UAS
Shift Work Schedule
Shawn
M. Wyne
ASCI
638 – Human Factors in Unmanned Systems
Embry-Riddle Aeronautical
University
Abstract
The long duration of
Unmanned Aircraft Systems (UAS) flight creates a new phenomenon for aviation.
With aircraft that can stay aloft as much as 40 hours at a time, pilots and
flight crews must operate in shifts to accomplish a mission. In a military unit
that controls multiple UAS at a time, personnel manning must be sufficient to
cover 365/24/7 operations. Like other professions that have no down time, such
as police and hospital nurses, a schedule must be created for employees to
cover multiple shifts. This paper analyzes a current UAS squadron’s shift
schedule and proposes changes for the purpose of decreasing fatigue among
flight crews.
Keywords: UAS, fatigue, shift work, schedules
UAS
Shift Work Schedule
A United States Air Force
(USAF) UAS squadron operating MQ-1B Medium Altitude, Long Endurance (MALE)
aircraft operates 24/7, 365 days a year. The crews in this squadron are
assigned to four teams on a continuous shift work schedule of six days on, two
days off (Figure 1). Unfortunately, crews have been reporting excessive levels
of fatigue, and complain of inadequate levels of sleep due to their schedule.
Fatigue is a problem, especially when operating aircraft, because it has been
shown to adversely affect performance (Wickens, Gordon, & Liu, 1998). Previous
research indicates nearly 50% of UAS operators meet the threshold for levels of
daily sleepiness that is expected to negatively affect job performance and
safety (Tvaryanas, Platt, Swigart, Colebank, & Miller, 2008). A new
schedule is presented to accommodate known issues related to fatigue resulting
from shift work.
The current schedule
causes excessive levels of fatigue in its participants because of several
reasons. The first reason is because the schedule disrupts crews’ circadian
rhythms. Circadian rhythms are physiological responses to the wake/sleep cycle,
and when they are desynchronized from nature they body physically feels sleepy
when the worker is trying to be awake (Wickens, et al, 1998). A certain amount
of disruption is inevitable when work must be accomplished overnight. But the
body can adapt, which takes 4-5 days to occur (Wickens, et al, 1998).
Unfortunately, the current schedule provides only six days on a particular
shift, and then the shift is altered. The crews are not provided with
sufficient time on a particular schedule to adapt before their schedule changes
and they must start over. Longer periods of maintaining a particular shift will
allow crews the chance to adapt to their schedule.
The second problem with
the current schedule is that is allows repeated states of sleep loss. The
six-on two-off schedule provides insufficient time to recover from a sleep
deprived state. A typical Monday through Friday worker has an average of 21.8
days of work and 8.7 days off per calendar month. The current UAS squadron
shift results in 24 days of work and 6 days off each month. Deprivation of
sleep that occurs when trying to work against circadian rhythms can build up
over time, resulting in a cumulative sleep debt (Wickens, et al, 1998). More
days off, or more frequent days off, will allow crews to recover from lost
sleep during the work week.
The first change to the
new schedule is to alter the team arrangement. Four teams will be consolidated
to three. This way, each team can be assigned to a single shift at a time
(Figure 2). The team will maintain that shift for a longer period of time. Fast
rotations of shifts are poor for circadian rhythm management. But staying on a
single shift for excessively long periods of time can also be bad. Long periods
of a single shift is only effective if crews can maintain their sleep schedule
even during days off (Tvaryanas, et al, 2008). This might be achieved in a
deployed scenario where there is little to do outside of work. Realistically
this is not probable considering crews have families and other priorities
outside of work. The new schedule will rotate shifts every six weeks.
The second change to the
new schedule is to alter the number of days each crew works. Since a single
team covers a single shift, crews within the team must alternate work and off
days to ensure enough workers are present each day. The previous schedule of
six-on, two-off will be replaced with a four-on, two-off rotation (Figure 3).
This schedule yields a monthly total of 20 work days and 10 days off. The
increased frequency and quantity of off days allows more opportunities to
recover from sleep debt. The rotation still keeps the same numbers of workers
on the shift any particular day as the six/two shift. This type of manning
schedule, called a waterfall, has overlap during the transition week when one
team moves onto its new shift (Figure 4). But the shifts are still covered with
the same number of crews.
Any changes to the
shift schedule are only a partial solution. Increased manning would provide
significantly more opportunity for breaks in the schedule for single
crewmembers, giving greater opportunities for vacation or alternate duties that
do not require shift work. The new schedule gives longer periods on a particular
shift to acclimate to the schedule, and also provides more breaks. Both of
these should contribute to decreased problems with fatigue and have an overall
positive impact on crew performance compared to the old schedule.
References
Tvaryanas,
P., Platte, W., Swigart, C., Colebank, J., and Miller, N. (2008). A Resurvey of Shift Work-Related Fatigue in
MQ-1 Predator Unmanned Aircraft System Crewmembers. Monterey, CA: Naval
Postgraduate School.
Wickens,
C, Gordon, S, and Liu, Y. (1998). An
Introduction to Human Factors Engineering. New York: Addison Wesley
Longman, Inc.
Figure
1. Current
Squadron Shift Schedule.
Figure
2. New
Team Arrangement.
Figure
3. New
Crew Schedule.
Figure
4. Transition
Weeks.
