Engines
CFM Partners Address Blade Out Risks For Open Fan Engines
RISE engine's RPMs will be less than half of conventional turbofans
CFM RISE engine
CFM partners GE and Safran are developing the RISE open fan engine with new composite fan blades. © GE Aerospace

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.