Aerobasics —An introduction to aeronautics

The structure of an airplane holds it together in flight without significant deformation due to flight loads. It contributes to about a quarter of the airplane take-off structure weight results in an equal increase in disposable load (fuel or payload) and thus contributes significantly to improved performance or economy. Thus great pains are taken by the designers to make an airplane structure as light as possible consistent with strength and stiffness. This structure is primarily of semi-monocoque design. This implies that it is designed as a hollow stiffened shell in which the skin contributes a major share to its strength and stiffness. In this article, we describe the general principles of design of this type of structure. We indicate the nature of flight loads the structure has to resist and the design concepts which ensure that the structure is safe during the life of an airplane.