The application of scientific principles to the design of aircraft and aircraft equipment during the post–war years has yielded results which are becoming increasingly apparent. The time interval which elapses between the conception of an idea and its application to production aircraft is necessarily long, but it would seem that we are just commencing to reap the reward of much patient study.

An attempt will be made to present a picture of the progress which has recently been made and to indicate the lines along which further research would appear most profitable. In making this review it is inevitable that attention should be paid particularly to Service aircraft. The more difficult the problem the greater is the ingenuity required to solve it, and the ever increasing demands made upon the designers of Service aircraft have stimulated research to perhaps a greater extent than is the case with civil aircraft, the requirements for which are less complex.

In the following article an attempt has been made to present the characteristics of a sail by considering it as an aerofoil, the “ lift ” and “ drag ” being replaced by two forces mutually at right-angles in a horizontal plane, one force corresponding to the drag, acting in the same direction as the relative wind. It appears that skill in the art of sailing could be reduced, apart from other considerations, to ability to set the sail in the required position determined by its aerodynamic characteristics.

In many branches of engineering, especially the aircraft industry, numerous geometric problems arise which present considerable difficulty to draughtsmen and designers. The object of this paper is to present methods which the writer has developed which enable any problem of the type under consideration to be rapidly solved. The majority of these problems arise in cases where, although sufficient data is provided to enable ordinary three view drawings of a particular part or assembly of parts to be made, angles and lengths have to be found which cannot be directly obtained from this three view drawing.

The issue of the Royal Aeronautical Society Structures Data Sheets 02.01.28 to 37* prompts the publication of a short survey of the theory on which these sheets are based and of the manner in which they may be applied. To save the need to refer to original sources the theory is developed from first principles; but for brevity the application is illustrated only by one simple example. Other more elaborate applications are illustrated by the example data sheets themselves. A recent paper by Chilver covers the same ground from the mathematical point of view and the purpose of the present paper is to illustrate the practical application of the method to familiar problems in the computation of initial buckling stress for sheet-stiffener combinations.

Measurements were made of the downwash effects behind two finite wings 3.1 percent, thick, having square and 20° raked tips respectively. The tests were conducted at a Mach number of 1.45 and a Reynolds number of 1.2 millions by traversing a yawmeter 1.62 chords behind the trailing edge of the finite wings.

In general, a maximum downwash of the order of ½° per degree of wing incidence was observed in that portion of the tip Mach cone behind the wing, and a maximum upwash of similar magnitude was observed in that part of the tip Mach cone situated outboard of the wing.

Thus it is apparent that these effects are large enough to affect the lift on any surface situated in the tip Mach cone behind a finite wing. In particular, placing the rear surface in the downwash region behind a finite wing, will tend to reduce the overall lift while placing it in the upwash region will tend to magnifiy the variations of lift initiated by the finite wing.

The work reported in this Note originally formed part of a comprehensive investigation into the fatigue strength of magnesium alloy ZW2 (2 per cent. zinc, 0·65 per cent. zirconium) in sheet form. The major portion of the programme was eventually cancelled but the tests herein described are sufficiently self-contained to be repotted by themselves. Direct stress fatigue determinations were made on small round test pieces machined from ¾ in. thick plate, at mean stresses of 0, 4,000, 8,000 and 13,000 lb./in.2. Static and rotating bar fatigue tests were also made.

One of the main problems in connection with the development of air-cooled engines appears to consist in securing adequate cooling without increasing the head resistance above that of corresponding water-cooled engines.

This problem particularly applies to large air-cooled engines which are limited in size by cooling difficulties. Air-cooled engines for windmill planes and helicopters for alternate slow and fast flying present a further problem, because such aircraft engines will be required to develop maximum horse-power when the speed of translation is lowest.

The airflow over the nose of a bulky body, such as that of an aeroplane, diverges radially in every direction from its axis. Such radial flow tends to overshoot laterally, at its core, the periphery of the engine or other obstruction and so depart from the contour thereof, with the result that a considerable turbulence is set up. Such turbulence has also the undesirable effect of causing a reversal of the pressure gradients, and a corresponding reversed or forward flow of air, in the boundary layer behind the engine, thereby creating a ” dead “ area or areas and so considerably reducing the cooling effect of the general air flow and increasing the turbulence.

The rotary derivatives of a Delta wing pitching or rolling at supersonic speed are obtained in addition to the lift curve slope first given in an earlier investigation.

The problems discussed here are those of a uniformly inclined and skew loadings on a finite rectangular plate such as would be obtained by the action of wind or rain on a large door of an aircraft hangar or other such building. Such a force may be considered constant in magnitude over the area of the plate but non-normal in its direction with the plate.

In a recent article Lundberg has made reference to use of the “ Hydraulic Analogy ” for quantitative investigation of gas dynamics phenomena. This is quite feasible provided that the basic analogy and its limitations are properly understood. In fact, considerable progress has already been made and it has been proved possible to utilise the analogy for both supersonic and transonic research.

A study of the mathematical analogy indicates that the strongest physical analogy between a two-dimensional (inviscid) gas flow and a three-dimensional (viscous) water flow exists for the transonic case when the water depth is approximately one quarter inch and the model is towed. Only thin profiles with small incidence can be sensibly investigated. Under such conditions the analogous water flow may be considered as a distorted dissimilar model of a corresponding prototype gas flow.