Aircraft equipped with
contra-rotating propellers, also referred to as
CRP,
coaxial contra-rotating propellers, or
high-speed propellers, apply the maximum power of usually a single
piston or
turboprop engine to drive two
coaxial propellers in
contra-rotation (rotation about the same axis in opposite directions). Two propellers are arranged one behind the other, and power is transferred from the engine via a
planetary gear or
spur gear transmission. Contra-rotating propellers should not be confused with
counter-rotating propellers—airscrews on separate shafts turning in opposite directions.