Bell’s high-speed vertical lift demonstrator for DARPA’s SPRINT program has received the official X-76 designation after passing its Critical Design Review, transitioning from design to manufacturing, integration, assembly, and ground testing.
The SPRINT program, a joint DARPA and U.S. Special Operations Command effort launched in November 2023, seeks to develop runway-independent technologies enabling cruise speeds exceeding 400 knots—up to 450-500 knots—while hovering in austere environments and operating from unprepared surfaces. This addresses the aviation tradeoff between fixed-wing speed and vertical lift flexibility.
In July 2025, Bell was downselected for Phase 2 over Aurora Flight Sciences, following preliminary design phases. The X-76 designation nods to 1776, marking the U.S.’s 250th anniversary and the experimental X-plane tradition. DARPA program manager Cmdr. Ian Higgins stated, “For too long, the runway has been both an enabler and a tether, granting speed but creating a critical vulnerability. With SPRINT, we’re not just building an X-plane; we’re building options.”
Central to the design is Bell’s Stop/Fold rotor technology: proprotors at wingtips stop rotating, fold into engine nacelles post-transition from hover, minimizing drag for jet-powered forward flight. Wind tunnel tests at Wichita State University’s NIAR validated stability during transitions. Phase 3 flight testing targets early 2028. The scalable concept suits gross weights from 4,000 to 100,000 pounds, supporting cargo, personnel, crewed, or uncrewed variants.
Bell Senior Vice President of Engineering Jason Hurst noted, “Bell is honored to receive the X-76 designation and continue the spirit of American innovation honoring the founding of the United States in 1776.”