Left-turning tendencies

The three yaw tendencies

Definition

A US-built engine turns the propeller clockwise as you see it from the cockpit, and three separate effects use that spin to yaw the nose left. P-factor: at a high angle of attack — climbing or slow — the downward-moving blade on the right side of the disc meets the air at a steeper angle and makes more thrust than the upward-moving blade on the left, so the nose swings left. Spiraling slipstream: the propwash corkscrews back around the fuselage and strikes the left side of the vertical fin, pushing the tail right and the nose left. Gyroscopic precession: the spinning prop acts like a gyroscope, so a pitch change shows up as a force ninety degrees later in the direction of rotation — raise the tail or lower the nose and it yaws left.

Explanation

All three are strongest when power is high and the airplane is slow at a high angle of attack — exactly the takeoff and initial climb. You hold the nose straight with right rudder, keeping the ball centered.

Figure 5-48. Corkscrewing slipstream. — Figure 5-48 · FAA-H-8083-25C, Pilot's Handbook of Aeronautical Knowledge (p. 128)

Why it matters

Uncorrected left yaw in the climb is uncoordinated flight, and close to the stall an uncoordinated airplane can drop a wing and spin. Right rudder on climb-out is a safety habit, not just tidiness.

From the Right Seat

I tell students the airplane 'asks for right rudder' the moment they push the throttle up — anticipate it rather than chase it after the nose has already swung.

A DPE might ask

Name the left-turning tendencies and say which are yaws.
Why is right rudder needed on takeoff and in the climb?

PHAK ch. 5 — Torque & P-factor

Torque: the roll tendency

Definition

Torque is the odd one out — it's a roll, not a yaw. By Newton's third law, the engine spinning the propeller one way rolls the airframe the other way: for a clockwise prop that's a left roll, strongest at high power and low airspeed. In cruise it's a mild tendency you trim out or hold off with a little right aileron, and many airplanes build in a slight rigging offset to help. On the takeoff roll the left roll also presses down the left main wheel, adding to the leftward pull on the ground.

Explanation

Keeping yaw and roll straight matters because they're fixed with different controls: the rudder handles the three yaw tendencies, while aileron and trim handle the torque roll. On a normal takeoff you're doing both — right rudder for the yaw and a touch of right aileron for the roll.

Figure 5-47. Torque reaction. — Figure 5-47 · FAA-H-8083-25C, Pilot's Handbook of Aeronautical Knowledge (p. 128)

Why it matters

If you treat all four as 'the same thing,' you'll reach for the wrong control. Naming torque as a roll is what tells you to use aileron or trim for it and save the rudder for the yaw.

Common error

A common mix-up is to think you counter these tendencies with left rudder, or that torque is a yaw. Every tendency is to the left, so the yaw fix is right rudder; and torque is a roll, held off with right aileron or trim — not rudder.

Which control primarily counters propeller torque (the left roll)?

Safety

Set climb trim and expect to carry right rudder the whole climb. If a wing keeps dropping, that's the torque roll — level it with aileron, don't try to fix it with rudder.

A DPE might ask

Why is torque a rolling tendency rather than a yaw?
How do you counter the torque roll versus the yaw tendencies?

Airplane Flying Handbook — Torque effect & takeoff