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J85
A General Electric J85-5
Type	Turbojet
National origin	United States
Manufacturer	General Electric
First run	1950s
Major applications	A-37 Dragonfly Canadair CL-41 Tutor Northrop F-5 T-38 Talon
Variants	General Electric CJ610, General Electric CF700
Developed into	General Electric CF700

The General Electric J85 is a small single-shaft turbojet engine. Military versions produce up to 2,950 lb_f (13.1 kN) of thrust dry, afterburning variants can reach up to 5,000 lb_f (22 kN). The engine, depending upon additional equipment and specific model, weighs from 300 to 500 pounds (140 to 230 kg). It is one of GE's most successful and longest in service military jet engines, the civilian versions having logged over 16.5 million hours of operation. The United States Air Force plans to continue using the J85 in aircraft through 2040. Civilian models, known as the CJ610, are similar but supplied without an afterburner, while the CF700 adds a rear-mounted fan for improved fuel economy.

Design and development [edit]

The J85 was originally designed to power a large decoy missile, the McDonnell ADM-20 Quail. The Quail was designed to be released from a B-52 Stratofortress in-flight and fly for long distances in formation with the launch aircraft, multiplying the number of targets facing the SA-2 surface-to-air missile operators on the ground. This mission demanded a small engine that could nevertheless provide enough power to keep up with the jet bomber. Like the similar Armstrong Siddeley Viper being built in England, the engine on a Quail drone had no need to last for extended periods of time, so therefore could be built of low-quality materials.

The fit was a success on the Quail, but again like the Viper it was later built with normal grade materials and subsequently used to power small jet aircraft, including the Northrop T-38 Talon, Northrop F-5, Canadair CT-114 Tutor, and Cessna A-37 Dragonfly light attack aircraft. More recently, J85s have powered the Scaled Composites White Knight aircraft, the carrier for the Scaled Composites SpaceShipOne spacecraft, and the Me 262 Project.

The basic engine design is quite small, about 18 inches (46 cm) in diameter, and 45 inches (110 cm) long.^{[citation needed]} It features an eight-stage axial-flow compressor powered by two turbine stages, and is capable of generating up to 2,950 lb_f (13.1 kN) of dry thrust, or more with an afterburner. At full throttle at sea level, this engine, without afterburner, consumes approximately 400 US gallons (1,500 L) of fuel per hour. At cruise altitude and power, it consumes approximately 100 US gal (380 L) per hour.

Several variants were produced. The J85-21 variant added a stage ahead of the base 8-stage compressor for a total of 9 stages, improving thrust.

Variants [edit]

J85-GE-1

2,600 lb_f (12 kN) thrust

J85-GE-3

2,450 lb_f (10.9 kN) thrust

J85-GE-4

2,950 lb_f (13.1 kN) thrust

J85-GE-5

2,400 lb_f (11 kN) thrust, 3,600 lb_f (16 kN) afterburning thrust

J85-GE-5A

3,850 lb_f (17.1 kN) afterburning thrust

J85-GE-7

2,450 lb_f (10.9 kN) thrust

J85-GE-13

4,080 lb_f (18.1 kN), 4,850 lb_f (21.6 kN) thrust

J85-GE-15

4,300 lb_f (19 kN) thrust

J85-CAN-15

Orenda manufactured J85-GE-15 for the Canadair CF-116 4,300 lb_f (19 kN) thrust

J85-GE-17A

2,850 lb_f (12.7 kN) thrust

J85-GE-21

3,500 lb_f (16 kN) military thrust; 5,000 lb_f (22 kN) afterburning thrust

J85-CAN-40

Manufactured by Orenda for the Canadair CT-114 Tutor, 2,650 lb_f (11.8 kN) thrust

CJ610

Civilianised J85

CF700

Aft fan variant of the CJ610

Applications [edit]

Scaled Composites White Knight sporting two General Electric J85 afterburning engines

• Fairchild C-123 Provider
• Canadair CL-41 Tutor
• Canadair CF-5
• Cessna A-37 Dragonfly
• Fiat G.91Y
• North American T-2 Buckeye
• Northrop F-5
• Northrop T-38 Talon
• Ryan XV-5 Vertifan
• Saab 105Ö
• Scaled Composites White Knight
• Viperjet MKII

Other [edit]

Messerschmitt Me 262A-1c reproduction, powered with a pair of GE J85 turbojets

• American Challenge water speed record jet-powered boat - Two J85-GE-21s^[1]
• Messerschmitt Me-262A-1c and B-1c. The "c" suffix stands for the flyable reproductions equipped with the J85-derived CJ610 engine instead of the original Junkers Jumo 004 jet engine.

Specifications [edit]

A J85 engine sectioned for display

Data from^{[citation needed]}

General characteristics

• Type: Turbojet engine (with or without afterburner)
• Length: 45.4–51.1 in (115–130 cm) (depending on accessory equipment installed)
• Diameter: 17.7 in (45 cm)
• Dry weight: 396–421 lb (180–191 kg) (depending on accessory equipment installed)

Components

• Compressor: 8 stages (9 in J85-21) axial
• Combustors: annular
• Turbine: 2 stages
• Fuel type: jet fuel

Performance

• Maximum thrust: 2,850–3,100 lb_f (12.7–14 kN) (dry)
• Overall pressure ratio: 8.3
• Turbine inlet temperature: 977C
• Specific fuel consumption: 0.96 - 0.97 lb/(lbf·h) (27 g/kN·s)
• Thrust-to-weight ratio: 7.5 (-21), 6.6 (-5), 6.8 (-13), 7 (-15)

See also [edit]

Related development

• General Electric CJ610
• General Electric CF700

Comparable engines

• Continental J69
• Fairchild J83

Related lists

• List of aircraft engines

References [edit]

• Gunston, Bill (2006). World Encyclopedia of Aero Engines, 5th Edition. Phoenix Mill, Gloucestershire, England, UK: Sutton Publishing Limited. ISBN 0-7509-4479-X. 

External links [edit]

Wikimedia Commons has media related to: General Electric J85

• GE J85 product page
• J85 picture

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