rotating noise

Aircraft equipped with contra-rotating propellers (CRP), coaxial contra-rotating propellers, or high-speed propellers, apply the maximum power of usually a single engine piston powered or turboprop engine to drive a pair of coaxial propellers in contra-rotation. Two propellers are arranged one behind the other, and power is transferred from the engine via a planetary gear or spur gear transmission. Although contra-rotating propellers are also known as counter-rotating propellers, the term is much more widely used when referring to airscrews on separate non-coaxial shafts turning in opposite directions.

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