The responses of systems, whose equations of motion are linear, to arbitrary applied forces are conveniently calculable by the use of impulsive or indicial admittances. Expressions for these admittances are here given explicity for some simple dynamical chains and the procedure for their calculation in chains with more degrees of freedom is outlined. Some general characteristics of the dynamical chains are also examined.

Curves are presented which, together with a knowledge of the intake performance, enable ram-jet thrust coefficients and specific consumption figures to be obtained quickly and accurately in the range M = 1·0 to 3·0.

As pointed out in previous work, in the method of collocation the functions used usually need not be orthogonal or integrable in closed form. Therefore function of different types may be mixed together in representing unknown quantities. Such function may be aptly called hybrid functions. Also, it has been found that usually it is better to represent unknown quantities by similarly looking functions instead of by a series involving higher harmonics. The idea is that by using similar looking functions it is possible to avoid poor regions for collocation, such as near nodal points, and so on, and closer fit in certain regions is assured. Thus if one knows approximately what the function sought looks like, one should try to find a set of function all of which resemble this desired shape, instead of taking an arbitrary set of harmonics when using the method of collocation. Simple examples below illustrate this approach and indicate the good results that can be expected in general.

A sequence of high Reynolds number two-dimensional entry flow problems is considered by varying the form of the entry profile from one representing uniform shear to one representing different parts of a Poiseuille profile. The detailed development of the entry flow is illustrated in a few cases. The entry length, pressure drop, and pressure loss in the entry region are given in each case.

The ability to operate when runways are flooded or slush-covered to some degree, must be demonstrated during the certification programme of any new civil transport aircraft. Failure to meet the requirements laid down will result in operating restrictions which may jeopardise the sales prospects of the aircraft. Most other types of aircraft will also have to operate occasionally in these adverse conditions.

The main problems result from the spray generated at the wheels, and are engine malfunction due to spray ingestion and damage due to its impingement on the airframe. An associated problem is the packing of slush into ducts, flap cavities, undercarriage bays, etc, with the attendant risks of damage to internal systems and jamming of mechanical parts. There is also a large additional drag load on the aircraft, due to the displacement of fluid by wheels and to spray impact on the airframe: this increases roughly in proportion to the depth and effectively limits the slush depth that can be tolerated on the runway. For many aircraft this limit is little more than one centimetre.

One of the great challenges of our time lies in the exploration of space. Part of this challenge has already been fulfilled but, up to this date, the transport of men and materials has been accomplished by means of expendable booster systems. In order to meet this challenge effectively, a new, fully reusable transportation system has been conceived which will be dramatically lower in overall cost than present-day launch systems. The proposed space shuttle is a fully reusable spacecraft consisting of a booster and an orbiter. A key factor in the design of the space shuttle is the selection and development of materials. Many current materials which have been widely and successfully used in space vehicles were developed for the most part with only a single short-time use requirement. The reusable, long-life requirements of the shuttle vehicle necessitates re-evaluation of the suitability of existing materials for this distinctly more demanding task for materials.

Kinetic heating, which is associated with supersonic flight, is probably the greatest challenge which has confronted the structural engineer, since the design and analysis of affected structures requires a radical extension of current practice. For example, the laws of heat transfer and the effects of high temperature on structural materials become important factors in structural analysis. To obtain a clear appreciation of the situation it is therefore necessary for the designers of the structure to become familiar with these factors, together with certain aspects of boundary layer theory.

Fleet planning is a complex process. Undertaking it is time consuming as, properly conducted, it involves virtually every part of the airline organisation in a series of sub-analyses all of which impact on each other in some way. Parts of the process are deeply technical but others may be purely subjective relying on the intuition or judgement of the airline’s one expert in the particular field.

Obviously in fleet planning we have to investigate suitable types of aircraft. Most of the factors involved are fairly well known. Their ability, or otherwise, to operate our routes economically and without significant restriction is vitally important as is our ability to maintain them in service. We need to understand our markets and the factors which influence passengers to travel in the first place, and with us rather than our competitors in the second.

In recent years, there have been rapid advances in the development of theoretical methods in aerodynamics, particularly for transonic flow calculations. Many papers have been written on this topic. It is however appropriate that there should now be a paper that concentrates not so much on the methods themselves but on the use of the methods for computer-aided design. One could say that the most striking development in the UK in the past two-three years has been that the methods are no longer merely within the preserve of the research establishments; they are being actively used by the aircraft industry in the design of actual aircraft projects. Any air of scepticism about their value has been dispelled. The designers are now appreciating through their own experience that with the aid of a powerful computer and indeed in some cases, a computer of only modest capacity, they can specify a shape for the first wind tunnel model of a new project with much more confidence that the test results will show that the shape is near what is required to achieve their design objectives. It is already being claimed that in this way, the time-scale of the design cycle is being shortened considerably. Also, the computer and the theoretical methods are being used increasingly in the interpretation of the test data. The forecasting of the full-scale characteristics on the basis of the model test data is developing into more of a science and less of an art based on past experience.

The experimental methods in current use for the determination of the dynamic properties of an arbitrary finite-freedom system are based on restrictive assumptions which may often be of questionable validity. The most common assumption is that the damping matrix can be reduced to a diagonal form by a congruent transformation using the modal matrix of the undamped system. Further, the damping is normally assumed to be hysteretic, or light if viscous.

Bishop and Gladwell give an excellent account of the theoretical background of the present experimental techniques. These can be divided into three groups:

• 1. The method of Kennedy and Pancu which obtains experimentally the complex receptance of the system and extracts its dynamic properties from vectorial plots.

• 2. The method of Trail-Nash and Asher which is based on the experimental determination of the in-phase response of the system and requires computation to be incorporated with the experimental procedure.

Following a brief description of the basic radio aids and the terminology used, the paper discusses in some detail the differences between the original British and American approaches to all-weather landing; the different types of equipment resulting from these two approaches are broadly described. The mixing of ideas which occurred at the IATA Conference at Lucerne in 1963 and the more recent tendency towards a blending of British and American ideas are then discussed, and some predictions are made as to the form of the ultimate all-weather landing system. Certain Australian contributions to display research and the simulation of low visibility in flight are mentioned in context.

For some years the author has been interested in subsonic ram-jets as a means of helicopter rotor tip propulsion and has done a considerable amount of experimental work with this end in view. Most of the effort has been concentrated on producing engines to operate at the lower end of the speed range as it was thought that, however simple a ram-jet may be, this advantage is lost when other means of propulsion are needed for starting purposes.

The paper concerns a phenomenon which occurs in rows of closely spaced blades, as in an axial flow compressor, when the flow around the blades approaches the stalling condition. Patches of stalled flow can propagate along the blade row, thus causing cyclic variations in the lift on individual blades. Under certain conditions this cyclic loading can lead to large blade stresses, and ultimately to blade failure.

Prior to 1914 there was no night flying proper, as we know it to-day, and therefore, so far as I am aware, there was no night lighting. I must except, of course, the night flying exhibitions which were given at Hendon in this country and at a few places abroad.

As concern for the environment increases, so does the desire to reduce emissions and improve fuel efficiency. One avenue being investigated in the aerospace industry is the reduction in losses in a gas turbine engine through endwall contouring, which has shown some promise in improving efficiency. The current investigation was aimed at investigating the unsteady effects downstream of a rotor with a non-axisymmetric endwall contour originally designed for a cascade.

Previous investigations (numerical and experimental) have shown that the endwall contour improved the turbine efficiency by reducing the cross passage secondary flows. The contour however had a detrimental effect on the tip flow. The current investigation found that there were negligible unsteady differences between the annular and contoured rotor, with the average comparing well to the steady state results. It was also found that the effects at the tip were due to the experimental blades untwisting during operation.

Subsonic wind tunnel experiments were conducted to study the effect of forced transition on the pressure distribution in the concave portion of contraction. Further more, the effect of early transition on the turbulence level in the test section of the wind tunnel is studied. Measurements were performed by installing several trip strips at two different positions in the concave portion of the contraction. The results show that installation of the trip strips, have significant effects on both turbulence intensity and on the pressure distribution. The reduction in the free stream turbulence as well as the wall static pressure distribution varied significantly with the location of the trip strip. The results confirm the significant impact of the tripped boundary layer on the control of adverse pressure gradient. The trip strip at X/L = 0.115 improves pressure distribution in contraction and reduces turbulence intensity in the test section, considerably.