Choice and Sizing of Engines for Aircraft

Abstract

AbstractThe key issues involved in the choice of engine for aircraft projects are discussed. Although the focus is mainly on subsonic transport aircraft, a few comments are included regarding supersonic military aircraft.The most important issues affecting engine choice and sizing are the number of engines per aircraft and the aircraft mission – its range, speed, maximum operating altitude, take‐off field length, payload, and consequent all‐up weight. Aircraft, and their missions, vary greatly, from small helicopters to large long‐range airliners. Safety is paramount in all cases.Important engine characteristics include the engine thrust, the type of engine, the engine fuel consumption, and its weight, diameter, life, and initial and maintenance costs. Other factors include the operating environment, the air and power off‐takes for aircraft services, stealth, customer perception, and maintenance arrangements.Engine fuel consumption per unit of thrust is shown to be of high importance to subsonic transport aircraft design because the weight of fuel consumed is often a significant fraction of the aircraft take‐off weight. This and the engine weight affect the aircraft design and therefore its drag; this in turn affects aircraft thrust requirements and therefore engine size. Choice of turbofan design parameters such as bypass ratio, are discussed.