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Aviation History
1927
1927 - 0642.PDF
AUGUST 25, 1927 ailerons to be inside the outer interplane struts. It is probable that a stiffer structure can flutter only at the higher speeds, as wing flutter depends, in part, on the elasticity of the wing structure. Performance Testing Much attention has been paid to the analysis of performance tests to the effect of body interference on airscrew performance, and a formula has been deduced for the body resistance due to the slip stream. Performance Wind tunnel tests on high-speed seaplanes have been made at the N.P.L. The methods of performance testing have been under review, and a new method put forward by Mr. Capon has been adopted for research purposes, and has been accepted by the industry. Difficulties arose in connection with the adequate calibration of instruments, and have now been overcome. A Martlesham report deals with the power of the normal engine. It has been generally assumed that the engine power was a function of the pressure only ; these experiments suggest that a function of the pressure to the two-thirds and of the density to one-third power gives a closer approximation to the truth, and the whole matter has been made a subject for further experiment. Load Factors for Fin and Rudder With regard to the proposed Air Ministry memorandum specifying certain minimum requirements for rudder power and volume, in view of the fact that these would, in many cases, involve an increase in the combined area of the fin and rudder, and a consequent increase in the side load on the fuselage, a modification was suggested in the existing formula for calculating the side load, which amounts in effect to a reduction in strength of about 26 per cent. The Design Panel decided there was no definite evidence supporting the assumption that fuselages calculated by present methods are unduly strong, and that unless the larger fin and rudder involved a serious addition to the structure weight if the existing formula was retained, it would not be advisable to authorise the proposed modification in estimating rudder loads. Comparison between French and British Methods of Stressing An opportunity will probably occur for making comparative strength tests on a certain machine by both French and British standard methods. Tractor and Pusher Airscrews A paper on this subject reports that, provided that efficient nacelles are designed, there is no reason to believe that pusher airscrews will be less efficient than tractors. Vortex Theory of Airscrews In recommending a report on this subject the Vortex Panel stated that careful consideration had been paid to all available evidence, and the conclusion reached that the vortex theory of airscrews had reached a stage where it can be applied to design with confidence. Scale Effect The Society of British Aircraft Constructors has suggested that in connection with full-scale testing of wings of different form, accurate results could be more rapidly obtained if. instead of using a Bristol Fighter for the purpose, as at present, a parasol monoplane could be constructed, capable of incorporating any particular wing section which it is desired to test. High-Speed Aircraft The question of further increasing the maximum speed obtainable in high-speed machines has been dealt with. During the test of a particular model in a tunnel, a surprising increase of lift coefficient was found over that of the wings alone, which was attributed to the fairing of the wings into the fuselage delaying the development of stalling of the centre section. With regard to engine drag, it seems possible Col. Minchin Ready COL. MINCHIN brought his Fokker monoplane over from Amsterdam on August 18, accompanied by Mr. Leslie Hamilton, and went on to Bristol to have the " Jupiter " tuned up. They are attempting the Atlantic flight shortly. Tunbridge Wells Air Pageant THIS was postponed on August 20 owing to bad weather. It will take place on August 27. The Mayor (Alderman Charles Westbrook) and Sir Robert Gower, M.P., President of the proposed club, will make flights. " Moths " will take that for racing machines, the air-cooled engine will not compare favourably with a water-cooled engine using wing radiators. Airscrews Working at High Tip Speeds Tests made on aerofoil sections at speeds up to twice the velocity of sound suggests that the shape of the most efficient aerofoil for use at such speeds differs considerably from that suitable for the ordinary range. Autogiro Further work on this type of machine has proved that the performance in top speed and rate of climb was not so good as that of a standard Avro of the same weight and with the same engine. But the advantages of the Autogiro, that is, its low minimum gliding speed and its ability to land at steep angles, were fully demonstrated. Instruments An instrument has been developed which records the true angle of flight path of an aeroplane independently of atmos- pheric currents. It is important, as a means of eliminating the effects of air currents on the full-scale measurements of lift and drag. The design of an instrument as a recording angular accelerometer for certain experiments on stalled flight has been recommended. Fire Prevention Progress in this direction is difficult, owing to the lack of exact knowledge as to the causes which lead to the ignition of the petrol vapour set free in a crash. In the case of single- engined machines, it is certain that the fireproof bulkhead between the engine and pilot has resulted in a saving of life on more than one occasion. The problem is more difficult in multi-engined machines. The fireproof bulkhead should be fitted if one engine is in the fuselage, and in the case of the engines on the wings, the petrol tanks should l>e placed so that petrol will not fall near an outlet of the exhaust. Fire risk may be lessened appreciably when a heavier fuel is used. Research is proceeding on the development of engines to burn heavy oils. Attention is being given to the recommendation of a type of fire extinguisher capable of use with one gloved hand and readily operative. Elasticity and Fatigue At the N.P.L., the previous experiments on the deformation and mechanism of failure of single crystals under static and repeated stresses is being extended to include specimens consisting of several large crystals. At the R.A.E., a funda- mental theory associating failure of metals under static and repeated stresses with complex phase changes is being further developed and subjected to critical experimental tests, Prof. Jenkin, of Oxford, is continuing high-frequency fatigue experiments. Prof. Mason is investigating the correlation between the endurance limit and the cyclic strain of specimens subjected to reversed tending stresses. Prof. Lea is working on the failure of metals under combined stresses. A report by Messrs. Gough and Wright, of the N.P.L., gives an investi- gation into the crippling strength of thin sheet metal used in aircraft construction. Light Alloys The use of magnesium allovs for aircraft purposes is being steadily developed, and these alloys appear to offer great possibilities. Some have excellent rolling and forging proper- ties. Corrosion is a difficulty, but marked improvement has been obtained in more recently prepared material. Engines Problems of detonation and fuel economy become increas- ingly important. It is possible to run the high compression and supercharged engine on " doped " fuels, but this involves the search for more suitable dopes than are at present avail- able. With airship engines, pending a general review oi compression-ignition engine research, the use of gaseous fuels is being considered. <*> <£» part in the meeting, and formation flying will be given by the R.A.F. Convenience of Flying MR. NORMAN HULBERT, Secretary of the National Funa for the Promotion of Aeronautics, found it necessary to gt-i to the West of England rather quickly, and the De Havillanc Company loaned him a " Moth " on very reasonable terms f<;* the purpose. He reached Shrewsbury from London uj about 1 hr. 10 mins., and for the double journey, the petrc. consumption was about eight gallons. 594
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