A Method for Smart Hydraulic Landing Gear Modeling and Simulation With Experimental Validation

Sensor and electronic control technology was applied to gas -hydraulic aircraft landing gear (oleo struts) to improve energy absorption capability. The strut stroking load was adjusted in proportion to sink rate just prior to ground contact. This provides added protection for the airframe in hard landings and moderate crashes. A full scale functional experimental strut similar to the landing gear strut for the UH-60A Black Hawk helicopter was used as a baseline for the study. The performance of the baseline strut was compared to struts modified with electronic control systems. Full scale drop tests were conducted at sink rates up to 42 feet per second. A numerical model was developed and used to compute the strut loads and strokes for a simulated vertical drop test. Comparison of computed results with experimental data shows that the analysis is valid for predicting the landing gear loads and strokes at different deceleration levels during impact. The work showed that protection can be enhanced in hard landings and crashes by including an electronic control system using sensor inputs to increase stroke efficiency and/or reduce maximum stroke. This may extend mission capability. Maximum payload can be increased for a given level of crash protection. Alternately, for a given payload, maximum gear stroke will be reduced in a severe hard landing. If that prevents fuselage-ground contact, the aircraft may be capable of continued operation.