An Analysis of Shift Schedule Rotations to allow for 24/7 UAS Operations
Conducted by 4 Teams
Robert J. Winn
Embry-Riddle Aeronautical University-WW-ASCI 638
Abstract
This research paper will present an analysis of a shift schedule for a MQ-1B Medium Altitude, Long Endurance (MALE) UAS squadron of the United States Air Force (USAF). The schedule, based on a 6 days on, 2 days off rotational format in order to accommodate missions conducted 24/7, 365 days a year providing armed, Intelligence, Surveillance, and Reconnaissance (ISR) to forces operating in country. In order to accomplish this mission, the UAS crews were divided into 4 teams and assigned a shift work schedule of 6 days on, 2 days off. Under this shift schedule crew members have reported extreme fatigue while conducting operations due to a lack of quality sleep. In order to optimize operations a revised shift schedule will be introduced in order to address the fatigue issue reported by the crews. In conclusion, an analysis of the current schedule will address the pros and cons compared to the revised shift schedule.
Keywords: fatigue, inadequate sleep, optimized operations, shift schedule,
An Analysis of Shift Schedule Rotations to allow for 24/7 UAS Operations
Conducted by 4 Teams
The introduction of long-endurance unmanned aircraft systems (UAS), such as the MQ-1 Predator and MQ-9 Reaper, has necessitated the routine implementation of shift work for United States Air Force (USAF) UAS crewmembers in order to provide the necessary around-the-clock staffing of ground control stations (Tvaryanas, 2008). A current 4 team shift schedule to accommodate 24/7, 365 days a year operations by MQ-1B USAF crews has introduced reports of increased fatigue attributed to inadequate sleep. The 2 cycle shift schedule requires 4 crews to alternate between 12 hour day (1st cycle) and night (2nd cycle) shifts by working 6 days on then two days off and then rotating to the alternate 12 cycle for the next 6/2 rotation.
A study by Barnes & Matz in 1998, found Army UAS operators preferred longer over shorter rotations because they perceived the longer rotations allowed for better situational awareness of the tactical environment (Tvaryanas, 2006). It could be that the longer rotation preferred by the crews was to that of the shift duration (12 hours) and not to the cycle of six days on. Another study showed that shift-working crewmembers in a Predator UAS squadron had significantly increased fatigue, emotional exhaustion, and burnout relative to traditional aircrew from another “high-demand, low-density” weapon system. The squadron work schedule was redesigned, but preferred shift work practices were not fully implemented because of manpower constraints and crewmember preferences (Tvaryanas, 2008).
Fatigue/Stress
Fatigue is a “State of diminished Physical or mental efficiency”. Fatigue can be triggered by previous perceived stress which may lead to impairment of performance and function (Kocalevent, 2011). The state of being fatigued has an effect on an individual’s capability to handle given levels of stress. The major causes of fatigue are; Sleep Loss, Work Schedule, Circadian Rhythm Disruptions, Recreational or Extracurricular Activity
Stress is a complex phenomenon brought about by the pressures that life or a given situation present. Factors that affect stress are Individual, Environmental and Occupational. The inability to socialize with family and community can exacerbate individual stressors, those stressors can compound issues attributed to increased fatigue brought about by diminished physical or mental efficiency. How an individual handles stress can have a direct effect on the individual’s ability to decompress, get restful sleep and recharge both the physical and mental state of being.
8 vs. 12
Numerous studies have concluded that for each hour past an 8 hour shift the risk and potential for error increased by one. These errors were also more likely to occur during a night shift where disruption of natural circadian rhythm occurs. In order to minimize the overall risk on a shift system we need to consider the number of successive night shifts, the length of the night shifts and the pro-vision of breaks within them (Tvaryanas, 2008). Additional studies found that a 12 hr. night shift that included frequent rest breaks might well prove safer than a shorter 8 hr. night shift with only a single, mid-shift break. Likewise, the length of the night shifts and the number of successive night shifts involved in a shift system will act in combination to determine the overall risk on that system (Folkard, 2003).
Work Cycle Duration
Shift worker fatigue has been described as a function of shift timing, length, frequency, and regularity as well as intrashift and intershift recovery opportunities (Tvaryanas, 2008). Shift workers experience a wide range of problems from acute disturbances of circadian rhythms and sleep to diminished family and social lives (Tvaryanas, 2008). If the number of successive night shifts is directly attributed to errors brought about by fatigue and circadian rhythm disruptions, than it would stand to reason the current 6 day on -2 day off cycle is not the optimal schedule for ensuring safe UAS operations. Therefore a revised shift schedule to accommodate the 4 UAS teams has been developed.
2-2/3-2/2-3 Rotating Shift Schedule | 24/7 Shift Coverage
The length of the night shifts and the number of successive night shifts involved in a shift system will act in combination to determine the overall risk on that system (Folkard, 2003). Implementing a 2-2/3-2/2-3 rotating shift schedule using 4 teams (crews) and 2 twelve-hour shifts to provide 24/7 coverage provides the individual crews with less exposure to prolonged 12 hour night shift rotations (Figure 1). Implemented over a 4-week cycle each team works 2 consecutive day shifts, followed by 2 days off, returning to work for 3 consecutive day shifts, followed by another 2 days off, then returning for another 2 consecutive day shifts, followed by 3 days off duty. The cycle then repeats itself but the crews are then assigned to the night shift for the same 2-2/3-2/2-3 cycle.
Figure 1. 2-2/3-2/2-3 rotating shift schedule Retrieved from http://www.bmscentral.com/learn-employee-scheduling/2-2-3-2-2-3-rotating-shift/
It should be considered that although the shift durations are in 12 hour increments a minimum of 15 minutes of overlap would be added by the outgoing dayshift crew in order to provide for a positive hand-off to the gaining night shift crew.
Pros • No employee works more than three consecutive days
• 3-day weekend every other weekend
• Taking 2 vacation days on one of the 2-day work week gives 7 days off
Cons • Could work up to 62 hours in one week
• Long shift length (12 hours)
• Requires an average of 2 overtime hours per employee per week
(BMS, 2015)
Conclusion
M.J Thorpy presented in the Journal of Family Practice, (V59, No.1, 2010), that there was a marked increase in the risk for incidents during working hours suggests that working more than 4 consecutive 12-hour night shifts should be avoided. Therefore, shift crews should be made aware that a potential exists for increased errors towards the end of a 12 hour shift. Shift schedules should rotate clockwise rather than counterclockwise manner as it has been found easier to change the sleep/wake cycle to a clockwise shift rotation, as this follows the natural adaptive pattern of delaying the sleep period. Additional ways to improve the sleep –wake cycle is to improve shift-work conditions, such as bright light exposure and appropriately timed naps.
Dr. D. Schroeder presented in a 2008 FAA Fatigue Management Symposium the following:
Summary
• No single shift rotation plan can entirely resolve the work and rest scheduling demands placed on individuals
• Discussion of specific advantages and risks difficult due to great diversity of flexible and irregular hours
• Given the variability of flexible hours, focus should be on the actual working hours of employees and the timing of their sleep
Recommendations
• Employ ergonomic principles of scheduling as possible
• Shift rotation time should be no less than 10 hrs
References
BMS, Business management Systems (2015), 2-2 3-2 2-3 Rotating Shift Schedule | 24/7 Shift Coverage Retrieved from http://www.bmscentral.com/learn-employee-scheduling/2-2-3-2-2-3-rotating-shift/
Kocalevent, R. D., Hinz, A., Brahler, E., Klapp, B. F., (2011) Determinants of fatigue and stress Research article from BMC Research notes 2011, 4:238 Retrieved from http://www.biomedcentral.com/1756-0500/4/238
Folkard, S., Tucker, P.T., (2003) Shift Work, Safety and productivity Retrieved from Department of Psychology, Swansea University, Swansea, Wales, United Kingdom Occupational Medicine (Impact Factor: 1.03). 04/2003; 53(2):95-101. DOI: 10.1093/occmed/kqg047
Schroeder, D. Ph.D., (2008) Sleep/Wake Cycles and Performance of ATC Operators Presented at the FAA Fatigue Management Symposium, June 17-19, 2008 Retrieved from http://www.faa.gov/about/office_org/headquarters_offices/avs/offices/afs/afs200/media/aviation_fatigue_symposium/SchroederAppComplete.pdf
Thorpy, M.J., (2010) Managing the patient with shift-work disorder, Supplement to the Journal of Family Practice, Vol 59, No 1., January 2010, Retrieved from http://media.mycme.com/documents/29/culpepper_2010_swd_suppl_7021.pdf
Tvaryanas, A.P., Lopez, N., Hickey, P., Daluz, C., Thompson, W. T., Caldwell, J.L. (2006) Effects of Shift Work and Sustained Operations: Operator Performance in Remotely Piloted Aircraft (OP-REPAIR) Retrieved from http://www.wpafb.af.mil/shared/media/document/afd-090121-043.pdf
Tvaryanas, A.P., Platte, W., Swigart, C., Colebank, J., Miller, N.L., (2008) A Resurvey of Shift Work-Related Fatigue in MQ-1 Predator Unmanned Aircraft System Crewmembers Retrieved from http://www.dtic.mil/get-tr-doc/pdf?AD=ADA477976
