The Safety Investigation Authority (Otkes) has published a report into the sinking of a Border Guard vessel last June that left one crew member dead.
Border Guard patrol boat PV 83 sank off the coast of Loviisa after running aground on 20 June last year.
Two members of the three-man crew escaped, but the boat's helmsman died after being trapped inside the cabin.
The Otkes' report highlighted flaws with the 10-metre boat, which was not originally designed or equipped for use as a patrol vessel.
The safety authority recommended that the Border Guard change crew navigation training and draw up guidelines on rescuing people from inside sunken vessels. It also recommended that transport agency Traficom communicate the dangers of water leaks to boaters.
How it happened: PV 83's sinking
According to safety investigators, PV 83 left the shipping channel before it ran aground as the crew returned to take a break aboard a larger ship, the Turva.
After contact with the seabed, water flooded into the hull through a 1.5-metre rupture at a rate of 300 litres per second.
Within six minutes, the aft deck was completely submerged and the water was approaching the open doorway at the back of the boat's cabin.
Shortly afterward, water flooded through the doorway, filling the cabin. At this point PV 83 turned on its end and sank, with only the tip of the bow remaining above water.
Navigation of PV 83 was largely done by means of a digital map, the report said, the accuracy of which depends on the scale used.
The situation was made worse by the inability of the crew to use paper charts, due to a lack of available space in the cabin.
"The large amount of equipment required for patrol duties made the cabin cramped. The helmsman’s visibility outside was limited and using paper charts was difficult without a chart table," the report said.
At the time PV 83 ran aground, the helmsman was responsible for both navigating and steering the boat, a deviation from standard practice the crew made as they believed the area was safe and familiar.
"Navigating and steering a fast boat alone is especially stressful, and therefore the active participation of several people is required to ensure the safety of navigation. The organisation must ensure that the correct operating model is followed," Otkes said.
The crew initially focused on rescuing equipment from the stricken vessel as the rate of sinking seemed slow at first, Otkes said.
"At the time of the accident the crew were aware of the danger of the boat sinking, but not of its severity. They began to evacuate tools from the boat," said Otkes Investigation Director Risto Haimila.
"Such a severely dangerous situation requires prioritising the protection of human lives regardless of material losses," the safety investigation agency's report said.
A fatal flaw
However, the design of PV 83 was what proved to be fatal, the report said.
"In practice, the cab of the patrol boat had only one emergency exit - the door on the back wall of the cabin," Otkes found.
"It suddenly sank under water when the bow of the boat rose as a result of the water that rushed in rapidly through the door. The two skylights in the ceiling of the cabin did not meet the requirements for an emergency exit," the report said.
Rescue efforts to free the helmsman trapped in the cabin were hampered by the submerged exit and the size of the skylights, which were too small to exit through while wearing a lifejacket.
Divers from Turva arrived on scene 45 minutes after PV 83 sank, in part because the need for divers "was not immediately identified," said the report.
The helmsman was taken to hospital, where he was pronounced dead.
"The situation developed suddenly, so in practice, it became impossible for the crew member who remained in the cabin in an immersion suit to leave the sinking boat," Haimila said.
"The boat involved in the accident was designed as an auxiliary boat of VL Turva, but in practice, it was used for patrol duties. The intended purpose of the boat was different, and the PV 83 was not designed or equipped for such long-term patrol duties,” said Professor Veli-Pekka Nurmi, Otkes' executive director.