TABLE OF CONTENTS "Ut tensio sic vis" (As the stretch so the force).
Robert Hooke
Fundamentally, an aircraft is a structure. Aircraft designers design structures. The structures are shaped to give them desired aerodynamic characteristics, and the materials and structures of their engines are chosen and shaped so they can provide needed thrust. Even seats, control sticks, and windows are structures, all of which must be designed for optimum performance.
Designing aircraft structures is particularly challenging because their weight must be kept to a minimum. There is always a tradeoff between structural strength and weight. A good aircraft structure is one that provides all of the strength and rigidity to allow the aircraft to meet all of its design requirements, but which weighs no more than necessary. Any excess structural weight often makes the aircraft cost more to build and almost always makes it cost more to operate. As with small excesses of aircraft drag, a small percentage of total aircraft weight used for structure instead of payload can make the difference between a profitable airliner or successful tactical fighter and a failure.
Designing aircraft structures involves determining the loads on the structure, planning the general shape and layout, choosing materials, and then shaping, sizing, and optimizing its many components to give every part just enough strength without excess weight. Because aircraft structures have relatively low densities, much of their interiors are typically empty space, which in the complete aircraft is filled with equipment, payload, and fuel. Careful layout of...
