On June 25, 1999, a Cessna 120 (registration N2651N) was involved in an aviation accident near Chino, CA. Investigators recorded the probable cause as: The preexisting multiple-origin fatigue fractures in the right landing gear axle, which led to the wheel detaching during a corrective turn on the runway. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During landing rollout, the aircraft veered left and initiated a corrective turn. The right wheel detached as the axle failed due to preexisting fatigue fractures, causing a ground loop.
What happened
During the landing rollout phase, the airplane began to veer toward the left side of the runway. Pilots attempted to correct this deviation by initiating a turn back toward the centerline. However, during this maneuver, the right main wheel detached from the aircraft. The broken axle dug into the ground surface, leading to a ground loop event where the airplane rotated excessively. The right wing tip subsequently struck the runway surface during the incident.
The investigation
Following the accident, investigators examined the right landing gear axle. Technical analysis revealed that the component had suffered from preexisting multiple-origin fatigue fractures. These structural defects were present prior to the flight and contributed significantly to the sudden failure of the gear during the high-stress maneuver.
Probable cause
The preexisting multiple-origin fatigue fractures in the right landing gear axle, which led to the wheel detaching during a corrective turn on the runway.