General Electric J85

"J85 redirects here, for the British Halcyon class minesweeper, see HMS Seagull (J85), for the Abscess of lung and mediastinum ICD-10 code, see ".-----

The General Electric J85 is a small single-shaft turbojet engine. Military versions produce up to 2,950 lbf (18 kN) of thrust dry, afterburning variants can reach up to 5,000 lbf (22 kN). The engine, depending upon additional equipment and specific model, weighs between 300 to 500 pounds (140 kg to 230 kg), giving it the highest thrust-to-weight ratio of any production turbojet in the world.Fact|date=August 2008 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 CJ700 adds an uncommon rear-mounted fan for improved fuel economy.

Development

The J85 was originally designed to power a large decoy aircraft, 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 operators on the ground. This mission demanded a small engine that could nevertheless provide enough power to keep up with the jet bomber. Unlike the similar Armstrong Siddeley Viper being built in England,Fact|date=July 2008 the engine on a Quail drone did not have to last for extended periods of time, so therefore could be built of low-quality materials.Fact|date=July 2008

The fit was a success on the Quail, and would subsequently be used on small jet aircraft, including the T-38 Talon, Northrop F-5, Canadair CT-114 Tutor, and Cessna A-37 Dragonfly light attack aircraft. More recently, J85s are used on the Scaled Composites White Knight aircraft, the carrier for the Scaled Composites SpaceShipOne spacecraft, and the aircraft in the US Me 262 Project

The basic engine design was quite small, about 18 inches (46 cm) in diameter, and 45 inches long (114 cm).((cn)) It featured an eight-stage axial-flow compressor powered by two turbine stages. It is capable of generating up to 2,950 lbf (18 kN) of dry thrust, or more with an afterburner. At full throttle at sea level, this engine, without afterburner, consumes approximately 400 gallons of fuel per hour. At cruise altitude and power, it consumes approximately 380 litre / 100 gallons 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.

Applications

* A-37 Dragonfly
* Canadair CL-41 Tutor
* Northrop F-5
* Scaled Composites White Knight
* T-38 Talon
* Saab 105Ö

Other

* American Challenge water speed record jet-powered boat - Two J85-GE-21 [ [http://www.popularmechanics.com/outdoors/boating/1277281.html?page=2 400 Mph On Water - Popular Mechanics ] ]

pecifications

jetspecs

type=Afterburning turbojet engine
length= 45.4 to 51.1 inches (depending on accessory equipment installed)
diameter=17.7 inches
weight=396 - 421 pounds (depending on accessory equipment installed)
compressor= 8 stages (9 in J85-21)
combustion= annular
turbine= 2 stages
fueltype=
oilsystem=
power=
thrust= 2850 - 3100 lbf thrust (dry)
compression=
aircon= 45 lb/s
turbinetemp=
fuelcon=
specfuelcon= 0.96 - 0.97
power/weight=
thrust/weight=7.5(-21),6.6(-5),6.8(-13),7(-15)

Versions

* J85-GE-3: 2,450 lbf (10.9 kN) thrust
* J85-GE-4: 2,950 lbf (13.1 kN) thrust
* J85-GE-5A: 3,850 lbf (17.1 kN) afterburning thrust
* J85-GE-13: 4,080 lbf
* J85-GE-15: 4,300 lbf
* J85-GE-21: 5,000 lbf

References

External links

* [http://www.geae.com/engines/military/j85/index.html GE J85 product page]
* [http://www.aircraftenginedesign.com/pictures/j85.gifJ85 picture]
* [http://www.aircraftenginedesign.com/pictures/CF700.gifCF700 picture]