This is an excerpt from EERE Network News, a weekly electronic newsletter.
Solar Airplane Equipped with Fuel Cell Crashes During Test Flight
Helios, a remotely piloted solar-powered aircraft, crashed on June 26th during a checkout flight. The prototype craft, which was essentially a flying wing, had been aloft for less than 30 minutes near the Hawaiian island of Kauai when it started to experience "control difficulties" at an altitude of about 3,000 feet. The control problem caused the wing to oscillate severely until some parts broke, causing it to fall out of control into the Pacific Ocean. Helios was operated under a program of the National Aeronautics and Space Administration (NASA), and NASA appointed a board to investigate the crash on June 27th. As of July 1st, three-quarters of the craft had been recovered.
Helios had been outfitted with two hydrogen storage tanks and a fuel cell to allow it to fly overnight at high altitude without landing or refueling, and a two-day trial was planned for mid-July. Previous flight tests in early June were terminated because of leaks in a coolant system and in lines feeding compressed air to the fuel cell. The hydrogen tanks were among the wreckage recovered from the crash. See NASA's Dryden Flight Research Center home page and press release page.
Helios was built and operated for NASA by AeroVironment, Inc. In 2001, it set a world altitude record for non-rocket-powered aircraft by flying 96,863 feet above the Pacific Ocean near Kauai. NASA intended to eventually equip the aircraft with a system to generate hydrogen from solar power, allowing the combination of fuel cell and solar power to keep the craft flying indefinitely. AeroVironment says that Helios' predecessor, the Pathfinder-Plus, may be used for some of the tests that were planned for Helios, and says that NASA and AeroVironment will continue the Helios program. AeroVironment will also press ahead with its plans to use a high-altitude solar aircraft as a telecommunications platform, acting essentially as a low-altitude satellite. See the AeroVironment press release.