Quite often, those whose honour it has been to deliver the Wilbur Wright Memorial Lecture have used the occasion to present a survey of progress along a fairly broad front and thence to predict what the future holds in store.

It may be that the courage, insight in experiment, and skill in craftsmanship, which culminated in that successful demonstration of fifty years ago last December, have excited those whose privilege it has been to commemorate that achievement to undertake flights in the realm of prophesy. A time so near the fiftieth anniversary might be considered unusually appropriate to historical review and philosophic speculation, but since Sir Harry Garner's 1952 Lecture “Prophesy and Achievement in Aviation,” the Royal Aeronautical Society has been busily converting crystal balls into models of the Montgolfiere balloon.

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.

Aircraft noise disturbs a significant number of people who live close to airports. It is tolerated due to the economic and social benefits those aircraft bring to society as a whole. However, the levels that are tolerated from individual aircraft must reduce, to compensate for increases in numbers of aircraft movements and the desire for an ever-improving environment for all of society's members. The issue is how to achieve that reduction without destroying social and economic benefits of air travel.

In his excellent review of the “state of the art” of effusion cooling (p. 73, February Journal, 1959), Dr. P. Grootenhuis clearly distinguishes the two mechanisms which contribute to the cooling effectiveness; namely, efficient abstraction of heat from the porous wall material by internal transfer to the effusing coolant, and reduction of the rate of external transfer of heat from the stream to the wall as a result of boundary layer injection. An observation that deserves emphasis, however, is that the first of these mechanisms is the predominant one. This fact is illustrated by the good agreement between the theory assuming laminar flow conditions (i.e. involving integration of the Navier-Stokes equations and the use of a one-parameter velocity-profile expression proposed by Schlich-ting for the laminar boundary layer with injection) and the various experiments, all of which involved turbulent stream conditions. This observed agreement indicates that the surface temperature is primarily controlled by the internal heat transfer within the porous wall and is relatively insensitive to the external heat-transfer conditions.

The standard method of strength calculation of a framework is based on the assumption that members are freely pinned together and external forces are applied only at nodes. Actually aircraft fuselage members are stiffly joined and transverse forces are often acting on them at considerable distances from nodes, e.g., weights of crew, instruments and oil, reactions of controls, stabiliser adjusting gear, etc.

The safest method of computing stress in such members is to assume both ends pin—jointed. As they actually are stiffly connected to adjacent members, they are not allowed to twist freely, i.e., the truss exerts moments on the loaded member. The effect of these end moments consists in diminishing deflection andfield moments. The decrease of maximum bending moment may attain nearly 50 per cent.

Since framework members are designed to withstand axial forces only, viz., tension or compression, they are comparatively weak against bending and have to be strengthened appreciably if transverse forces are present.

Handley Page Jetstream G-NFLC has for many years been used to complement the theoretical teaching material on undergraduate and postgraduate aeronautical engineering courses through a set of airborne laboratories designed to expose students to practical measurements in a realistic environment. It is suspected by some of the Cranfield test pilots that the aeroplane may be prone to pilot involved oscillations in pitch during the flare; the most likely causes are a deterioration in the short period dynamics at aft centre of gravity locations and adverse longitudinal stick force characteristics. To date however, no objective data has been available to support this hypothesis. This study reports upon an experiment designed to quantify these effects by identifying linear models of the short term dynamics from flight-test data, and assessing them against the Gibson drop-back and phase rate criteria. As expected, a rearward shift in the centre of gravity causes the airframe short period pitching oscillation (elevator deflection to pitch rate) to become more sluggish, thereby producing a significant reduction in dropback, which can be traced directly to the size of the static margin. The longitudinal stick force characteristics have a negative impact on the response, causing a reduction in dropback and a substantial increase in phase rate.

The past has been interesting, but what of the future? As Fig. 1 shows, extrapolation is an attractive tool, with pitfalls for the incautious - most often exemplified in aerospace by the prediction that by 2015 the entire US defence budget would fund one aeroplane, or more recently by the belief that avionics will expand into infallibility and reduce costs to invisibility. The first extrapolation is premature, and the latter two as near as makes no difference wrong.

In the case of the single affordable US defence aircraft the extrapolation probably correctly estimated the 2015 US defence budget, but erred in expressing the US Department of Defence requirement in terms of aircraft rather than damage-effects on target. The subsequent step change in avionics miniaturisation undermined the extrapolation and now looks likely to enable the DoD’s damage-effect requirements to be attained using products that lie on a different cost-effectiveness trend line.

The employment of aircraft for surveying has become so usual, and so much has been written about it from one aspect or another, that perhaps the time is appropriate to define exactly what is meant by Air Survey; what the surveyor is trying to achieve, and how he is dependent upon the airman to obtain his objectives. To achieve good results from an air survey, closely integrated team work is required. The airman, photographer, instrument specialist, meteorologist and the surveyor each depend upon the other, any weakness in the chain making results more expensive and less effective. The author, as a surveyor, has worked in harmony for a good many years with the “air” side, and it is proposed in this paper to summarise the surveyor's approach and his requirements, and to explain why he seems never to be satisfied with the accuracy achieved. The greater the accuracy of photography, the simpler, quicker and cheaper become methods of using the results to fulfil the desired specification.

The 882nd Lecture to be given before the Royal Aeronautical Society was held under the auspices of the Glasgow Branch on 23rd April 1953. Professor W. J. Duncan, F.R.S., F.R.Ae.S., President of the Glasgow Branch, welcomed the visitors. He expressed regret that the President of the Society, Mr. G. H. Dowty, F.R.Ae.S., was unable to be present and welcomed Mr. N. E. Rowe, C.B.E., F.R.Ae.S., Chairman of the Branches Committee, and the Secretary of the Society, Dr. A. M. Ballantyne, T.D., A.F.R.Ae.S.

Mr. Rowe, taking the Chair for the rest of the meeting, said how much the President regretted not being present; as they knew, he had shown the liveliest interest in the Branches and had made many visits to them during his year of office. This was the twelfth Main Society Lecture to be given at a Branch meeting; the holding of Main Lectures at the Branches had proved a great success and he was sure that the present meeting would be a success also, because their lecturer had been doing pioneering work for the past three years on the development of the Comet. After graduating from Cambridge in 1940 Captain Majendie joined the R.A.F. and served as an instructor for several years; he served with Coastal Command in 1943 and was mentioned in despatches, then served on ferry duties, and in 1946 joined British Overseas Airways. He held a Pilot's “B” Licence, a Navigator's Licence and a Wireless Operator's Licence. Before being appointed to work on the Comet he had been engaged in helping Mr. E. S. Calvert at the Royal Aircraft Establishment to develop the high intensity lighting system. Captain Majendie was one of those rare people who combined a scientific and a really practical ability.

In the vibration of isotropic rectangular plates, the phenomenon of the simultaneous excitation of two separate modes having equal frequencies is well known. Wallerobserved complex nodal patterns on isotropic rectangular plates, and she stated that such combinations were possible because of the internal damping of the plates, which reduced the sharpness of resonance.

Warburton considered the existence of modes m/n±n/m for a clamped plate and showed that when a plate is square, for the mode 4/2 + 2/4, the nodal lines do not lie parallel to the edges of the plate. Furthermore, it was proved that for a square clamped plate, the modes m/n±n/m have discrete frequencies.

The problem of fracture characterisation of geometrically complex structures is considered. Numerical and experimental strategies are used to evaluate stress intensity factors and elastic fields for cracked thin shell and plate structures. Theoretical analyses, using different order theories, are also performed in order to evaluate stress and energy distributions in the neighbourhood of the crack tip. A geometrically complex strut component is analysed by using a ‘p-convergent’ finite element code based on hierarchic elements and on the high degree of approximating functions. Actual fracture modes, for different crack locations, have been singled out and the elastic fields are compared to those referring to cracked plate and shell structures. An experimental investigation, using the optical method of caustics, has been also performed and stress intensity factors for several crack configurations have been calculated. The numerical investigations have shown the ability of the p-version finite element method to provide accurate computation of local stress values and to quote the convergence of the numerical calculations. The caustics method has confirmed its accuracy for evaluating stress intensity factors, even for complex structures.

The equations showing how to correct for the effect of non-uniformity of the Atmosphere when computing the angle-of-climb (or descent) are well known and can be found in Refs. 1 and 2.

From Ref. 1, a climb at constant Mach number M implies a factor F on the Aircraft Weight to give the true angle-of-climbs (in our units for R) given by the expression

I t is perhaps unfortunate, from the point of view of aviators, that the extinct flying reptiles known as “pterodactyls” or “pterosauria” no longer exist. There can be no doubt, that in the case of the more highly evolved members of the group the organisation was more specialised for flight than that of any other animal of which we have knowledge. Other flying animals can walk, run, or swim, besides fly. But in the case of the higher pterodactyls their structure is such that it is difficult to understand how they can have had any other means of progression than flying. With a body little larger than that of a cat they had a span of wing asserted in some cases to have reached 21 feet or more.

The problem of aircraft noise has been touched on by a number of today's speakers, but I wonder how much it is appreciated that probably the biggest single interface problem before the aviation industry today is that of environmental pollution.

The dilemma which every Minister responsible for civil aviation has to face is how to strike a right balance between, on the one hand, economic and operational considerations and, on the other, the protection of the public from excessive noise. Successive Ministers have indicated very clearly to the Department that they favoured paying a substantial price, if required, for the preservation of amenity.

There is at present no thoroughly satisfactory method of measuring accurately the true air speed of an aircraft, particularly at high speeds.

Ground radar can accurately follow a high-speed aircraft but, without the development described here, can only measure the speed of the aircraft relative to the ground. The method developed by the authors makes immediate allowance for wind speed and is capable of giving the true air speed of an aircraft to within one per cent. There is no apparent reason why the method should not be applicable even at very high speeds and there is no limit in aircraft altitude at which the measurement may be made.

You can pick up almost any history of aviation—from the early times to the present—and read of the exploits and adventures of pilots and their planes. Sir Charles Kingsford-Smith and his Fokker, Charles Lindbergh and his Ryan, Amelia Earhart and her Lockheed. We who have technical interests in aviation know that Kingsford- Smith and Lindbergh depended on their Whirlwinds, and Miss Earhart on a Wasp, but the popular stories often fail to make that point.

In more modern times, the engines are equally vital but sometimes get overlooked. Once, when a new jet aircraft was being announced at a press briefing, an airline officer breathlessly described the aircraft, showed artists’ concepts of the cabin and flight deck, and talked at length of the systems and subsystems. After an hour-long description, he called on his audience of reporters, and then he got his come-uppance from an engine man’s point of view. A reporter at the back of the room was recognised, and asked: ‘And what is this aircraft going to be? A glider?’ The by now red-faced official had neglected to mention the powerplants.

An unstructured flow solver with adaptive mesh refinement and multigrid acceleration is developed to efficiently compute two-dimensional inviscid and viscous steady flows about complex configurations. High resolution is achieved by using the upwind scheme coupled with adaptive mesh refinement. An aspect-ratio adaptive multigrid method is developed and applied to effectively accelerate the solution convergence of the explicit time-marching in the near wall regions with high aspect mesh ratios. Numerical examples are presented for configurations and conditions ranging from transonic to low speed flows to demonstrate accuracy, speed, and robustness of the method.

The rate of progress in most technical fields, and propulsion is no exception, has increased so rapidly during the past 50 years that it is becoming difficult to predict the trend of development for more than a few years ahead. On the other hand, there are fundamental limits to progress in certain directions and it is within these limits that this paper is written. One must, of course, devote some thought to the validity of the limit. Not so long ago it was thought that the speed of sound would be a limiting speed for aircraft, for instance. One cannot go far wrong with the basic laws of physics and the intention, at least, of this paper is not to transgress such laws.