Paul MacCready’s career of bold experimentation recaptured the exhilaration of aviation’s golden age. Disregarding conventional notions of practicality, he invented the first human-powered flying machine, realising a dream dating back to Leonardo da Vinci and probably beyond. His pedal-powered craft then crossed the English Channel – and he went on to create the first solar-powered aircraft.

MacCready’s quirky intelligence was directed by a desire to “do more with less”. An early advocate of environmental sustainability, he was also behind the first production electric car, General Motors’ EV1.

A bad debt was the spur for his first record. Needing to find $100,000 in a hurry, he remembered that a British industrialist, Henry Kremer, was offering almost exactly that amount to the creator of a machine capable of flying through human muscle power alone. “Suddenly, human-powered flight seemed important.”

MacCready, a former gliding champion, took his inspiration from the graceful soaring flights of birds of prey. His key insight was realising that if he could triple the wingspan of a glider without increasing its weight, it could be kept aloft by one quarter of one horsepower, which a trim athlete was well capable of providing.

The Gossamer Condor was built from piano wire, aluminium tubes and bicycle parts and covered in translucent plastic film. The spindly craft had a vast 90ft (27m) wingspan but weighed only 70lb (32kg). On August 23, 1977, piloted by Bryan Allen, a bicycle racer, it succesfully completed a seven-mile figure-of-eight course in California. The feat earned MacCready the prize money and the media soubriquet “the father of human-powered flight.”

Kremer soon upped the stakes, offering £100,000 for the first human-powered flight across the Channel. Only two years later, MacCready felt confident enough to make an attempt on the prize with an improved version of the Condor, the Gossamer Albatross, built with a lighter, carbon-fibre frame.

With Allen again the engine, the craft took off from Folkestone on June 12, 1979, gaining maximum lift by gliding, like seabirds do, just above the waves. It touched down 22 miles away at Cap Gris-Nez two hours and 50 minutes later – an average speed of under eight miles an hour.

Only months later Janice Brown, a primary school teacher, recorded the first flight powered only by the sun when she took the Gossamer Penguin airborne above the Arizona desert. MacCready refined the design to produce the Solar Challenger, powered by 16,128 photovoltaic cells feeding a three horsepower engine. In 1981 this flew the 163 miles from Paris to Canterbury at 11,000ft.

His research in the field continued, and in 2001 Helios, his 247ft-wingspan unmanned solar aircraft reached 97,000ft (18 miles), a world record for a non-rocket-powered plane.

MacCready readily admitted that “as a commercial proposition, solar flight is wildly impractical”, but this was never the point. He liked to cite the inspiration of Charles Lindbergh, whose flight across the Atlantic did not directly advance aircraft design. “But it changed the world by being a catalyst for thinking about aviation.” (MacCready’s Condor now hangs alongside Lindbergh’s Spirit of St Louis at the Smithsonian Institution.)

His solar-powered experiments were also, though, fuelled by a desire to focus attention on the need for a less energy-intensive future for transport. As early as 1981 he spoke of the need to wake the US public up to solar power: “I really believe half the populace would be willing to send my sons to the Middle East to fight a war to protect the supply of oil required to keep their cars going. I keep asking what I can do to improve our approach to energy.”

MacCready was convinced that electric-powered cars were the future. In 1987 his solar-powered racing car, the GM Sunraycer, won a 1,800-mile race between Darwin and Adelaide, averaging 41mph. His Impact concept car, doing 0-60 in 8 seconds, was the basis for the production electric car, GM’s EV1, launched in 1996. The car was, however, ahead of its time; though it won a loyal following, the model was shelved by GM in 2000 after losing $1 billion.

Paul Beattie MacCready was born in New Haven in 1925, the son of a doctor. He built model planes from a young age. “Looking back, I realise it was a good substitute for always being the smallest kid in the class,” he said in 1989. He soon graduated to the real thing, qualifying as a pilot aged 16.

He started at Yale in 1943, also doing flying training with the US Navy during the war, and graduated with a degree in physics in 1947. He took up gliding, winning three national championships, and earned a doctorate in aeronautics from the California Institute of Technology in 1952. Four years later he became the first American to win the world championship.

MacCready’s approach to problems was resolutely untraditional. “Any big idea I’ve ever had has always come to me in daydreaming,” he would say. He liked to plunge into challenges, unafraid to get things wrong; the Condor was developed by learning from numerous crashes in testing (he conceded this was “not the way to develop airliners”.) Among his other projects was a radio-controlled, flying replica of a pterodactyl and – a rare failure – a small plane powered by a hamster. “Hamsters are lazy,” he explained, “A rat may do the trick.”

Despite his image as a childlike dreamer, however, MacCready was a shrewd businessman. The Albatross and the Penguin were both sponsored by DuPont, as a showcase for their lightweight materials, just as his electric cars were bankrolled by GM.

In 1951 he had founded his first company, Meteorology Research Inc, doing early work on cloud seeding, and after selling the business he founded AeroVironment in 1971. He remained in charge of the company, which develops environmental technologies and remote-controlled surveillance planes, until just before his death. He won dozens of innovation and engineering awards and was inducted into the Aviation Hall of Fame in 1991.

He is survived by his wife, Judy, and three sons.

Paul MacCready, aeronautical engineer and inventor, was born on September 29, 1925. He died on August 28, 2007, aged 81