OVERVIEW

A new impetus was given to aviation by the relatively enormous power for weight of the atomic engine; it was at last possible to add Redmaynes's ingenious helicopter ascent and descent engine to the vertical propeller that had hitherto been the sole driving force of the aeroplane without over-weighting the machine

H.G. Wells, in The World Set Free, 1914

In this chapter we will look at the engine/airframe as a single system. When an engine is mounted on the airframe, it becomes an integral part of the aircraft. The performance parameters considered are the thrust, power, specific fuel consumption, fuel flow, and the free parameters needed to evaluate them (flight speed, altitude and throttle position). Additional parameters are involved in propeller propulsion. These are the propeller's geometric configuration and its rotational speed. For variable throttle settings, the engine response will be considered instantaneous. Therefore, there will be no time lag between throttle and power or thrust.

We will not provide details on how a gas turbine or a reciprocating engine functions. For reference, some data on jet engine cycles are provided in Table A.3. Data and performance on aero-engines are published regularly by Jane's Information Systems ^[154]. Chart performance, if not already available in the open literature, is almost impossible to obtain from the manufacturers unless you buy an engine from them. Some basic concepts will be reviewed in this chapter, with the scope of providing means of calculating some propeller and helicopter performance.

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