This paper presents the results of the experimental study carried out to address the issues of base heating and smooth separation of the stage of launch vehicles. The pressure at the base of a convergent-divergent circular nozzle, from which Mach 1.8 jet emanates, attached to an annular shroud of larger area is controlled by providing air vents on the shroud. On the shroud, vent holes were made at different azimuthal locations, to entrain the surrounding air mass at a higher pressure, pa, to increase the low-pressure, pb, at the base region, caused by the suction creating large-scale vortices formed owing to the sudden expansion of the jet emerging from the nozzle into the shroud. For different number and size of the vents on the shroud, the base pressure was measured. This measurement was done at five levels of overexpansion of the nozzle in the range from –64% to –58%. It is found that increase in vent area results in increase of base pressure, up to some limiting level of the area. Also, the increase of base pressure for the case of vents closer to the nozzle exit is found to be marginally more than the increase caused by vents at distances away from the nozzle exit. Increase of base pressure can be regarded as an advantage not only from base heating point of view but also from the point of view of deflection of the plume to the shroud wall for uniform melting of the pyro layer bonding the stages of the launch vehicle, leading to a smooth separation of the launch vehicle stages.

Introducing Captain FAY, MR FITZWILLIAMS said it would be generally agreed, that very few people, if any, in the world were better able to discuss the subject The lecturer held the rank of Captain in British European Airways, and had served with the Helicopter Unit of the B E A since its inception in 1947, when it was based on Yeovil, and when the Chairman had had the pleasure of meeting him and his colleagues The activities of that Unit had covered a very wide range of helicopter operation, including an intensive pioneering effort in helicopter blind flying

As a Fleet Air Arm pilot he had learned to fly in 1940, and had served for two years in H M S “Victorious” Afterwards he had joined the Naval Service Trials Unit, and was converted to helicopters at the first helicopter training course in this country, at Hanworth, in 1944

In recent times, there has been increased focus on the utilisation of virtual reality flight simulators in flight training, driven by their advantages compared to conventional methods. However, a paucity of empirical evidence has prevented their widespread introduction and regulatory approval. Existing research focuses on single-user simulators, leaving a gap in studies of collaborative training within virtual environments. Consequently, this paper investigates evidence-based simulator training within a collaborative virtual environment.

A mixed methods approach was adopted, where behaviours related to industry-standard competencies were observed in a virtual reality complex aircraft and thematic analysis applied to a post-experiment participant debrief. The findings showcase the feasibility of utilising a collaborative virtual environment for evidence-based training purposes in scenarios aligned to typical initial First Officer airline training programmes, which is a precursor to supplementing traditional professional pilot training techniques. In addition, the study found that the visual barriers imposed by head-mounted displays were overcome through the adoption of refined communication strategies, thus laying the groundwork for physically separated multi-crew pilot training.

The compressible subsonic flow about an oscillating two-dimensional aerofoil in a wind tunnel with porous walls is considered. The porous wall is assumed to exhibit the property that the ratio of the normal velocity at the wall to the pressure drop across the wall is constant. The aerodynamic derivatives are found for quasi-steady pitching motion of the aerofoil. The dependence of the derivatives on Mach number and wall porosity is displayed graphically.

Flow measurement by optical devices of various types, particularly those involving laser light sources, have received considerable attention over the last few years. Different schemes employing a wide range of optical layouts have evolved and the resulting signals have been processed in a number of ingenious ways. We report new experimental work on an optical instrument that can be considered as the forerunner of the laser anemometer in the belief that in certain circumstances this particular optical layout offers some real advantages over the majority of laser anemometers. One important advantage of this system is the ease with which both the shape and size of the sampling zone can be independently controlled. Another is the ability to position the sampling region very close to a boundary without having to contend with the surface reflection difficulties that often prevent such measurements being made with laser optics. The instrument measures the velocities of small particles suspended in the fluid in much the same way as the laser anemometer. In unsteady flows this results in a series of velocity estimates generated at random time instants. These intermittent samples of the velocity are used to form power spectral density estimates by methods recently developed for the analysis of randomly sampled records (Gaster and Roberts, 1975 & 1976). This method of analysis could well be applied to the processing of the signals generated by laser anemometers operating in the burst counter mode.

This note discusses changes in the state of a gas flowing in a duct of constant area. In the past, changes, such as normal shock waves, combustion and other phenomena, which are defined by the equations of energy, conservation of momentum and mass flow, have each been treated on their merits. In this note a method is developed whereby all phenomena governed by these three equations can be solved by a single general method. The method rests on the derivation of a parameter which is unaltered in value by the change, in all cases where the total temperature is constant. A shock wave is an example of such a discontinuity. In problems of heat addition or extraction, the parameter changes its value only because of the change in total temperature. The change in total temperature may be calculated from the known quantity of heat added or extracted.

The parameters derived are useful in showing how problems of this type should be attacked analytically. With oblique waves it is easy to derive a relation between the normal velocities before and after the wave, and it is probable that this relationship has not been published before.

A study is made on the aerodynamic interference between a wing and a surface of velocity discontinuity in a non-uniform potential flow field. Actually, the surface of velocity discontinuity is deformed around the wing, which penetrates the surface, but no theoretical predictions of the surface deformation can be found in existing papers. In the present paper, a deformation of the surface is theoretically predicted, leading to the conclusion that a “sectorial region” will be formed on the wing. Formation of the sectorial region is recognised in new experiments and in many existing experimental results. Both theoretical and experimental analyses are made of the physical roles of the sectorial region.

A simple theoretical analysis is given of the quantities affecting the sensitivity and range of a schlieren apparatus. In regions of large density gradient the deflections of the light rays may lie outside the normal working range. When this occurs, dark regions may appear in parts of the photograph that would normally be light. Examples of this effect are given, and it is shown that confusion can be avoided by taking photographs in pairs, with the knife edges or slits arranged to give sensitivities of opposite sign.

The deflections of light rays in various typical disturbances in a supersonic air stream are calculated, using geometrical optics. Prandtl-Meyer expansions, boundary layers, and plane and curved shock waves are considered. From these calculated deflections it is shown that some of the anomalous effects commonly observed in schlieren photographs can be explained.

A theory is presented for the airflow and power requirements of a compressible hovercraft jet operating under equilibrium conditions. It is shown that, even for a partially sonic jet, these requirements may not differ markedly from those of an incompressible peripheral jet.

The flows resulting from a number of different methods for producing swirl in an axi-symmetric jet have been investigated. These methods include upstream vanes, tangential injection, a twisted plastic sheet and rotation of part of the jet pipe. Tests were also made with the first two types of swirl device in association with a radial distribution of axial velocity in the jet which had a minimum on the axis produced by a suitably graded wire grid or web inserted in the jet pipe. The measurements covered the mean (axial and swirl) velocity distributions as well as the main turbulence quantities at various stations downstream of the jet exit. It was found that the swirl considerably enhanced the rate of growth of the mixing region as previous workers have shown, but there was a significant reduction of this enhancement when the axial velocity increased from the centre outwards. This is in accordance with current concepts on the stability of curved turbulent shear flows.

The BAC subsonic lifting-surface method is applied to the problem of evaluating the downwash at the surface of wings of rectangular planform subjected to particular loadings and the results are compared with a set of datum results. Over 95 per cent of the wing span the results of the BAC method are shown to be accurate to within 0.01 per cent, irrespective of chordwise position.

Hypersonic small-disturbance theory is applied to the source flow over power-law slender bodies with conical or wedge type asymptote. The results for a point source flow with λ=2 over power-law cones of revolution show that the dominating equations in the first and second approximations are essentially the same as the ones for the parallel flow over power-law bodies of revolution. In the special case of a cone, results of a source flow and of a parallel flow are compared and it is shown that the surface pressure in a source flow at the nose is the same as the constant cone pressure in a parallel flow, but systematically decreases in the rear part. This is confirmed by comparison with a shock tunnel experiment.

An exact analysis is first given, within the spirit of elementary theory, of the torsional modes of a uniformly tapered solid wing whose section shape - as distinct from size - is constant. Numerical results are presented for the first five torsional modes for various values of tip chord/root chord. It is shown that the frequencies are fairly insensitive to the magnitude of the taper and a corollary to this, which is also investigated, is that an analysis based on a partially stepped representation of the taper yields close estimates of the frequencies but can yield massive differences in the higher mode shapes. An analysis is also made of warping restraint and distributed inertia effects.

A theoretical analysis is presented for a two-dimensional air strut with walls consisting of thin membranes which are joined by many inextensible strings. The strut is deflected through large angles so than an appreciable portion of each membrane is buckled and lies along the solid plates which form the ends of the strut. Numerical solutions are obtained for two cases and, in particular, the resultant force on each end plate is determined.

Thin-walled tubes, in. in diameter, of three hard aluminium alloys and of mild steel have been tested in fatigue under three systems of alternating stresses while subjected to biaxial mean tensions imposed by means of internal pressure. In fatigue under direct or bending stresses the hoop tension in the walls of the aluminium alloy tubes did not seriously reduce the fatigue endurance, but it did markedly affect the mode and rate of crack propagation; cracks initially transverse to the tube axis tended to develop very rapidly in the axial direction. This tendency was present under both fluid and gas pressure, and under gas pressure the cracks propagated so fast that the test piece was often blown to pieces before the gas pressure fell by leakage through the cracks. The gradual taper in wall thickness along the fillets joining the test section to the enlarged ends offered no barrier to propagation of the axial cracks and the whole test piece, including its enlarged ends, was often shattered. Propagation of the axial cracks was preventible by sufficiently reducing the fillet radius, or by a ring glued on. Under alternating torsion, both endurance and mode of failure were affected by internal gas pressure. The initial fatigue crack, either circumferential or axial, often extended over a length comparable with the diameter of the tube, except under low ranges of shear stress when the crack length was sometimes very short. At each end the cracks forked in a characteristic manner and under moderate gas pressure the portions of tHe wall between the prongs of the fork were blown outwards. Under high pressure explosive failure and fragmentation often occurred. Mild steel under alternating torsion with internal gas pressure exhibited the same modes of failure, and two or more fatigue cracks were often formed simultaneously. Under high hoop tension, cracks propagated rapidly and one test piece, after two million cycles endurance, failed by exploding. However, no mild steel test piece was fragmented. A tentative explanation is offered of the reason why, in tubes of small diameter, rather short fatigue cracks may be expected to lead to fast fracture under the static loading. Attention is drawn to the inference that the initial fatigue crack itself must develop very quickly to considerable length.