Aircraft: Avid Flyer. Injuries: None. Location: Yamhill, Oregon. Aircraft damage: Substantial.
What reportedly happened: The pilot was attempting to land on a private airstrip in his homebuilt, tailwheel-equipped airplane.
The winds were calm and the approach and touchdown were normal, but during the rollout the airplane began an uncommanded turn to the right. The pilot attempted to correct by application of rudder and engine power.
The airplane veered off the runway and into a ditch. During the impact sequence one propeller blade broke, and the left wingtip and a wing rib were broken.
The pilot, who built and maintained the experimental airplane, said the accident could have been prevented had the angle of the tailwheel assembly been correct, noting that after years of use, the tailwheel spring-to-empennage attachment assembly flattened. The incorrect angle altered the tailwheel’s pivot point. This event, combined with the vibration induced during rollout on the gravel runway, allowed the tailwheel to unlock and be in castoring mode at the time of the landing.
Probable cause: The pilot’s loss of directional control during landing rollout due to an unlocked tail wheel that was caused by a degradation of the tailwheel assembly mounting angle.
NTSB Identification: WPR11CA358
This July 2011 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.