An endurance flight is a fight against gravity, wind, human limitations, and fuel capacity. The HQ drone series, designed by Latitude Engineering, set a record for longest flight by a vertical takeoff or landing aircraft in 2016, staying in air for more than 22 hours. The technology that enabled that flight, the unique combination of airframe and software, was granted a patent on Dec. 25, just in time for the HQ’s systems new owners, L3 Technologies, to start floating the hybrid quadcopter as the right vehicle for the Army’s Future Tactical Unmanned Aircraft System competition.

The rough concept and early prototypes of the HQ drone series have been around since at least 2013. Combining the VTOL capabilities of a quadcopter with the flight efficiency of a fixed-wing plane, the craft relies on four rotors on booms to get the plane up and down, while a pusher prop and traditional wings carry it through the sky normally. The record-setting flight in 2016 was performed by the HQ-60 model of the drone, and demonstrated at the time before an audience consisting of military and public safety professionals, including Special Operations Forces.

Part of what likely makes the Hybrid Quadcopter so adept at staying airborne is the software balancing its two flight modes. Rotorcraft prefer to tilt forward for extra forward momentum, but that’s counterproductive with fixed wings, since it changes the angle of the wings and increases drag while losing lift. So it’s the software’s ability to manage the dual-modes of the craft that’s at the heart of this patent, enabling normal flight, vertical flight, and hovering, especially in high winds.

It’s that ability to operate in high winds that L3 expresses as the key component of the patent, and likely the feature it will use to distinguish this specific brand of fixed-wing/quadcopter hybrid from the competition.