In its latest Safety Digest, UK MAIB analyzed a collision between two rigid-hulled inflatable boats, after a windsurfing race, which caused four people to fall overboard. According to MAIB, overconfidence on the boats’ handling was critical to the accident, while the fact that everyone was wearing life-saving equipment was vital to prevent loss of life.
The incident
A military sail training centre was hosting a windsurfing event. Three officer cadets were then tasked to helm three RHIBs as support boats for the racing. After the racing had finished, all three RHIBs were heading back to the sailing centre. There were 10 officer cadets in the three boats, all wearing buoyancy aids and the helms had their kill cords attached. Although the sea was calm, there was a swell from the south-east of about 1.5m and 15kts of wind from the south-west. The three RHIBs (A, B and C) headed home in a line about 400m apart at a speed of about 30kts.
On the way towards the harbour entrance, the helm of the lead boat noticed that a paddle had come loose, so slowed down to sort it out; this significantly reduced the distance between boats A and B. As the events had finished earlier than planned, there was spare time available for planing practice, so when boat A reached the pole, the helm decided to turn to starboard into the swell, rather than turn to port into the harbour.
Boat A’s manoeuvre brought it directly into the path of boat B, which was still planing at full speed. When the helm of boat B realised what had happened, it was too late to avoid collision, so he pulled the kill cord to stop the engine. Boat B struck boat A violently on its starboard side then rode right over boat A into the sea beyond. As such, all of boat A’s four crew were thrown into the water and three were injured, one seriously.
The helm of boat B made a “Mayday” call on VHF and its crew recovered boat A’s crew members. All boats then headed back towards the harbour, where they met at harbour entrance the harbourmaster’s launch and the local lifeboat that had responded to the “Mayday”. The boats then headed to a nearby marina, where an ambulance was waiting; the casualties were attended by the ambulance paramedic and then transferred to the nearest hospital for further assessment.
Lessons learned
- When the collision happened, everyone who was thrown overboard was wearing a buoyancy aid and both boats’ helmsmen were wearing their kill cords. These actions probably prevented loss of life. Had the kill cords not been connected, at least one – maybe both – boats would have continued underway and out of control, presenting a serious threat to those in the water. Cold water immersion can lead to a shock response and rapid loss of muscle function with risk of drowning. Wearing a lifejacket or buoyancy aid greatly assists casualties in this situation, keeping them at the surface until rescued.
- Prior to collision, the RHIBs were planing at high speed and in company on the open sea. The RYA powerboat level 2 course focuses on low speed boat handling with only an introduction to planing speeds. Although operating as event support boats was intended to consolidate their training, the cadet helms’ operation of their boats went well beyond their taught skill level or experience and resulted in the serious risk of collision. This could have been prevented by a higher level of supervision from the sailing centre’s staff and clearer direction about how the boats were to be handled and operated.
- Whatever the size of vessel or the task, every passage needs a plan. Although it had not been discussed, the plan on this occasion was to return to the sailing centre; a route taken by all the boats several times over the preceding days. The decision by the helm of boat A to turn to starboard at the navigation pole was a deviation from this route. The helm of boat A did not communicate his intentions beforehand and the manoeuvre placed boat A directly in the path of boat B. The close proximity of boat B prevented its helm from taking effective avoiding action. To minimise the risk of collision, high speed planing in company requires absolute clarity of the plan, a ‘shared mental model’ and good communications to maintain situational awareness and understand other boats’ intentions.
- Although a VHF “Mayday” was called, the boats were fitted with digital selective calling (DSC) radios and the distress button function could have been used to raise the alarm. The key benefit of using the DSC distress function is that the coastguard will automatically receive the casualty vessel’s position. In this case, the boats were so close to shore that the casualties were probably transferred to hospital by the fastest means.
