Pratt & Whitney JT3D

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The Pratt & Whitney JT3D is an early turbofan engine derived from the Pratt & Whitney JT3C turbojet and was first flown in 1958. Over 8,000 JT3Ds were produced between 1959 and 1985. Most JT3D engines still in service today are used on military aircraft, where the engine is referred to by its USAF designation of TF33.

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 next development of the 707 (the -300 series) were only offered with JT3D turbofans.[1]

The Boeing KC-135 Stratotankers were all originally powered by turbojet engines, although some of the more specialized variants were fitted with TF33s. 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.[1]

After long service for both airlines and air forces the number of JT3D powered aircraft is steadily decreasing. 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, e.g RAF, French and Saudi E-3s routinely fly higher than NATO/USAF counterparts. However the main funding for such a program would come from the United States who most likely wish to upgrade their own fleet first.[who?]

Another well known aircraft which was fitted with the JT3D (in TF33 form) was the Boeing B-52H Stratofortress. The 'H' model of the B-52 was the only variant of the famous bomber to be fitted with turbofan engines, and the only model remaining in US Air Force service. It is expected to remain as a mainstay of the USAF heavy bomber fleet until at least 2030.

[edit] Variants

JT3D-3 
18,000lb (80.1 kN) thrust civil version
TF33-P-3
17,000lb (75.6 kN) thrust for the B-52H
TF33-P-5
18,000lb (80.1 kN thrust for the KC-135
TF33-P-7
21,000lb (93.4 kN) thrust for the C-141
TF33-P-11
16,000lb (71.2 kN) thrust for the B-57

[edit] Aircraft applications


[edit] References

  1. ^ a b Tony Pither, The Boeing 707 720 and C-135, Air-Britain (Historians), 1998, ISBN 0 85130 236 X
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