The Directory attempts to list all heavier-than-air flying machines, whether models or of man-carrying size, which are said to have been built and tested in western Europe prior to the Montgolfiers. While I do not include machines which are known to have been totally imaginary, I have been fairly liberal in my sifting of the evidence. Thus the list includes items ranging from those about which there is no historical doubt whatever (eg, the ornithopters of Blanchard) to others which may never in fact have existed (eg, the zany structure conceived by d'Alcripe's drunken Norman labourer).

Bonus schemes have tended to fall into disrepute and have been neglected; this is a pity because they are an extremely powerful tool when applied successfully. One of the weakest areas of the individual bonus scheme for cost control was the setting of standards through individual negotiation influenced by many factors, rather than by estimating the work content.

During 1975, the individual bonus scheme was suspended at British Aerospace Weybridge-Bristol Division, Filton Site, and a start was made on the development of a cost control system based on work measurement and using modern computing techniques. The new system had to contain two essential features. First, the speedy identification of jobs giving problems on the shop floor, since it was realised that the suspension of the individual bonus scheme would slow down this process, secondly the provision of a fast and reliable method of checking the work issued to the shops against the original estimates.

The technique of geometric programming is applied to the design of optimum wing bend boxes in sheet-stringer-rib construction. The work extends the previous application in multi-spar design and the results for the different configurations are compared. Closed-form design equations are given for the case of buckling constraints whereas more complex formulations with stress constraint were solved by computer.

The RAE Boundary Layer Tunnel is an open return facility driven by a 100 hp ventilating fan. It is provided with interchangeable working sections of cross-section either 1·2m × 0·3 m or 0·6 m × 0·6 m. There is no diffuser downstream of the working section which exhausts directly into the test room. The tunnel was arranged in this way to avoid restrictions on the design of the working sections and also in order to enable control of the pressure in the working section by means of a screen over the exit. This control made it possible to bleed flow from the working section, to avoid unwanted separations, for example, or to provide some special flow characteristic.