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Aviation History
1960
1960 - 0385.PDF
FLIGHT, 18 March 1960 385 y •v— i $ j a Pratt & Whitney JT4A-3 Commercial turbojet. Eight-stage low-pressure com- pressor, seven-stage high-pressure compressor, combustion chamber with eight flame tubes each having six burners, single-stage high-pressure turbine and two- stage low-pressure turbine. Front-frame diameter, 43in; overall length, 144.1in; dry weight, 5,0201b; max rating, 15,8001b at 8,000 r.p.m. with s.f.c. of 0.78; corre- sponding mass flow and pressure ratio, 300lb/sec and 12:1. JT4A-5 Similar except for weight 4,8151b. JT4A-9 Similar except for weight 5 0501b, and max rating 16,8001b with s.f.c. of 0.81. JT4A-10 Similar to -9 except for weight 4,845lb. JT4A-11: weight, 5,1001b and max rating 17,5001b. JT4A-12: similar to -11 except for weight, 4,8951b. J75-P-2 (JT4A-4) Military engine. Length, 146.4in; weight, 4,960lb; max rating, 15,8O0lb with s.f.c. of 0.77. J75-P-17 (afterburning JT4A-28): length, 237.6in; dry weight, 5,875lbr max rating 24,500lb with s.f.c. of 2.15. J75-P-19W (afterburning and water injection), length, 259.3in; dry weight, 5,960lb; max wet rating, 26,500lb with s.f.c. of 2.2. Pratt & Whitney JT3C-6 Commercial turbojet. Nine-stage low-pressure com- pressor, seven-stage high-pressure compressor, combustion chamber with eight annular flame tubes each having six burners, single-stage high-pressure turbine and two-stage low-pressure turbine. Max diameter of carcase, 38.88in; max height of engine, 49.2in; length as depicted, room temp., 138.64in; dry weight, 4,234lb; max rating, 13,0001b (s.f.c., 0.90) at 8,000 r.p.m. with water, or 11,2001b dry; corresponding mass flow and pressure ratio, 18Olb/sec and 12.5:1; max cruise, M0.85, 4,8S0lb (s.f.c., 0.963) at 20,000ft, 3,220lb (s.f.c., 0.923) at 35,OOOft. JT3C-7 Max diam, 38.8in; max height of engine. 48.9in; length, 136.77in; dry weight, 3,495lb; max rating at sea level, 12,0001b (s.f.c., 0.785) at 8,000 r.p.m.; max cruise, M0.85, 5,3501b (s.f.c., 0.957) at 20,000ft, 3,5501b (s.f.c., 0.909) at 35,OOOft. JT3C-2 (J57-P-43W) Military engine. Max diam, 38.6in; max height of engine, 49in; length with tailcone, room temp., 167.33in; dry weight, 3,840lb; max rating - at sea level, 13,7501b (s.f.c., 0.95) at 8,000 r.p.m. with water. an airflow 150 per cent greater and reduce the mean jet velocity. Design of the fan was facilitated by the company's work on the J91, the huge but defunct turbojet conceived as the engine for the USAF closed-cycle nuclear programme. A two-stage fan was evolved, with blades some 16in long and of narrow chord, supported by a shroud about two-thirds of the radius from the hub to the tip. As a result of its advanced design this fan is relatively light, and, although having but two stages, has replaced the first three stages of the original 1-p. compressor. At the same time, the .1-p. turbine has been modified to provide the neces- sary increase in shaft power by having its second-stage enlarged and a third stage added, making four turbine stages in all. Here again a defunct engine (the T57 turboprop) pro- vided valuable experience on suitable slender blading. Designated JT3D, and sponsored by the Air Force as the TF33, the resulting engine is claimed to retain 90 per cent of the parts of the basic J57, yet gives 52 per cent more take-off thrust with 15 per cent better s.f.c. Extensive tunnel-testing led to an installa- tion in which the fan air—giving about half the total thrust—is discharged on either side by way of a short duct. Pratt & Whitney emphasize the excellence of this duct, from the viewpoints of installed drag and weight. Nevertheless it has penalties, and considerable effort has had to be applied to overcoming the problems of sonic buffeting by the jets on the flanks of the nacelle. Moreover, full thrust reverse has demanded a complex arrange- ment involving multiple jacks and shutters on both the lateral ducts, as well as a reverser for the main hot jet. These devices are absent ' in the much simpler military TF33, and in DC-8s Douglas are going to use a full-length by-pass duct, which will allov full reverse to be accomplished by two shutters. Bench-running in the Wilgoos laboratory began in the autumn of 1958 and four engines had logged almost 300hr by the end of that year. The first prototype JT3D-1 was flight tested last summer, and by January had been evaluated over its full range of power at alti- tudes up to 45,000ft. The commercial JT3D-1 has been bought by five airlines, both for new aircraft and conversions, and costs about $197,000. The Air Force has chosen the TF33-P-1 as the powerplant of the B-52H, and the first engine was recently delivered to Boeing at Wichita. Certification testing is near comple- tion, and commercial deliveries are due to start in July. Succeeding the JT3D-1 is the D-3, with a rating of 18,0001b, and due for delivery in June 1961. JT3D-9 Its "JT3" designation is almost the only point of similarity between this com- pletely new powerplant and its predecessor. Essentially it is a by-pass engine to the Rolls- Royce formula. Although the existing JT3D fan appears to be retained almost unchanged, the low-pressure spool now consists of at least four stages to give a higher fan pressure. The work-split between the spools has been brought more into line with Rolls-Royce prac- tice and a much higher proportion of the total flow passes down the entirely new high- pressure line. By-pass ratio is not more than about 1.1, and the fan air is all ducted aft to a concentric aft nozzle. Design rating is of the order of 21,0001b, and further development is expected to lead to a wet rating of 24,0001b by 1964. The D-9 is at present a paper engine, but Pratt & Whitney are exceedingly anxious to turn it into hardware. JT4/J75 To a time-scale three years later than that of the JT3, Pratt & Whitney evolved the JT4 as a natural outgrowth, to meet the propulsive requirements of the larger first- generation supersonic aircraft of the USAF and Last month Pratt & Whitney Aircraft shipped the first four prototype TF33-P-1 turbofan engines to Boeing's plant at Wichita, Kansas. Commercial JT3D- Is will follow during the summer of this year Navy. In order not to be inferior in specific weight, the JT4 had to surpass its predecessor in many points of design. For example, the first four compressor stages have a lower hub /tip ratio to handle a substantially increased air- flow. Like the JT3D, the longer blades are not much heavier, the stubby fir-tree blades of the JT3 giving way to slender pin-jointed blades of titanium alloy—and one stage was discarded. In retrospect it can be seen that the military J75 was developed just in time to achieve reasonable production, and total deliveries are likely to exceed 1,000. Last year 308 were delivered, almost all of them J75-P-17 and P-19W afterburning models for the Republic F-105 and Convair F-106. About 20 non-afterburning J75-P-2s were delivered for the three Martin P6M-2 Sea Masters. Total flight time is unlikely to exceed 50,000hr on all military engines. Some endurance testing, pos- sibly amounting to l,000hr per powerplant, has been achieved by the USAF with J75s mounted on the outboard pylons of the XB-52. JT4 Commercial Most of the Boeing 707s and Douglas DC-8s so far purchased will be powered by the JT4; in fact, production of this engine is likely to exceed that of the military J75. Although the first airline JT4s are much less powerful than the contemporary Rolls- Royce Conway RCo.12, appreciably heavier and slightly inferior in achieved fuel consump- tion, they have achieved greater commercial success. First version to enter service was the JT4A-3, 323 of which had been delivered by December 31. An engine of this general type was installed in the No. 2 position of the original Boeing 367-80 in December 1957 for basic testing of the complete powerplant of the 707 Intercontinental. In addition, Pratt & Whitney have attempted to make up for lack of military experience by subjecting individual engines to intensive testing, and have built up at least 5,000hr on one powerplant during simulated airline operations on the bench to an overhaul period of l,000hr. From this basic commercial powerplant Pratt & Whitney are evolving a series of air- line engines to three main levels of thrust. Moreover, at each level of thrust there are two series of powerplants, one 2051b lighter as a result of a switch to titanium throughout the 1-p. compressor rotor and for the first three stages on the h-p. spool, at an appreciable penalty in cost. The lightweight version of the A-3 is the A-5, already in production. Later this year deliveries will begin on the A-9, with improved materials in the first two turbine stages in order to run hotter and give 1,0001b more average thrust. The more advanced A-ll/12 series will be rated at 17,5001b aver- age thrust, and are due for delivery some time next year. On January 1 a total of 640 JT4s of all types remained to be delivered, making a total commercial procurement of 862 engines so far. A typical capital cost is $210,000.
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