The Solar Impulse HB-SIA prototype, a uniquely solar-powered aircraft, has entered a new test phase, which should see the aircraft taking its first night flights this summer. The carbon fiber aircraft has been built with the intent to ultimately fly around the world, day and night, without fuel other than energy acquired from the sun. The new test phase follows on a successful first takeoff, last December, and will include short circuits and a first flight at altitude. Piloting the aircraft is described by the company as "an extremely difficult high-risk exercise." Two pilots, Bertrand Piccard and Andre Borschberg, will take turns in the test series to familiarize themselves with the plane, leading to the first night flights. According to the company, "never before has such a large and lightweight aircraft left the ground." NASA's Helios was larger and lighter, but did not carry a human being; it broke up in flight and crashed in the Pacific Ocean in June, 2003.
This is a companion discussion topic for the original entry at https://www.avweb.com/news/solar-impulse-steps-toward-first-night-flight