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Aviation History
1943
1943 - 2015.PDF
AUGUST 12TH, 1943 FLIGHT 181 CORRESPONDENCE The Editor does not hold himself responsible for the views expressed by correspondents. The names and addresses of the writers, not necessarily for publication, must in all cases accompany letters. POST-WAR AIR TRANSPORT * Provincial Airfields Must Follow London's Example 'PHE plans of the proposed new £20,000,000 pbst-war London X airport are, indeed, a model of perfection and fully justify the high praise and acclamation accorded the general outline of the scheme. What are the provincial authorities doing in connection with this great British civil aviation expansion programme? So lar, there has not been news of any worth-while activity on their part, and I do feel that it would be a serious drawback to the progress of air transport development if some of our air- ports became quite inadequate to cope with the increased traffic occasioned by the giant liners of coming years. In support of my statement, 1 would like to mention the words of Captain K. Bartlett, a director of the Bristol Aero- plane Co., Ltd., who says that "there is a future lor flying boats in areas where airfields have not been developed, and where weather and sea conditions do not hamper their use." With the rapid growth of air travel, which is bound to materialise after the war, the "feeder" system—operated from the network of airfields in this country—will undoubtedly have to resort to larger aircraft, or, alternatively, be abandoned, thus making each route a main line. ERIC LORRAINE ADLEM. BOMBER ARMAMENT Most Important Point Overlooked TT7ITH regard to the controversy about bomber armament, VV it seems to me that all your correspondents so far have overlooked the most important point of all—whether there would be any advantage obtained by fitting 0.5m. guns in our bombers. The heavily armed American bombers were designed specific- ally for daylight operations, and the conditions which are most suitable for them to operate in are also those which are most suitable for enemy fighters. Good visibility, which is essential for the daylight operations, enables the enemy to spot the bombers while they are still a long way off; also the Fortresses are unable to make use of cloud cover, for they cannot operate on cloudy days. There- fore they must rely for defence on the fire power of their guns *fnd also to some extent on the close defensive formation they fly in. Consider now the conditions which are most suitable for our heavy night bombers, namely, thick cloud to and from the target. Any night lighter-pilot will tell you that if his first attack fails he rarety gets a chance for another one. Hence most night fighters are heavily armed and close in to as near the enemy as possible so as to get the best possible effect from their burst. The 0.303m. machine-gun is then a very efficient defensive weapon, with its high rate of fire, which will tend to throw the enemy off his aim. * By all means let us have heavily armed bombers, but let us be sure first that we are using the right weapon for the job. HARRY ARCHER. v ONE-TYPE TEST PILOTS M.A.P. Red Tape that Limits Experience '"PEST pilots, other than a firm's chief test pilot, are unable -•- under present arrangements to gain experience on other firms' types except by surreptitiously circumventing the several yards of red tape which at present control testing. Only firms' chief test pilots are "on the list" at Service Experimental Establishments for flying new types, and other test pilots must obtain M.A.P. "Approval" for (a) type of aircraft, (b) airfield to be used, and (c) type of flying to be done, before they can so much as start up an engine of some- body else's aircraft. Approval normally takes anything from three weeks to three months to obtain, though temporary approval can be given by a firm's M.A.P. Overseer in urgent cases. This position is ludicrous! It is surely to everybody's advan- tage for all test pilots to have as varied experience of types as possible. Could not the S.B.A.C. or some similar organisation create a liaison between firms or between firms and the A.T.A. whereby "A" company's pilots could fly "B" company's products without entering into the tangle of official approval red tape? If such a scheme could be made workable (and the writers suggest that it certainly could), all the firms concerned would benefit from the more numerous criticisms and sugges tions from their own and other lest pilots, and the pilots them- selves would have a far wider outlook on the desirability and suitability of various features in different aircraft, and would therefore become more useful in their profession. The counter-argument that production pilots are not required to know any other standard than the machine they are currently testing is responsible for the present conditions in which the number of really first class test pilots is rapidly diminishing by the process of elimination, and the pilots who take their place have not had the opportunity of getting the varied experience so desirable in a test pilot. This tendency on the part ol chief test pilots to prevent the production pilots from attaining their own standard of experience is a selfish and short-sighted policy into which firms should not allow themselves to be drawn, and may have a very grave effect on the future of the British air- craft manufacturing industry. The lault will lie partly with the industry itself and partly with the Ministry for having so much red tape. How many times has one been asked, when handing a machine over to a ferry pilot, "How does it compare with a Spit. ? " and all one can reply is that one hasn't flown a Spit., or whatever type he happens to choose. THREE PRODUCTION TEST PILOTS. REVERSIBLE-PITCH AIRSCREWS Comparison with V.P. Marine Screws B . HAMPTON COURT" (in your July 20th issue) has justnot bothered to explore the maze. He accuses me of ignoring the very elementary fact that when the pitch is reversed the relative camber is reversed too, and bases his whole argument against "negative props" as landing-run shorteners on this alone. But 1 could have told him a much better reason to aigue that reversed airscrews would not be fully efficient: namely, that by ihe time you had got a de- cently negative pitch on the main body of the blade, the tip would be almost fully feathered, and, therefore, very inefficient indeed (because the tip, having much less positive incidence than the root and middle of the blade, would- go into negative, while the root was still in positive or "normal" pitch). It is for these two reasons that, in the letter to which he objects, I referred to the use of "negative props " on the ground only, at comparatively slow speeds, because: — (1) In accelerating from rest to, say, 50 or 70 m.p.h., your "normal props" are shockingly inefficient atiyway. (2) You can get "up a good acceleration even in " positive coarse" ; indeed, I have seen a Blenheim IV take off at Gib- raltar, of all places, in "positive coarse" pitch, which means that the airscrews were pretty well stalled—"all drag and no lift." (3) Providing the carburation allows it, you can fly almost all aircraft (ancient and modern) upside clown indefinitely—so the inefficiency of 'negative camber." can't be so very con- siderable. . (4) A few pages before Mr. "Hampton Court's" letter you have an item on the new Rotol v.p marine screw, which is clearly of reversible pitch, and is used in that manner to make ships stop dead or go backwards; in fact, ships not only ie- verse the camber of their screws, they even dare to reverse the crankshaft and use the trailing edge of the propeller blade as a leading edge—and they still get along. (And with a marine v.p. screw-the problem of the blade tip becoming "very nega- tive" when the rest of the blade is only just negative is ob- viously greater than with an airscrew owing to the much greater rate of pitch washout towards the tip.) ' (5) Lastly, " B. Hampton Court's" statement that the use- ful power from a reversed airscrew is "incomparably lower " than that of a normal airscrew is just a bit of unproved and unconsidered generalisation. The only person who can give a really satisfactory answer to this question is one of the pro- fessional wind-tunnel wallahs, whose comment I hereby earnestly invite. "DRIVER."
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