US Defense Advanced Research Projects Agency (DARPA) is proceeding with work to develop a full-scale version of Hybrid Electric vertical takeoff and landing VTOL X-Plane.
DARPA has already completed flight-testing of the sub-scale version of a novel aircraft design as part of its vertical takeoff and landing (VTOL) X-Plane program, the agency announced Tuesday.
Developed and fabricated by Aurora Flight Sciences, the aircraft includes 24 electric ducted fans—18 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.
The tests suggest there is a time in the not-so-distant future when VTOL aircraft could fly much faster and farther than any existing hover-capable craft, and take off and land almost anywhere.
Subscale testing began on the VTOL program in March of 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 specifically 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 subscale aircraft flight and mission control architectures will, for the most part, be carried over into the full-scale VTOL aircraft, but with a few additions and improvements.
According to Bagai, the full-scale aircraft will incorporate a triple-redundant flight control system instead of a single system. A hybrid turboshaft engine driving electric generators to power the fan units, versus the demonstrator’s batteries, will power the full-scale aircraft.
Finally, the full-scale aircraft fan units will be synchronized to the generators and turn at a constant RPM, but incorporate variable pitch, whereas the demonstrator’s fans are speed controlled.