Allison J35

J35
	An Allison J35 at Aalborg, Denmark
Type	Turbojet
National origin	United States
Manufacturer	General Electric ; Allison Engine Company
First run	1946
Major applications	North American FJ-1 Fury ; Northrop F-89 Scorpion ; Northrop YB-49 ; Republic F-84 Thunderjet
Number built	14,000
Developed into	Allison J71; General Electric J47

The General Electric/Allison J35 was the United States Air Force's first axial-flow (straight-through airflow) compressor jet engine. Originally developed by General Electric (GE company designation TG-180) in parallel with the Whittle-based centrifugal-flow J33, the J35 was a fairly simple turbojet, consisting of an eleven-stage axial-flow compressor and a single-stage turbine. With the afterburner, which most models carried, it produced a thrust of 7,400 lbf (33 kN).

Like the J33, the design of the J35 originated at General Electric, but major production was by the Allison Engine Company.

Design and development

While developing the T31 axial turboprop in 1943 General Electric realized that they had the resources to design an axial flow turbojet at the same time as their centrifugal-flow J33 engine. They recognized the axial would have more potential for the future and went ahead with the TG-180 engine.^[1] GE axial compressor designs were developed from the NACA 8-stage compressor.^[2]

Sectioned J35 at the National Naval Aviation Museum, Pensacola, FL. The 11-stage compressor is painted blue (the stators have been removed), the combustors are red, the turbine is unpainted. The teardrop-shaped openings along the outer edge of the turbine are the air channels used to cool the blades.

Cutaway of J35 combustor dome

Cutaway of J35 fuel atomizer

The engine had its starter and accessories (fuel control, fuel pump, oil pumps, hydraulic pump, RPM generator)^[3] mounted in the center of the compressor inlet. This accessory layout, as used on centrifugal engines, restricted the area available for compressor inlet air. It was carried over to the J47 but revised (relocated to an external gearbox) on the J73 when a 50% increase in airflow was required.^[4] It also had an inlet debris guard which was common on early jet engines.

GE developed a variable afterburner for the engine, although electronic control linked with engine controls had to wait until the J47.^[5] Marrett describes one of the potential consequences of manual control of the engine and afterburner on a turbine engine: if the afterburner lit but the pilot failed to ensure the nozzle opened, the RPM governor could overfuel the engine until the turbine failed.^[6]

Operational history

The General Electric J35 first flew in the Republic XP-84 Thunderjet in 1946. Late in 1947, complete responsibility for the development and production of the engine was transferred to the Allison Division of the General Motors Corporation and some J35s were also built by GM's Chevrolet division. More than 14,000 J35s had been built by the time production ended in 1955.

The J35 was used to power the Bell X-5 variable-sweep research aircraft and various prototypes such as the Douglas XB-43 Jetmaster, North American XB-45 Tornado, Convair XB-46, Boeing XB-47 Stratojet, Martin XB-48, and Northrop YB-49. It is probably best known, however, as the engine used in two of the leading fighters of the United States Air Force (USAF) in the 1950s: the Republic F-84 Thunderjet and the Northrop F-89 Scorpion.

A largely redesigned development, the J35-A-23, was later produced as the Allison J71, developing 10,900 lbf (48.49 kN) thrust.

Variants

Data from: Aircraft Engines of the World 1953,^[7] Aircraft Engines of the World 1950^[8]

J35-GE-2: 3,820 lbf (17.0 kN) thrust, prototypes built by General Electric.
J35-GE-7: 3,745 lbf (16.66 kN) thrust, built by General Electric, powered the 2 Republic XP-84 Thunderjet prototypes
J35-GE-15: 4,000 lbf (18 kN) thrust, built by General Electric, powered the sole Republic XP-84A Thunderjet
J35-A-3: 4,000 lbf (18 kN) thrust
J35-C-3: 3,820 lbf (17.0 kN) thrust, production by Chevrolet.
J35-C-3: 4,000 lbf (18 kN) thrust, production by Chevrolet.
J35-A-4: Similar to -29, 4,000 lbf (18 kN) thrust
J35-A-5: 4,000 lbf (18 kN) thrust
J35-A-9: 4,000 lbf (18 kN) thrust
J35-A-11: Similar to -29, 6,000 lbf (27 kN) thrust
J35-A-13: 5,200 lbf (23 kN) thrust
J35-A-13C
J35-A-15: Similar to -29, 4,000 lbf (18 kN) thrust, powered the 15 Republic YP-84 Thunderjets
J35-A-15C: 4,000 lbf (18 kN) thrust
J35-A-17: Similar to -29, 4,900 lbf (22 kN) thrust
J35-A-17A: Similar to -29, 5,000 lbf (22 kN) thrust
J35-A-17D: 5,000 lbf (22 kN) thrust
J35-A-19: Similar to -17, 5,000 lbf (22 kN) thrust
J35-A-21: Similar to -35, 5,600 lbf (25 kN) thrust, 7,400 lbf (33 kN) with afterburner
J35-A-21A: Similar to -35, 5,600 lbf (25 kN) thrust, 7,400 lbf (33 kN) with afterburner
J35-A-23: Similar to -29, 10,900 lbf (48 kN) thrust, original designation for the Allison J71
J35-A-25: Similar to -29, 5,000 lbf (22 kN) thrust
J35-A-29: 5,560 lbf (24.7 kN) thrust
J35-A-33: Similar to -35, 5,600 lbf (25 kN) thrust, 7,400 lbf (33 kN) with afterburner, without anti-icing
J35-A-33A: Similar to -35, 5,600 lbf (25 kN) thrust, 7,400 lbf (33 kN) with afterburner, without anti-icing
J35-A-35: 5,440 lbf (24.2 kN) thrust, 7,200 lbf (32 kN) with afterburner
J35-A-41: Similar to -35, 5,600 lbf (25 kN) thrust, 7,400 lbf (33 kN) with afterburner, with anti-icing
Model 450: company designation for J35 series engines.
General Electric 7E-TG-180-XR-17A: ca 1,740 hp (1,300 kW) gas power, gas generator for the Hughes XH-17.

Applications

Bell X-5
Boeing XB-47 Stratojet
Convair XB-46
Douglas D-558-1 Skystreak
Douglas XB-43 Jetmaster
Fiat G.80 (proposal only)
Hughes XH-17 (experimental helicopter)
Martin XB-48
North American FJ-1 Fury
North American XB-45 Tornado
North American XP-86 Sabre
Northrop F-89 Scorpion
Northrop YB-49
Republic F-84 Thunderjet
Vought F7U-3 Cutlass (interim test usage)

Engines on display

Allison J35 is on public display at Texas Air Museum - Stinson Chapter, San Antonio, Texas
Allison J35 is on public display at San Jose State University, San Jose, California
Allison J35 is on public display at Flyhistorisk Museum, Sola, Norway

Specifications (J35-A-35)

Data from ,^[9] Aircraft engines of the World 1957^[10]

General characteristics

Type: Afterburning turbojet
Length: 195.5 in (4,970 mm) including afterburner
Diameter: 37 in (940 mm)
Frontal area: 7.5 sq ft (0.70 m²)
Dry weight: 2,315 lb (1,050 kg) without afterburner; 2,930 lb (1,330 kg) including afterburner

Components

Compressor: 11-stage axial compressor
Combustors: eight tubular inter-connected combustion chambers
Turbine: single-stage axial turbine
Fuel type: aviation kerosene, JP-4, MIL-F-5624 or 100/130 octane gasoline
Oil system: dry sump pressure system with spur gear pressure and scavenge pumps at 35 psi (240 kPa)

Performance

Maximum thrust: (dry): 5,600 lbf (25 kN) for take-off at 8,000 rpm
Maximum thrust (wet): 7,500 lbf (33 kN) for take-off at 8,000 rpm
Overall pressure ratio: 5:1
Air mass flow: 95 lb/s (2,600 kg/min) at take-off power
Specific fuel consumption: 1.1 lb/(lbf⋅h) (31 g/(kN⋅s)) dry; 2 lb/(lbf⋅h) (57 g/(kN⋅s)) wet
Thrust-to-weight ratio: 2.63
Maximum operating altitude: 50,000 ft (15,000 m)
Cost: US$ 46,000 each

References

^ Gunston, Bill (2006). The development of jet and turbine aero engines (4 ed.). Sparkford: PSL. p. 143. ISBN 0750944773.
^ Dawson, Virginia P. (1991). "SP-4306 Engines and Innovation: Lewis Laboratory and American Propulsion Technology Chapter 3 : Jet Propulsion: Too Little, Too Late". history.nasa.gov. Washington, D.C.: National Aeronautics and Space Administration Office of Management Scientific and Technical Information Division. Retrieved 16 March 2019.
^ "AERO ENGINES 1956". Flight and Aircraft Engineer. 69 (2468): 567–597. 11 May 1956. Retrieved 16 March 2019.
^ "Aero Engines 1957". Flight and Aircraft Engineer. 72 (2531): 111–143. 26 July 1957. Retrieved 16 March 2019.
^ General Electric Company (1979). Seven Decades of Progress: A Heritage of Aircraft Turbine Technology (1st ed.). Fallbrook: Aero Publishers Inc. p. 76. ISBN 0-8168-8355-6.
^ Marrett, George J. (2006). Testing death : Hughes Aircraft test pilots and Cold War weaponry (1st ed.). Naval Institute Press. p. 21. ISBN 978-1-59114-512-7.
^ Wilkinson, Paul H. (1953). Aircraft Engines of the World 1953 (11th ed.). London: Sir Isaac Pitman & Sons Ltd. pp. 60–62.
^ Wilkinson, Paul H. (1950). Aircraft Engines of the World 1950 (11th ed.). London: Sir Isaac Pitman & Sons Ltd. pp. 48–49.
^ Bridgman, Leonard (1955). Jane's all the World's Aircraft 1955–56. London: Jane's all the World's Aircraft Publishing Co. Ltd.
^ Wilkinson, Paul H. (1957). Aircraft engines of the World 1957 (15th ed.). London: Sir Isaac Pitman & Sons Ltd. pp. 70–71.