The first flight across the English Channel by a sun-powered airplane ended successfully when Stpehen Ptacek piloted the stubby but graceful Solar Challenger into Manston airfield in Kent July 7.
The event is unlikely to strike terror into the hearts to airplane manufacturers who rely on jet or piston engines to propel their products.
But Solar Challenger's 5-hour, 180-mile journey from the outskirts of Paris to the eastern edge of Britain was hailed by the plane's designer, Paul MacCready, as a dramatic demonstration of the importance of solar energy as one of man's chief natural resources.
Dr. MacCready and his team of eight had been required to wait a month to prove their point. Consistently gloomy weather over that period denied the Solar Challenger's 16,000 solar cells the vital sunshine needed to hoist the tiny craft skyward and allow the diminutive Ptacek, selected for his lightness as well as his skill, to steer it for respectable distances through the air.
The sun at last come out July 7 and MacCready and his associate hastened to fit the bits and pieces of their brainchild together. Ptacek, the Challenger, and the sun did the rest.
The plane, its 47-foot wingspan exposing the solar cells to the sunshine, began to soar. When it reached 11,000 feet, the pilot leveled off and headed for Britain.
Ptacek said afterwards that the Challenger, pursued by chase planes, one of them containing MacCready, performed perfectly. It took exactly one hour to cross the stretch of water separating France from Britain.
The flight would have been shorter if ground staff a Manston airfield had been ready for Solar Challenger's arrival. Ptacek had to circle the airport for half an hour while customs and immigration officials prepared themselves to receive the American pilot.
Dr. MacCready, who four years ago won a L50,000 ($100,000) prize for the first sustained and controlled airplane flight using human power, said Solar Challenger's journey was of great significance.
The aim of the venture, he said, was to focus attention on solar energy as an alternative to oil. "Our thinking over the past 70 years has been conditioned by the ready availability of lots of cheap energy and we are going to have to get by on less."
The main significance of the principle employed in Solar Challenger is long-term. It is thought that airliners in the future could use energy from the sun as motive power while cruising at high altitudes.
The Challenger's array of solar cells produces about 1.1 kilowatts per square yard of wing and tailplane area. A two-blade propeller can be turned on and off by the pilot.
So far the project has cost L340,000 ($680,000) of which fitting the solar cells accounted for L20,000 ($40 ,000) The cells are on loan from NASA.