The Marine Accident Investigation Branch (MAIB) has published a report into the investigation of the listing, flooding and grounding of the car and truck carrier Hoegh Osaka on the Bramble Bank in the Solent on 3 January last year.
Accompanying the report, a safety flyer has been produced highlighting key safety lessons arising from the accident which the Chief Inspector of Marine Accidents urges the industry to take forward.
Stability modelling and analysis following the accident show that Hoegh Osaka heeled heavily to starboard while turning as a result of having departed port with inadequate stability. Cargo distribution was such that the upper vehicle decks were full while the lower vehicle decks were lightly loaded. Hoegh Osaka was low on bunker fuel oil, which was stored low down in the ship, and the ship’s overall vertical centre of gravity (VCG) was relatively high. Hoegh Osaka’s inadequate stability had not been identified prior to departure. The figures in the pre-stowage plan were significantly different to the final cargo tally; the estimated weight of many items of cargo was less than their actual weight; and no allowance was made for the VCG of the cargo loaded being above deck level. Finally, it was onboard practice to alter the ballast tank quantity readings on the loading computer so its output would match the observed draught readings. It would have been possible to embark additional ballast prior to departure to reduce the ship’s VCG as necessary, but as the shortcoming in stability had not been identified this was not done.
The MAIB’s investigation found that Hoegh Osaka’s stability did not meet the minimum international requirements for ships proceeding to sea. The cargo loading plan had not been adjusted for a change to the ship’s usual journey pattern and the number of vehicles due to be loaded according to the pre stowage plan was significantly different from than that of the final tally. The estimated weight of cargo was also less than the actual weight. Crucially, the assumed distribution of ballast on board, bore no resemblance to reality, which resulted in the ship leaving Southampton with a higher centre of gravity than normal.