NT888G MK2 AUTOPILOT OPERATING MANUAL
2.7 The AUTOTRIM Key (Automatic Permanent Helm).
AUTOTRIM (Automatic Permanent Helm) is applied by the Autopilot over a period of
time when underway to offset the rudder and eliminate heading errors caused by
windage or vessel trim etc.
The Autotrim function can be permanently switched off if required (confirmed by
illumination of the “
AUTOTRIM
” key corner LED) or can be used to instantaneously
assess the required rudder “offset” angle when the Autotrim key “
SET
” facility is used.
NB.
The
AUTOTRIM
key is also used simultaneously with the
TRACK
key to enter
the Diagnostic Mode. (Installation and Tech Manual Section TM5).
Most of the Autotrim Set Up parameters are determined during Sea Trials and include
the APH Time Constant and Autotrim Trip Angle, the values of which are set/altered
via the Set Up Menu. (Installation and Tech Manual Section 3.13 to 3.15).
The Set Up Menu also offers special Autotrim operating modes but standard (STD)
mode is normally chosen. In the standard mode, the “
AUTOTRIM
” key is used as
follows:-
(i)
Factory default setting is AUTOTRIM active (ON) when the Autopilot is
switched from “
STANDBY
” to “
ON
”.
(ii)
To switch the Autotrim facility OFF, press the “
AUTOTRIM
” key for 5
seconds until the corner “
OFF
” LED illuminates. (Autotrim will
automatically revert to the active state when the Autopilot is switched
“OFF” and “ON” again).
(iii)
Single press the “
AUTOTRIM
” key to switch Autotrim ON again if the
corner LED is illuminated (Autotrim off).
(iv) Single press the “
AUTOTRIM
” key to automatically assess and
instantaneously apply the correct angle of rudder (APH).
