A novel approach to encouraging proper fatigue management in British Army aviation training and operations

Transcription

1 THE AERONAUTICAL JOURNAL JUNE A novel approach to encouraging proper fatigue management in British Army aviation training and operations R. P. King School of Army Aviation Middle Wallop, UK ABSTRACT Fatigue management in military aviation remains problematic and can be easily neglected by planners and aircrew in a busy operational environment. The basic assessment tool (BAT) is an objective and educational computer tool for evaluating and combining various fatigue factors. It provides an impartial performance comparison while at the same time educating and reminding its users of the importance of fatigue management. Individual factors of the BAT were chosen because they affect fatigue, sleepiness, alertness and performance. A short explanation of components not chosen is also included. An example of how the BAT can be used is described and figures of the resulting outputs (screenshots) are included. Most commercial fatigue estimation products are subjective and do not consider specific issues associated with tactical operations in a field environment. This novel approach can be used to help plan missions by minimizing the BAT score while still maximising the tactical advantage and keeping fatigue management fresh in the minds of military rotary wing pilots while in training and on operations. Although the BAT is military aviation focused and objective, it can be easily modified to suit particular fatigue concerns. 1.0 INTRODUCTION Fatigue remains a major problem in military aviation and some sources attribute between 21 and 70% of all aviation accidents directly or indirectly to fatigue (1,2). With the acquisition of the Apache helicopter, the British Army Air Corps was faced with a new weapons platform that was designed to exploit its advantages in the dark. This meant that, unlike other aircraft in their inventory, this helicopter would need to be flown primarily at night both in training and on operations. Since nocturnal flying activities carry with them additional risks not present during the day, Army Air Corps pilots have asked for a concise resource from the Army Aviation Medicine community and it has responded by creating an easily accessible reference document for use by pilots, flight planners and commanders. Entitled the Visual and Manned Performance in Illumination Reduced Environments, or VAMPIRE, the purpose of this reference was to remind soldiers of the additional problem they face when flying at night and covers visual, fatigue and environmental issues. The information has been placed on a self-starting (autoplay) compact disk with reference material. Ready made slide presentations for instructors to modify or use directly to help teach the dangers of nighttime operations are also available. Further to the fatigue portion of the guide, a basic assessment tool (BAT) was developed to help highlight the major aspects that impact alertness and could be used to create a relative objective comparison, or fatigue factor, of aircrew to determine which might be relatively less fatigued. In the past, attempts have been made to model fatigue and provide predictive fatigue ratings to help plan missions. This has been particularly important in aiding the risk mitigation strategies for long-haul flights (3). However, most fatigue assessment tools that are currently available to the individual are subjective and aircrew typically underestimate the impact of fatigue on themselves; thus self-assessment of alertness has always been fraught with inaccuracies (4,5). A wide range of military and commercial fatigue scheduling tools are available but these tend to be very complex and may not be flexible enough to cope with the stress of unscheduled attack or defence missions and other activities that occur on a very fluid modern battlefield. Paper No Manuscript received 11 April 2005, accepted 11 May 2005.

2 294 THE AERONAUTICAL JOURNAL JUNE 2005 The BAT, which is simply a Microsoft Excel based spreadsheet that calculates a fatigue score, should not be seen as an absolute indication of fatigue and has not yet been validated against existing sleepiness and fatigue scales. Rather it should be used as a further tool to make the aviation community aware of those factors that will impact their performance in flight and as an aid to operational decision-making. 2.0 COMPONENTS The major components used to create the BAT were chosen after a review of available literature and consensus formation by the author and UK Army aviation medicine specialists. In developing the BAT, consideration was first given to those factors that should not be covered. Research has shown that individual susceptibility to the effects of sleep loss varies considerably from person to person (6) so the goal was not to create a performance prediction based on fatigue history or mission requirements. In the past, the notion of directional asymmetry, which implied that phase delays (westward travel) were better tolerated than phase advances (eastward travel), existed but now research seems to suggest that phase direction may not be a factor (7,8). Since this phase direction as a factor in circadian disruption is currently being questioned, it is not included in the BAT. Gender was not included as a variable in this calculation because US Army research has shown no gender effect from sleep deprivation or continuous tasks in military aviators (9). Medication usage (i.e. stimulants, sedatives) as a fatigue countermeasure is not included as there are currently no regulations in place sanctioning their use in flight for the British Army Air Corps. Diet is also excluded in this calculation as research has not yet borne out the effectiveness of diet in dealing with sleep or circadian disruption (5,10). Proper nutrition, however, though not specifically as a fatigue countermeasure, is always recommended. The following components were chosen for the BAT calculation based on their operational importance, educational impact and scientific merit. Additionally, some of the factors that could be modified by planners and operators were highlighted. Sleep loss has a negative effect on the performance of cognitive tasks (11). Obviously, the BAT needed to include some way of stressing the importance of sleep. However, with the increasing evidence underscoring the dangers of sleep debt (2,12,13,14), the dangers of accumulated sleep loss also needed to be accentuated. In the BAT, multiple days at less than the ideal eight hours of sleep will lead to point penalties (5,14). The creation of desynchrony between the body clock and environmental cues that occurs when travelling through multiple time zones, or jet lag, was felt to be an important factor for deploying military Table 1 BAT without any pilot input.

3 KING A NOVEL APPROACH TO ENCOURAGING PROPER FATIGUE MANAGEMENT units as it is with long and short haul operators (14). A globally ready squadron should be given a way to assess the dangers of jet lag and so a variable that accounts for zone shift as well as time in the new zone is included. The BAT also allows for one hour of adjustment for every day spent in the new time zone to decay the effect of jet lag (3,15). Furthermore, human circadian pacemakers are set to coordinate regular physiologic and behavioural functions and exhibit a physiologic nadir between 0300 and 0500hrs. Activity during this time reveals a great performance penalty and this fact has been stressed in the calculation (5). Since working extended shifts has been shown to cause a significant increase in vehicular accidents and near misses (16), a variable for extended duty hours and wakefulness is included. In particular, any activity beyond 16 hours of continuous wakefulness will be subject to a performance penalty equivalent to having two drinks of alcohol (17). Overall, soldiers tend not to perform as well when wearing chemical and biological protective equipment. The addition of sleep loss and fatigue worsens this performance decrement (13). Thus, the BAT includes the requirement to fly with chemical and biological protective equipment as an important factor in the total equation. The additional physical strain of supporting extra weight on the helmet combined with the continuous scanning technique required for successful use of helmet mounted night vision devices reveals another operational source of tiredness (18,19). Eyestrain from frequent difficulty in interpreting infrared or image-intensified scenery also compounds this fatiguing effect. Thus, the use of night vision devices is added to the overall equation with the caveat that Apache crews will always have these points assessed against them since they always fly with a helmet-mounted sight. Sleep studies in climatic extremes have shown that environment is not only important in the initiation of sleep, but also in obtaining quality, undisturbed sleep (20,21). As units deploy to a training or operational theatre (e.g. desert, arctic), many pilots are housed in less than optimal accommodations, frequently tents without climate or lighting controls. The inability to control the sleeping area or extremes of environment has been included in the calculations to help bring out the importance of pilot accommodation. Strenuous exercise has been shown to increase the incidence of slow wave EEG activity, an indicator of sleepiness, in subjects (up to 50 minutes after exercise) and although it did ameliorate some fatigue in the short term (up to 30 minutes after exercise) there was no improved performance compared to those who did not exercise (22). This should give units reason to exclude pilots who are at risk for developing fatigue from strenuous exercise whenever operationally possible. Hence, an input for the presence of strenuous exercise for more than 30 minutes since last awakening is included. Figure 2 BAT with first sortie data.

4 296 THE AERONAUTICAL JOURNAL JUNE 2005 Several studies support the use of naps as a countermeasure in sustained operations or shift work (14,23,24). In most cases, nap length is not important, ranging from ten minutes to two hours. Rather than complicating the calculation with nap length, which is difficult for an individual to estimate, only the presence or absence of a nap is queried. The importance of napping is further highlighted in the BAT by the fact that a perfectly refreshed individual without a nap still incurs a point penalty. Acute tiredness is the final step in calculating the BAT fatigue factor. It became important to point out that mission length could be an acute concern so any total mission times over two hours incur additional penalties. This was discovered as an important factor while interviewing instructor pilots who had tested the BAT. They reported instances of hot refuelling while students were changed without the instructor being given a chance to get out of the aircraft. Finally, successive missions during the same awake period are added at the top of the BAT with some washout of acute fatigue when a break between flights is given. Calculations with the BAT are best made before the mission is planned to help commanders, planners and operators in crew pairing and risk mitigation strategies before the mission is flown. This estimation is performed by computing a fatigue factor for the individual based on those critical elements of their past history (or projected data) as well as mission factors detailed above. Once completed, the BAT fatigue factor for one pilot can be compared to others and aid commanders and mission planners in crew selection, mission selection and crew pairing. It has been suggested that proper military sleep management during combat should strive to avoid exhausting all personnel at the same time (24). Thus, if faced with two pilots with relatively high BAT scores and two with relatively low ones, the smart mission planner might choose to pair the fatigued individuals with less fatigued co-pilots. 3.0 EXAMPLE Table 1 shows what the BAT looks like when set to zero you will notice that a score is still indicated and this is simply because when reset to zero, the box for naps is unchecked and one is already a bit fatigued because of this. In Table 2, a British Apache helicopter pilot has put in his data for a 90-minute night mission commencing at 2300hrs local. He has been in Canada (GMT +8) for three days and has not slept very well in his very cold (it is January) tent. He also participated in some ammunition and supply off-loading for 45 minutes this morning that was quite strenuous but he managed to take a nap in the afternoon. Upon successfully completing his mission, the pilot returns to find that he has been scheduled for the next sortie as well because Table 3 BAT with second sortie data.

5 KING A NOVEL APPROACH TO ENCOURAGING PROPER FATIGUE MANAGEMENT the original crewman has developed a severe upper respiratory tract infection. Table 3 now shows his score with the additional fatigue from the previous mission while Table 4 shows his commander s BAT score who has been in country longer, did no off-loading and has slept fairly well. If mission planners using the BAT realise the difference in fatigue and at least consider sending the unit commander, rather than this already fatigued pilot from Table 3, on this next mission, then the BAT would be considered a success. 4.0 DISCUSSION Although the idea of a fatigue estimation calculator for aircrew is not new (3), most of the systems in use or currently being developed tend to be very complex and time-consuming. The aim of this tool was to create an objective fatigue estimator that could be completed quickly on a PC in the squadron and, while not providing validated absolute fatigue scores, does help to heighten fatigue awareness of commanders, planners and pilots. Additionally, many of these commercial products do not consider specific issues associated with tactical operations in a field environment (e.g. night vision devices use, weather extremes and biological/chemical protection use.) To its credit, the BAT is composed of characteristics that have all been individually validated as important factors in determining fatigue. The BAT is only one tool to help combat the problems intrinsic to nighttime operations and should be used in conjunction with local medical advice whenever possible. The results derived from its use must always be tempered with tactical necessity and mission requirements and should not be used to label a mission too risky to perform. It is important to remember that although the individual components were chosen because they have been shown to affect fatigue, sleepiness, alertness and performance, the BAT has not been validated or tested against other fatigue measuring instruments. Thus, there are no absolute BAT results that should be used to discriminate or cancel missions due to fatigue. 5.0 CONCLUSIONS: The author believes that this fatigue assessment tool will be useful in two significant ways: 1. it will enable mission planners and operators to objectively discern aviators with relatively more fatigue, 2. it can be used as a educational (or re-educational) tool to highlight important factors in fatigue management. Table 4 Commander's BAT output.

6 298 THE AERONAUTICAL JOURNAL JUNE 2005 A future project will involve comparison and validation of this tool against other fatigue estimation systems that are already in existence. Furthermore, if the BAT is widely adopted and used, it could be used retrospectively to analyse the contribution of fatigue in accident investigations as well. A simple calculator like this could also be adapted to a number of other workplace environments. Certainly, military fixed-wing operators could easily modify the BAT for their use but other transport industries such as rail, shipping and commercial road transport could make use of this approach. Furthermore, this approach need not be limited to vehicle operators; other work environments where fatigue may be an issue could also benefit (e.g. air traffic control, nuclear power plants, hospitals, police and other emergency responders.) Since the programme is relatively simple to modify and expand, the development of BAT variations for other occupational environments should be encouraged. ACKNOWLEDGEMENTS The author is indebted to the pilots of the British Army Air Corps for their contributions in flight testing this fatigue tool. I would also like to thank my fellow Specialists in Aviation Medicine in the U.K. who helped identify and prioritise the various fatigue factors. Disclaimer: The views and opinion are those of the author, and do not necessarily represent the views of the US Army, the Department of Defence, the British Army or the Ministry of Defence. REFERENCES 1. CALDWELL, J.A., GILREATH, S., ERICKSON, B. and SMYTH, N. Is fatigue a problem in army aviation? The results of a survey of aviators and aircrews, December 2000, United States Army Aviation Research Lab Report No , Fort Rucker, AL. 2. DRAKE, C.L., ROEHRS, T.A., BURDUVALI, E, ET AL. 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