The 909th Lecture to be given before the Society and the 16th Main Lecture at a Branch, was held under the auspices of the Chester Branch of the Society on 8th April 1954. Mr. K. G. Hancock, Chairman of the Chester Branch, expressed the pleasure of the Branch at having a Main Meeting of the Society at Chester and welcomed the visitors, particularly the officers of the Main Society. He then asked the President, Sir William Farren, to preside for the rest of the Meeting.

The association of a gas turbine with a piston engine is by no means a recent conception. As early as 1924 a Napier Lion Series V engine was equipped with a turbine in the manner shown in Fig. 1, the exhaust gases being fed into the turbine to provide all the power to drive the engine supercharger.

At a later date during the 1939-1945 War, many engines were installed in operational aircraft fitted with “turbo-chargers” of the type shown in Fig. 2, in which an exhaust activated turbine drives a subsidiary blower boosting the air intake of the normal engine supercharger.

The issue of the Royal Aeronautical Society Structures Data Sheets 02.01.28 to 37* prompts the publication of a short survey of the theory on which these sheets are based and of the manner in which they may be applied. To save the need to refer to original sources the theory is developed from first principles; but for brevity the application is illustrated only by one simple example. Other more elaborate applications are illustrated by the example data sheets themselves. A recent paper by Chilver covers the same ground from the mathematical point of view and the purpose of the present paper is to illustrate the practical application of the method to familiar problems in the computation of initial buckling stress for sheet-stiffener combinations.

The title of this paper is not strictly correct since it is not really concerned with “efficiency” in the accepted sense of the word. It has in the past been considered that the sole duty of an engine air intake is to deliver air to the engine at a high efficiency, that is at a mean total pressure as nearly as possible equal to the aircraft pitot pressure. More recently other considerations have arisen, such as the necessity of avoiding asymmetric flow in twin duct air intakes. These aspects of air intake design have frequently been discussed, for example in Dr. Seddon’s lecture to the Society in December 1951, but the particular subject of this paper has been rather neglected—the velocity distribution of the air delivered to the engine.

The stability criteria for systems whose characteristic equations are of the eighth degree are expressed in a convenient form and a detailed scheme for the computation of the complete set of test functions in sequence is given. A special method for the direct calculation of the critical test function T7 is also given; the vanishing of this determines the critical flutter speeds of quaternary systems.

The flexural vibration of uniform plates on uniform elastic foundations is of interest in connection with fatigue and sound intensity studies.

This note presents in matrix form the equations of motion of a rotating and vibrating beam. The natural frequencies of the system are obtained by plotting an impedance-frequency diagram and noting the frequencies at which the impedance vanishes. Uncoupled bending vibrations are considered but the analysis can easily be extended to include coupled bending-torsion vibrations. The arrangement of the method for solution on a digital computor is quite straight-forward.