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Aviation History
1948
1948 - 0729.PDF
MAY 20TH, I948 FLIGHT CORRESPONDENCE The Editor does not hold not necessarily for tyr^euoy correspondents. The names and addresses oj then, must in all cases accompany letters. . LIGHT AIRCRAFT ENGINES The Two-stroke is Worthy of Consideration REFERRING to Mr. A. G. J. Brown's plea in Flight of XV May 6th for the development of a 40-50 h.p. light aircraft engine, I would like to suggest once more that there is still a lot to be said for the simple three-port air-cooled two-stroke type of, say, the four-cylinder variety, with a cubic capacity of about 2 litres. Is it too late to suggest that an up-to-date design of thistvpe be developed and thoroughly flight-tested to find out what it really will do? To my mind, it still seems well worthwhile, particularly from the viewpoint of economy in manu- facture which the type offers. Even if it is desired to add a small amount of complication in the interests of higher output, some very interesting pos- sibilities arise with the application of the Kadenacy system ul ballistic charging. The simple two-stroke can play the same part in light avia- tion as it has done for the past thirty-five years in light road and water transport. Will it be given the opportunity? Farnborough, Hants. C. F. CAUNTER. MULTI-WHEEL UNDERCARRIAGES " Comparator " is Challenged to a Friendly Wager "/COMPARATOR" may come out from behind his flimsy v^ disguise of a new nom de plume. Who, as he himself might ask, does he think he is fooling with his stratagem? Could anyone believe that this literaTy shadow-boxer, who employs with such facility the techniques of a London Univer- sity student, an English aeronautical engineer, a Hollywood publicity man and a 42nd Street columnist, could be any other than . . , ? But we shall desist in deference to an apparent editorial wish. What I really wanted from "Comparator" was an explana- tion of why he selects for criticism the single-wheel undercar- riage system of the Convair XC-99. Is he riot aware that this is a temporary arrangement, that production versions of the B-36 (the bomber twin of the XC-99) already have quadruple main- wheel assemblies, and that similar gear is proposed for any future "99s" civil variants? As for British landing gears being "a jump ahead of the Americans" I am prepared to gamble a silver dollar—or, should "Comparator" prefer them, two cupro-nickel half- crowns—that, following the experience of Consolidated-Vultee, the Brabazon will eventually appear with several more wheels or with a redesigned main undercarriage. Kingston, Surrey. "IMPERATOR." DIESEL ENGINES FOR AIRCRAFT Questions of Combustion and CompressionR EFERRING to the letter from Air Commodore Banks in your Correspondence column of May 6th, I feel I must correct the mistaken impression which that letter gives about the diesel aircraft engine's efficiency. It is absurd to say that a diesel engine only burns 80 per cent of the air whereas the petrol engine burns 100 per cent. As a matter of fact, it is only the oxygen in the air which is used, and as there is only about 25 per cent of that combustible in the air, it is difficult to see how the petrol burns 100 per cent of the air as the 75 per cent of nitrogen does not burn. liven the diesel engine will not burn 80 per cent of the air, in spite of its very high supercharging and compression which is very much more likely to burn up all the air than is the petrol engine, with its comparatively low compression pressure, viz., 300 lb/sq in against the diesel's 650 lb/sq in. Total diesel combustion pressure 1,450 1b, petrol total 800 1b. What might be meant is that the two-stroke diesel gives 80 per cent full power against the four-stroke petrol engine which, as it only gives a power stroke every other revolution, gives 50 per cent full power. This means that the petrol engine gives in each stroke 100 per cent power, whereas the diesel engine two-stroke gives in each stroke 90 per cent power. But ax the diesel gives double the number of power strokes, it should also be 30 per cent lighter than the petrol engine, which1 think it most probably will be very soon. . -^gain, as the diesel engine does not use a fuel which over- h the engine, as high-octane petrol does, it can operate at 80 per cent full throttle, whereas the petrol engine canonly operate at 60 per cent when cruising, otherwise it over- heats. The diesel aircraft engine will give a higher cruising The petrol engine is very wasteful in all directions. Its ex-haust gas temperature is actually 1,650 deg Fahr., whereas the exhaust gas temperature of the diesel engine is 950 degFahr. only, which is hardly red-hot iron heat. Heat, it must be remembered, is power. The flash point of petrol is 30 deg Fahr. below freezing point, which means that it is constantly giving off vapour, especially in hot climates, and as this vapour is explosive it is. of course, sheer madness using such a fuel on air liners. A railway company will not allow even a sealed tin of creosote to be carried in the guard's van or any part of the train. This is the law of the country and Was instituted by past experience. It is very noticeable that trains never catch fire in a crash It is also noticeable that when an aircraft does not happen to catch fiie in a crash, very few people are killed. Hardly anybody, in fact, as everything one bumps against is of a light nature and gives considerably. I have had it. Again, the exhaust gas of petrol is very poisonous as it contains 5 per cent carbon monoxide, whereas diesel exhaust only contains 1 per cent so that it is practically non-poisonous. A leak into the cockpit of a single-engined petrol aircraft will cause the pilot to pass out in 15 minutes. Many accidents have been caused by this. It is obvious by these few remarks and figures that the diesel engine is infinitely superior to the petrol engine for civil aviation. Especially considering that the fuel consump- tion is 20 per cent less and is a third of the price. Engineers of long standing in engine-building firms agree on this. To say that it will take ten years to develop a diesel aircraft engine, when it is already developed for aircraft use and weighs only 1 lb per h.p. against the petrol engine (which weighs 1.3 for the Rolls-Royce Griffon or the Bristol Hercules) shows a lack of knowledge of engineering production. Westcliff-on-Sea, Essex. J. R. GOULD. [Evidently the writer of this letter is not aware of the work of Air Commodore Banks, or he would not accuse him of a lack of knowledge of engineering production.—ED.] FORTHCOMING EVENTS May 21st.—Institute of Navigation : " Meteorology in Aviation : Is it Obsolete?" Francis Chichester. May 22nd and 23rd.—Shannon Aero Club Rally. May 24th to 29th.—Aircraft Exhibition Cardiff. May 27th.—Royal Aeronautical Society : Wilbur Wright Memorial Lecture. A. Gouge, B.Sc, F.R.Ae.S. May 29th and 30th.—Netherlands Aero Club Invitation Rally, Ypenburg. Holland. May 29th and 30th.—Butlin's Week-end Air Rally. Speeton, Filey, Yorki. June 5th.—Cardiff Air Disolay. June 5th Derby Aero Club : Flying display at Burnaston airport. June 12th.—Wolverhampton Aero Club " At Home." June 12th and 13th.—Butlin's Week-end Air Rally at Ingoldmells, Skegness. June 13th.—Henri Bardel Cup for model aircraft with mechanical motorc. June 19th to 21st.—Royal Aero Club Week-end for Foreign Guests London. June 26th and 27th.—Butlin's Week-end Air Rally. Broom Hall, Pwllheli N. Wales. July 3rd to 5th.—Private Air Rally for members and associate members of the Royal Aero Club at Oeauville, France. (Guests of M. F Andre.) July 3rd.—R.Ae.S. (Glasgow) : Visit to Blackburn Aircraft Ltd., Dum barton. July 17th.—Southend-on-Sea Air Rally. July 19th to 31st.—Swiss International Gliding Competitions, Samaden. July 24th to 26th.—Private Air Rally for members and associate members of the Royal Aero Club at La Baule-Escoublac, St. Nazaire. (Guests of M. F. Andr«.) July 31st.—Aero Club of Orange, Air Rally. July 31st to Aug. 8th.—International Model Aircraft Meeting, Eaton Bray, Beds. Aug. 1st.—Boroden Cup for Model Aircraft with mechanical engines, London Region. Aug. 7th.—Air Meeting and Competitions at Ypenburg, Holland. Aug. 27th to Sept. 5th.—Aero Club de France. " Tour de France." Aug. 28th and 29th.—Cinque Ports Flying Club. International Flying Meeting. Lympne, Kent. Sept. 7th to 12th.—S.B.A.C. Exhibition and Display, Farnborough airfield, Hants. Sept. 18th to Oct. 3rd.—Copenhagen Show, organized by the F.B.I. Oct. 15th to 24th—Third International Aircraft Exhibition, Forum Ex- hibition Hall, Copenhagen.
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