A Design Solution for a Crashworthy Landing Gear with a New Triggering Mechanism for the Plastic Collapse of Metallic Tubes

The paper presents the basic guidelines for the design of a landing gear adopting a crash tube as an energy absorbing device in crash conditions. In the considered landing gear lay-out, a light alloy thin walled tube is mounted coaxially to the shock absorber cylinder and, in severe impact condition, collapses in order to enhance the energy absorption performance of the landing system. A novel triggering mechanism, activated in crash impact conditions, has been developed in order to eliminate the initial load peak in the tube collapse process. The device allows to study the possible design solutions for an additional shock absorbing stage that can be integrated in a landing gear structure without requiring the introduction of frangible attachments. The characteristics of the triggering device are presented and the structural lay-out of a crashworthy landing gear adopting the developed additional energy absorbing stage is outlined. Experimental and numerical results relevant to the triggering system development are reported. The potential performances of a landing gear featured with the additional stage are analysed by means of a simplified numerical model, showing that appreciable energy absorbing capabilities and efficiencies can be obtained in crash conditions.