Turning Tendency

Turning Tendencies 

When flying a propeller-driven airplane, particularly during takeoff and climb, pilots encounter several forces that can affect the aircraft. These are known as turning tendencies—natural aerodynamic and mechanical effects that must be anticipated and corrected by the pilot. Left uncorrected, these tendencies can lead to poor directional control, especially at low airspeeds and high power settings. The primary turning tendencies include torque, P-factor (asymmetric thrust), spiraling slipstream, and gyroscopic precession. Understanding the source of each of these tendencies is essential for precise and safe aircraft handling.

Torque

Torque is a result of Newton’s Third Law, which states that for every action, there is an equal and opposite reaction. In the case of an airplane with a clockwise-turning propeller (as viewed from the cockpit), the crankshaft and propeller rotate to the right. In response, the aircraft itself wants to roll to the left. While this torque reaction is primarily a rolling force, on the ground it often results in a yawing motion, since more weight is being placed on the left main wheel, it creates more friction, pulling the aircraft to the left. This effect is most pronounced at high power settings and low airspeeds—conditions commonly experienced during takeoff. To maintain proper directional control, the pilot must apply appropriate right rudder input to counteract the rolling and yawing motion caused by torque.

P-Factor (Asymmetric Thrust)

P-factor, or asymmetric propeller loading, occurs when an airplane is flying at a high or low pitch attitude—most commonly during takeoff, climb, or a descent. In a nose up pitch attitude, the descending blade of the propeller (on the right side from the pilot’s view) meets the relative wind at a steeper angle of attack than the ascending blade on the left. As a result, the descending blade generates more thrust than the ascending blade. This asymmetry causes a yawing force to the left. In a nose down pitch attitude, the ascending blade is at a higher angle of attack than the descending blade. The ascending blade creates more thrust creating a yawing motion to the right. Unlike torque, which is always present during power application, P-factor becomes more pronounced as the pitch attitude changes past level flight. Pilots can recognize its effect by noticing increased left yaw in steep climbs or slow flight, and once again, coordinated rudder use—usually to the right—is essential to maintain straight flight.

Spiraling Slipstream

Another factor that contributes to left-turning tendency is the spiraling slipstream. As the propeller spins, it accelerates air in a corkscrew pattern around the fuselage. This spiraling airflow wraps around the airplane and strikes the left side of the vertical stabilizer. The impact pushes the tail to the right and causes the nose to yaw left. This effect is strongest at low airspeeds when the propeller is producing maximum thrust, such as during takeoff and initial climb. As the airplane speeds up and airflow becomes more streamlined, the effect of the spiraling slipstream diminishes. Nevertheless, during takeoff rolls and power changes, the pilot must be ready to apply right rudder pressure to counteract the leftward yaw caused by this airflow pattern.

Gyroscopic Precession

Gyroscopic precession is a phenomenon that arises from the behavior of spinning objects—in this case, the aircraft’s propeller acting as a gyroscope. When a force is applied to a spinning gyroscope, the resulting reaction does not occur in the direction of the applied force, but instead 90 degrees ahead of it in the direction of rotation. This is particularly noticeable in tailwheel (taildragger) aircraft during takeoff, when the tail is raised and the nose pitches down. This change in pitch applies a force to the top of the propeller disk. Due to gyroscopic precession, the airplane reacts as if the force were applied 90 degrees ahead in the direction of rotation, causing a yaw to the left. While this tendency is generally not as significant in tricycle-gear airplanes, it can be quite noticeable in taildraggers and must be anticipated with appropriate rudder input during the takeoff roll.

Managing Turning Tendencies

Each of these turning tendencies—torque, P-factor, spiraling slipstream, and gyroscopic precession—causes the airplane to yaw or roll, primarily to the left. In many real-world scenarios, these effects act together, especially during takeoff, when high power and low airspeed combine multiple tendencies at once. For this reason, a smooth and continuous application of rudder pressure is often necessary to keep the aircraft tracking straight down the runway and climbing in coordinated flight. Pilots should be especially attentive to the aircraft’s yaw during these critical phases of flight, using outside visual cues, runway alignment, and the slip skid indicator to ensure coordination.

Turning tendencies are inherent to propeller-driven flight and become most apparent when power is high and speed is low. By understanding what causes each of these effects and recognizing when they are likely to occur, pilots can respond with timely and precise control inputs. Mastery of rudder usage and anticipation of these forces are key components of becoming a skilled and confident pilot, especially during takeoff and climb.