Solar Impulse primed for take off this week

Around 70 engineers, technicians and test-pilots involved with Solar Impulse hope to get the craft airborne for a short period this or next week, with a longer two-hour test flight scheduled for early next year in Payerne.

The initial test from Dübendorf airfield near Zurich, is part of a series of checks launched earlier this month to prepare for a crucial 36-hour mission flight, currently scheduled for late spring or early summer 2010. The mission objective is to fly the solar-powered plane for two full days and a night non-stop. The aircraft has been designed to gather energy from the sun to operate throughout the night.

This series of checks will help technicians assess whether a pilot will be able to control the unusual plane. Lightness, a large wingspan and low flying speed are all considerations.

“Solar Impulse will fly at 50 kilometres per hour and everything happens at much lower speeds," André Borschberg, who along with adventurer Bertrand Piccard will eventually fly Solar Impulse, told Swisster. “In some ways it’s an aeroplane with four engines, but then in other ways it can be compared to a glider, although it flies much slower." he said.

During tests early this month, experts that include former test-pilots from NASA, Dassault and the German aerospace company DLR, assessed the propeller engines and vibration they prompted in other parts of the wings and fuselage. Around 100 sensors and gauges, placed on different points of the aeroplane, were used and resulting data transferred to computer by telematry. Flight control performance was also analysed.

Special landing gear, in particular a swivelling nose wheel which allows Solar Impulse to land at an angle in cross winds, was under scrutiny as well.

Borschberg explained that the aircraft's large wingspan prevented pilots from “decrabbing” the plane, the technical term to describe fuselage alignment during landing.

On November 20, a test pilot taxied the plane on the runway with a rolling airbag fitted under the plane to take the strain. “Luckily the gear worked perfectly well, so we then removed the airbag”, said Borschberg.

Although it weighs about the same as a family car, Solar Impulse possesses a 63-metre wing span (comparable to that of an Airbus A340), and the power of a scooter. Its propulsion is generated from some 11,600 ultrathin solar cells, used to provide the thrust needed to take off and maintain flight.

The team hopes that a 36-hour non-stop flight will pave the way for a continuous journey around the world.