In a shock strut for an aircraft landing gear having inner and outer elongated telescoping tubes and a primary orifice selected and designed to attenuate the load level to a certain design condition which is compatible with the aircraft's structural threshold up to a certain overload sink speed, a load attenuating valve which opens when the design velocity is exceeded. The load attenuating valve includes secondary orifices held closed by a tension fuse which ruptures and opens the orifices in parallel to the primary orifice for additional flow, thus keeping the pressure drop across the orifices to an acceptable level so as to permit full stroking of the strut. In this way, as much energy as possible is absorbed before the load is transmitted to the aircraft on failure.
A shock absorber is disclosed having an outer cylinder closed at one end thereof, a hollow inner cylinder closed at one end and opened at an another end thereof, the open end being inserted in the outer cylinder, a guide member for guiding the inner cylinder slidably in the outer cylinder, a member for generating a damping force, the damping force generating member being connected to the open end of the inner cylinder, and having an orifice for throttling flow of hydraulic fluid from a chamber in the outer cylinder to a chamber in the inner cylinder, the orifice being in a central portion of the inner cylinder, and a plate-like stop provided between the inner cylinder and the damping force generating member for retaining the damping force generating member against the damping force within a predetermined range, the stop having an aperture greater than the orifice.
The invention relates to a force-limiting device for aircraft landing gear shock absorbers, in particular for helicopters, and also to a shock absorber fitted with such a device. According to the invention, a box 201 is provided that forms a partition in the main body 101 of the shock absorber, the box having a bottom 202 whose central portion has a diaphragm 210 with small throttling orifices 211 and force-limiting members also being provided comprising firstly an annular valve member 225 disposed around the diaphragm 210 such that when open it allows a large volume of hydraulic fluid to pass through the box in a very short time, and a resilient return member 226 holding the annular valve member 225 in its closed position, but allowing the valve member to open above a predetermined threshold.
