IMO Performance Standards for Heading Control Systems (AutoPilots)

IMO Performance Standards for Heading Control Systems (AutoPilots)

IMO PERFORMANCE STANDARDS FOR HEADING CONTROL SYSTEMS(AUTOPILOTS)OBJECTIVES1. Within limits related to the ship’s maneuverability the headingcontrol system, in conjunction with its source of headinginformation, should enable a ship to keep a preset heading withminimum operation of the ship's steering gear.2. A heading control system may work together with a track controlsystem adjusting its heading for drift.3. A turn rate control for performing turns may be provided.FUNCTIONAL REQUIREMENTS1. The heading control system should be capable of adaptingmanually or automatically to different steering characteristics of theship under various speeds, weather and loading conditions, andprovide reliable operation under prevailing environment and normaloperational conditions.2. The heading control system should be able to perform turns,within the turning capability of the ship, based either on a presetturning radius or a preset rate of turn.3. Means should be incorporated in the equipment to enable rudderangle limitation in the automatic mode. Means should also beavailable to indicate when the angle of limitation has beencommanded or reached.4. Means should be incorporated to prevent unnecessary activationof the rudder due to normal yaw motion.5. Any alteration of the preset heading should not be possiblewithout intended action of the ship's personnel.6. The heading control system should change to a preset headingwithout significant overshoot.CHANGE-OVER FROM AUTOMATIC TO MANUAL STEERING AND VICEVERSA1. Change-over from automatic to manual steering and vice-versashould be possible at any position of the rudder and should beeffected by one manual control within 3 seconds.

2. Change-over from automatic to manual steering should bepossible under any conditions including any failure in the automaticcontrol system.3. When changing over from manual to automatic steering theheading control system shall take over the actual heading as thepreset heading.4. There should be a single change-over control which should belocated in such a position that it is easily accessible to the officer of the watch.5. Adequate indication should be provided to show which method of steering is in operation.CHANGE-OVER FROM TRACK CONTROL TO HEADING CONTROL1. If the heading control system works as part of a track controlsystem, then when switching from track control to heading control,the actual heading should be taken as the preset heading.2. Any switching back to track control shall not be possible withoutintended action of the ship's personnel.ALARMS AND SIGNALLING FACILITIES1. An alarm both audible with mute function and visual should beprovided in order to indicate failure or a reduction in the powersupply to the heading control system or heading monitor, whichwould affect the safe operation of the equipment.2. An off-heading alarm, both audible with mute function and visualshould be provided when the actual heading deviates from thepreset heading beyond a preset limit.3. If the ship is required to carry two independent compasses, aheading monitor should be provided to monitor the actual headinginformation by independent heading sources. The heading monitoris not required to be an integrated part of the heading controlsystem.4. An alarm both audible with mute function and visual should beprovided when the heading information in use deviates from thesecond heading source beyond a preset limit.5. A clear indication of the actual heading source should beprovided.CONTROLS1. The number of operational controls should be such that easy andsafe operation can be achieved. The controls should be designed topreclude inadvertent operation.2. Unless features for automatic adjustment are incorporated in theinstallation, the heading control system should be provided withadequate controls to adjust to effects due to weather and the ship'ssteering performance.3. The heading control system should be designed in such a way asto ensure altering the pre-set heading to starboard by turning theheading setting control clockwise or tilting it to the right-hand side.

Normal alterations of heading should be possible by one adjustmentonly of the preset heading control.4. Where remote control stations are provided, facilities for thedelegation of control to the remote station and unconditional returnof control should be incorporated in the master station.5. Except for the preset heading setting control, the actuation of anyother control should not significantly affect the heading of the ship.INTERFACING1. The heading control system should be connected to a suitablesource of heading information.2. The heading control system should be connected to a suitablesource of speed information when it is used in a turning radius modeor when any control parameters are automatically adapted tospeed.3. If a heading control system is capable of digital serialcommunication with the ship's navigation system then the interfacefacilities should comply with the relevant international marineinterface standards.