NT888G MK2 AUTOPILOT OPERATING MANUAL
2.25 Optimising the Yaw Control Setting.
The YAW control setting defines the Autopilot sensitivity to short term yaw or course
error and determines how much short term error will be tolerated before corrective
rudder is ordered.
A minimum YAW setting (N°1) prescribes maximum Autopilot sensitivity (±0.7°)
increasing linearly to a maximum setting (N°9) for minimum sensitivity (±10°) (i.e.
minimum yaw = maximum sensitivity and vice versa).
NB.
The minimum yaw setting limit of ±0.7° referred to above does not restrict the
Autopilot in it’s ability to maintain heading control more accurately than ±0.7°.
In practice, the cumulative effects of Counter Rudder and Autotrim (APH)
combine to produce an overall resolution of ±0.2°.
This combined effect is particularly important in heavy sea conditions when the
YAW control setting can be increased to prevent unnecessarily frequent rudder
movements in response to sea state induced yaw. In such conditions and
despite the wider deadband (increased tolerance to natural yaw) the Autopilot
will continue to monitor and control the mean course accuracy as a function of
the Autotrim (APH Integrator) with a higher long term resolution than the Yaw
control setting would otherwise permit.
As a general rule, the Yaw control should be set at the lowest number
that provides the required course keeping sensitivity and ‘straight wake’
performance but avoids unnecessary rudder movements in response to
natural Yaw.
The Yaw control is adjusted via the
CONTROLS
Menu:-
(i) Use
the
CONTROLS
key three times to enter the Controls Menu and
select
YAW
(followed by highlighted digit 1 to 9).
(ii)
Rotate the illum. control (+/-) to increase or decrease the setting as
required.
(iii)
Timeout and retention of new setting will occur automatically when the
display will revert to the standard operating mode.
2.26 STW Speed Data Input (Speed through the Water).
It is essential to note that Speed through the water (STW) input data is the primary
requirement for the Autopilot Speed Adaptive operating mode.
In the absence of STW data – Speed Adaptive operation is not possible and any
attempt to calibrate (section 2.29) or engage the Adaptive mode will be rejected and
accompanied by an audible alarm and display message
No SPD adaptive
.
2.27 SOG Speed Data Input (Speed over the Ground).
It is essential to note that Speed over the Ground (SOG) input data is the primary
requirement for Autopilot
RADIUS
of
TURN
control when operating in a stand alone
mode.
