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Aviation History
1961
1961 - 0978.PDF
FLIGHT, 20 July 196178 AERO ENGINES 1961 . . . Great Britain ALVIS Alvis Ltd, Coventry. Although the earlier types of Leon- ides nine-cylinder radial piston engine are still in production at ratings of the order of 560 h.p., the most important unit is the Leonides 531. in which the piston stroke is increased to 4.8in. The new marks of Leonides also have longer pistons and are generally strengthened to permit them to operate at their increased level of power (Table 6). Installed in the Twin Pioneer Series 3 these engines confer an increment of additional performance which is especially valuable in operations from hot or high airfields. A considerable number of RAF Twin Pioneers are at present being fitted with the new engines. ARDEM Rollason Aircraft & Engines Ltd, Croydon Airport, Surrey. The Ardem 4C02 flat-four is being produced at Croydon by arrange- ment with M Roger Druine, the designer, and the Popular Flying Association. The basic engine has twin Lucas magnetos and an impulse starter, in place of the original dual magneto of French design. Rollason have also fitted aluminium cylinders of larger bore, raising the output from 30.7 to 40 h.p. and reducing the weight of the engine by 121b. Another modification is the fitting of a Solex side-entry carburettor and a hand-starting device in the cockpit. The company have delivered 26 engines, and the 17 Turbulent aircraft in their own charge have now flown over 2,500hr. BLACKBURN Blackburn Engines Ltd, Brough, Yorkshire. This company was formed in April 1959 to co-ortlinate the aero-engine activities of the Blackburn Group, which in turn merged with Hawker Siddeley last year. By far the most important aircraft-propulsion engine is the Nimbus, but limited service-support and overhaul work is in hand for the Palas 600 turbojet, Palouste 500 compressor and Turmo 603 free-turbine engine in service with the Royal Navy in the Westland P.531 Mk 0 helicopter. In addition, large numbers of Artoustes and Paloustes are employed in non-propulsive applications, particularly for starting aircraft engines and driving airborne auxiliary powerplants. The company's newest engine is the Cumulus, and, although perfor- mance data are given in Table 5, it is not yet a certainty that the com- pany will decide to produce an aircraft-propulsion version. ENGINE DATA ARE TABULATED AT END OF THIS REVIEW Nimbus Originally known by the type-number of A.129, this engine is basically a Turbomeca-derived unit, but with its performance enhanced by the addition of a two-stage transonic axial compressor upstream of the centrifugal stage. The free-turbine output is at the rear, and in the Westland Scout helicopter powers the rotor through primary and secondary reduction gearboxes leading forwards beneath the engine. After early testing as a turbojet in July 1958, the Nimbus ran on the dynamometer in August of that year at 840 s.h.p. Most of the running has been at the level of 968 s.h.p., but Blackburn now speak of the Nimbus as "in the 1,100 h.p. class," and emphasize its robust and economical design. Quantity production is in hand for the Scout, and a slightly different version will be installed in the SRN.2 Hover- craft. BRISTOL SIDDELEY Bristol Siddeley Engines Ltd, Mercury House, Knightsbridge, London SW7. Having demonstrated that two rival companies can effect a true integration—which essentially meant overcoming any feelings of "us" and "them,"" by creating a new cor- porate image able to command the loyalties of all 25,000 employees— Bristol Siddeley have also overcome virtually all the "agonizing re- appraisals" that were needed to put their house in order. Had they not merged, Bristol Aero-Engines and Armstrong Siddeley Motors would undoubtedly today be but shadows of their former selves. As BS, they still have nothing like the aviation business of Rolls-Royce or Pratt & Whitney; but what they have is firm, what they may reason- able expect to win is much greater and they also have the advantage of considerable non-aero business allied to sound management. It was originally dictated that Patchway (Bristol) would be the Aero Division, while Ansty (Coventry) would be the Power Division. In the event, aero engines have by no means disappeared from Coventry, although the main effort of design and development is now at Bristol. Remaining at Ansty and other Coventry establishments are portions of previous ASM programmes, and all work on rocket engines. The latter are not for aircraft, but include such renowned powerplants as Gamma, for Black Knight, and Stentor, for Blue Steel. The Power Division make many other products, in particular the excellent Maybach MD-650 and other high-speed diesel engines for rail traction. BS.53 Pegasus Genesis of this unique powerplant was outlined in Flight for August 12, 1960. After passing through various evolu- tionary stages, it was finally turned into metal in 1959 as the most neat and efficient way of making a relatively conventional gas turbine provide Blackburn Nimbus turboshaft both lift and thrust without itself pivoting bodily. Essentially the Pegasus is a high-by-pass-ratio turbofan with exit nozzles on each side for the fan air and further lateral nozzles for the hot jet at the rear. All four nozzles are provided with efficient cascade vanes, and rotate in unison to turn the whole efflux forwards, downwards or to the rear, to impart braking, lift or thrust to the aircraft. From an early stage the project was in receipt of funding from the Mutual Weapons Development Program, since it promised to meet a common NATO requirement for a V/STOL combat powerplant. The first engine ran on the bench in 1959 as a complete unit with nozzles and air bleeds for aircraft stabilization, and running in this ground rig sorted out most of the major unknowns at an early stage. First applica- tion of the Pegasus is the Hawker P. 1127 tactical strike fighter, which was designed around the engine partly to achieve minimum weight— always a prime requirement in jet-lift aircraft—and partly to minimize undesirable pitch, yaw or roll moments, particularly during nozzle rotation. The aircraft completed hovering trials last year, flew as an aeroplane in March and is now approaching the stage when complete transitions can be effected. It is obvious that the P.I 127 has always been short of all the thrust it would like, and will eventually get; but the experience already gained is unparalleled in any other country. The fundamental drawback to a single lift/thrust engine is that the thrust needed for lift makes the unit too large in other regimes, and the throttling in cruising flight may increase specific consumption. Never- theless, this is a drastic oversimplification, and—in particular for shorter ranges—the Pegasus concept is in many types of application demonstrably superior to all rivals. Development of the engine is being further accelerated by the increased British and MWDP funding an- nounced in April, and appreciably greater thrusts will be forthcoming. Duct-burning of additional fuel in the fan air would at once give a very handsome increment, and the increased s.f.c. in the lift regime would be counteracted by the reduced s.f.c. in the cruise with a bigger aeroplane. Republic/Fokker have announced their interest in Pegasus for a supersonic VTOL fighter for NATO and other constructors have Pegasus-engined projects ranging from supersonic fighters to four- engined transports. BS.75 As yet unnamed, this turbofan is the BS entry in the stakes for the optimum engine in the medium-sized, high-subsonic class. Although it has yet to run it is largely a synthesis of very well proven components, including a fan which owes much to the Olympus, a high- pressure compressor aerodynamically similar to the compressor of the Orpheus, a combustion chamber which likewise betrays traces of Orpheus influence and two-stage compressor and fan turbines which have much in common with those of the Proteus. It should not be inferred from this, however, that the BS.75 is a mere "lash-up" of bits of old engines. Its design has been most carefully considered over a period of years, as was related in our issue of August 12 last year, and while it is logical to draw the maximum possible benefit from the service experience of existing engines, the design of the BS.75 is completely uninhibited. By-pass ratio has been set at a value higher than that for any other British engine, largely owing to the fact that the BS.75 is aimed particu- larly at aircraft with modest cruising speed but likely to operate where noise will be all-important. The specification (Table 2) is challenging, Bristol Siddeley Olympus BOI.7R reheat turbojet on KSt stand
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