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| General Electric CJ805 | |
|---|---|
| Name | General Electric CJ805 |
| Type | Axial-flow turbojet |
| Manufacturer | General Electric |
| First run | 1955 |
| Status | Retired |
| Used in | Boeing 707 (civil versions), Boeing 720 (civil versions), Lockheed L-188 Electra (testbed), Convair 880 (development testbed) |
General Electric CJ805
The General Electric CJ805 was a civilian derivative of the military General Electric J79 axial-flow turbojet developed in the 1950s by General Electric for use on passenger transport aircraft during the early Jet Age. It powered transcontinental and transoceanic airliner projects and competed with powerplants from Rolls-Royce, Pratt & Whitney, and Snecma in the burgeoning post-World War II commercial aviation market. The engine's design adaptations sought to balance military performance heritage with the reliability and efficiency demands of Pan American World Airways, Trans World Airlines, and other carriers.
The CJ805 traceable lineage began with the military General Electric J79 program, which powered aircraft such as the McDonnell Douglas F-4 Phantom II and the Convair B-58 Hustler. General Electric engineers led by program managers engaged with airframe manufacturers like Boeing, Douglas Aircraft Company, and Lockheed Corporation to develop a civil variant suitable for the Boeing 707 and other jetliners. The CJ805 incorporated a single-spool axial compressor and a centrifugal-flow-derived turbine arrangement adapted from turbine technologies proven in the J79 and earlier I.A.E. collaborations. Design priorities reflected requirements from Civil Aeronautics Board certification processes and airline operating economics favored by American Airlines and United Airlines route planners.
Civil adaptations addressed bypass airflow by adding a fan or ejector system in later variants, drawing on research from NASA and test programs with Pratt & Whitney and Rolls-Royce engines. Material choices incorporated high-temperature alloys developed in cooperation with suppliers like Carpenter Technology Corporation and testing was conducted at General Electric Flight Test facilities and wind tunnels at Langley Research Center. Certification involved compliance with Federal Aviation Administration standards and coordination with regulatory bodies across United Kingdom and France for export models.
The CJ805 family split into several principal variants, each tailored to specific airframe needs and airline contracts. The CJ805-3 featured a straight turbojet core for high-speed service attractive to carriers such as Trans World Airlines and the CJ805-23 introduced a low-pressure booster and fan arrangement aimed at improved fuel consumption sought by Pan American World Airways. A long-range derivative tested with variable inlet designs borrowed experience from the J79-GE-17 military line and collaborative studies with Société Nationale d'Étude et de Construction de Moteurs d'Aviation engineers. Experimental versions incorporated afterburning systems similar to those on the J79 to explore thrust augmentation for heavy takeoff conditions, with testbeds using Boeing 720 and Convair 880 airframes.
Typical specifications for the civil CJ805 variants included an axial compressor stage count and turbine stage arrangement inherited from the J79 core, producing sea-level static thrust ratings competitive with contemporaries from Rolls-Royce Avon and Pratt & Whitney JT3C. Core features included forged disk technology supplied by Wyman-Gordon, chrome-nickel alloys from Allegheny Ludlum, and fuel control systems developed with Honeywell instrumentation standards. The CJ805's specific fuel consumption and thrust-to-weight ratio were focal points in airline evaluations alongside maintenance intervals influenced by Society of Automotive Engineers component standards. Accessory gearbox architecture followed conventions used in major civil platforms certified under Civil Air Regulations.
The CJ805 entered airline service in the late 1950s and early 1960s, coinciding with fleet expansions by Pan American World Airways, Trans World Airlines, and European carriers modernizing with jetliners from Boeing and Douglas. Operational records show that early deployments confronted fuel price sensitivity influenced by international route structures negotiated under Chicago Convention air services arrangements. Maintenance regimes were developed in cooperation with independent maintenance organizations such as Sabena Maintenance and major airline overhaul shops. Reliability improvements over initial service life paralleled similar maturation cycles experienced by the Rolls-Royce Conway and Pratt & Whitney JT3D programs.
The CJ805 was applied to several commercial and testbed applications. Primary installations included civil versions of the Boeing 707 and Boeing 720 aircraft derivations and experimental testbeds on prototypes like the Lockheed L-188 Electra and conversions of the Convair 880. Airlines evaluating the CJ805 weighed its performance against alternative powerplants on transatlantic services operated by Pan Am and shorter transcontinental sectors served by American Airlines and United Airlines. Cargo and military transport studies also considered the CJ805 for non-combat platforms in collaboration with agencies such as the United States Air Force logistics planners.
Accident investigations involving CJ805-powered installations were handled by national authorities including the Civil Aeronautics Board and later the National Transportation Safety Board. Notable incidents prompted airworthiness directives coordinated with Federal Aviation Administration and airframe manufacturers like Boeing and Douglas Aircraft Company to address component failures and improve inspection intervals. Findings from inquiries influenced maintenance practices adopted by carriers and overhaul facilities such as General Electric Aircraft Engines Overhaul shops and international partners.
Category:Aircraft engines Category:General Electric aircraft engines