Pratt & Whitney J48

The Pratt & Whitney J48 (company designation JT7 Turbo-Wasp) is a turbojet engine developed by Pratt & Whitney as a license-built version of the Rolls-Royce Tay. The Tay/J48 was an enlarged development of the Rolls-Royce Nene (Pratt & Whitney J42).

J48
A Pratt & Whitney J48
Type	Turbojet
National origin	United Kingdom/United States
Manufacturer	Pratt & Whitney
Major applications	Grumman F9F Panther Grumman F-9 Cougar Lockheed F-94 Starfire
Number built	4,108
Developed from	Rolls-Royce RB.44 Tay

Design and development

In 1947, at the behest of the United States Navy, Pratt & Whitney entered into an agreement to produce the Rolls-Royce Nene centrifugal-flow turbojet engine under license as the J42 (company designation JT6), for use in the Grumman F9F Panther fighter aircraft.^[1] Concerned that the Nene would not have the potential to cope with future weight growth in improved versions of the Panther, Luke Hobbs, vice president of engineering for P&W's parent company, the United Aircraft Corporation, requested that Rolls-Royce design a more powerful engine based on the Nene, which Pratt & Whitney would also produce.

By 1948, Rolls-Royce had designed the Tay turbojet, also a centrifugal-flow design. However, as Rolls-Royce was then developing an improved design with an axial compressor, which would become the Avon, the development and production of the Tay turbojet was left to Pratt & Whitney.^[1][2] However, Rolls-Royce retained the rights to the Tay outside of the United States.

The Tay/J48 was a thirty percent enlargement of the preceding Nene/J42, and was produced both with and without afterburning.^[2]

Operational history

Several aircraft types used the J48 engine during the 1950s, including the Grumman F9F-5 Panther.^[3] and Grumman F9F-6/F9F-8 Cougar,^[4] The U.S. Air Force's Lockheed F-94C Starfire^[5] and North American YF-93 used afterburning versions of the J48 engine.^[6]

Variants

Data from The Engines of Pratt & Whitney: A Technical History.^[7]

J48-P-1

6,000 lbf (27 kN) dry, 8,000 lbf (36 kN) thrust with afterburning

J48-P-2

6,250 lbf (27.8 kN), 7,000 lbf (31 kN) thrust with water injection

J48-P-3

6,000 lbf (27 kN), 8,000 lbf (36 kN) thrust with afterburning

J48-P-5

6,350 lbf (28.2 kN), 8,750 lbf (38.9 kN) thrust with afterburning

J48-P-6

6,250 lbf (27.8 kN), 7,000 lbf (31 kN) thrust with water injection

J48-P-6a

6,250 lbf (27.8 kN), 7,000 lbf (31 kN) thrust with water injection

J48-P-7

6,350 lbf (28.2 kN), 8,750 lbf (38.9 kN) thrust with afterburning

J48-P-8

7,250 lbf (32.2 kN) thrust

J48-P-8A

7,250 lbf (32.2 kN) thrust

Turbo-Wasp JT-7

Commercial engines / company designation

Applications

• Grumman F9F-5 Panther
• Grumman F9F-6/-8 Cougar
• Lockheed F-94C Starfire
• North American YF-93

Specifications (J48-P-8A)

A Pratt & Whitney J48 with afterburner

Data from Aircraft engines of the World 1957^[8]

General characteristics

• Type: turbojet with water injection^[9]
• Length: 109.75 in (2,788 mm) without fixed nozzle
• Diameter: 50.5 in (1,280 mm)
  
• Frontal area: 13.9 sq ft (1.29 m²)
• Dry weight: 2,080 lb (940 kg) dry

Components

• Compressor: single-stage double-sided centrifugal compressor
• Combustors: nine interconnected can combustion chambers
• Turbine: single stage axial
• Fuel type: aviation kerosene / JP-4
• Oil system: pressure spray with scavenge at 40 psi (280 kPa)

Performance

• Maximum thrust: dry 7,250 lbf (32.2 kN) thrust for take-off; wet 8,500 lbf (38 kN)
• Overall pressure ratio: 4.5:1
• Air mass flow: 130 lb/s (59 kg/s) at 11,000 rpm
• Specific fuel consumption: 1.14 lb/(lbf⋅h) (32 g/(kN⋅s))
• Thrust-to-weight ratio: 3.57

See also

Related development

• Rolls-Royce RB.44 Tay
• Rolls-Royce Nene/Pratt & Whitney J42

Related lists

• List of aircraft engines