For the
modified shift work schedule based on the example provided of a 4-crew 24-hour
MALE UAS operation, the objective is to provide the aircraft and payload
operators with sufficient rest between shifts and the ability to maintain
constant availability for mission readiness. The current shift of 6 days on/2
days off rotates in a clockwise fashion, i.e. each crew will work for 6 days,
take 2 days off, then shift forward to the next block.
 |
| Figure 1. Original shift schedule, 8-day portion. |
There have been several studies
conducted of rotating shifts and their effect on fatigue, most notably in the
air traffic control industry. There are several recommendations to add to the
MALE ISR shift schedule, and several operational constraints that prevent full
implementation of the recommendations.
The overall recommendation is to
shorten the number of consecutive shifts and more rapidly rotate through the
shift schedule. The current clockwise shift rotation (day-swing-night) is
preferable to counter-clockwise, because it is analogous to flying east-to-west
during air travel. Recovering from jet lag has been shown to be significantly
easier when flying east-to-west because of our 25-hour circadian rhythm.
Because the time zone is earlier on arrival, the day is longer, which matches
the natural circadian rhythm more closely (Lu, et. al, 2016). Rotating on a
2-day shift schedule (2-2-2) with 2 days off following the night shift has been
shown to maintain a generally diurnal circadian rhythm, and is currently used
by USAF air traffic controllers (Luna, French, Mitcha, & Neville, 1992).
 |
| Figure 2. Revised 2-2-2 shift schedule. |
Additional steps can be taken to reduce
pilot fatigue on the various shifts. The 1992 study by Luna, French, Mitcha,
and Neville (title) showed that
subjective fatigue levels were higher on the night shifts in a 2-2-2 schedule.
For the night shift, the main recommendation is to maintain a cool environment
to encourage alertness. Another recommendation is to provide caffeine at the
beginning of the shift to increase alertness, as the lowest levels of alertness
occurred in the first 30 minutes of the night shift (Luna, French, Mitcha, and
Neville, 1992). An additional recommendation is to provide tasty, nutritious
foods around the clock so that night shift workers do not have to rely on
frequent snacks for hunger satisfaction. Exercise was also shown to improve
alertness on every shift, and it was recommended to provide access to a
stationary bicycle or treadmill for crews in confined spaces (such as ships or
small bases).
One recommendation was to lengthen the day or swing shifts
and shorten the night shifts. However, most aviation units limit pilots to 8
duty hours in a 24-hour period, so that is not practical with this current crew
schedule. Another consideration is the frequent shifting of mission times
throughout each day and potential loss of fidelity while performing ISR tasks
such as long-term observation of a target. The handoff briefs between shifts
should be very thorough and specific, with a script provided for each crew to
follow with a list of tasks and items that must be briefed to prevent
fatigue-induced mishaps.
One additional risk to any rotating screw schedule is the
potential for sickness or injury that prevents a crew from performing normal
duties. 4 crews rotating on a 3-shift schedule is the minimum number needed for
mission readiness; if one crew is sick for 24 hours or longer, the impact of
schedule disruption will be felt by all crews. The final recommendation is to
post one additional crew, which will facilitate an additional day off after the
night shifts and provide backup in the event of illness or injury to a
crewmember.
References
Cruz, C., Detwiler, C., Nesthus, T., and
Boquet, A. (2003, June). Clockwise and counterclockwise rotating shifts:
effects on sleep duration, timing, and quality. Aviation, Space, and Environmental Medicine Journal, 74(6), pp.
597-605. Oklahoma City, OK: Federal Aviation Administration.
Lu, Z., Klein-Cardeña, K.,
Lee, S., Antonsen, T.M., Girvan, M., & Ott, E. (2016, July). Resynchronization
of circadian oscillators and the east-west asymmetry of jet lag. Chaos, 26. doi: http://dx.doi.org/10.1063/1.4954275
Luna, T.D., French, J.,
Mitcha, J.L., & Neville, K.J. (1992, September). Forward rapid rotation shiftwork in USAF air traffic controllers:
sleep, activity, fatigue, and mood analyses. Brooks Air Force Base, TX: Air
Force Materiel Command.
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