In moving from the realm of stationary wing flight towards the complexity of flapping wing flight as evolved in birds, we wish to introduce the simplest means of flapping as a first step in an attempt to simplify as much as possible our wind tunnel model and also to confine our attention to the dominant thrust producing mechanism. Our model half wings flap only in the plane normal to flight. The flapping motion is sinusoidal with time and symmetrical about the mid position (Fig. 6). No wing bending was allowed. The wing section shape had no camber and also was rigid in shape but free to twist in torsion about its shear centre. However, the model root support was fixed and therefore could not simulate vertical plunging of a bird associated with ideal elliptic span loading (Ref. 1).

In Ref. 1, an exact theoretical analysis is given for the buckling of sandwich columns in compression. The theory is able to predict both overall buckling and face wrinkling and the present paper extends this work by suggesting a design procedure for obtaining least column weight for a given end load and column length. It is shown how a family of optimum design curves can be obtained for given material properties, which encompass all of the geometrical parameters excepting column width. For a given end load, least weight is obtained with least width, but the limiting factor then becomes one of overall instability in the transverse direction of the column. The columns are not optimum in the sense that the buckling and compressive failure loads are made to occur at the same time. Generally speaking, it is not possible to design to this condition for given core and face plate materials and there is found to be a large margin of safety between the buckling stresses and the ultimate failure stresses.

This paper considers the conversion training of qualified engineers employed in flight simulation from the background of experience in British Airways. The title is taken to mean the conversion of engineers qualified to appropriate standards, with experience in their chosen area which is demonstrated to be generally some form of electronics, to full skill level in flight simulation.

The rate of change in flight simulation is very fast. Training should keep up with these changes, but it is often hard-pressed to do so for reasons explained subsequently.

I would like first of all to explain the philosophy of our operation with an eye to the future for we are in a transitional stage at present. Our primary effort is a maintenance task where the 17 flight simulators will be divided into three groups. These groups will contain six analogue simulators and eight digital simulators currently in house, with three further simulators on order or about to be (Fig. 1). Not shown in Fig. 1 is a support group providing specialist service as required.

Axial, normal (radial) and tangential turbulence intensity measurements have been carried out in the past in pipe and two-dimensional channel flows, e.g. Refs. 1-9. A similarity in the distribution of these turbulence intensities is observed. They are all minimum at the centreline, increasing steadily as the wall is approached, until they reach some maximum values close to the wall, then they start to decrease as the wall is approached further. Furthermore, the three components of turbulence intensity have been observed to vary in a similar way with the Reynolds number.

On the other hand, the Prandtl mixing length theory assumes that the turbulent fluctuations are proportional to the product of a local mixing length and a velocity gradient. This implies that the turbulence fluctuations are directly proportional to each other. It is, therefore, found worthwhile examining the possibility of a relationship between the turbulence intensities. Smooth pipe and channel flows are chosen for this purpose.

Largely as a result of frequent written reports by Pierre Des Noyers, secretary to the Queen of Poland, mid-seventeenth century scientists took a great deal of interest in the aeronautical work of an Italian engineer, Tito Livio Burattini. Born in Agordo, north of Venice, on 8th March 1617, Burattini early became a travelling scholar. By 1637 he had reached Egypt, where he helped John Greaves with his famous work on the pyramids. Despite his youth, he appears greatly to have impressed Greaves, who referred to him, with slight inaccuracy, as ‘Titus Livius Burretinus, a Venetian, an ingenious young man'. In 1641 Burattini returned to Europe, spending a little time in Germany and travelling on to Poland, where he lived until 1645. In 1647, after a visit to his native Italy and a second period in Egypt, he settled permanently in Poland, where he attempted, soon after his arrival, to establish himself at the court of Wladislaw IV (30th May 1595-20th May 1648).

What do we mean by reliability? Mathematically, it is the probability that a piece of equipment will be capable of working when called upon to do so for the time required and under the environment specified, and, if we know the mean time between failures and make certain assumptions about the randomness of the failures, we can derive expressions that will give numerical values of inherent reliability.

In layman's terms, we can say that it is the ability of a piece of equipment, whether it be a small component or a complete aircraft, to be ready to work and to continue to work in the environment for which it has been designed, for as long as the specification requires it to do so and to do this with the minimum amount of maintenance.

A method of improving the flow angle and Mach number distribution of a flexible-plate supersonic wind tunnel by small movements of the top and bottom liners has been known for a number of years. Once the influence on the flow, at a given Mach number, of small displacements of jacks supporting the liners are known, jack movements can be used to reduce non-uniformities in the working section flow. Such a procedure is being studied for adjusting the flow in the 8 ft x 8 ft Supersonic Wind Tunnel at RAE Bedford. However, one of the main difficulties encountered has been that of accurately determining the influence of each jack. The extended rippling in the plate which results from a displacement of a single jack generates a Mach number disturbance which is difficult to trace. This is particularly true at lower Mach numbers (i.e. near M=l.4) where the reflection of the disturbance from the opposite wall is observed to combine with the ‘tail’ of the direct effect, thereby causing interference effects in the data. Even with a 9-tube pitot rake spanning the tunnel it is difficult to ascertain which part of the disturbance is coming from the top of the tunnel and which part from the bottom. Ways have therefore been considered of moving the plate in the region of a particular jack in such a manner that the resulting waveform is shorter and more readily traced. A simple but effective system of jack movement has been derived and is described here as the 1-4-1 system.

The buckling coefficient for a conventional shear web, reinforced by a series of equally-spaced transverse stiffeners, is practically independent of the flexural rigidity of the stiffeners provided this exceeds a certain critical value. The stiffeners then provide conditions close to simple-support (if they are of negligible torsional stiffness). For stiffeners of less than this critical rigidity, reduced buckling coefficients are plotted in Ref. 1, in terms of a stiffness parameter μ related to the second moment of area of the stiffeners. Reference 1 also shows that the critical value μc referred to above increases rapidly with reducing stiffener pitch, leading in some cases to impractically large stiffeners.

There is a growing interest in the analysis and design of waffle cylinders because of the advantages of integrally stiffened shell wall construction. The usual approach to the stability analysis of a stiffened shell has been to replace it by an equivalent orthotropic shell. The eccentricity of the stiffener has a large effect on the critical load in cylindrical shells, and outside stiffening has been found to be stronger than inside stiffening. Inversion of the stiffener eccentricity effect has been observed in cylinders under hydrostatic pressure loading. Naturally, regardless of whether the stiffened cylinder is considered as an orthotropic continuum or a composite of discrete elements, the treatment cannot be complete if it fails to include the coupling between bending and extensional forces and deformations resulting from one-sidedness of the stiffeners.

Vortices are of interest in many situations in fluid mechanics. One type of vortex with which the gas turbine designer is concerned is the line vortex springing like a miniature tornado from a point on the ground (or from a nearby aircraft surface) and entering the engine intake. It is possible for these vortices to suck stones up into the engine (Refs. 1, 2) and also to reduce the compressor surge margin (Refs. 3, 4). They are unsteady, in that their point of origin wanders about and so does their point of entry into the intake. This unsteadiness makes it very difficult to measure them, and so far no one known to the author has reported measurements of ground vortex strength, in the course of several investigations of the phenomenon (Refs. 1-3, 5-8).

Passenger traffic through the seven BAA airports, Heathrow, Gatwick and Stansted in the South-East and Glasgow, Edinburgh, Prestwick and Aberdeen in Scotland is predominantly in the leisure sector and this sector is most affected by low fares. In 1978 this sector formed 65% of all traffic at the three South-East airports and 55% at the four airports in Scotland.

As Ray Colegate and Adam Thomson have said low fares are no new choice for air travellers. Low fares for charter operations with a range of fare options have been the main feature of the rapid passenger growth at Gatwick Airport for many years. This is also the case at Luton Airport which is not owned by the BAA but serves the South-East.

The knowledge about the position of the detached shock and the aerodynamic forces acting upon a booster front during upper stage (sustainer) jet impingement on a separated booster is needed in connection with the problem of stage separation in the atmosphere for a multistage launch vehicle. The jet flow is squeezed in by the free-stream and characterised by a non-uniform transverse variation of flow properties. The flow field analysis of a trailing blunt body in such a non-uniform flow has been limited to experimental studies only. Most of the prior analytical treatments were restricted to the study of the effect of free-stream non-uniformities such as source flow and wake-like free-stream velocities on blunt bodies. A somewhat related problem of supersonic, underexpanded jet impingement upon an infinite flat plate in the absence of external stream has been studied by Belov et al and Gummer and Hunt.

It has long been suspected that the inner portion of any turbulent boundary layer velocity profile obeys a so-called law of the wall which takes the form:

where u is the boundary layer velocity at a distance y from the wall, uτ is the friction velocity given by √(τw/ρ) in which τw is the wall shearing stress and ρ is the fluid density, v is the kinematic viscosity and A and B are constants.

When British Aerospace, Brough, were first tasked with carrying out a study of mechanical systems and component reliability it was anticipated that the installed environment would be a significant parameter in the investigation. Consequently it was decided to carry out a separate study of the environment of equipment on a number of aircraft to assess how this had influenced the design and subsequent reliability of the components and to see if the initial assumptions had been valid. This study was to make use of measured data from routine development flying as well as tropical and cold weather trials. In addition the reliability of appropriate equipment was reviewed to determine the incidence of problems arising from environmental factors.

The installed environment can be broken down badly into two separate factors. Firstly, those which are external to the components in question, e.g. altitude, ambient temperature, humidity, vibration levels, solar radiation and contaminants such as salt, sand and dust. Secondly, there are those factors which are internal to the component in question or are influenced by the installation of the component in a larger system. These factors include internal pressures, temperatures and contaminants, the effect of the system flows and interaction with other components.

A serious disadvantage of using a lattice of vortex rings to model a surface of vorticity, is that points close to the lattice surface may see large ‘holes’ in what from a larger distance appears as a smooth vorticity distribution. This failing is particularly important when two surfaces approach each other, such as occurs at the trailing edge of a wing, or when a free vortex passes near to a solid boundary. In these cases the error in induced velocity can adversely affect the overall flow computation. A relaxation process to find the force-free position of a free vortex close to a surface would obviously fail, for example. The obvious way of overcoming this problem is to improve the accuracy of the vorticity model whenever a point draws critically near to the vortex lattice.

Maskew suggested a way of overcoming this problem in two dimensions and his ideas have been extended in this note to three dimensions.