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Airbus is evolving the hybrid helicopter technology it developed during the X3 program for civilian application in the Racer (an acronym for Rapid And Cost-Efficient Rotorcraft). Airbus Image

Airbus testing RACER high-speed demonstrator in sim as development continues

By Jon Duke | July 23, 2018

Estimated reading time 4 minutes, 46 seconds.

Airbus Helicopters has revealed new details of the progression of its high-speed RACER program — the compound helicopter developed under the Clean Sky 2 program and direct descendant of the record-breaking X3 technology demonstrator.

Airbus said it is developing RACER with the aim of minimizing the time between certification and a production aircraft. Airbus Photo
Airbus said it is developing RACER with the aim of minimizing the time between certification and a production aircraft. Airbus Photo

Like the X3, Racer — which stands for “Rapid And Cost-Effective Rotorcraft” — features a main rotor, along with two lateral pusher propellers mounted on short “box-wings” that provide lift and thrust in forward flight. The aircraft is still in development, but is already being flown by test pilots at Airbus in a fixed-base simulator.

“The configuration is surprisingly easy to fly, much easier than a tilt-rotor because you are basically flying a helicopter, but with one additional thrust control,” said Hervé Jammayrac, a former H175 project pilot and Airbus Helicopters’ chief test pilot, who also flew the X3 extensively. “If you want to accelerate, you have a switch on the collective to increase or decrease speed. In this configuration, you put the nose where you want to go, and you decelerate using that switch, and you can do this without any automation or autopilot at all.”

Following the success of the X3 program, which saw the aircraft reach a level flight speed of 255 knots and record more than 155 flight hours, Airbus was confident that the twin-propeller compound concept was sound, Jammayrac told Vertical. “We were not sure about the application of the specific design of the concept, but from the beginning we were confident of future development. We were not designing a one-shot project just to break records.”

Getting maximum performance from the X3 involved matching component limits closely to minimize performance bottlenecks. To reduce associated risks and development time, the team used an AS365 Dauphin as a donor airframe, mated with components that were already available but modern enough to confer a degree of future-proofing. While this means that a few critical components of the X3 now find themselves part of the RACER, including a modified variant of the H175 gearbox, others were replaced with recently available products such as Safran’s Aneto engine.

“While there is commonality [with X3] in RACER, there are differences because the aircraft has a different aim,” said Jammayrac. “With X3, we focused closely on safety issues but, as a prototype, [we weren’t] being held back by certification requirements. However, we are developing RACER with the aim of minimizing the time between certification and a production aircraft.”

The X3 was only flown under tightly controlled test conditions by highly qualified and experienced test pilots like Jammayrac. If successful, RACER’s direct derivatives will very quickly be operated “in the wild” by pilots of all experience and skill levels, so the safety factor is intrinsic to the system design. Something that Jammayrac says Airbus Helicopters is very focused on.

The most obvious impact of this has been on the placement of the propellers; the X3s were mounted on the front of the aircraft’s wings, but on the RACER, they’re found behind a biplane-style wing.

“Doing this creates a barrier in front of the propellers, and access to the cabin is in front of this barrier,” Jammayrac explained. “Also, the [box-wing] allows a large wing area beneath the rotor span so the aircraft remains compact, and the downwash effect on the wing area is minimized.” However, he did admit that it is too early to tell what penalties or compromises these changes will incur.

These compromises are currently being explored in Airbus Helicopters’ developmental fixed-base simulator, which Jammayrac is already using to assess the aircraft, although all he would say about this is that “it flies well.”

RACER is being developed under the Clean Sky 2 program, which aims to reduce the environmental impact of aviation, and while a target first flight date has been set, Airbus say safety and simplicity are at the heart of the project, and that the highest priority is to get the design right.

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