FUNDAMENTALS OF AIRLINER DESIGN―PART 13 STRUCTURES AND MATERIALS I

摘要

Compared to 19th century engineering, the need for really lightweight structures was a new one. However, the wings of an aircraft are subjeet to bending forces, very much like a bridge, and since there was a good deal of precedence, bending loads could safely be dealt with. Wing spars, of 'I' or box section, were continuous beams on three or more supports, each bay of a biplane carrying an axial load in addition to the lateral load from the air forces. Early aircraft were built mainly of wood and mild steel tubing, with coverings of fabric that, when doped, shrank to give a taut surface. The biplane's strength resided in the spars and the external bracing. The ribs were necessary to hold the fabric covering to the correct profile. but they did not contribute much to the strength (even less so the fabric). Strength calculations was no fairly straightforward, for the structure was no more than an ordinary braced girder: Nevertheless, it was some time, during which many lives were lost, before the stressing conditions to which an aircraft is subject were more fully understood.