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Aviation History
1946
1946 - 1589.PDF
AUGUST 15TH, 1946 FLIGHT 107 9,712 lb. The span is 43ft, length 41.4ft, and gross wing area 374 sq. ft. Should the full 8,400 lb thrust be used for climb, the Meteor, according to a rough calculation by Mr. Carter, would impeller accelerates from an idling speed of 2,500 r.p.m. to 15,000 r.p.m. in less than four seconds. For the Herne Bay attempts the Der- wents were tested" in cycles of. five initially ascend at 10,000ft /min. At the high Mach numbers which the Meteor IV now attains the drag curve is beginning to rise sharply and every mile-an-hour increase costs dear in thrust. As usual, Rolls-Royce have responded nobly to the de- mands of the airframe designer and have developed the Derwent V tur- bine-jet to deliver 4,200 lb. Thestan- minutes at 3,000 lb thrust, followedby two minutes at 4,000 lb thrust. Thirty consecutive cycles were com-pleted satisfactorily before the units were cleared. Recent tests havebeen even more severe. No fewer than sixty cycles have been com-pleted, consisting of two minutes at 3,000 lb thrust, two minutes at3,500 1b thrust and one minute at A Meteor IV of the High-Speed Flight is inspected before a test flight on which speeds exceeding the present record were attained. dard Mark V Derwent, as installed in R.A.F. Meteors, is rated at 3,500 lb, and for the Herne Bay attempts the special units, although capable of delivering 4,000 lb, were adjusted to give 3,600 lb. Essentially the Derwent Vs for the High-Speed Meteors are standard units, but advantage has been taken of some notable metallurgical developments the nature of which is still secret. The new metals, one of which is used for the turbine blades, have enabled the gas temperature in • the cycle to be raised with safety and allow a rotational speed of 15,200 r.p.m. (the normal figure is 14,600 r.p.m.) and a jet pipe temperature of about 750 deg. C. At the special rating the Derwent has a specific fuel consumption of 1.07 lb/lb/hr, or something-like 750 gallons of para- ffin an hour. The thrust / weight ratio is of the order of 0.3 lb/lb-thrust. Seeking to interpret some of the technical data relative to the Derwent, Rolls-Royce point out that at 600 m.p.h. the thrust of 4,200 lb is equivalent to more than i2,oooh.p., allowing for the loss in efficiency of an airscrew at this speed. They explain that the Derwent consumes more than two tons of air per minute and that it would exhaust the air from a room 12ft square in one and a half seconds. They go further and state that the tip speed of the im- peller (1,100 m.p.h.) is faster than the speed of a rifle bullet, but here their claim must be disputed ; for about half a century ordinary military rifles have had muzzle velocities much higher than the 1,600ft/.sec which this speed repre- sents, while sporting rifles give anything up to 4,000ft/ sec. To-day, iu fact, a revolver bullet (from the Smith and Wesson Magnum) approaches the speed claimed. An impressive fact is, nevertheless, that the Derwent's 4,200 1b thrust. This is equivalent to making fifteen com-plete record attempts, each of four runs. Moreover, a special Derwent has completed twelve cycles of fiveminutes at its full thrust of 4,200 lb, and after strippin" was found to be in perfect condition. A course somewhere in the Selsey-Brighton area waschosen because of meteorological considerations. Here the High-Speed pilots could expect during August to have abetter chance of obtaining the conditions they required than in any other area. A course wholly over the sea waschosen with a view to avoiding bumps, although at low tide Group Capt. Donaldson and his pilots have been badlybumped above exposed sand and rocks. Indicating the flight path are two hundred markers ofdifferent types. The main markers, at the commence- ment of turns and at each end of the 3 km straight, are32-foot bombing targets; the timed stretch is marked with "camels"—inflatable air bags used for salvaging sunkenaircraft. These obviate the danger of the markers break- ing up in a heavy sea. At each end of the 3 km stretchis a pair of balloons flying at 230ft; these will show the pilots that they are below regulation height of 75 metres. Two timing methods will be used, both photographic.The first makes use of two cine-cameras, one at each end of the course, and the second of modified F.24 aircraftcameras. Accurate timing impulses are transmitted by land line -from the N P.L. at Teddington. In addition to two seaplane tenders the A. /S.R. organisa-tion has supplied a Sea Otter amphibian. Two Mosquitoes of No. 29 Squadron have been fitted with barographs, andwill circle within the outer loops of the course to ensure that the Meteois rln not exceed 400 metres at any point.
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