Incident Overview
While a student pilot was landing on runway 11, approximately 5 feet above the runway, a gust of wind lifted the right wing. The left main landing gear touched down, causing the gear spring to twist. The airplane began to drift left. After allowing the student a couple of seconds to recover, the certified flight instructor (CFI) took control. The airplane continued to veer and departed the left side of the runway, where the left main landing gear collapsed. The airplane came to rest on a grass area. The left main landing gear spring was retained for examination.
Examination Findings
According to the manufacturer's technical report, the tubular spring for the left main landing gear fractured at the inboard end. The inboard end contained a longitudinal oriented fracture that intersected a fastener hole. The fracture face exhibited chevron marks typical of an overstress fracture, pointing back to the hole, indicating the fracture originated from the fastener hole. No evidence of corrosion was noted on the fracture region. Further examination revealed machining marks and fretting within the fastener hole.
Maintenance History
Review of the airplane's maintenance records showed that the landing gear struts were removed and floats were installed in 1992. After approximately 2,158 hours of service, the floats were removed and the original landing gear struts were reinstalled. At the time of the incident, the airplane had accumulated about 3,598 total service hours.
Wind Conditions
The CFI reported that winds at the airport around the time of the incident were from 180 degrees at 8 knots, gusting to 17 knots.