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Aviation History
1943
1943 - 0185.PDF
JANUARY 2IST, 1943 FLIGHT 77 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. FIRST SPITFIRE FLIGHT Mistaken Impression CorrectedI AM anxious to correct a wrong statement which has beenwidely circulated in the daily Press. The initial flight tests of the prototype Spitfire were madeby Mr. J. Summers and not (as has been stated) by me. The first flight took place in March, 1936, and Mr. Summerswas then, a*nd still is, Chief Test Pilot to the Vickers Group of companies. The error has no doubt arisen from the fact thatMr. Summers granted to me the privilege Of flying the aircraft at its first public appearance in June, 1936, at which Pressrepresentatives were present. I would also iike to add that much of the development workon the prototype and later Spitfires was done by Mr. A. G. Pickering, who is still with the Supermarine works.As the first flight of the first Spitfire was undoubtedly an his- toric event, f should be glad if you would give due prominence-to the above facts. J. K. QUILL. BOMBER ESCORT Long-range Fighters or Longer-range Guns? I WONDER if I can help Mr. Condon in his problem of fighterescort? I can assure him that the time is not far distant when fighters will be able to escort bombers to the limit of theirjourney and back, providing it is profitable to do so. One must remember when a fighter is equipped with long rangetanks and necessary ammunition and gear it becomes a little slow in handling. Moreover, one has to bear' in mind thatwhilst the bomber may have an operational flight of, say, 1,000 miles, the fighter escorting it would have to have twice thatrange, if it wanted to have a real "set to" on the return journey. A given range at a steady 300 m.p.h. is not so expensive asthe same range with half a dozen dog fights thrown in ; once you start pushing the throttle through the emergency gate yourrange shortens. I think thu problem is being tackled on the right lines byfitting longer range guns to the bomber. Half a dozen cannon with, say, 300 yards range, are better than 16 machine guns of200 yards range, because, obviously, a fighter can (as has happened) sit outside the range of the bomber's machine gunsand just push holes inte it. It is not an easy problem, believe me, to fit cannon to a bomber; they are not easy to fit in amovable turret. The solution lies in longer range, larger cali- bre machine guns for the bomber rather than fighter escort forextreme journeys. I would add (without, I think, giving any secrets away) thatdespite all the talk that we British are far behind in certain types of aircraft, there are many pleasant surprises in store forthe public, and without offending any of our allies I think we 'can say that British aircraft of all types are second to none.In fact, I think British aircraft have led the world, and I honestly believe they will continue to do so. R. H. CORDERY. AN UNFORTUNATE CHOICE? Venturas in the Eindhoven RaidT HE Eindhoven raid is discussed by a correspondent in yourissue of December 31st, 1942. It is also mentioned else- where in that issue in connection with the Lockheed-VegaVentura. Twelve bombers were lost in that raid. I feel i:hat a large proportion of them must have been Venturas. A study of the three types engaged in the operation—Mos-quitos, Bostons and Venturas—leads one to the conclusion that the Ventura was an unfortunate choice.Bostons have already proved their worth in daylight bomb- ing attacks where their high speed and heavy armament ensurea minimum amount of time over enemy territory combined with good defensive as well as offensive powers. The excel-lence of the Mosquito for high-speed bombing in daylight is now well confirmed. About a fortnight ago I saw a really magnificent film of theraid in the news at a local cinema. There were some fine shots of Mosquitos and Venturas taking off, and the latter typeseemed terribly slow in the air by comparison. Films taken from the nose of one of the Bostons showed the crossing of theDutch coast, Bostons sweeping over enemy-occupied territory at o feet, and the run-up to the target, firing at Germangunners on the roof of the factory. Shots from the rear turret showed the bombs bursting on their objective. Throughout this brief but interesting film I had the impres-sion that the Venturas must have had a tough time if they had sought to emulate the antics of the Bostons. Like its youngerbrother, the Hudson, it is developed from a spacious airliner, and so is suitable rather for long-range reconnaissance overlarge stretches of ocean—where comfort for the crew is an important consideration—than for daylight bombing of enemyterritory where speed is the dominant factor. It is no reflection on the design or performance of the Ven-tura to say that it is not suitable for the type of job which it was called upon to carry out in the Eindhoven raid. Thismachine should be used in carrying on the traditions of the Hudson in convoy escort and anti-submarine work. S. W. GREENWOOD. BOOST PRESSURE VARIATION Behaviour of the Hercules IN reply to K. V. P.'s request for confirmation of the " risingboost phenomenon," I am not in a position to write regard- ing the Merlin but have noted the following average figuresduring the ground testing of Hercules XI engines. Upon reducing the engine r.p.m. from 2,400 to 1,800 bycoarsening the pitch of the airscrew, the boost invariably rises from about — ilb./sq. in. to — Jlb./sq. in.It should be noted that on this type of engine the lowest datum setting of the boost control is —41b./sq. in., so therecan be no doubt that the boost control is in action during the airscrew check. • Thus it would appear that there is a difference between thepressure operating the boost gauge and that acting on the boost control aneroid. To account for this is the fact that the con-nections for gauge and control are at different points on the induction system. In the Merlin, and, to a lesser degree, theHercules, the gauge connection is nearer the cylinder, along the path of the mixture, than is the boost control connection. Therefore, is it not possible that the back pressure, which,increases as the revs drop, is more pronounced on the gauge connection and the uncorrected increase is registered on thegauge? "FITTER HE.'" Factors Affecting Control AS "Navy Plumber" states in the December 31st issue ofFlight, the Merlin XX boost control is inoperative at zero boost, but this is not due simply to the action of the change-over cock; this only substitutes atmospheric pressure for boost when, the latter is insufficient to operate the relay. The pressure at which the b.c. will begin to control isdependent upon several factors, among which are aneroid spring stiffness, initial clearance between tappet and aneroidassembly, length of assembly and the clearances of the piston- .valve and relay piston, not forgetting strength of relay pistonbias spring. On many engines I have noticed that the relay piston beginsto travel towards the rear outer end of the cylinder when the boost is about +J lb./sq. in., hence it can only control at a.boost slightly greater than this pressure, or, of course, any higher pressure. In the October 1st issue of Flight, page 356, it was statedthat the maximum power altitudes of the Hercules III are 14,500 ft. and 15,000 ft. respectively in m.s. and f.s. gear, thepowers being 1,425 and 1,270 b.h.p. Should not the altitude given as 14,500 ft. read 4,500 ft., or some similar figure? Another rather interesting and similar question to that raisedby "Puzzled " arises in the case of the Merlin X. When run- ning at rated boost in m.s. a slight increase in boost is obtainedwhen gear change to f.s. is effected. This increase is more pronounced with engines which arefitted with partially worn boost controls. Although the con- trol may be adjusted to control at 5J lb./sq. in. in m.s., anincrease to 6 Ib./sq. in. may result when f.s. is engaged. My explanation is that, due to the greater pressure differenceacross the blower in f.s., leakage losses in the control increase
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