Primary finding
Probable cause
The failure of the right main landing gear weldment due to fatigue cracking.
Investigator assessment
Analysis narrative
After landing, the pilot felt a violent tailwheel shimmy and the airplane veered left. He applied full right rudder and brakes, but the airplane continued to veer toward the left edge of the runway. The right main landing gear collapsed, followed by the left main landing gear, and the airplane departed the runway onto the grass. Postaccident examination found that both of the lower main landing gear weldments had fractured, in addition to the tailwheel attachment link. Metallurgical analysis determined that the lower right landing gear weldment failed on landing due to fatigue cracking that originated at multiple locations on the weld and propagated over time. The remaining fracture surfaces on the right landing gear, left landing gear, and tailwheel link showed overstress, most likely due to the landing sequence. According to the pilot, the weldment made to the right landing gear was not fabricated by the airplane’s kit supplier. It was fabricated about 12 years before the accident flight by a 3rd party welder whom he hired to repair damage from a previous accident. The pilot said that he did not observe any detectable issues with the weldment before the accident.
Source record
Factual narrative
On June 8, 2024, at 1008 eastern daylight time, an experimental amateur-built Titan T-51 airplane, N512JA, sustained substantial damage when it was involved in an accident near Madisonville, Tennessee. The airline transport pilot sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot, who also built the airplane, stated that after he landed at the Monroe County Airport (MNV), Madisonville, Tennessee, he felt a “violent shimmy” from the tailwheel and the airplane began to veer left. He attempted to steer the airplane with full right rudder and brakes, but the right main landing gear collapsed. The airplane began to exit the runway when the left main landing gear collapsed. The airplane came to a rest just off the runway in the grass. The airplane sustained substantial damage to the right wing and fuselage, and all four composite propeller blades sheared from the hub. Postaccident examination of the airplane revealed the welded joints for the left and right main landing gear had failed and the tailwheel attachment link had fractured. The tailwheel link and the fractured weldments were sent to the NTSB Materials Laboratory for further examination. The examination revealed that the right landing gear weldment fractured during landing from fatigue cracking that had initiated at multiple locations on the outer surface of the weld. The fatigue cracking propagated over time through the weld filler to approximately 1.6 inches in circumference. The remainder of the fracture surface exhibited features consistent with overstress. The fracture surfaces of the left landing gear weldment and tailwheel link were both consistent with overstress. According to the pilot, the weldment made to the right landing gear was not fabricated by the airplane’s kit supplier. It was fabricated about 12 years before the accident flight by a 3rd party welder whom he hired to repair damage from a previous accident. The pilot said that he did not observe any detectable issues with the right landing gear weldment before the accident.