The engine may be considered the heart of any powered-aircraft system. This book is not concerned with engine design, but it covers the information needed by air­craft designers to find a matched engine, install it on an aircraft, and evaluate its performance. The chapter begins with an introduction to the evolution of an engine followed by the classification of engine types available and their domain of applica­tion. This chapter primarily discusses gas turbines (both jet – and propeller-driven) and – to a lesser extent – piston engines, which are used only in smaller general – aviation aircraft. Therefore, a discussion of propeller performance is also included in the chapter. The derivation of thrust equations precedes propeller theory.

It is difficult to obtain industry-standard engine-performance data for course- work because the information is proprietary. The performance of some types of engines in nondimensional form is described in Section 10.11. Readers must be care­ful when applying engine data – an error could degrade or upgrade the aircraft per­formance and corrupt the design. Verification and substantiation of aircraft design are accomplished through performance flight tests. It is difficult to locate the source of any discrepancy between predicted and tested performance, whether the discrep­ancy stems from the aircraft, the engine, or both. The author suggests that appropri­ate engine data may be obtained beyond what is provided in the scope of this book. As mentioned previously, the U. S. contribution to aeronautics is indispensable and its data are generated using the FPS system. Much of the data and worked-out exam­ples in this book are in the FPS system. An extensive list of conversion factors is in Appendix A.

10.1.1 What Is to Be Learned?

This chapter covers the following topics:

Section 10.2: Background on and classification of aircraft engines

Section 10.3: Definitions

Section 10.4: Introduction to air-breathing aircraft engine types

Section 10.5: Engine cycles

Section 10.6: Theories involved in engine-performance analysis

Figure 10.1. Modular concept of gas turbine design

Considerations for engine installation Intake and nozzle design Nozzle and thrust reversers Propeller

Engine-performance data

10.1.2 Coursework Content

This chapter creates engine-performance graphs that are used in Chapter 11 for aircraft-performance analysis. In this chapter, readers generate thrust and fuel-flow levels for matched engines at various power settings, speeds, and altitudes, all in a standard atmosphere.