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Aviation History
1949
1949 - 0525.PDF
MARCH 24TH, 1949 FLIGHT 335 tive of the type in service to-day, and which has enough speed to satisfy the requirements of everyone who is not plagued by the speed bug. (In order not to confuse the issue, the propeller turbine will not be considered.) Concerning the jet aircraft, a figure of 34 for the per- centage structure-weight seems.reasonable, .sinccia wing larger than that of the C-102—whether fitted with efficient flaps or not—would be required in order to give the re- quired minimum flying speed; then, assuming an aircraft of " Ambassadorial "cleanliness, a,.4otal thrust of 14,000 lb is indicated, which will account for a weight of some 7,700 1b or 14 per ceni/ of the gross weight. S For the weight of crew, equipment, stores, and so on, a figure of 6,000 lb seems fair enough; but, un- like Sir Frank Whittle, the writer does not believe that any percepSifcae weight- saving in this connection could be achieved as a re- sult of the jet machine re- ducing the time between the airport terminals by 10 to 15 minutes. These opinions take for granted a service run on commonsense and not luxurious lines. From the above figures, we find that the piston-en- gined aircraft has a dispos- able load of 24,250 lb and the jet-engined machine a dis- posable load of 22,600 1b. Using Sir Frank's method, we find that the required fuel loads are 390 gall (say, 2,850 lb) and 1,122 gall (9,100 1b), so that the piston-engined machine has a theoretical payload of 21,400 lb and the jet type a payload of 13,500 lb. The term "theoretical payload" has been used, since, in order to limit the number of different types required by an airline and provide a reasonably flexible machine, an effective range considerably greater than 200 miles, and a correspondingly smaller payload, would "be primarily considered. However, if due consideration" were given in the initial design, there is no reason why the slower machine should not carry a payload approaching the theoretical figure, made up of passengers, mail and freight; in any case, it is clear that it will enjoy a considerable advantage over the 400 m.p.h. machine in this respect. Turning to the question of fuel, A. Cdre. Whittle's figure of is 2d per gallon for the cost of kerosene probably favours the jet unduly, since a large demand for kerosene would probably have the effect of raising its price, as the coats of the various fuels depend on the relative amounts in demand. In any case, the far larger amount of fuel re- quired by the faster machine outweighs any saving in the cost of turbine fuel. Although it is very common nowadays to hear kerosene acclaimed as much safer than petroleum, it mast foe aekaow- The Rolls-Royce-Derwent-engined C-IQ2, (Canada) Ltd. ledged, in fairness to the piston engine, that this has yet to be proved in service. It should not be forgotten that the jet engine relies on the use of very high temperatures (600 deg to 850 deg C), figures which are tikety to be in- creased with the development of higher-grade steels, and that the amount of fuel involved is very much greater. Regarding the question of utilization, it is probably not generally realized that the figure for B.O.A.C.'s Constel- lations and T.C.A.'s D.C.-4MS on the Atlantic route is from 2,500-3,000 hours per annum, so that Sir Frank's figure of 2,000 hours for the piston - engined aircraft could be suitably increased. It is, of course, quite pos- sible that jet aircraft could improve on these figures, but it should be borne in mind that much heavier utilization would mean that services would necessarily be operated during the hours of darkness, which would probably be unpopular with passengers, .an'! conse- quently give poor load fac- tors. Moreover, mainten- ance would need to be car- ried out on a shift basis, which would be more ex- pensive than normal work- ing, and coats due to light- ing and heating would be • ' considerably increased. A. Cdre. Whittle chooses the London-Paris route for con- sideration because, he says, "it is one on which it is par- ticularly difficult to make a profit''; but he does not qualify the statement. There is, in the writer's opinion, no reason why the case should be as he claims it to be: there is always a heavy potential traffic offering, the distance involved does not entail the carriage of fuel at the expense of payload, and the weather likely to be ex- pected can be fairly reliably forecast. In actual fact, Im- perial Airways had reached the stage in 1939 when they could have operated the service without subsidy. The foregoing notes should serve to show that the saving of a few minutes on a door-to-door journey lasting three hours or so has to be very dearly bought, no matter what present-day means of propulsion is employed. It is well known that very high speed is uneconomical for commercial aircraft when the piston engine is employed, and even Sir Frank's figures show that it is cheaper to fly at 300 m.p.h. than at 400 m.p.h. with a jet. Since the jet engine is acknowledged to be uneconomic for relatively low-speed propulsion, it is only reasonable to expect that any large increase over speeds in vogue to-day would be paid for by increased operating costs. Wsbea It is recalled that, at present, only a iew of the 'worlds airlines can show a profit, even when inordinate mail payments arc made to them, any such incr-ease can- not be jiistifieiL built by A. V. Roe LONDON AIRPORT FILM A TEN-MINUTE documentary film about London Airport,made by the Crown Film Unit, is to "be distributed to some 3,500 cinemas. It will also be shown by Government mobile projection units, a,nd from May 1st it will be available on free loan from the Central Film Library, London. The film was produced for the public, and an absence of technicalities is therefore understandable. Its opening scenes are particularly well-chosen; the airport is shown from an approaching aircraft, and R/T exchanges between the tower and a Trans-Canada captain complete the impression of arrival. One feels, however, that in the short time available some of the scenes of airfield construction might have been cut in order to show the airliners rather more intimately; and exclusion from the commentary of the names of even the most frequently used types suggests under-estimation of the public's interest in such matters. / INDTJS*miAL AIRFIELD TTKHTIL 1-946-the Dav*.d Broun group of engineering com- V* pastes osed to charter aircraft for business flights; toast ih.ev found, the method inconvenient, and in October of that year acquired aircraft oi their own. Since then no fewer than 1,500 passengers from the managing director to maintenance engineers, have been carried on business fights not only in the British Isles but over most of Europe. The aircraft were based at Sherburn-in-Elmet until, in 1947, the firm converted a stretch of moorland at Crosland Heath, only a mile from the Haddersfield headquarters, into a private airfield. A photograph of the fleet appears on p. 336. The airfield—which, at 850ft above sea level, is the highest in England—now has emergency night-landing facilities. It has been placed at the service of other users, without landing- fee, and it is probable that a BeTfast-Huddersfield "textiles charter" service will make frequent use of it. »•• 5
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