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Aviation History
1960
1960 - 0082.PDF
82 FLIGHT, 15 January 1960 CONWAY . . . withstand exceedingly high and varying internal pressure loads atrelatively high ambient temperatures; moreover, the duct has to withstand 150 per cent of the maximum thrust of the engine asan axial load when the reverser is in operation. Rolls-Royce designs of thrust reverser and noise-suppressingnozzle have already been described (Flight, September 19, 1958 and February 6, 1959) and are illustrated on pp. 78-79. JosephLucas (G.T.E.) Ltd designed the fuel system, which is generally conventional. Most standard turbine fuels can be accepted andthe system is entirely automatic in operation. Unlike correspond- ing American engines the pilot does not have to set up the engineaccording to airfield, altitude and temperature in order to produce the required thrust, but merely pushes the power levers as farforward as they will go in the knowledge that the maximum possible thrust will thereby be obtained (up to the cold-weatherlimit of 19,0001b). The oil system is self-contained and includes a fuel oil heat exchanger. Air sealing and cooling is conventional,although it is worth noting that, in order to provide air at the required pressure, the cooling flow for the turbine discs is tappedoff at about 400 °C from the inner combustion casing. For the Boeing 707-436 (BOAC) and its sister-ships in otherairlines, accessories are disposed as shown in the main drawings on the centre pages of this issue. The Sundstrand drive incorporatesits own oil system and cooler, and an auto-tensioned cable/pulley system is used to control engine power. Aircraft pressurization ishandled by an AiResearch turbo-compressor driven by bleed air. As an alternatiye, a bleed from the outside of the low-pressurecompressor casing could be employed during the cruise (the Caravelle is at present pressurized by air bled from the inside ofthe Avon compressor). The DC-8 engine is generally similar, except that the turbo-compressor units are relocated in the noseof the aircraft and that the low-pressure fuel system includes a flowmeter. For the 707, Rolls-Royce deliver the complete powerplant,including cowling, reverser and suppressor. For DC-8s bare engines are delivered. The Boeing nacelle comprises a nose cowl andenormous side doors, which can be opened for major servicing but incorporate small apertures for such tasks as filling the oil sump.These doors are hinged to the upper "mid fairing" which, although made by Rolls-Royce, bolts permanently to the bottom of theBoeing pylon and marks the joint between powerplant and air- frame. The engine is suspended by a pair of spigots above theintermediate casing, one of which takes thrust and the other (being spherically mounted) takes weight only. The resultant yawingload, and a proportion of the weight, is borne by the rear suspen- sion above the nozzle box. The majority of connecting servicesare grouped at a disconnect platform on the starboard side of the compressor casing. In most installations a low-pressure air orcombustion starter is used. The next stage in development is the RCo.15, which canreadily be converted from RCo.12 standard at an overhaul. As well as incorporating a large number of minor ckaning-up modifi-cations to improve the specific consumption, the RCo.15 has a new front end, fabricated entirely in steel and with a slightlyincreased diameter. The zero stage has increased capacity to handle the mass flow of 2951b/sec, the inlet guide vanes and zero- This detail sketch of the forward end of a combustion chamber clarifies the mechanical and aero- dynamic design. Typifying modern Rolls-Royce/Lucas practice, each of the ten cans is fabricated from nimonic sheet HIGH PRESSURE COMPRESSOR OUTLET CASING stage rotor blades arelengthened and the first- stage rotor blades have aslightly changed angular setting. Ultimate developmentof the Conway is aimed at raising the by-pass ratioto a level giving optimum specific consumption inhigh-subsonic cruise con- ditions. Engine diameterhas grown to some 45in.— which can readily beaccepted in a nacelle-type installation, and is in any case 9in less than that of the Pratt &Whitney JT3D—and the by-pass ratio has been raised from 0.3 to 0.6. The greatly increased mass flow of 3631b/sec and otherchanges have resulted in a considerable increase in thrust, match- ing the engine to the Vickers-Armstrongs VC10, as the Conway540, and allowing Boeing to offer an even larger 707. It is worth noting that the complete high-pressure rotating assembly is exactlythe same as that in the present engine, and it is expected that this critical unit will have logged nearly 2,000,000hr in airline service,as well as additional time with Bomber Command, by the time the RCo.42 enters service. In many respects the RCo.42 has developed in parallel withthe RB.141 and 163, this being particularly the case in the careful matching of hot and cold flow-velocities and the mixing ofthese streams in the final nozzle to obtain the last iota of installed efficiency. Rolls-Royce are confident that the RCo.42 cannot bebeaten within the time-scale of its development, and even more advanced Conways are planned to succeed it. THE ORDER BOOK Military: The RCo.11 is currently in production for the Handley Page Victor B.2 bomber for the RAF. No indication of the number of aircraft may be divulged. Civil: The RCo.12 (Mk 508) is being delivered for installation in Boeing 707s of BOAC (15 707-436), Air India (3 or 4 707-437), Lufthansa (4 707-430) and Varig (2 707-441); the RCo.12 (Mk 509) is being delivered for installation in DC-8s of TCA (6) and Alitalia (4); the RCo.15 has been ordered for installation in the DC-8s of CPAL (4); and the RCo.42 (Mk 540) is being developed to power the VC10 aircraft of BOAC (35). RCo.12 BASIC DATA Dimensions: Maximum carcase diameter 42.2in; length of bare engine 135.9in; internal diameter at intake 37.6in. Performance (ISA standard day): Guaranteed minimum rating 17,5001b. average fleet rating 18.0001b at 9,980 r.p.m., with mass flow of 282lb/sec; corre- sponding specific consumption 0.725; typical cruising thrust at tropopause at47Skt, 4,6251b; corresponding specific consumption 0.874. HEAT SHIELD Although precise evaluation under altitude conditions is being conducted in the company's high-altitude test plant ("Flight," October 3, 1958) intensive flying is being conducted with an Ashton and with the Vulcan shown here. The Vulcan has frequently flown 18hr daily
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