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Aviation History
1957
1957 - 0294.PDF
296 FLIGHT, 8 March 1957 ON page 294 of this issue we record the establishment ofnew thrust ratings for the de Havilland Gyron turbojet.These new DGy.2 ratings of 20,000 lb dry and 25,000 lb with reheat exceed by a wide margin any thrust previouslyannounced for any other engine in the world. A commentary on the general design philosophy of the HalfordH.4, or Gyron, family appeared in our issue of September 9,1955. This class of engine was planned specifically to meet the propul-sion requirements of supersonic aeroplanes and is characterized by a moderate pressure ratio, an exceedingly high through-put perunit frontal area, and relatively massive construction to with- stand the enormous stresses imposed by high ram-air pressuresand temperatures. The first prototype engine ran on January 5, 1953, and the DGy.l rating of 15,000 lb thrust was achieved aftertype-testing in August 1955. In the same month the engine first took to the air mounted inthe lower port position on the Short Sperrin VX 158. This aero- plane has since conducted all the flight development of theGyron, and the behaviour of the engine has been fully explored up to the limits imposed by the airframe. Nine Gyrons havebeen cleared for flight and two are at present engaged in flight trials, a second unit having been installed in the starboardnacelle of the Sperrin early last year. The aircraft is normally operated by a pilot, flight engineer and two observers, and thestarting, handling and general behaviour of the Gyron have been demonstrated as exemplary. Never once has a Gyron stalled inthe air; relight trials are progressing favourably and an indica- tion of acceleration is provided by the fact that it takes but threeseconds to go from flight idling to full thrust. Engine flight hours exceed one hundred. Thrusts of the order of 20,000 1b dry were visualized at thestart of detail design back in 1950. The establishment of these ratings marks successful completion of the first stage of theengine's development, and it is worth recording that the DGy.2 figures have been attained by a unit which is fundamentallyidentical to the original engine of four years ago. No hint can be given of the performance now being recordedby later developments of the Gyron. It is, however, almost a unique situation for an engine to be available so far in advance ofany aircraft able to take it. Such a situation is not an encouraging one since, for proper development, any engine—and particularlya supersonic engine—must have full Governmental support and be matched with specific aircraft designs. It has been unofficiallysuggested that the supersonic military aeroplane now being developed as a private venture by Hawker Aircraft is lookedupon as a future application of this engine. And of course it is possible to argue that there must always be a market for themost powerful supersonic turbojet in the world, particularly DE HAVILLAND ENGINES 1957 Turbojets and Rockets of Advanced Design This is the first photograph to be published of a Gyron Junior on test. The overhead suspension is employed in all the new test cells at Hat field, to which engines are brought from the Engine Company headquarters at Leavesden or the Engineering Division at Stag Lane. when, as in this case, it is in an advanced state of development. Gyron Junior. Virtually a two-fifths scale model of its bigbrother, the Gyron Junior has been developed under contract to the Ministry of Supply since September 1954. Owing to its closesimilarity to an existing engine, extensive component testing was unnecessary and the first prototype ran as early as August1955. Since that date, development of the Junior has been outstandingly successful. Its qualities appealed to aircraftdesigners immediately and the engine has progressively tended to overshadow its larger ancestor owing to its more immediateapplication to existing aircraft programmes. No figures for thrust may yet be published, but it can be statedthat more than one distinct type of Junior is under intensive development, and that trials with reheat and every other con-ceivable type of appurtenance (which will hereafter be discussed in general terms) have now reached an advanced stage. Thefirst 150-hr test was run last September, and one thousand hours of bench running was completed by December. The engine isshortly to fly in a Canberra, in which it will replace first one of the Avons, and later both. With this aircraft the Junior'sperformance will be explored up to very high altitudes and high subsonic speeds. Later the company may make use of a Javelinwhich is now being modified at the Napier Flight Development Establishment at Luton to take twin Gyron Juniors with reheat. It is appropriate at this point to interject a general dissertationon some of the problems which a manufacturer of a supersonic turbojet must face. To an ever-increasing extent such com-panies are being required to deliver a complete installation suit- able for a particular type of aircraft rather than a mere engine in acrate. The de Havilland Engine Company, having proven the basic design of die Gyron/Gyron Junior family, are now heavilycommitted to investigations into intakes, nozzles, reheat systems and other associated devices. An introduction to the installation problems of supersonicturbojets was published in our issue for May 11 last. The intake design is critical to the achievement of good engine performance,and it may well demand a variable centre-body, auxiliary intakes for subsonic flight and a spilling arrangement to match theswallowing capacity of the engine intake. Moreover, an auto- matic control system is necessary to match the engine mass-flowratio and Mach number under all conditions. Test techniques are particularly difficult and it is not normallypossible to do more than investigate the tunnel performance of comparatively small models. The de Havilland engine-research equipment is being strengthened by the addition of a supersonic tunnel two feet square for preliminary investigationsat Mach 3. Extensions are also being made to the Halford gas dynamics laboratory at Hatfield to enable actual Gyron Juniors to Fully described in our issue of September 23, 1955, the mighty instal- lation on the left is tailored to the require- ments of the Gyron in all its forms, some variants having thrusts in excess of the 1VA tons so far revealed. The Detuner silencer is bifurcated.
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