A human-powered aircraft (HPA) is an aircraft powered by direct human energy and the force of gravity; the thrust provided by the human may be the only source; however, a hang glider that is partially powered by pilot power is a human-powered aircraft where the flight path can be enhanced more than if the hang glider had not been assisted by human power. Likewise, HPA inevitably experience assist from thermals or rising air currents. Pure HPA do not use hybrid flows of energy (solar energy, wound rubber band, fuel cell, etc.) for thrust. In nil wind, a flatland-long-gliding aircraft is a form of HPA where the thrust in the nil wind is provided by the running of the pilot; when the pilot loses touch with the ground, his or her thrusting ceases to add energy to the flight system and a glide begins; the pilot may or may not add energy after the pilot stops touching the ground. Humans who tow up a manned kite form one type of human-powered aircraft.
Early attempts at human-powered flight were unsuccessful because of the difficulty of achieving the high power-to-weight ratio. Prototypes often used ornithopter principles which were not only too heavy to meet this requirement but aerodynamically unsatisfactory.
Under the auspices of the Society, in 1959 the industrialist Henry Kremer offered the Kremer Prizes of £50,000 for the first human-powered aeroplane to fly a figure-of-eight course round two markers half-a-mile apart.
A team of Enea Bossi (designer), Vittorio Bonomi (builder), and Emilio Casco (pilot) met a challenge by the Italian Government for a flight of one kilometre using their Pedaliante in March 1937. The aircraft apparently flew short distances fully under human power, but the distances were not significant enough to win the competition's prize. Furthermore there has been much dispute as to whether it ever took off under the pedal-power of the pilot alone, in particular because there is no record of official observation of it having done so. Some of the arguments for and against the validity of Bossi's claim to have done so are presented by Sherwin (1976). At the time the fully human-powered flights were deemed to be a result of the pilot's significant strength and endurance; and ultimately not attainable by a typical human. As with the HV-1 Mufli, additional attempts were therefore made using a catapult system. By being catapulted to a height of 9 metres (30 ft), the aircraft met the distance requirement of 1 kilometre (0.62 mi) but was declined the prize due to the launch method.
The first officially authenticated take-off and landing of a man powered aircraft (one capable of powered take-offs, unlike a glider) was made on 9 November, 1961 by Derek Piggott in Southampton University's Man Powered Aircraft (SUMPA). The best flight was 650 metres.
Puffin 2 flew on 27 August, 1965 and made several flights over a half-mile, including a climb to 5.2 metres. In 1967 Kremer increased his prize money tenfold to £500,000, for no-one had even attempted his challenging course. He also opened the competition to all nationalities as it had previously been restricted to British entries only. After this date several less successful aircraft flew, until 1972 when the Jupiter flew 1,070 metres and 1,239 metres in June 1972.
On 23 August, 1977 the Gossamer Condor 2 flew the first figure-of-eight, a distance of 2,172 metres winning the first Kremer prize. It was built by Dr Paul B. MacCready. and piloted by amateur cyclist and hang-glider pilot Bryan Allen.
A Kremer prize of £20,000 for speed went on 1 May, 1984 to a design team of the Massachusetts Institute of Technology for flying their MIT Monarch B craft on a triangular 1.5 km course in under three minutes (for an average speed of 32 km/h): pilot Frank Scarabino. Further prizes of £5,000 are awarded to each subsequent entrant improving the speed by at least five percent.
The current distance record recognised by the FAI was achieved on 23 April, 1988 from Iraklion on Crete to Santorini in a MIT Daedalus 88 piloted by Kanellos Kanellopoulos: a straight distance of 115.11 km (74 miles).
With further funds from the late Henry Kremer, the Royal Aeronautical Society has announced four new prizes:
The eventual aim is to achieve Olympic recognition as a sport.