Every flight, every day is packed with variables that present some risk to the successful completion of that flight. One variable we can actively mitigate is pilot fatigue. Articles on the topic have been in the mainstream media for months, with new rest regulations coming for airline pilots. The new regulations address only crew rest requirements, not with other factors (like the interruption of circadian rhythm and physiology)that contribute to fatigue. Length of the rest period is important, but we must also beware of other factors.
Dozing off in a meeting could be a career killer. Dozing off in the cockpit could be a killer, period. Insufficient rest is obviously a major element of pilot fatigue. A friend who flies for a major carrier explained how their rest time worked. In theory, they had eight hours with that rest time beginning at a set time after the aircraft landed and ending at a set time before it departed again. In reality, they had far less than the eight hours. Let’s say the hotel van is 30 minutes late and it’s another 30 minutes to the hotel. The crew now has seven hours of rest available. Going back to the airport, the crew has to fit their schedule to the hotel’s shuttle; so, if the crew needs to leave on the half hour but the van leaves on the hour, they leave an hour and a half before they need to be at the airport. The crew now has five and a half hours of rest time. Throw in some time searching for dinner or breakfast and how much actual “rest” time is that crew getting? Not much. How was this airline crew rested enough to fly? The new regulations have rest time basically starting and ending at the hotel. When the regulations go into effect, they will give the crew a much better chance at actually getting meaningful rest. While rest requirements for Part 135 are already greater than those for airlines, the shuttle, drive time and food issues are easy to forget when planning rest periods for our crews, as well. Also easily forgotten are the fatigue contributions made by interruption in circadian rhythm and by physiology.
Humans are diurnal with circadian rhythms oriented to sleeping at night. Aviation is a 24-hour industry; so, of course, there are going to be times when flight schedules directly oppose sleep schedules. With the exception of red-eyes and international flights, most scheduled service flights coincide with normal sleep schedules. However, for maximum crew scheduling efficiency, crew schedules contain some number of CDO or nap lines. Friends flying for both regional and legacy carriers have told me that the inconsistencies of those lines can be brutal after awhile. Freight flies largely at night; so, I suppose you could say that the crews could train their bodies to operate on a different rhythm, the way most shift workers do – you know those people who defined Shift Work Sleep Disorder. That might need a little review, as well. Like scheduled flights, most charter operates within normal rhythm, with the notable exception of life flights, which are almost always at some hideous hour. I have yet to hear of a regular charter operator that can afford to hire a full-time crew whose sole responsibility is to fly life flights. As a result, crews have schedules that are all over the clock and all out of rhythm. Most pilots aren’t called on to fly life flights or odd-hour charter flights frequently enough to result in total exhaustion; however, when assigning crews, it’s a consideration the scheduler has to keep in mind.
The most difficult fatigue factor to plan around, I think, is aviation physiology – the element that becomes important when we start talking about weather and heavy traffic – those conditions which require hypervigilance or instrument flying. You’ve heard pilots say that their jobs are 99% boredom, 1% sheer terror. The problem is that the 1% of sheer terror doesn’t happen as a 30-second event. Flying through storms takes time – sometimes a long time. A friend told me of a study done in the 80s which found that one hour of flying in instrument conditions without autopilot equaled three hours of physical labor and five hours of mental stress. (If you have a copy of that study or a similar one, I’d love to see it.) Even with some percentage of error in the study, it stands to reason that hand-flying in instrument conditions is far more mentally taxing and more stressful than engaging auto-pilots in VFR conditions. Assigning crews for trips is typically done several days in advance and I don’t know anyone who thinks about the weather conditions for a trip on Monday when assigning crews for a trip on Tuesday, regardless of the itineraries or the length of the rest period.
Each of these elements presents risk. Any combination of them presents even great risks with the snowball effect. Trying to make a profit in a charter market that offers decreasing margins means that fewer people assume more responsibilities. It means that every penny is stretched into thin copper wire. It means that stress levels go up. In this environment, it is crucial that we pay closer attention to any of the industry variables that present risk. Rest time is one of the easiest variables in our industry to get right – and it’s one of the easiest to get wrong. Fatigue does not usually result in accidents or incidents; so, it’s one of the easiest to take for granted. However, it’s one we must closely control because the cost of being wrong is simply too high.