11Aircraft Sizing, Engine Matching, and Variant Derivative

11.1 Overview

Chapter 6 proposes a methodology with worked-out examples to conceive a “firstcut” (i.e., preliminary) aircraft configuration, derived primarily from statistical information except for the fuselage, which is deterministic. A designer’s past experience is vital in making the preliminary configuration. Weight estimation is conducted in Chapter 8 for the proposed first-cut aircraft configuration, revising the MTOM taken from statistics. Chapter 9 establishes the aircraft drag (i.e., drag polar), and Chapter 10 develops engine performance. From these building blocks, finally, the aircraft size can be fine-tuned to a “satisfactory” (see Section 4.1) configuration offering a family of variant designs. None may be the optimum but together they offer the best fit to satisfy many customers (i.e., operators) and to encompass a wide range of payload-range requirements, resulting in increased sales and profitability.

The two classic important sizing parameters – wing-loading (W/S) and thrustloading (TSLS/W) are instrumental in the methodology for aircraft sizing and engine matching. This chapter presents a formal methodology to obtain the sized W/S and TSLS/W for a baseline aircraft. These two loadings alone provide sufficient information to conceive of aircraft configuration in a preferred size. Empennage size is governed by wing size and location on the fuselage. This study is possibly the most important aspect in the development of an aircraft, finalizing the external geometry for management review in order to obtain a go-ahead decision for the project.

Because the preliminary configuration is based on past experience and statistics, an iterative procedure ensues to fine-tune the aircraft for the correct size of the wing reference area for a family of variant aircraft designs and matched engines selected after discussion with engine manufacturers. Reference [1] provides an excellent presentation on the subject.

11.1.1 What Is to Be Learned?

This chapter covers the following topics:

Section 11.2: Introduction to the concept of aircraft sizing and engine matching

Section 11.3: Theoretical considerations

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