A comprehensive review of problems associated with long duration flying and some suggested remedies

Material and Methods

The study was carried out as a questionnaire study. In our literature survey we could not find any validated questionnaire for bringing out aircraft design characteristics vis-à-vis pilot fatigue. A questionnaire had to be developed anew for this study. This was done in three phases.

In the first phase, a set of questions was formulated based on preliminary discussions with pilots on problems associated with long duration flying. In phase two these preliminary questions were vetted by a panel consisting of one aviation medicine specialist, one experimental test pilot and two qualified flying instructors with a vast instructional experience with the view to ascertaining five qualities:-

1. Comprehensiveness

2. Absence of any leading questions.

3. Absence of double-barrelled questions ie two queries in a single question which might vitiate the answer.

4. Unambiguous questions.

5. No personally offensive questions.

The final questionnaire was made after incorporating inputs from the vetting panel. Subsequently, the questionnaire was subjected to a test-retest cycle to assess test-retest reliability and split half reliability. The questionnaire was administered to all fighter aircrew on base without bias to age, rank or experience. The questionnaire was kept anonymous, without any column for the name of the respondent. The final questionnaire consisted of 56 questions covering nine areas of concern.

Results

As has been mentioned above, the questionnaire had 56 questions addressing nine areas of concern which have been brought out in Table-1.

The questionnaire was returned by a total of 30 pilots. Their mean age was 30 years. Their mean flying experience was 1362 h. They had flown an average of seven long duration sorties. The maximum number of long duration sorties flown by a single individual were 23. All respondents were male, as the IAF has only male fighter pilots.

The raw data for this questionnaire was quite extensive hence it has condensed into the nine areas as mentioned in Table 1 for the sake of clarity. The condensed results for each of these categories are given at table-2.

The test-retest reliability coefficient of the questionnaire was 0.89 and the split half reliability coefficient was 0.93. 100% pilots felt that the stipulated duration of 4 hours to classify a sortie as a long duration sortie was too long. 70% of the pilots felt that the duration of a long duration sortie should be different for day and night sorties. Pilots universally agreed that introduction of autopilot would reduce fatigue to a large extent. In addition, it would also allow ease during in-flight eating (75%) as well as urination(70%), as the former requires loosening of mask and the latter loosening of QRB.

100% pilots believed that a more comfortable seat would reduce fatigue, while 30% respondents brought out that a more spacious cockpit with more comfortable cockpit geometry would also reduce fatigue. It was felt by 100% respondents that better ground and cockpit systems would reduce the workload and hence fatigue. The pilots specified improvement in navigations systems, recovery systems, aircraft health monitoring systems, situational awareness systems, GCA and ILS as systems which would reduce fatigue. Another issue brought out by all pilots was better living conditions at home and work. These included a reliable electrical supply, water supply, better quality furniture etc. It also included easier procurement of spares, flying clothing etc. A mention was also made of better administrative services by 100% respondents.

All the respondents placed a large emphasis on physical fitness. Most respondents considered themselves quite physically fit. On the other hand, the total time devoted to physical activity was only 3-4 h per week. Boredom as an important issue in long duration sorties was brought out by 100% of the respondents. Most pilots felt the need for boredom alleviation strategies. Nearly 60% of pilots use some sort a boredom alleviation strategy in the cockpit.

Discussion

Majority of pilots felt that four hours was too long a duration for a sortie to be called long duration. This is noteworthy, because it is different from world literature. For the F-16 the USAF has determined an 8-hour period as a long duration sortie [6]. On the other hand, the Jaguar is the only single seat aircraft involved in long-duration flying which does not have an autopilot. Another issue brought out by the respondents was about the difficulty of a particular sortie. It was brought out that while for a ferry sortie a 4 hour sortie may be quite comfortable, for a sortie with multiple aerial refuellings and combat situations even 2-3 hours is quite fatiguing. It has been established that disruption of circadian rhythm is much more fatiguing [7]. This finding was confirmed in the present study where a majority of the pilots felt that a night sortie of the same duration is more fatiguing. Another factor that may have contributed to this is that a night long duration sortie also involves night aerial refuelling, which is a tough exercise in itself, especially in the Jaguar.

The conjecture made above was substantiated by pilots who brought out universally that the fatigue would be reduced by introduction of an autopilot in the aircraft. The lack of autopilot also hampered other activities which are considered routine in other aircraft. Loosening the mask and eating an inflight meal is an uphill task without an autopilot, especially if the food is elaborate or messy. A majority of pilots agreed that they would be willing to compromise on taste and quality of rations provided it was easy to eat. For this reason, most pilots preferred chocolates to a more substantial meal for sorties lasting for less than 4 hours. However, for sorties of a longer duration, they said they preferred different and more wholesome rations like a sandwich or 'parantha' roll. Despite this a large number of pilots asserted that they would prefer not to eat in the absence of an autopilot as it may be a flight safety hazard.

Pilots were questioned about their preferred method of in-flight urine disposal. Most pilots agreed that the adult diaper suggested by some authors [7] is not an appropriate method for urine disposal. Most respondents brought out that they had never used the diaper for in-flight urination. In the aircraft in question, the negative-G strap is a thick flat strap that presses on the crotch. Thus urination requires loosening of the QRB, which in the absence of an autopilot, is difficult if not impossible. The respondents felt that a better designed and comfortable cockpit, better seat, arm rests etc. would go a long way to reduce fatigue due to long duration flying. Again, reduction in cockpit workload using better displays, fail-safe systems, ground and air base navigational aids, GPS and ILS would reduce fatigue. It is noteworthy, that most modern aircraft tasked with long duration sorties have all these features.

Pilots brought out that adequate infra-structure facilities both at home and at work reduce fatigue and this is transferred to the cockpit. Thus, when the infrastructure is adequate long-duration sorties are tolerated better. All respondents emphasized the importance of physical fitness in combating the stresses of long duration flying. Most respondents also felt that they were adequately physically fit. Surprisingly, the average duration of time spent by pilots on physical fitness turned out to be only 3-4 hours per week. This indicates that though the pilots felt that they may be physically fit, their average level of fitness could not have been high.

Boredom appears to be an important and hitherto un-addressed issue in long-duration flying. Most pilots felt that if long duration flying is to be the norm then active measures are required to be taken to alleviate boredom. It is interesting that our literature search did not indicate that any other Air Force is doing active research into boredom alleviation. 60% pilots mentioned that they use some strategy for boredom alleviation in the cockpit, like singing, talking to oneself, talking on R/T. There is, however, no teaching/discussion in the squadrons about how to alleviate boredom. In addition to the points brought out above, other factors contribute to the fatigue resulting from long duration flying. Thomas et al have concluded that eastward ‘back of clock’ flights induce much more fatigue than westward flights [8]. Gowron et al [9] have brought out the importance of a good night’s rest prior to long haul operations for reducing the amount of fatigue. They advise at least 12 hours rest of which 7-8 hours must be spent in uninterrupted sleep. Pharmaceutical countermeasures have also been suggested by some authors [6].

Conclusion

Long duration flying poses various problems, which increase with increasing number of exercises and increase in duration. However, a large amount of problems and associated fatigue may result from the man-machine interface or the lack of it. The Jaguar being an older aircraft, these problems are more and varied. This study thus provides an insight into two areas. One is to be able to help reduce problems with long duration flying in the Jaguar aircraft. The second equally important idea is to help create a database of problems associated with various aspects of man-machine interface, which would help in future aircraft design.