Accident to the Piper PA18 registered F-HYHB on 07/03/2023 at Biscarrosse

The rupture of the right-hand bracket of the forward float interconnecting strut was initiated by fatigue cracking. The cracking had spread slowly and progressively from the bore hole during in-service use of the assembly. The part finally ruptured when the remaining section of the bracket, not consumed by the cracking, had become insufficient to withstand the applied load, probably during the previous water landing. During the last water landing, the three other mounting brackets experienced ductile failure due to the overload stresses from the sudden deceleration caused by the right, then left, floats moving apart on contact with the water.

The instructor’s analysis that the pilot was having difficulties in controlling the path did not lead him to suspect a fault in the equipment. Neither did the instructor detect the vibration observed by the pilot during the following take-off nor did he decide to interrupt the instruction session and land at Biscarosse aerodrome to check the floats.