Curves are presented which, together with a knowledge of the intake performance, enable ram-jet thrust coefficients and specific consumption figures to be obtained quickly and accurately in the range M = 1·0 to 3·0.

Expressions are obtained for the radial, tangential, and shear stresses in an infinite plate containing a variably reinforced circular hole. The variation in the cross-sectional area of the reinforcement is chosen so that the maximum tensile resistance of the reinforcement occurs at points around the hole where the stresses in the plate tend to be high. It is shown that when the reinforcement has a given weight, the effect of varying its cross section is to reduce the stress concentration in the plate.

The following particular applied stress systems are considered:—

1. (i) Uniform tension or compression in one direction.

2. (ii) Uniform shear.

3. (iii) Unequal principal stresses.

For the particular cases of uniform end loading and unequal applied stresses in the ratio 2:1, data have been obtained which enable the designer to determine the stress distribution in plates with reinforcements having a reasonably wide range of practical dimensions.

The paper examines the error involved when the continuous distribution of lift on an unswept lifting surface is represented by a finite number of horseshoe vortices, the strengths of which are determined by a prescribed downwash. Attention is directed mainly to the case of elliptic loading, but an anti-symmetrical case is also studied to ensure that the conclusions are not peculiar to the elliptic case.

The paper describes a method of estimating the frequency of gust components in the plane of a propeller from measurements of vertical gust components, which are those generally recorded. By this means additional flight recording is avoided and the danger of under-estimating the frequency of gusts affecting the propeller is reduced. Random distribution of gusts in space is assumed. It is found that gust components in the plane of the propeller of 10 ft./sec. or more occur 2·51 times as frequently as vertical components of 10 ft./sec. or more. For speeds greater than 10 ft./sec., the ratio is higher.

An approximate theory is described which takes into account the influence of the wake on the aerodynamic derivatives of an oscillating rotor blade. It is shown that the most important parameter is the number of cycles of the oscillation which occur during one revolution of the rotor. For integral values of this parameter the flexural damping is shown to become very small at small angles of incidence. The flutter characteristics of a simple rotor blade are calculated on the basis of this theory, and it is found that the wake causes radical changes in the critical speeds. The theory is in good qualitative agreement with experiment.

The method which was developed in an earlier paper for calculating the lift on a thin jet-flapped aerofoil has been applied to the case in which the jet enters the main stream tangentially from a deflected flap. The lift derivative with respect to the (small) angle of deflection β is of the form

where , E being the ratio of flap length to aerofoil chord, and D0 a function both of E and of the jet momentum coefficient CJ. In the special case CJ = 0, Do vanishes and the classical results for attached flow on flapped aerofoils without super-circulation are obtained. More generally, Do has been evaluated over the range 0<CJ<5 for six ratios E between 0·02 and 0·50, using an electronic computer. The lift derivatives so found lie between those in the limiting cases of “deflection” (E = 0) and “incidence” (E=1) which were calculated in Reference 1. They show that the effectiveness of the jet-flap scheme might be greatly increased by blowing over flaps of the order of 20 or 30 per cent of the chord, rather than over the small “shrouds” which have hitherto been proposed.

This paper gives some identities concerning the flexibility of certain elastic structures, including flat plates, at the onset of buckling and subsequently. The identities have a useful application in determining the flexibility and the rate of change of flexibility with load for structures in which the mode in the buckled state changes continuously with load.

In this note Ward's “area-transfer rule” is modified in order to make it more suitable for configurations with fuselages or nacelles which are neither slender nor smooth (although they are assumed to have small profile slope). The body source strength of Ward's analysis, which is appropriate only for smooth, slender bodies, is replaced by a source strength which is valid more generally. However, the drag contributions of the body multi-sources and of the interference field are still neglected, so that the theory is tentative rather than rigorous.