Which phrase best describes the function of fins on the AIM-120 control section?

• A. To measure airspeed
• B. To house guidance electronics
• C. To steer the missile in flight
• D. To dampen vibrations

Answer: (C)

Fins act as movable aerodynamic control surfaces that translate guidance commands into steering torque. When the onboard guidance computer determines a change in trajectory, it deflects the fins to create lift and moments about the missile’s center of gravity. This changes the missile’s attitude and path, steering it toward the target during flight.

A speed-sensing function is handled by air data sensors, not the fins. The electronics for guidance live in the guidance section, not in the fins themselves. Damping vibrations can be a side effect of having control surfaces, but the primary purpose of the fins is to steer the missile.