FAA Aviation Mechanic Airframe (AMA)Airframe StructuresMedium
A technician is inspecting an aileron trim system and finds a small auxiliary surface hinged to the trailing edge of the aileron that is mechanically linked to the fixed wing structure so that it automatically deflects opposite to the aileron's movement, reducing pilot control force without being directly controlled by the pilot. What is this type of tab called?
- ABalance tab
- BSpring tab
- CServo tab
- DTrim tab
Show answer & explanationAnswer & explanation
Correct answer: A. Balance tab
A balance tab is linked to the fixed structure so it automatically moves in the opposite direction to the control surface, creating an aerodynamic force that helps move the surface and reduces pilot control force. Unlike a servo tab, it is not directly moved by the pilot's cockpit control; unlike a trim tab, it is not adjusted independently to trim out control forces at a given flight condition.
Why the other options are wrong
- B. A spring tab uses a spring linkage to assist control force at higher speeds, differing from the fixed-structure linkage of a balance tab.
- C. A servo tab is directly controlled by the pilot and moves the main surface via aerodynamic force, rather than moving automatically opposite to the surface.
- D. A trim tab is independently adjustable by the pilot to relieve steady-state control forces, not automatically linked to fixed structure.
Balance Tab
A control surface tab linked to the fixed airframe structure that automatically deflects opposite to the primary control surface, reducing the pilot's required control force.
- Linked to fixed structure, not the cockpit control
- Moves automatically opposite the control surface
- Reduces pilot control force aerodynamically
Memory trick: Balance tab is 'tied to the wing' — it swings opposite automatically to balance the load