Landing gear systems for vertical takeoff and landing (VTOL) aircraft, which include rotary-wing aircraft (e.g., helicopters), may be non-retractable or retractable. Some VTOL aircraft have a nose landing gear while others have a tail landing gear, and still others have both. The landing gear components for a VTOL aircraft are generally similar to those components used in a fixed-wing aircraft landing gear system. The main landing gear system generally supports the VTOL aircraft on the ground and cushions it from shock during landing. The main landing gear system typically includes a shock strut, torque arm, which may also take the form of a drag beam or side beam depending on a retraction direction of the landing gear, an axle or spindle, one or more wheels or tires, a braking system and a weight-on-wheels system, which may take the form of a weight-on-wheels sensing switch.
The weight-on-wheels switch provides ground or flight status indications for various systems of the VTOL aircraft and for a variety of maneuvers. By way of example, the weight-on-wheels switch provides an indication as to whether the aircraft is touching the ground or airborne. When the aircraft is on the ground, the switch is compressed in relationship to a small stroke of the shock absorber, which results from at least an incremental amount of the aircraft weight being transferred to the ground. Typically, only a small amount of the aircraft's weight is required to achieve the small stroke of the shock absorber, where the stroke distance is generally about 0.25 to about 0.50 inches. Next, an on-board computer system of the VTOL aircraft receives an indication that the aircraft is at least touching the ground.
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