American aerodynamicist who headed a team that designed and built both the first man-powered aircraft (airplane) and the first solar-powered (solar cell) aircraft capable of sustained flights.

MacCready was a national champion model-plane builder in the 1930s and received his pilot's license at the age of 16. He graduated with a B.S. degree in physics from Yale University in 1947 and earned an M.S. degree in physics (1948) and a Ph.D. in aeronautics (1952) from the California Institute of Technology.

MacCready started sailplaning in 1947 and was U.S. soaring champion in 1948, 1949, and 1953 and international champion in 1956. He was head of his own firm, AeroVironment, in Pasadena, Calif., working on the improvement of air quality, the conservation of energy, and the derivation of power from wind and water.

On Aug. 23, 1977, at Shafter Airport near Bakersfield, Calif., MacCready's Gossamer Condor, pedaled and piloted by 137-pound (62-kilogram) Bryan Allen, a bicyclist and hang-glider enthusiast, completed the course required to win the Kremer Prize of £50,000 ($95,000), clearing a 10-foot- (3-metre-) high start-and-finish line while making a figure-eight flight around two pylons set half a mile apart. The total distance flown was 1.15 miles (1.85 km) in 6 min 27.05 s, at a top speed of 11 miles per hour (18 km/h). The 70-pound (32-kilogram) plane had a 96-foot (29-metre) wingspan.

A subsequent, more streamlined MacCready plane, the Gossamer Albatross, was pedaled and piloted by Allen from near Folkestone, Kent, Eng., to Cape Gris-Nez, Fr., a distance of 23 miles (37 km), in 2 h 49 min, on June 12, 1979. This flight won the £100,000 Kremer Prize for the first man-propelled flight across the English Channel. The plane had a wingspan of 93 feet 10 inches (28.6 m), weighed 70 pounds, and was constructed of Mylar, polystyrene, and carbon-fibre rods.

On July 7, 1981, the Solar Challenger, a solar-powered plane designed by MacCready, flew from the Pointoise Cormeilles airport, near Paris, to the Manston Royal Air Force Base, in Kent, Eng., a distance of 160 miles (258 km), in 5 hr 23 min at an average speed of about 30 miles per hour (48 km/h) and a cruising altitude of 11,000 feet (3,350 m). The pilot was Stephen Ptacek, weighing 122 pounds (55 kg). The plane, powered by 16,128 solar cells connected to two electric motors, weighed 210 pounds (95 kg) and had a wingspan of 47 feet (14.3 m).

MacCready's later inventions include Sunraycer, a solar-powered car that in 1987 won a 1,867-mile (3,006-km) race in Australia. He was president of the International Human Powered Vehicle Association, which is dedicated to maximizing the speed of the bicycle. In 1991 MacCready was inducted into the National Aviation Hall of Fame.