U.S. aircraft manufacturer Bell Textron Inc. has been tasked by DARPA (Defense Advanced Research Projects Agency) to advance to the second phase of the SPRINT program (Speed and Runway Independent Technologies). The goal is to create a groundbreaking high-speed aircraft, known as the X-Plane, capable of vertical takeoff. For the first time, it will feature the innovative stop–fold rotor technology.
Bell is leading the design, construction, ground testing and certification of a working prototype. The project focuses on a highly adaptable aircraft that can take off and land vertically, use short runways when needed and fly like a conventional jet at cruising speeds of up to 515 mph.
Central to the design is the innovative stop–fold technology. While the rotors enable vertical takeoff, they are fully stopped and folded away once the aircraft transitions to horizontal flight. Unlike traditional tiltrotor systems, where rotors keep spinning and create drag during forward motion, stop–fold greatly reduces air resistance and boosts efficiency at high speeds.
During cruise flight, separate engines take over propulsion, providing a balance of speed and agility. According to Bell, the aircraft features a modular design that can be tailored for a range of military operations – from medical evacuation to precision strikes on enemy radar systems. A released render video showcases several potential mission scenarios, highlighting the platform’s versatility in action.
Flight tests are planned for 2028, with the current phase of ground testing and certification scheduled to run through 2027. On Reddit, the stop–fold technology is already being hailed as a “potential game changer” for its promise to reshape the future of high-speed vertical flight.