The RAF has been undertaking peacetime repairs on composite rotor blades, fibreglass radomes and panels on a variety of combat aircraft types for many years. However, the Service's main experience in the repair of aircraft structures manufactured from carbon fibre composite (CFC) material has been related to the Harrier II. In any future conflict involving air power, battle damaged aircraft, including the Harrier II, will have to be repaired rapidly to meet operational requirements. The repair techniques used may have to differ from those undertaken in peacetime but they must still aim to restore the full static strength of the aircraft within the time constraints imposed by the operational situation. Therefore, aircraft battle damage repair (ABDR) is a carefully planned alternative to conventional repair techniques. This paper describes the main CFC structures of the Harrier II and outlines the variety of RAF peace and wartime structural repair procedures applied to the aircraft. Examples are provided of various simple and complex repairs. Greater emphasis on adhesively bonded repairs is called for if Harrier II experience is to aid in the logistic support of Eurofighter 2000 (EF2000) in peace and war.

A windtunnel study was undertaken to determine the effects of delta planform tip sails (DPTS) on the aerodynamic characteristics of a planar blunt edged wing. In the investigation, the sail incidence and chordwise attachment position were varied. The results indicate that significant performance improvements can be obtained with DPTS. For all DPTS variations, increases of lift curve slope, maximum lift coefficient and Oswald efficiency factor were recorded and compared to the basic wing.

Two major technologies in aeronautics promise substantial improvements in the fields of economy and ecology. One is laminar flow technology and the other arises from new developments related to aircraft turbofan engines. The trend in turbofan engine development is towards engines possessing higher bypass ratios. This, however, entails larger engine dimensions, leading not only to an increase in the skin friction drag but also to negative engine-airframe interactions. As a consequence, the need for laminar flow nacelles becomes all the more important as part of the general process of engine-air-frame integration optimisation for advanced transport aircraft.

This paper deals with some results obtained from flight tests with a laminar flow nacelle demonstrator and specifically addresses the topic of aerodynamics of intakes and nozzles. The results described relate to a European collaborative programme in which a natural laminar flow (NLF) nacelle was flight tested. Results of the effect of the angle of yaw on the static pressure distribution on the fan cowl including the intake of an NLF nacelle are presented for the maximum cruise flight condition. At zero yaw, a comparison of Euler calculations with flight test data is made. Measured flow variables of the fan nozzle flow directly downstream of the fan nozzle exit, exemplified by the Mach number and the flow density distributions, are also presented for the condition of maximum cruise.

A new method has been used to solve the transonic flow equation for flow over a wavy wall. The results thus obtained are compared with those obtained from windtunnel experiments. A new fluctuating flow phenomenon has been observed both in the experiment and in numerical calculations which may enhance flow mixing. The numerical results also indicate that the flow becomes locally sonic for a transonic parameter value greater than 0·5, while experimental data indicate a value of 0·6363 for the transonic parameter. The classical value of transonic parameter has a value of one for the flow to become locally sonic.

In recent years the increasing importance of electronic warfare has resulted in a proliferation of assorted antennae, large fairings and other foreign bodies attached to transport aircraft airframes. In many cases the size, shape and location of these excrescences are fixed by the requirements of the relevant electronic devices and it is then left to the engineers and aerodynamicists to attach them to the airframe in the least adverse manner.

This note describes an installation which was extensively tested in a large-scale commercial windtunnel and was found to give apparently well-behaved steady-state aerodynamic characteristics but which, when flight tested, exhibited unacceptable levels of airframe buffeting and rather unusual directional stability problems. A re-examination of the fuselage flowfield using a simplified model, but with attention focused on the unsteady aspects of the flow, rapidly identified the underlying cause and enabled a successful aerodynamic fix to be developed. The lessons learnt from this experience are presented as a warning to those contemplating the addition of large excrescences to any airframe.

Energy considerations are used to find the spanwise circulatory lift distribution yielding minimal induced resistance for a harmonically oscillating planar wing in a steady incompressible flow. Under the restriction that the time-averaged and oscillatory constituents of the wing's circulatory lift are known, the optimal distribution is such that its time-averaged constituent is elliptical, but the oscillatory one is generally not. The latter varies from elliptical to rectangular as the frequency of the oscillations increases. When the oscillatory part of the lift is not prescribed, present results infer that its reduction — as, for example, by an elastic twist — will typically reduce the drag, even if the twist yields a non-optimal (for that lift) lift distribution.

A windtunnel study was undertaken to determine the effectiveness of leading edge vortex plates in enhancing the lifting abilities of a blunt edged delta wing. In the investigation, vortex plates were attached to both the upper and lower surfaces of the leading edge. Various positions of the vortex plates with respect to the wing's leading edge were evaluated. The results indicate that a vortex plate located on the upper surface of the wing is capable of increasing lift so as to be comparable to a similar sharp edged wing, whilst reducing drag through some retained leading edge thrust. The increase in zero lift drag associated with vortex plate attachment tends to limit potential performance improvements. A vortex plate mounted on the lower wing surface decreased lift slightly compared to the blunt wing. However, drag was found to decrease markedly.