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Aviation History
1957
1957 - 1872.PDF
Rotodyne Report ... > over the engine nacelle, and a few inches from the trailing edge.This auxiliary delivers compressed air only—it does not pass it through any combustion chambers—via a double volute to a singleexit leading along the front of the wing to the main rotor pylon, and then upwards to the rotor head and out to the Fairey pressure-jet units at the blade tips. In the current prototype each engine feeds two of the four jets, so that in the event of an engine failingonly two of the jets will continue to function; but this is considered sufficient to maintain safety. This arrangement, operating in con-junction with similarly duplicated fuel services, does in fact minimize power loss in the event of one engine failing. Fuel is supplied under pressure to each tip-jet unit, the fuel/airratio being governed by a variable-datum automatic regulator. Ignition of the mixture of fuel and air is by two high-energy igniterplugs in each unit. Each plug is fed from an independent supply as an insurance against electrical failure. The speed of the rotor isquite independent of engine speed and is, therefore, variable over a wide range. This makes for ease of control and is also a valuablecontribution to passenger comfort. The relatively high specific K5O 200 JOO 400 500 STAGE DISTANCE iM.i«' Rotodyne developments: operating economy. fuel consumption of the tip jets is offset to a considerable degreeby the relatively short time during which the rotor head is actually being driven. For most of a typical Rotodyne flight the aircraftwill be moved solely by the tractive power of the Elands' propellers. A rotor-driven accessories gearbox ensures that the essential flyingcontrols are unaffected in the event of both Elands failing when airborne. This gearbox is mounted within the pylon structureand incorporates a hydraulically operated friction rotor brake. Napiers are particularly proud of the hydraulic clutch, whichwas developed from the basic principle of the Sinclair clutch. The requirement was for a clutch with the minimum possible slip andwith great flexibility. Obviously it had to be of the hydraulic and not the friction type; it had to be able to deal with 2,800 shaft h.p.on the early engine (more on those planned for the production Rotodynes) and 12,500 r.p.m.; and, clearly, it would have to becooled. In all, it was a difficult proposition but one with which Napiers, with their long tradition of precision engineering, wereweU able to deal. The vanes of the clutch were designed to be shrouded and cooling oil was passed between the vanes and theshrouds. All this was required within an extremely small diameter to fit in between the jet-pipe bifurcation. In the event the diameterof the clutch was a mere 12in. This hydraulic clutch coupling is supplied with oil from the engine pump. The pressure oil pump,torquemeter pump and scavenge pumps are driven from a shaft at the rear end of the propeller shaft. The oil pressure, torque-meter and main scavenge pumps are of the gear type and the auxiliary scavenge pumps for the bearings are of the vane type. One other modification which had to be made for this Rotodyneengine was in the engine controls. It took the form of an auto- 960 FLIGHT The Fairey spinning rig at the A. and A.B.E., Boxombe Down: the propulsive system is being tested with one Eland and its associated pair of tip-jet rotor blades. matic unit which ensures that in the event of one engine failingpower is increased on the other. Comprising an interconnected propeller control and fuel metering unit, it also, of course, com-pensates for variations in altitude and forward speed. A separate control is provided for the hydraulic clutch. Rotol propellers are fitted to the Rotodyne's Elands, in contrastto the de Havilland products which are used on the Elands flying in the Napier Convair that is now undergoing its C.A.A. accept-ance trials at Santa Monica, California. Originally Rotol were doing all the development work on the Eland propellers. Fewdetails of the reasons for the change-over from one make of pro- peller to another are available, but as Rotol did the original workon the Eland propellers it is possible that they developed extremely fine pitch stops, which would be very necessary in this particularhelicopter application of the Eland. Even today the Eland is still the only turboprop engine available 6O1— 20 100 200 SOO 4OO 5OO 600 r' STAGE DISTANCE M,ir, . • •' " "~~ " Rotodyne developments: passenger-carrying ability. ~ in Britain which is suitable for the Rotodyne. This article has dealtwith the 3,000 e.h.p. NE1.3 unit, but development has been pushed ahead on more powerful versions of the engine, in particular theNE1.6 of 3,500 ch.p., which in its Rotodyne form is known as the NE1.7. This is destined to be fitted to the production Rotodynesand development is going ahead (with official British Government encouragement) following the success of the initial flight tests ofthe Rotodyne—and also as a result of the encouraging reception which Napiers are at the moment receiving from North Americaand other parts of the world now that their Convair is showing its paces. One other version of the Eland, the NE1.4—the "hot" versionof the engine—was at one time considered for the Rotodyne, but lack of Government funds forced Napiers to shelve this design.It is, however, not so much a skeleton in the cupboard as a well- preserved corpse which could be revived by the gentle applicationof Treasury massage. This engine, as is shown in the accompany- ing diagram, would have bestowed considerable additional loadcarrying capabilities on the Rotodyne. The Eland was initially started as a private enterprise byNapiers with, of course, the full backing of their parent firm English Electric. The first standard Eland ran for the first timein September 1952, and began its flight trials in a Varsity test-bed in July 1954. At the end of diat year it successfully completed,at the first attempt, a 150-hour rehearsal type test at the full NE1.1 rating. The first Rotodyne-Eland began running in March1955 and since then many hours have been accumulated on the Napier test-beds at Coronation Road, Acton, and at Hatfield. Napier NEI.3 Data Length (front of propeller shaft to auxiliary compressor inlet flange) 1464m Max. diameter (excluding mounting frame) ... ... ... 36in Net dry weight (including mounting frame but without final jet-pipes) 2,400 Ib (estimated) Engine compressor flow (take-off condition) 31 Ib sec Auxiliary compressor flow at max. cont. rating 18.5 Ib/sec Auxiliary compressor overall pressure ratio at maximum continuous rating 3.9:1 ^ Centre of gravity, distance forward of engine mounting point 58^in (approx.) Engine rotation (viewed from rear) ... ... ... ... Left-hand r Max. engine speed 12,500 r.p.m. Max. take-off power 2,805 s.h.p. plus 500 Ib thrust Max. take-off power (tropical, 45 deg C) 2,185 s.h.p. plus 410 Ib thrust Max. take-off power (Arctic.—26 deg C) 3,000 s.h.p. plus 585 Ib thrust- Max, continuous power ... ... ... ... ... ... 2,180 s.h.p. plus 420 Ib thrust Max. recommended cruising ... 1,710 s.h.p. plus 355 Ib thrust Fuel consumption at max. recommended cruise ... ... 1,300 Ib/hr Specific fuel consumption at max. recommended cruise ... 0.760 Ib/s.h.p./hr Fuel ... ... ... ... ... ... ... ... Wide-cut gasoline, or Avtur
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