GB618914A - Improvements in and relating to undercarriages for aircraft, especially helicopters - Google Patents

Abstract

618,914. Launching aircraft. CIERVA AUTOGIRO CO., Ltd., PULLIN, C. G., and WATSON, K. Nov. 12, 1946, No. 33581., [Class 4] An aircraft undercarriage, especially for helicopters, comprises a landing wheel associated with two independent shock-absorbing mechanisms operative in series, one being capable of dissipating the energy of an emergency landing without imposing a deceleration exceeding 3g and the other being capable of dissipating the energy of normal landings and taxying shocks. The landing wheel 18 is carried in a fork 17 secured to the plunger 16 which together with the cylinder 15 forms a resilient shock-damping buffer capable of dissipating normal landing shocks. Vertical movement of the plunger 16 in the cylinder 15 takes place in the plane of rotation of the wheel 18 and thus gives rise to no scrubbing action on the tyre. When a certain critical loading is exceeded, the cooperating faces 48, 49 ensure that the wheel 18 turns into the plane containing the arm 9 of the emergency landing system. The arm 9 is pivoted at 8 to the aircraft and is provided with a hydraulic buffer 11 to control its pivoting action. The buffer 11, Fig. 2, comprises a cylinder 19 which houses a plunger 20 having an internal bore 21 and a restricted orifice 22 at the lower end. The return of the oil in the cylinder 19 to the reservoir 26 via pipes 23, 25 is controlled by a spring-loaded valve 32, the setting of which determines the critical loading under which the emergency landing system 9, 11 begins to collapse. A hand-operated lever 35 enables the buffer 11 to be collapsed at will when the aircraft is on the ground. To enable the emergency landing system to be fully extended again when the aircraft is airborne, a pump 28 is provided to pump the fluid back into the cylinder 19, a non-return valve 29 being provided in the delivery pipe 24 to prevent back-flow of fluid from the buffer 11 to the reservoir when the buffer is under load and the pump not working. An overload relief valve 31 is provided and means may be provided to hold this valve open when the landing system is under load and thus prevent the pump tending to jack the aircraft up whenever the pump is running. Other arrangements for providing an emergency landing system are also described.