Six on/six off equals fatigue

摘要

A small cargo vessel was on a coastal passage and proceeding at full sea speed. At midnight, the master, one of the two watch-keepers on board, was relieved by the other officer. Soon after taking over, the officer on watch (OOW), as was common practice, sent the duty lookout below. It was later determined that the OOW fell asleep some time after sending the lookout below. With the bridge navigational watch alarm system (BNWAS) turned off and other alarms not activated, available bridge resources that could have alerted the crew and/ or awoken a sleeping OOW were silenced. As a result the vessel steamed at 11.5kt with no-one in control on the bridge for more than an hour before grounding.