Aerodynamic assistance to control surfaces is provided by which device?

• A. Transponder Mode A
• B. Spring tab
• C. Probes and sensors (Permanent)
• D. Main and Emergency Battery

Answer: (B)

Spring tab provides aerodynamic assistance to control surfaces by using a small auxiliary surface on the trailing edge that deflects with the control input. As the pilot moves the control, the spring tab deflects in a way that, through the airflow, creates a force on the tab itself. This aerodynamic force then helps move the larger primary control surface, reducing the amount of effort the pilot must apply to achieve the desired deflection. This is especially useful on large aircraft or at high speeds where control forces can be heavy.

The other options serve different roles: a transponder responds to air traffic control codes, probes and sensors measure flight parameters, and the main and emergency battery supply electrical power.