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Aviation History
1952
1952 - 1521.PDF
De Havilland Tiger Moth, with Dowty shock-absorber legs. Double retractable tailwheels on the Short Stirling. Ryan S.C. monoplane, with experimental levered-suspension undercarriage (Above) Internally sprung wheels on Westland Lysander. (Below) the Dowty-equipped Avro Canada Jetliner. (Right) Avro Lancaster with „ t |^ Dowty retractable undercarriage and hydraulic system. Bristol "Britain First," with early Dowty retractable undercarriage jet-propelled Gloster/Whittle E.28/39 of 1941. The low ground-clearance permitted by the absence of an airscrew allowed full advantage to be taken of the inherent compact ness of the system, and results were altogether successful—so much so, in fact, that a generally similar undercarriage was chosen for the Meteor. The Meteor embodied another Dowty innovation in that the main legs were compressed on retraction in order to lessen the space needed for stowage. An occasion of note during 1943 was an exhibition at the headquarters of the Ministry of Aircraft Production, wherein the track undercarriage and liquid-sprung shock-absorber were first shown publicly. Flight's representative was much taken by the Liquid Spring system and wrote of it, "It is so much a departure from commonly held postulates that we could scarcely believe the device workable, flatly refuting, as it does, the generally accepted principle that oil is, for all practical purposes, incompressible." The unit consisted of a cylinder in which slid a piston rod carrying a head, itself containing a damping valve and orifice. With the rod fully extended the cylinder was completely filled with oil, to the exclusion of all air; so, when the rod was driven into the cylinder the reducton of volume caused by the presence of the rod induced compression of the fluid. Very little maintenance was necessary. For topping-up there were two filler plugs whereby oil could be introduced without air. Eloquent of the system's robustness were the results achieved on a Halifax, which survived two crash-landings and was then subjected to 500 landings without receiving attention of any kind. The Liquid Spring, of course, has grown vastly in popu larity since 1943, and is now installed on many of the most advanced types of civil and military aircraft. With the ending of the war Dowty technical development went from strength to strength; thus, Mr. A. W. Martyn, the chairman, addressing the annual general meeting at Chelten ham in 1946 was able to announce : "At no time in our history have we had so large a volume of prototype and development work. We are working concurrently on such designs as the Bristol Brabazon, Bristol Wayfarer, Avro Tudor, Airspeed Ambassador, and numerous other civil and military types." The Brabazon undercarriage itself was a major achievement. On the Mk 1 machine the principal units are two main Dowty assemblies, with liquid-sprung shock-absorber units and two twin-tyre Dunlop wheels; a Dowty nosewheel assembly, also liquid-sprung, with twin steerable Dunlop wheels; and a non-retractable tail bumper, again with liquid springing. On the Mk 2 there will be two main undercarriage groups of four-wheel bogies, each with Dunlop twin-tyred wheels, and this gear is now to be seen on the massive 100-ton drop-test rig at Arle Court. Dowty's know-how, acquired during years of work on
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