AUTOPILOT

1. AUTOPILOT
AUTOPILOTS:
This is intended to remove the need for the operator to assess the correct control settings. In
effect the autopilot ‘learns’ the vessel’s handling characteristics in calm weather and then,
when the weather deteriorate, can distinguish between those errors in heading due to the
weather and those due to vessel’s normal handling characteristics. It has been found that in
heavy weather the vessel’s head deviates very little ‘relative to the water’.T4 the adaptive
autopilot concerns itself primarily with those errors in heading resulting from normal
handling characteristics, so reducing the work and hence drag of the rudder.
For example in Sperry model auto tuning software is fitted. The software performs dynamic
tuning of the autopilot during a modest series of initial maneuvers, then automatically
continues to retune the tuning throughout the voyage in response to the ship’s behavior.
System also maintains two different tunings, one for light and one for loaded condition.
Limitations of auto pilot: Auto pilot should not be used under following circumstances:
(WASTV MNS)
In rough weather
During large alterations of courses
At slow speeds
In heavy traffic areas
In conditions of reduced visibility
While maneuvering the vessel
In narrow channels and confined waters.
In shallow waters
CONTROL UNIT:
1)PROPORTIONAL CONTROL: Output of the controller is proportional to the offcourse
error from the course to steer ( deviation)
Controller ouput = constant (Kp) x Deviation
2) INTEGRAL CONTROL: Output of the controller is proportional to the summation of all
instantaneous values of error ( deviation ) for as long as error persists.
error x TimeController output = constant ( Ki ) x
3) DERIVATIVE CONTROL: Output of the controller is proportional to the rate of change of
error ( deviation ).
Controller output = constant ( KD ) x change of error / time
THREE TERM CONTROLLER ACTION: Output signal is proportional to the deviation,
persists as long as deviation persists and also depends on rate of change of deviation i.e.
Proportional + Integral + Derivative
CONTROLS:
WEATHER SETTING CONTROL: When steering in heavy weather with wind and sea at an
angle to the vessel’s heading, there is a tendency for the vessel’s head to be turned in a
particular direction. The effect of this can be offset by maintaining some permanent value of
rudder angle; this angle is set using ‘weather helm’ after a period of trial and error.
SYNCHRONISATION CONTROL: Temporairly disconnects gyro repeater from main gyro
for sync of heading. Required for sync and when gyro switched off and restarted.
SPEED: Usually from log and manual if log fails
COURSE SELECTOR KNOB: For setting course to be steered.
DIMMER: For illumination of panel
AUTO/FOLLOW UP/ NON FOLLOW UP : For choosing steering mode

2. RUDDER LIMIT: Purpose is to prevent a maneuver more radical than is compatible with:
Speed loss
Comfort on ship
Safety of ship
Rudder angle greater than 15 to 20 deg do not improve course alteration but result in
excessive speed loss.This control limits the number of degrees of helm that can be applied
by auto pilot computer in any mode. Limits are : 5, 10, 15 and 20 degrees.
OFF COURSE ALARM: It gives alarm if ship deviates from set course by a pre determined
limit. Setting depends on Wx condition, open/coastal waters.
RUDDER CONTROL: This is proportional controller which transmits a signal which is
proportional to course error
Controller ouput = constant (Kp) x Deviation
The ratio can be changed by settings ( i.e. the ratio between instantaneous heading error
and rudder command)
Also called rudder multiplier
Control knob alters the ratio of output.
Higher setting -- Larger rudder angle ( results in overcorrecting – overshooting )
Lower setting – Less rudder angle ( Long time to return to set Co – Sluggish )
Therefore optimum setting required.
COUNTER RUDDER: This is Derivative control.
Purpose is to apply a relatively greater amount of helm at the beginning of a course
alteration to get the ship turning. Once the ship is turning, just enough helm is applied in
order to keep her coming around. When new heading is approached, opposite helm is
applied to stop the swing. As the ship settles on new heading and the yaw rate disappears,
the helm is removed.
Produces an output when course of vessel is changing.
Depends on rate of change of course:
Controller output = constant ( KD ) x change of error / time
Determines amount of counter rudder to steady the ship on set course.
Keeps over shoot to minimum.
Greater the ship’s inertia, greater the setting required. If ship has good dynamic stability,
relatively small settings of counter rudder will be sufficient. If the ship is unstable, higher
settings will be required.
Depends on ship’s characteristics, loaded/ballast conditions and rate of turn.
Too high setting will bring the ship to set Co slowly
Too low setting allows overshoot
As counter rudder settings increase , counter rudder increases.
KD – Counter rudder time constant ( Calibration done at sea trial to set KD )
PERMANENT HELM: This is integral controller.( In NFU this control is out of action)
When ship has known imbalance to one side, requiring a certain amount of bias helm ( e.g.
TT of propeller or extreme case of trawlers working their trawl over one side) manual setting
of the approximate bias speed up the effect of the AUTOMATIC PERMANENT HELM
calculator, because it started off nearer to its target.
Whether the control setting is estimated correctly or left at zero has no effect on the final
steering accuracy but only in the time it takes to reach this heading accuracy.

3. If not used as described above , the permanent helm should be left at ZERO and the
automatic permanent helm will function normally.
Produces output as long a course error persists
Used when beam winds; couple formed causing ship to turn into wind.
Rudder position required to counteract is permanent helm.
Continuous control calibrated from 20 (P) to 20 (S).
Changing over from Hand Steering to Auto Steering :
Before changing over from hand steering to auto steering, the settings on the auto pilot
panel must be adjusted for weather and traffic conditions.
The vessel must be made steady on the course on which she has to be set on auto steering.
Changing over to emergency steering system :
When the steering panel gives an alarm, it must be read carefully to see as to what has gone
out of order, operation must be changed-over to the other/ alterative steering gear/ motor
or transmission system/ telemotor, engineroom must be informed immediately.
If the Auto-pilot gives an alarm or the off-course alarm goes off, adjust the settings on the
Auto-pilot panel accordingly.
If the Auto-pilot fails, change-over to hand steering.
If the Follow-up system doesn’t work (the feedback leg of the steering gears doesn’t function
properly), change-over to Non-Follow-Up mode.
If the steering transmission systems or telemotors stop working, emergency steering has to
be performed by trick-wheel arrangement or solenoids after bringing the rudder mid-ships.
Further, if the steering hydraulic or electric motors also stop working, rudder will have to
turned by some mechanical arrangement like chains and blocks, this is not possible in case
of large rudders (large ships). As the last resort, Jury rudder is used, which means some
arrangement/ structural changes, which overside work as an alternative rudder
arrangement e.g. wooden planks on the stern turned/ rotated like a rudder.
Changing over (handing over/ taking over) of a watch between the OOWs whether at sea or
at anchor is done in compliance with the ISM checklists onboard which, in general, include
the following :
Use of the Automatic Pilot
4.- (1) The master shall ensure that an automatic pilot, where fitted, shall not be used in
area of high traffic density, in conditions of restricted visibility nor in any other hazardous
navigational situation unless it is possible to establish manual control of the ship's steering
within 30 seconds.
(2) Before entering any area of high traffic density, and whenever visibility is likely to
become restricted or some other hazardous navigational situation is likely to arise, the
master shall arrange, where practicable, for the officer of the watch to have available
without delay the services of a qualified helmsman who shall be ready at all times to take
over the manual steering.
(3) The change-over form automatic to manual steering and vice versa shall be made by, or

4. under the supervision of, the officer of the watch, or, if there is no such officer, the master.
(4) The master shall ensure that the manual steering gear is tested (a) after continuous use
of the automatic pilot for 24 hours and (b) before entering any areas where navigation
demands special caution.
Operations of Steering Gear
5. In areas where navigation demands special caution, the master shall ensure that the ship
shall have more than one steering gear power unit in operation when such units are
available and capable of simultaneous operation.
Steering Gear - Testing and Drills
6.-(1) The master shall, within 12 hours before departure of the ship, cause the steering gear
to be checked and tested so as to ensure that it is working satisfactorily:
Provided that in the case of ships regularly making more than one voyage a week to or from
the same port a check and test of the steering gear need only be made once in that week
unless a part of the steering gear or its control system has been dismantled or change since
the last test.
1764 MERCHANT SHIPPING
The test procedure shall include, where applicable, the operation of the following:
(a) the main steering gear;
(b) the auxiliary steering gear;
(c) the remote steering gear control systems
(d) the steering positions located on the navigating bridge
(e) the emergency power supply
(f) the rudder angle indicators in relation to the actual position of the rudder
(g) the remote steering gear control system power failure alarms
(h) the steering gear power unit failure alarms; and
(i) the automatic isolating arrangements and other automatic equipment required for
steering gear.
(2) The checks and tests shall include:
(a) the full movement of the rudder according to the required capabilities of the steering
gear;
(b) a visual inspection of the steering gear and its connecting linkage; and
(c) the operation of the means of communication between the navigating bridge and the
steering gear compartment.
(3) The owner shall provide simple operating instructions, with a block diagram showing

5. the changeover procedures, for the remote steering gear control systems and steering gear
power units, and the master shall ensure that they are permanently displayed on the
navigating bridge and in the steering gear compartment.
(4) A person shall not supervise the operation or maintenance of the steering gear unless
that person is familiar with the operation of the steering systems fitted on the ship, and,
where applicable, with the procedures for changing form one system to the other.
(5) In addition to the routine checks and tests prescribed in paragraphs (1) and (2) of this
regulation, the master shall ensure that emergency steering gear drills which practise
emergency steering gear procedures take place at least once every three months. These drills
shall include, where applicable, use of direct control form within the steering gear
compartment, the communications procedure with the navigating bridge and the operation
of alternative power supplies.
(6) (a) The date time and place that the said routine checks and tests are carried out and the
date and details of emergency steering drills carried out shall be recorded by the master in
the official logbook.
(b) In ships not required to keep an official logbook, a record of each check, test and drill
shall be made by the master and be retained on board for a period of six months and be
available for inspection on demand by a superintendent, proper officer or surveyor of ships.