Electromechanical Actuator for Helicopter Landing Gears

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Electromechanical Actuator for Helicopter Landing Gears


application/pdf Electromechanical Actuator for Helicopter Landing Gears M. Rottach, T. Schneider
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Electromechanical Actuator for Helicopter Landing Gears


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Electromechanical Actuator for Helicopter Landing Gears M. Rottach (1), T. Schneider (2) 1 : Liebherr-Aerospace-Lindenberg GmbH, Pfänderstr. 50-52, 88161 Lindenberg, Germany, email: michael.rottach@liebherr.com 2 : Liebherr-Aerospace-Lindenberg GmbH, email: tom.schneider@liebherr.com Abstract Electromechanical actuators are used increasingly in aerospace applications in order to increase efficiency and to reduce environmental impact and operating costs of air transport. This paper presents a linear electromechanical actuator (EMA) for helicopter landing gear extension and retraction systems. The actuator developed at Liebherr-Aerospace-Lindenberg can be used to extend and retract a helicopter landing gear and provides emergency functions for landing gear extension without external power sources. In order to comply with the efficiency targets and to decrease the overall weight of the actuator, a highly optimised direct drive high efficiency ball-screw arrangement is combined with integrated electrical motor and power electronics. A prototype of the actuator is under construction and test results will be presented at the conference. Introduction Energy efficiency and the reduction of emissions are important design and technology drivers within the aerospace industry. Ever increasing environmental awareness and increasing air transport require clean and green technologies which at the same time reduce the operating costs of the aircraft. Electromechanical actuators are seen as a promising technology towards achieving these goals ([1], [2]). Electromechanical actuation of landing gears offers deletion of hydraulic systems and piping and can help reducing the aircraft weight while increasing its efficiency. Research activities concerning electromechanical landing gear actuators for commercial aircraft have been presented in literature. In [3] a study of a linear landing gear EMA for a large passenger aircraft is presented and the benefits of EMAs in terms of reduced maintenance and increased dispatch reliability is highlighted. Doberstein [4] presents an optimisation methodology for EMA systems and applies it to a landing gear actuator, showing the impact of kinematics variation on component and system sizing. A linear EMA for landing gear actuation is presented by Chevalier [5], showing the EMA as a viable alternative to Hydraulic and Electro Hydrostatic Actuators (EHA). This paper focuses on the development of an EMA for a helicopter landing gear. High efficiency and minimum weight with maximum availability are the major design drivers. The design concept of the fault- tolerant EMA will be presented at the conference and test results from a prototype EMA will be shown. Landing Gear EMA The main function of the landing gear EMA is the controlled extension and retraction of the landing gear. Additionally, an emergency extension mode of operation allows for the extension of the landing gear in absence of electrical power at the actuator. Furthermore, the EMA locks the landing gear in extended and retracted position to allow for a safe operation of the aircraft. The landing gear actuation scheme is shown in Fig. 1. Fig. 1: Landing gear actuation scheme The landing gear linear EMA design features a high efficiency ball-screw and a brushless DC (BLDC) motor in a direct drive arrangement. This arrangement optimises the reliability and availability of the EMA by minimising component count of the system. Furthermore it realises a low inertia design for optimised back driveability. In case of failures of the electrical supply system or the electrical drive train of the actuator, a free-fall operation mode is required of the actuator. With an emergency release device a free rotation of the roller screw nut is achieved and the landing gear extends by gravity. For integrity reasons the status of the emergency release device is monitored by sensors to avoid undetected unintentional activation. The full landing gear EMA will be presented at the conference alongside with details of the application as well as the achieved performance of the demonstrator EMA. Conclusions Electromechanical actuators for helicopter landing gear extension and retraction offer system level benefits in terms of weight, operating costs and efficiency. An EMA for a helicopter landing gear application has been presented and its main features and design drivers have been highlighted. At the conference the test results with a demonstrator prototype will be presented References [1] D. P. Rubertus, L. D. Hunter, G. J. Cecere; "Electromechanical Actuation Technology for the All-Electric Aircraft"; IEEE Transactions on Aerospace and Electronic Systems, vol. AES- 20, pp. 243-249, 1984 [2] P. W. Wheeler, "The More Electric Aircraft: Why Aerospace Needs Power-Electronics?"; EPE '09, Barcelona, 2009 [3] W. Li, J.P. Fielding; “Preliminary Study of EMA Landing Gear Actuation”; ICAS 2012, Brisbane, 2012 [4] D. Doberstein, F. Thielecke; “Model Based Design Method for Electro-Mechanic Actuator Systems, Applied to a Nose Landing Gear”; R3ASC’12, Toulouse, 2012 [5] P. Chevalier, S. Grac, P. Liegeois; “More Electrical Landing Gear Actuation Systems”; R3ASC’10, Toulouse, 2010.