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Aviation History
1962
1962 - 0726.PDF
724 FLIGHT International, 10 May 1962 HANOVER ROUND-UP Lt Peracchi of the Italian Air Force in the Fiat G.9IT3 after his brilliant aerobatic display opportunity to convert to turboprop power without the need for restressing airframes or increasing fuel tankage—both serious problems in the conversions made to date. The cherished dream of a single-engined Astazou-powered execu tive aeroplane capable of cruising at over 300 m.p.h. is now being realized by Procaer and Sipa together, in the form of the Antilope, but the problems are considerable. The wing must have relatively high loading and high aspect-ratio to give a reasonable ride at the high cruising speeds, and it must also have sufficient lift to stay within the maximum stalling speed of 64 m.p.h. demanded by airworthiness regulations. The structure is quite a problem, but the feeling seems to be that so long as the money lasts, the Antilope design team can make the grade. Certification for IFR operation is another problem, but some of the Astazous at Hanover had electric intake and propeller de-icing and were covered in this respect. Development of the Astazou into a practicable and available engine has been one of the successes of the past five years. Shorts have been overtaken by it and are now able to count on the engine for all but the first prototype of the Skyvan. Pilatus, nervous at first about the reliability of the remarkable automatic control system, have come to have complete faith in the engine—certainly the Turbo-Porter has been selling reasonably well and performs astonishingly. Turbomeca rightly claim that the automatic control is a safety factor as well as a convenience and that there is nothing difficult about its use. I was fascinated to watch it perform in both the Turbo-Porter and the Potez 840. Nine Turbo-Porters and 27 piston-engined versions have now been sold. A sizeable order for Porters from a West African country is expected shortly. Otherwise, Pilatus are combining with the Swiss Government factory at Emmen and FFA Altenrhein to make the Mirage IIIC under licence. Pilatus will build the fuselage, FFA will make the wing and Emmen will assemble and flight-test. Sulzer Brothers are to make the Atar engine. Some electronics will be made in Switzerland, but the Hughes Taran fire-control will be imported. I talked with Dr Ing B. Eckert, director of Mercedes Benz, about the newly announced PTL 6 turboshaft engine, a hand-made prototype of which was on display. The first of several prototypes ran on the bench at the turn of the years 1958-59 and some 800hr have so far been accumulated. The 50hr pre-flight rating test should be completed during this year and a flight engine is to be installed as a third powerplant in a Noratlas next year. There is no firm production application in view yet, but Mercedes are convinced that there is room for another 1,000 h.p. turboshaft, in helicopters as well as fixed-wing types. Another exhibit on the Mercedes stand was a transonic compressor disc which had run at 85 per cent efficiency at a compression ratio of 1.5:1, an achievement of which the company was proud. The PTL 6, of course, has four axial compressor stages and one centrifugal. The Turbo-Porter I had flown the piston-engined Porter at Hanover two years ago and had been enormously impressed with its handling, and particularly with its pleasantness and capability at the lowest speeds. The Astazou version promised some really interesting results, so this year I jumped at the chance of a flight in it. HB-FAD is, I believe, the first Turbo-Porter and Herr Bohme, the Pilatus test pilot, was frequently flying it with the full load of seven passengers. I sat next to him in front, under that great bubble canopy, with three rows of people two-abreast comfortably ensconced behind me. The Astazou seemed to protrude about eight feet ahead of the wind-screen, but did not unduly interfere with visibility. The engine controls have now been rationalized and simplified. There are a per cent power gauge, a per cent r.p.m. gauge, combined oil temperature and j.p.t. gauge, oil pressure warning light, vernier r.p.m. control, propeller pitch lever (this is the main handling control) and a big red buttoH for automatic full power, with an orange indicator lamp beside it. The engine was started on internal batteries at the push of a button, the r.p.m. vernier being screwed in when j.p.t. showed the fire had lit, until r.p.m. reached 90 per cent, the minimum for taxying. Propeller pitch was still at zero and thrust therefore remained at zero too. The whole procedure took perhaps 20sec and we were ready to roll. Turbine r.p.m. are 43,500, giving a propeller r.p.m. of 2,080, which is pretty noisy on the ground. The 90 per cent allows plenty of power for taxying and considerably reduces noise. When we had taxied out to the end of the western taxiway Bohme screwed the vernier to 100 per cent r.p.m. and pressed the automatic full-power button, whereupon we had full power, with the pitch lever creeping forward of its own accord, in about three seconds. The brakes were released and we lurched forward, to leave the ground at 50 m.p.h. after a run of perhaps 40yd. The fuel tanks were three-quarters full. Under automatic full power the r.p.m. are governed, the pitch constantly adjusted to maintain correct geometric pitch and the fuel input adjusted to maintain maximum j.p.t. The smallest manual displacement of the pitch lever operates a detent which puts the engine back into its cruise regime, where pitch remains unaltered except by lever adjustment, r.p.m. are governed and fuel input is automatically adjusted to maintain r.p.m. The result is that any change in airspeed causes a change in power. After a while we climbed at l,200ft/min at 80 per cent power and 100 m.p.h. Normal climb power is between 80 and 90 per cent and the Turbo Porter can reach 9,800ft in 5min. The Porter air frame is red-lined for cruising at 175 m.p.h. and normal Astazou cruising power will push the aircraft mighty close to that limit; but, as we levelled off from our 80 per cent power climb, the power automatically reduced and there was no danger of exceeding the speed. A slight push forward on the pitch lever was in fact required to build up to a cruising power of 75 per cent, which produced 150 m.p.h. This is fairly close to the red line and one would nor mally have to be careful not to drop the nose and reach it. But with the Astazou, power automatically reduces when the nose is pushed down, so that corner was also removed. In fact, Bohme pushed the nose right down and the torque gauge showed negative thrust. He The Siai Marchetti Riviera prototype arrives in the static park
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