Until recently, aircraft cooling requirements were met by direct heat transfer to free stream. Flight at high subsonic speeds brought forth a need for crew compartment refrigeration. Supersonic flight may result in an extension of this technique to a wider field, particularly the cooling of equipment and temperature-vulnerable functional materials.

This state of affairs has arisen from two major factors. Firstly, the hot boundary layer which surrounds the aircraft and would ultimately soak it to maximum boundary kinetic temperature. Secondly, ducted air either for the engine, equipment cooling, or crew conditioning, is received at nearly stagnation temperature. This temperature increases rapidly with Mach number and reaches its first unacceptable level, i.e. for crew cooling, at low altitudes in the transonic range.

During my five years from July 1929 at Weybridge the amount that was done was amazing, although the technical and design staffs were microscopic by present-day standards. The types included Vimy, Virginia, Victoria, B.19/27 Night Bomber—all of these were twin-engined—Type 163, 4-engined Night Bomber, a P.V. with tandem engines; Vespa, Vildebeeste Torpedo Bomber and other roles, C.O.W. Gun Fighter, G.4/31 Reconnaissance Bomber (2 versions)—all of these were single engined military machines; Viastra, passenger carrier, Vellore and Vellox Freighters—twin-engined civil aircraft, although Viastra first flew with three engines. All were biplanes with the exception of the C.O.W. Gun Fighter, the Viastra and the second prototype G.4/31 which were monoplanes. Incidentally, the G.4/31 was the first example of geodetic construction, the fuselage being so constructed. My recollection is that Mr. Wallis was responsible for the structural design of this aircraft which had an unusually large aspect ratio. It became the Wellesley, had a most honourable career in the R.A.F. and of course held the world's long distance record for many years.

Terms used in the description and analysis of the external drag of a body (with or without internal flow) are considered, and definitions suggested for the various components of the drag. Care has been taken to ensure that the proposed terms are consistent with those used in the Panel's report on thrust.

In recent years there has been a rapid expansion of the ranges of speed and altitude that are of practical interest to aircraft and missile designers. In consequence, several new terms have been introduced to describe the new flow regimes that require to be considered and, at the same time the meanings of some of the older terms have undergone a measure of modification. The meanings attached to these terms by different workers have not always been consistent, differences have sometimes arisen from the differences of outlook between theoretical and experimental workers or between those concerned primarily with the motion of a fluid and those concerned primarily with the forces on a body in the fluid. To avoid the confusion that may readily arise if such differences become too well established it was felt desirable at this stage to attempt the formulation of unambiguous definitions of the more important terms in current use.

The difficulties of determining latitude and longitude under adverse weather conditions, when neither the Sun nor stars can be sighted, are well-known, and the advantages of a non-visual system of position finding which could operate through clouds or fog are too obvious to require emphasis.

A Radio Sextant, which detects and locks-on to 8 mm. radiation from the Sun, has already been made and tested in America with reputedly excellent results. An analysis of both the theoretical and the practical design factors is given in the present paper, together with the results of successful experiments made in Great Britain.

The Propelling Nozzles tested are turned from brass and the interior surface finish shows a centre line average of about 15 micro inches when examined on a Taylor Hobson machine. This is fairly rough compared with the estimated boundary layer thickness and it was required to know whether this in fact affected the thrust. The thrust of a nozzle manufactured by the usual process was measured before and after a polishing process. An improvement of one half per cent was recorded.

The Important characteristics of the turbulent velocity profile of a plain concentric annulus and some of the methods of correlating the velocity distribution are briefly reviewed. The average velocities in an annular section are examined and some experimental data is correlated by a modified power law.

A Phenomenon of interest in the study of high-speed aerodynamics concerns the flows generated around very slender bodies of revolution. It has been observed that these bodies, at moderate and large angles of attack, produce a kind of flow pattern that differs considerably from the ones assumed in perfect-fluid treatment according to the usual slender-body analysis.

Photographs reveal that the flow above the upper surface of the body contains two symmetrically disposed spiral vortex sheets which roll up and are carried down-stream. Viewed in respect to the stationary body, the shed vortices appear fixed. The vortices increase in strength as anybody cross plane moves rearward, being eventually discharged to form a Karman vortex street as viewed in the moving cross plane.

In the July JOURNAL, page 528, Dr. H. Fessler describes a method of testing struts using links in tension to apply the load.

A much easier and cheaper method is to use sharpened rods as struts tested between hard flat plates. As the load increases the ends continually crush so that there is no restraint and the equivalent to a pin joint is obtained.

Eccentricities can easily be obtained by bending the rods and the amount can be checked by mounting between female centres and rotating. At least three specimens of each length should be tested. A strut curve consisting of failing stress plotted against length divided by radius of gyration can then easily be obtained for use with the material, without the use of theory.

In the bending and vibration of plates it is found that the values of maximum deflection and natural frequencies, respectively, vary considerably from the simply-supported to clamped edge conditions. For an estimation of these characteristics in the intermediate range a generalised boundary condition may be assumed, of which the simply-supported and clamped edges become limiting cases. While Bassali considers the ratio of edge moment to the cross-wise moment as a constant, Newmark, Lurie and Klein and other investigators, in their analyses of various structures, consider that moment and slope at an end are proportional.

Here the definition of elastic restraint as given by Timoshenko, α=βM, is followed, where α is the slope at any edge, M the corresponding edge moment per unit length while β is the elastic restraint factor. β→0 and β→∞ represent the two limiting cases of simply-supported and clamped edge conditions.