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Aviation History
1957
1957 - 1046.PDF
136 FLIGHT Lycoming T53-L-1 (LTC1B-1). Free-turbine engine for helicopters or fixed-wing aircraft (the former version is depicted). Compressor with five axial stages and one centrifugal stage, annular combustion chamber with 12 vaporizing burners, single-stage compressor turbine and single-stage power turbine. Diameter, 23.25in; overall length, 47.8in; dry weight, 460 Ib; mass flow, 10.8 Ib/sec; pressure ratio, 5.7:1; maximum rating, 825 s.h.p. + 102 Ib thrust at 21,500 r.p.m. (6,790 output r.p.m.) with s.f.c. of 0.673 Ib/hr/e.s.h.p. The fixed-wing engine gives 808 s.h.p. AERO ENGINES 1957 . . . 1953. The gas-producing part of the T53 engine went on test inDecember 1954, and at U.S.A.F. request was then up-rated to 720 h.p. Unlike all previous American aero-engines, the T53 is a free-turbineunit, and it is largely this feature which has conferred upon the engine the valuable quality of being able to operate over a wide range ofr.p.m. at constant torque or power, or alternatively to maintain constant r.p.m. over a wide range of power. To the basic gas-generator sectioncan be added gearboxes and other equipment suitable for helicopters or fixed-wing applications. From the annular intake the air is compressed initially in an axialunit comprising five stubby discs with inserted swallow-tail-root blades of 405 stainless steel. From the outset the stators have been manu-factured (at 35c apiece) from twisted sections of rolled aerofoil strip. An axial rotor has now also been run with similarly fabricated bladesfor a period exceeding 300 hr, and it is expected that the price per blade will be reduced by this method from $14.5 to $1.5. Behind theaxial assembly is a single-sided centrifugal impeller fabricated from 422 stainless steel (a titanium impeller is at present under test and thissaves 11J lb in weight and reduces acceleratien time). Final radial compression obviates the need for the tiny and delicateaxial blades which would otherwise be required, and it also throws the air out to a diameter suitable for the combustion section. Thelatter is truly annular and comprises inner and outer liners so arranged that the air first passes just inside the outer casing of the engine tothe rear of the chamber where it is turned through 180 deg and flows forwards through the primary zone. Fuel is injected at the rear of thechamber through twelve "walking stick" vaporizing burners reminiscent of those of Armstrong Siddeley. A proportion of the compressor-delivery air does not enter the chamber at all but is directed around the forward end by peripheral cascades to form a secondary flow ofdilution and film-cooling air. In the space in the centre of the annular chamber are located thecompressor turbine and power turbine, each of which has a single row of cast blades. The design of the chamber is such that temperaturedistribution is very even around the turbine inlet, and the T53 has been run at mean gas temperatures of 1,700 deg F. Moreover thefact that the turbine wheels are surrounded by four layers of steel shielding is considered a valuable safety feature; during the develop-ment of the T55 (q.v.) malfunction of their locking device allowed ten turbine blades to slide out of their fir-tree roots and leave the wheelentirely, but none penetrated to the outside of the engine. The folded configuration of the combustion chamber appreciably reduces the lengthof the engine, a factor which was of assistance in easing the whirling problems of the power-turbine drive shaft. Another advantage of thelayout is that, since the power-turbine is supported within the exhaust diffuser, which is itself part of the combustor, the whole power-turbineand combustion-chamber assembly can be removed as a unit to expose all the hot parts of the engine. This can be done even with the unitinstalled in an airframe. Total bench testing amounted to 2,000 hr late in January and isnow probably double this amount. The 50-hr preliminary flight rating test was passed last August and several YT53 engines have beendelivered. Last September a T53 was run in the HOK-1 test-bed, and after approximately two hours of ground running this helicopterflew on September 27. On October 20, after several hours of ground running, the new Bell XH-40 helicopter was flown for the first time.Both these helicopters have since shown that the flight behaviour of the T53 is exemplary. It is worth noting that at the mock-up reviewof the H-40 the T53 was removed and replaced in fifteen minutes. The engine is also flying in the Vertol 76, in which it drives twolifting /propulsion rotors and two ducted torque-control fans. Future V Lycoming T55-L-1 (LTC4A-1). Free-turbine engine for fixed-wing aircraft or helicopters (the former version is depicted). Configuration similar to that of T53, above. Diameter, 24.25in; overall length, 58.854in; equipped dry weight, 695 Ib; mass flow and pressure ratio, restricted; maximum rating, 1,500 s.h.p.-f-378 Ib 1,451 e.h.p.) at 1,290 output r.p.m. with s.f.c. of 0.657. The helicopter LTC4B-1 gives 1,600 s.h.p. and weighs 600 Ib. applications of the engine include the Grumman high-performanceobservation aircraft (a development contract was placed earlier this month for the fixed-wing T53) and several other machines. T55. Unlike reciprocating engines, gas turbines are amenable tobeing scaled up or down, and when a company has developed a success- ful unit it is logical to produce the same design to a different scale tomeet a wider field of applications. In the T55, Lycoming have pro- duced an engine which, although substantially similar to the T53 inits dimensional envelope and only some 18 per cent heavier, gives double the power with better specific fuel consumption. In basic layout the new T55 is identical to its predecessor, althoughthe design points are slightly more ambitious. The U.S.A.F. requested Lycoming to develop the engine and it is now being funded by theU.S. Army. Like its predecessor it is available in fixed-wing and helicopter versions, and with slight modification can be adapted formarine or industrial use. Prototypes have been subjected to extensive testing and the enginehas a number of civil and military applications. Two recent four- engined aircraft which are being planned around the engine are theFairchild Turboboxcar and the Douglas 1906/1940 series. Piston Engines. Four of the well-established flat-four units manu-factured at Williamsport are the O-235-C1 (108 h.p.), the O-290-D2B (135 h.p.), the O-320 (150 h.p.) and the O-340 (170 h.p.). To thisrange has now been added a new engine with the highest rating of any certificated four-cylinder engine produced in the U.S.A. Desig-nated O-360, the new unit is rated at 180 h.p. at 2,700 r.p.m. and has a very competitive power/weight ratio. The O-360 uses 91/96-octanefuel, and has salt-cooled valves of the rotator type, chrome piston rings and a nitrided crankshaft; an optional item is a constant-speedunit. The engine has powered the prototype Piper Comanche and is the standard powerplant of the Beech Travel-air. Among the flat-six engines are a variety of helicopter units, suchas the VO-435 of 260 h.p. used in late-model Bell helicopters, and the 340 h.p. GSO-480 supercharged and geared engine which powersthe Super Aero Commander. MARQUARDT. Marquardt Aircraft Company, 165 55 SaticoyStreet, Van Nuys, Cal. Founded by Roy E. Marquardt 13 years ago with $1,000 capital, Marquardt Aircraft is now selling at the rate ofmany millions of dollars annually. The vast majority of the company's work lies in the field of supersonic ramjets, but it can now be said thatMarquardt operations encompass every type of advanced air-breathing powerplant—and some engines which are only partially air-breathing. One of the three partners in the OMAR group, the others beingReaction Motors and Olin Mathieson, Marquardt have now taken their first supersonic ramjet families to the production stage and on June 4dedicated an ad hoc production plant at Ogden, Utah. The most im- portant unit in this connection is the RJ43, described below. Subsonic ramjets include a variety used for drone and test-vehiclepropulsion, as well as a range of helicopter tip-drive devices. Among the latter are ramjets of aerofoil section forming extensions to the rotorblades. A great deal of work has been expended in the development of afterburner systems for several turbojets designed by other com-panies, a recent programme in this field concerning the Fairchild J83. Marquardt are named as a prime contractor to the U.S. Air Force inthe Aircraft Nuclear Propulsion Program, and it is unofficially claimed that they are well advanced in the design of a ramjet drawing heatfrom nuclear fuel "although," says the report, "the project was not in the hardware stage last April." Yet another advanced project uponwhich Marquardt are working concerns an air-turbo-rocket, i.e., a turbo- jet in which the compressor is driven by a highly rated turbine fedwith gas from a controlled-combustion solid or liquid charge. Since turbine output is thus made independent of air density much greaterthrust can be obtained at altitude than from a normal turbojet, and, in addition, hydrocarbon fuel can usually be burnt in the rocket exhaustto give augmented thrust. _L Marquardt RJ43-M-1 (MA-20C). Supersonic ramjet. Fixed-geometry supersonic intake, centre body housing fuels system and controls, and convergent/divergent nozzle. Diameter, 28in; length, about 145in; dry weight, 485 Ib; mass flow and pressure ratio, restricted; maximum theoretical thrust at sea level, about 11,500 Ib. RJ43. Depicted in the drawing, this is the largest supersonicramjet yet to have been built in really large numbers. Bearing the company-designation MA-20C it has a diameter of 28in and in its firstgeneration burns conventional kerosine fuel. The double-shock intake is very accurately made and has a fixedgeometry. Most of the fuel system components, including the ram-air- turbine fuel pump and the control system, are assembled and calibratedon the bench in self-contained pre-programmed packages which can be readily installed or replaced in the field. Flame-holding is accom-plished by an efficient mechanical system, although no doubt aero- dynamic means will eventually be incorporated. The combustionchamber is lined with a thick coating of aluminium oxide and the carcase of the engine includes such new alloys as HK31 (Mg-Th-Zr),A-110AT (ti) and 6A1-4V (a self-explanatory heat-treated ti-alloy). For several years the RJ43 has been the powerplant of the IM-99Bomarc twin-engined anti-aircraft missile of the U.S. Air Force. Flight development has been conducted very successfully with the LockheedX-7 test vehicle, which has also been used to develop Marquardt's larger 36in ramjet. Preliminary flight-rating test funds included $5min the spring of 1956; two months ago the Air Materiel Command placed a $ 1.66m contract for RJ43 production testing. ,f
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