5 Aircraft Load

5.1 Overview

Aircraft structures must withstand the imposed load during operations; the extent depends on what is expected from the intended mission role. The bulkiness of the aircraft depends on its structural integrity to withstand the design load level. The heavier the load, the heavier is the structure; hence, the MTOW affecting aircraft performance. Aircraft designers must comply with mandatory certification regulations to meet the minimum safety standards.

This book does not address load estimation in detail but rather continues with design information on load experienced by aircraft. Although the information provided herein is not directly used in configuring aircraft, the knowledge and data are essential for understanding design considerations that affect aircraft mass (i.e., weight). Only the loads and associated V-n diagram in symmetrical flight are discussed herein. It is assumed that designers are supplied with aircraft V-n diagrams by the aerodynamics and structures groups. Estimation of load is a specialized subject covered in focused courses and textbooks. However, this chapter does outline the key elements of aircraft loads. Aircraft shaping dictates the pattern of pressure distribution over the wetted surface that directly affects load distribution. Therefore, aircraft loads must be known early enough to make a design “right the first time.”

5.1.1 What Is to Be Learned?

This chapter covers the following topics:

Section 5.2: Introduction to aircraft load, buffet, and flutter

Section 5.3: Flight maneuvers

Section 5.4: Aircraft load

Section 5.5: Theory and definitions (limit and ultimate load)

Section 5.6: Limits (load limit and speed limit)

Section 5.7: V-n diagram (the safe flight envelope)

Section 5.8: Gust envelope

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