Lockheed Martin subsidiary Sikorsky has successfully flown an electric-powered, 115-lb (52-kg) autonomous drone that uses what it calls a "rotor blown wing" to fly like both a helicopter and an airplane and can be scaled for larger airframes.
The rotor blown wing (RBW) design directs the backwash from the propellers or rotors over the wing surfaces, reducing drag and increasing lift by increasing the velocity of the air. Though there are some trade-offs in power and efficiency, this allows STOL and VTOL aircraft to not only take off from short runways, it also enhances flight controls.
In addition, Sikorsky says its RBW design also helps tail-sitter or tilt-rotor aircraft and similar vehicles have smoother transitions from hovering to slow horizontal flight to cruising speeds. This is one of the reasons Sikorsky exploited the approach for its latest tail-sitting drone.
According to Lockheed Martin, the purpose of the first flights of the twin prop-rotor prototype was to demonstrate its operational stability and maneuverability across all flight modes, as well as the design's scalability for larger hybrid-electric variants and the ability of a RBW to reduce drag from the wing while hovering.
In particular, one task of the project was to demonstrate Sikorsky Innovations, the company's rapid prototyping group, to go from preliminary design to untethered flight of the protoype in a little over a year.
The flight tests in January 2025 consisted of over 40 takeoffs and landings along with 30 extremely complex transitions between helicopter and airplane mode, reaching a top cruise speed of 86 knots (99 mph, 159 km/h). These were conducted in parallel with wind tunnel tests of a full-scale model to allow comparison between workbench and real-world results – especially regarding the advanced control laws of the flight systems, including Sikorsky's MATRIX flight autonomy system, which are the mathematical expression of how they make the aircraft more stable and controllable.
When the technology is mature, expected applications include search and rescue missions, firefighting monitoring, humanitarian responses, pipeline surveillance, long range intelligence, surveillance and reconnaissance, and teaming with crewed aircraft for combat missions.
"Our rotor blown wing has demonstrated the control power and unique handling qualities necessary to transition repeatedly and predictably from a hover to high-speed wing-borne cruise flight, and back again," said Sikorsky Innovations Director Igor Cherepinsky. "New control laws were required for this transition maneuver to work seamlessly and efficiently. The data indicates we can operate from pitching ships decks and unprepared ground when scaled to much larger sizes."
Source: Lockheed Martin