{{short description|1950s British turbojet aircraft engine}} {{Use dmy dates|date=February 2018}} {{Use British English|date=February 2018}} {{lowercase title|title=de Havilland Gyron Junior}} {{infobox aero engine |name= Gyron Junior |image=File:DH Gyron Junior DHAM.jpg |caption=de Havilland Gyron Junior at the de Havilland Aircraft Museum |engine_type=Turbojet |manufacturer= de Havilland Engine Company |first_run= August 1955<ref name="Gunston" >{{cite book |title=World Encyclopaedia of Aero Engines |last= Gunston |first= Bill |year=1989 |publisher=Patrick Stephens |location= Wellingborough |isbn=1-85260-163-9 |ref=Gunston, Encycl. |pages=52 }}</ref> |major_applications= {{ubl | Blackburn Buccaneer | Bristol 188 }} |number_built = 89 |developed_from = de Havilland Gyron |developed_into = |variants_with_their_own_articles = }}

The '''de Havilland Gyron Junior''' is 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.

== Design and development == 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.<ref>''Flight'' "Aeroengines 1960"</ref>

It powered the Blackburn Buccaneer S.1 twin-engined Naval strike aircraft. The engine was rather unreliable and considered short of thrust.<ref name =eeles>"A Passion For Flying"Tom Eeles, Pen & Sword Books Ltd. 2008, {{ISBN|978 1 84415 688 7}}, p.42</ref> 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.<ref name=eeles/> 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.<ref>"From Spitfire To Eurofighter" Roy Boot, Airlife Publishing Ltd. Shrewsbury< {{ISBN|1 85310 093 5}}, p.133</ref>

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 to an end the use of Gyron Junior.<ref name=eeles/>

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 with continuously variable thrust up to full reheat; others increased thrust in discrete steps.<ref>{{cite web |url=https://www.flightglobal.com/pdfarchive/view/1962/1962%20-%200700.html |title=1962 {{!}} 0700 {{!}} Flight Archive |website=www.flightglobal.com |url-status=dead |archive-url=https://web.archive.org/web/20160224235930/https://www.flightglobal.com/pdfarchive/view/1962/1962%20-%200700.html |archive-date=2016-02-24}} </ref> The programme 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.

==Variants== ''Ref:''<ref name="Gunston" /> ;Gyron Junior DGJ.1: (or P.S.43) ;Gyron Junior DGJ.2: (Mk.101) Interim production stage, used on Buccaneer S. Mk.1.<ref name=JAWA62-63>{{cite book|last=Taylor|first=John W.R. FRHistS. ARAeS|title=Jane's All the World's Aircraft 1962-63|year=1962|publisher=Sampson, Low, Marston & Co Ltd|location=London}}</ref> Variable inlet and guide vane, annular manifold for flap blowing, {{convert|121|in|m|abbr=on}} long overall ;Gyron Junior DGJ.10:Exhibited in 1958 at Farnborough, longer than the DJG.1<ref>{{citation |journal=Flight |url=http://www.flightglobal.com/FlightPDFArchive/1958/1958-1-%20-%200183.PDF |title=A New Gyron Junior |date=August 1958}}</ref><ref name=JAWA62-63/> ;Gyron Junior DGJ.10R: (or P.S.50) highly augmented afterburning version for the Bristol 188, dry thrust 10,000&nbsp;lb, wet thrust 14,000&nbsp;lb (62.3&nbsp;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 {{convert|191|in|m|abbr=on}}<ref>{{citation |journal=Flight |url=http://www.flightglobal.com/pdfarchive/view/1960/1960%20-%200370.html |title=Aeroengines 1960 |date=18 March 1960}}</ref> ;Gyron Junior DGJ.20:<ref name=JAWA62-63/>

== Applications == * Avro 732 : Intended application, not built<ref>{{Cite web |last=Buttler |first=Tony |date=15 January 2024 |title=Tony Buttler examines the scale test-beds that preceded the Victor and the Vulcan – and V-bombers that might have been |url=https://www.key.aero/article/vulcan-and-victor-their-mini-delta-precursors |website=Key.aero}}</ref>

* Blackburn Buccaneer S.1 : 40 aircraft built<ref name="Jackson, Blackburn Aircraft, p494" >{{cite book |title=Blackburn Aircraft since 1909 |last=Jackson |first=A.J. |year=1968 |publisher=Putnam Publishing |location=London |isbn=0-370-00053-6 |ref=Jackson, Blackburn Aircraft

|pages=494 }}</ref>

* Bristol 188 : Only 2 built

* Gloster Javelin : Testing only, 1 production FAW Mk.1 modified<ref name="James, Gloster Aircraft, pp322" >{{cite book |title= Gloster Aircraft since 1917 |last= James |first=Derek N. |year=1971 |publisher=Putnam Publishing |location=London |isbn= 0-370-00084-6 |ref=James, Gloster Aircraft

|pages=322, 326, 370 }}</ref>

* Saunders-Roe SR.177 : Intended application, not built

==Engines on display== A de Havilland Gyron Junior is on display at the de Havilland Aircraft Museum, 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''.<ref>[http://gatwick-aviation-museum.co.uk/Buccaneer/bucc.html Gatwick Aviation Museum - Buccaneer S.1] {{Webarchive|url=https://web.archive.org/web/20160316005224/http://www.gatwick-aviation-museum.co.uk/Buccaneer/bucc.html |date=16 March 2016 }} Retrieved: 23 February 2012</ref>

== Specifications (Gyron Junior DGJ.10) == thumb|Rear view {{jetspecs|<!-- If you do not understand how to use this template, please ask at Wikipedia talk:WikiProject Aircraft --> <!-- Please include units where appropriate (main comes first, alt in parentheses). If data are missing, leave the parameter blank (do not delete it). For additional lines, end your alt units with )</li> and start a new, fully-formatted line with <li> --> |ref= ''Gunston and Jane's All the World's Aircraft 1962-63.''<ref name="Gunston" /><ref name=JAWA62-63/> |type=Single-spool after-burning turbojet |length={{cvt|102.9|in|cm|1}} |diameter={{cvt|41.1|in|cm|1}} |weight={{cvt|3100|lb}} |compressor=7-stage axial flow with Variable Inlet Guide Vanes (VIGV) |combustion= Annular combustion chamber with 13 spill-type burners |turbine=Two-stage axial flow |fueltype=Aviation kerosene |oilsystem=Pressure spray/splash with scavenging |power= |thrust={{convert|10000|lbf|kN|abbr=on}} dry, {{convert|14000|lbf|kN|abbr=on}} wet at sea level, {{convert|20000|lbf|kN|abbr=on}}+ at M2.5+ at {{convert|36000|ft|m|abbr=on}} |compression= '''DGJ.1:''' 6.4:1<ref name="Gunston" /> |aircon= '''DGJ.1:''' {{cvt|123|lb/s|kg/s}} |turbinetemp= |fuelcon= |specfuelcon= |power/weight= |thrust/weight=3.23 dry, 4.52 wet at sea level, 6.45+ at M2.5+ at {{convert|36000|ft|m|abbr=on}} }}

==See also== {{aircontent <!-- other related articles that have not already linked: --> |see also=

<!-- designs which were developed into or from this aircraft: --> |related= * de Havilland Gyron

<!-- For aircraft engine articles. Engines that are of similar to this design: --> |similar engines= * Armstrong Siddeley Sapphire

<!-- relevant lists that this aircraft appears in: --> |lists= *List of aircraft engines <!-- See WP:Air/PC for more explanation of these fields. --> }}

==References== {{reflist}}

==External links== {{commons category}} * [http://www.airmuseumsuk.org/museum/dhengine/800/pages/109%20DH%20Gyron%20Junior.htm Photo of DH Gyron Junior] * [https://web.archive.org/web/20110411103418/http://www.enginehistory.org/Museums/de%20Havilland/Gyron%20Junior%206.jpg Photo of Gyron Junior] * [http://www.leteckemotory.cz/motory/gyron-junior Gyron Junior on LeteckeMotory.cz] (cs)

{{De Havilland aeroengines}} {{Bristol aeroengines}}

Gyron Junior Category:Bristol aircraft engines Category:1950s turbojet engines