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Aviation History
1959
1959 - 2376.PDF
18 September 1959 263 An eighth-scale model of the latest addition to the family ofjet engine test stands manufactured by John Curran was displayed for the first time; designated Mk 1C, this has a capacity for enginesof up to 30,000 1b thrust and it was specially designed for checking Rolls-Royce Conways and Pratt and Whitney JT3 and JT4 turbo-jets. The first example will be supplied to Rolls-Royce's new overhaul factory in Brazil, and two other units are in productionfor the Indian Air Force and South African Airways. An example of a new range of inexpensive classroom training aids for airlines,by Air Trainers Link, was new to the display. Developed in co-operation with B.O.A.C, the example shown was concernedwith the Bendix Flight System of the 707. Royston Instruments showed a new kind of fault-finding equip-ment for airline maintenance departments, used in conjunction with the company's Midas flight and crash recorder (also dis-played). It is claimed to be simpler and cheaper than other larger play-back equipment. Its purpose is to permit maintenance staffquickly to detect and deal with faults which have developed in flight. A cassette from the flight recorder is taken out of the air-craft, the tape is rewound to a point in time (G.M.T.) where the pilot has reported the trouble, and the recorder is then re-played.Simulated readings of the instrument are reproduced and a ground engineer thus has a complete picture upon which to basehis diagnosis. Temple wood Hawksley, a member of the Hawker SiddeleyGroup, and who have taken over the design, development and manufacture of airline servicing units formerly dealt with byAir Service Training, have supplemented the existing range of A.S.T. equipment. New products include an improved version ofthe Mk 4 servicing trolley with a higher capacity for the big jets. New heavy-duty servicing units and water carriers are alsoto be put into production as self-propelled units. POWERPLANTS PROBABLY the most significant development in aircraft pro-pulsion in recent years is the evolution of the double-flow turbojet as an intermediary bridging the gap between the turboprop andthe turbojet. The manner in which this has come about is well known: after initial exploration by such companies as Turbomecaand Metrovick, Rolls-Royce established the first standard with the Conway (which they have always described as a by-passturbojet), the thrust of which has risen from 9,250 1b to 18,500 lb since 1953. Commercial sales won by these engines in 1956spurred the two largest American companies to produce "fan" derivatives of existing straight turbojets. Today, the position is clarified. While the first-generationAmerican fans come near to entering service both Rolls-Royce and Bristol Siddeley are actively developing families of entirelynew powerplants utilizing the double-flow principle. Both firms are at pains to point out that their new engines are based uponclean sheets of paper and are in no way compromised by having to incorporate pans of earlier engines; yet at the same timeBristol Siddeley at least stress that many of the most critical items in their new fan engines are "identical or similar to those used inearlier designs which have completed many thousands of hours in service."First details of the Bristol Siddeley BE.S8 were given in our two previous issues. These figures may now be expanded to thefollowing: sea-level thrust, 14,500 1b with s.f.c. of 0.572; s.f.c. under cruising conditions at 36,000ft, 0.8 ("at least 10 per centlower than that of the most efficient current turbojet"). Dry weight is 2,600 lb. It remains to be seen what mechanical con-figuration has been adopted. The alternatives are: single shaft; twin shaft (which may be regarded as a straight jet with amechanically independent low-pressure assembly comprising a turbine driving a two-stage fan), and split compression, in whichthe fan is formed by the first two stages of the low-pressure compressor having extended blading. Bearing in mind the likeli-hood that major portions of the rotating assembly are derived from the Orpheus and Olympus, the third alternative seems themost likely. The cold-flow ratio is known to lie between 1.5 and 2, suggesting that the engine is matched to propulsion of transportaircraft at Mach numbers of not greater than 0.9. Compared with the Bristol Siddeley fans, the Rolls-RoyceRB.141, progenitor of a complete family, has a lower cold-flow ratio, resulting in an engine of higher fineness ratio. Rolls-Roycehave stated that they are aiming particularly at thrusts between 10,000 and 17,500 lb as being most suitable for the propulsion ofthe next generation of airliners. So far, financing of the family appears to be entirely by the company. The two engines mostlikely to reach a state of early commercial availability are a 14,300 lb thrust RB.141 and a 10,100 lb thrust RB.163, respec-tively for the advanced Caravelle and the Airco D.H.121. The slimness of the RB.141 (displayed at Farnborough as anengineering mock-up) should significantly reduce the momentum drag and increase the net effective thrust imparted to the air-frame, especially at take-off, in comparison with a fat fan engine. The four lift-engines of the SC.l are Rolls-Royce RB.108s arranged in twin packages which tilt 30 deg fore and aft In the RB.141 engineering mock-up (presumably for Sud Avia-tion) the accessory package was mounted on the underside, seemingly more logical than the dorsal mounting on the BE.58.Compared with the new family of "optimum" commercial engines the existing Conway family have a rather lower cold-flowratio; although their economy is nevertheless appreciably better than that of the straight turbojets with which they have competedfor business (as the measured performance figures for the Boeing 707-436 substantiate). It is an index of the quality of Rolls-Royceengineering that, although until recently Conway flight-time was severely limited, development has surpassed all expectations. Clearance of the commercial units at 17,500 lb has beenachieved horn 12 to 18 months ahead of schedule; Mks 505 and 507 (Boeing and Douglas respectively) are being delivered inquantity at 16,500 lb guaranteed minimum dry, with approval at 17,000 lb; Mks 508 and 509 (Boeing and Douglas) are virtuallyidentical at 17,500/18,000 lb; net dry weight is averaging some 140 1b below the guaranteed figure; engines have already beenrun ar over 19,000 lb dry and appreciably higher ratings are planned. For commercial operations, increased power will confermuch-needed improvement in field performance, and in any case it is likely that the Vickers VC.10 is being planned around aConway more powerful than those currently being delivered. For military applications the RCo.ll (17,250 lb dry) is being deliveredin quantity for the Victor B.2, and Rolls-Royce have now made reference to the possibility of producing a fighter Conway witha thrust of 30,000 lb burning additional fuel in the by-pass air. Permission has been granted for publication of the configurationof the main rotating assemblies of the current Conway. The RCo.10 and 12 (Mks 505-509) utilize a seven-stage low-pressurecompressor, a nine-stage high-pressure compressor, a single-stage high-pressure turbine and a two-stage low-pressure turbine. Thepressure ratio may not be quoted, but it may be recalled that the Tyne, the pressure-ratio of which is 13 : 1, has a six-stage 1-p.compressor and a nine-stage h-p. compressor; and it has been suggested that the h-p. spool of the Tyne is scaled from that ofthe Conway. It must be recorded that certain markets for the Napier Elandhave failed to materialize in the manner hoped. Nevertheless, as a straightforward engineering product the engine has progressedexcellently; it is insufficiently appreciated that it has been fully certificated to the new ARB/CAA schedule (and was actually thefirst turboprop in the world to achieve this distinction), and has for some time been carrying fare-paying passengers. The operatorinvolved is Allegheny Airlines, using a CV-540. During the summer some unfortunate service delays were caused by bearingfailures, and Allegheny were forced to use other equipment while the problem was investigated. It was traced to brinelling of theraces during air/road shipment of the powerplants from the United Kingdom, and the new transport stand—displayed atFarnborough—incorporates rubber-in-compression shockproof mountings which seem to have made brinelling a thing of the past. Although it has yet to fly, the de Havilland Gyron JuniorDGJ.10R (10,000 lb dry, 14,000 1b with afterburner) may be regarded as already in a very advanced state of development owing
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