The 996th Lecture to be given before the Society and the 26th Main Lecture to be held at a Branch of the Society, was also the First Sir Henry Royce Memorial Lecture inaugurated by the Derby Branch. The Lecture, “ Sir Henry Royce, Bart,” was given by Mr. Ivan Evernden, M.B.E., B.Sc.(Lond.), M.I.Mech.E., M.S.A.E., M.S.I.A., on 1st October 1956 at Derby. Mr. A. A. Rubbra, F.R.Ae.S., Chairman of the Derby Branch opened the Meeting and Dr. E. S. Moult, B.Sc.(Eng.), F.R.Ae.S., Vice-President of the Society, presided for the rest of the meeting.

The designer of transport aircraft can play a very important rôle in improving the economic efficiency of air transport and the following analysis is devoted to a review of some calculations illustrating this aspect of aircraft design.

Economic efficiency must not be obtained at the expense of other necessary qualities, and it would be as well to touch briefly on some of these before considering cost alone.

1. (a) Safety and Comfort

2. American experience shows these factors to be as important as any. The introduction of a type of aircraft with a good reputation in these respects leads to remarkable popularity.

3. (b) Speed

4. This, the main advantage of air over sea, rail and road transport (reducing a journey of weeks to days, and of days to hours), has a very different importance when reduced to the possible saving of a few further hours or minutes. For usual aircraft engine combinations, it will probably be found worthwhile to increase the cruising speed to that at which economic and safe continuous running of the engines is not exceeded.

An experimental determination of the relation between the rate of sink of a sailplane and its air speed is of interest both to the designer and to the pilot. This paper describes tests made to establish this relation for the Slingsby Sky. During the tests, the aircraft was flown in a series of “ partial glides ” at constant speed, while a camera looking over the pilot's shoulder photographed the altimeter and A.S.I., together with a slip indicator and a clock. From an analysis of the photographic recordings, the mean air speed and the rate of sink during each partial glide can be determined; a large number of such results enables the relation between air speed and rate of sink to be established. The final results show that a considerable improvement in high-speed performance can be achieved if the aircraft is fitted with a long skid instead of the short skid and large fixed landing wheel; the superiority of the Sky over the Weihe for competition work is demonstrated. Sources of error in the results are discussed; it is shown that the accuracy with which the rate of sink may be determined is limited by the presence of vertical air movements. Possible future trends in performance testing technique are discussed.

Not to go too far back in years, and to relate a few facts within the lifetime of most of you present to-night, I may commence by saying that it was in 1909 that Admiral Lord Fisher instructed Admiral Bacon to proceed with the design and construction of a rigid airship, attention having been called to the success attending Count Zeppelin's efforts and to the fact that we could not realise the dangers to which we might be exposed until we possessed airships of our own.

Admiral Bacon got into touch with Messrs. Vickers' experts, and Naval Airship No. 1, nicknamed the “ Mayfly,” was built at Barrow. Messrs. Vickers deserve all credit for their pioneer work on airship design and construction in this country, and it was only very bad luck that prevented their building the bigger ships.

A meeting of the Royal Aeronautical Society was held at the Institution of Civil Engineers, Great George Street, Westminster, on 11th December 1946, at which a paper, “ Lofting and Template Reproduction,” by Mr. S. P. Woodley, was read by Mr. L. G. Burnard. In the Chair, Sir John Buchanan, F.R.Ae.S.

In Switzerland aircraft often have to take off and land in narrow mountain valleys where a strong, irregular wind is blowing. In these circumstances one faulty casting may cause failure of a control; or a small part, if insufficiently heat-treated, may fracture and result in the loss of the aircraft. For this reason, thorough inspection during production and careful maintenance of the aircraft are of prime importance. Control within the aircraft factory consists of inspection of the raw materials, such as bars, sheet metal, tubes, castings, forgings and so on; testing of the most important parts during manufacture to detect cracks and to control the heat treatment; and the final control of all parts, of components and of the whole aircraft. Maintenance inspection reveals cracks, corrosion and other defects of the most important parts of the aircraft.

After two years research work in the Universities of this country and elsewhere, there is need for a comprehensive review of the present position on the suppression of aerodynamic noise from jet engines. This report outlines the fundamental understanding of the problem that has been achieved, the basic experimental work done, and the noise suppression techniques which have been suggested.

A study is made of measured noise levels on advanced types of engines and an analysis is made of reductions required and so far achieved with the proposed noise suppression devices. While the basic principles underlying noise formation, both in subsonic and supersonic jet streams are beginning to be understood, the noise reductions so far achieved are still insufficient and warrant an extended programme of research.

The report includes helicopter noise analyses with pressure and pulse jets, and touches on the problem of structural fatigue in the vicinity of a jet stream.