What is a balance trim tab?

• A. It is an auxiliary control designed to create aerodynamic forces to assist in moving a control surface; the tab is positioned by a control rod connected to the fixed surface on the same side as the horn on the tab.
• B. It is a device that seals fuel tanks.
• C. It is a device to measure pilot workload.
• D. It is used only on helicopter rotor controls.

Answer: (A)

A balance trim tab is a small secondary control surface attached to the trailing edge of a primary control surface. Its job is to create aerodynamic forces that help move the primary surface, reducing the pilot’s effort required to hold or move that control. The tab is designed so part of it is ahead of the hinge line, and it is driven by a linkage connected to the fixed structure on the same side as the tab’s horn. This arrangement provides a balancing moment that lightens the controllability, especially at launch, high speeds, or when precision is needed.

The other options don’t describe a trim device: one is about sealing fuel tanks, another is a device to measure pilot workload, and the last incorrectly limits trim tabs to helicopter rotor controls.