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Aviation History
1944
1944 - 0233.PDF
FEBRUARY 3RD, 1944 FLIGHT nt, BACKBONE OF THE FLEET until recently the power available for take-off set a limita tion to high wing loadings. Now, with such powerful units available as the new 2,000 h.p. Napier Sabre and the potential of the jet propulsion engine—to mention only two—it is clear that the tactical possibility of having an entirely new type of fleet fighter is on the horizon. There are, however, other equally fascinating projects which probably underlie the American trend of authorita tive naval thought; which is to the effect that the aircraft carrier is now the *,'Backbone of the Fleet," the tactical unit to which o1?ners are subservient. This progressive view holds many adherents in the Royal Navy, which has passed its fledgling stage and is rapidly spreading powerful wings over the world's oceans. To paraphrase General Smuts words: " The tents have been struck, and the great might of the Navy is once more on the move.'' Jet Propulsioj One of the Original Scotland Rocket Respffrch Experimenters Sums Up the Qerfj^rc^t^rte^jif^Developrnent By J. AT less than the speed of sound a jet only propels the machine that carries it because of th^ reaction jj • produced, and this is still more or lesi sonic Speeds. Let us see then how a jet operates. Mr. Swimer's Article (Flight, December 23rd, 1943) gipesa^raccount of the jet of one type. This and the true JjjjjiWeject gases only which originate in the machine, and the gross weight of the machine falls by the total mass of the effective substance. This is ideal where there is no air, and might be use ful if speeds of the order of 2,000 feet per second gfre to be used. One thing must be made clear, the jet does not push against the air like a punt pole against the bottom! E < DENNL a force on the internal surface B C and on the external 'surface, and this will be partly balanced by the force on CD. The difference is the drag of the body. Now, ignoring the external effects, if we put a heater inside C it is theo retically possible to make the volume of the gas escaping at H so much greater'than the equal weight of colder gas entering at G that the force acting on the conical surface CD will be greater than the force acting on BC, and so the device will propel itself. In practice, if one places a jet of hot gas at C this will happen, althojj^n the power of the jet in itself is too small to measure. Now the design due to J.J. Smith for such an air craft (which we would have made between September, 1939, and May, 1940, if the war had not intervened) .'A — The ring-shaped body BCD will behave much as would the complete streamline body ABCDE and would require little power to drive it. Experiments carried out in Scotland with the assumption that speeds of over 1,000 feet per second were not yet practicable led to the use of a jet injection system in which no engine is used but the main force is produced by driving air drawn in from the atmosphere out again at an increased temperature and velocity. The latter statement is also true of the Caproni Cam- pini (see Flight, Februarv 19th, 1942), but the differences are considerable. If t>e aim of the engine is to pump, .r^faanically, air from one side of the narrow space C2—C3 to the other (see diagram) then the difference is really greater than the resemblance, for in that case one has only a differently-shaped, differently-placed article doing just what the airscrew does, i.e., taking rotary power and using it to drive the aircraft. The diagram shows a ring-shaped streamline body BCD which will behave in much the same way as the complete circular solid body ABCDE would have done before the streamline tube was put inside it. The air passing through will be compressed and will would have used a 500 h.p. engine which uses ail its power in compressing air. This air would have been fed into a ring of two-stage injectors situated at C and fed with fuel oil. The engine would have consumed about three quarters of an ounce of fuel oil per second, and the injectors about a quarter of a/pound in the same time. The propulsion power should have been about 4,000 h.p. (abt. 1 ton). Using a Williams internal combustion turbine engine as compressor, that would have scaled about 4 cwt., and the jet system about 1 cwt. The whole power unit should be easy to make under half a ton, even if the more flexible reciprocating engine were used. (The advantages of the turbine is a separate subject, best ignored here, but our preference for industrial fuel oil that takes fire less readily than petrol is obvious.) We should have used a tail-first layout and, indeed the same parts as, experiment 43 at most points. The greater controllability of tail-first, jet-propelled air craft is a thing that is easy to understand and is borne out when both are flown under similar conditions. WHAT ARE THEY* PLANNING ? Before the war the Airspeed company specialised on civil aircraft. It seems logical to assume that when things become normal that work will be resumed. Here is Mr. A. E. Hagg with his technical staff. From left to right: Mr. Riches; Mr. Chapleo (chief structures engineer); Mr. Jewett (chief development engineer); Mr. Ellison (chief project engineer); Mr. Foss (chief «erodynamicist); Mr. Clarke (chief engineer); Mr. Hagg (technical director); Mr. Jupp (experimental superin tendent) ; Mr. Johnston (chief draughtsman); and Mr Errington (chief test pilot).
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