Ship manoeuvring controls

Ship manoeuvring control
Ship manoeuvring control

A bridge is not only for navigation but is also the command and control centre of the ship. As such it must have a comprehensive control system that connects to the engine and steering gear as well as other systems on the ship such as the navigation lights. On a modern ship this is achieved by a combination of hydraulic, mechanical, electronic and electrical means and a system of indicators that returns information to those controlling the ship.

The controls of the various systems are often supplied by the bridge manufacturer for an integrated system or they can come from an independent third party. Operation of the controls will vary and in many ships the once-familiar system of wheel, knobs and levers has been replaced by a combination of joysticks and touch screens.

In 2010, Kvant introduced a haptonomic module that can be used with its controls to give a positive feedback to the operator. This gives back some of the ‘feel’ that was inherent in older methods of control and allows the navigator to better understand what is happening at the rudder or propulsor. Although this may seem to be an unnecessary gimmick, since the navigator has the readout display in clear sight, it has been shown to prevent excessive use of the control and thus eliminate the hazards and undesirable effects of systems being overloaded.

The layout of the ship’s controls is considered to be part of the ergonomics of the bridge and placement will take into account the position from which they are normally operated. On some ferries and offshore vessels, the controls may even be partially incorporated in to the captain’s chair.

The physical controls are normally sufficient for general use but emergencies do arise and all vessels are required to have a means of emergency steering, which is invariably located as close to the rudder as possible and thus very far from the bridge. Those operating the emergency steering need to receive orders and so, as well as voice communication to the engine room, there must also be a means to communicate directly with the emergency steering room from the bridge. There must also be a public address system for allowing commands to be broadcast throughout the vessel.

Many of the information display systems required under SOLAS vary depending upon the ship’s size. All vessels above 300gt and all passenger ships are required to have a speed-and-distance measuring device for measuring speed and distance through the water (SOLAS Regulation V/ In addition, ships of 50,000gt and over require a similar device for measuring speed over the ground in the forward and athwartships directions (SOLAS Regulation V/ Both devices, if fitted, should be connected to the ship’s VDR. The devices are usually referred to as Doppler Speed Logs for the simple reason that they operate using Doppler radar and a transceiver fitted to the ship’s hull.

Until very recently, it was considered sufficient to meet the requirements for the larger ships to be covered by installing a single device capable of indicating both measurements. However, in July 2013 following MSC 90, the IMO issued a clarification that on ships requiring both devices (ie ships of 50,000gt and over) the requirement should be fulfilled by two separate devices: one speed and distance measuring and indicating device capable of measuring speed through water; and a separate speed and distance measuring and indicating device capable of measuring speed over the ground in the forward and athwartships directions.

These amendments are published in IMO resolution MSC.334(90) and the IMO circular MSC.1/Circ.1429 and apply to devices installed on ships constructed on or after July 1, 2014.

Above 500gt, ships are also obliged to be fitted with a rudder angle indicator which, as the name indicates, provides information displaying the angle of the rudder. The same ships must also have a display indicating the thrust and pitch of the propeller(s) if they are fitted with controllable pitch propellers. On all ships above 50,000gt there is an additional requirement for a rate-of-turn indicator to give information on how fast the ship is turning at a steady rate. The display is normally shown as number of degrees turned.

As a means to prevent the helmsman suffering from fatigue, ships of 10,000gt and above are required to be fitted with an autopilot. Autopilots, or heading control systems as they are commonly referred to, are also common on smaller vessels where their installation is not mandatory simply because of the benefits they can confer. The autopilot should not be used in high traffic areas and it is essential to keep a lookout whenever it is in use for obvious reasons.

The performance standards for autopilot systems are quite extensive and have adapted over time to cover evolving technology such as ECDIS. As a consequence, autopilot systems are now capable of more than just maintaining the vessel on a pre-set heading with minimum operation of the ship’s steering gear. Being connected to the gyrocompass and GPS as well as the ECDIS, an autopilot can now be part of a track-control system, making turns and following a pre-determined passage plan. If the system is to make turns it should be connected to a suitable source of speed information and be able to perform turns within the turning capability of the ship, based either on a pre-set turning radius or a pre-set rate of turn.

Since some systems will be fitted with remote stations to which control can be delegated, it is also a requirement that the master station should have a means to regain control at any time. Finally, the system must also incorporate alarms that operate if the vessel deviates from the pre-set course or if there is a failure or a reduction in the power supply to the heading control system or heading monitor, which would affect the safe operation of the equipment.

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