Incident Details
During the takeoff roll, approximately 210 feet from the start, the right nose wheel separated from the float. About 35 feet later, the left nose wheel also separated. After the left nose wheel detached, its strut dug into the turf, causing the aircraft to nose over.
Examination Findings
Inspection of the aircraft revealed that the nose wheel struts had separated from the castoring assemblies. The left and right nose wheel struts and castoring assemblies were sent to the National Transportation Safety Board's Materials Laboratory for metallurgical examination.
Visual examination showed that both castoring nose wheels had fractured at the bearing boss welds to the strut arms. Both strut arms were bent upward: the right arm approximately 30 degrees and the left about 5 degrees. The fractures were located through the fusion zones of the strut to bearing boss welds, with some tearing of the boss material at the upper edges of the welds.
Microscopic inspection revealed matte gray textured fracture surfaces, typical of overstress fractures. Deformation and rearward displacement of the boss material adjacent to the upper edge tears and fracture regions, along with smearing contact of the lower fracture areas, were consistent with bending overstress forces on the weld joint.
Service Bulletin
On August 8, 2007, Baumann Floats LLC issued Service Bulletin No. 001. The purpose was "to improve the service and reliability of the nose gear assembly." The bulletin modified the G-129 nose gear tube assembly. Compliance was considered mandatory by the manufacturer upon receipt, and specifically required prior to operating off grass or soft field areas.