Primary finding
Probable cause
The pilot’s failure to maintain directional control during the landing roll with an unexpected windshift, which resulted in a runway excursion.
Investigator assessment
Analysis narrative
The pilot reported that during his landing roll the airplane encountered an unexpected wind shift with quartering tailwind gusts as he decelerated to about 45 miles per hour. The pilot had not yet retracted his flaps and lost directional control of the airplane. The airplane departed the left side of the runway, traversed through the grass, and came to rest in a swale, resulting in substantial damage to the fuselage and engine mount. The pilot did not report any mechanical malfunctions or failures with the airplane that would have precluded normal operation.