Left-turning tendencies and ground effect

Why the airplane wants to go left

In airplanes with a propeller that turns clockwise (as seen from the cockpit), four effects make the nose want to go left, especially at high power and low airspeed, like on takeoff and climb. You counter them with right rudder.

• Torque. The engine spins the propeller clockwise, so the airplane wants to roll the opposite way, to the left (Newton's third law).
• Spiraling slipstream. The propeller's slipstream corkscrews around the fuselage and hits the left side of the vertical tail, yawing the nose left.
• P-factor (asymmetric propeller loading). At a high angle of attack, the descending blade on the right side takes a bigger "bite" of air than the ascending blade on the left, so the right side makes more thrust and yaws the nose left. It's strongest at high power and high angle of attack, like a climb.
• Gyroscopic precession. The spinning propeller acts like a gyroscope. When you pitch the nose (for example, raising the tail on a tailwheel takeoff), the force shows up 90° ahead in the direction of rotation, producing a yaw.

Ground effect

When the airplane is within about one wingspan of the ground, the ground interferes with the wingtip vortices and the downwash. That reduces induced drag and lets the wing make the same lift at a lower angle of attack. The effect is strongest very close to the surface.

• On landing, ground effect makes the airplane float, especially if you're too fast. Fly the right approach speed.
• On takeoff, an airplane can lift off in ground effect at a speed too slow to climb out of it. As it rises above ground effect, induced drag increases and it can settle back down. Soft-field takeoffs use ground effect on purpose, but you must accelerate to a safe climb speed before climbing out of it.