Stabilizer trim continues to move by itself toward nose-up indefinitely, ignoring pilot input.

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

Answer: (C)

Runaway stabilizer trim is when the horizontal stabilizer trim moves on its own and continues in one direction despite pilot input. In this scenario, the trim keeps driving toward nose-up without responding to the pilot, which is the hallmark of a fault in the trim system causing uncommanded, sustained movement.

This is the best match because the symptom is uncommanded, continuous movement of the stabilizer in a single direction. The other faults describe surfaces or systems that would either jam and stop moving or affect other controls or indications, not cause the trim to keep moving by itself toward nose-up regardless of inputs.