

understanding why some individuals in this age group have difficulty in adapting to unusual hours of

work and rest. This issue may be relevant to the practice of occupational medicine.

Finally, in one group of pilots, preliminary analyses suggest that other individual factors may

contribute to the crew member’s response to layover sleep requirements. Although this evidence is

currently limited to differences in daytime sleepiness in morning- versus evening-type individuals, it

underscores the potential usefulness of factors related to personality and lifestyle as predictors of

individual reactions to multiple time zone flights.

Study Limitations

Although these results have direct implications for air carrier operations, they must be viewed

within the context of several limitations inherent in the study design. Most important is the fact that

relatively uncomplicated trip patterns were studied. All but one of these trips involved an immediate

return to the home time zone after the layover. The primary data were obtained from crew members

during the first layover stay following an initial outbound flight. One group of subjects provided

additional data upon return to homebase.

At present, such trips are not typical of most international flight crew duty schedules, which

usually involve multiple flight segments and layovers in different time zones before return home;

nevertheless, the trips under examination represent an important type of schedule which is becoming

more prevalent.

Although the alterations in sleep were not considered to be of operational significance in the

present schedules, it is nevertheless possible that the pattern of disturbed sleep would lead to cumulative sleep loss if the schedule were longer or if complete recovery of sleep were not attained before the

next trip. The latter possibility is supported, at least in part, by the observation that baseline sleep was

reduced in some subjects, though this may have also been due to other factors such as early rising.

Furthermore, all flights occurred during late summer or early fall, which did not permit us to examine

seasonal influences, particularly the length of daylight versus darkness, which may also be an

important operational factor.

Secondly, the relatively limited sample sizes may not be representative of the flight crew

population as a whole. In this regard, it is clear that the groups differed considerably in age and

possibly may have differed along other dimensions related to the voluntary nature of their participation. Third, spending a layover at a sleep laboratory may not be equated with staying at a crew hotel.

However, sleep log results from two participating groups of crew members suggest that sleep-wake

patterns differ little under these two conditions.
71

Finally, a potentially more serious problem stems from the difficulty we experienced in obtaining

baseline data immediately preceding the trip. Except for one airline, baseline data could only be

obtained whenever the volunteers were available following at least three non-flying days. Consequently, these measurements often preceded or followed the trip by a week or more. Thus, any

conclusions relating to baseline sleep must be tempered by the realization that the actual sleep obtained

during the nights immediately prior to flight might have differed from that measured in the homebase

laboratory and may have been confounded by the residual effect of the previous flight schedule,

particularly if the preceding trip involved an eastward flight direction.

Regardless of these interpretative issues, the data revealed a high degree of similarity and

consistency among the different flight crew samples despite significant differences in culture, age,

and airline operational practices. Consequently, it is likely that the overall results apply to a wide

spectrum of long-haul crew members and carriers.
72

Crew Factors in Flight Operations VI: Psychophysiological Responses

to Helicopter Operations

Gander, P.H., Barnes, R., Gregory, K.B., Connell, L.J., Miller, D.L., and Graeber, R.C. (1994).

Crew factors in flight operations VI: Psychophysiological responses to helicopter operations.

(NASA Technical Memorandum No. 108838). Moffett Field, CA: National Aeronautics and Space

Administration.

Operational Overview

This report is the sixth in a series on the physiological and psychological effects of flight

operations on flight crews, and on the operational significance of these effects. This section presents

a comprehensive review of the major findings and their significance. The rest of the volume contains

the complete scientific description of the work.

Thirty-two helicopter pilots (average age 34 yr) were studied before, during, and after 4- to 5-day

trips providing support services from Aberdeen, Scotland, to rigs in the North Sea oil fields. Duty

days began and ended in Aberdeen. Half the trips studied took place in winter/spring, and the other

half in summer/autumn. Heart rate, rectal temperature, and activity of the nondominant wrist were

monitored continuously by means of portable biomedical monitors. Subjects kept daily logs of sleep

timing and quality, food and fluid intake, medications taken, and medical symptoms. They also rated

their fatigue and mood every 2 hr while awake. For every segment flown, they rated their workload

(on a modified Bedford Scale) for each phase of flight, and rated five different environmental factors

assumed to influence workload, that is, functioning of the aircraft systems (on a 5-point scale from

perfect to useless); and weather conditions for landing, the landing site, letdown aids, and air-traffic

control (each on a 5-point scale from very favorable to very unfavorable).

On trip mornings, subjects were required to wake up about 1.5 hr earlier than on pretrip mornings

(average on-duty time 0725 local time). Although they came off duty relatively early (average 1437

local time), they averaged only 6.4 hr of sleep during layovers at home that averaged almost 17 hr.

The inability to fall asleep earlier than the habitual bedtime is due to properties of the physiological

mechanisms controlling sleep. Subjects were thus unable to compensate for the early wake-ups, and

therefore averaged about 50 min less sleep per night on trips than on pretrip. In the laboratory, 1 hr per

night of sleep restriction has been shown to accumulate and to progressively increase daytime sleepiness. Sleep was rated as better overall posttrip than on trip nights and deeper posttrip than pretrip, as is

typical during recovery from sleep loss. Delaying the start of on-duty times (by 1.5–2 hr on average)

would be expected to produce a significant improvement in the amount of sleep pilots are able to

obtain, and should be given serious consideration.

Pilots reported more fatigue on posttrip days than on pretrip days, suggesting a cumulative effect

of duty-related activities and sleep loss. Fatigue and negative affect were higher, and activation lower,

by the end of trip days than by the end of pretrip days. The inability to maintain subjective activation

by the end of trip days was exacerbated by early on-duty times.
73

Pilots drank 42% more caffeine on trip days than on pretrip and posttrip days. More caffeine was

consumed in the early morning, in association with the early wake-ups, and also around the time of the

mid-afternoon peak in physiological sleepiness. The urge to fall asleep at this time would increase as

the sleep debt accumulated across trip days.

There were twice as many complaints of headaches on trips as at home. Reports of back pain

increased twelvefold, and reports of burning eyes increased fourfold. Helicopter pilots were three

times more likely to report headaches, and five times more likely to report back pain than were pilots

of fixed-wing aircraft on short-haul commercial flights. The physical environment on the helicopter

flight deck was probably an important factor. Studies of the same operations, conducted in parallel,

demonstrated that pilots often had skin temperatures outside the range of thermal comfort, and that

vibration levels in all of the helicopters studied exceeded the “reduced comfort” boundary defined by

the International Standards Organization (I.S.O. 263). The longer pilots remained on duty, the more

negative their mood became. This situation could be improved with better seat design, including better

isolation of the seat from floor vibration, and better flight-deck ventilation.

The predominant environmental factors affecting subjective workload assessments were different

for different phases of flight. The quality of the aircraft systems (rated on a 5-point scale from perfect to

useless) had a significant effect during preflight, taxi, climb, and cruise. Paying particular attention to

aircraft maintenance, thereby minimizing failures, might be one way of reducing workload during these

phases of flight. Landing weather was the major factor influencing workload ratings during descent and

approach. However, the effect of adverse weather on workload was reduced with better landing sites

and better letdown aids. The quality of the landing site and air-traffic control had a significant effect on

workload ratings during landing. These findings confirm that improvements in landing sites, letdown

aids, and air-traffic control can reduce subjective workload during descent, approach, and landing.
74

Crew Factors in Flight Operations VIII: Factors Influencing

Sleep Timing and Subjective Sleep Quality in Commercial

Long-Haul Flight Crews

Gander, P.H., Graeber, R.C., Connell, L.J, and Gregory, K.B. (1991). Crew factors in flight

operations: VIII. Factors influencing sleep timing and subjective sleep quality in commercial longhaul flight crews. (NASA Technical Memorandum No. 103852). Moffett Field, CA: National

Aeronautics and Space Administration.

Operational Overview

This report is the eighth in a series on physiological and psychological effects of flight operations

on flight crews, and the operational significance of these effects. The Operational Overview is a

comprehensive review of the major findings and their significance. The rest of this volume contains

the complete scientific description of the work. The aim of this study was to document how flight

crews organize their sleep during a variety of international trip patterns, and to elucidate how duty

requirements, local time, and the circadian system (measured by the rhythm of body temperature)

influence the choice of sleep times, sleep duration, and subjectively rated sleep quality. Duty requirements and local time can be viewed as environmental constraints on the time available for sleep, while

the circadian system is a major physiological modulator of sleep quality and duration.

Self-reports of sleep (and nap) timing and sleep quality, and continuous records of rectal

temperature were collected from 29 male flight crew members (average age 52 yr) during scheduled

B-747 commercial long-haul operations. Data from four different trip patterns were combined.

Sleep/wake patterns on these trips were complex. On average, duty periods lasted about 10.3 hr

and were followed by layovers of about 24.8 hr during which there were typically two subject-defined

sleep episodes. The average pattern of sleep and wakefulness (disregarding naps) was 19 hr wake/

5.7 hr sleep/7.4 hr wake/5.8 hr sleep. The average durations of the first- and second-sleep episodes in

a layover were not significantly longer episodes of wakefulness. However, first-sleeps were rated as

being of better quality, with less difficulty falling asleep and deeper sleep. Sleep-quality ratings

improved as sleep duration increased, reinforcing the importance of allowing adequate time for sleep.

The circadian system appeared to have a greater influence on the timing and duration of first-sleep

episodes than on second-sleep episodes in the layover, except when that level of accumulated sleep

debt was high, e.g., after eastward flights crossing five or more time zones. In such cases, crew

members typically went to sleep sooner after arriving at the layover destination, during the local

afternoon, and woke up either about 2 hr later (if they reported a nap) or 3 hr later (if they reported a

sleep episode). Otherwise, crew members tended to delay going to sleep until the local night and/or

until the hours preceding the temperature minimum.

The timing of second-sleep onsets seemed to be related primarily to the amount of sleep already

obtained in the layover and generally coincided with local night. The duration of second-sleeps was

strongly influenced by the amount of time remaining in the layover. For both first- and second-sleeps,
75

the circadian time of sleep onset was also a significant predictor of sleep duration. Longer sleep

episodes began earlier with respect to the minimum of the circadian temperature cycle.

In summary, the relative importance of duty requirements, local time, and the circadian system in

determining sleep timing and quality was different for first- and second-sleep episodes in a layover and

was related to specific flight schedules. Nevertheless, there were clearly preferred times for sleep

within the layover, determined by the circadian modulation of sleep propensity and the factors driving

the preference to sleep during the local night (noise, light, meal availability, etc.).

Flight and duty-time regulations can be interpreted as a means of ensuring that reasonable

minimum rest periods are respected. There has been a tendency on the part of regulatory authorities to

view the entire time off duty as being time available for sleep, despite anecdotal evidence that the ease

of falling asleep and the ability to remain asleep were not constant throughout the layover. This study

clearly documents that in scheduled commercial long-haul operations, there are physiologically and

environmentally determined preferred sleep times within a layover, i.e., the time available for sleep is

less than the time off duty.

Evidence from this and other studies suggests that the timing and duration of the second-sleep

episode in a layover is strongly linked to the amount of sleep already obtained in the layover. Particularly when the first-sleep is short, as is typical after eastward flights crossing five or more time zones,

it is essential that the layover be long enough to permit an adequate second-sleep episode appropriately

timed with respect to the temperature cycle and local time. The duration of any specific layover should

be determined with regard to the local arrival time, and the sequence of flights preceding it in the trip

pattern, which influences both the cumulative sleep loss and the phase of the circadian system.

Based on polygraphic studies of flight crew sleep after a single eastward flight crossing eight or

nine time zones, Graeber et al. recommended that crew members should limit sleep immediately after

arrival and prolong the subsequent wake period to end around the normal local time for sleep. This is

intended to improve the quality of the subsequent sleep episode, in keeping with the anecdotal report

that flight crews consider it important to have a good sleep immediately before a flight. Their study

looked only at sleep during the first (24 hr) layover of a trip sequence. The present study suggests that

the recommended strategy may not be optimal after eastward flights later in the sequence, when crew

members may have already accumulated an important sleep debt, and when the position of their

circadian timing system would be much less predictable.

Naps were also reported, both during the layovers and on the flight deck. Naps that represented

the first-sleep episode in a layover were significantly longer (average duration 2.0 hr) than subsequent

naps in the layover or flight-deck naps, and followed significantly longer episodes of wakefulness

(14.7 versus 5.9 and 9.3 hr, respectively). Such first naps were not very common and were associated

with the acute sleep debt imposed by overnight eastward flights crossing five or more time zones

(67%) or the prolonged wakefulness associated with westward flights crossing five or more time

zones (25%). Naps later in the layover tended to occur just before the next duty period and, since they

reduce the duration of continuous wakefulness before the next flight, may be useful as a strategy for

reducing cumulative sleep loss.
76

On the flight deck, crew members were observed to be napping at least 11% of the available time.

The average duration of these naps was 46 min (range 10–130 min). Recent work from our group

suggests that a preplanned 40-min time interval for napping on the flight deck can reduce subsequent

reaction times and the number of EEG/EOG microevents during long international flights. The optimal

duration of such naps is an active research issue.

This study has significantly enhanced our understanding of how the circadian system functions in

this complex operational environment. The flight schedules of the trips studied forced the sleep/wake

cycle to adopt a period different from that of the underlying circadian pacemaker, although the

influence of the circadian system was still seen in the selection of sleep times and in sleep durations,

i.e., the two systems were not completely uncoupled. However, when the accumulated sleep debt

was high, the circadian rhythm in sleep propensity could be overridden, and crew members could

fall asleep at unusual times in their temperature cycles. The circadian system, in turn, effectively

uncoupled from the very complex patterns of environmental synchronizing stimuli experienced by

crews.

There are known to be differences between individuals in (1) the periods of their circadian

pacemakers, (2) their sensitivity to environmental synchronizers, and (3) their self-selected patterns of

exposure to social and sunlight cues in each time zone. At least some of these factors may be associated with certain personality profiles and probably all are age-dependent. An analysis of questionnaire

data from 205 of the flight crew members in our data bases concurs with other studies suggesting that

the period of the circadian pacemaker shortens with age. Age-related changes in sleep are also well

documented, including shorter, less efficient nocturnal sleep and increased physiological sleepiness

during the day.

The timing and quality of sleep obtained by flight crews is the product of a subtle and dynamic

interplay between all of these factors and cannot be captured by any simple predictive algorithm.

Based on the insights gained in this and other studies, we see two particularly promising approaches

to improving en route sleep for flight crews during international commercial trip patterns. The first is

education, providing crew members with basic information about sleep and the functioning of the

circadian system, and how their behavior can modify both. Second, expert system technology should

be used to combine our understanding of the underlying physiological systems with operational

knowledge acquired from flight crew members and schedulers to develop a computerized intelligent

scheduling assistant.
77

Crew Factors in Flight Operations IX: Effects of Planned Cockpit Rest

on Crew Performance and Alertness in Long-Haul Operations

Rosekind, M.R., Graeber, R.C., Dinges, D.F., Connell, L.J., Rountree, M.S., Spinweber, C.L., and

Gillen, K.A. (1994). Crew factors in flight operations IX: Effects of planned cockpit rest on crew

performance and alertness in long-haul operations. (NASA Technical Memorandum No. 108839).

Moffett Field, CA: National Aeronautics and Space Administration.

Operational Overview

This report is the ninth in a series on physiological and psychological effects of flight operations

on flight crews, and on the operational significance of these effects.

Long-haul flight operations often involve rapid multiple time-zone changes, sleep disturbances,

circadian disruptions, and long, irregular work schedules. These factors can result in fatigue, cumulative sleep loss, decreased alertness, and decreased performance in long-haul flight crews. Thus,

operational effectiveness and safety may be compromised because of pilot fatigue. One natural

compensatory response to the sleepiness and fatigue experienced in long-haul operations is unplanned,

spontaneous napping and nonsanctioned rest periods. That these activities occur is supported by

anecdotal, observational, and subjective report data from a variety of sources. In response to this

information and to concerns for maintaining flight safety, it was suggested that a planned cockpit rest

period could provide a “safety valve” for the fatigue and sleepiness experienced in long-haul flying.

The cockpit rest period would allow a planned opportunity to sleep, with the primary goal being to

improve subsequent levels of performance and alertness, especially during critical phases of operation

such as descent and landing.

This study was co-sponsored and sanctioned by the FAA and involved the voluntary participation

of two commercial airlines. The primary goal was to determine the effectiveness of a planned cockpit

rest period to improve performance and alertness in nonaugmented, three-person long-haul flight

operations. Twenty-one volunteer pilots participated and were randomly assigned to either a rest group

(N = 12) or a no-rest group (N = 9) condition. The rest group (RG) was allowed a planned 40-min

rest period during the low-workload, cruise portion of flight over water. Pilots rested one at a time, on

a prearranged rotation, with two crew members maintaining the flight at all times. The no-rest group

(NRG) had a 40-min planned control period identified during cruise but maintained their usual flight

activities during this time. The four consecutive middle legs of a regularly scheduled transpacific trip,

part of a 12-day trip pattern, were studied. Two legs were westbound day flights and two legs were

eastbound night flights, with generally comparable flight and duty times.

Specific procedural and safety guidelines were successfully implemented in this initial study.

However, not all of these would be necessary for a general implementation of planned cockpit rest

periods in long-haul flight operations: (1) it was crucial that the rest period was planned, with first

choice of rest period going to the landing pilot; (2) the rest periods were scheduled during a lowworkload phase of flight and ended 1 hr before descent; (3) only one crew member was scheduled to

rest at a time with a clear planned rotation established; (4) the rest opportunity was divided into an
78

initial preparation period (3 min), followed by the 40-min rest period, followed by a recovery period

(20 min) (these times might be altered to reduce the overall length of the period); (5) the rest was

terminated at a preset time by a researcher, and the resting pilot was fully briefed before reentering the

operational loop; and (6) it was established that the captain would be notified immediately at the first

indication of any potential anomaly. The safe and normal operation of the aircraft was given the

highest priority and, therefore, no cockpit rest procedure or activity was allowed to interfere with this.

Several measures were used to examine the physiological, behavioral, performance, and subjective

effects of the planned cockpit nap. Continuous ambulatory recordings of brain wave and eye movement activity were conducted to determine physiologically how much sleep was obtained during the

rest period, as well as the time taken to fall asleep and the stages of sleep. (These recordings allowed

differentiation of non-rapid-eye-movement (NREM) sleep and its stages and rapid-eye-movement

(REM) sleep). A reaction-time/sustained-attention task (psychomotor vigilance task) was used to

assess performance capability. A wrist activity monitor was worn continuously before, during, and

after the trip schedule. This activity monitor provided information regarding the pilots’ 24-hr rest/

activity pattern and was used to examine layover sleep episodes. Subjective measures collected in the

study included in-flight fatigue and alertness ratings, a daily log for noting sleep periods, meals,

exercise, flight and duty periods, etc., and the NASA Background Questionnaire.

The physiological data showed that on 93% of the rest period opportunities the RG pilots were

able to sleep. Generally, they fell asleep quickly (average = 5.6 min) and slept for an average of

26 min. There were six factors related to sleep quantity and quality that were analyzed: total sleep

time, sleep efficiency, sleep latency, percent NREM stage 1 sleep, percent NREM stage 2 sleep, and

percent NREM slow wave sleep. Each of these factors was examined for effects related to trip leg,

halves of the trip, day versus night, and flight position (captain, first officer, second officer). There

were two significant effects that emerged from these analyses. The day flights had significantly more

light sleep than night flights, and the night flights had significantly more deep sleep than day flights.

An interesting finding emerged from analysis of the physiological data collected during the NRG

40-min control period. Although instructed to continue usual flight activities, four NRG pilots fell

asleep (a total of five episodes) for periods lasting from several minutes to over 10 min.

There were generally consistent findings for the variety of analytical approaches used to examine

the performance data. The median sustained attention/reaction time (a performance measure) for the

NRG showed a greater range of average responses across flight legs and during in-flight trials than

seen in the RG. After leg 1, the pilots in the NRG showed a steady increase in median reaction time

across flight legs, with significant differences by the middle and end of flights. The RG pilots

maintained a generally consistent level of performance both across and within flight legs, and did not

show significant increases in reaction time. There were a total of 283 lapses (i.e., a response delay

> 0.5 sec) for all 21 pilots (both groups combined). For in-flight trials, the NRG (with fewer

subjects) had a total of 124 lapses, whereas the RG had a total of 81. There was an increase in lapses

during in-flight trials 2 and 3 (after the test period) for the NRG, though this increase did not occur

during in-flight trials following the nap in the RG. Both groups had more lapses before top of descent

(TOD) on night-flight leg 4 than on night leg 2. However, the number of lapses in the NRG pilots

increased twice as much as in the RG pilots. Vigilance decrement functions also revealed that on night

flights the NRG pilots had a level of performance that was significantly decreased relative to the RG

pilots. Generally, the performance task demonstrated decrements across flight legs and within flights
79

for the NRG, whereas the RG maintained consistent levels of performance. These findings suggest

that the planned nap prevented deterioration of vigilance performance.

Changes in brain wave and eye movement activity can reflect the subtle ways that physiological

alertness/sleepiness changes. An intensive critical phase analysis was conducted to examine the effects

of the cockpit nap on subsequent physiological alertness. The period from 1 hr before TOD through

descent and landing was analyzed for the occurrence of brain and eye movement microevents indicative of reduced physiological alertness. During approximately the last 90 min of flight, each event

greater than 5-sec duration was scored for both the NRG and RG. There was at least one such

microevent identified in 78% of the NRG and 50% of the RG. Overall, there were a total of

120 microevents that occurred in the NRG (with fewer subjects) and a total of 34 microevents in the

RG. The NRG averaged significantly more total microevents (6.37) than the average in the RG (2.90).

This supports the conclusion that the sleep obtained during the rest period was followed by increased

physiological alertness in the RG relative to the NRG.

The 24-hr rest/activity patterns, in combination with the subjective logs, demonstrated that 86% of

the 21 subjects accumulated a sleep debt that ranged from 4 to 22 hr and averaged approximately 9 hr

by the ninth day of the duty cycle. When the entire 36-hr duty period (layover and subsequent duty

cycle) is considered, the percent of layover sleep time is 28%. This is less than the average 33% sleep

time spent off-duty at home, hence the cumulative sleep debt. One subject gained sleep, and two others

had no change. Further analysis demonstrated that the cockpit nap did not significantly alter the

cumulative sleep debt observed in the RG. Also, 77% of the layovers involved more than one sleep

episode. Generally, there were two sleep episodes, and if the first one was long, then the second one

was short or did not occur. Conversely, if the first sleep episode was short, then there was almost

always a second one that was long. This result demonstrated that there were multiple factors operating

to control sleep timing and quantity (e.g., local time, home circadian time, prior sleep loss). This study

was not designed to examine the issue of layover sleep periods, though recently, the timing of layover

sleep periods, including naps, in long-haul flight operations, has been addressed.

Overall, the analysis of the subjective alertness ratings demonstrated that pilots reported lower

alertness on night flights than on day flights and after the rest/control period than before it (except on

leg 1). The results indicated that the nap did not affect the subjective ratings of alertness, though the

objective measures clearly indicated better performance and greater alertness in the RG.

The level of physiological sleepiness experienced in long-haul flight operations was demonstrated

in both subject groups. The speed of falling asleep has been used as a measure of physiological

sleepiness (i.e., the more sleepy an individual, the faster he or she will fall asleep). The speed of

falling asleep in the RG (5.6 min) is comparable to that seen in moderately sleep deprived individuals.

A diagnostic guide for excessive sleepiness in sleep disorder patients is a sleep latency of 5 min or

less. Also, there were five episodes of sleep that occurred during the control period in four NRG pilots

who had been instructed to continue usual flight operations. This result reinforces previous findings

that pilots are poor evaluators of their level of physiological sleepiness.

Overall, the study results provide support for differentiating fatigue countermeasures into two

basic approaches. Conceptually and operationally, methods to minimize or mitigate the effects of sleep

loss, circadian disruption, and fatigue in flight operations can be divided into (1) preventive strategies
80

and (2) operational countermeasures. Preventive strategies involve those approaches that result in more

long-term adjustments and effects on underlying physiological sleep and circadian processes

(e.g., possibilities for further research include shifting the circadian phase before multiple time-zone

changes, using bright lights or exercise to rapidly readjust the circadian clock, and maximizing the

quantity and quality of sleep). These preventive strategies affect underlying physiological sleep need,

sleepiness, and circadian phase in a long-term and chronic fashion. Operational countermeasures are

focused strategies for reducing sleepiness and improving performance and alertness during actual

operations (e.g., proved strategies include judicious use of caffeine, increased physical activity, and

increased interaction). These short-acting countermeasures are not intended to reduce underlying

physiological sleepiness or a sleep debt, but rather to increase performance and alertness during

operational tasks. One acute, short-acting operational countermeasure that can temporarily reduce

physiological sleepiness is napping. The planned cockpit nap in this study is considered to be an

operational countermeasure that provided an acute, short-acting improvement in performance and

alertness.

It must be acknowledged that every scientific study has specific limitations that restrict the

generalizability of the results. This study involved only one trip pattern on a commercial airline carrier.

The study was conducted on transpacific flights to utilize the opportunity of scheduling the planned

rest periods during the low-workload portion of cruise over water. The intense physiological and

performance data collection occurred during a specific and restricted middle segment (four consecutive

flight legs) of the trip schedule. Therefore, the initial home-to-flight-schedule transition is quantified

only with log book and activity data. Also, the highest levels of accumulated fatigue, which probably

occurred during the final trip legs, were not studied except for log book and activity data. This study

involved B-747 aircraft flown by three-person crews; the specific application of this countermeasure

to the two-person cockpit was not addressed. There were two NASA researchers on the flight deck

during the in-flight data collection periods. Although they were instructed to minimize their interactions

and presence, there is no question that having two extra individuals on the flight deck may have

potentially altered the regular flow of cockpit conversation and interaction. It is important to remain

cognizant of these limitations when attempts are made to generalize the study results to questions that

extend beyond the scope of the specific scientific issues addressed here.

In conclusion, the RG pilots were able to sleep during the planned cockpit rest period, generally

falling asleep quickly and sleeping efficiently. This nap was associated with improved performance

and physiological alertness in the RG compared to the NRG. The benefits of the nap were observed

through the critical descent and landing phases of flight. The convergence of the behavioral performance data and the physiological data to demonstrate the effectiveness of the cockpit nap lends support

to the robustness of the findings. The nap did not affect layover sleep or the overall cumulative sleep

debt displayed by the most of the crew members. The nap procedures were implemented with minimal

disruption to usual flight operations, and there were no reported or identified concerns regarding

safety.

The planned nap appeared to provide an effective, acute relief for the fatigue and sleepiness

experienced in nonaugmented three-person long-haul flight operations. The strength of the current

results supports the implementation of planned cockpit sleep opportunities in nonaugmented long-haul

flight operations involving three-person crews. If planned cockpit sleep opportunities were sanctioned,

each airline could determine the appropriate incorporation of procedures into its specific mode of
81

operation. If implemented, we recommend that a joint NASA/FAA follow-up study be conducted

within 6–12 months to examine how planned cockpit sleep opportunities have been incorporated into

airline procedures. That study would examine how the procedures were implemented and their effectiveness. This might take the form of a survey or include some field data collection. The results of

that follow-up study might then lend support for further refinement of procedures and future

implementation in other flight environments.

83

APPENDIX D

NASA AMES FATIGUE COUNTERMEASURES PROGRAM

Representative Publications

Co, E.L., Rosekind, M.R., Johnson, J.M., Weldon, K.J., Smith, R.M., Gregory, K.B.,

Miller, D.L., Gander, P.H., & Lebacqz, J.V. (1994). Fatigue countermeasures: Alertness

management in flight operations. In Proceedings of the Eleventh Annual International Aircraft Cabin

Safety Symposium. Long Beach, CA: Southern California Safety Institute.

Dinges, D.F., Rosekind, M.R., Connell, L.J., Graeber, R.C., and Gillen, K.A. (1992). Eastbound

night flights vs. westbound day flights: Directionally dependent effects on flight crew layover sleep.

Sleep Research, 21, 118.

Foushee, H.C., Lauber, J.K., Baetge, M.M., and Acomb, D.B. (1986). Crew factors in flight

operations: III. The operational significance of exposure to short-haul air transport operations.

(NASA Technical Memorandum No. 88322). Moffett Field, CA: National Aeronautics and Space

Administration.

Gander, P.H., Kronauer, R., and Graeber, R.C. (1985). Phase-shifting two coupled circadian

pacemakers: Implications for jetlag. Am. J. Physiol., 249, R704–R719.

Gander, P.H., Connell, L.J., and Graeber, R.C. (1986). Masking of the circadian rhythms of heart

rate and core body temperature by the rest-activity cycle in man. J. Biol. Rhythms Res., 1(2),

119–135.

Gander, P.H., Myrhe, G., Graeber, R.C., Anderson, H.T., and Lauber, J.K. (1989). Adjustment of

sleep and the circadian temperature rhythm after flights across nine time zones. Aviation, Space,

Environmental Medicine, 60, 733–743.

Gander, P.H., Graeber, R.C., Connell, L.J, and Gregory, K.B. (1991). Crew factors in flight

operations: VIII. Factors influencing sleep timing and subjective sleep quality in commercial longhaul flight crews. (NASA Technical Memorandum No. 103852). Moffett Field, CA: National

Aeronautics and Space Administration.

Gander, P.H., Nguyen, D., Rosekind, M.R., & Connell, L.J. (1993). Age, circadian rhythms, and

sleep loss in flight crews. Aviation, Space and Environmental Medicine, 64(3), 189–195.

Gander, P.H., Graeber, R.C., Foushee, H.C., Lauber, J.K., and Connell, L.J. (1994). Crew factors

in flight operations: II. Psychophysiological responses to short-haul air transport operations. (NASA

Technical Memorandum). Moffett Field, CA: National Aeronautics and Space Administration.
84

Gander, P.H., Barnes, R., Gregory, K.B., Connell, L.J., Miller, D.L., and Graeber, R.C. (1994).

Crew factors in flight operations VI: Psychophysiological responses to helicopter operations.

(NASA Technical Memorandum No. 108838). Moffett Field, CA: National Aeronautics and Space

Administration.

Gander, P.H., Gregory, K.B., Connell, L.J., and Miller, D.L. (1996). Crew factors in flight

operations VII: Psychophysiological responses to overnight cargo operations. (NASA Technical

Memorandum). Moffett Field, CA: National Aeronautics and Space Administration.

Graeber, R.C. (1982). Alterations in performance following rapid transmeridian flights. In F.M Brown

and R.C. Graeber (Eds.), Rhythmic Aspects of Behaviour, 172–212.

Graeber, R.C. (Ed.) (1986). Crew factors in flight operations: IV. Sleep and wakefulness in

international aircrews. (NASA Technical Memorandum No. 88231). Moffett Field, CA: National

Aeronautics and Space Administration.

Graeber, R.C. (1987). Aircrew fatigue and circadian rhythmicity. In E. Weiner and D. Nagel (Eds.),

Human Factors in Aviation, 305–344.

Graeber, R.C., Rosekind, M.R., Connell, L.C., and Dinges, D.F. (1990). Cockpit napping. ICAO J.,

45(10), 6–10.

Kelly, S.M., Rosekind, M.R., Dinges, D.F., Miller, D.L., Gillen, K.A., Aguilar, R.D., and Smith,

R.M. (1993). Flight controller alertness and performance during MOD shiftwork operations.

(NASA Conference Publication No. 3240).

Kurosaki, Y., Sasaki, M., Takahashi, T., Mori, A., Spinweber, C.L., and Graeber, R.C. (1987).

Flight crew sleep after multiple layover polar flights. Sleep Research, 16, 565.

Monk, T., Moline, M., and Graeber, R.C. (1988). Inducing jet lag in the laboratory: Patterns of

adjustment to an acute shift in routine. Aviation, Space, and Environmental Medicine,

59, 703–710.

Pilot Fatigue and Circadian Desynchronosis. (1980). Report of a workshop held in San Francisco,

California on August 26–28, 1980. (NASA Technical Memorandum No. 81275). Moffett Field,

CA: National Aeronautics and Space Administration.

Rosekind, M.R., Gander, P.H., and Dinges, D.F. (1991). Alertness management in flight operations:

Strategic napping. SAE Technical Paper Series No. 912138.

Rosekind, M.R., Gander, P.H., Miller, D.L., Gregory, K.B., McNally, K.L., Smith, R.M., and

Lebacqz, J.V. (1993). NASA Ames Fatigue Countermeasures Program. FAA Aviation Safety

Journal, 3(1), 20–25.
85

Rosekind, M.R., Gander, P.H., Miller, D.L., Gregory, K.B., Smith, R.M., Weldon, K.J., Co,

E.L., McNally, K.L., and Lebacqz, J.V. (1994). Fatigue in operational settings: Examples from the

aviation environment. Human Factors, 36(2), 327–338.

Rosekind, M.R., Graeber, R.C., Dinges, D.F., Connell, L.J., Rountree, M.S., Spinweber, C.L., and

Gillen, K.A. (1994). Crew factors in flight operations IX: Effects of planned cockpit rest on crew

performance and alertness in long-haul operations. (NASA Technical Memorandum No. 108839).

Moffett Field, CA: National Aeronautics and Space Administration.

Rosekind, M.R., Gregory, K.B., Miller, D.L., Co, E.L., and Lebacqz, J.V. (1994). Analysis of

crew fatigue factors in AIA Guantanamo Bay aviation accident. In National Transportation Safety

Board special investigation report on commercial aviation accident. (NTIS No. PB94-910406).

Washington, D.C.: National Transportation Safety Board.

Rosekind, M.R., Weldon, K.J., and Lebacqz, J.V. (1993). Pegasus launch anomaly, evaluation of

contributory fatigue factors. In National Transportation Safety Board special investigation report on

commercial space launch incident. (NTIS No. PB93-917003). Washington, D.C.: National

Transportation Safety Board.

Rosekind, M.R., Co, E.L., Johnson, J.M., Smith, R.M., Weldon, K.J., Miller, D.L., Gregory,

K.B., Gander, P.H., & Lebacqz, J.V. (1994). Alertness management in long-haul flight operations.

In Proceedings of the Thirty-Ninth Corporate Aviation Safety Seminar St. Louis, MO: Flight Safety

Foundation.

Rosekind, M.R., Weldon, K.J., Co, E.L., Miller, D.L., Gregory, K.B., Smith, R.M., Johnson,

J.M., Gander, P.H., & Lebacqz, J.V. (1994). Fatigue factors in regional airline operations. In

Public Forum on Commuter Airline Safety. Atlanta, GA: National Transportation Safety Board.

87

APPENDIX E

GENERAL READINGS

Carskadon, M.A. (Ed.). (1992). Encyclopedia of sleep and dreaming. New York, NY: Macmillan

Publishing Company.

Coleman, R.M. (1986). Wide awake at 3:00 A.M.: By choice or by chance? New York, NY:

W.H. Freeman & Company.

Dement, W.C. (1972). Some must watch while some must sleep. New York, NY: W.W. Norton

& Company.

Dement, W.C. (1992). The sleepwatchers. Stanford, CA: Stanford Alumni Association.

Dinges, D.F., & Broughton, R.J. (Eds.). (1989). Sleep and Alertness: Chronobiological, Behavioral,

and Medical Aspects of Napping. New York, NY: Raven Press.

Kryger, M.H., Roth T., and Dement, W.C. (Eds.). (1994). Principles and Practice of Sleep

Medicine. Philadelphia, PA: Saunders.

Lamberg, L. (1984). The American Medical Association guide to better sleep. New York, NY:

Random House.

Moore-Ede, M.C., Sulzman, F.M., and Fuller, C.A. (1982). The clocks that time us: Physiology of

the circadian timing system. Cambridge, MA: Harvard University Press.

Rosa, R.R., Bonnet, M.H., Bootzin, R.R., Eastman, C.I., Monk, T., Penn, P.E. Tepas, D.I., and

Walsh, J.K. (1990). Intervention factors for promoting adjustment to nightwork and shiftwork. In

A.J. Scott (Ed.), Occupational medicine: State of the art reviews (pp. 391–416). Philadelphia, PA:

Hanley & Belfus, Inc.
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A05

Crew Factors in Flight Operations X: Alertness Management

in Flight Operations

Mark R. Rosekind, Philippa H. Gander,* Linda J. Connell,

and Elizabeth L. Co*

In response to a 1980 congressional request, NASA Ames Research Center initiated a Fatigue/Jet Lag

Program to examine fatigue, sleep loss, and circadian disruption in aviation. Research has examined fatigue

in a variety of flight environments using a range of measures (from self-report to performance to physiological). In 1991, the program evolved into the Fatigue Countermeasures Program, emphasizing the development and evaluation of strategies to maintain alertness and performance in operational settings. Over the

years, the Federal Aviation Administration (FAA) has become a collaborative partner in support of fatigue

research and other Program activities.

From the inception of the Program, a principal goal was to return the information learned from research

and other Program activities to the operational community. The objectives of this Education and Training

Module are to explain what has been learned about the physiological mechanisms that underlie fatigue,

demonstrate the application of this information in flight operations, and offer some specific fatigue countermeasure recommendations. It is intended for all segments of the aeronautics industry, including pilots, flight

attendants, managers, schedulers, safety and policy personnel, maintenance crews, and others involved in an

operational environment that challenges human physiological capabilities because of fatigue, sleep loss, and

circadian disruption.

Fatigue, Circadian rhythms, Education and training

Technical Memorandum

Point of Contact: David F. Neri, Ames Research Center, MS 262-4, Moffett Field, CA 94035-1000

 (650) 604-0658

*San Jose State University Foundation, Ames Research Center.