ERA18LA258 · Beech 35 V35

While approaching the airport for landing during an instructional flight, the airplane entered an uncommanded yaw and roll to the right and began to pitch up. The flight instructor was able to maintain some control of the airplane by applying left rudder, left aileron, and forward elevator pressure, and trimming the airplane nose-down. The instructor noticed that the airplane’s right yaw increased as the airplane's speed decreased, and it became "impossible" to maintain alignment with the runway centerline. Upon touching down on the runway, the airplane immediately veered to the right about 90° and collided with trees, resulting in substantial damage to the firewall, fuselage, and both wings. Examination of the flight control system revealed that the left seat’s left rudder pedal arm clevis was fractured in multiple sections. Metallurgical examination identified cracks and voids created during the casting (manufacturing) process. The presence of these voids, cracks, and oxide layers reduced the cross-sectional area that could withstand the force applied over the pedal arm clevises. Once a high enough load input was applied to the pedal arm, the remaining material fractured in overstress. The separation of the pedal arm from the pushrod subsequently resulted in a failure of the rudder control system. Review of the airframe logbooks revealed that the rudder pedal arm was original to the airplane and had accrued a total of 6,203.62 flight hours.

Verbatim NTSB analysis and probable cause from the NTSB dataset