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Aviation History
1951
1951 - 0819.PDF
FLIGHT CORRESPONDENCE The Editor of "Flight" does not hold himself responsible for the views expressed by correspondents in these columns. The names and addresses of the writers, not necessarily for publication, must in all cases accompany letters. The First Intentional Spin?O NE becomes chary of claiming a "first" in aviation, but I sub- mit to the challenge of your readers that S/L. J. C. Brooke (now retired) was the first man to make an intentional spin. The place was over Killingholm, near Grimsby, and the date 1915. The aircraft was a Sopwith two-seater scout, popularly known as the "Spinning Jenny." In this type, many pilots spun involuntarily, as did S/L. Brooke on one occasion; but, unlike the others, he managed to come out of the spin. The next day, with witnesses which included Norman Blackburn, he Hew to 3,000ft and made two deliberate spins, losing 1,000ft on each. The method of going into the spin was interesting: the pilot put the machine into a tight spiral and gradually throttled back, thus inducing a spin. The idea of a stall followed by applied rudder came later. Whilst "every schoolboy knows" who made the first loop, and the vogue which it led to (not forgetting Claude Grahame-White's Upside-down Dinner, starting with coffee and liqueurs and ending with soup), the nearest to fame the inventor of the spin achieved was a stiff admonition from his CO. and a narrow miss at a court martial. London, W.i. B. J. HURREN. Ice FormationI N the article on the Qantas DC-3 "Rain Trainer" (April 6th) there appears to be some confusion of thought concerning the causes of ice accretion upon aircraft in level flight. It was stated, "when an aircraft is flying above freezing level in the presence of snowflakes or ice crystals rime ice may be expected to build up on it. During flight above freezing level through rain of the non-freezing type, in which no ice is present, an accumula- tion of clear ice may be expected on the aircraft." Neither ice crystals nor snowflakes are, in fact, sources of air- craft icing, unless perhaps they are encountered together with supercooled water drops in quantity. Ice formation on an aircraft flying above the freezing level results from the disturbance by the aircraft of supercooled water drops. These drops will normally be cloud particles, though, under certain conditions, they may include supercooled falling raindrops. When a supercooled water drop is disturbed by an aircraft, part of the drop freezes immediately upon surfaces such as the leading edges of aerofoils. The solidification of this part of the drop is instantaneous and small air bubbles become imprisoned in the ice, which is therefore of the "rime" type. The latent heat released in the formation of the rime ice raises the temperature of the remainder of the drop to 32 deg F. This water flows back beyond the leading edge and freezes in somewhat more leisurely fashion upon the flat upper surface of the aerofoil. Here, however, there is no complication with air bubbles, and the ice which forms will be hard and clear. The greater the degree of supercooling, the greater will be the proportion of each water drop that freezes upon impact as rime ice. Therefore, clear ice may be expected to build up most rapidly in the region of least supercooling, immediately above the freezing level, especially if the water drops there are large and water for ice formation is available in considerable quantity. Dorchester, Dorset. D. J. PAXMAN. Sailplane Airworthiness Requirements I WAS very interested to read, under the heading "A Sailplane'sNationality" (April 6th), that the inclusion of the anglicized version of the D.F.S. Meise sailplane in the Festival of Britain Exhibition was to be the subject of questions in the House by a Yorkshire M.P. While the origin of the questions is fairly obvious and I have every sympathy with Elliots of Newbury, Ltd., it would appear that, after some 5,000 hours of labour in re-designing an already successful and well-tried sailplane created by German experts at great expense, the satisfaction of the British airworthiness requirements for sailplanes seems to have resulted in a weight increase of some 120 lb over the original German design. It is also rather odd that, by these same British standards— brought into effect after the war, with little or no background of sailplane research work in this country—the German Meise is not considered by our airworthiness authorities to be a safe vehicle in which to enter cloud, i.e., the job which all sailplanes are intended to do. It follows, therefore, that this state of affairs must also apply to the German designed and built Weihe sailplane—constructed to the same standards as the Meise—in which Mr. Philip Wills so recently achieved his well-deserved award of the Britannia Trophy by darting into every nasty-looking cloud he could find. I am glad, indeed, that he has survived to tell the tale after using for this purpose a machine which is considered by our airworthiness experts to be so inadequately stressed for this type of flying! It would have seemed a commonsense plan after the war to have adopted the existing German sailplane strength requirements as they stood, in view of the fact that these engineering standards had been evolved over many years of great expenditure and practical experiment in the Fatherland. If this course had been adopted, our home-designed sailplanes could now presumably compete with those built elsewhere—on more favourable terms as regards weight than at the present time. In addition, the building in this country of any of the family of highly successful German sailplane designs would only necessitate the conversion of the specified German materials to equivalent English ones, which is a fairly easy process. As it is, the cost of the complete re-design of any of the well-tried machines such as the Grunau Baby, Meise, Weihe, Kranich, etc.— the drawings of which were handed to us on a plate after the war— is a very heavy one, and must be passed on to the customer. Worthing, Sussex. SPLITPIN. Airspeed and Tricycle-undercarriage HistoryT HE letter from Mr. R. E. Hardingham of the A.R.B. Flight, April 13th) was both interesting and informative, and it was kind of the member of his staff, whose remarks he includes, to point out the few inevitable "slip-ups" in my original letter. I was aware of the original British registration of Mr. C. T. P, Ulm's ill-fated Envoy; in endeavouring to meet space limitations I purposely omitted the information. The error in Mr. Ulm's initials was a typing one to which I must plead guilty! Referring to the third paragraph of my original letter, I find the registration letters of one of N.E.A.'s Couriers is incorrectly given as G-AVGC. This, of course, should have read G-ACVG and appears to be a printing error, since my copy quotes the correct registration [this is so—ED.]. Regarding Envoys sold abroad, the four which went to South African Airways in 1936 were ZS-AGA,; B, C and D. According to a South African correspondent of mine, ; all four were impressed into S.A.A.F. service in 1940, and by \ 1945 all had been written-off as a result of service in the Union. \ One last point concerns the interesting comment, on the revival j of tricycle undercarriages, by Mr. P. H. T. Green in his letters on ; March 16th and April 6th. The G.A.L. project which appeared 1 in 1937 was known as the G.A.L. Type 29B. I do not wish to ; dispute the G.A.L. claim put forward by Mr. Green, since this \ is confirmed by a very detailed history of General Aircraft, Ltd.,; which appeared in The Aeroplane Spotter in 1948. It seems that only lack of Government backing prevented the further development of tricycle undercarriages by this company back in i936-37» ^le*r t*len chief designer, Mr. D. L. Hollis Williams, was primarily responsible. So far as tricycle development in the U.S.A. is concerned, few people in this country, or even in America, realize that a part mock-up of the original DC-4 Sky- master with its then "revolutionary trike" design appeared as early as 1935, although, of course, the prototype aircraft (NX-18100) did not fly until Jajiuary, 1938 (this information did not originate from American "sources). The first DC-4 project was a "hush hush" affair until mid-1937, when first official details were released by the Douglas company. • Prestwick, Ayrshire. DENNIS M. POWELL. [The feature article on airspeed history which was published in Flight of February 23rd has clearly aroused great interest; but unless any new point of exceptional interest crops up we cannot devote any further space to correspondence on the subject.—ED.] The Canberra's Radio "PROM your issue of March 9th (p. 281) I see that the Canberra's F Atlantic flight is claimed to be the first occasion in which the R.A.F. have used the successors (AD 107/8 and AD 7092A) to the well-tried T.1154/R Marconi radio equipment. I believe this to be incorrect, since I recall that when No. 31 Squadron, Transport Command, operated de Havilland Doves (not Devons) on V.I.P. work from Hendon in 1949, these aircraft had the AD 107/8 and AD 7092A civilian equipment. This gave us a considerable supply problem, since, being non-standard so fat as the R.A.F. was concerned, it required special new stores :if>" test equipment from the signals section. St. Andrews, Fife. M. T. SMEDLEV
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