Over-speed limiter schemes for Full Authority Digital Engine Control System

Engine control system of aircraft is used for controlling the engine parameters. In today´s world Full Authority Digital Engine Control System (FADECS) is used for controlling engine of aircrafts. FADEC system broadly consists of the hydro-mechanical systems, sensors, harnesses, dedicated electronics and embedded software for controlling the engine parameters. FADEC system controls various engine parameters as per the control laws embedded into it. The main spool of the engine is a very critical component on which various hydro-mechanical systems (viz. First Stage Pump, Main Engine Fuel Control Unit, Reheat Fuel Control Pump etc) and electrical system (Generators, Alternators etc) are mechanically coupled. For smooth functioning of engine, it is highly desirable to provide a reliable speed regulation and over-speed protection mechanism for main spool of the engine. In no circumstance engine speed should go beyond a certain specified limit. Various over-speed limiters schemes for main spool of engine have been identified to limit the speed of main spool during various failure modes which can lead to over-speeding of spool. For these schemes the paper also brings out the required hardware and software architecture.