Boeing won a $9.36 million contract modification from the U.S. Defense Advanced Research Projects Agency (Darpa) to refine its concept for a radically improved vertical takeoff and landing (VTOL) aircraft to the preliminary design review stage. Three other contractors have proposed concepts for the program.
Boeing’s Phantom Swift concept combines two lift fans in the main body of the aircraft for vertical lift with two wingtip thrusters for forward propulsion. “The vehicle that we’re designing today is a 12,000-pound, about 44-foot nose-to-tail, 50-foot wingtip-to-wingtip unmanned aircraft,” Brian Ritter, the company’s program manager, told reporters in June.
The demonstrator would be powered by twin General Electric CT7-8 turboshaft engines, with the aim of moving to electric propulsion in the future. An engineer with Boeing Commercial Airplanes in Seattle proposed the design as part of an internal innovation challenge. The company’s helicopter unit in Ridley Park, Pa., refined the concept and demonstrated it with a flying “broomstick model,” Ritter said.
In the last year, Darpa awarded Phase 1A conceptual design contracts to Boeing, Aurora Flight Sciences, Karem Aircraft and Sikorsky Aircraft, all of which proposed unmanned aircraft. The contract option Darpa exercised with Boeing this month is for a 16-month Phase 1B technology maturation effort to be completed by November 30 next year. In the program’s second phase, Darpa plans to select two proposals to advance to detailed design, fabrication and assembly. Flight-testing will take place in the third phase, scheduled for 2017-2018.
Darpa released a broad agency announcement in February last year seeking proposals for a VTOL experimental aircraft “with exceptional performance in vertical and cruise flight…The program will demonstrate an aircraft capable of sustained flight at high speeds, improved hover and cruise efficiencies that are significantly greater than contemporary rotary-wing aircraft, and increased useful load fractions and aircraft functionality.”
Specifically, Darpa called for a VTOL X-plane designed to fly at sustained speeds of 300 to 400 knots; demonstrating hover efficiency within 25 percent of the ideal power loading at sea level; with double the lift-to-drag ratio of a typical helicopter; and the ability to carry a useful load of at least 40 percent of the vehicle’s max gross weight of 10,000 to 12,000 pounds.