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Aviation History
1933
1933 - 1319.PDF
December 28, 1933 Supplement to FLIGHT Edited by C POULSEN December 28, 1933 CONTENTS Jiotes on the Design of Commercial Aireraft F.R.Ae.S I)e Bergue Patent Countersunk Rivetting Process The Design of Aerofoils and the Prediction of Characteristic W. R. Andrews, A.F.R.Ae.S Technical Literature— Summaries of Aeronautical Research Committee Reports .. By W. 0. Manning, By Page K.-> 88 91 NOTES ON THE DESIGN OF COMMERCIAL AIRCRAFT By W. O. MANNING, F.R.AE.S. Mr. Manning, as most of our readers will be aware, is one of the pioneers of British aircraft, designers, his experience dating back to the "heroic " years of 1910-11 and extending up to comparatively recently. Mr. Manning is not nowadays a professional aeroplane de signer, in the sense that he is not connected with any particular firm as designer. His views on the subject of design are, therefore, entirely unbiassed, which may account for the fact that they are usually very refreshing to those of us who are submerged in the subject every day.—ED. TAKING first the question as it concerns commercial aircraft, there is no doubt that progress in these machines is in the direction of improving speed and comfort, but the importance of speed on the various aircraft routes depends necessarily on the nature of the traffic and on the speed of competing methods of transport. Take, for instance, the London-Paris route. The distance is about 260 miles, and the best train and boat time is about 7 hr., with an average of less than 40 miles an hour. This is rather slow, but the trans ference of passengers from train to boat and boat to train, combined with the slow steamship passage, necessarily takes time. The Imperial Airways time is 4 hr. from the London depot to the Paris depot, giving an average of about 63 miles an hour. If the Channel tunnel was in existence, the train speed between the two capitals would probably be in creased to an average of at least 55 miles an hour, re ducing the time now taken between them to about 4f hr.; or only three-quarters of an hour more than the time taken by the air route. If this happened there is no doubt Imperial Airways would require much faster aeroplanes if they wanted to keep their traffic. The influence of the factor of the comparatively slow speed of the competitive route is reflected in the design of the Imperial Airways machines, for if an advantage •of three hours in time taken is enough to attract the necessary traffic, why trouble to fly any faster? Especially as the slower machine has an advantage over the faster in the amount of pay load it can carry on each trip. The conditions in the United States of America are quite different; here the air route has to compete with an excellent train service, so that in order to attract traffic the speeds of the machines used must be high. In fact, the latest types used tliere can cruise at about 170 miles an hour. It is of great interest to contrast the types of aero planes used here and on the American services, espe cially as the conditions are so different, but in doing so it should be remembered that, while there are many large American operating companies, there is only one large English one, so that there is a larger demand for new types in America than there is here. The bulk of the Imperial Airways traffic is still carried by the " Hannibal " class, which is characterised by its large pay load, moderate speed and four engines. This number of engines is considered important from the point of view of safety, and British passengers have been educated to believe that security resides in a much subdivided power plant. The, older " Argosy " class had three engines only, and this number is con sidered here to be the minimum for a passenger air liner. Imperial Airways are one of the only large air operating companies which still use biplanes; though the most recent design used by them in Africa is a monoplane, the " Atalanta " type, they have reverted to the biplane in the new machines now being built by Short Bros. I am personally of the opinion that the monoplane is the type of the immediate future. Not only does the monoplane offer the advantage of great cleanliness in design by eliminating the struts and bracing of the conventional biplane, but it also possesses the advan tage of reduced upkeep cost, as there is so much less structure to be maintained in good order. It would be reasonable to suppose, therefore, that the future machines of Imperial Airways will resemble the " Atalanta " type, though the provision of four engines on a monoplane is always a difficulty. If they are arranged in tandem, as in the latest Fokker, there is a sacrifice of propeller efficiency, which means a loss of thrust which is especially serious when the aeroplane is taking off. Alternatively, the wing has to be cut up with a number of engine nacelles, which is bad from the aerodynamical standpoint. 1310 a
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