A high entry speed and a not fully immersed propeller contributed to a large container ship hitting a gantry crane, resulting in the latter’s collapse. The Nautical Institute describes the incident in a new Mars Report.
The Nautical Institute gathers reports of maritime accidents and near-misses. It then publishes these so-called Mars (Mariners’ Alerting and Reporting Scheme) Reports (anonymously) to prevent other accidents from happening. This is one of these reports.
A large container ship was inbound and a port pilot embarked for docking. Before boarding, the pilot had decided to upgrade the two tugs to be used for more powerful ones because the vessel was in ballast. He did not discuss this or his other docking plans with the master, nor did the master discuss his expectations of the docking with the pilot.
As they entered the inner harbour at about 9.5 knots, the pilot ordered a turn to starboard to bring the vessel parallel with the berths. Starboard 10 was requested, but the vessel turned more slowly than expected. Starboard 20 was requested and soon after hard starboard. When the vessel came parallel with the berths, the wind was now on the starboard side at Beaufort 4-5 and pushing the vessel to port. The vessel’s large freeboard afforded ample windage, so the force to port was considerable.
The pilot soon realised that emergency action was needed as the vessel was approaching the berths with momentum to port at a speed of more than five knots. Tugs and the bow thruster were used to try and slow and turn the vessel, but contact was now inevitable. Emergency manoeuvres and some luck avoided contact with the berthed vessel aft, but the port bow of the
container ship struck a gantry crane on the pier, which quickly collapsed. As the vessel came away from the pier, it struck another berthed vessel forward.
The investigation later established that, at the time of the accident, the propeller had an immersion ratio of about 68 per cent.
Also read: Vessel speed exacerbates bank suction, take two
Advice from The Nautical Institute
- Poor planning and an underestimation of the vessel’s manoeuvring characteristics in ballast were major contributors to this accident.
- Another important factor was the speed of entry, which left no room for error or manoeuvring underperformance, which is to be expected with low draught high freeboard situations.
- Higher speeds also make bow thruster performance negligible and tug assistance more tenuous.
- Not only are the turning characteristics of a rudder negatively affected by being less than fully immersed, the effects of the propeller are also reduced. Carefully consider these effects and discuss with the pilot to arrive at a common plan prior to port entry or exit.
- The pilot upgraded the power of the tugs in attendance prior to boarding the vessel which indicates his concern for the limitations he expected. Notwithstanding these concerns, his docking plan was not discussed with the Master and the ’one man show’ was a catastrophic failure.
Also read: Vessel’s berth contact cuts deep
Mars Reports
This accident was covered in the Mars Reports, originally published as Mars 202534. A selection of the Mars Reports are also published in the SWZ|Maritime magazine. The Nautical Institute compiles these reports to help prevent maritime accidents. That is why they are also published (in full) on SWZ|Maritime’s website.
More reports are needed to keep the scheme interesting and informative. All reports are read only by the Mars coordinator and are treated in the strictest confidence. To submit a report, please use the Mars report form.
