ERA18LA258

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.

On September 22, 2018, about 1515 eastern daylight time, a Beech V35 airplane, N435RB, was substantially damaged when it was involved in an accident near Georgetown, South Carolina. The flight instructor and the private pilot sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. The flight instructor stated that he was providing instruction to the pilot for a complex/high performance endorsement. They flew for about 30 minutes before returning to the airport, and the flight instructor took control of the airplane so the pilot could get a drink of water. During that time, the airplane entered an uncommanded yaw and roll to the right and started to pitch up, and the instructor confirmed with the pilot that he was not touching the controls. The instructor was able to maintain some control of the airplane by applying left rudder, left aileron, and forward elevator pressure. He also trimmed the elevator nose down, which helped relieve some of the airplane’s right-turning tendency. As he prepared to land on runway 11, the instructor noticed that the right yaw increased as the airplane's speed decreased. As the airplane slowed down to 80 mph, it became "impossible" to maintain alignment with the runway centerline and the airplane began to drift to the right. Once the airplane touched down, it immediately veered to the right about 90° and collided with trees, resulting in substantial damage to the firewall, fuselage, and both wings. Postaccident examination of the flight control system revealed that the left seat’s left rudder pedal arm clevis was fractured in multiple locations. Metallurgical examination of the fractured pieces 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, installed at the time of manufacture in 1966. At the time of the accident, the airplane had accrued a total of 6,203.62 flight hours.