The Gyron Junior was a two-fifths output scaling down of the Gyron, starting as Project Study number 43 in 1954; the first prototype Junior ran in August 1955.
Only a little more widely used than the Gyron, it did at least enter serial production for the Blackburn Buccaneer S.1 twin-engined Naval strike aircraft. However it was never a successful engine in service. The Buccaneer S.1 was criticised for being underpowered and the later and more numerous S.2 used the more powerful Rolls-Royce Spey instead.
Twin Gyron Juniors, with afterburners, were also used to power the Bristol 188 Mach 2 supersonic research aircraft. The Rolls-Royce Avon had been considered, but only the Gyron Junior was used in practice. The program was a disappointment, if not a failure, and was terminated early without achieving all of the high-speed high-temperature trials that had been intended. The limitation was the poor fuel consumption of the Gyron Junior and surging from the intakes. This could have been solved with Avons and the successful English Electric Lightning intake design, but the Avro 730 project that the 188 was a research aircraft for had been dropped as a result of the 1957 Defence White Paper which cancelled many manned aircraft designs under development as they were expected to be rendered obsolete by guided missiles. Only Mach 1.95 was achieved for a few minutes, endurance at any speed was so restricted by fuel limits that it was impossible to study the long-term "thermal soaking" of a supersonic airframe, as intended. It was big leap for de Havilland from centrifugal- to axial-flow, and was perhaps too far.
Exhibited in 1958 at Farnborough, longer than the DJG.1
Gyron Junior DGJ.10R
highly augmentation afterburning version for the Bristol 188, dry thrust 10,000 lb, wet thrust 14,000 lb s.t. (62.3 kN). Added zero stage and two rows of variable stators. Variable nozzle for convergent, parallel and divergent/convergent configuration depending on reheat and aircraft speed. Overall length 191 in (4.9 m)