More Electric Landing Gear Actuation Study

Abstract

This report addresses the problem of landing gear actuation system design on more-electric aircraft (MEA). Firstly, information about more-electric aircraft and more-electric actuators was gathered and sorted. Current more-electric landing actuation system applications and researches were also summarized. Then several possible more-electric landing gear actuation concepts were identified. To evaluate these concepts, the case study method has been used. A concept aircraft “MRT7-T”, which has similar maximum takeoff weight to that of Boeing 787, has been chosen as the design case. Systems of different configurations and architectures were designed for this aircraft. In the end of this study, a comparison between different more-electric landing gear actuation systems, and also with traditional central hydraulic system was made. The best concept was proposed. More-electric actuation technology has made considerable progress in the last two decades. However, most of the applications and researches have focused on flight control actuation and brakes. Using more-electric drives for landing gear actuation has been well known to be difficult, for the reason of massive power needs and difficulties in achieving redundancy levels. Famous more-electric research projects like POA and Power-By-Wire only gave recommendation of using electro-hydrostatic actuators (EHA) in landing gear actuation. And no further information is available to the public. In this study, DHS (distributed hydraulic system), EHA (electro-hydrostatic actuator) and EMA (electro-mechanical actuator) were identified as candidate solutions. Design requirements such as retraction time, load and redundancy levels were derived through analysis. As a unique feature, landing gear kinematics concepts were also subject to optimization. Various kinematics concepts were proposed and analyzed in detail, to provide favorable loading and geometrical conditions for the systems. Kinematics design guidelines were built through discussion. Different motors such as AC induction motor, BDCM (brushless DC motor) and PMSM (permanent magnetic synchronous motor) were evaluated for use. Different system architectures were also explored. The multi-discipline optimization method has been extensively used in the design process of the systems. Firstly, each node of the actuation systems was optimized. Then optimizations were made to the systems. Performances of each system were analyzed in several aspects such as weight, power, reliability and maintenance. Comparison of different systems was made through scoring method. The results suggested that DHS, EHA and EMA are all applicable for landing gear actuation. And isolated EHA is the best.