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Aviation History
1957
1957 - 0315.PDF
LIGHT, 8 March 1957 317 CIVIL AVIATION INVERSION TO TURBINE POWER SJ last week's issue we briefly summarized the second Henson andtringfellow Memorial Lecture, presented by Mr. H. Sammons, C.B.E., .R.Ae.S., managing director of D. Napier and Son, Ltd. EntitledReplacement of Piston Engines by Gas Turbines in Airliners," it was strong presentation of the Napier view that airlines can increaserofits and give their piston-engined fleets a new and competitive lease f life by conversion to Eland power. We give here a more detailedsynopsis of the paper. BY 1963, the lecturer estimated, there would still be apreponderance of piston-engined aircraft in service. Atthe present time there were 4,300 piston-engined transports nd 170 turbine-powered aircraft in service; by 1960 the rela-ve figures would be 3,900 piston transports and 800 turbine •ansports. By 1963, when all present orders had been fulfilled,;lative figures would be 3,100 piston and 1,500 turbine. "If we ssume that the growth of air traffic will be between 15 and 20er cent per annum, the planned production of aircraft will be ble to meet the demand providing that, substantially, existingircraft will remain in commercial operation." The following factors were of paramount importance in theonsideration of any conversion: (1) cost of conversion; (2) cost f operation; (3) performance of converted aircraft; (4) loss ofevenue during conversion; (5) reliability of the converted air- raft. A more elusive fact which had to be taken into account/as the profit-earning relationship after conversion. Theoretically [ would be possible to have higher direct operating costs andet make a bigger profit owing to increased revenue. However, he lecturer hoped to show that reduced costs were possible. Of all the aeroplanes operating throughout the world thelonvair 340 and 440, the Douglas DC-6B and the Lockheed Constellation 749 were found to be suitable for conversion. Therevere in operation or on order at the present time 285 Convairs, !81 DC-6Bs, and 325 Constellation 749s. This represented aKrtential of 4,730 engines, including spares. If only one-third of he aircraft were converted this was more than sufficient toustify the production of engines and modification kits. light, comparison of the Eland nacelle of the Convair 340 with the •ninimum nacelle shape which could have been achieved by costly changes to the rear nacelle structure and wing. The production Convair 340 converted by Napier to Eland power. The DC-6B and Constellation 749 also lend themselves to conversion. Napier had decided to convert a Convair 340 to Eland power;this aircraft was an example of a new twin-engined airliner of the latest type and therefore suitable for subjecting to a sample con-version. An Elizabethan had also been converted. In considering the conversion of these aircraft it had to bedecided how far to go in the redesign. Both had large-diameter, radial air-cooled piston engines, which meant that, where aturboprop engine of approximately half the diameter was installed, a reduction in nacelle diameter of at least 12in waspossible. This at first seemed to be desirable, but it was decided not to do this "because the modification brought into beingchanges to the wing which were quite prohibitive from the cost point of view." It was decided to retain the original nacelle diameter ofapproximately 66in on the Convair 340 (see diagram). Although PROP4 4 ~»rr F«*AL LAYOUT MINIMUM NACELLE Sefow, performance comparison for (left to right): Convair 340, 0C-6B, Constellation 749. Full lines represent the turboprop versions. S6* 28O ->26O o ul&23O (A o O2OO 18O 340 32O O.3OO E ^a 28Oul ui Q.ft 26O 240 220 200 15 O 2 4 6 a 1O STAGE LENGTH (St milesxiopi t2 i- 2O 15 3 f° * 5 5 IO 15 2O 25 STAGE LENGTH (st miles X IOO) 3O 32O ->3OO Q. O ul Ul 1260 OS24O m 22O 2OO I I '/ / O 5 1O ,15 20 25 30STAGE LENGTH ( St.miles X IOO ) O OS- 15 X X o 1O 3 § 5 k\
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