Maneuvering the Sally Maersk

purpose is to explicate the control system in order to provide an understanding of thepossible ways of maneuvering the vessel.The steering control system fitted on the Sally Mærsk is a Sperry Adaptive DigitalGyropilot ADG 6000. The system facilitates five different modes of steering:A. Fully automatic. The voyage management system provides the auto pilot withcourse information.B. Auto pilot. The course to be followed is set by a human actor and the auto pilotfollows the given courseC. Follow up. The human actor turns the steering wheel to a rudder setting(rudder angle) and the control system moves the rudder to the desired position.D. Non follow up. The human actor moves the rudder via a direct link to thecylinders turning the rudder. The rudder only moves as long as the switch ispressed to either starboard or port.E. Telephone. An actor on the bridge communicate desired rudder setting viatelephone to an engineer who operates the rudder from the emergency stand.The emergency stand functions according to the principle of non follow up.The five different modes of steering represent different levels of automationavailable within the steering control system. To understand the use objective of thedifferent modes of maneuvering we must distinguish between the objectives ofrobustness and maneuverability. Not all modes have been implemented strictly inorder to provide better opportunities for maneuvering. This is the case for both thetelephone mode and non follow up. There simply is no motivation for these modes ifwe consider them exclusively in terms of maneuvering. They are however perfectlysensible as measures of robustness. The fully automatic mode, the auto pilot, andfollow up mirror the nature of different types of maneuvering while the lower levelsof automation are measures counteracting a total loss of steering if the higher levelsof automation fail. The counter measures to system failure can be traced even furtherto the mountings on the rudder stock allowing it to be turned by chains, and so forth.However, to understand how the actors maneuver the vessel we may concentrateexclusively on the three topmost levels of automation as these are the modes usedduring standard operations.The different modes of steering are performed by use of dedicated devices. In theabove we have already mentioned the vessel management system and the auto pilotbeing two such effectuators. In the below we will deal with these and further controlsubsystems in more detail. We will explain their basic functioning and illustrate howthey serve different types of maneuvering. We will start with the helm stand and theother effectuators that are in use during follow up maneuvering.Follow up steeringWhen operating in open water, say, when crossing the Atlantic Ocean, the vesselfollows the same course for long periods of time. Space is ample and the need forrash course changes seldom occurs. However, the conditions change radically whenoperating closer to a harbor where traffic density is high and the space (restricted bywater depth and traffic regulations) is limited. In the latter case maneuvering is mostoften performed manually, for example, by a helmsman steering the vessel manuallyfrom the helm stand.4