Cause of Helios crash still unknown

Associated Press

Investigators have not pinpointed what caused the severe up-and-down fluctuations that brought down a record-setting unmanned plane during a test flight from Hawai'i in June, a NASA official said this week.

"There are still a few issues to be resolved," said Alan Brown, a spokesman for NASA's Dryden Flight Research Center in Edwards, Calif. "We are hopeful that preliminary findings of the investigation team may be forthcoming in a month or two."

With a wingspan of 247 feet, the solar-electric, propeller-driven aircraft looked more like a flying wing than a conventional plane. It crashed June 26 about a half hour after taking off from the Navy's Pacific Missile Range Facility on Kaua'i.

A preliminary report released two weeks after the crash said the plane was at 3,000 feet altitude when it fluctuated up and down before breaking up and crashing into the Pacific Ocean. The report by a five-member NASA investigation team said the fluctuations may have resulted from the complex interactions between the different systems aboard the aircraft.

The flight was aimed at testing an advanced experimental fuel cell system before the Helios was to be flown on a long-endurance mission of almost two days that had been planned for late July.

Helios was flying under the guidance of ground-based mission controllers for AeroVironment Inc. of Monrovia, Calif., the plane's builder and operator. It was one of several remotely piloted aircraft whose technological development NASA has sponsored.

The prototype, powered by solar cells during the day and by fuel cells at night, was designed to fly at altitudes of up to 100,000 feet. It was designed for atmospheric science and imaging missions as well as telecommunications relay work.

NASA continues to develop the technology that it had been testing with Helios, Brown said.

The space agency is aiming to have new high-altitude, long-endurance technology for remote-controlled aircraft ready for testing by 2007, Brown said, adding that the focus is on achieving extreme duration of 10 days to a few months.

It hasn't yet been determined whether the agency will rebuild Helios or develop another type of aircraft.

"They're still looking at a number of different options," Brown said. "We hope to have some idea within early next year on where we hope to go with this technology.

"A lot of it will depend on funding."