Accident Overview
On September 8, 2021, at about 1130 Pacific daylight time, a Cessna A185F (registration N185BB) was substantially damaged during a landing accident near Arlington, Washington. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. The flight instructor, pilot receiving instruction, and passenger were not injured.
Sequence of Events
According to the flight instructor, the pilot receiving instruction had performed several landings before the instructor assumed control of the tailwheel airplane to demonstrate a wheel landing. During the landing roll on runway 16, after the tailwheel touched down, the airplane veered to the right. The instructor attempted to correct with brake and rudder, but the airplane exited the right side of the runway and ground looped to the right. The left wing and horizontal stabilizer struck the surface.
Postaccident Findings
Postaccident examination revealed that the tailwheel fitting spring attachment was partially fractured and had rotated approximately 90° from its normal position. The tailwheel fitting spring attachment was sent to the National Transportation Safety Board Materials Laboratory for examination.
Laboratory Examination
Examination of the fracture surface showed fatigue cracking that initiated at the fillet weld gap between the fitting cross tube and the attachment brace. The fatigue cracks initiated at corrosion pits that had formed along the outer diameter surface of the tube within the gap against the brace. These characteristics were consistent with crevice corrosion.
Maintenance Records Review
A review of the airplane’s maintenance records indicated that, about one month before the accident flight, the tailwheel fitting spring attachment was removed, and new bushings and washers were installed. The tailwheel fitting spring was then reinstalled with new hardware. The age of the tailwheel fitting spring attachment could not be determined.