The US Defense Advanced Research Projects Agency (DARPA) has selected Aurora Flight Sciences to build a full-scale X-plane to demonstrate the viability of using active flow control (AFC) actuators for primary flight control. The award represents Phase 3 of the Control of Revolutionary Aircraft with Novel Effectors (CRANE) programme.
While conventional aircraft of all types use a system of movable, external control surfaces for flight control, the CRANE programme’s X-65 technology demonstrator breaks this century-old design paradigm for flight control by using jets of air from a pressurised source to shape the flow of air over the aircraft surface, with AFC effectors on several surfaces to control the aircraft’s roll, pitch, and yaw. Eliminating external moving parts is expected to reduce weight and complexity and to improve performance.
“The X-65 is a technology demonstrator, and it’s distinctive, diamond-like wing shape is designed to help us maximise what we can learn about AFC in full-scale, real-world tests,” Dr Richard Wlezien, DARPA’s program manager for CRANE, was quoted as saying in a 3 January 2204 DARPA press release.
The X-65 will be built with two sets of control actuators – traditional flaps and rudders as well as AFC effectors embedded across all the lifting surfaces. This is designed to both minimise risk and maximise the programme’s insight into control effectiveness. The X-65’s performance with traditional control surfaces will serve as a baseline, while successive tests will selectively lock down moving surfaces, using AFC effectors instead.
“The X-65 conventional surfaces are like training wheels to help us understand how AFC can be used in place of traditional flaps and rudders,” said Wlezien. “We’ll have sensors in place to monitor how the AFC effectors’ performance compares with traditional control mechanisms, and these data will help us better understand how AFC could revolutionise both military and commercial craft in the future.”
The 7,000 lb (3,175 kg), unmanned X-65 will have a 30 ft (9.144 m) wingspan and be capable of speeds up to Mach 0.7 (864.36 km/h). Its weight, size, and speed – similar to a military trainer aircraft – make the flight-test results immediately relevant to real-world aircraft design.
“We’re building the X-65 as a modular platform – wing sections and the AFC effectors can easily be swapped out – to allow it to live on as a test asset for DARPA and other agencies long after CRANE concludes,” said Wlezien.
Aurora Flight Sciences, a Boeing company, has already started fabricating the X-plane at Aurora facilities in West Virginia and Mississippi; plans include building the airframe at Aurora West Virginia, followed by system integration and ground testing at Aurora’s headquarters in Manassas, Virginia.
The X-65 is scheduled to be rolled out in early 2025, with the first flight planned for summer of the same year.
“It’s thrilling to be able to say, ‘We’re building an AFC X-plane,” said Wlezien. “I came to DARPA in 1999 to work on a programme called Micro Adaptive Flow Control [MAFC], which helped pioneer the foundational understanding of fluid dynamics that eventually led to CRANE. I left DARPA in 2003 after managing MAFC, and it’s the chance of a lifetime to come back and help see that early work come to fruition in a full-scale physical aircraft. Aerospace engineers live to see their efforts take flight.”
