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Aviation History
1946
1946 - 1910.PDF
326 FLIGHT SEPTEMBER 2f>TH, I946 Speeds and Mach NumbersS OME confusion appears to have arisen in connection with the proposal to put the de Havilland 108 and Supermarine E.10/44 over tne sPeed course off Littlehampton. The world's speed record of 616 m.p.h. established by Group Captain Donaldson on a Gloster Meteor cannot be improved upon with that machine until better weather conditions obtain, such as less bumpy air and a higher temperature. The de Havilland 108 has now passed all its frying tests, and it is logical and desirable to try it out over the course so that exact speed figures can be obtained. The 108, with its swept-back wings, should have a higher Mach number than trie Meteor, and from this fact there are some who have jumped to the conclusion that it is faster. This does not, of course, necessarily follow. The higher Mach number merely means that the machine carf be pushed to a greater speed if there is sufficient thrust. No doubt the de Havilland company has a fairly good idea of what the Mach number is at which compressi- bility symptoms begin to appear. Even if the speed at which this occurs cannot be reached in level flight, due to insufficient thrust, it can be ascertained fairly readily in a comparatively shallow dive. The static thrust of the Goblin jet unit, as used in the Vampires, is about 3,000 lb. Doubtless this can be increased for short durations such as those involved in the four runs over the course. It is obviously desirable to ascertain the exact drag coefficient of the machine, and if the thrust is known and the speed accurately determined, the drag at that speed is the same as the thrust. From this it is possible to extrapolate the drag CONTENTS The Outlook Towed Tailless Here and There Lincolns at Lindholme Flight in the Nene Lancastrian Civil Aviation News - A Fairey Party Echoes of Radlett The Hurricane Correspondence Service Aviation 325 327 331 333 336 340 342 343 346 348 349 at higher speeds until the Mach number is reached, when the drag ceases to follow the square law. In view of its very clean shape and small size, it may well be that the 108 will equal or exceed the Meteor record. But even if the thrust of a single Goblin is not- sufficient to enable it to do this, the test will have been very well worth while on account of the exact informa- tion which it will provide. That is of far greater im- portance than the actual speed attained over the course. . Less is known about the Vickers-Supermarine E. 10/44 • which was so admirably demonstrated at Radlett by Jeffery Quill. That it is very fast indeed was obvious, • but the most surprising thing about it was, perhaps, its relative silence. Chinese philosophers deem silence a virtue, and in flying, too, it may be a token of inner strength under strict control. After all, to make noise, absorbs power. The Supermarine has the urge of a Nene unit, and its wings, although not swept back, are" extremely thin, so it may be as fast as the 108 even if. its Mach number is lower, f^jfc CCD t^ CHEATING TH& WIND: Anexclusive \ Flight jjhotcgraph of Jack Olvery a Napie/Develop-ment Flight test -pilot, flying a Sabre-engined Tempest fittedwith the new Napier hollow spinner, an ingenious device forincreasing intake area without incurring extra drag. The normalcowling is extended by a separate annu'ar skirt enclosing the bladeroots.
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