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Aviation History
1949
1949 - 0448.PDF
286 FLIGHT March loih, 1949 In relation to the large view, this detail was taken at the instant of full strut-closure and shows the order of tyre deflection. lor HAPPIER LANDINGS A Review of Work Now on Hand at Electro.Hydraulics, Ltd. The Her/pe* 'V note undercarriage fitted in the large vertical-guide drop-test machine. The pointer indicates that the rig is set up for a free drop of 30in. -r T NDERCAJRRIAGE manufacture on a large scale is I I busily engaging the attention of Electro-Hydraulics, ^ J Ltd., Warrington, where production of main and nose landing-gear assemblies for Vampires is in full swing.* The contract for Hastings undercarriages is almost com- plete, whilst main- and nose-strut assemblies for the Hermes IV are in production, as are the landing gears for the Short Sealand and Percival Prince. In addition to these production units, prototype undercarriages are also being built for the Firth helicopter as well as for other, still secret, aircraft. The company was one of the first to introduce under- carriages of integral construction, of which the Halifax cast- magnesium bridge was the first example. Whilst the same principle has been retained in the more recent develop- ments, high-strength aluminium-alloy forgings are now more usually employed in order that the highest possible strength-weight ratio may be obtained. The progress in weight-reduction as a result of these developments is tabu- lated hereunder: — WRIGHT OP MAIN UNDERCARRIAGE (Excluding Whaalt. Tyra» and Retraction Qnr) Aircraft rWHutHvtinfi Harmn IV ... Yaar I9W 1943 1944 All-up w.lght 65,0001b 75,000 Ib 85,0001b Und«- carrlaga waifht 511 Ib 4761b 4241b Parcantac* 0.790 0.635 0.499 A detailed description of the maekining and otktr production processes employedit contained m the March issue of out associated journal "Aircraft Production" ««<. mill be eotitimwJ in April. For the undercarriage future Electro-Hydraulics are seriously concerned with multi-wheel bogie designs and, in fact, such an undercarriage, equipped with 33m tyres, is now being flight-tested on a Lincoln at Farnborough. The company is prepared to state that, for an aircraft of 100,000 lb all-up weight, the bogie undercarriage complete with wheels and tyres, as offered up to the airframe, would weigh about 100 lb less per leg than would the conven- tional twin-wheel unit, and about 150 lb less per leg than a comparable single-wheel undercarriage. Reducing Landing Drag Aside from the very real advantage of weight-saving, the multi-wheel bogie permits a wide distribution of the requisite tyre-contact area, and rather more compact stow- age in the aircraft, except in the matter of length, which can usually be well afforded. A further advantage offered by the multi-wheel configuration is that, by arranging the rearmost pair of wheels (in a four-wheel bogie) always to touch first on landing, these wheels can be accelerated before the front wheels touch, and by so doing thus reduce the drag load. In the case of an aircraft with a landing weight of 75,000 lb it has been found that the spinning-up time for one pair of wheels at 1 g is 0.067 sec *or a ^ = 0.4, whilst it can be arranged that the second pair of wheels does not touch the ground until 0.083 sec after the first pair. Thus the maximum drag is approximately half that of the con- ventional undercarriage. Developments in this direction will be watched with considerable interest. With twin-wheel nose undercarriages, interesting prob- lems hinge on the " one-tyre punctured " case. It is fairly
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