During a turn, the rudder does not deflect and yaw rate remains zero.

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

Answer: (B)

The key idea is that yawing motion in a turn is generated by the rudder. If, during a turn, the rudder does not move and the yaw rate stays at zero, the most likely fault is that the rudder system is jammed. With the rudder locked, you can’t create the required yaw moment to steer or coordinate the turn, so the airplane remains effectively un-yawed despite rudder commands.

If the elevator were jammed, you’d expect pitch control issues rather than a lack of yaw. A stabilizer trim runaway would cause the trim to move on its own, altering nose position rather than preventing rudder movement. Unreliable airspeed affects speed indications, not the ability to deflect the rudder.