In presenting this paper an attempt has been made to examine the development of current propeller theory and practice to cover the range of aircraft speeds between 450 and 550 m.p.h., which at 36,000 ft. represents a flight Mach number range of about 0.68 to 0.83. Inevitably in such a discussion it has been necessary to peep over the wall into the realms of higher speeds, but no serious attempt has been made to cover such a controversial region because of the lack of experimental data.

A theory of primary failure of compression panels of integral construction with unflanged stiffeners is presented, involving rotation, or translation, or rotation and translation of the stiffeners with the corresponding distortion of the sheet without deformation of the cross sections in their own planes. The investigation shows that the failure may occur generally either by pure torsion of the stiffener with the associated lateral distortion of the sheet or by pure flexure in accordance with whichever mode yields a smaller stress. The theory is compared with the test results covering a fairly wide range of the dimensions involved. The theory is in complete agreement with the experiments. The accuracy of the result thus obtained indicates that the fillets at the junction of the skin and the stiffener are not important and their effects may safely be disregarded.

The performance of aero gas turbine combustion chambers is discussed under the following headings : Combustion efficiency, combustion stability, ease of ignition, deposits, exhaust temperature variation, and smooth combustion. It is shown that, as assessed by these criteria, combustion chamber performance can be significantly affected by fuel characteristics; also that the effects of fuel type can be greatly modified by equipment design changes. The conclusion is that most of the problems- aggravated by fuel characteristics are better solved by modifications to equipment, if fuel availability and cost are not to be adversely affected.

From the earliest days of flying, gusts have been a problem for aircraft. In the very early flights aircraft were flown only when it was nearly dead calm and few gusts were met. Later on and, in fact, almost up to the Second World War, flying was greatly restricted by the ground and air conditions at the aerodrome. This meant that there had to be fairly good visibility and that the grass aerodrome must not be unduly softened by water. Since the war, aircraft have been flown with much greater regularity.

The design of the static and pitot static tubes which are still in common use—such as the National Physical Laboratory standard head or the Prandtl tube, dates back some forty years (see Ref. 1). Before these tubes can be used it is necessary to calibrate them, using a replica of the instrument which is commonly regarded as the standard. This procedure assumes a perfect replica. Furthermore, the shape of the instrument head used hitherto (conical or hemispherical) is known to be aerodynamically poor and, as a consequence, the calibration factor varies unpredictably with wind speed, stream turbulence and Mach number.

Measurements were made of the pressures in flattened, blunt-nosed pitot tubes, in an air stream at Reynolds numbers from 13-1,000 (based on the external height of the tube). Three tubes were used, having cross sections with ratios of width to height (W/H) of 3, 7 and 11.

The collected comments of Messrs. Greenwood (December 1953 and October 1954 JOURNAL), Thorne (February and October 1954 JOURNAL), and Asquith and Whitaker (May and October 1954 JOURNAL) on the definition of specific impulse in the field of rocket propulsion argue certain traditional points of view, each of which has enough merit to gain proponents but apparently not enough merit to gain universal acceptance.

In a Technical Note published in the April 1954 issue of the JOURNAL an approximate equation was presented for calculating the propeller moment of a helicopter rotor at the project stage, the solution to which could be obtained from two graphs.