Digital Control Brings Large Turbofan Benefits to the Regional Jetliner Turbofan Market

Abstract

In keeping with the general industry trend of applying Full Authority Digital Electronic Control (FADEC) technology to small gas turbine engines, Textron Lycoming and Chandler Evans Division of Coltec Industries have developed and qualified a single channel control system for use on the Textron Lycoming LF507-1F turbofan engine. The LF507-1F is the world’s smallest FADEC-equipped airline turbofan engine and is the only FADEC-equipped turbofan developed and certified for the regional jetliner market. The application for this powerplant, the four-engine AVRO International Aerospace RJ Avroliner series of aircraft, began airline service in April of 1993. The FADEC employs modern control algorithms to achieve surge-free operation over the flight envelope while providing rapid transient performance and crisp handling qualities. The control interfaces with the aircraft via an ARINC 429 data link to control each engine automatically to the desired power setting with or without N1 synchronization. A simple hydromechanical backup control provides full dispatch capability in the event of a critical FADEC system failure. In addition, the FADEC includes advanced diagnostics for fault identification to the line replaceable unit (LRU) level without specialized test equipment. This paper describes the architecture, primary features, and development process of the engine control system. Emphasis is placed on the design characteristics and technical challenges unique to the development of an inexpensive control system for the low thrust turbofan market.