Ryan NAVION N27AW accident near Chicago, Illinois

Probable cause

The failure of the left main landing gear upper side brace assembly during landing due to reverse bending fatigue as a result of the incomplete penetration of the circumferential weld during initial production of the component.

NTSB analysis

The pilot reported that as the airplane touched down on the dry concrete runway, he heard a "snap" noise but that the landing was "smooth and normal." He taxied the entire length of the runway for the rollout but then had difficulty taxiing the airplane straight. The pilot thought that he had a flat tire until he exited the airplane and saw that the left main landing gear had failed.

A postaccident examination revealed the left main landing gear upper side brace assembly fractured due to reverse bending fatigue at the circumferential weld between the middle tube and the fork at the inboard end of the assembly. The fatigue initiated from the tip of the weld in areas of incomplete weld penetration. The weld was performed during initial production of the component. The fatigue cracks extended radially outward from the interior surface of the tube, but the fatigue region did not intersect the outer surface. Thus, the cracks likely would not have been detected by visual inspection. The failure of the weld resulted in the displacement of the left main landing gear strut outboard toward the wingtip, which caused substantial damage to the underside of the left wing.

Text from the NTSB. Open the NTSB docket for CEN19LA251 for the full record.