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Aviation History
1956
1956 - 0597.PDF
11 May 1956 597 V/right Aeronautical: assembly of Turbo-Compounds from automatic conveyer lines. Output is accelerating, against a full order-book. exceptional peak efficiencies. The airscrews are already on test as alsois a new gearbox for the derated unit. The first YT49s, however, have the full rating of about 10,380 e.h.p. Flight development is taking placein a pair of Boeing XB-47Ds in which a YT49 (with a ducted-spinner airscrew) replaces each inner pair of J47 turbojets. The first XB-47Dflew in August 1955 and the second flew in February last. The design figures of the engine (published in our last "Engines" issue of April 9th,1954) still apply. Turbo-Compound. This valuable transport engine has acquired avirtual monopoly among long-range, piston-engined aircraft in America and, in view of the great demand for it, an accelerated productionschedule has been extended until 1958. More than 1,800 are in airline service and approximately the same number are still to be built,excluding military engines. The Turbo-Compound is a refined and expensive engine, usually exceeding £28,500. First commercial services were in August 1953 and the subsequenthistory was not entirely happy. Chronic nozzle-box cracking was experienced; for example T.W.A.'s 19 Super-Gs (Turbo-CompoundDA-3s) are reported to have suffered 226 unscheduled removals of turbines or components in July last year, of which 156 were due tonozzle-box cracking. Introduction of new high-temperature materials is now giving improved behaviour; the longest overhaul time on Turbo-Compounds is 1,400 hr, with Air France. Last summer the new EA series went through qualification tests.First production models are the EA-1 (DC-7C) and EA-2 (L.1649A), the latter having a 0.335 reduction gear for a 16ft, three-blade airscrew.Both are rated at 3,400 h.p. for take-off (dry), a gain of 150 h.p. over the DA series, and the m.e.t.o. low-blower power of 2,800 h.p. is100 h.p. up. Considerable effort is going into improving the low- and high-blower critical cruise altitude by from 2,000 to 5,000ft (to16,600 and 25,600ft), and almost every part of the engine is being intensively developed. During component-testing, dry powers havefrequently exceeded 4,000 h.p. and a commercial rating of this order could be made available if necessary. Some thousands of Turbo-Compounds are in military service.Between 1951 and 1954 a proportion of these engines were made by the Chevrolet Aircraft Engine Division at N. Tonawanda, N.Y. Other Piston Engines. The non-compounded R-3350 Cycloneremains in production, one model—the R-3350-26WB—being needed for Douglas AD-7 production until the end of next year. The ratingis 2,700 h.p. Essentially similar commercial engines (the BD series) have reached a 2,000-hr overhaul life in Constellations. Over 115,000Cyclone 9s have been built, and advanced models of these engines are being made by Lycoming (q.v.) and Canadian Pratt and Whitney (g.v.). Ramjets. Last July the company opened a £2.75m ramjet laboratoryat Wood-Ridge, believed to be the largest privately owned, high-altitude, supersonic facility of its type in the world. Sponsored by the U.S.A.F.,it adjoins the 1949 ramjet laboratory and the 1946 gas-turbine labora- tory. Earlier ramjet testing was limited to units of 50in diameter, buteven larger engines can now be accommodated. The most important production application concerns the NorthAmerican SM-64 Navaho. This missile, with a design range of more than 2,500 miles at Mach 3.5 at over 75,OOOft, is powered by two largeramjets which have been fully developed in test vehicles flying at Mach 3 at up to 90,000ft. The airframe was flown over a year ago onturbojet power, and has now probably flown on the Wright ramjets. Motors are also to be delivered for the Lockheed X-7 missile. Rockets. The accompanying drawing shows the XLR25 liquid-propellant motor which the company have developed for the Bell X-2, Curtiss-Wright Ramjet. This unit was illustrated for the first time two months ago. Clearly designed for a liach number of at least 3 it is believed to^be generally similar to the large powerplants evolved for the cruise propulsion of the SM-MA strategic missile. There is an abrupt change in profile at the end of the ditfuser. Curtiss-Wright LR25-W-1. Throttleable liquid-propellant rocket motor Turbo-pump group driven by self-contained system to feed propellanti to large and small regeneratively-cooled chambers under the control of pilot-actuated electro- hydraulic throttles. Approximate ratings of the two chambers: main, 8,0001b; auxiliary (cruising), 4,000 Ib. Application: Bell X-2 hypersonic research aircraft. an experimental aircraft at present conducting thermal-barrier researchat Edwards A.F.B. A company advertisement states that the X-2 pilot will be "able to throttle the engine up and down . . . and start orstop it ... at will. He will select from a wide range of throttle positions . . . proportioning his fuel and controlling the rocket thrust." U.S.S.R. ALTHOUGH very little detailed information is available, enough isknown of current Russian aircraft-propulsion development to rate it as comparable with progress in the Western nations. The following notesare grouped under broad headings of engine type. Turbojets. Between 1945 and 1948 the basis of Russian work wasa series of German axial engines, which became available at the end of World War 2 (in many cases with a substantial proportion of theirdesign teams). A typical early Russian engine is the RD-10 (reakivnyi dyigatiel 10), based on the Junkers Jumo 004B. Mechanical details werevirtually identical to those of the German engine (eight-stage com- pressor, six flame tubes and single-stage turbine) and the tailpipe-bulletfor varying nozzle area was retained. The standard RD-10 weighs 1,587 lb and has a rating (at 560 m.p.h. at sea level) of 1,887 lb thrustat 8,750 r.p.m. Several thousand were made in Russia before the end of 1947 and were used in the Yak-15 and 17 fighters and trainers. A direct development was a completely Russian engine with an eleven-stage compressor and two-stage turbine. Although the increase in weight was only about 800 1b the later engine was rated at 5,952 Ib thrust at6,000 r.p.m. with an s.f.c. of unity (considerably better than that of the RD-10). It is probably further development of this series which has led to thevery large engine used in the Tu-104 transport and the bomber known to the West as Badger. The consensus of opinion is that this enginehas from nine to eleven stages of compression, an annular combustion chamber and a two-stage turbine. The commercial engine apparently hasa rating of about 14,900 lb dry, but there is evidence to indicate that the bomber can call upon a rating (possibly with water) of at least18,000 Ib from each engine. It is almost certain that four of these units power the large bomber code-named Bison. It is not a by-pass unit,neither is it installed in the centre of a large duct. There is also certain evidence of the existence of an entirely new axialturbojet which is already in large-scale production as the powerplant of the twin-engined all-weather fighter known as Flashlight (and, prob-ably, of the supersonic Farmer). This outstanding unit must be in the class of some Western engines, with a thrust of some 8,000 lb and an im-pressively small diameter—probably not above 33in. In neither of the applications mentioned above is there evidence of afterburning. Shipment of Rolls-Royce Derwents and Nenes in 1947 started a com-pletely separate line of development which Russian and German engineers have exploited to the utmost—more, one might add, than hasthe West. Two eminent Americans recently pronounced the final de- velopments of the RD-45 (Nene derivative) as being in advance of any-thin? done by Rolls-Royce, Pratt and Whitney or Hispano-Suiza. Not only has progressive aerodynamic modification taken this series ofcentrifugal engines into the 120 lb/sec class but—remarkably—^blade alloys have been developed capable of taking temperatures as high asthose in Western engines, although the life is almost certainly shorter. Production of the Nene-derived units probably exceeds 20,000, earlyRD-45s being used in Mig-15s and Il-28s and later examples being fitted to the Mig-17. The final thrust ratings probably exceed 7,000 lb. Turboprops. The outstanding development in this field is a unitdriving contra-rotating airscrews which must have a maximum output of at least 6,500 h.p. (and possibly as much as 7,500 h.p.). It is likelyto be based on early German work. One assumes that it is a single- shaft engine, and it is doubtful if its performance is in any way tobe regarded as spectacular. Piston Engines. Steady development continues upon the followingair-cooled radial engines: M-ll (145 h.p.); ASH-21 (760 h.p.); ASz-21 (540 h.p.) helicopter unit; ASH-82 (around 1,800 h.p.); and ASH-90(2,400 h.p.). Most of these units owe much to Western designs, the last-named being virtually a Chinese-copy of the Wright R-3350. Other Work. It is almost a sine qua non to credit Russia with greatadvances in the fields of rocketry, inter-continental ballistic missiles and even space travel. Little is known beyond the fact that a substantial forceof rocket and missile engineers have been recruited—largely on an ex- German basis—and that they are certainly working hard.
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