Tail Wheel Planes

Cessna 180

The center of gravity on a tail wheel plane is located between the main and tail gear. When you land a tail wheel plane

a little side ways your center of gravity still wants to go forward, kind of like your upper body does in a car as you turn around a corner. Friction on the tires is turning the plane in the direction that the plane is facing. The center of gravity is then thrown in the opposite direction. This two-force action creates a moment since it is spaced away from the center of gravity. The two force, or couple moment, acts against your desire to roll down the runway and makes you spin in circles if you're lucky, or tip if you're not.