Bell Textron Inc. took a decisive step forward in the development of its in-flight rotor folding system (Stop/Fold) by recently completing wind tunnel testing at Wichita State University’s National Institute for Aeronautics Research (NIAR) as part of the DARPA Speed and Runway Independent Technology (SPRINT) program. This breakthrough follows successful testing at the Holloman High Speed Runway in New Mexico in 2023, and represents a key milestone toward flight demonstration of the concept. This technology is essential for aircraft that will employ the High Speed Vertical Takeoff and Landing Technology (HSVTOL) that Bell is developing.

Bell’s Stop/Fold folding rotor system was subjected to rigorous testing in both wind tunnel and real-world conditions on the ground. These tests served to validate the stability and control of the aircraft during the in-flight rotor folding and unfolding sequence, a key technical challenge in ensuring the viability of aircraft that combine jet speed with vertical takeoff and landing capabilities. With the successful completion of both test phases, the concept is now ready to advance to the next stage of the program, which includes a full-scale flight demonstration.

“After completing folding rotor transition testing on the sled at Holloman Air Force Base last year, we’re thrilled to have now completed this next phase of testing,” said Jason Hurst, executive vice president, Engineering, Bell. “Bell’s advanced Stop/Fold family of systems will revolutionize the speed, range and survivability of vertical lift aircraft to enable operations in contested environments. We are excited to be part of another aviation milestone with this breakthrough technology.

Bell’s scalable Stop/Fold configurations combine the speed of a modern jet with the runway independence of helicopters, offering next-generation capabilities that will transform the battlefield of the future.

The technology Bell is developing will enable the aircraft to take advantage of available runways to optimize payload and range, while their powerful vertical lift capability will allow them to continue operating even in the absence of runways. HSVTOL-type aircraft will be able to operate from virtually any location, providing a distinct strategic advantage, especially in the Indo-Pacific theater, where distances are vast, airspace is highly contested and infrastructure is limited or sometimes non-existent.

This unique combination of capabilities is also ideal for Special Operations, enhancing speed, range and survivability in our most challenging and sensitive missions.