Method and apparatus for sensing preload in a tilt rotor downstop

Abstract

A improved tilt rotor aircraft comprising an airframe, at least one wing member coupled to the airframe, and at least one tilt rotor assembly carried by the at least one wing member. The tilt rotor assembly is actuated by a conversion actuator. The improved tilt rotor aircraft includes a low-height tunable downstop assembly for absorbing oscillatory vibration loads, such as pitch loads and yaw loads. The low-height tunable downstop assembly comprises a pivotable striker assembly having an adjustable stiffness, and a cradle assembly adapted to releasably receive the striker assembly. The striker assembly is attached to the tilt rotor assembly and the cradle assembly is attached to the wing member. A plurality of sensor modules are bonded to the cradle assembly. The sensor modules include a plurality of strain gages arranged to sense shear strain in the cradle assembly. The sensor modules are electrically coupled to sensor circuits and flight control computers. As the conversion actuator pivots the tilt rotor assembly into the airplane mode, the conversion actuator forces the striker assembly into contact with the cradle assembly at a selected preload. The sensor modules directly sense preload induced strain in the cradle assembly and send corresponding signals to the flight control computers via the sensor circuits. If the signals from the sensor modules indicate that the preload is insufficient to maintain stability in the aircraft mode, then a warning signal is sent to the pilot and a control signal is sent to the conversion actuator to increase the preload. Likewise, if the signals from the sensor modules indicate that the preload is too high, a warning signal is sent to the pilot and a control signal is sent to the conversion actuator to decrease the preload.