THE SUBSEQUENT HISTORY OF THE CJ805-23 AND THE JT3D

Although GE’s CJ805-23 was the first flight-qualified turbofan engine, it was not the first to enter commercial service. Because it weighed 1000 pounds more than the CJ805 turbojet, it could not be installed on the Convair 880. It did fit both the 707 and the DC-8, but P&W’s rapid response pre-empted any chance for its replacing the JT3C on either of these aircraft. The CJ805-23 thus had to await the development of a new aircraft, the Convair 990, to enter service. First flight was scheduled for Fall of 1960, with production deliveries scheduled for March, 1961. Aerodynamic performance problems with the aircraft ended up moving the latter date back to September, 1962. Ultimately only 37 Convair 990s were sold. GE attempted to have the CJ805-23 introduced on the Caravelle, replacing the Rolls – Royce Avon, but this too fell through. The breakthrough turbofan engine ended up without an aircraft to fly on.82

The CJ805-23 had some problems in the field. Leakage from the hot turbine stream to the cold fan stream proved more of a problem on production engines than it had on the prototype, necessitating some minor redesign. More seriously, the turbofan bluckets began suffering thermal fatigue cracks, owing to the combination of transient thermal stresses (during start-up and shutdown) and the opposite camber of the fan and turbine blading. For a while the blucket thermal fatigue problem looked like it might be a fundamental fact of bluckets and hence not solvable at all, threatening to create a small financial disaster for GE.83 The problem was solved, but it surely did not help GE convince anyone to consider the engine on other aircraft. The last CJ805-23 was shipped in 1962. Its great engineering achievement notwithstanding, it was by all standards a commercial failure. The contrast between this outcome and the commercial success of P&W’s JT3D led Jack Parker, the head of GE Aerospace and Defense, to remark, “We converted the heathen but the competitor sold the bibles.”84 The fan design of the CJ805-23, however, had a more illustrious history. A scaled-down version of it was installed behind GE’s small J-85 engine to form the CF-700, a 4000 pound thrust engine. This engine flew on business jets into the 1990s, most notably the Falcon 20F and the Sabre 75A. The commercial failure of the CJ805-23 was not the fault of the fan design.

P&W’s JT3D entered service on the Boeing 707 in July, 1960, more than two years before the CJ805-23. Shortly thereafter it began powering Boeing 720B’s and DC-8’s, and the TF-33 entered service on the KC-135 and the eight-engine B-52H bomber, of which the military had ordered 102 in September 1959, and a few years later on the Lockheed C-141. JT3D-powered 707s were still in service into the 1990s, and the TF-33-powered B-52 served in the Persian Gulf War. P&W had delivered 8550 JT3D’s, including JT3C conversions, by 1983. Its success was outdone only by P&W’s JT8D, designed in 1959 on largely the same basis as the JT3D, with more than 13,000 delivered.