What happened
During the takeoff phase, the pilot of the float-equipped aircraft observed the left float shifting into his peripheral vision, accompanied by a leftward yaw. This was followed by the left wing striking the water, causing the aircraft to nose over. The impact was severe enough to separate the right wing from the fuselage. Passengers on board noted choppy ocean conditions with visible whitecaps and reported that the aircraft struck a significant swell or wave, which triggered the sudden nose-over and caused the cabin to fill rapidly with water.
Findings
An inspection of the float assembly identified several structural failures. Specifically, there were fractures in the left front flying wire attachment fitting and the right rear flying wire attachment strap, along with hole elongation in the left rear flying wire attachment fitting. The bolts connecting the left flying wire attachment fittings to the left float were bent, and the associated flying wires were buckled.
While minor corrosion was present on the fractured left forward fitting, it was not significant enough to compromise the structural integrity below the design specification. Testing by the manufacturer demonstrated that the observed buckling of flying wires only occurs at loads exceeding 9,000 pounds of force, which is far above the design specification of 3,453 pounds of force. Consequently, the investigation concluded that the impact with an ocean wave or swell subjected the floats to forces exceeding their design limitations, causing the structural failure of the flying wire components.