Abstract: The load on an aircraft component, such as the load on or in a landing gear leg during braking, is measured with an all-weather displacement measuring system. The system includes a processing unit, a controllable source of laser light and a light detector comprising a plurality of sensors. When the aircraft component is subjected to a load, relative movement of the source and detector is caused. The source and detector are housed in an inert and dry atmosphere sealed in a container and are therefore protected from the external environment. The detector generates in response to light received from the focused beam of light emitted by the source a signal that is received by a signal processor of the control unit. The signal received by the control unit depends on the relative positions of the source and detector. The control unit is arranged to provide an output signal representative of the load sustained by the aircraft component.

Abstract: An aircraft control system operates during landing to suppress normal modes of flexing of the aircraft or modes of rigid rotation. The excitation of the modes are measured using accelerometers attached to the aircraft or strain-measuring devices attached to the landing gears. To suppress the modes, the controller operates the flight control surfaces, e.g., elevators, ailerons, rudders and spoilers and/or the steering angle of the nose wheel. This reduces vibration, which reduces wear and makes braking more even because the variation in load on the ground wheels caused by the excitation of the modes is reduced.