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Alarmed at a high incidence of crashes during routine flight training in the 1940s, U.S. Air Force officials looked for evidence of mechanical flaws in the planes or human error perhaps inadvertently introduced by their curriculum, but the cause of the crashes remained mysterious. At last, officials commissioned a lieutenant trained as a scientist, Gilbert Daniels, to look at the physical structures of the cockpit and the men who used them. Daniels noted that all the cockpit structures—seat and back, pedals, knobs, and so on—had been built to specifications calculated for an average military recruit. Recruits for pilot training were already selected for some degree of averageness, had been the reasoning, so these dimensions should fit most pilots, most of the time. But when Daniels measured 4,063 soldiers, he was astonished to find that not a single one of the men fit all ten of the measurements that had been determined to be average. Instead, every body offered its own variation: One pilot might have a longer-than-average arm length, but a shorter-than-average leg length. Another pilot might have a big chest but small hips. Even more astonishing, Daniels discovered that if you picked just three of the ten dimensions of size—say, neck circumference, thigh circumference, and wrist circumference—less than 3.5 percent of pilots would be average sized on all three dimensions. Daniels’s findings were clear and incontrovertible. There was no such thing as an average pilot. The unyielding fixity of the average cockpit ended up being useful to exactly no one. Thereafter, aeronautical engineers began to make everything from seats and foot pedals to flight suits and helmet straps adjustable, and the Air Force adjusted its cockpit specifications to stipulate movable parts that could be adapted to fit a range of body measurements, from 5 to 95 percent of average, just right.
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