Confidential Human Factors
Incident Reporting Programme
The Charity
Aviation
Maritime
M2069
Initial Report
The skipper of a 17m sailing yacht with a draught of 2.5m and a crew of five were on passage in a large sea area. They approach port with charted depths that should have presented no difficulties. However, a chart note stated that the marina entrance was prone to silting and that vessels should proceed with caution, keeping a close eye on the depth sounder.
Sails had been lowered about a mile from the marina entrance, and the engine engaged. The crew used up-to-date paper charts and the pilot book for the area. This warned of reports of shallow spots extending up to 50m from the marina breakwater, and advised giving this a wide berth.
As they approached the entrance, the following sea became more pronounced as the depth decreased. Mindful of the pilot book’s warning, they kept clear of the end of the breakwater, and expected to see the three starboard-hand lateral beacons and four port-hand lateral buoys to guide them in.
They began their turn to starboard, having seen a single set of port and starboard lateral buoys inside the entrance and made a course between them. The depth was being monitored, but reduced quickly, falling below 1m under the keel.
In the belief that this was one of the shallow areas noted on the chart, they continued, but grounded shortly afterwards. The engine was put hard astern, but the swell was driving them further towards the beach. They were able to bring the boat head to sea using the bow thruster, and the anchor was deployed.
Fortunately the vessel re-floated and they were able to motor into the marina, taking a course much closer to the breakwater than that advised by the pilot book but which they had observed in the previous hour being successfully used by vessels of a similar size.
When the boat was lifted out of the water and inspected, nothing more than superficial damage was found to the keel bulb.
The reporter clarified that mistakes had been made by not referring to the chart notes and acting on their information concerning silting at the approaches. The reporter had become too focussed on the advice in the pilot book, which was four years old, regarding the shallow patches extending from the harbour breakwater.
When the depths began to reduce, instead of stopping and going astern, the yacht continued with the approach resulting in the grounding.
The reporter also informed CHIRP that the yacht’s engine was not working at full efficiency due to an, at the time, undiagnosed, broken turbo. While it could propel the yacht at between 6 and 7 knots in calm conditions, there was insufficient power when needed in an emergency.
CHIRP Comment
This report highlights the dangers of using unofficial sources of navigational data. The discrepancy between the actual and expected depth should have been a ‘red flag’ to the crew that they were not necessarily where they thought they were. Although they turned at what they thought was a safe distance, in reality they had turned too soon because they did not see the expected number of lateral bouys. There is evidence of confirmation bias in the report – they felt they were in the right place; and they explained away the rapidly shoaling ground as the ‘shallow patch’. The right answer was to turn around and confirm their position.
CHIRP wants to reinforce the requirement that a fully performing engine on a sailing yacht should be considered an essential safety item, not only for the circumstances experienced at the time of grounding but also for collision avoidance, MOB situations, and executing crash stops in close-quarters cases.
Key Issues relating to this report
Situational awareness- The pilot book was several years out of date and it is likely that it no longer described seabed depths accurately. The expected number of lateral buoys were not visible prior to the course alteration around the breakwater, and although the second entry into the marina was successful this was based largely on guesswork by estimating the route other vessels had followed.
Communications- Contacting the port authorities to ask about the latest seabed changes should have been considered to plan a safer approach to the port. Is this something that you would do if you were approaching a port for the first time?
Local Practices- Although most charts and pilotage books are issued annually, many yacht owners admit to only updating their copies every few years to save on costs. This is a false economy compared to the potential costs of an incident. Similarly, engine maintenance can be costly but could be the difference between an accident and a near-miss.