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Doors covering the embedded lift fans are open in the vertical flight phase.
Aurora Flight Sciences has unveiled a refined concept for a fan-in-wing high-speed vertical-takeoff-and-landing (VTOL) aircraft as it receives funding to proceed to a preliminary design review under a DARPA project to fly an X-plane demonstrator.
Boeing-owned Aurora is the first performer to be awarded a contract for Phase 1B of DARPA’s Speed and Runway Independent Technologies (Sprint) project to fly a demonstrator for an aircraft that combines a VTOL aircraft capability with a 450-kt. cruise speed.
One of four companies awarded Sprint Phase 1A conceptual design contracts in November 2023, Aurora received an almost $25 million contract modification on April 30 for Phase 1B, with the work expected to be completed in June 2025. DARPA’s goal is a first flight within 36 months.
Aurora has previously shown a concept for a crewed aircraft with four lift fans embedded in a blended wing body airframe. The latest artists’ renderings show an uncrewed aircraft, still a blended wing body but with three lift fans, two in the wing and one on the forward fuselage.
“The choice of three lift fans reflects the [Aurora/Boeing] team’s strategy to simplify the demonstrator and streamline its path to flight test,” Aurora says. It noted the fan-in-wing technology can be scaled to four or more lift fans for future aircraft.
“Similarly, while an uncrewed demonstrator offers benefits in testing and risk reduction, the [fan-in-wing] technology would be fully transferable to traditional aircraft with crews,” the company says.
Aurora’s latest design has a refined composite exterior with large angled inlets under the nose and a conventional jet exhaust between the V tails. The wing fans are covered by semi-circular upper doors hinged along their centerline as in the Ryan XV-5 Vertifan fan-in-wing VTOL experimental aircraft first flown in 1964.
The fuselage fan is covered by a door that slides aft and longitudinal louvers that vector fan thrust for control in vertical flight as just visible below the fuselage. The XV-5 also had lateral louvers under its wing fans for control, and these are just visible in Aurora’s artist’s rendering.
Rectangular upper-fuselage doors inboard of the wing fans that hinge open in vertical flight, along with flush exhausts below the V-tail, suggest the lift fans may have their own propulsion system, but that is not confirmed by Aurora. The XV-5’s lift fans were tip driven by diverted engine exhaust gases.
Past DARPA X-plane programs have seldom reached flight, most often because the research agency failed to secure the required support from a military service to transition the technology after demonstration. As a result, DARPA has been looking at rescoping its X-planes to be more affordable but still result in flying something that could be useful to a customer.
This approach appears to be supported by Aurora’s decision to redesign its Sprint X-plane as an uncrewed aircraft with only three lift fans. Bell, Piasecki Aircraft and Northrop Grumman were also awarded Phase 1A contracts and at least one more Phase 1B performer is expected to be named.
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