Allison J35 Explained

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 7400lbf.

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] 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 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 10900abbr=onNaNabbr=on thrust.

Variants

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

J35-GE-2: 3820lbf thrust, prototypes built by General Electric.

J35-GE-7: 3745lbf thrust, built by General Electric, powered the 2 Republic XP-84 Thunderjet prototypes

J35-GE-15: 4000lbf thrust, built by General Electric, powered the sole Republic XP-84A Thunderjet

J35-A-3: 4000lbf thrust

J35-C-3: 3820lbf thrust, production by Chevrolet.

J35-C-3: 4000lbf thrust, production by Chevrolet.

J35-A-4: Similar to -29, 4000lbf thrust

J35-A-5: 4000lbf thrust

J35-A-9: 4000lbf thrust

J35-A-11: Similar to -29, 6000lbf thrust

J35-A-13: 5200lbf thrust

J35-A-13C:

J35-A-15: Similar to -29, 4000lbf thrust, powered the 15 Republic YP-84 Thunderjets

J35-A-15C: 4000lbf thrust

J35-A-17: Similar to -29, 4900lbf thrust

J35-A-17A: Similar to -29, 5000lbf thrust

J35-A-17D: 5000lbf thrust

J35-A-19: Similar to -17, 5000lbf thrust

J35-A-21: Similar to -35, 5600lbf thrust, 7400lbf with afterburner

J35-A-21A: Similar to -35, 5600lbf thrust, 7400lbf with afterburner

J35-A-23: Similar to -29, 10900lbf thrust, original designation for the Allison J71

J35-A-25: Similar to -29, 5000lbf thrust

J35-A-29: 5560lbf thrust

J35-A-33: Similar to -35, 5600lbf thrust, 7400lbf with afterburner, without anti-icing

J35-A-33A: Similar to -35, 5600lbf thrust, 7400lbf with afterburner, without anti-icing

J35-A-35: 5440lbf thrust, 7200lbf with afterburner

J35-A-41: Similar to -35, 5600lbf thrust, 7400lbf with afterburner, with anti-icing

Model 450:company designation for J35 series engines.

General Electric 7E-TG-180-XR-17A : ca 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

Further reading

• Book: Kay, Anthony L.. Turbojet History and Development 1930–1960 Volume 2:USSR, USA, Japan, France, Canada, Sweden, Switzerland, Italy and Hungary . The Crowood Press. Ramsbury. 2007. 1st. 978-1861269393.
• Foremost American Turbojet : Some Details of the Slim, Axial-flow J-35 . Flight and Aircraft Engineer . 5 August 1948 . LIV . 2067 . 163 . 16 March 2019.

Notes and References

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