Once established in a turn, what does the miniature airplane on the turn coordinator indicate?

The miniature airplane on the turn coordinator indicates the rate of turn. This instrument is specifically designed to help pilots maintain a controlled turn by showing how quickly the aircraft is turning in degrees per second. A proper rate of turn ensures that the aircraft remains coordinated and safely executes the turn without excessive banking or stalling.

A rate of turn indication is crucial during instrument flight, as visual references are often limited or nonexistent. The pilot can use this information to adjust the aircraft's control inputs to maintain a steady and comfortable turn. The miniature airplane will move in relation to a reference line when the aircraft is turning, allowing the pilot to visually assess whether the turn rate is appropriate for the conditions.

While options such as rate of descent or bank angle may be referenced in other contexts or with different instruments, the turn coordinator's primary function is to provide feedback on the rate of turn, ensuring the pilot can achieve the desired maneuver safely and effectively.