Definition
The tendency of a propeller-driven airplane to roll in the opposite direction of propeller rotation, caused by the engine applying torque to spin the propeller and the propeller applying an equal and opposite reaction back through the airframe. In most U.S. airplanes the propeller turns clockwise when viewed from the cockpit, so the airframe tends to roll left, especially at high power and low airspeed.
Plain English
When the engine spins the propeller one way, the airplane wants to roll the other way. Pilots feel this most during takeoff and climb, when power is high and the airplane is flying slowly.
Context Anchor
Encountered when comparing propeller airplanes with jet airplanes, and in propeller airplanes during high-power situations such as takeoff and climb.
Derivation
Torque comes from the Latin torquere, meaning 'to twist.' The engine twists the propeller one way, and the airplane gets twisted the other way as a reaction.
Why Pilots Care
It creates a strong left-rolling force at high power settings that must be countered with right rudder to maintain directional control.
Analogy
It is like using a strong drill: as the drill bit turns one way, the drill body can try to twist the other way in your hand.
Intuition Check
Propeller torque effect does not mean every handling change caused by a propeller. It specifically means the airplane’s rolling reaction to the propeller being twisted by the engine.
Example Sentence 1
On the takeoff roll, the student felt the airplane try to roll left from propeller torque effect and added right aileron to keep the wings level.
Example Sentence 2
In the climb the pilot increased right rudder pressure as power was added because the propeller torque effect became stronger.