Which statement best describes a balance trim tab?

• A. An auxiliary control that reduces drag on a surface.
• B. A device used to measure airspeed.
• C. It creates aerodynamic forces to assist in moving a control surface and is positioned by a control rod on the same side as the tab horn.
• D. A primary flight control used for roll.

Answer: (C)

A balance trim tab works by creating aerodynamic forces that assist in moving a primary control surface, reducing the pilot’s effort to hold or move that surface. The tab is a small movable surface attached to the main control surface and is actuated by a control linkage that is on the same side as the tab horn, so its movement helps balance the loads on the surface. This is exactly how trim is achieved: a tiny aerodynamic push or pull from the tab makes it easier for the main surface to deflect to the desired position.

The other ideas don’t fit because a trim tab isn’t primarily about reducing drag, it isn’t a device for measuring airspeed, and trimming isn’t the same as a primary control used for roll (that role belongs to the ailerons).