Definition
A propeller arrangement on a multi-engine aircraft in which the propeller on one engine rotates clockwise (as viewed from behind) while the propeller on the other engine rotates counterclockwise. This balanced arrangement cancels out the asymmetric thrust effects that would otherwise occur if both propellers turned the same direction, eliminating the concept of a 'critical engine.'
Plain English
On a twin-engine plane with this setup, the two propellers spin in opposite directions, which keeps the aircraft balanced if one engine fails.
Context Anchor
Seen in multi-engine aircraft descriptions, systems discussions, and training about engine-out handling.
Derivation
From Latin 'contra' (against) and 'rotare' (to turn). The name simply describes propellers that turn against each other -- one clockwise, one counterclockwise.
Why Pilots Care
Reduces the strong left-turning tendency during takeoff and climb, making the aircraft easier to control and safer in engine-out situations.
Intuition Check
Counter-rotating does not mean the propellers reverse direction in flight. It means each propeller has its own normal direction of rotation, and those directions are opposite each other.
Example Sentence 1
Because the trainer was equipped with counter-rotating propellers, the instructor explained that there was no critical engine to memorize.
Example Sentence 2
Transition training emphasized that counter-rotating propellers eliminate the critical engine distinction found on conventional twins.