Aerospace New Aircraft Engines: Airbus and CFM Test Demonstrator of an Open Fan

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To achieve the aviation industry's climate goals by 2050, new propulsion systems and concepts are necessary. An open fan could help increase an aircraft's fuel efficiency. In this context, Airbus and its engine partner CFM International are testing the demonstrator of an open fan.

The open fan engine architecture is considered a promising technology for the aviation industry to achieve its climate goals by 2050. The open fan combines the fuel consumption of a turboprop with the performance and speed of a turbofan. Ahead of real flight tests, Airbus and its engine partner CFM are conducting wind tunnel tests on an open fan demonstrator to study its aerodynamic and acoustic performance.

Minimize Fuel Consumption

The development of a future aircraft at Airbus begins with reducing fuel consumption. Improved aerodynamics can make a significant contribution, but above all, the propulsion can make a noticeable difference. The aerodynamic profile, acoustic footprint, and easy integration of the open fan are critical factors compared to the Ultra-High Bypass Turbofan (UHBR).

Therefore, CFM, a joint venture between GE Aerospace and Safran Aircraft Engines, has developed a corresponding demonstrator over the past three years as part of its technology demonstration program "Revolutionary Innovation for Sustainable Engines" (RISE).

Before the Flight Test, the Wind Tunnel Test Takes Place

Airbus and CFM now aim to jointly test the open fan and analyze its potential for use in a future aircraft. Before flight testing, the open fan architecture and its integration into the aircraft undergo a wind tunnel test. In this testing phase, two "minimum body models" are used: a 1:5.5 scale model for high-speed tests and a 1:7 model for low-speed tests.

Each model is tested both individually and with a scale wing to evaluate how the two interact. For the low-speed model, the examination extends to high-lift devices such as flaps and slats. The tests take place in wind tunnels belonging to the French aerospace laboratory ONERA (high speed) and DNW, a Dutch-German facility in the Netherlands (low speed). Both provide extremely accurate data.

The high-speed tests took place at ONERA at the beginning of last year. They collected experimental data that allowed researchers to examine the installation effects of the models and the performance of the propeller. Subsequently, in the fall, tests simulating takeoff and landing were conducted at DNW. They focused on the aeroacoustic performance of the open fan and the interaction with high-lift devices.

Because engines with open fans are not ducted, managing the noise of their larger rotor blades requires new design decisions and new technologies at both the engine and aircraft levels. Nonetheless, the engines must still comply with acoustic regulatory and certification requirements.

On the Way to Flight Testing

After more than 500 test hours, this first "minimum body" campaign is coming to an end. The next step is to evaluate, using 1:11 (high speed) and 1:14 (low speed) full aircraft models, how an open fan propulsion system impacts aircraft performance. These models will be tested in 2026 in ONERA's high-speed wind tunnel and Airbus's low-speed facility in Filton, UK. Design and production are already underway.

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