Torque effect
From Infogalactic: the planetary knowledge core
The torque effect experienced in helicopters and single propeller-powered aircraft is a result of Isaac Newton's third law of motion that "for every action there is an equal and opposite reaction"
In helicopters, the result of the torque effect is a tendency of the main rotor to want to turn the fuselage in the opposite direction from the rotor.
In a single-propeller plane, the result of the torque effect is a tendency of the plane to want to turn upwards and left in response to the propeller wanting to turn (bank) the plane in the opposite direction of the propeller spin.
