De Havilland Gyron Junior


The de Havilland Gyron Junior was a military turbojet engine design of the 1950s developed by the de Havilland Engine Company and later produced by Bristol Siddeley. The Gyron Junior was a scaled-down derivative of the de Havilland Gyron.

Gyron Junior
de Havilland Gyron Junior at the de Havilland Aircraft Heritage Centre
Type Turbojet
Manufacturer de Havilland Engine Company
First run August 1955[1]
Major applications Blackburn Buccaneer
Bristol 188
Number built 89
Developed from de Havilland Gyron

Design and developmentEdit

The Gyron Junior was a two-fifths flow scale version of the existing Gyron engine. It started as Project Study number 43 in 1954 and the first prototype ran in August 1955.[2]

It powered the Blackburn Buccaneer S.1 twin-engined Naval strike aircraft. The engine was rather unreliable and considered short of thrust.[3] The later Buccaneer S.2 used the more powerful Rolls-Royce Spey engine.

The engine had variable inlet guide vanes, as used on many other engines, necessary for accelerating from idle to high thrust. However, on the Gyron Junior, positioning of the vanes was not reliable and could cause surging which, in turn, could prevent accelerating to higher thrust levels.[3] A possibly unique feature on this engine was valve-controlled cooling air to the turbine blades. The engine had to supply air for the aircraft's boundary layer control system and the resulting thrust loss was unacceptable. To regain the thrust the turbine temperature limit was raised by using turbine blade cooling, selected only with blowing on.[4]

In December 1970 a Buccaneer was lost after one engine surged and failed to accelerate on an overshoot and a week later another aircraft was lost after an uncontained engine failure. This last accident brought Gyron Junior flying to a halt forever.[3]

Two Gyron Juniors, with afterburners, were also used on the Bristol 188 Mach 2 supersonic research aircraft. The 188 was originally intended to have the Rolls-Royce Avon but the half ton lighter Gyron Junior was substituted in June 1957 .This engine was one of the first in the world to have infinite variation of thrust right up to full reheat. Other manufacturers using thrust increase in discrete steps.[5] The program was terminated early without achieving the high-speed high-temperature trials that had been intended. Limitations included poor fuel consumption of the Gyron Junior and engine surging. Fuel limitations restricted the time spent at its maximum speed, Mach 1.95, to a few minutes. This was not long enough to achieve the required stabilized temperatures in "thermal soaking" tests.



Gyron Junior DGJ.1
(or P.S.43)
Gyron Junior DGJ.2
(Mk.101) Interim production stage, used on Buccaneer S. Mk.1.[6] Variable inlet and guide vane, annular manifold for flap blowing, 121 in (3.1 m) long overall
Gyron Junior DGJ.10
Exhibited in 1958 at Farnborough, longer than the DJG.1[7][6]
Gyron Junior DGJ.10R
(or P.S.50) highly augmented afterburning version for the Bristol 188, dry thrust 10,000 lb, wet thrust 14,000 lb (62.3 kN). Added zero stage and two rows of variable stators. Variable nozzle with convergent, convergent/parallel or convergent/divergent configuration depending on reheat selection and aircraft speed. Overall length 191 in (4.9 m)[8]
Gyron Junior DGJ.20


40 aircraft built[9]
Only 2 built
Testing only, 1 production FAW Mk.1 modified[10]
Intended application, not built

Engines on displayEdit

A de Havilland Gyron Junior is on display at the de Havilland Aircraft Heritage Centre, London Colney, Hertfordshire.

A D.H Gyron Junior is on public display at East Midlands Aeropark.

Also on display at the Gatwick Aviation Museum, Charlwood, Surrey, two running engines can also be found here, fitted to Buccaneer S.1, XN923.[11]

Specifications (Gyron Junior DGJ.10)Edit

Data from Gunston and Jane's All the World's Aircraft 1962-63.[1][6]

General characteristics

  • Type: Single-spool after-burning turbojet
  • Length: 102.9 in (261.4 cm)
  • Diameter: 41.1 in (104.4 cm)
  • Dry weight: 3,100 lb (1,400 kg)


  • Compressor: 7-stage axial flow with Variable Inlet Guide Vanes (VIGV)
  • Combustors: Annular combustion chamber with 13 spill-type burners
  • Turbine: Two-stage axial flow
  • Fuel type: Aviation kerosene
  • Oil system: Pressure spray/splash with scavenging


  • Maximum thrust: 10,000 lbf (44 kN) dry, 14,000 lbf (62 kN) wet at sea level, 20,000 lbf (89 kN)+ at M2.5+ at 36,000 ft (11,000 m)
  • Overall pressure ratio: DGJ.1: 6.4:1[1]
  • Air mass flow: DGJ.1: 123 lb/s (56 kg/s)
  • Thrust-to-weight ratio: 3.23 dry, 4.52 wet at sea level, 6.45+ at M2.5+ at 36,000 ft (11,000 m)

See alsoEdit

Related development

Comparable engines

Related lists


  1. ^ a b c d Gunston, Bill (1989). World Encyclopaedia of Aero Engines. Wellingborough: Patrick Stephens. p. 52. ISBN 1-85260-163-9.
  2. ^ Flight "Aeroengines 1960"
  3. ^ a b c "A Passion For Flying"Tom Eeles, Pen & Sword Books Ltd. 2008, ISBN 978 1 84415 688 7, p.42
  4. ^ "From Spitfire To Eurofighter" Roy Boot, Airlife Publishing Ltd. Shrewsbury< ISBN 1 85310 093 5, p.133
  5. ^ "1962 | 0700 | Flight Archive". Archived from the original on 24 February 2016.
  6. ^ a b c d Taylor, John W.R. FRHistS. ARAeS (1962). Jane's All the World's Aircraft 1962-63. London: Sampson, Low, Marston & Co Ltd.
  7. ^ "A New Gyron Junior" (PDF), Flight, August 1958
  8. ^ "Aeroengines 1960", Flight, 18 March 1960
  9. ^ Jackson, A.J. (1968). Blackburn Aircraft since 1909. London: Putnam Publishing. p. 494. ISBN 0-370-00053-6.
  10. ^ James, Derek N. (1971). Gloster Aircraft since 1917. London: Putnam Publishing. pp. 322, 326, 370. ISBN 0-370-00084-6.
  11. ^ Gatwick Aviation Museum - Buccaneer S.1 Archived 16 March 2016 at the Wayback Machine Retrieved: 23 February 2012

External linksEdit

  • Photo of DH Gyron Junior
  • Photo of Gyron Junior
  • Gyron Junior on (cs)