Accident Overview
On May 30, 2024, at about 1610 mountain daylight time, an amateur-built experimental Kitfox, registration N506F, sustained substantial damage in an accident near Parowan, Utah. The pilot, who was the sole occupant, was not injured. The flight was conducted under Title 14 Code of Federal Regulations Part 91 as a personal cross-country repositioning flight.
Pilot Report
The pilot, who had recently acquired the tailwheel-equipped airplane, reported feeling a shimmy during takeoff. He subsequently performed a three-point landing on runway 22 at Parowan Airport (1L9). Immediately upon touchdown, the airplane "unexplainably and severely turned left, departed the runway, and ground looped," according to the pilot. The right main landing gear collapsed, causing substantial damage to the right wing. The pilot noted that the wind was light and variable with no gusts at the time of landing.
Tailwheel Assembly Findings
The airplane was fitted with a Matco 11-inch dual fork tailwheel assembly. Postaccident photographs provided by the pilot showed the assembly partially displaced to the left side of the airplane, with the tailwheel deflected to the right. Further photographs of the removed assembly revealed damage and fractures on the fitting flanges of the extruded base on both sides. An NTSB structures engineer reviewed the images and determined that the damage resulted from a twisting motion about the single bolt securing the assembly to the suspension. The mode of fracture could not be determined from photographs, but deformation suggested shear overload consistent with a tailwheel shimmy event. Under normal operation, the tailwheel is designed to caster about the vertical axle without rotation about the attachment bolt. The investigation could not determine whether a loose attachment bolt caused the shimmy or if the shimmy caused movement around the bolt.
Additional Information
The pilot examined the airplane's brakes and found no anomalies. A full examination of the tailwheel assembly was not conducted. The most recent condition inspection was performed on October 28, 2023, but no specific details about pre-accident maintenance or inspection of the tailwheel were provided.