What happened
During a takeoff run from a fishing camp at Bradburn Lake, Manitoba, a Beech 18 seaplane experienced a significant leftward yaw. The pilot attempted to correct the deviation using rudders and differential engine power, but the yaw worsened as the aircraft reached approximately 60 mph. During this sequence, the left float detached from the airframe, causing the left wing to strike the water. The aircraft turned sharply and capsized in roughly 15 feet of water.
The pilot and six passengers successfully exited the sinking aircraft through an overhead hatch and swam to the nearby shore. While the aircraft and the passengers' baggage sustained substantial damage, there were no injuries among the seven people on board.
The investigation
Investigators examined the wreckage and the float attachment hardware. The examination of the front swivel fitting and mounting pad revealed that the attaching bolt had likely moved out of position. This movement was attributed to the securing nut either being absent or having detached during service. The investigation also noted that several other float bolts were secured with fibre self-locking nuts rather than the specified castellated nuts and cotter pins, and some bolts did not extend fully through the nuts.
Further review of maintenance protocols showed that the operator's approved inspection program did not incorporate the more rigorous inspection requirements specified in the Bristol Float Service Manual. While the manufacturer recommended removing the floats for inspection every 500 hours or at the end of each season, the operator's program only required checks for cracks and security every 100 hours.
Findings
- The primary cause of the accident was the departure of the left front swivel fitting attachment bolt from its position, which triggered a chain of structural failures.
- The bolt likely moved because the securing nut was either not installed or fell off during operation.
- The aircraft's low-wing design and float configuration made it difficult to detect defects in the forward float fittings during routine walkarounds.
- The operator's inspection schedule lacked the specific requirements mandated by the float manufacturer.
- The pilot's pre-takeoff briefing and actions during the sinking contributed to the successful evacuation of all passengers.