An experimental investigation has been carried out to compare the effects of sweep direction upon the aerodynamic characteristics of three wing planforms. The wings have biconvex aerofoil sections which allow them to be tested in both the forward-swept and backward-swept configurations without changing the section profile. Measurements of lift, drag and pitching moment have been made for angles of incidence in the range —5° to +50° at a mean chord Reynolds number of approximately 1·5 × 105 and a Mach number of 0·1. To complement the force and moment data a comprehensive series of oil-flow visualisations are also presented. In addition the aerodynamic characteristics of simple strakes (wing root fillets) have been studied for both the swept-forward and swept-back configurations.

This Paper was originally written at the request of L'Association Francaise des Ingenieurs et Techniciens de L'Aeronautique (AFITA) and was presented at a meeting in Paris on 30th April, 1946. The Service Technique of the French Air Force were also interested.

The Paper reproduced here represents the entire lecture, except for those parts which were concerned purely with the French picture.

Compared with most other industries a distinguishing feature of the air transport business throughout its history has been the rapid development and replacement of its flying equipment. Aircraft have evolved to meet the needs of expanding traffic and each generation has been succeeded by different, newer and better versions. The thirties saw the appearance of the all-metal monoplane with piston engines and propellers.

Kites are currently used in a number of applications (anemometry, aerial platform, traction), but very little information is available for the systematic design of kite systems. An experimental technique based on an instrumented tether for single-line kites is described. This was used to measure the performance of a variety of single-line kites. The analysis techniques are briefly outlined, and incorporate allowances for kite unsteadiness, the displacement of the kite from the anemometers, extrapolation of the line tension from the tether to the kite, and the kite’s velocity relative to the ground. The results are correlated with aspects of kite design, and specific recommendations for kite applications are made.

Several Attempts have been made lately to reduce the drag due to lift of wings by means of camber and twist. Slender wings in particular have been considered and a typical theory is that by Tsien on the supersonic conical wing of minimum drag, where the lift forces on the wing are calculated from conventional aerofoil theory so that the overall lift of a flat wing turns out to be proportional to the angle of incidence. For convenience, this is called a “ linear theory.” It is usual to consider two cases: (1) Wings where the drag is calculated by the same theory so that the full thrust component and the suction at the leading edge are included. (2) Wings where the drag is not calculated by the same theory as the lift but where the thrust at the leading edge is omitted.

From Mr. A. M. Dobson's Note (July 1955 Journal, page 506) which dealt with the stability of an axially loaded continuous beam, and other contacts we have had with the Aircraft Industry, it would appear that the very considerable developments of structural theory which have taken place in relation to continuous beams subjected to axial load, as employed in normal structural steel work, are not well known in aircraft stress offices. The list of references appended may then be found helpful.

In 1954, Preston introduced a new concept of skin friction measurement in turbulent flows by using a surface pitot tube. Since then considerable controversy has risen in the use of Preston tubes for skin friction measurements. However, Head and Rechenberg investigated Preston tubes extensively and confirmed the validity of the Preston tube method. Recently Rajaratnam has given a theoretical calibration curve for the Preston tube using logarithmic velocity distribution for the boundary layer velocity profile.

Scientific and technological development over the past 20 years has been tremendous. It presents the military planner with a dazzling array of possible developments to meet a wide range of operational requirements. Unfortunately, in every country resources are limited and a choice between the various alternatives has to be made. An objective and, if possible, quantitative method of examining alternative proposals is required. This is what cost-effectiveness analysis attempts to do. It can be and is applied at any level. For example, the government may require a study examining the implications of the different allocations of national resources to defence, foreign aid, civil industrial research, social security benefits, etc.; the Ministry of Defence may require a study examining the balance between the forces on land, at sea or in the air (force structure) and the contribution each make in a number of scenarios; a single service may require a study of the resources that should be allocated to defensive or offensive action; within a single role a study may be required of the alternative weapons that could be deployed to meet a particular requirement. In this paper, only questions arising in the study of defence systems will be considered.

The solution of sandwich plate problems by the framework method is proposed and the basic elements of the method used are reviewed. The technique is demonstrated by application to a simple framework analog for rectangular sandwich panels with very thin faces and an antiplane core. A number of illustrative examples involving small and large deflections are solved.

Unshrouded impellers of centrifugal compressors and centripetal turbines manifest an increase of the flow losses in comparison with the shrouded ones. Assuming that the controlling factor in such increase of loss is the leakage through the gap between wheel and casing, the author develops a simple theory leading to a formula for the volumetric efficiency. Only one experimental quantity is required for applying the formula; and tentative values, based on some experimental evidence, are presented.

The Association is pleased to announce that the prize of £50 for the 1958 Cierva Essay Competition has been awarded to Mr E R Kendall

Mr Kendall, who is 25 years of age, is a Project Aerodynamicist with the Helicopter Division of Saunders-Roe Ltd He served his apprenticeship with that Company and in 1955 was nominated by the S B A C for a two year course at the College of Aeronautics, where he specialised in helicopter aerodynamics For his exceptional ability in technical study whilst at the College, he received the 1957 Alan Marsh Memorial Award which enabled him to take a short course of helicopter piloting instruction at Air Service Training He is an Associate Member of the Association

The attainment of the mighty speed of 379 miles an hour by an officer of the Royal Air Force (Flight Lieutenant Stainforth) is fresh in our minds and we honour the pilots, the aircraft builders and the engine constructors who made this possible. We remember also, I hope, the scientific workers, whose investigations afforded the basis on which so much else was built. When one contemplates motion at such speeds as this, one cannot help speculating where such enterprise will lead. The power to move is not new; railways and roadways give abundant evidence of high speed, but motion along them is almost entirely in two dimensions. It is only when the freedom of the air makes three-dimensional motion possible that the problem appears in its greatest and most interesting aspect. In the air there is combined the greatest possible freedom with the highest possible speed, and it is this combination which makes the study of such intense scientific interest. Moreover, the flight path may be greatly curved and that curvature may be in any plane. Great forces may then arise and act upon the aircraft from any side. It is not for nothing that the pilot is strapped into his seat.

The method of matched asymptotic expansions is used to calculate the lift for a class of thin aerofoils with highincidence flaps or blunt trailing edges. The analysis is based on smallness of the ratio between the flap length (or trailingedge thickness) and the chord of the main foil. Results are compared with exact solutions for bent plates and for triangular and quadrilateral bodies. A procedure for extension to general trailing-edge configurations, including detached flaps, is outlined.