|force per unit area|
|proportionality between applied force and resulting change in length of a given spring|
movable part of an airplane wing that is controlled by the pilot and permits him to roll the aircraft around its longitudinal axis. Ailerons are thus used primarily to bank the aircraft for turning. Ailerons have taken different forms through the years but are usually part of the wing's trailing edge, near the tip. Their efficiency in lateral control made obsolete the Wright brothers' system of wing warping.
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