Direct Measurement of Fluid Level, Gas Pressure, and Temperature for Autonomous Landing Gear Shock Strut Operational Readiness Evaluation

ABSTRACT: Aircraft oleo-pneumatic landing gear shock struts require a precise gas to fluid ratio. Measuring oil fluid level explicitly requires time consuming service and temporary aircraft inoperability. Current approaches to verify the operational readiness of landing gear shock struts forgo measuring oil fluid level directly, and instead compare x-dimension (shock strut extension) to gas pressure and/or aircraft gross weight, often leading to improperly serviced shock struts. Gas pressure is typically adjusted during inspections, which can adversely alter the gas to fluid ratio degrading a shock struts ability to absorb and dissipate impact forces that can result in airframe damage or personnel injuries. An automated method for directly measuring oil fluid level, gas pressure(s), and temperature would yield greater confidence of shock strut operational readiness, and vastly increase inspection efficiency and accuracy. To meet this critical need, Luna proposes to develop a non-obtrusive, ultra low-power, wireless system comprised of conformal solid-sate capacitive fluid level, pressure, and temperature sensors. The system will have the ability to wirelessly transmit in real-time, autonomously record data to embedded memory, and will require minimal retrofit implementation modifications. Finally, the system will be ruggedized to withstand the operating environment with considerations including temperature, vibration, de-icing, and environmental effects. BENEFIT: Successful implementation of the proposed technology will provide aerospace maintainers with an extremely helpful tool to verify the operational readiness of aircraft landing gear shock struts. In addition to the clear benefits of such a sensing system for maintaining, inspecting, and reducing safety risks to DoD aircraft and personnel, potential commercial application for this technology is broad. The proposed shock strut sensing system will benefit the commercial aircraft industry by greatly increasing inspection efficiency and accuracy and decreasing safety risks to aircraft, crew members, and passengers. Oleo-pneumatic shocks are used in numerous industries; they are used to support large industrial equipment, to decelerate railcars, and often incorporated in suspension systems, including automobiles and motorcycles, and therefore are other candidates for this technology. The shock strut sensing system can be used as a tool for evaluating maintenance intervals and performance of maintenance personnel. Additionally, the shock strut sensing system could provide a useful tool for shock design and testing.