Page 10 - July21T

Naps and caffeine are to fatigue what aspirin is to a headache – you have not cured the underlying illness; you have only reduced the symptoms. The only cure for fatigue is sleep.
There are three types of fatigue: transient, cumulative and circadian. Transient fatigue is brought on by a night of insufficient sleep (it also oc- curs after being awake for an excessive period of time). Cumulative fatigue occurs when insufficient sleep occurs multiple nights in a row. Circadian fa- tigue is also known as jet lag. It occurs when the quality of sleep is disrupted by rapidly changing sleep cycles.
Transient fatigue is easily resolved: get extra sleep. The average person requires around eight hours per night (the exact number is inversely related to age). Six hours of sleep will produce two hours of sleep deficit. If you sleep 10 hours the next night, you will be properly rested. If you get six hours of sleep five nights in a row (cumulative fatigue), your sleep deficit is 10 hours. You obviously cannot catch up on this
in one night. Two (or more) nights of excess sleep may be required to fully eliminate cumulative fatigue.
Circadian fatigue is a bit more com- plex. The human body is optimized for regular sleep cycles. A normal person (who is awake during the day) expe- riences maximum sleepiness from 0200-0600 (which is also the most ef- fective time to be asleep). Conversely, the greatest alertness occurs between 0900-1100 (the least effective time to sleep). The body will (to some degree) adapt to different sleep cycles, but in general, it is only capable of adjust- ing by around an hour per day. If you change your wakeup call from 0900 to 0500, your body requires four days to produce fully restorative sleep on the new schedule.
It is little surprise to find fatigue related accidents are the bane of cargo operators. It is an industry that often operates on the backside of the geo- graphical clock. The NTSB is quick to reference “insufficient management of off-duty sleep” in accident reports. The view of the NTSB is that pilots are responsible for maintaining a sleep pattern that will facilitate their next duty cycle, regardless of how this im- pacts off-duty time. This can produce difficult dynamics at home as fami- lies inevitably live on diurnal sched- ules (awake during the day, asleep at night). Given the extended period of time required to adapt to new sleep cycles, a pilot at home for a few days has little hope of fully adapting from family activities to the routine of the graveyard shift.
Fatigue is not the isolated province of check haulers. Passenger red-eyes are routine for eastbound flights. Like- wise, mid-sequence schedule changes represent a ubiquitous theme in all forms of flying. Aviation is often more about optimizing operational needs than dodging fatigue. A 6 a.m. depar- ture on Tuesday followed by a 10 p.m. touchdown on Thursday will inevi- tably involve some degree of fatigue.
Many sleeping aides are approved for pilots (primarily when used to adapt to different sleep cycles. If used to treat an underlying sleep disorder, a special issuance medical
is required). Yet most medications require the time between the last dose and flight duty to exceed “five times the half-life” of the drug (the recom- mended time interval between doses generally equates to the half-life. An antihistamine with instructions to “take every 12 hours,” for example, would require 60 hours between use and flight). Dietary supplements of- fer more flexibility, though they are not without controversy. Melatonin and tryptophan are two substances found naturally in food that are also produced as sleep aids (both as OTC and as food supplements).
The FAA lists melatonin as “gen- erally safe to fly” (the FAA does not actually approve any drug for use by pilots; it only lists some – such as as- pirin – as “generally safe to fly”). Stud- ies have demonstrated that melatonin facilitates a more rapid adjustment to a new sleep cycle when used prop- erly (taken immediately before going to bed). It represents an imperfect solution, but it may be an effective method to counter circadian fatigue for individuals who require a rapid shift from one sleep cycle to another. Note that some countries and certain military branches require flyers to observe a specified interval between the last dose of melatonin and operat- ing a flight.
Fatigue is the indisputable cham- pion. Neither skill nor experience pro- vides an effective countermeasure to the debilitating effects of tiredness. The only way to overcome fatigue is to throw in the towel and find a bed. Resignation is the path to victory in this case. Fatigue diminishes every advantage that an aviator has: mental alertness, experience, training and ingenuity. It is an exam that you can only pass by sleeping through it.
Stan Dunn is an airline captain and check airman. He has 7,000 hours in turbine powered aircraft, with type rat- ings in the BE-1900, EMB-120, EMB- 145, ERJ-170, and ERJ-190. Stan has been a professional pilot for 14 years, and has been flying for two decades. You can contact Stan at tdunns@ hotmail.com.
8 • TWIN & TURBINE / July 2021