Pitch astern when transferring control; mooring requirements

摘要

An anchor-handling tug/supply (AHTS) vessel moved into a stern-to position in order to conduct bulk operations with a mobile offshore drilling unit (MODU). After driving the vessel in manual, the master applied 25 per cent astern pitch to take off the forward motion, the pitch selector was moved to 0 and control passed to aft, in order to set up dynamic positioning (DP). The aft position took control before the pitch had fully returned to zero. The dynamic positioning officer (DPO) did not notice that pitch had been set where it was when control was taken - that is, 25 per cent astern. Unable to take control of the controllable pitch propellers (CPP), and unable to apply forward thrust, attempts were made to reset the system by passing control. Control of the CPP was only regained once emergency mode was selected.