Engines

JT3D

The Pratt & Whitney JT3D is an early turbofan engine derived from the Pratt & Whitney JT3C turbojet. It was first run in 1958 and was first flown in 1959 under a B-45 Tornado test aircraft. 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.

Design and development
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, 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. 135 KC-135s use the JT3D while 354 are fitted with CFM International CFM56. NATO has a fleet of 17 E-3 Sentry AWACS aircraft with TF33 engines and 3 B707 based TCA aircraft equiped with JT3D-7 engines.
Another well known aircraft which is fitted with the JT3D (in TF33 form) is the Boeing B-52H Stratofortress. The 'H' model of the B-52 was the only production 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 2040.

Variants
- JT3D-3: 18,000 lb (80.1kN) thrust civil version
- JT3D-7: 19,000 lb (84,6 kN) thrust civil version
- TF33-P-3: 17,000 lb (75.6kN) thrust for the B-52H
- TF33-P-5: 18,000 lb (80.1kN) thrust for the KC-135
- TF33-P-7: 21,000 lb (93.4kN) thrust for the C-141
- TF33-P-11: 16,000 lb (71.2kN) thrust for the B-57