Washington: NASA's 10-engine Unmanned Arial Vehicle (UAV), dubbed the Greased Lightning (GL-10), recently achieved a new feat in the skies over Hampton, Virginia.

The drone, which is under development by a team at the Langley Research Centre, had already passed its initial hovering tests last August.

But the real challenge was switching over from hover mode to conventional forward flight without the vehicle falling out of the sky. Recently, the battery-powered aircraft successfully did just that.

"During the flight tests, we successfully transitioned from hover to wing-borne flight like a conventional airplane then back to hover again. So far, we have done this on five flights," said aerospace engineer Bill Fredericks.

"We were ecstatic. Now we're working on our second goal -- to demonstrate that this concept is four times more aerodynamically efficient in cruise than a helicopter," he added.

The Langley team hopes to spin the technology off into a number of commercial applications including small package delivery or industrial/agricultural surveillance.

Also, a scaled up version, much larger than what NASA is testing now, would make a great 3-4 person size personal air vehicle, according to Fredericks.