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Aviation History
1956
1956 - 1561.PDF
FLIGHT, 2 November 1956 719 Helicopter Powerplants... having a rated delivery of 3 lb of air persecond. Although not yet used in heli- copters it is scheduled to power latermodels of Djinn. It was described and illustrated in our issue of May 11 last.Palouste This air-compressing gas tur- bine is now widely used, and is thepowerplant of present Djinn pressure-jet helicopters. The latest version, thePalouste IV, delivers up to 2.4 lb of air per second at 33,000 r.p.m., equal to1,785 cu ft/min of free air or horse-power of 190. An anglicized version is describedand illustrated on an earlier page. U.S.A. AIRCOOLED MOTORS, INC. Syracuse 8, N.Y. (69-2711)Recently this company—makers of "Franklin" engines—claimed that theirneat, air-cooled, flat-six units were fitted to three-quarters of all the helicoptersdelivered from American factories. O-335 Also known as the 6V4, this unithas been built in very large numbers for Hillers and Bells. In both machines theengine is mounted with the crankshaft vertical and is provided with a clutch andcooling fan at the upper (drive) end. The six cylinders each have a bore and strokeof, respectively, 4.5 and 3.5in, resulting in a swept volume of 335 cu in. A typicaldry weight for the 1946-53 engines is 311 lb and the maximum rating 178 h.p.at 3,000 r.p.m. Current production Bells and Hillers have a higher-compression6V4 running on 91-98 octane fuel and rated at 200 h.p. O-425 Of very similar layout to theO-335 (and also designated 6V6) this unit is rather larger, the cylinder size being4.75 by 4.0in. The standard helicopter rating is 245 h.p. A development,designated O-425-2, has a positive-dis- placement supercharger driven from thecrankshaft and can maintain a maximum rating of 300 h.p. up to 8,200ft. It issponsored by the U.S. Navy. A further development, which is at present beingevaluated in a Sikorsky S-52, is the turbo- supercharged O-425-13. The exhaust gasdrives a single-stage turbine which is directly coupled to a shrouded centrifugalblower. ALLISON DIVISION OF GENERAL MOTORS CORPORATION Indianapolis, Ind.(Belmont 1S41) Neither of the units described in next column is in production but they are of unusual technical interest. Turbomeca Artouste III. Single-shatt turboprop. One axial compressor stage followed by a single-sided centrifugal stage, annular combustion chamber and two-stage turbine. Overall height. 221 n; width 17.Bin; length, approximately 68m; dry weight 333 1b; mass flow, about 8.81b sec; pressure ratio 5.1:1; take-off rating, 645 J.h.p. with 6,000 r.p.m output-shaft speed and s.f.c.of 0.73; m.e.t.o.,525 h.p J35 This turbojet was originally ofGeneral Electric design, and started life with the designation TG-180. Two ofthese early units were considerably modi- fied for use as gas producers and wereemployed on the giant tip-drive Hughes XH-17 "flying crane." TS6 A special derivative of this single-shaft turbine has been prepared to suit the large, twin-rotor Vertol (ex-Piasecki)YH-16A Transporter. Originally this was to have had a T38 engine but the morepowerful T56 was actually ready in time for use in the prototype. The U.S.Armed Services designation of the unit was T56-A-5, and the design rating was3,500 sJi.p. BOEING AIRPLANE COMPANY Seattle, Wash. Mohawk 3333) Since the end of World War 2 this largeaircraft firm have been actively develop- ing a range of small gas turbines. Ingeneral, these engines have a single-sided centrifugal compressor and provide shaftpower from a single-stage free turbine. Although their production applicationsare in other fields it is worth noting that experimental Boeing Model 502 unitswere successfully fitted to American heli- copters, the latter being the first gas-tur-bine-powered rotary-wing machines to fly. The first installation was made in aKaman K-225 helicopter, a single 175 h.p. Boeing YT50 being employed. This air-craft flew on turbine power in December 1951. In March 1954 a Kaman HTKhelicopter flew on the power of a pair of Boeing 502-2 units, each rated at 190s.h.p. Both units were arranged to drive through clutches so that either could beshut down for cruising flight. CONTINENTAL AVIATION AND ENGINEERING CORPORATION Detroit, Mich.(Valley 2-1500) Long renowned for their widely usedpiston engines, Continental are now in full production with small gas turbines basedon the Turbomeca designs. Certain of these units, particularly the "Artouste-derivatives," are used in American helicopters. R-97S This well-tried radial engine hasbeen highly developed for rotary-wing applications and is the standard power-plant of most of the Vertol HUP and H-25 tandem-rotor machines. The helicopterR-975 can be mounted at any angle and in the HUP it is installed as a quicklyremovable package complete with lubrica- tion system and cooling fan. EarlierHUPs were fitted with the 525 h.p. R-975-34 but the 550 h.p. -42 is morecommon. A single-speed supercharger and injection-type carburettor are standard. Model 140 Based on the TurbomecaPalouste (q.v.), this air-compressor delivers up to 1,500 cu ft of free air per minute.Although potentially a helicopter engine, its chief production use in the U.S.A. isthe starting of large gas turbines by pneumatic power. Model 210-1 Also known as theT51-T-1, this is a single-shaft turboprop unit with a gas-generator section based onthat of the Turbomeca Arrouste I. Weigh- ing 266 1b complete with 15.2:1 reductiongear, the 210 is rated at 280 s.h.p. at sea level at 35,000 r.p.m. It is installed inthe Bell XH-13F. Model 220-2 Having a gas-generatingsystem like a scaled-up version of that of the 210, the 220 has a mass flow of7 lb/sec, compared with the 4.4 of the smaller unit. As a consequence the shaft-power is raised to a maximum of 425 s.h.p. at 34,800 r.p.m., equivalent to the FrenchArtouste II. The Model 220-2, known by the U.S. Services as the T51-T-3, isinstalled in the Sikorsky XH-39 which recently established world helicopterrecords for altitude and speed. Model 260 With the Service designa-tion T51-T-5, this unit is a free-turbine engine derived from the Model 220 andwith a roughly similar rating of 400 s.h.p. Flight trials with an XT51-T-5 installedin the XH-39 will be used to compare the behaviour of the free-turbine with theless-flexible T51-T-3. GENERAL ELECTRIC CO. Aircraft Gas Turbine Division,Cincinnati IS, Ohio. (Popular 1-4100) Although more than 40,000 turbojets ofG.E. design have now been delivered to the U.S. Air Force and Navy the com-pany's experience of helicopter propulsion is only just beginning. The T58 free-turbine engine is, however, one of the most advanced and attractive shaft-driveunits of its class. T58 As the simplified cut-away draw-ing reveals, this unit has an axial com- Aireoolad-Franklin O-425-13. Helicopter piston engine. Six horizontally-opposed air-cooled cylinders, direct drive with cool- ing fan; exhaust-driven turbo- supercharger (not shown) mount- ed on the airframe. Vertical crankshaft. Width, 34.2in (over valve covers); height, 40in; bore, 4.75in; stroke, 4in; swept volume, 425 cu in; dry weight, 462 1b (including turbo-supercharger): maximum rating, 300h.p. at 3,275 r.p.m. with 4 Ib/sq in boost. Continental R-f75-42 nine- cylinder, air-cooled, poppet-valve radial for helicopters, ungeared but supercharged and with injec- tion-type carburettor (note: the valve-gear push rods lie behind the cylinders). Bore, 5in; stroke, 5.5in; swept volume, 973 cu in (15.9 litres); diameter. 45.5in; length or height (according to installation), 42.4in; dry weight, 730 Ib; maximum power, 550 h.p. at 2,400 r.p.m. at 6.8 Ib boost at sea level.
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