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OCR for page 87
5
Pilot Commuting and Fatigue Risk
In this chapter we relate the scientific evidence presented in Chapter 4
to the manner in which pilot commuting could contribute to these factors
and therefore to fatigue as an operational risk.1 We repeat the caution to
readers not to assume that the distance pilots live from the airport reflects
their likely commute times. As discussed above, there are very little data to
evaluate that assumption.
INADEQUATE SLEEP PRIOR TO FLIGHT DUTY
Consistent with the scientific literature from laboratory experiments
(reviewed in Chapter 4), field studies of pilots have found that sleep dura-
tion in the 24 hours prior to a flight duty period can contribute to pilot
fatigue in flight. In a recent report by Thomas and Ferguson (2010), sleep
and performance data from captains and first officers were collected by
trained expert observers during 302 normal flight operations of a commer-
cial airline flying short-haul jet operations that primarily occurred between
6:00 a.m. and 10:00 p.m. Crew members provided estimates of their total
sleep in the prior 24 hours, their total sleep in the prior 48 hours, and the
total time they were awake since their last sleep period at the commence-
1 We did not consider transportation while crews are laying over during long-haul opera-
tions, as these typically involve arranged times, hotels for sleep, and conveyances to and from
the airport, and they fall within the flight and duty time regulations. We are also not consider-
ing in-flight sleep during long-haul operations with augmented crews, as these also fall within
the flight and duty time regulations.
87
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88 THE EFFECTS OF COMMUTING ON PILOT FATIGUE
ment of cruise (i.e., early in flight). Observers assessed the crew during
normal flight operations using the “threat and error management model”
(Helmreich, 2000; International Civil Aviation Organization, 2002; Klinect,
2002). In this model, safety was defined as the active process of crews’ effec-
tive management of operational threats, which included aspects of normal
flight operations that have the potential to negatively affect safety, such as
adverse weather or an aircraft system malfunction, and management of the
inevitable errors that occur as part of normal human performance. The
study found that restricted sleep in both the 24-hour and 48-hour periods
prior to each sector was associated with changes in crews’ threat and error
management performance. Restriction to less than 6 hours of sleep in the
prior 24 hours was associated with degraded operational performance and
increased error rates (Thomas and Ferguson, 2010). The authors concluded
that their findings support prior sleep as a critical fatigue-related variable.
A study of 19 long-haul pilots also found that sleep in the prior 24
hours was a significant predictor of self-rated fatigue and the measured
mean response speed of the psychomotor vigilance task after international
flight sectors (Petrilli et al., 2006). These investigators concluded that in
order to minimize the risk of fatigue, the sleep obtained by pilots should be
taken into account in the development of flight and duty time regulations.
This provocative suggestion may or may not be considered relative to flight
and duty time regulations, but the scientific evidence on how commut-
ing may contribute to fatigue because of inadequate sleep and prolonged
wakefulness may suggest that there is a shared responsibility for mitigating
fatigue between pilots and carriers.
Sleep is a physiological phenomenon that is defined by measuring brain
waves, eye movements, muscle activity, and other physiological processes.
As noted in Chapter 4, in order to acquire 6 hours physiological sleep
time, an average healthy adult must spend approximately 7 hours in bed,
as physiological sleep occurs for 85-95 percent of time in bed for healthy
sleepers. Thus, when it is necessary to obtain at least 6 hours of physi-
ological sleep, the time in bed would have to be approximately 7 hours.
Moreover, although some people can function at normal levels for a night
or two with 6 hours of physiological sleep, repeated days of 6 hours of sleep
can result in cumulative fatigue and its attendant cognitive performance
deficits in a significant portion of the population (Van Dongen et al., 2003a;
Mollicone et al., 2007). Therefore, a requirement of 6 hours of physiologi-
cal sleep (i.e., 7 hours of time in bed) prior to duty should be considered
a bare minimum for alert functioning, and its adequacy for pilot alertness
should be periodically evaluated.
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89
PILOT COMMUTING AND FATIGUE RISK
EXAMPLES OF “FAVORABLE” AND
“UNFAVORABLE” COMMUTES
In order to illustrate how the various dimensions of a pilot’s commute
may be affected by sources of fatigue, the committee presents illustrations
of commute patterns for four different combinations of home-to-domicile
distances, timing, and circadian shifts. These commute patterns are drawn
from the committee’s direct conversations with various stakeholders (in-
cluding pilots, airlines, unions, and the FAA), in the course of hearings and
testimony, during this study. These examples reflect the norms of the indus-
try based on conversations with industry officials, the committee’s experi-
ence, and the committee’s analysis of home-to-domicile distances calculated
from zip code data (see Chapter 3). These selections may not reflect the
true distribution of commutes but were rather chosen to highlight different
patterns. These illustrations are accompanied by examples of “favorable”
and “unfavorable” commuting patterns based on the findings from sleep
science. Four primary sources of fatigue—time awake, sleep time, sleep
quality, and circadian phase—are the dependent variables for determining
whether a commute is favorable or unfavorable. These examples begin with
place of residence for the pilot and end with the completion of the pilot’s
first day’s duty assignment.2 The committee had no way to determine how
much more risk an unfavorable commute would present as compared to a
favorable one.
Example 1: Home, Portland, Oregon; Domicile,
San Francisco International Airport (SFO)
Description: Early morning awakening following short sleep
Factors: Time since awakening, with 13 hours duty
Unfavorable: Example 1a
The pilot, on the evening preceding the assignment, goes to bed ear-
lier than usual at 9:00 p.m., but, unaccustomed to the early bedtime, falls
asleep at 10:00 p.m. The pilot wakes at 3:00 a.m. at home in Portland
after 5 hours of sleep. The pilot departs his home at 3:30 a.m. and arrives
at the Portland International Airport (PDX) at 4:00 a.m. The pilot departs
PDX at 5:00 a.m. on a 1-hour commuting flight as a passenger to SFO.
The pilot reports for duty at 8:00 a.m. for the first assigned flight, which
departs at 9:00 a.m. The pilot flies three legs, with the last one landing at
2 Alltime references refer to the time associated with the pilot’s place of residence (residence
time), not time at location of flight legs or aircraft landing.
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90 THE EFFECTS OF COMMUTING ON PILOT FATIGUE
Total Time Awake (18)
Activity (hours)
Flight Segments (7)
On Duty (13)
Commute (2.5)
Rest
(6 in bed, 5 sleep)
11:00
11:00
9:00
10:00
12:00
1:00
2:00
3:00
4:00
5:00
6:00
7:00
8:00
9:00
10:00
12:00
1:00
2:00
3:00
4:00
5:00
6:00
7:00
8:00
9:00
PM AM PM
Time of Day at Residence
Figure 5-1.eps
FIGURE 5-1 Example 1a: Unfavorable commuting pattern.
SOURCE: Based on a submission by a pilot to the Aviation System Reporting Sys-
tems (ASRS) database. ASRS collects, processes, and analyzes voluntarily submitted
aviation safety incident reports of unsafe occurrences and hazardous situations from
pilots, air traffic controllers, dispatchers, flight attendants, maintenance technicians,
and others. For details, see http://asrs.arc.nasa.gov/overview/summary.html [May
2011].
Bradley International Airport (BDL) in Hartford, Connecticut, at 9:00 p.m.
(Oregon time). At this time, the pilot has been awake for 18 hours, includ-
ing 13 hours of duty, following a short sleep (5 hours). For the graphical
representation of this example, see Figure 5-1.
Favorable: Example 1b
The pilot commutes from home to SFO the day before the duty assign-
ment begins. The pilot arrives in San Francisco by 9:30 p.m., sleeps at a
hotel near the airport, going to sleep by 11:00 p.m. and awakens at 6:30
a.m. (with 7.5 hours of sleep). Following the same pattern above, ending
the duty at BDL, the pilot’s time since awakening is 14.5 hours, following a
night of 7.5 hours of sleep. For a graphical representation of this example,
see Figure 5-2.
Example 2: Home, Alexandria, Virginia; Domicile: John F.
Kennedy International Airport (JFK), New York City
Description: Emergent, unplanned circumstance in commute
Factors: Long total awake time without nap, operations during circa-
dian low
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91
PILOT COMMUTING AND FATIGUE RISK
Total Time Awake (14.5)
Activity (hours)
Flight Segments (7)
On Duty (13)
Commute (3.0)
Rest
(8 in bed, 7.5 sleep)
11:00
11:00
7:00
8:00
9:00
10:00
12:00
1:00
2:00
3:00
4:00
5:00
6:00
7:00
8:00
9:00
10:00
12:00
1:00
2:00
3:00
4:00
5:00
6:00
7:00
8:00
9:00
PM AM PM
Time of Day at Residence
FIGURE 5-2 Example 1b: Favorable commuting pattern.
Figure 5-2.eps
Unfavorable: Example 2a
The pilot obtains a full night’s sleep (7 hours) in the evening prior
to duty and awakens at his normal time of 6:00 a.m. After spending the
morning and early afternoon at home engaged in normal activities, the pilot
leaves at 2:00 p.m., arriving at Ronald Reagan Washington National Air-
port (DCA) at 2:30 p.m. for a 3:30 p.m. departure to JFK. The flight is late
and departs at 4:30 p.m., arriving at JFK at 6:00 p.m. The pilot reports for
duty at 7:00 p.m. The pilot begins the single-leg assignment at 8:00 p.m. to
Phoenix, Arizona, arriving at 1:00 a.m. (Virginia time). Although the pilot
had adequate sleep the night before, the pilot’s time awake by the end of
the duty day is 19 hours.
Even if the pilot attempted to sleep or nap prior to leaving home for
the commute to JFK, the pilot is unlikely to have obtained restful sleep so
soon after awakening and during the circadian peak. Moreover, the pilot
is waiting for a delayed flight and then taking a short commuting flight
during the afternoon circadian low, when a nap attempt may be more suc-
cessful. Thus, with the commute occupying the best portion of the preduty
period for sleep, although several hours are potentially available for sleep
prior to duty, it is quite possible that this pilot will be landing the aircraft
in Phoenix fatigued, with the length of time since awakening likely to affect
individual performance adversely. For the graphical representation of this
example, see Figure 5-3.
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92 THE EFFECTS OF COMMUTING ON PILOT FATIGUE
Total Time Awake (19)
Activity (hours)
Flight Segments (5)
On Duty (6)
Commute (4)
Rest
(8 in bed, 7 sleep)
11:00
11:00
11:00
10:00
12:00
1:00
2:00
3:00
4:00
5:00
6:00
7:00
8:00
9:00
10:00
12:00
1:00
2:00
3:00
4:00
5:00
6:00
7:00
8:00
9:00
10:00
12:00
1:00
PM AM PM AM
Time of Day at Residence
FIGURE 5-3 Example 2a: Unfavorable commuting pattern.
SOURCE: Based on personal testimony from stakeholders at open session meetings.
Figure 5-3.eps
Total Time Awake (16)
Activity (hours)
Flight Segments (5)
On Duty (6)
Commute (3)
Rest
(8 in bed, 7 sleep,
3 nap)
11:00
11:00
11:00
10:00
12:00
1:00
2:00
3:00
4:00
5:00
6:00
7:00
8:00
9:00
10:00
12:00
1:00
2:00
3:00
4:00
5:00
6:00
7:00
8:00
9:00
10:00
12:00
1:00
PM AM PM AM
Time of Day at Residence
FIGURE 5-4 Example 2b: Favorable commuting pattern.
Figure 5-4.eps
Favorable: Example 2b
The pilot leaves home earlier, finds a rest facility, and naps in an envi-
ronment conducive to quality rest during this circadian phase for napping,
2:00 p.m. to 5:00 p.m. For the graphical representation of this example,
see Figure 5-4.
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93
PILOT COMMUTING AND FATIGUE RISK
Example 3: Home, Concord, California; Domicile, Charlotte/
Douglas International Airport (CLT), Charlotte, North Carolina
Description: Transcontinental commute, cargo airline
Factors: Nocturnal sleep loss and work during circadian low; unrestful
sleep environment; early morning awakening; inadequate sleep in 24 hours
prior to end of duty; difficulty of sleeping during circadian high; question-
able sleep quantity/quality during night-time commuting flight.
Unfavorable: Example 3a
The pilot leaves home in Concord, California, at 9:00 p.m., arriving
at SFO at 10:00 p.m. The pilot departs SFO at 11:00 p.m. to commute to
CLT, arriving Charlotte at 4:00 a.m. (California time). The pilot checks in
for duty at 5:00 a.m. and begins the duty assignment at 6:00 a.m. for a
3-hour flight to Dallas/Fort Worth International Airport (DFW), arriving
at 9:00 a.m. (California time).
If the pilot had slept from noon to 8:00 p.m. at home, before depart-
ing at 9:00 p.m., the pilot would have obtained adequate sleep. However,
by sleeping on the normal pattern, from 11:00 p.m. to 7:00 a.m., and then
napping during the afternoon circadian low from 2:00 p.m. to 5:00 p.m.
(with actual sleep time 2.5 hours), the amount of time slept within the
past 24 hours preceding the projected time of landing in Dallas would be
inadequate.
The pilot could then consider the sleep that she might obtain during
the 5-hour commuting flight from the West Coast to the East Coast. In fa-
vor of obtaining restful sleep during this commute, the all-night timing of
the flight spans not only the window of circadian low, but also the pilot’s
entire habituated sleep period. The duration and quality of sleep actually
obtained, though, will depend on factors beyond the immediate control of
the pilot, such as whether the available accommodation is in a first-class lie-
flat sleeper seat or in an upright coach seat next to a crying baby. On arrival
at CLT, the pilot may well be faced with a decision of whether to advise
the airline that of being unfit to operate the assigned flight to DFW due to
fatigue. For the graphical representation of this example, see Figure 5-5.
Favorable: Example 3b
The pilot commutes in to Charlotte on the day before the assigned
flight, and sleeps near the domicile in a hotel or local accommodation, with
plenty of time for a complete sleep period before awakening at 3:30 a.m. (in
time to report to the domicile, CLT, for duty at 5:00 a.m., including local
travel). Although the possibility of obtaining high-quality sleep is likely bet-
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94 THE EFFECTS OF COMMUTING ON PILOT FATIGUE
Total Time Awake (23.5)
Activity (hours)
Flight Segments (3)
On Duty (4)
Commute (7)
Rest
(8 in bed, 7 sleep, 2.5 nap)
11:00
11:00
12:00
1:00
2:00
3:00
4:00
5:00
6:00
7:00
2:00
3:00
4:00
5:00
6:00
7:00
8:00
9:00
10:00
12:00
1:00
2:00
3:00
4:00
5:00
6:00
7:00
8:00
9:00
…
PM AM PM AM
Time of Day at Residence
Figure 5-5.eps
FIGURE 5-5 Example 3a: Unfavorable commuting pattern.
SOURCE: Based on personal testimony from stakeholders at open session meetings.
Total Time Awake (13.5)
Flight Segments (3)
Activity (hours)
On Duty (4)
Commute (7.5)
Rest
(7.5 in bed, 6.5 sleep)
| | | | | | | | | | | | | | | | | | | | |
1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 9:0010:0011:00 12:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 9:00
PM AM AM
Time of Day at Residence
FIGURE 5-6 Example 3b: Favorable commuting pattern.
ter in a bed than on the airplane, it is important to note that the very early
wake-up call for the West Coast habituated pilot may make it difficult to
obtain a full night’s rest due to the interruption of the habitual sleep period.
For the graphical representation of this example, see Figure 5-6.
Example 4: Home, Baltimore, Maryland; Domicile: Washington
Dulles International Airport (IAD), Chantilly, Virginia
Description: Same 1-day schedule for 3 consecutive days
Factors: Time awake, sleep loss (cumulative), and sleep quality
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95
PILOT COMMUTING AND FATIGUE RISK
Unfavorable: Example 4a
A pilot has the same 1-day schedule for 3 consecutive days. On the first
night preceding the assignment, the pilot goes to bed at 10:00 p.m. and
wakes at 4:00 a.m. for 5 hours of sleep (6 hours in bed). The pilot departs
home (her residence in Baltimore) at 5:00 a.m. for the 2-hour commute to
her domicile, IAD. The pilot checks in for duty at 7:00 a.m. and begins
the first of four flight legs for the day at 8:00 a.m. The pilot concludes the
duty day and leaves for the commute home at 8:00 p.m. The pilot repeats
this pattern for the next 2 days. However, on the evenings of the first and
second days, due to the commute home, the amount of sleep each night
decreases by 1 hour to 4 hours (5 hours of time in bed). For the graphical
representations of these 1-day and 3-day patterns, see Figures 5-7 and 5-8.
Favorable
Given current scheduling practices, there is no obvious favorable alter-
native to the commuting pattern for this flight schedule, and it is therefore
reflective of shared responsibility between the pilot and the airline. One
possible mitigation of fatigue might be for the pilot to take a nap between
the hours of 3:00 p.m. and 4:00 p.m. on each afternoon. The value of the
nap would be contingent on sleep quality. However, airlines also might be
able to effectively limit the negative effects of fatigue on pilots’ performance
by using both their bidding procedures and their trip pairings (including
computerized preference bidding systems) to refrain from assigning mul-
Total Time Awake (16)
Activity (hours)
Flight Segments (4)
On Duty (13)
Commute (2)
Rest*
(6 in bed, 5 sleep)
| | | | | | | | | | | | | | | | | | | | | |
10:00
11:00
12:00
1:00
2:00
3:00
4:00
5:00
6:00
7:00
8:00
9:00
10:00
11:00
12:00
1:00
2:00
3:00
4:00
5:00
6:00
7:00
8:00
PM AM PM
Time of Day at Residence
FIGURE 5-7 Example 4a: Unfavorable commuting pattern—day 1 of 3 consecutive
days. On second and third days, rest time reduced by 1 hour.
SOURCE: Based on communication with FAA officials.
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96 THE EFFECTS OF COMMUTING ON PILOT FATIGUE
Time Awake
Flight Segments
Activity
On Duty
Commute
Rest
| | | | | | |
12:00 AM 12:00 PM 12:00 AM 12:00 PM 12:00 AM 12:00 PM 12:00 AM
Day 1 Day 2 Day 3
Time of Day at Residence
FIGURE 5-8 Example 4a: Unfavorable commuting pattern—overview of 3 con-
Figure 5-8.eps
secutive days.
SOURCE: Based on communication with FAA officials.
tiday trip assignments like this one to pilots who are commuting to their
domicile, even if the commute is a driving commute of less than 2 hours.
Discussion
Commute time cannot be viewed singularly without considering such
factors as the time of the start of the duty day, the length of the duty day,
and what the pilot was doing that would add to the overall time awake at
the end of the duty day. The end result is a product of the interaction of
those factors. Pilots need to consider these several factors when thinking
about commuting in a way to minimize fatigue. What is noteworthy about
all of these examples is that the favorable commutes all cut into the pilot’s
time at home; it appears there is often a tradeoff between time at home and
beginning the duty cycle adequately rested.
RECOMMENDATION
Extensive scientific evidence exists on the negative effects of fatigue
on performance of many cognitive tasks (see Chapter 4), including those
essential for safely operating a commercial aircraft. The adverse effects of
fatigue induced by sleep loss include maintaining wakefulness and alertness,
vigilance and selective attention, psychomotor and cognitive speed, accu-
racy of performing a wide range of cognitive tasks, working and executive
memory, and on higher cognitive functions such as decision making, detec-
tion of safety threats, and problem solving, as well as communication and
mood. Fatigue is not, however, a binary condition where one is either rested
with no negative effects on performance or fatigued with severe negative
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97
PILOT COMMUTING AND FATIGUE RISK
effects on performance. There are degrees of fatigue and degrees of the
negative effects of fatigue on performance. Similarly, the effects of fatigue
on performance can vary substantially from one pilot to the next without
any untoward effects on the safety of flight.
The scientific literature shows fatigue as a risk to performance can
result from three factors: (1) being awake continuously for more than
approximately 16 hours, or (2) sleeping too little (especially less than 6
hours on the day prior to work), or (3) when undertaking work at a time
when the body is biologically programmed to be asleep (i.e., an individual’s
habitual nocturnal sleep period), which for most people is between 10:00
p.m. and 7:00 a.m. The evidence that cognitive performance is adversely
affected when the amount of sleep in 24 hours is cumulatively less than
approximately 6 hours suggests that pilots should seek to obtain sufficient
bed time to ensure they are fit for duty. The detrimental effects of fatigue
on performance may be exacerbated by a tendency for individuals to have
reduced awareness of the cognitive performance deficits that result from
fatigue.
Pilots are currently required to report fit for duty. Judging whether a
pilot is fit for duty is an individual pilot decision that should take into ac-
count the amount of sleep received prior to duty.
RECOMMENDATION 1: Pilots should avoid planning commutes or
other preduty activities that result in being awake beyond approxi-
mately 16 hours before the scheduled end of duty, endeavor to sleep at
least 6 hours3 prior to reporting for duty, and obtain more than 6 hours
of sleep per day whenever possible to prevent cumulative fatigue from
chronic sleep restriction Pilots should also consider the amount of sleep
and time awake in their decision making relative to when to inform
their supervisors that they should not fly due to fatigue.
Although there are currently no agreed-on objective standards in the
aviation industry to determine whether a pilot is reporting to duty fatigued,
there are provisions in the proposed Notice of Proposed Rulemaking for as-
sessment by others of whether a pilot is fatigued. The validity and reliability
of such assessments are unknown, as is the likelihood that they can result in
either false positives or false negatives. Consequently it is uncertain whether
they can result in effective prevention of fatigue. The proposed regulation
is discussed in the next chapter.
3 This refers to at least 6 hours of physiological sleep. Since physiological sleep is typically
85 to 95 percent of total bed time in healthy adults, time in bed for sleep will have to be 6.5
to 7 hours to ensure at least 6 hours of physiological sleep are acquired.
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