Pratt & Whitney JT3D

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JT3D/TF33
First KC-135E with TF33 engines 1982.JPEG
TF33 engines of a KC-135E
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 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[edit]

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. Pratt & Whitney provided a kit whereby JT3C's could be converted to the JT3D standard in an overhaul shop. [1]

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.[2]

JT3Ds from Boeing 707s are used to re-engine USAF KC-135As, 1984.

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; for instance, RAF, French and Saudi E-3s routinely fly higher than NATO/USAF counterparts.

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[edit]

TF33-P-7 engine of a C-141B
JT3D-1 
17,000 lbf (75.62 kN) thrust civil version, (Water injection optional)[3]
JT3D-2 
(TF33-P-3) 17,000 lbf (75.62 kN)[3]
JT3D-3
18,000 lbf (80.07 kN), (Water injection optional)[3]
JT3D-3A
(TF33-P-5) 18,000 lbf (80.07 kN)[3]
JT3D-3B
18,000 lbf (80.07 kN) thrust civil version
JT3D-5A
(TF33-P-7) 18,000 lbf (80.07 kN), (Water injection optional)[3]
JT3D-8A
(TF33-P-7) 18,000 lbf (80.07 kN), (Water injection optional)[3]
JT3D-7
19,000 lbf (84.52 kN) thrust civil version
JT3D-15
22,500 lbf (100.08 kN) thrust civil version for the unbuilt 707-820
TF33-P-3 
17,000 lbf (75.62 kN) thrust for the Boeing B-52H Stratofortress[3]
TF33-P-5 
18,000 lbf (80.07 kN) thrust for the Boeing KC-135 Stratotanker[3]
TF33-P-7 
21,000 lbf (93.41 kN) thrust for the Lockheed C-141 Starlifter[3]
TF33-P-11 
16,000 lbf (71.17 kN) thrust for the Martin B-57 Canberra

Aircraft applications[edit]

JT3D on a Douglas DC-8
Civilian (JT3D)
TF33/JT3D on Boeing VC-137B at Seattle Museum of Flight
Military (TF33)

Specifications (JT3D-1)[edit]

General characteristics

  • Type: Turbofan
  • Length: ~138in (3505mm) flange-to-flange
  • Diameter: ~51.57in (1310mm) fan tip
  • Dry weight: ~4360lb (1978Kg) bare engine

Components

  • 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

Performance

  • 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
  • Air mass flow: 432lb/s (196kg/s)
  • Turbine inlet temperature: ~1150K @Take-off,SLS,ISA
  • Specific fuel consumption: ~0.78 lb/(lbf·h) (22 g/(kN·s)) @ 4000lbf thrust M 0.82,35000ft,ISA
  • Thrust-to-weight ratio: 3.9 bare engine

Specifications (TF33-PW-7)[edit]

General characteristics

  • Type: Turbofan
  • Length: 6200 mm
  • Diameter: 1000 mm
  • Dry weight:

Components

  • Compressor: Axial flow, 7-stage LP

Performance

See also[edit]

Related development
Related lists

References[edit]

  1. ^ based on article in Flight magazine 19 December, 1958
  2. ^ Tony Pither, The Boeing 707 720 and C-135, Air-Britain (Historians), 1998, ISBN 0-85130-236-X
  3. ^ a b c d e f g h i Taylor, John W.R. FRHistS. ARAeS (1962). Jane's All the World's Aircraft 1962-63. London: Sampson, Low, Marston & Co Ltd. 
  • Taylor, John W.R. FRHistS. ARAeS (1962). Jane's All the World's Aircraft 1962-63. London: Sampson, Low, Marston & Co Ltd. 

External links[edit]