What force contributes to an airplane turning during a bank?

The horizontal component of lift is the force that specifically contributes to an airplane's turning during a bank. When an aircraft banks, the lift vector tilts along with the airplane's wings relative to the horizontal plane. This tilting results in two components of lift: one that acts vertically to counteract the weight of the airplane and another that acts horizontally towards the center of the turn.

This horizontal component of lift is critical because it provides the necessary centripetal force to change the aircraft's direction. As the aircraft continues to bank, maintaining an appropriate angle, the increased horizontal lift allows the airplane to execute a turn efficiently.

In contrast, thrust produced by the engines primarily propels the airplane forward but does not contribute to the lateral force needed for turning. Weight acts straight down due to gravity, balancing the vertical lift, but does not aid in the turn itself. Increased drag on the low wing can impact the efficiency of the turn but does not directly contribute to the turning force. Hence, it's the horizontal component of lift that plays the essential role in facilitating a turn during a bank.