We've got a look at what a fusion of helicopters and jets might look like after Bell released a new image. This is the model used by Bell during wind tunnel testing as part of DARPA's Speed and Runway Independent Technology (SPRINT) program.
Rotorcraft such as helicopters have the advantage of taking off and landing vertically in rugged terrain, but their speed is not very high. Jets are fast but need runways, even STOVL type jets need a properly flat surface to land on. It has long been thought that these are two distinct classes of aircraft without much overlap.
That was until the U.S. Defense Advanced Research Projects Agency (DARPA) launched the SPRINT program, which aimed to bring the two classes of aircraft together. An aircraft that could take off, land and hover like a gyroplane, then convert to a jet when flying vertically.
Bell is one of the main contenders in this race, with an X-plane that looks a bit like Bell's V-22 Osprey, with hidden features found in Transformers toys. After takeoff, the X-Plane tilts the rotor nacelles forward for level flight and locks them in place once the jet engines take over. At this point, the rotor blades become a liability and only create drag. To eliminate this, the rotors were designed to fold back into the nacelle.
The idea was tested in 2023 at the Holloman High Speed Test Site (HHSTT) in New Mexico, where an engineering prototype of the stop/fold rotor assembly was photographed to test its folding capabilities under simulated flight conditions. Now, the National Institute for Aeronautics Research (NIAR) at Wichita State University has taken it one step further, with wind tunnel testing completed.
In addition to the technical data collected, the testing also gave us the first look at what the X-plane would look like, which we had previously only seen in artist's renderings. The test model shows a streamlined fuselage, thin wings and V-shaped tail, while folding rotors are visible on the nacelle behind the aerodynamic fairing.
According to Bell, when the technology demonstrator is completed, it will be a pilotable aircraft with an expected subsonic cruise speed of 450 knots (518 mph, 833 km/h), a range of 200 nautical miles (230 miles, 370 kilometers), and an altitude of up to 30,000 feet (9,100 meters). In addition, it can carry a payload of up to 5,000 pounds (2,300 kilograms) in a cabin large enough to accommodate a small aircraft. The hope is that it will provide special forces with greater speed, range, survivability and mobility, particularly in the Indo-Pacific theater.
"After completing transition testing of folding rotors at Holloman Air Force Base last year, we are pleased to have now completed the next phase of testing," said Jason Hurst, Bell's executive vice president of engineering. "Bell's advanced Stop/Fold family of systems will revolutionize the speed, range and survivability of vertical lift aircraft, enabling them to perform missions in contested environments. We are excited to be part of another aviation milestone with this breakthrough technology."