Why do airplanes bank when turning?

Lift is a crucial aerodynamic force that allows airplanes to rise off the ground and remain airborne. It is created when air flows over and under the wings of an aircraft, generating a pressure difference. The design of the wing, specifically its airfoil shape, is pivotal to this process.

As air moves over the wing's surface, it travels faster and generates lower pressure compared to the slower moving air under the wing, which creates higher pressure. This disparity in pressure is what propels the plane upward, opposing the force of gravity. The magnitude of lift must be equal to the weight of the aircraft for it to sustain level flight. Pilots can adjust lift by altering the wing's angle of attack or the aircraft's speed, both of which are vital in executing various maneuvers, including turns.

Centripetal force is the invisible tether that keeps an object moving in a circular path, pulling it towards the center of rotation. Imagine swinging a ball on a string; the tension in the string is analogous to centripetal force.

In aviation, when a plane turns, it needs this inward force to change direction while maintaining its path along a curved trajectory. The component of lift that gets redirected sideways when an airplane banks acts as the centripetal force. This force is necessary for the aircraft to perform a coordinated turn, where the airplane's heading is changed without slipping to the side or losing altitude. It's a fine balance between lift and the plane's inertia, which inherently aims to keep moving in a straight line, due to Newton's first law of motion.

Turning maneuvers in flight are complex operations that involve a precise balance of forces. A pilot initiates a turn by banking the airplane, which tilts the lift vector and provides the horizontal component needed for the turn.

The balance between the lift and the weight of the airplane shifts as the plane banks. To maintain altitude during a turn, the pilot must increase the angle of attack or speed to compensate for the reduced vertical component of lift. This requirement arises from the conservation of energy and the need to counteract the gravitational pull. An efficient turn is one where the aircraft neither gains nor loses altitude unnecessarily, maintains a steady speed, and achieves the desired change in direction.

Banking refers to the tilting of an aircraft to one side. In aerodynamics, this maneuver is essential for changing the aircraft's flight path. The lift normally acts in the opposite direction of gravity, but when a plane banks, the lift vector tilts and divides into two components: one vertical and one horizontal.

The horizontal component is what enables the plane to turn. Think of it as an invisible hand pushing the airplane sideways. For an effective banked turn, the combined lift force (both vertical and horizontal components) must be greater than when the airplane is flying level. Hence, pilots often increase the thrust or adjust the wing flaps to generate sufficient lift. The steeper the bank, the greater the centripetal force required, which can result in higher g-forces felt by passengers and crew.