The aerodynamic interference between typical tanker and large receiver aircraft during air-to-air refuelling was modelled using a simple horseshoe vortex representation of the tanker wake whilst the aerodynamic forces and moments acting on the receiver were calculated using the vortex lattice method. For each combination of tanker and receiver, the aerodynamic loads depend mainly on the vertical separation, whilst the receiver tailplane position on the fin strongly effects the pitching moment acting on the receiver due to the tanker downwash. Particular attention was given to a high T-tail receiver aircraft. The predicted increase in the receiver drag compares favourably with available flight test data. Changes in trim in pitch of the receiver were analysed and related to the static stability of the aircraft. Aerodynamic derivatives due to the position and attitude of the receiver aircraft within the tanker downwash field were calculated and solutions of the linearised equations of motion obtained for the high T-tail receiver refuelling from different tanker aircraft at different flight conditions. Typically the receiver exhibited a divergent oscillation at the normal refuelling position. The dynamic stability characteristics are consistent with the trends observed in flight tests on the tendency of the receiver to oscillate in pitch.

Under zero-gravity conditions, the liquid surface in a container has a displaced equilibrium position due to surface tension effects; this depends upon the magnitude of the contact angle to the wall. Free and forced sloshing have been investigated for these conditions. It was found that the natural frequencies of the liquid increases with the contact angle to a maximum value at a contact angle slightly above π/2 and then decreases. This behaviour is not symmetrical within the wetting and non-wetting range. Thus, a completely non-wetting liquid has larger natural frequencies than a completely wetting liquid. It was also found that the sloshing mass of a wetting liquid is considerably larger under zero-gravity than under normal gravity conditions and that a non-wetting liquid exhibits substantially reduced sloshing mass, indicating that the influence of liquids with a small contact angle on the dynamics of a vehicle with liquid containers (with a free liquid surface) may be quite pronounced.

Most organisations predict that the expansion of satellite applications to new areas, such as land mobile communications, will be in a rapid worldwide growth phase up to the end of the century. The geographical and geometrical link properties along with the economic aspects (with the projected saturation of the frequency allocation), have led communications services to consider non-conventional orbits for the near future. This paper presents an analysis of the fundamental problems and a statement on the short-term technical solutions within the particular framework of a general land mobile communication mission. The results of these efforts led the authors to propose the Sycomores concept, which is at least a twin satellite system located on particular inclined elliptical geosynchronous orbits.

The report concerns the response of a shear flow to the insertion of a small obstacle at an impermeable wall. A calculation method is described which makes use of elementary potential flow theory although the solutions obtained are not potential flows. The first inviscid approximation to the response is computed explicitly in a number of different cases and qualitative features of the solutions are found in accordance with expectation. Their relevance to a more accurate determination of the flow is discussed.

Recent experimental and computational studies have indicated that rearward curvature of a wing can reduce the induced drag factor to values less than that obtained from the unswept elliptical wing considered optimal in classical wing theory. Wake non-planarity associated with a wing with aft swept tips has been suggested as a reason for this behaviour. This paper provides a systematic examination of the wake non-planarities induced by a variety of wing planforms and quantifies the induced drag reductions which may be expected. Results suggest a dependence of induced drag factor upon angle of attack, and therefore upon lift coefficient. The crescent wing is identified as the planform to derive the most benefit from its non-planar wake shape, typically a 4% reduction in induced drag factor at moderate angle of attack.