An existing system in the aircraft industry. The British Aircraft Corporation Numerical Master Geometry system

Abstract

In May 1965 the author started experimental work on numerical geometry, his terms of reference being to devise a system whereby the external shape of an aircraft could be represented numerically in a form allowing the necessary information for design and manufacture to be produced quickly, using a digital computer. The technique in use at British Aircraft Corporation, Weybridge Division, at that time was that of ‘lofting’, an extension of the graphical system, descriptive geometry (Robertson 1966). Lofting used nests of parallel plane sections, drawn out full size on metal plates, to define the shape of the aeroplane. (The term derives from shipbuilding practice where the loft of the shipyard was the only place large enough to draw-out a complete ship full size.) The other Divisions of the British Aircraft Corporation were using ‘conic lofting’, whereby the plane sections were fitted by piecewise second degree curves (Shelley about 1947). This enabled the graphical constructions to be replaced by desk calculations, with some advantages in speed, accuracy and repeatability. The Vickers Valiant bomber had been defined in terms of conic lofting at Weybridge, but this had not been followed up.