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Aviation History
1979
1979 - 2438.PDF
II -aMPf BRITAIN'S first solaiypowered airr craft, Solar One, has made its debut at Lasham Airfield, Hampshire, flying nearly three-quarters of a mile. Solar One was powered by electrical energy gathered by solar cells and stored in batteries. The flight, on June 13, was made by Ken Stewart who reported a take off speed of 18-20kt, a maximum speed of about 35kt and a maximum altitude of about 80ft. Stewart switched Solar One's electrical power unit on and off several times during the flight, before eventually gliding to the ground as he had used up all the available runway. Solar One made a second similar flight the same day, when pilot Bill Maidment reached a maximum speed of 42kt. The aircraft is the brain child of Freddie To, who formed Solar-Powered Aircraft Developments* to produce it. The design of Solar One has rested largely in the hands of consultant David Williams. The group claims to have achieved the first flight of a solar-powered aircraft with a short hop last December (Flight, May 26), but this is con tested by Larry Mauro of Ultralight Flying Machines in the US who flew a converted rigid hang glider in April. Solar One is an all-new aircraft and consists of a built-up wooden framework which is covered by a heat-shrunk thin plastic material called Solarfilm—the kind used to make model aeroplanes. The wing is in three parts for easy storage and transport—a centre section and two outer halves—and features a lami nated spruce girder box spar. The fuselage uses a similar internal arrangement as do the detachable all-moving fin and tailplane. The power unit is mounted on a stalk above the nose of the aircraft just in front of the pilot. The engine consists of four permanent magnet electrical motors, joined together by a chain drive to produce a nominal output of 4 h.p. The drive in corporates a 3:1 reduction to the fixed-pitch propeller which ends up being driven at about 1,100 r.p.m., but at present this gradually drops off as the batteries become exhausted. Solar One's "battery" consists of 24 Nickel/Cadmium accumulator cells joined in series and having a capacity of 25Ahr. When these are fully charged they provide enough power for the aircraft to climb for about eight minutes, though they supply useful energy for several more minutes. Solar powered aircraft develop ment's has invested about £16,000 in developing Solar One. This includes roughly £8,000 for materials, £6,000 of which was spent on the 750 solar cells fitted to the aircraft. The cells are thus the most expensive item on the aircraft, which partly accounts for why more have not been fitted to date. Solar One is designed to have almost all its top wing surface covered by cells—those fitted at present weigh less than 101b, including wiring—.it is claimed that this would give the craft a sustained rate of climb of 70ft/min in bright sunshine. Control of Solar One is fairly con ventional with power operated by an on/off switch. The team is currently looking at ways to improve Solar One's performance and plans to make a cross-country flight soon. One of the aims of the group is to develop their solar-powered aircraft for sport and recreational flying. *Solar-Powered Aircraft Developments, 5A Lyndhurst Gardens, London NW3. SOLAR ONE DATA Length 22ft; Span 68ft; Wing area 260ft2; Empty weight 2301b; Aerofoil section Wort- man FX180, 18 per cent thickness/chord; Power unit 4x Bosch 1 h.p. electric motors; Propeller wooden, 5ft 3in diameter; Solar cells 7S0x3in diameter and 0-008in thick; Batteries 24 Nickel/ Cadmium cells, capacity 25Ahr. Top Solar One takes-off on a flight of nearly three-quarters of a mile. Below left The 750 solar cells are attached to the inboard rear portion of the wings. The cells are covered by a transparent film to reduce drag. Below right The team responsible for Solar One, from left to right, Rill Maidment, Ken Stewart, Freddie To and David Williams
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