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Aviation History
1953
1953 - 0912.PDF
68 FLIGHT THE WEEK AT THE Lutetia.—Little known outside France, this company makes aero engines of the light, air-cooled, two-stroke type. Two-stroke engines suffer from many handicaps, but the Lutetia models aim at getting the best of both worlds by careful design. The mixture is not pre-compressed in the crankcase, but in an eccentric-vane supercharger; with a normal carburettor this gives "excellent atomization and easy starting." Again, no oil is necessary in the fuel, a normal four-stroke-type system being included, with the crankcase acting as tank and cooler. The most-used model is the 4.C.O2, a vee-four with air-cooled cylinder blocks and spark ignition. Giving up to 44 h.p. at 2,800 r.p.m., this engine powers the B6be Jodel, illustrated on page 19 last week. Potez.—Although Henri Potez resumed aircraft manufacture only this year, the firm has turned out air-cooled aero engines for many years. Of the current models, it is noteworthy that, although they are variously fitted with reduction gear, direct fuel-injection, or supercharger, all utilize the same cylinder size, namely 125 by 120 mm. The same sort of standardization applies to many other parts. A number of four, six, and eight cylinder engines were exhibited, and the company certainly appear to be developing classical engines as long as they have a market. Auxiliary motor generator sets were also on view. Rolls-Royce.—A representative RA 7 Avon has now been prepared as a show model, and this was seen to have a large-diameter hot-air anti- icing system installed, as well as a number of other new features. Listed in the French brochure as a military prototype, the engine was actually a production power-plant, and it is believed that it has actually run. Although the Avon is, or is likely to be, licence-produced in Sweden, France, Australia, Belgium and Canada, one cannot say any more about it, nor can Rolls-Royce cut one open for display. Probably complementary to the RA 7 was the Avon afterburner illus trated on page 20 of our last issue. This also was a production job, and showed itself to be a very workmanlike sheet-steel assembly. Bearing in mind the almost frightening airflow, heat dissipation and power output, this afterburner has very modest dimensions. No blanking caps were fitted, but the burners and flame-holders were removed. Left- and right-hand two-position eyelids are fitted, the actuation being effected by four Dunlop electro-hydraulic jacks, the eyelids being mechanically interconnected to prevent deviation of the thrust-line. Although one exhibition Dart was then on show at Zurich, Rolls- Royce produced another superb example which, although not quite representative of the latest Viscount practice, had the fully shrouded turbine blading machined from solid Nimonic blanks. These very neat blades are made by Rolls-Royce, as also are the hollow nozzle guide vanes which are precision-cast by the lost-wax method. A sectioned Derwent was also shown, but held no secrets. Salmson.—The most eye-catching engine here was a genuine Canton- Unn£ of 1916 vintage. Of more immediate interest was a model 9NH helicopter power-plant of the type fitted in the Alouette. This nine- cylinder radial features forced-air cooling and, with a rated power of about 216 h.p., it is remarkable that the equipped weight is under 400 lb. Also shown was an inverted vee-eight of some 255 h.p., of the type used in several trainers. S.F.E.C.M.A.S.—Singularly neat was the S.600 ramjet made of thin steel sheet sprayed with silver paint. At the end of the diffuser section two pipe rings carry four and eight burners respectively, as shown in the photograph on this page. In the centre is an air swirl inducer. From the spray rings an inner steel wall runs back for a distance of about 2ft, separated from the original wall by a £in air cooling space. Photographs showed an S.600 mounted under each outer wing of a Ju88G, and we learnt that the company have applications in various missiles, but have not yet flown the engine as a primary power unit. With a diameter of 60 cm (about 2ft), the weight is 160 lb, and a typical performance is a thrust of 265 lb at 560 m.p.h. at 40,000ft for a fuel consumption of 42 lb/sec. A lively colour film showed the flight of pilotless engine test-beds photographed from an accompanying aircraft. The majority were winged missiles launched, apparently, over North Africa at about 20,000ft. Various types of rocket or ramjet were fitted in the fuselage or wing-tips, some burning brightly and shedding what appeared to be pieces of burn ing solid fuel. One vehicle suddenly blew up with extreme violence— which no doubt explains why that part of the film was sub-titled Lance- ment d'un Engirt Explosif. ••&**:• A L O N (Continued from page 39) S.N.C.A.S.O.—With the marketing licence for the Palas auxiliary turbojet, S.N.C.A.S.O. showed the latest unit on their stand. They have taken the basic Turbomeca engine and worked it into an excellent auxiliary turbojet, the chief function of which is likely to be the boosting of DC-3s to meet the I.C.A.O. engine-out case. The current finely streamlined pod greatly reduces drag, and the flush intake makes it difficult for harmful foreign bodies to enter with the engine air. Also, the total-head intake in flight with fuel off is such that no motoring takes place under ram air. S.N.E.C.M.A.—By far the most important development is the Atar turbojet which originally sprang from B.M.W. designs of the 1940s. S.N.E.C.M.A. have taken the Atar a long way since then, and we know of English engineers best able to judge who have a high regard for this engine. An early Atar 101A was shown fully sectioned, but unfortunately painted in rather a lurid colour scheme. The Atar is very much a utility engine and has a simple axial compressor with seven stages, a sheet-steel annular combustion chamber with 20 burners, huge sheet-steel nozzle guide-vanes, and a single-stage turbine. A variable orifice is fitted, initially of the German needle-valve type, but now employing a pair of eyelids. A really fine exhibit was the 101F, which must be at least 15ft long, including an immense tailpipe and afterburner. A blanking disc was fitted over the outlet, but a prominent flexible fuel-line could be seen running to multiple re-heat burners. This engine has a great virtue from the supersonic point of view, in that the auxiliaries fit snugly around the compressor to retain a small frontal area. The actual diameter is some 39in and total weight 2,560 lb, of which 600 lb is afterburner. Maximum sea-level power is 8,370 lb, falling to 3,790 at 36,000ft at 620 m.p.h. The 101F may power the Mystire 2, Baroudeur and Vautour. Although not shown, photographs were available of the Vulcain, which greatly resembles the Sapphire. It was developed by S.N.E.C.M.A. to give 9,920 lb thrust, and ran for 15 hr at this rating two months ago. Two Vulcains will be flight-tested beneath an Armagnac. At the last Salon the Escopette pulse jet caused a stir, and was found difficult to understand by some. This year's Ecrivisse is guaranteed to baffle all. It is simply a piece of tube bent back along itself, containing a combustion chamber of increased diameter along its mid-portion. There are no moving parts, and the airflow is governed solely by pres sures and profiles. Air is induced through the aft-facing intake on top to form an explosive mixture with any liquid fuel continuously fed to the single burner. At the right strength the mixture explodes, the majority passing out through the lower orifice; the internal depression thus created then draws in a fresh charge. The tube resonates at about 60 cyc/sec, and is started with the aid of an air hose and igniter plug. More compact and powerful than the Escopette, the Ecrivisse weighs 13.2 lb and gives 44 lb thrust for the good specific fuel consumption of 1.35. Shown in photographs was the S.N.E.C.M.A. thrust deviator, which is the first practicable device for turbojets corresponding to the reverse- pitch airscrew. The essentials are a series of channel-section rings mounted in tandem around the jet, and a means for diverging the jet into these rings. The device is being tested in a Vampire—which was demonstrated last weekend—and the jet can be deflected forwards over a proportion of the periphery only, in order to avoid pitching moments or damage to the airframe. One of the early deviators included a series of variable-incidence vanes in the jet-pipe which, by introducing rotation, directed the jet into the deflecting rings by centrifugal force. The pattern demonstrated at Le Bourget—the Vampire is illustrated on page 57—obtains a similar effect by blowing the jet apart with a stream of compressed air from a nozzle at the jet orifice. Normally, the jet passes through the deflecting rings with little loss. Among the piston engines S.N.E.C.M.A. have a useful 14-cylinder helicopter power-plant in the 14XH, which develops up to 900 h.p. With the vertical crankshaft, this engine is highly developed and smooth- running. Not shown were the Hercules 758 (built for the Nord 2501 and shown by S.N.C.A.N.) and the TB-1000 turboprop upon which work appears to have ceased. S.T.A.L.—Although it more than met the specification of the Royal Swedish Air Force, the Dovern axial turbojet has been abandoned in favour of the Avon—which S.T.A.L. are to build in its place. Never theless, an excellent show Dovern II was exhibited, and a fine-looking engine it is. An all-steel, nine-stage compressor is used, the guide vanes of which have reduced incidence at their ends to maintain a relatively thin boundary layer. The pressure ratio is 5.2 : I, and freedom from surge is claimed; four blow-off valves are, in fact, purely to shorten acceleration time. The nine flame-tubes, of Nimonic 75, are giving well over 500 hr life, and a single turbine is fitted and a fixed-area tailpipe. The Dovern IIA incorporates anti-icing, and the IIB a 30 per cent after- The burner assembly of the S.F.E.C.M.A.S. S.600 ramjet. (Be/ow) The Ecrivisse is a resonant pulsejet, with both intake and exhaust facing aft.
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