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Aviation History
1963
1963 - 2332.PDF
I'LIGHT International supplement, 26 December 1963 The Light Hovercraft Air-Cushion Vehicles IMost of Mr Britten's paper concerns the light hovercraft designed by his own company. In this fine view—taken from a helicopter over the harbour at Bembridge, Isle of Wight—a CC-2 Cushioncraft is seen with main engine running and auxiliary air propellers stopped ON NOVEMBER 20, as reported on page , an ACV symposium was held in Stockholm under the sponsorship of the Swedish Society of Aeronautics and the Swedish Institution of Mechanical Engineers. What follows is based upon a paper read at this meeting by Messrs F. R. J. Britten and N. D. Norman, who founded the company bearing their name. The position in the ACV field of a light hovercraft must broadly resemble that of the light aircraft in relation to the commercial passenger-carrying aircraft. This means that it will be judged not upon cost per passenger seat-mile but upon first cost in relation to the job Performed. For example, a four-seater hovercraft costing $70,000 would com pare unfavourably with a four-seat helicopter costing a similar amount, because it offers a lower performance over a more limited range of conditions. On the other hand a four-seat hover craft costing $12,500 would compare favourably with a high-speed cabin launch costing a similar sum, because it would offer a better performance over a wider range of conditions. A four-seat helicopter does in fact cost about $70,000, and it can do all that a four-seat ACV can do and a ireat deal more besides. On the other tand, a 30kt cabin launch with two J10 h.p. engines costs some $12,500. It shall© is incapable of traversing safely w waters, sandbanks, ice, beaches, rapids, etc, and is perhaps 20kt slower than the small ACV under normally calm conditions. The function of our light ACV lies somewhere between those of light helicopters and light utility launches. But it must not go too far up the scale away from the launch and towards the helicopter because to do so would render the latter the pre ferred vehicle. If a four-seat aeroplane mounted on amphibious floats can perform the duties required of our light hovercraft it will be preferred on the grounds of speed since its cost would fall well below that of the helicopter. Fortunately for the light hovercraft, amphibious aircraft suffer from many of the limita tions of high-speed launches on water and require long strips of smooth, firm ground ashore. In common with the helicopter they demand highly qualified personnel for their operation and maintenance. Britten-Norman's ACV development programme started in August 1959 with the design of the CC-1, the major aim of which was to develop an efficient lift system. By using an axial-flow fan with a very large hub : diameter ratio, and discharging the flow into a very short nozzle, aerodynamic losses were kept to a minimum. The CC-1 com pleted some 20hr testing at Bembridge Airport over a period of fifteen months. The craft was subsequently delivered to the Hovercraft Trials Unit at Lee-on- by John Britten Solent, where it has also done a limited amount of testing. It is now being fitted with two Volkswagen propulsion en gines and an experimental skirt. The CC-1 programme provided much useful qualitive information about the behaviour of air-cushion vehicles. The peripheral fan was extremely efficient and gave a good hoverheight. The machine was, however, deficient in for ward thrust and had problems associ ated with the gyroscopic forces set up by the large fan. It was also thought that the fan was in too exposed a position for a commercial vehicle, CC2I-001 Design of the CC-2 began in July 1960; CC-2/001 first hovered on August 31, 1961. It obtained a hoverheight of 12in and a forward speed of about 25kt. The prototype CC-2 was pur chased by the Ministry of Aviation whilst still under construction, and it was on test at Bembridge for only some four months. Since taking delivery the MoA have accumulated some 50hr experimental running and the machine has been fully instrumented. As part of the Ministry's programme a one-sixth wind-tunnel model was built and exten sively tested with two designs of fan. This model was also tested with auxili ary external motors. In addition, a one- third scale half-model was built in which various fans were tested together with different intakes and plenum arrangements. For the next series of tests CC-2/001 is being modified at Bembridge in the following main respects:— (1) A new design of fan giving in creased efficiency is to be fitted. (2) Re-designed sidebodies are being built, carrying a 100 b.h.p. Conti nental engine on either side of the cabin. (3) Additional roll and yaw controls are being provided in the outer jets. (4) The fins are to be provided with movable rudders. These modifications are expected to be completed early in 1964. After a further period of tests the machine will also be equipped with a flexible skirt. CC-21002 Following the sale of CC-2/001 to the MoA, work was immediately put in hand on a second prototype. As a result of further model work, and experience with the CC-2/001, it was decided that the second machine should be fitted with a conventional design of centrifugal 7ft- 81
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