A revolutionary helicopter prototype designed by Boeing Co. in Mesa completed two test flights in the past month following a crash in 2004 that set the development program back nearly two years.
Called the X-50A Dragonfly, the unmanned air vehicle uses canard rotor/wing technology that is designed to allow the craft to take off and land like a helicopter and fly like a fixedwing aircraft.
The two-bladed main rotor spins when the craft is in helicopter mode and stops in mid-flight to function like a wing when it is in traditional aircraft mode.
In the latest test flight Friday at the U.S. Army’s Yuma Proving Ground in southwest Arizona, the technology demonstrator reached an altitude of about 20 feet and hovered for four minutes, Boeing said.
That followed a preparatory "pop up" flight on Nov. 4 lasting about 30 seconds, during which the aircraft stabilized briefly at 16 feet before landing.
The latest test flight met all of its objectives, said Clark Mitchell, manager of the program.
"This is a significant achievement toward validating the new stopped-rotor technology," he said.
The $40 million development program is a joint project of the Boeing Phantom Works, the company’s technology development group, and the Defense Advanced Research Projects Agency, the technology development arm of the U.S. Department of Defense.
Last week’s successful flight was especially heartening for the program’s engineers following the crash of the first Dragonfly prototype during a test flight on March 23, 2004, at the Yuma Proving Ground.
A subsequent investigation by Boeing and Defense Advanced Research Projects Agency identified the design of cross coupling of the rotor controls as the cause of the accident, which caused no injuries because the aircraft was being controlled from the ground.
Improvements were incorporated into the second prototype as the result of wind tunnel tests at Boeing’s helicopter works in Philadelphia earlier this year.
Among the changes were increased control power, new flight control software and installation of a flight data recorder, all of which were successfully demonstrated in last week’s flight, Mitchell said.
"The most significant objective met was verification that software
compensation effectively reduces the rotor control issue we were having," he said. Eleven more test flights are scheduled through at least the first quarter of next year.
The Dragonfly will gradually perform more extensive hover flights, then forwardmoving rotary flights and finally convert from rotary to fixed-wing operation in-flight.
The 17-foot-long demonstrator is powered by a single turbofan jet engine. During rotary flight, the engine’s exhaust is diverted into the main rotor blades and exits through small nozzles in the rotor tips, causing the blades to spin rapidly.
After the machine is airborne, the exhaust is diverted through a nozzle at the back of the plane, propelling it forward. The conversion requires the main rotor to stop turning in flight and lock in place to become a fixed wing, allowing faster speeds.
An in-flight conversion won’t be attempted until the last one or two flights in the series, said Boeing spokesman Doug Kinneard. "The objective is to get to that point. Then the test program is over," he said.
The technology could eventually be used for aerial surveillance and other military missions.