During flight, the aircraft cannot produce any yaw change despite full rudder pedal application.

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

Answer: (B)

The key idea is that yaw is controlled by the rudder. The rudder is the movable surface at the tail that deflects air to push the aircraft left or right, producing rotation about the vertical axis. If the rudder system is jammed, the rudder cannot move even when you push the pedals to full travel, so there will be no yaw change despite maximum pedal input.

Other failures don’t fit because they affect different control axes. An elevator jammed would lock the elevator and degrade pitch control, not yaw. A stabilizer trim runaway changes the horizontal stabilizer position, which mainly alters pitch trim rather than preventing yaw movement. Unreliable airspeed affects the aircraft’s speed indicators and performance, not the ability to deflect the rudder or produce yaw.