When I was invited to deliver this paper it was suggested that I should adopt the title “Standards and Objectives for Air Safety”. I welcomed this idea because I think that now is an appropriate time to review our approach to air safety and I would like to discuss some of the modern developments in standards. On reflection, however, I felt that I should really make a small change to the title to put the objectives before the standards and I hope my hosts will forgive me for taking this liberty. I must confess that there have been many cases where the standards got written first and the objectives were worked out afterwards. But I would like to treat them here in the order in which I think they should appear.

I have been concerned for much of my working life with that part of safety called “airworthiness” but, as you probably know, it has been proposed that the ARB should now become part of a very much larger bureaucracy and so I hope my future colleagues will forgive me if I anticipate the merger with them and deal with safety in a rather broader sense.

A number of theoretical methods concerning the flow about jet flapped wings have been developed for predicting the increase of lift due to super-circulation around an aerofoil, but only a few of those methods have been concerned with a jet flapped wing with ground effect.

The main purpose of this paper is to introduce a simple approximate representation of the flow around a jet flapped aerofoil in the case when the jet hits the ground. Hence, it is assumed that the existence of a stationary vortex is neglected and the wake fully develops from the leading edge. It is also assumed that the jet is replaced with a suitable distribution of sinks along the jet axis, to represent the effect of jet entrainment. When the aerofoil is in very close proximity to the ground, it may be assumed that the jet impinges on the ground before the mixing layer finally emerges in the centre of the jet.

Figure 1 is a sketch of an “aerodynamic seal”. This type seal has potential application where it is necessary to control leakage of fluid through a clearance space bounded by one moving wall. For mechanical reasons it is necessary to maintain a clearance, in this case equal to the throat width t, between the inner wall I and the outer wall O. To prevent flow from the high pressure chamber H from passing into the low pressure chamber L, pump P supercharges fluid from H and forces it through nozzle J. The resulting fluid jet, which may be aided in following the curved surface by the Coanda effect, passes through the throat t and into diffuser D which recovers part of the entering velocity head. In the ideal case, with no losses and one-dimensional flow, the per cent recovery of inlet velocity head may be made as near to 100% as desired, since the diffuser recovery coefficient becomes asymptotic to 1-0 with increasing area ratio. Conversely, the dumping loss may be made as near to zero as desired. The attractiveness of this proposal hinges on diffuser performance. The pump is necessary to make up for the velocity head lost at the diffuser exit and for flow losses in the system. The pressure at the diffuser throat should be approximately that of the low pressure chamber for optimum performance. For large pressure ratios it may be necessary to stage two or more seals in series.

The problem of cut-outs in structures being analysed by the matrix force method is solved by Goodey by the method of undetermined multipliers. It can be shown that the final results are identical to those of ref. 2. In this note we demonstrate that the method of undetermined multipliers can also be used to incorporate modifications into a structure. This, in itself, is only of academic interest for a simple problem. However, it does give many advantages when dealing with more complex situations. The basic equations can be written down quite simply and the development of the subsequent matrix algebra follows the straightforward pattern for solving simultaneous equations. Also, where previous results can be used, this becomes apparent.

A great deal of research effort is going into the measurement of turbulent air velocities in relation to aircraft flight. There is a continuing need to review our knowledge of aircraft responses to air turbulence in order to appreciate the significance of the new information as it becomes available and in order to demonstrate which parameters in the problem are of most importance and therefore deserving of the closest study.

At the present stage of aircraft development we can see dramatic changes in aircraft speed, size and shape. Increased aircraft size, speed and height of operation imply larger values of the gust mass parameter μg than hitherto; they also mean that structural flexibility is becoming increasingly significant. Change of shape towards the slender configuration involves us not only in new appraisals of aircraft aerodynamics, steady and unsteady, but also in different modes of structural distortion from those typical of current subsonic turbojet transport aircraft.

The problem of maintaining a satellite in a fixed orientation relative to the earth has led to the investigation of several methods of attitude control. In particular, the one involving passive stabilisation using gravity-gradient torque has aroused considerable interest. However, a major limitation of this manner of stabilisation is its inability to achieve station keeping to a high degree of accuracy. Furthermore, some form of external damping is necessary to recover an equilibrium configuration in a reasonably short period of time. Modi and Brereton investigated the energy dissipating mechanism which was an extension of the model proposed by Paul The numerical analysis of the system with small damper mass showed limit cycles associated with the system to be identical with one of the periodic solutions of the undamped case.

Research is in progress to assess, and if possible improve, the accuracy of a widely-used method for calculating the pressure distribution on swept wings in subsonic attached (inviscid) flow. Ref. 1 does not make specific recommendations on how to deal with wings having “cranked” planforms (i.e. wings with discontinuous changes in the sweep angle of the leading or trailing edges, other than at the central “kink” fundamental to the swept wing concept); but it implies (section 8.3) that the method of ref. 2 could be used for this purpose. A re-examination of this problem, in connection with the programme of work of the Transonic Aerodynamics Committee of the Royal Aeronautical Society, has revealed errors, which could be seriously misleading, in that part of ref. 2 dealing with the thickness effect. The object of the present note is to present the corrected formulae for the basic streamwise and span-wise components of perturbation velocity due to the thickness, at and near the crank, in the simplified example consisting of two semi-infinite wing panels of different sweep angles joined together; to examine the possible singularities in the flow field in the neighbourhood of the crank; and finally to discuss qualitatively the implications of these formulae on the magnitude of the “crank effect”, including the influence of free-stream Mach number.

The elastic modulus of a honeycomb sandwich core under transverse compression should be simply (ρE/ρ0), where ρ is the density of the honeycomb, ρ0 that of the material of the honeycomb and E the Young's modulus of the material. However when honeycomb sandwiches are tested under compression between flat platens it is common experience that the deformations recorded are markedly greater than those predicted from the theoretical modulus. In order to throw light on this discrepancy comparative tests have been made on three samples, two of normal thicknesses, namely in and in, and the third 8 in thick.