General Electric CJ805
| CJ805 | |
|---|---|
 |
|
| A CJ805-3A turbojet installed on a Convair 880 airliner | |
| Type |
Turbojet (CJ805) Turbofan (CJ805-23) |
| National origin | United States |
| Manufacturer | General Electric Aircraft Engines |
| Major applications |
CJ805: Convair 880 CJ805-23: Convair 990 |
| Developed from | General Electric J79 |
The General Electric CJ805 is a jet engine which was developed by GE Aviation in the late 1950s. It was a civilian version of the J79 and differed only in detail. It was developed in two versions. The basic CJ805-3 was a turbojet and powered the Convair 880, while CJ805-23 (military designation TF35), a turbofan derivative, powered the Convair 990 airliners.
The CJ805-3 engine was General Electric's entry into the commercial engine business. Its application, the Convair 880, followed very soon after the military J79, on which it was based, entered service. An RB-66, with CJ805-3 engines installed, gained experience for airline use by flying simulated airline routes.
The engine was fitted with a thrust reverser and noise-suppressing nozzle. Focus on commercial jet engine noise, and the requirement for noise suppressors, was very real before the Boeing 707 went into service 2 years before the Convair 880. There was already a lawsuit, by residents around Newark airport, concerning the noise from existing propeller-driven aircraft such as the Super Constellation, Stratocruiser and DC-7C.
Transatlantic service needed a higher thrust version of the existing turbojet and a demonstrator engine with a single-stage front fan attached to the compressor was run. It was difficult to start and operate. This experience led to the aft-fan which didn't compromise the operation of the gas generator.
Although nowhere near as successful as the Pratt & Whitney JT3D, the CJ805-23 was a very advanced engine for its time (late 50's). Like the JT3D, the CJ805-23 was a turbofan derived from a turbojet. General Electric's approach was to take the single spool CJ805-3 turbojet and incorporate an aft fan/turbine system into the exhaust system. Each turbine blade was an integral part of a blucket, the outboard section of which was a fan rotor blade. Running freely on a stub shaft, a series of bluckets, mounted on a disc, made up the aft rotor assembly. The efflux from the turbojet expanded through the (inner) turbine annulus. thus providing power directly to the fan blades located in the outer annulus. A full-length cowl, an annular exhaust system and a bucket thrust-reverser were fitted for the Convair 990. A relatively short fan cowl and thrust reverser was used to demonstrate the engine on the Sud Aviation Caravelle. The CJ805-23, if chosen, would have replaced the Rolls-Royce Avon. Rolls-Royce quickly built and tested an aft-fan demonstrator Avon to compete with the greater thrust and lower sfc of the CJ805-23. In the end the Caravelle was re-engined with the P&W JT8D turbofan.
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