Cessna A185F N185BB accident near Arlington, Washington

Probable cause

The fatigue fracture of the tailwheel fitting spring, which resulted in the loss of directional control during the landing roll.

NTSB analysis

The flight instructor of a tailwheel airplane was demonstrating a wheel landing to the pilot receiving instruction. The airplane touched down normally on its main landing gear, and, as the tailwheel touched down, the airplane veered to the right. The flight instructor attempted to correct back to the runway, but the airplane continued off the runway and ground looped to the right. The left wing and horizontal stabilizer sustained substantial damage.

Examination of the airplane revealed the tailwheel fitting had separated near the weld gap between the fitting cross tube and the attachment brace. Metallurgical examination of the fracture surfaces identified corrosion pits where the fatigue cracks had initiated. The corrosion pits formed along the outer diameter surface of the tube within the gap against the brace, which created crevice corrosion. As a result of the crevice corrosion, the landing gear failed during the landing rollout, which caused the pilot to lose directional control of the airplane and subsequent ground loop.

Text from the NTSB. Open the NTSB docket for WPR21LA339 for the full record.