CFM Partners Address Blade Out Risks For Open Fan Engines

The Open Rotor engine and its evolution, the Open Fan, promise dramatically lower fuel consumption compared with evolutions of the ducted fan engine. The Open Rotor has counter-rotating fans, while the Open Fan has a single rotating fan with stators that do not rotate behind it, which can be adjusted or pivoted for maximum efficiency.

Open Rotor testing in the 1980s proved noisy, offered slower cruising speeds than conventional jet engines, and caused vibration that transferred to the vertical tails of the Boeing 727 and McDonnell Douglas MD-80 test beds. Questions about maintenance and concerns over blade failure were paramount.

According to the developers of the Open Fan—GE Aerospace, and Safran, under the CFM International brand—objections to the Open Rotor design have been overcome. They say the noise is lower than that of the CFM LEAP engine, according to testing with its planned RISE (Revolutionary Innovation for Sustainable Engines) propulsion system.

The cruising speed is now projected to be comparable to today’s Airbus A320neo and Boeing 737 MAXs. Maintenance durability, reliability, and dust ingestion testing aims to overcome reported entry-in-service maintenance shortcomings of the LEAP and competing Pratt & Whitney Geared Turbofan (GTF) engines.

However, some industry and airline officials Leeham News and Analysis (LNA) talks to aren’t yet convinced that blade out concerns have been resolved. “We’re designing for blade-outs,” GE’s Arjan Hageman, vice president for the future of flight at GE, said in an interview earlier this month.

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