Duty cycle analysis for aircraft control surface actuation
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PBW actuation methods, particularly Electro-Mechanical Actuators (EMA) and Electro-Hyrdrostatic Actuators (EHA), are reviewed and compared to the conventional hydraulically based actuation methods which have dominated aircraft primary control surface actuator procurements since the 1950's. Primary surface actuation requirements, which are typically based on conventional hydraulic actuation methods, are reviewed and explained with particular emphasis being placed on the effects that aerodynamic phenomena and industry trends have on these requirements. Notable PBW prototype testing programs have revealed that PBW actuators can benefit significantly from a duty cycle based requirements specification. Two particularly areas of concern, which have been noted in literature, include PBW actuator thermal performance and durability, both of which are directly influenced by the duty cycle. A particularly demanding aircraft duty cycle is presented in Chapter 4, along with 5 basic analysis techniques which can be used both in the development of new design requirements and in the support of subsequent analyses specific to an area of particular interest. Both a thermal and durability analysis were conducted yielding results which a prospective designer could use directly to support design decisions to improve the thermal and durability performance of PBW actuators. Based on the availability of duty cycle data (when hardware provisions are made to collect and record it) an actuator intelligence and decision making scheme is proposed. The decision making scheme (which would operate directly off of duty cycle based criteria) has the potential to offer significant maintenance and reliability benefits to PBW actuators, while simultaneously allowing the pilot/engineer/operator to more effectively monitor and control the aircraft. The implementation of these analysis techniques and intelligence measures thereby facilitates the transition of PBW to common use in primary surface control and advances the cause of the moreelectric aircraft.