The HB-SIA solar-powered aircraft, the first prototype of the Solar Impulse project, is to be unveiled next week on June 26 at Dübendorf air base, near Zurich, Switzerland. Those who attend will discover some design changes since the last images were released, company CEO André Borschberg told AIN, adding that a first flight is planned for later this year.
In February, Solar Impulse engineers were elated when the main spar successfully completed load tests, which simulated situations such as a combination of turbulence and extreme piloting maneuvers. The trials involved flexion and torsion of the aircraft’s 200-foot-long spar. The spar was fixed at its center and lead weights were gradually added onto approximately 30 platforms suspended by cables or winches distributed along its span. They were loaded in four stages–25, 50, 75 and 100 percent–yielding a total load equivalent to 3.5gs. With the total load–comprising 5.5 metric tons of lead–the deflection measured at the wing tips was almost four feet.
