Cessna 120 N3124N accident near Lone Pine, California

Probable cause

The fracture of the left main landing gear (MLG) wheel axle due to fatigue, which resulted in the separation of the left MLG wheel during takeoff from a dirt airstrip.

NTSB analysis

The private pilot was taking off from a dirt airstrip for a personal cross-country flight. He reported that, during the takeoff roll, it felt like the left main landing gear had hit soft soil and that the drag had increased. He attempted to correct for the condition, but the left MLG wheel continued to drag. The airplane then suddenly nosed over, which resulted in substantial damage to the wings and empennage.

Postaccident examination of the airplane revealed that the left MLG wheel axle was fractured, which resulted in the separation of the left MLG wheel. A detailed examination of the fracture surface identified a fatigue fracture that emanated from the outer surface of a circumferential weld between the lateral tube portion and the vertical plate portion of the axle. The investigation could not determine what event initiated the fatigue cracking; however, the origin areas were covered in zinc-chromate primer, which indicates that the axle was painted when the circumferential weld contained a preexisting crack.

Text from the NTSB. Open the NTSB docket for WPR16LA018 for the full record.