Configuring Aircraft

6.1 Overview

The coursework now starts with this chapter. It follows the mock market study in Chapter 2, which generated customer-specified aircraft requirements. Civil and mil­itary aircraft configuration layouts are addressed separately because of the funda­mental differences in their approach, especially in the layout of the fuselage. A civil aircraft has “hollow” fuselages to carry passengers. Conversely, a combat-aircraft fuselage is densely packed with fixed equipments and crew members.

Industry uses its considerable experience and imagination to propose several candidate configurations that would satisfy customer (i. e., operator) requirements and be superior to existing designs. Finally, a design is chosen (in consultation with the operators) that would ensure the best sale. In the coursework, after a quick review of possible configurations with the instructor’s guidance, it is suggested that only one design be selected for classwork that would be promising in facing market competition. This chapter describes how an aircraft is conceived, first to a prelimi­nary configuration; that is, it presents a methodology for generating a preliminary aircraft shape, size, and weight. Finalizing the preliminary configuration is described in Chapter 11.

The market specification itself demands improvements, primarily in economic gains but also in performance. A 10 to 15% all-around gain over existing designs, delivered when required by the operators, would provide market leadership for the manufacturers. Historically, aircraft designers played a more dominant role in estab­lishing a product line; gradually, however, input by operators began to influence new designs. Major operators have engineers who are aware of the latest trends, and they competently generate realistic requirements for future operations in discussion with manufacturers. To encompass diverse demands by various operators, the manufac­turers offer a family of variants to maximize the market share.

The product has to be right the first time and a considerable amount of back­ground work is needed. This chapter describes how to arrive at an aircraft prelim­inary configuration that will be best suited to market specifications and could be feasibly manufactured. Finalizing the design comes later through an involved iter­ative process using aircraft sizing and engine matching (see Chapter 11). In the
coursework, one iteration is sufficient. An experienced chief designer could start with a preliminary configuration that is close to the final arrangement.

There is no mathematics in this chapter; rather, past designs and their reason­ing are important in configuring a new aircraft. Readers need to review Sections 4.11, 12.8, 12.9, and 13.7 on design considerations and discussion to gain insight from experience. Statistics is a powerful tool that should be used discriminately. Researchers and academics have worked on statistics to a great extent; however, in many cases, current market demands have stabilized statistics (Section 6.4).

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