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Aviation History
1957
1957 - 0295.PDF
Two-fifths (linear) as big as the Gyron, the Gyron Junior (right) is at present the dominant partner, with applications closer in time. be run at conditions appropriate to supersonic speed at sea level.Even on model intakes the loads are considerable, and centre- body spikes made of ordinary steel have been found to succumbto temperature and erosion after less than one hour's running at Mach 1.9.Reheat systems—otherwise known as afterburners—have not been viewed with enthusiasm in this country when associated withsubsonic aeroplanes. They do, however, make a great deal of sense at high supersonic speed and are certain to be widelyemployed in future military aircraft. The de Havilland Engine (Company have an unsurpassed knowledge of the problemsinvolved (on October 29, 1954, we published abstracts from a paper on D.H. reheat by Mr. J. L. Edwards, now assistant chiefengineer). General reheat theory has now been fully established forengines of the Gyron type, and systems have been fully developed and are virtually ready for production. High-intensity systemshave been evolved with a hack Ghost engine and, with proper heat-shields and correct fuel injection, reheat temperatures canbe consistently held at 2,000 deg K. Reheat fuel is supplied by an air-turbine-driven pump, and it is worth remarking that thetotal fuel flow of a reheat Gyron (Senior) may reach the awesome level of 12,000 gallons per hour. The company have also put in seme three years' active develop-ment in the field of supersonic nozzles. A nozzle capable of complete expansion over a ratio of perhaps 20:1 would beimpossibly long and heavy, and one must accordingly choose a compromise intermediate value with a variable amount of con-vergence and divergence—and, if reheat is fitted, a variable throat as well. Area variation can be accomplished mechanically oraerodynamically and, provided the requisite efficiency can be achieved, one would expect the latter arrangement to be lighter.Ground testing of supersonic nozzles is again no easy task, although it is possible to reach expansion ratios up to about 7:1by using an engine as an ejector. Most modern turbojets were originally projected with theknowledge that the aircraft designer might require a substantial quantity of bleed air. Modern military aircraft frequently makeuse of blown flaps and de Havilland have removed all the thorns from this problem (although, of course, they cannot remove theattendant thrust penalty). The company have also achieved com- plete success with jet deflection, an arrangement first tried by theN.G.T.E. with a Meteor, as described in our issue of March 18, 1955. Equally encouraging results—in the writer's experience,unsurpassed results—have been achieved with reverse-thrust mechanisms. No less than 75 per cent reverse at full thrust hasbeen achieved with an installation mounted in a Venom; more- over, there is no time-limitation imposed on its use and no increasein turbine-exit temperature. Envelope size and weight of the device is quite acceptable and it can be cowled almost down tothe final nozzle. Ghost. Production batches of Ghost 105 turbojets are beingsupplied for the tail-end of Sea Venom production. It is possible to deduce that this engine is, in fact, fitted to the Sea VenomFAW.22 which is progressively replacing the Mk 21 with Fleet Air Arm squadrons. The new Ghost operates at increased temperatures by virtue ofits hollow turbine-nozzle guide vanes cooled by compressor- bleed air, a new design of fully floating box-type discharge nozzle,and turbine blades of Nimonic 95 with pinned root serrations. Piston Engines. One of the principal applications of the new The taking of this action shot of 25,000 Ib of reheat-Gyron thrust demanded no small amount of nerve on the part of the photographer. 200-series Gipsy Major is the Saro Skeeter helicopter. Experi-ence, particularly in the tropics, has shown that this aircraft could utilize increased power, and future production will accordinglybe fitted with the Gipsy Major 215 of 215 rated horse-power. Basically a standard direct-injection unit similar to its pre-decessors, the 215 is mechanically improved and operates at higher r.p.m. It is possible that similar increases in rating may also beachieved with the larger six-cylinder engines of the Gipsy family. Spectre. This name identifies what may well become themost important family of aircraft rocket motors in the world. The Ministry of Supply, for whom all work is being conducted,have announced five successive development ratings; but their enforcement of security is so rigorous that one may not evencomment on the design of the unit or state its propellants. It would, however, be reasonable to expect the latter to be high-test peroxide and kerosine, since these are operationally accept- able and are those with which the de Havilland Engine Companyhave a long record of experience. Various types of Spectre are being developed for use both asa.t.o. units and for permanent installation for primary propulsion. It may well be that the Spectre will be the powerplant of theforthcoming Saunders-Roe series of intercepters, the first of which is soon to fly.Full thrust with a development unit was first achieved in July 1954. Special-category flight clearance for initial flight opera-
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