NT888G MK2 AUTOPILOT OPERATING MANUAL
2.20 Optimising the Rudder Control Setting.
The RUDDER control provides the operator with the means to increase or decrease
the angle of rudder applied in relation to course error and should be adjusted to
provide positive correction of Yaw without oversteer (Section 2.19 refers).
NB. Certain types of vessel steering characteristics benefit greatly from the
anticipation afforded by a competent helmsman in applying short term
exaggerated angles of rudder in order to check or ‘counter’ yaw inertia as soon
as ‘felt’. The Autopilot Counter Rudder function produces a similar effect and it
may prove beneficial at a later stage to increase the COUNTER control setting
by an amount, which fully optimises the straight-line steering performance.
Under normal operating conditions (normal cruising speed and average sea state) the
RUDDER value will ideally be set at approximately mid range (No. 5 in the Controls
Menu) to provide operator scope for increase or decrease in significantly changed
operating conditions.
In heavy following sea conditions or at very slow speeds, it is likely that the operator
will need to increase the RUDDER control setting whereas at full speed or when
beating into sea the RUDDER control setting will need to be decreased.
NB.
Once the Adaptive calibration has been optimised versus Speed & Draft input
data, the RUDDER parameter adjustment will be automatic in the Adaptive operating
mode. (Sections 2.29 & 2.30 refer).
If it is found that the maximum (No. 9) RUDDER value typically does not produce
enough rudder or, conversely, if the minimum (No. 1) RUDDER value typically
provides too much rudder, the entire band of control available to the operator can be
increased or decreased by corresponding Loop Gain adjustment via the Autopilot Set
Up Menu as specified in section 2.21.
2.21 Optimising the Rudder Control Band.
A RUDDER control value of No. 1 (Controls Menu) will produce 1/3
rd
(33%) of the
angle of rudder otherwise produced by a control setting of No. 9. The resultant 3:1
range available to the operator can be calibrated via access to the Set Up Menu to
produce actual degree of rudder per degree of course error ranges (or bands) as
follows:-
Loop Gain values:-
Minimum:
0.33°/° (N°1) to 1°/° (N°9) = rudder/degree of course error.
Maximum:
1°/° (N°1) to 3°/° (N°9) = rudder/degree of course error.
The factory default range setting for loop gain provides 0.5° to 1.5° of rudder
per degree of course error but as a general rule, the operating band via Loop
Gain calibration should initially be set as follows: -
Fast planing/semi planing vessels (HSC)
-
0.33° to 1° per degree
Deep sea fishing vessels etc.
-
0.5° to 1.5° per degree
Heavy displacement ocean going vessels
-
1.0° to 3.0° per degree
