What part of the turn coordinator indicates the coordination between aileron and rudder?

The inclinometer is the part of the turn coordinator that shows the coordination between aileron and rudder. Specifically, the inclinometer is a fluid-filled curved tube that indicates whether the aircraft is in coordinated flight during a turn. When the aircraft is correctly coordinated, the ball inside the inclinometer remains centered. If the ball moves to one side, it indicates that the aircraft is either skidding or pulling too hard on the control surfaces, suggesting improper use of aileron or rudder inputs.

Proper coordination between aileron and rudder is crucial in maintaining balance and preventing adverse yaw during turns. Therefore, the inclinometer allows pilots to assess and adjust their control inputs to ensure a smooth and coordinated turn, leading to improved handling and safety.