Incident Overview
A pilot reported that during the landing roll, a 'rumbling noise' was heard. When the pilot applied the brakes, the airplane pulled slightly to the left. The pilot pulled back on the elevator but was unable to prevent the airplane from nosing down and flipping inverted.
Post-Accident Inspection
After the accident, inspection revealed that the front wheel on the left float had separated from the airplane. The wheel attachment bracket then dug into the sod airstrip, which resulted in the airplane nosing over.
Metallurgical Examination
Metallurgical examination of the left caster axis bolt showed that it had failed due to a fatigue fracture. This failure likely allowed the wheel to separate, leading to the nose-over.