Sikorsky, a Lockheed Martin company has validated the advanced control laws to successfully fly a ‘rotor blown wing’ (RBW) uncrewed aerial system (UAS) in both helicopter and airplane modes. Powered by batteries, the 115 pounds (52kg) twin prop-rotor prototype has demonstrated operational stability and maneuverability across all flight regimes, and the potential to scale the unique vertical take-off and landing (VTOL) design to larger sizes requiring hybrid-electric propulsion.

Sikorsky proves a rotor blown wing tail sitter drone can transition easily between helicopter and fixed wing flight modes. Photos by Sikorsky, a Lockheed Martin company.

Very broadly, the RBW design uses a rotor (similar to a helicopter’s main rotor) to provide lift for vertical takeoff and hovering. To transition to forward flight the rotor slows down or even stops as speed increases, and the airflow from the rotor is redirected over a fixed wing—hence rotor-blown wing. This wing generates additional lift, allowing the aircraft to fly more like a conventional airplane, with improved speed and efficiency.

During hover and low-speed flight, the rotor does the heavy lifting. As the aircraft accelerates, forward thrust comes from separate propulsion systems, such as pusher propellers or jet engines, reducing the rotor’s workload. The rotor’s airflow over the wing enhances lift, a bit like a blown flap system in traditional aircraft, but here it’s integrated into the whole flight regime. In some iterations, the rotor might lock in place at high speeds, acting as part of the fixed wing structure, though Sikorsky’s designs typically keep it adjustable for flexibility.

The demo UAS is a tail-sitter VTOL design with a rotor-blown wing configuration, featuring two large proprotors. These aren’t traditional helicopter rotors but rather oversized propellers mounted on nacelles that can tilt. In the vertical takeoff phase, the aircraft sits on its tail, and the two proprotors are oriented upward, providing the lift needed for ascent and hover—much like a helicopter.

During transition, the entire aircraft tilts forward, and the proprotors swivel to a horizontal position, enabling forward flight like an airplane. The “rotor-blown wing” aspect comes from the proprotors’ airflow washing over the fixed wing during this transition and cruise, boosting lift and reducing drag compared to a hovering rotorcraft.

The use of the same two proprotors to handle both vertical lift and horizontal thrust simplifies the design but requires sophisticated control laws to manage the transition smoothly, which Sikorsky has been validating in tests. In January 2025, this battery-powered, 115-pound prototype with a 10.3-foot wingspan completed over 40 takeoffs and landings, including 30 transitions between vertical and horizontal modes, hitting a cruise speed of 86 knots in forward flight.

Sikorsky Innovations, the company’s rapid prototyping group, heads the effort to develop and mature the rotor blown wing design. In just over a year, Sikorsky Innovations has progressed through preliminary design, simulation, tethered and untethered flight to gather aerodynamic, flight control and quality data.

Breakthrough was achieved in January 2025 with the 10.3-ft composite wingspan aircraft when Sikorsky Innovations successfully completed more than 40 take-offs and landings. Notably, the aircraft performed 30 transitions between helicopter and airplane modes, the most complex maneuver demanded of the design. In horizontal flight mode, the aircraft reached a top cruise speed of 86 knots. Simultaneous wind tunnel tests were conducted on a 1:1 scale model providing valuable validation of the newly developed control laws by correlating them with real-world experimental data.

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. 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.

—Sikorsky Innovations Director Igor Cherepinsky

Applications of future UAS rotor blown wing aircraft include search and rescue, firefighting monitoring, humanitarian response, and pipeline surveilling. Large variants will enable long range intelligence, surveillance and reconnaissance, and piloted drone teaming (crewed/uncrewed teaming) missions.

All rotor blown wing variants will include Sikorsky’s MATRIX flight autonomy system to navigate the aircraft during flight.

The rotor blown wing design is one of a future family of systems in development by Sikorsky. The family will include winged VTOL UAS and single main rotor aircraft.

Also in development by Sikorsky is a 1.2 megawatt hybrid-electric demonstrator (HEX) configured with a tilt wing and a fuselage to carry passengers or cargo across long distances. A HEX power system test bed is expected to demonstrate hover capability in 2027.