Aug 202011

Fatigue or sleep inertia?

Sleep and fatigue are familiar tropes on MAC posts and two recently released reports from the UK’s Marine Accident Investigation Branch highlight two issues, one familiar, the other less so – stress, fatigue and sleep inertia.

In the case of the FV Jack  Abry II grounding on the Isle of Rum, 31 January 2011, the skipper, who had been alone on watch in the wheelhouse, fell asleep and failed to make a course alteration. He had joined the vessel in Lochinver on the day of the accident after travelling from his home in France. It is likely the skipper became fatigued through a combination of personal stress, a prolonged period without sleep and poor quality rest before leaving his home, much of it possibly connected to domestic issues.

The wheelhouse watch alarm was not used, nor was best use made of the available navigational aids and crew.

Fatigue is not just lack of sleep and heightened stress levels. The brain has a rhythm of alertness, a circadian rhythm, which can increase the effect of fatigue. Taken together these effects do not just increase the chances of falling asleep but also increase the chances of bad decision-making. In the case of FV Jack  Abry II, the skipper did not take advantage of appropriately trained crew onboard to provide additional lookout duties.

Most of us know we are under personal stress or have slept badly yet somehow feel it unmanly, or unprofessional, to recognise it and we try to bull through it. Learning to recognise when we ourselves have become a potential hazard to the vessel and its crew is part of being professional.

In the second case, PSV Skandi Foula, a chief officer had plenty of sleep, was called to the bridge and subsequently made heavy contact with the moored Panamanian registered supply vessel OMS Resolution in Victoria Dock, Aberdeen. He was new to the vessel and the controls were unfamiliar to him. The MAIB report suggests ‘sleep inertia’ as a contributing factor.

Sleep inertia is something most of us are familiar with. When we switch on a computer it takes a while for it to become usable and we are the same. Waking up is not like switching on a light, it takes a few minutes for us to become fully alert. On Skandi Foula the chief officer was woken up and on the bridge within about 15 minutes. Almost certainly he was not yet fully awake.

As with most accidents there were other contributory causes for the accidents.


Download FV Jack  Abry II report
Download Skandi Foula report



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