OPEN ROTOR ENGINE

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An open rotor is a gas turbine engine where the fan is not within the nacelle. In such designs the fan is referred to as a propeller and can be either a single rotation propeller, i.e., a turboprop, or a pair of contra-rotating propellers, i.e., an open rotor or propfan. There are two principle ways of driving large slow tip speed Propellers, either via a reduction gearbox driven by a high speed, low stage count, low pressure turbine (Allison P&W 578DX), or directly from a contra-rotating statorless multi-stage low pressure turbine (GE36).