NT888G MK2 AUTOPILOT OPERATING MANUAL
2.24 Evaluating the Counter Rudder Setting (Continued).
Opposite -
Monitors the closing rate towards a new course to prevent
‘overshoot’ by removing rudder early and applying opposite
rudder to ‘meet’ and stabilise the vessel on the new heading
specified.
Adjusting the Counter Rudder Setting.
The Counter Rudder effect may be increased or decreased by adjustment of the
Autopilot
COUNTER
value via the
CONTROLS
Menu between the Limits of 1 to 9
where 9 produces maximum counter rudder.
(i)
With the Autopilot engaged (ON) and the vessel underway on a stable
heading, use the Autopilot Set Course knob to order a course change of
30° Port or Stbd of the current heading.
(ii) Observe the response of the vessel noting whether overshoot
occurs or whether the vessel is prematurely arrested in its turn to the
new heading.
(iii) Repeat the 30° course change in the opposite direction to gain an
average evaluation.
Vessel Consistently Overshoots - Increase the Counter Rudder Value
Vessel Prematurely Arrested
- Decrease the Counter Rudder Value
The optimum Counter setting has been achieved when the vessel turns efficiently to
the new heading and stabilises without overshoot.
To increase / decrease the Counter Rudder value: -
(iv) Use
the
CONTROLS
key 4 times to select “
COUNTER
” in the Menu.
(v)
Rotate the illum. control (+/-) to increase or decrease the highlighted
“COUNTER” No
. (1 to 9) as required.
(The highlighted counter value will timeout after a period of 30 seconds
and the display will automatically revert to the standard operational
mode).
NB. If overshoot persists despite a high Counter Control setting it is likely that
the AUTOTRIM Timing Period is too short and can be evaluated as follows: -
(vi)
Set the Autotrim key
OFF
.
(vii) Use the Autopilot Set Course Control to order a 30° course change.
(viii) If there is now no overshoot or the vessel is prematurely arrested
turning to the new heading the AUTOTRIM Time Constant must be
increased. (See Section 2.23).
