Tombarra - Feb 2011

During the investigation into the failure of a fall wire with the loss of one life, two causes were identified: malfunction of proximity switch and the boat being overweight.

The fall wire attached to the rescue boat  parted during a routine drill which was being conducted in the sheltered waters of the Royal Portbury Docks, Bristol, UK. The accident occurred at the point when the rescue boat had been hoisted to its stowed position. The rescue boat and its four crew fell nearly 29m into the water below. One of the boat’s crew died and two were hospitalised.

Hoisting was not stopped before the davit reached its stowed position. The proximity switch, that should have cut electrical power to the winch motor before the davit reached its stops, failed to function

Investigation has also identified that 14 of the 15 foam-filled compartments in Tombarra’s rescue boat had been penetrated by water. In addition, the foam in the lower sections of the hull contained cavities and there were voids between the foam and the hull. Water ingress and retention within the foam-filled internal compartments of the Watercraft WHFRB 6.50 is a serious cause for concern. It is apparent that, without warning, it can result in a boat’s weight increasing considerably over time.
Although the additional weight caused the davit’s SWL to be exceeded, by itself it would not have caused the wire to fail

Download MAIB report on Overweight investigation(2.8MB); 

Tombarra - Overweight rescue boat

 

Download MAIB report on Proximity switch failure: (1.5MB):

Tombarra - Proximity switch failure