An improved method, based on one strip approximation of the method of integral relations which was reported originally by Belov, Ginzburg and Shub, is presented for the calculation of flow parameters in the impingement region of a supersonic, underexpanded jet striking a normal surface located within the first cell. The results are presented for two impingement conditions and found to be in good agreement with the experimental data.

Ladies and Gentlemen,

It is my privilege to introduce to you today MR FITZWILLIAMS, whose subject is “Some work with Rotating Wing Aircraft”

MR FITZWILLIAMS is a founder member of the Helicopter Association and a member of our Council and has been engaged on various aspects of rotating wing development over the past nine years, first with Mr PULLIN at Messrs G & J Weir Ltd, and later with Mr HAFNER at the Ministry of Supply He is now Helicopter Engineer of the Westland Aircraft Company

During the latter part of his time with the Ministry he was in charge of the rotating wing section of the Airborne Forces Experimental Establishment at Beaulieu I understand that this period supplies the bulk of the material for his talk and I feel sure we shall find it both interesting and entertaining

On behalf of the Association I extend a cordial welcome to our guests

The need for efficient propulsion systems allied to increasingly more challenging fixed-wing UAV mission requirements has led to recent research on the autonomous thermal soaring field with promising results. As part of that effort, the feasibility and advantages of model predictive control (MPC)-based guidance and control algorithms capable of extracting energy from natural occurring updrafts have already been demonstrated numerically. However, given the nature of the dominant atmospheric phenomena and the amplitude of the required manoeuvres, a non-linear optimal control problem results. Depending on the adopted prediction horizon length, it may be of large order, leading to implementation and real-time operation difficulties. Knowing that, an alternative MPC-based autonomous thermal soaring controller is presented herein. It is designed to yield a simple and small non-linear programming problem to be solved online. In order to accomplish that, linear prediction schemes are employed to impose the differential constraints, thus no extra variables are added to the problem and only linear bound restrictions result. For capturing the governing non-linear effects during the climb phase, a simplified representation of the aircraft kinematics with quasi-steady corrections is used by the controller internal model. Flight simulation results using a 3 degree-of-freedom model subjected to a randomly generated time varying thermal environment show that the aircraft is able to locate and exploit updrafts, suggesting that the proposed algorithm is a feasible MPC strategy to be employed in a practical application.

A study of engineering problems encountered in the design of transparencies for supersonic aircraft is presented with a special emphasis on the effects of kinetic heating. The paper is written primarily with optical transparencies in mind but many of the general principles discussed are equally applicable to the design of radomes for elevated temperature applications.

The first parts of the paper consider briefly the methods of calculating temperature distribution in transparent panels subjected to kinetic heating (or cooling) and this leads naturally to discussion of the effects of the non-uniform temperature distribution, differential expansion and the edge restraints preventing thermal deformations. Methods of calculating thermal stresses are suggested through the concept of the “ self-equilibrating ” temperature distribution; the main attention, however, being concentrated on the derivation of simple engineering formulae rather than on the mathematical rigour of the solution.

The choice of design cases for combined pressure and thermal loading is considered and it is shown that, in general, deceleration manoeuvres combined with outward pressure constitute the design criteria for transparencies. The effects of various parameters on the magnitude of thermal stresses are analysed; these include the effects of altitude, temperature, deceleration and material properties. It is shown that, for given material and panel geometry, the thermal stresses depend mainly on the following parameters: total temperature change, acceleration (or deceleration), and the Biot number based on the panel thickness.

Practical design aspects are also considered, such as choice of materials, strength, panel geometry, mounting of panels and the fail-safe design. Finally, testing of transparencies under pressure and thermal loading is briefly discussed, together with possible methods of strain measurements, and a tentative proving procedure for transparencies is suggested.

The friction force in many physical systems has been found to depend on a power of the velocity, the magnitude of which varies according to the damping mechanism. This note employs an approximate theory applicable to small damping to examine the free vibration of a single degree of freedom system in which the damping force is proportional to an unspecified power of the velocity.

Correlation with experimental data on the internal damping of solid materials shows that this phenomenon also tends to obey a power law although discrepancies exist between the expected and observed behaviours. These arise from the interpretation of the damping coefficient and from the frequency dependence of the dissipated energy.

Comprehensive understanding of propulsive jet aerodynamics and aeroacoustics is key to engine design for reduced jet noise and infra-red signature in civil and military aerospace, respectively. Illustrated examples are provided of other aerodynamic/aeroacoustic problems involving jet development, including chevron nozzles, increased jet/wing/flap interference (as fan diameter increases), high acoustic environment (and potentially damaging screech) of supersonic jets on carrier decks and the strongly Three-Dimensional (3D) unsteady flow during the in-ground effect operation of Short Take-Off and Vertical Landing (STOVL) aircraft. To date, laboratory/rig test measurements have primarily been used to identify design solutions; increased use of Computational Fluid Dynamics (CFD) would help achieve cost/time reductions, but Reynolds-Average Navier–Stokes (RANS) CFD with statistical turbulence modelling has proven inadequate for such flows. The scenarios described are far removed from flows used to calibrate model constants, and predictive accuracy demands detailed insight into unsteady flow. Large-Eddy Simulation (LES), whilst computationally more demanding, offers a potential solution. Research undertaken to assess LES capability to address the challenges described is reviewed here. This demonstrates that tremendous progress has been made, indicating that LES can provide sufficiently accurate predictions, representing high value for engineering design. A series of validation studies of increasing realism to practical engineering systems is presented to underpin this conclusion. Finally, areas for further work are suggested to support the combined application of RANS and LES that is probably the optimum way forward.

This paper presents a performance analysis on a novel engine concept, currently under development, in order to achieve hybrid air-breathing rocket technology. A component-level approach has been developed to simulate the performance of the engine at Mach 5, and the thermodynamic interaction of the different working fluids has been analysed. The bypass ramjet duct has also been included in the model. This facilitates the improved evaluation of performance parameters. The impact of ram drag induced by the intake of the engine has also been demonstrated. The whole model is introduced into a multi-platform application for aeroengine simulation to make it accessible to the interested reader. Results show that the bypass duct modelling increases the overall efficiency by approximately 7%. The model calculates the specific impulse at approximately 1800 seconds, which is 4 times higher than any chemical rocket.

Nobody would deny that a major objective of the peoples of the world is to improve standards of health and hygiene and an essential part of this must be to increase the quantity of food produced. To do this it is essential to use supplementary nutrients and exercise effective pest management. It has been shown that the yields of basic foods, such as rice, can be doubled by using the right seed strains, fertilisers and crop protection techniques. Crop yield losses because of insects alone are estimated at 5% in Europe where insecticides are used widely and as much as 21% in Asia where insecticides are used only in a few of the better organised cultural areas.

A theory of primary failure of compression panels of integral construction with unflanged stiffeners is presented, involving rotation, or translation, or rotation and translation of the stiffeners with the corresponding distortion of the sheet without deformation of the cross sections in their own planes. The investigation shows that the failure may occur generally either by pure torsion of the stiffener with the associated lateral distortion of the sheet or by pure flexure in accordance with whichever mode yields a smaller stress. The theory is compared with the test results covering a fairly wide range of the dimensions involved. The theory is in complete agreement with the experiments. The accuracy of the result thus obtained indicates that the fillets at the junction of the skin and the stiffener are not important and their effects may safely be disregarded.

The work to be described was planned as the first stage of an investigation of the effects of streamwise vortices on base pressure. An axi-symmetric blunt-based body was used, consisting of a cylindrical portion with a semiellipsoidal nose. The intention was to mount strakes or semi-delta wings at incidence on the sides of the body to produce vortices and to measure the effects of these on the base pressure. The base of the body was fitted with 37 pressure tappings so that local variations of base pressure could be explored. It was found that for the body at zero incidence and yaw, without any strakes or wings, there was great difficulty in obtaining an axi-symmetric distribution of pressure on the base.

A re-cooled cycle has been proposed for a regeneratively cooled scramjet to reduce the hydrogen fuel flow for cooling. Upon the completion of the first cooling, fuel can be used for secondary cooling by transferring the enthalpy from fuel to work. Fuel heat sink (cooling capacity) is thus repeatedly used and fuel heat sink is indirectly increased. Instead of carrying excess fuel for cooling or seeking for any new coolant, the cooling fuel flow is reduced, and fuel onboard is adequate to satisfy the cooling requirement for the whole hypersonic vehicle. A performance model considering flow and heat transfer is build. A model sensitivity study of inlet temperature and pressure reveals that, for given exterior heating condition and cooling panel size, fuel heat sink can be obviously increased at moderate inlet temperature and pressure. Simultaneously the low-temperature heat transfer deterioration and Mach number constrains can also be avoided.

It is now the usual practice in Great Britain to estimate the “ safe ” life of an aircraft wing from fatigue tests which are carried out on specimens representing the more highly stressed portions of the tension boom or booms. Such tests are designed to produce a tensile load in the boom equal to that produced in steady flight, and superimposed on this, a small fluctuating load corresponding to that which would be produced by an up gust immediately followed by a down gust of the same magnitude.

This Convention poses a challenge to the lecturers. It asks us to gaze into a crystal ball and to forecast the future on the basis of the research of today. My contribution is to review the aerodynamics scene. I am the first specialist lecturer; this is perhaps a recognition that many of the significant advances of the past have been aerodynamically inspired. It is natural to start by thinking back 20 years and asking whether we would then have predicted what has come true today. In aerodynamics, there is obviously a clear answer to this question.

— A great deal of publicity has been given in recent years to the problems caused by microbiological attack on aviation fuels, although there had been considerable experience of the subject before the first serious problems arose in aviation. Intensive studies of the nature of the attack have shown that although limited use of biocides has been successful, the best control is by the elimination of stagnant water from the fuel supply system and the aircraft fuel system.

The results of an investigation into the effects that sub-boundary layer vortex generators (SBVGs) have on reducing normal shock-induced turbulent boundary-layer separation are presented. The freestream Mach number and Reynolds number were M = 1·45 and 15·9 × 106/m, respectively. Total pressure profiles, static pressure distributions, surface total pressure distributions, oil flow visualisation and Schlieren photographs were used in the results analysis. The effects of SBVG height, lateral spacing and location upstream of the shock were investigated. A novel curved shape SBVG was also evaluated and comparisons against the conventional flat vane type were made. The results show that in all but two cases, separation was completely eliminated. As expected, the largest SBVGs with height, h = 55%δ, provided the greatest pressure recovery and maximum mixing. However, the shock pressure rise was highest for this case. The experiments showed that the mid height SBVG array with the largest spacing provided similar results to the SBVG array with the largest height. Reducing the distance to shock to 10δ upstream also showed some improvement over the SBVG position of 18δ upstream. It was suggested that total elimination of the separated region may not be required to achieve a balance of improved static pressure recovery whilst minimising the pressure rise through the shock. The effect of curving the SBVGs provided an improved near wall mixing with an improved static and surface total pressure recovery downstream of the separation line. The optimum SBVG for the current flow conditions was found to be the curved vanes of h = 40%δ, with the largest spacing, located at 18δ upstream of the shock. Overall, it was apparent from the results that in comparison to larger vortex generators with a height comparable to δ, for SBVGs the parameters involved become more important in order to obtain the highest degree of mixing from a given SBVG configuration.

The past ten years have seen a wide variety of axial gas turbine aero-engines pass through their development phase into military service. A new phase began when the first axial gas turbine engines to operate to a civil schedule entered service in 1956-7, powering the Britannia and Tu.104 aircraft. The coming years will see an ever-increasing percentage of the world’s air traffic being carried by axial gas turbine engines and it may be confidently predicted that in another ten years they will be the rule rather than the exception.

The enormous importance of reliability in civil operation is well known. Possibly less well known is the incredibly rapid build-up of running hours which occurs when an engine is introduced into civil operation. In six months of civil operation these may exceed the cumulative hours in the whole life of a military type, and will outstrip the total manufacturers’ bench experience in an even shorter time. With all the achievements in bench development and military service in the past ten years, the axial gas turbine engine is still in the “ kindergarten ” in relation to civil operation.

The large displacement analysis of shells of arbitrary form is rightly considered to be a formidable undertaking. A purely analytical approach to the solution of such problems involving also initial buckling, post-buckling and secondary instability or snap-through is at the present state of knowledge impossible. However, with the advent of the matrix displacement method initiated in 1954 it became increasingly apparent that this method would prove in time the ideal tool for the solution of such complex structural phenomena. Nevertheless, all efforts in this direction were bedevilled until recently by the lack of suitable elements, satisfying all kinematic compatibility conditions. The major breakthrough came in this direction through the invention of the triangular shell element SHEBA, which admits an arbitrary variation of curvature. This again evolved from a natural extension of the plate element TUBA of TN 14. At the same time the SHEBA theory of ref. 1 was restricted to small displacements or linear behaviour. To generalise it to large displacements was not possible without an additional major conceptual progress. This was achieved within the Technical Notes 17 to 20, which introduced the idea of a local sub-element and showed how its geometrical stiffness could be used to deduce the geometrical stiffness of the complete element by a physically evident argument. The attentive reader will have noticed that the sub-element of an arbitrary beam in space discussed in ref. 3 is the obvious component block for our shell element. As a matter of fact, the technique is simply based on the representation of the SHEBA element by a grid of beam sub-elements running along the natural α, β, γ directions.

In recent years it has grown customary for aircraft firms to put increasing effort into the prediction of flutter during the design stage. This design work, however, is chiefly related to wing flutter in which the control surfaces play little part, whereas the cases of flutter which most commonly occur in reality are those involving control surfaces. The reason for this is that the wing stiffness, and hence the wing weight, is often determined by considerations of main surface flutter. Control surface flutter, however, can often be prevented by methods which do not have a serious effect on the aircraft weight and which are often postponed until after the design stage. This paper will discuss what steps can be taken, both in the design stage and during the flight testing of a prototype, to prevent control surface flutter.

There is not a great need for the further reductions in flight time that can be afforded by the SST over the near-sonic jets. Furthermore, the time gain by the SST will be counteracted by reduced in-flight comfort and, on the average, by an increasing difference in airport distance between supersonic and competing subsonic services. Nevertheless, most businessmen in a great hurry and some tourists are likely to prefer the SST on conveniently scheduled flights and at equal fares.

However, for utilisation reasons only some of the SST flights can be conveniently scheduled and the SST's will—for 15 specified reasons—be so grossly uneconomical in competition with subsonic aircraft that the condition of equal fares cannot be complied with without exceedingly high subsidies to be covered by the taxpayers in all SST-operating countries. The subsidies must continuously increase mainly because of

—improvements of competing subsonic aircraft in operating cost—and ability to use more centrally located airports and

—increasingly adverse sonic-boom reactions (as the operation grows and the SST's, as is normal, become heavier and create higher boom intensities) by people on the ground, including potential SST passengers.

As the SST enterprise will thus be an economic failure, most of the aspects that are claimed to be advantageous in the event of an SST success, in particular prestige and improved national economy, will instead turn into pronounced disadvantages: loss in prestige and an economical burden.

Over and above this, supersonic aviation will

—most likely be much less safe than subsonic aviation,

—possibly subject passenger and crew members or their off-spring to harmful effects of cosmic radiation,

—seriously counteract, probably make impossible, the urgently needed improvement of flight safety in aviation,

—hamper the brilliant prospects now in sight for making aviation a really cheap and convenient means of mass transportation, and

—retard the expansion of civil aviation.

People in general are prepared to put up with a certain amount of noise—in confined areas and mainly during the working hours of the weekdays—if it is an inevitable by-product of a necessary, an important, or a profitable activity. But supersonic aviation, which will cause serious noise disturbances day and night, 365 days of the year, in unprecedently vast areas, is neither necessary, nor very important, nor profitable. Thus, the introduction of supersonic flight would mean that hundreds of millions of people would not only be seriously disturbed by the sonic booms, often to an extent detrimental to health, but also have to pay out their own money to keep the noise-creating activity alive, and in addition, have to accept a much less safe and cheap civil aviation than would otherwise be possible to achieve.

Therefore, the consequences are such that, once the supersonic era has begun, the general public will always strenuously oppose it. There will be an unprecedented tension between aviation and the public. Intense efforts will certainly be made to switch back to all-subsonic aviation. The cost of such a reversion will be fantastic and rapidly grow the longer the supersonic era prevails.

Obviously, it lies in the best interest also of civil aviation to prevent introduction of supersonic flight in its presently suggested form.

More than two years ago Pollard in a paper given to the Society made out the case for the use of fibre-reinforced plastics in the structural field. He and others have shown that materials based on strong, inert fibres, such as glass or asbestos, have mechanical properties which, when stabilised by suitable resins, permit them to function with a high degree of efficiency within certain well defined parameters of loading.

Four distinct groups of resin are used in combination with such fibres, phenolic, polyester, epoxide and silicone. With the present exception of silicone resins, each can be used at low or even contact pressures during moulding and thus do not impose serious processing limitation upon the size, quantity or complexity of the structures which can be contemplated.