The prospect of reducing the induced drag of an aircraft by using both a canard and tailplane for trimming is investigated and results are compared with those for conventional tail-aft and canard arrangements. It is concluded that improvements of approximately 20% in lift-drag ratio are theoretically possible at high lift coefficients by the use of an additional trimming surface.

There is a history of criticism from aircraft operators, both civil and military, regarding the poor reliability of fuel associated systems, especially gauging, and the high pilot workloads that can result when a malfunction occurs during flight of light strike aircraft. In response the Ministry of Defence (Procurement Executive) sponsored work, initially at Smiths Industries and later at British Aerospace to investigate improved gauging and fuel management using digital concepts. It is concluded from flight trials that digital gauging will provide increased accuracy over a range of aircraft attitudes and with greater reliability than current analogue systems. Further, in a military aircraft, there are many advantages in a microprocessor based fuel management system which integrates fuel measurement, transfer and warning functions. These include reduced pilot workload, higher system integrity, fault detection, and system reconfiguration following battle damage. The evolutionary process leads naturally towards consideration of the inclusion of the fuel system functions in the centralised management of all the utility systems, based on Def Stan 00-18 data bus. Practical investigations of microcomputer based fuel and other utility systems are required to ensure that their full potential is realised within the limits imposed by the need for cost effective solutions.

It was recognised over 40 years ago that sweeping the wing of an aircraft could be used to offset the effects of compressibility. However, by no means all of the earlier swept-back wing aircraft used sweep for performance reasons. Some, such as the Horten tailless gliders built in Germany, had swept back wings to ensure necessary longitudinal stability. Likewise the Messerschmitt Me163 rocket interceptor employed a swept back wing as an essential feature of its layout but it operated at a sufficiently high Mach number for the beneficial aerodynamic effects of sweep to be of value. From the compressibility point of view, the wing may be either swept back or swept forward, and the idea of forward sweep was incorporated in the Junkers Ju287 jet propelled bomber (Fig. 1). The 18 degrees forward sweep enabled the wing-fuselage intersection to be positioned behind the deep bomb-bay and thus avoided a difficult structural cut-out problem. A more elegant solution to the same difficulty was the ‘crescent’ swept-back wing layout for the Handley-Page Victor bomber.

In shock wave turbulent boundary layer interaction, upstream influence is defined as the distance from the inviscid shock wave to where the incoming boundary layer is first disturbed. The latter position is generally taken as being where the mean wall pressure first increases above the undisturbed value. Wall pressure fluctuation measurements in two Mach 3, high Reynolds number interactions have shown that unsteadiness of the separation shock wave structure results in the instantaneous upstream influence varying over a range of values. Upstream influence as defined above is actually the maximum of this range and, at this distance upstream of the shock wave, the probability of finding the flow disturbed is correspondingly low. The minimum value of the range is the distance from the inviscid shock wave to where the incoming flow is always disturbed. In all of the cases studied the latter station was found to be just upstream of the separation point.