1 Summary In this essay I describe some ways you can harm yourself without meaning to, and show you some clues by which you can judge when to compensate. First, the vestibular system (inner ear) is designed to detect change in our body's position. On the other hand, we pilots are more interested in our glider's current orientation or state with respect to airflow. I'll show you several reasons why "keeping your head on a swivel" protects you from illusions that can mess up your control coordination and wreck your ship. The vestibular system works well, but is imprecise and is prone to certain predictable errors. Understanding the conditions in which these errors are most likely can help you avoid them. Second, pilot physical impairment is usually subtle and insidious, and may be difficult to notice. Most important are - fear or doubt - fatigue - dehydration - hypoxia - illness or disease1 ----------- 1. I like to distinguish "disease" from "illness" by considering a "disease" to be a condition that requires treatment, but may be completely stable and not at all bothersome with treatment; many diseases do not create any risk of decreased pilot performance. I consider "illness" to be something that does at least make you miserable and in other ways may physically impair performance. It's often safe to fly with a disease; it's seldom safe to fly despite illness, in this sense. Fear can completely destroy judgment and freeze rational analysis. The best antidote to fear is thorough training. Studies have shown that the pilot who has mentally rehearsed formal emergency procedures will effectively do them under stress; the pilot who is unprepared will be unable to formulate a cogent emergency plan at the instant of an emergency. Doubt is lack of confidence which may make it impossible in a moment of stress for a pilot to objectively evaluate which of several courses of action is the best. I'll not spend any time reviewing the extensive work on the psychology of emergency decision-making, and instead focus on the inner ear and the effects of fatigue, hypoxia, and dehydration on performance. 1.1 Performance Of the many factors affecting competence, I'll comment only on biological ones. When the Lord God made Man a living spirit, He created psychological, ethical, social, and spiritual factors; but we will assume that you and your mom pretty much worked the basics out several years ago, and you have become a competent, effective human being and later training made you a pilot. Some of the biological factors of competence are: - fatigue, - hydration status, - oxygenation, - nutritional status, - core temperature, - emission-control plan, - cardiovascular conditioning & stress response, - and others. 1.2 Fatigue Rest, as you already know, takes several forms. You may come home from your sedentary job exhausted and rest by going for a long run. Physical and mental effort seem to produce separate types of exhaustion. Each person has a different capacity for mental or physical work, which varies over time depending on many factors. The most pervasive and subtle collection of factors is called "jet lag," which amounts to disturbed biorhythms. 1.3 Jet lag Ideally, one should arise at the same time every day, and go to bed within about 30 minutes before and up to 1 hour after a given time (depending on your need for sleep), in order to entrain biorhythms most effectively. Changing your sleep cycle will shatter your biorhythms promptly.2 If you stay up most of one night, you will be ----------- 2. Precisely, the body can adjust easily to advancing bedtime by three hours per day; but it can easily adjust to going to bed earlier by only one hour per day. sleepy the next (second) day, but on the following (third) day you will lack mental and physical resilience and feel "tired" (but not sleepy), even if you sleep on your normal schedule between the second and third day. This third-day fatigue is "jet lag," and is likely to occur during any trip if the sleeping conditions are unfavorable to satisfying rest. Chronic "jet lag" does seem to affect longevity: About 40 years ago I read a newspaper report stating that Northwest Airlines had studied its pilots, and found that the life expectancy of their trans-pacific pilots was a few years shorter than that of pilots flying only domestic routes. And a study about 15 years ago of physicians showed that those specialists such as ophthalmologists and pathologists, with no night call, lived on the average into their 80's, while those whose specialties required night call, such as general or family practice or internal medicine, died about 10 years younger. With travel involving any significant shift of time zones, adaptation of your biorhythms requires several days, as you've noticed. Traveling west is easier than traveling east: research has demonstrated that we can cope well with a delay in bedtime, and time of arising, of up to three hours; but to "back up" only half an hour presents a similar difficulty to our systems. So our bodies adjust most smoothly if we (in traveling west) go to bed and get up three hours later each day, and if in traveling east we go to bed and get up 1/2 hour earlier each day. Ironically, this means that if we travel more than 4 time zones east, it's actually easier to adapt by going to bed three hours later each day. Actually to follow such a schedule rigidly is usually impossible while traveling, but understanding this principle and approximately following it can make it easier for you to adapt during and after your next trans-continental trip. The important lesson for the pilot is that if you are able to continue "living in your home time zone" during a trip by arising at the usual zulu time daily, you will have less mental fatigue and avoid the performance degradation that comes with jet lag. Regarding the nature of mental fatigue, little is known physiologically due to the unseemly reluctance of people to let biologists put fine metal probes into the depths of their brains. Despite this general lack of commitment to scientific progress, everyone except young children in need of a nap and college students understand that mental fatigue impairs intellectual performance. And piloting a glider is obviously an intellectual performance, if only because so little gross physical activity can take place in such a small cockpit. If you feel tired, you are tired: expect sub-par intellectual agility, slowed perception, and awkward judgment--and rigidly stick to the basics.