Pratt & Whitney JT3D
| JT3D/TF33 | |
|---|---|
 |
|
| JT3D-3B on a Royal Australian Air Force Boeing 707 | |
| Type | Turbofan |
| Manufacturer | Pratt & Whitney |
| First run | 1958 |
| Major applications |
B-52H Stratofortress Boeing 707 C-141 Starlifter Douglas DC-8 |
| Number built | ca. 8,600 |
| Developed from | Pratt & Whitney J57/JT3C |
The Pratt & Whitney JT3D is an early turbofan aircraft 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.
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 replaced the first 3 stages of the 9-stage JT3C LP compressor. On the LP turbine, the second stage was enlarged and a third stage added.
Unlike GE with the CJ805-23, Pratt & Whitney had not undertaken any transonic fan research prior to designing the JT3D, so they were unable to incorporate a single stage unit into the specification. Instead P&W designed a 2-stage unit based on some research they had done to support the J91 nuclear turbojet.
Nevertheless, the overall P&W engine design was quite an elegant solution to produce a turbofan to compete with the Rolls-Royce Conway in a very short timescale. Indeed, 55 years later, the basic architecture of the JT3D can still be seen in modern large American civil turbofans, such as the GE90, PW4000, etc..
On the Boeing 707 the JT3D fan nacelle was relatively short, whereas the Douglas DC-8 installation had a full length fan cowl. 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.
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