Survival in hostile environments: The fight to understand and protect against acceleration-induced visual disturbance and loss of consciousness in pilots of powered, heavier-than-air aircraft

In the two decades that followed the first sustained, controlled flights of the Wright Flyer at Kitty Hawk on 17 December 1903, the design of powered, heavier- than-air aircraft advanced rapidly. The development of increasingly powerful engines allowed pilots to fly higher and faster, and begin to perform aerobatic manoeuvres. However, rolls, steep turns, and pullouts from dives exposed aviators to accelerative forces equivalent to many times the force of gravity. Reported effects included the sensation of 'being forced into the seat', heaviness of the legs, and occasionally, on pushing 'the rotatory stimuli up to unusual limits', narrowing of the visual field, and 'darkening of the sky'.