What is the primary force that causes an airplane to turn?

The primary force that causes an airplane to turn is actually lift, specifically the lateral component of lift when the aircraft is banked. When a pilot wants to initiate a turn, they bank the aircraft, which tilts the lift vector to one side. This creates a horizontal component of lift that acts towards the center of the turn, thereby enabling the airplane to change direction.

Centrifugal force is a perceived force that feels like it acts outward on a body moving in a curve, but it is not a real force that acts on the airplane. It's a result of inertia, where the airplane tends to continue moving in a straight line due to its mass. However, in the context of airplane dynamics, it is the tilting of the lift in conjunction with gravity that facilitates the turn, not centrifugal force.

Understanding the role of lift in turns is crucial for pilots, as it highlights the importance of banking and adjusting the angle of attack to effectively navigate through airspace while maintaining control.