MANASSAS, Virginia, April 12, 2017 (ENS) - In the near future, vertical takeoff and landing (VTOL) aircraft will be able to take off and land almost anywhere and fly much faster and farther than any existing hover-capable craft, according to the U.S. military, authorized personnel reveal.
The U.S. Defense Advanced Research Projects Agency (DARPA) successfully completed flight-testing of a sub-scale version of a novel aircraft design in March as part of its VTOL X-Plane program.
DARPA is proceeding now to develop a full-scale version of the novel plane, nicknamed Lightning Strike, and recently designated the XV-24A by DARPA and the U.S. Air Force.
Developed and fabricated by Aurora Flight Sciences in Manassas, with partners Rolls-Royce and Honeywell, the XV-24A is a tilt-wing unmanned aerial vehicle powered by an Electric Distributed Propulsion system.
Twenty four variable-pitch ducted fans driven by electric motors provide thrust for both hover and cruise. A single Rolls-Royce AE 1107C turboshaft engine drives three Honeywell generators which provide power to the wing and canard electric motors.
Eighteen of the fans are distributed within the main wings and six in the canard surfaces, with the wings and canards tilting upwards for vertical flight and rotating to a horizontal position for wing-borne flight.
“Aurora is proud to support DARPA on what we all hope to be a truly historic breakthrough in aviation technology,” said Dr. John Langford, chairman and CEO of Aurora. “If successful, VTOL X-Plane’s radically improved flight capabilities could lead to revolutionary advancement of the U.S. military’s future mission capabilities.”
Subscale testing began on the VTOL program in March 2016 and the first phase of testing ended after six flights with demonstration of auto take off; sustained hover; directional and translational control, including lateral and rearward flight, waypoint navigation, and auto landing.
Later, the aircraft wing and canard tilt mechanisms, tilt schedules, and wing-borne flight controls were enabled for testing.
Four of the test flights featured an expanded flight envelope in which the vehicle experimented with increases in air speed until the wing generated most of the lift.
“The VTOL demonstrator was designed to test the aerodynamic design of the aircraft, validate flight dynamics, and develop the flight and mission-systems controls for application to the full-scale vehicle,” said Ashish Bagai, DARPA program manager.
“The aircraft exhibited exceptional flight characteristics, with no loss in altitude even as it transitioned from vertical to horizontal flight. It also demonstrated aerodynamic effectiveness of the distributed propulsive system," Bagai said.
The sub-scale aircraft weighs 325 pounds and is a 20 percent flight model of the full scale demonstrator Aurora will build for DARPA over the next two years.
The subscale aircraft flight and mission control architectures will be carried over into the full-scale VTOL aircraft, with some additions and improvements.
The full-scale XV-24A will weigh 12,000 pounds compared to the demonstrator’s 322 pounds, and will aim to demonstrate performance objectives stipulated by DARPA: flight speeds in excess of 300 knots, full hover and vertical flight capabilities, a 25 percent improvement in hovering efficiency over helicopters and 50 percent reduction in system drag losses during cruise.
According to Bagai, the full-scale aircraft will incorporate a triple-redundant flight control system instead of a single system.
The aircraft’s electric distributed propulsion system would consist of highly integrated, distributed ducted fans that, combined with the synchronous electric drive system, would enable the design’s potentially revolutionary hover efficiency and high-speed forward flight.
The Rolls-Royce AE 1107C hybrid turboshaft engine driving electric generators to power the fan units, rather than the demonstrator’s batteries, will power the full-scale aircraft.
“The Aurora team’s goal is to help redefine the future of vertical flight,” said Mark Wilson, chief operating officer of Rolls-Royce LibertyWorks, an advanced aerospace technology research and design unit.
“Rolls-Royce LibertyWorks is proud to contribute both proven components and innovative new technologies in turbo-electric distributed propulsion to this exciting program," said Wilson.
The full-scale aircraft fan units will be synchronized to the generators and turn at a constant RPM, but incorporate variable pitch, while the demonstrator’s fans are speed controlled.
In addition to serving as a flight controls systems developmental aircraft, the VTOL subscale demonstrator advanced technologies such as 3D-printed plastics for flight structures and aerodynamic surfaces as well as embedded distributed electric propulsion.
The subscale demonstrator improved methods to develop the aerodynamic databases upon which the air-vehicle control system is modeled, and provided lessons for the flight control system.
With the subscale test flights completed, the aircraft will be preserved for possible additional tests in the future.
Meanwhile, all ongoing-program efforts will focus on the development of the full-scale VTOL X-Plane aircraft.
“These are ambitious performance parameters,” Bagai said, “which we believe will push current technologies to the max and enable a new generation of vertical flight operational capabilities.”
PHOTO 01: Lightning Strike sub-scale version of the XV-24A takes off vertically. (Photo courtesy Aurora)
PHOTO 02: Artist's concept of the full-scale XV-24A vertical takeoff and landing electric plane (Image courtesy Aurora)