When designing an aircraft structure, the structural engineer has to achieve given standards of airworthiness in respect of strength, stiffness and fatigue life while ensuring that the final weight is as low as possible to give operating economy or flexibility. At the same time he must ensure that a minimum of design effort is used, manufacture is as easy as possible, the serviceability is good, the aerodynamic shape is retained, aeroelastic effects minimised and so on. The structural engineer of today has to ensure that the fatigue life is satisfactory, together with the older concept of purely static strength, and if he has resorted to the use of fail safe principles he has to establish those characteristics as well.

The results of experiments on the reattachment of a laminar boundary layer, separating from a rearward facing step in a flat plate aerofoil, are correlated with the properties of the short leading edge bubble which forms on thin aerofoils near the stall.

The experiments, comprising pressure measurements, Pitot explorations, liquid film and smoke studies, indicate that for all Reynolds numbers above the value given by the Owen-KIanfer criterion the reattachment is turbulent behind a stationary air reverse flow vortex bubble. It is also found that the reattachment is laminar for Reynolds numbers below the critical, which further supports Crabtree's interpretation of the Owen-KIanfer criterion in terms of the condition for the growth of turbulent bursts.

In the present era of supersonic and hypersonic flight, structural analysts are well aware of the new problems that arise from the exposure of aircraft and missile structures to elevated temperatures. The task of solving these problems is in its early stage of development. Since the problems are diversified in nature, a different method of solution has to be developed in each case. It is probable that in some cases radically new techniques may have to be devised. Until such time, the structural designer is forced to take a realistic view and use satisfactory extensions of existing methods of analysis.

There are many problems to be solved when it is required to fly an aircraft at speeds approaching the speed of sound. When the speed of the aeroplane exceeds its critical Mach number, regions of supersonic flow appear at points on its surface, where the velocity of the displaced air is greatest. These regions of supersonic flow increase in size with increasing speed until the flow is wholly supersonic. The range of speed in which this mixed flow occurs is called the transonic range. In this range an aircraft will experience a sudden increase in drag, trim changes, loss of control effectiveness and possibly instability, or buffeting.

Whenever a new and truly great idea is put forward for the first time it is usually received with scorn and derision by those whom it directly concerns. Such was the initial reception of the idea of refuelling aircraft in flight.

Soon after the First World War air carnivals became very popular around the flying fields of the United States of America and it was in a search for new stunts that two intrepid fliers hit on the idea of transferring fuel by hose pipe from one aircraft to another. The two single-seater aeroplanes flew one above the other, the upper one carrying the extra fuel; in order to transfer it the pilot threw a length of hose overboard leaving it trailing behind him. The receiver aircraft then manoeuvred into position and the pilot caught the hose and put the nozzle into his reserve fuel tank. When a small quantity of fuel had been transferred, he pulled out the hose and threw it clear of his aircraft, leaving the donor aircraft to haul it in.

An experimental verification of coles’ postulate of the Law of the Wake in three dimensions has been attempted. This hypothesis, which is strongly supported by experimental evidence in two dimensions, purports to represent the velocity vector in a yawed boundary layer by the sum of two vectors, whose magnitudes are found from the universal law of the wall, and a second universal function, the law of the wake. It has been found that the velocity vector can be represented in this way and the wake function required for this is very similar to Coles’ form. Limitations of the experimental arrangement however prohibited the comparison of vector directions with that proposed by Coles.

The problem of flow past a thin wing of circular plan form when the undisturbed flow is along the x-axis, U(z)=Az+V has been solved.

The solutions for potential flow past a wing of circular plan form have been given in terms of spheroidal co-ordinates using the concept of acceleration potential. The solutions can be easily adapted to the case when the undisturbed flow is weakly sheared. In the particular case when the undisturbed velocity U(z) = Az+V, where A and V are constants, the pressure equation can be simplified by a simple substitution and the solution for a thin wing of circular plan form can be easily constructed from the solution for potential flow. If the wings in the two cases develop the same lift, it is found that the wing in shear flow should be slightly cambered (potential wing is un-cambered). The results are shown graphically in Fig. 1.

The Rayleigh-Ritz method is well known as an approximate method of determining the natural frequencies of a conservative system, using a constrained deflection form. On the other hand, if a general deflection form (i.e. an unconstrained form) is used, the method provides a theoretically exact solution. An unconstrained form may be obtained by expressing the deflection as an expansion in terms of a suitable set of orthogonal functions, and in selecting such a set, it is convenient to use the known normal modes of a suitably chosen “ basic system.” The given system, whose vibration properties are to be determined, can then be regarded as a “ modified system,” which is derived from the basic system by a variation of mass and elasticity. A similar procedure has been applied to systems with a finite number of degrees of freedom. In the present note the method is applied to simple non-uniform beams, and to beams with added masses and constraints. A concise general solution is obtained, and an iteration process of obtaining a numerical solution is described.

While staying at the “Old England Hotel” Bowness-on-Windermere at the end of May in 1912 one heard and then saw what was loosely called an aeroplane flying over the Lake. It is of some “historic” interest that the car which brought us to Bowness was a 45 h.p. six cylinder Napier San Giorgio model. The Hydro Biplane was garaged in rather untidy looking wooden sheds only some 100 yards from the Hotel and I have a clear recollection of the following facts. The photographs (Figs. 1 and 2) show it to be a single-engined pusher propeller biplane on one central float. It always flew at a height of about 100 yards at around 50-60 m.p.h. A little speedier “ downhill.” Taking off speed was about 50 m.p.h. The pilot (see Fig. 2), I never knew his name, flew two or three times a day in suitable weather garbed like the present day motor cyclist but without crash helmet.