Sleep and Fatigue — Page 225, Lesson 360

Alright, let's talk about hypovigilance. This is a critical concept for us as pilots, because it's a state that directly threatens our ability to fly safely. Hypovigilance is a condition where your sleep patterns start to show up on an EEG—that's an electroencephalogram, a machine that measures your brain's electrical activity—while you are supposed to be awake and performing a task. In plain language, your brain begins to drift into sleep mode even though your eyes are open and you're on duty. It is very similar to a microsleep, which is a brief, involuntary episode of sleep that can last from a fraction of a second up to several seconds. Now, what triggers this? The excerpt lists several conditions that are almost tailor-made for the flight deck. It can occur during periods of monotony, a reduction of workload, or during simple or repetitive tasks—think of a long cruise at altitude with the autopilot engaged. It's also brought on by constant and monotonous noise (like the steady drone of the engines), low lighting, high temperature, isolation, sleep debit (which is the cumulative lack of sufficient sleep), and fatigue. It can also occur shortly after a meal, as your body directs energy toward digestion. So, how do we deal with this in flight? The first thing to understand is that it is not possible to totally eliminate hypovigilance during flight. In fact, there's a theory that it helps control energy consumption—your brain essentially tries to conserve energy when it perceives the environment as non-threatening. However, it is prudent to forestall this phenomenon as far as possible. We need to take active precautions. Here are the key precautions you should take: First, ensure you have sufficient sleep credit before the flight. This is your foundation. Second, be aware of the physical danger signs in yourself and your crew. These include: - Drowsiness, your head dropping forward, and a vague but persistent sensation of discomfort that makes you constantly shift your sitting position. - Slower sensory perception—for example, having to look at an instrument for a longer time than normal before you can digest its information. - Preoccupation with a problem completely outside of the current situation—your mind wanders off to something unrelated to flying. - Moodiness and a reluctance to talk. Third, take active countermeasures: - Move your position regularly every so often. If possible, get up and walk a few steps in the aircraft. - Maintain social contact with the rest of the crew. Talk to each other. - Remember that vigilance decreases with lack of stimuli, so keep mentally and physically active. Challenge yourself with a mental exercise, scan your instruments actively, or discuss the next phase of flight. - Members of the crew should take their meals at different times. This is a double-edged precaution. First, it helps ensure that if hypovigilance is going to be a problem among the crew, its occurrence will probably be staggered—not everyone will be affected at the same time. Second, as we've already discussed, this also avoids food poisoning striking more than one crew member at a time. Finally, the excerpt closes with a general principle: there is no absolute amount of sleep that must be achieved. You should sleep as much as you need. The key word is need—it's individual, and you must know your own requirements to maintain safe performance.