At the Paris Air Show, Airbus has unveiled a new demonstrator rotorcraft concept optimised for a cruise speed of approximately 400 km/h.
The Racer (Rapid And Cost-Effective Rotorcraft) concept uses a main rotor for lift and basic flight modes, along with two lateral pusher rotors that generate thrust in forward flight plus a box-wing to provide lift in cruise mode.
Tomasz Krysinski, Vice President of Research & Innovation at Airbus Helicopters, said the box-wing, was crucial to the overall design effectiveness.
“The staggered-type box-wing has a smaller overall surface than a normal wing, so it is less affected by performance-reducing rotor downwash, and therefore, less power is required to hover,” Krysinski said. “However, the box-wing’s upper and lower segments create all the lift we need in forward flight.”
Another advantage is the ability to integrate the landing gear into the box wing’s lower segment. This facilitates the kinematics for the landing gear’s retraction, while also providing lower weight and lower cost.
The propellers are installed on the back of the box-wing in a pusher arrangement, reducing the power required during forward flight by 10 per cent – thereby lowering fuel consumption and increasing flight range.
The Racer draws on Airbus's X3 high-speed demonstrator, also a compound rotorcraft, which showed that high speed, highly efficient results could be obtained when the main rotor’s rotational speed is slowed down during forward flight, and thrust is provided by propellers mounted on a wing that provides lift.
“The X3 flew a total of 350 hours with excellent results – which were confirmed by pilots from many countries who were given the opportunity of being at the controls,” said Krysinski.
“In the second step with Clean Sky 2, we are now taking a clean-sheet approach in creating a new demonstrator that shows its suitability for the missions – which include emergency medical services, search and rescue, public services, along with commercial and business aviation.”
Final assembly of the Racer demonstrator is planned to start at Airbus Helicopters in 2019, with a first flight the following year. It will be based on a hybrid metallic-composite airframe, with two RTM322 turboshaft engines linked by a supercritical shaft to drive the main rotor and pusher propellers. An electrically-powered “eco mode” will allow one of the RTM322 engines to be stopped in flight – and quickly restarted when needed – thus generating fuel savings and increasing range.
[An artist's impression of the Racer. Image: Airbus]