Primary finding
Probable cause
The fatigue failure of the right landing gear leg that resulted in its separation from the airplane during takeoff.
Investigator assessment
Analysis narrative
The pilot stated that while taking off on a frozen lake with hard-packed snow, the right main landing gear separated from the airplane. He continued the takeoff and landed the airplane without further incident on a snow-covered lake near his home. The airplane sustained substantial damage to the vertical stabilizer due to impact from the right main landing gear. A metallurgical examination of the right main landing gear leg assembly revealed that bilateral fatigue cracks originated from the inner wall of a cross-drilled hole near the right gear leg socket. Eventually, overload and bending stresses in the direction of the fatigue cracks resulted in the right gear leg separating. It was unclear why the hole was drilled. There is an identical hole in the same spot on the left landing gear leg.
Source record
Factual narrative
On February 18, 2023, about 1215 central standard time, a Titan Tornado II, N9168P, was substantially damaged when it was involved in an accident near Windom, Minnesota. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that he departed Cloquet Airport (COQ) near Cloquet, Minnesota, and flew south to Fish Lake, near Windom, Minnesota, to attend an event. After the event was over, he taxied to an area of the lake where the “snow was hardpacked with no bumps, ruts, or [snow] chunks visible” to take off. After reaching rotation speed, the right main landing gear leg sheared off and struck the vertical stabilizer. The pilot was able to control the airplane with aileron and safely became airborne. The pilot flew back to COQ and advised Duluth Air Route Traffic Control Center that he was going to land on Big Lake, Minnesota, about five miles west of COQ, to prevent any further airplane damage from landing on asphalt. During the landing, he applied full left aileron input and touched down on the left main landing gear wheel first and then lowered the nosewheel. The right wing dropped and slid along the ice. He counteracted with left rudder, spun 90° to the right, and came to a full upright stop. Postaccident examination revealed that the airplane sustained substantial damage to the vertical stabilizer from the impact of the right gear leg after it separated from near the fuselage gear leg socket. An examination of the landing gear revealed that bilateral fatigue cracks originated from the inner wall of a cross-drilled hole near the right gear leg socket. Eventually, overload and bending stresses in the direction of the fatigue cracks resulted in the right gear leg separating. There was an identical hole drilled in each landing gear strut. The purpose of the hole is unknown. The pilot stated the hole was covered by a zip tie that was used to secure the brake line.