Safran is preparing to begin key wind-tunnel tests of a fuel-saving geared open-rotor engine being developed under Europe’s Clean Sky government-industry research program.

Under Clean Sky’s Sustained and Green Engines (SAGE) program, the tests of a 1/5th-scale powered model at French aerospace research organization Onera in Modane will measure performance and acoustics.

Safran company Snecma is aiming for a fuel-burn reduction of 25-30% over today’s CFM56 turbofan, and a noise level lower than engines now being introduced. “Keeping noise at a reasonable level is still a challenge, but we think it is feasible,” says Pierre Guillaume, director of research and technology.

Under Clean Sky, Snecma plans to ground-test the SAGE 2 geared open-rotor demonstrator at the end of 2015. Flight tests, on a modified Airbus A340-600, have slipped to the follow-on Clean Sky 2 program now being proposed, and would take place in 2019, he says.

The wind-tunnel tests, to be conducted between July and October, “are a real next step, the first clear achievement for us on the road to a ground demonstrator,” says Guillaume. Work so far has involved simulation of aerodynamics and aero-acoustics.

Phased subsystem preliminary design reviews for the demonstrator started a few weeks ago, he says. Configuration freeze and the start of detail design is scheduled for early 2014.

The focus of SAGE 2 is developing the propulsion module—gearbox, rotating structure and blades. The ground demonstrator will use a Snecma M88 fighter enegine as the gas generator to drive the counter-rotating rotors—a 14-ft.-dia. forward row of 12 blades, and a second row of 10 blades rotating in the opposite direction.

The ground demonstrator is sized at around 25,000-lb. thrust, in the same class as the CFM56, and the variable-pitch composite blades use the same three-dimensional woven carbon-fiber technology as CFM’s new Leap-1 engine, now in development, says Guillaume.

Flight-testing would take the geared open-rotor to a technology readiness level of 6 by 2020, ready to enter product development. “These demonstrations are really crucial if we are to get the maturity of the concept and take this engine to market in 2025-2030,” he says.