A recent paper on the potential incompressible flow through two-dimensional contracting ducts raises some interesting points that are relevant to the hodograph technique for solving this problem.

In this paper, Lau obtains a contraction shape by placing a source in a uniform flow that is contained in a doubly infinite strip. The resulting flow pattern is sketched in Fig. 1. The flow is from a region of unit velocity to one of velocity R, where R is the contraction ratio. A streamline, intermediate in position between ψ = 0 and ψ=1.0, is adopted as the contraction profile.

Interest in sail design has recently stimulated some work, using thin aerofoil theory, to obtain the velocity distribution on simple polynomial mean lines. In particular in reference 1, a solution has been obtained for a cubic mean line. There is an omission in equation (3) of this reference where an x should appear in the numerator outside the curly bracket. (The equation is subsequently used in its correct form).

In the present note a general solution is obtained for polynomial mean lines. It is demonstrated by applying the result to Boyd's equation (3).

In every country where agricultural aviation is done as a private enterprise, some system of rules and regulations is sure to exist and the International Agricultural Aviation Centre has collected data on this subject.

To imagine, however, that a system of regulations, ideally suited to all cases, could be drawn up on a basis of these national rules is an illusion. Every country—and this holds true for many spheres—is blessed or cursed with the laws it deserves. For all these systems of laws and regulations are determined partly by internal and partly by external factors. Let us compare two countries. One is densely populated with intensive agriculture, the other sparsely populated with extensive agriculture. It is obvious that the first country will have a more comprehensive system of regulations in regard to agricultural aviation than the second country. The denser population necessitates a higher grade of protection against the dangers from both the aircraft themselves and the drift of toxic chemicals. Quality agriculture demands quality work from the aerial applicator.

The equation for the buckling of a homogeneous elastic plate is well known

For a simply-supported rectangular plate without shear (Nxy=0), the critical loads are usually found by substituting into equation (1) and determining the loads at which nontrivial solutions exist. In the presence of shear, however, the difficulty with the above approach is that the shear term would involve cosines instead of sines.

In using resistance wire thermometers for measuring transient gas temperatures, such as internal combustion engine exhausts, errors occur due to the thermal inertia of the wire and conduction along it and the supports.

Benson and Brundrett analysed the situation by solving the heat transfer equation for a particular case where the gas temperature was assumed to vary sinusoidally with time. An estimate of the maximum error for particular sizes of wire could be obtained. Conduction in the supports was neglected.

In the early part of this century aircraft were flown only when the pilot could control them by reference to outside sources—the ground, the sky and the horizon. Soon, however, instruments were developed which enabled him to fly in cloud or darkness. The Second World War with its blackout enforced this need for total blind flying and, as a consequence instruments and techniques were perfected, ending with what was known as the standard blind flying panel. This has remained substantially unchanged in the majority of aircraft up to the present day. This paper reviews the presentation and the principles which led to its development and then discusses some recent developments in this interesting field. First it is necessary to look at the problem in more detail.

This note illustrates the correlation of the pressure distributions measured on three NACA 16-series aerofoils at subsonic and transonic speeds. The transonic similarity parameters proposed by Spreiter

are used for the subsonic, transonic and supersonic types of flow illustrated in Fig. 1.

I am grateful to Mr. Llewelyn for pointing out the slip in equation (3) of reference 1.

In considering a particular case of the polynomial camber line I did have to evaluate a number of integrals of the kind but the process is not as laborious as perhaps Mr. Llewelyn implies for there is a simple recurrence relation between integrals of this kind.

The German metallurgists were the first to discover how to make the light alloy of aluminium which they called duralumin. I understand it is a mixture of 97 per cent aluminium and 3 per cent copper, but it may have a very small percentage of rarer metals. Whereas aluminium has a yield point of about nine tons per square inch, duralumin has a yield point of twenty-five tons per square inch.

Before and during the First World War the German aircraft constructors used duralumin in the construction of Zeppelin rigid airships, aeroplanes and seaplanes and flying boats. Towards the end of the First World War, I began to fear that the Germans would invent all-metal aircraft with highly streamlined forms which would increase the speed of their aircraft and that at very high speed with their bombing aircraft, they would fly at almost house top level, drop a time bomb on our works and be at a safe distance before the explosion occurred.