The trim continues to move in the same direction despite attempts to stop it with control inputs.

• A. Elevator System Jammed
• B. Rudder System Jammed
• C. Stabilizer Trim Runaway
• D. Unreliable Airspeed

Answer: (C)

This describes a stabilizer trim runaway. When the stabilizer trim keeps moving in the same direction no matter what you do with the controls, the trim system is failing and driving the stabilizer by itself. That behavior is distinct from an elevator or rudder jam, which would lock movement rather than cause continuous motion, and it isn’t explained by unreliable airspeed. The usual corrective action is to cut power to the trim (trim-cutout) and, if needed, disconnect the autopilot to regain manual control and stabilize the airplane.