Video: High-Speed Plunge Transforms Robo-Copter into a Plane

Video: High-Speed Plunge Transforms Robo-Copter into a Plane:
The U.S. Navy has doubled down on an effort to build a hybrid flying robot that takes off like a helicopter and cruises like an airplane. The Flexrotor, under development by the Office of Naval Research and the Aerovel Corporation in Washington State, represents at least the fourth attempt to duplicate the skills of the crash-prone V-22 Osprey tiltrotor, but without the Osprey’s design flaws.
On April 30, the Navy awarded Aerovel a second development contract to improve the Flexrotor’s engine and remote controls. The ultimate goal is to develop a version of the ‘bot equipped with sensors and capable of operating from small ships. “With Flexrotor, the two biggest benefits to sailors and Marines would be the ability to do extended maritime surveillance from a ship, and to do so with a small footprint,” said ONR’s John Kinzer.
As depicted in the video above, the Flexrotor takes off vertically like a helicopter, propelled by its roughly five-foot, tip-mounted rotor. Once it climbs high enough, small winglets pop out of the robot’s tail end and it tips over and dives, transferring lift from its rotors to its 10-foot-wide wing mounted in the middle of the tube-shaped body. The rotor becomes a propeller, and Flexrotor cruises along like any conventional airplane. The first drone’s first test transition between copter and plane modes took place in August.

What the Flexrotor achieves with its daring transition maneuver, the Bell-Boeing V-22 accomplishes with rotating, wingtip engine nacelles. Pointing the engines up allows the 57-foot-long Osprey to take off, land and hover like a helicopter. Pointing them forward transforms the V-22 into an airplane for high-speed cruising.
But design compromises such as short rotor blades (to allow the Osprey to fit aboard ships) and delicate, high-horsepower engines (to compensate for the short blades), plus the unique aerodynamics of the tiltrotor concept, have plagued the $65-million craft. Thirty-seven people have died in a series of high-profile Osprey mishaps. Despite the dangers, 200 or so V-22s are slated for production on top of the nearly 200 already in service.
The military and industry have made other attempts to match the V-22′s vertical-flying abilities and high speed, but without the Osprey’s liabilities. The Piasecki Speedhawk and Sikorsky X2 are experimental helicopters with rear-mounted pusher rotors to boost their top speeds. The Pentagon is looking at a tiltrotor with wider rotor blades and safer engines as a possible replacement for today’s helicopters. The Flexrotor’s dive-and-transition concept could work for robots, but is unsuitable for a manned aircraft.
Plus, the Flexrotor is not without its own risks, as ONR pointed out. “The propeller needs to be big enough to provide sufficient lift to take off vertically, yet small enough to be efficient while in horizontal flight,” the agency reported. “The flight controls must provide powerful and precise control in vertical takeoffs and landings and efficient, low-drag control in forward flight. Perfecting both the rotor and other flight capabilities requires a constant balancing act among power, efficiency and weight.”