The trim tab on a control surface is used to balance what?

• A. Balance of control forces
• B. Increase lift
• C. Decrease drag
• D. Improve fuel efficiency

Answer: (A)

Trim tabs balance the forces on a control surface so the aircraft can stay in a chosen attitude without the pilot having to hold constant pressure. By moving the tab, a small aerodynamic force is produced that counteracts the hinge moment of the main surface. This offsets the control surface’s tendency to move due to airflow, making it easier to hold a desired position and maintain steady flight.

In other words, the tab’s job is to reduce the amount of stick force needed by the pilot by balancing the control forces. It’s not primarily about increasing lift, decreasing drag, or directly improving fuel efficiency—those effects may occur as a side result, but they aren’t the primary purpose.