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Pratt & Whitney JT3D / TF33

KC-135E with TF33 engines


Aware of the competition from the Rolls-Royce Conway turbofan, Pratt&Whitney decided to develop the JT3D turbofan from the JT3C turbojet for later deliveries of the Boeing 707 and the Douglas DC-8, then nearing entry into service. A 2-stage fan, based on work done on the J91 nuclear turbojet, replaced the first 3 stages of the 8-stage JT3C LP compressor. On the LP turbine, the second stage was enlarged and a third stage added. On the Boeing 707 the fan nacelle was relatively short, whereas the Douglas DC-8 installation had a full length fan cowl. First run in 1958 and flown in 1959 (under a B-45 Tornado test aircraft), Pratt & Whitney provided a kit whereby JT3C's could be converted to the JT3D standard in an overhaul shop.

In 1959, important orders for the engine were the Boeing 707-120B and Boeing 720B when American Airlines ordered one 707 powered by JT3D turbofans and KLM ordered a JT3D powered Douglas DC-8. The earlier 707s had been powered by the turbojet JT3C and the improved efficiency of the turbofan soon attracted the airlines. A JT3D powered 707-123B and 720-023B (the suffix B was to indicate a turbofan powered aircraft) entered service with American Airlines on the same day, March 12, 1961.

The Boeing KC-135 Stratotankers were all originally powered by turbojet engines. With the demise of many airline 707s the United States Air Force took the opportunity to buy the surplus airframes and use the engines to re-engine the KC-135As used by the Air National Guard and reserve squadrons with the civilian JT3D (designated TF33-PW-102). Over 150 aircraft were modified and the former KC-135A were re-designated the KC-135E.

135 KC-135s use the JT3D while 354 were fitted with CFM International CFM56 engines which provide greater thrust and increased operational flexibility due to their lower noise footprint. The noise of the JT3D is one of the reasons NATO has debated re-engining their E-3 Sentry AWACS fleet, with the aircraft subject to restrictions that modern-engined aircraft are not. Operational flexibility would be further increased due to the ability of higher power engines to increase the ceiling of the aircraft, extending the horizon for radar surveillance; for instance, RAF, French and Saudi E-3s routinely fly higher than NATO/USAF counterparts.

the Boeing B-52H Stratofortress is fitted with the JT3D (in TF33 form). The 'H' model of the B-52 was the only production variant of the bomber to be fitted with turbofan engines.

About 8,600 JT3Ds were produced between 1959 and 1985.



17,000 lbf (75.62 kN) thrust civil version, (Water injection optional)
(TF33-P-3) 17,000 lbf (75.62 kN)
18,000 lbf (80.07 kN), (Water injection optional)


(TF33-P-5) 18,000 lbf (80.07 kN)


18,000 lbf (80.07 kN) thrust civil version


(TF33-P-7) 18,000 lbf (80.07 kN), (Water injection optional)


(TF33-P-7) 18,000 lbf (80.07 kN), (Water injection optional)


19,000 lbf (84.52 kN) thrust civil version


22,500 lbf (100.08 kN) thrust civil version for the unbuilt 707-820


17,000 lbf (75.62 kN) thrust for the Boeing B-52H Stratofortress


18,000 lbf (80.07 kN) thrust for the Boeing KC-135 Stratotanker


21,000 lbf (93.41 kN) thrust for the Lockheed C-141 Starlifter


16,000 lbf (71.17 kN) thrust for the Martin B-57 Canberra


Aircraft applications:

Civilian (JT3D)
Boeing 707
Douglas DC-8
Shanghai Y-10

Military (TF33)
B-52 Stratofortress
Boeing C-18
C-135B Stratolifter
E-3 Sentry
E-8 Joint STARS
KC-135E Stratotanker (JT3Ds from surplus civil 707 airliners)
VC-137B/C Stratoliner
C-141 Starlifter
Martin RB-57F


Type: Turbofan
Length: ~138in (3505mm) flange-to-flange
Diameter: ~51.57in (1310mm) fan tip
Dry weight: ~4360lb (1978Kg) bare engine
Compressor: Axial flow, 2-stage fan, 6-stage IP compressor and 7-stage HP compressor
Combustors: cannular, 8 flame tubes
Turbine: Axial flow,single stage HP turbine and 3-stage LP turbine
Maximum thrust: 17,000 lbf (75.6 KN)Take-off (flat-rated to ISA); partial thrust restoration with water injection
Overall pressure ratio: ~12.5:1; bypass ratio 1.42:1
Turbine inlet temperature: ~1150K @Take-off,SLS,ISA
Specific fuel consumption: ~0.78lb/hr/lbf (22.09g/s/KN) @ 4000lbf thrust M 0.82,35000ft,ISA
Thrust-to-weight ratio: 3.9 bare engine


Type: Turbofan
Length: 6200 mm
Diameter: 1000 mm
Compressor: Axial flow, 7-stage LP
Maximum thrust: 21,000 lbf







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