At 1549 on 7 February 2011, the rescue boat on board the UK registered car carrier, Tombarra, plummeted approximately 29m from its davit into the water below, killing one of the rescue boat’s four crew. The accident occurred when the boat’s fall wire parted as the boat was being recovered to its stowage during a monthly drill. Tombarra was alongside Royal Portbury Dock, Bristol.
The rescue boat’s fall wire failed because an electronic proximity switch, which was intended to stop power to the winch motor as the rescue boat davit neared its stowed position, did not operate. As a result, the rescue boat was hoisted fully home into its davit and the fall wire became overstressed by the davit winch, which was fitted with a 15/20kW electric motor.
The investigation has identified a number of factors that contributed to the accident, including:
- The proximity switch that failed to operate was not fitted in accordance with its manufacturer’s instructions, and was not suitable to be used as a ‘final stop’ device in man-lifting equipment.
- The functionality of the proximity switch was not tested immediately before the rescue boat’s recovery.
- Although the davit system manufacturer intended that the winch motor be stopped by its operator before the proximity switch was activated, the manufacturer’s guidance was misleading.
- The winch motor was able to easily and rapidly overstress the fall wire.
Although the International Maritime Organization recommends that all davit system designs are checked to ensure the compatibility of component parts, the Life Saving Appliance (LSA) Code accepts that overstressing of components could occur, but requires that this is prevented by the use of safety devices. However, the Code does not specify any standard to which such safety devices must conform or the number of safety devices that must be fitted to davit systems.
During the investigation, it was also found that the rescue boat was significantly overweight. This did not contribute substantially to the failure of the fall wire on this occasion, but the increase in the weight of the boat while in service is a cause for concern.
The weight growth found on Tombarra’s rescue boat had been caused by the ingress and retention of water in the hull’s internal stiffeners, which were hollow, and in segregated spaces containing buoyancy foam within the boat’s hull. The water could not be drained from these spaces and the crew had no way of knowing the water was there. The foam used in the buoyancy chambers was of varying quality and contained voids in which water was able to collect. Inspection and testing of other WHFRB 6.50 rescue boats, along with reports of inspections of other rescue boat models, indicates that there is considerable scope for many rescue boats and lifeboats to be overweight due to water retention.
During this investigation, it was apparent that the problem of water ingress and retention in rescue boats and lifeboats using buoyancy foam is known by many of the interested parties within the shipping industry. There is general recognition that boats will not remain watertight and their weight will increase over time as the accumulated water cannot be drained. An increase in weight can not only adversely affect a rescue boat’s ability to meet international requirements, but it can also compromise the safety of its launching and recovery equipment.
Regarding measures to prevent similar accident the IMO has released the following circulars
- MSC circular 1094 Application of SOLAS Regulation III/26
- MSC Circular.1206/Revision.1 Measures to prevent accidents with lifeboats
The MAIB reports regarding the rescue boat accident can be found in the following links:
Additionally due to the seriousness of the accident MAIB has also released a “Safety Flyer” related to the incident: