Operating manual ALPHASEAPILOT MFC Issue 1.1 Page 63 of 84
ALPHASEAPILOT MFC
2.35 Optimising the Off Heading & Course Comparator (CCA) Alarms
The Autopilot OFF HEADING ALARM (OHA) continuously monitors and compares the
difference between the heading set and the actual heading steered to generate an audible and
visual alarm if the specified limit is exceeded.
The OHA function differs greatly from the COURSE COMPARATOR ALARM function (CCA)
which does not compare actual heading with heading set but instead compares the values of
two Autopilot heading inputs to generate an audible and visual alarm if one value (heading)
differs by more than a programmed amount from the other.
Alarm Trip Level.
The specified limit (Alarm trip level) is operator selectable at 2° to 30° in 2° steps – or can be
switched OFF - via entry to the LIMITS Menu.
NB. When in TRACK steering mode using HTC sentence data received from an Approved Track
Control System, the Off Heading Alarm limit may be set to a value demanded by the Track
system – or switched OFF - if ordered.
Alarm Cancellation.
The audible/visual display alarm can be cancelled by use of the alarm TEST key but is
programmable via the SET UP Menu in two categories:-
(i) OHA DELAY – Parameter No. 35 in the Set Up Menu, this can be
programmed from 10 to 60 seconds in 2 sec steps as
the delay time from exceeding the alarm trip level to
generation of audible and visual alarms.
This feature prevents unnecessary alarms due to
natural yaw/periodic motion of the vessel.
(ii) OHA ALARM TIMEOUT – Parameter No. 48 in the Set Up Menu, this can be
programmed from 30 to 120 seconds in 1° steps as the
delay time to allow the vessel to turn to a new course
when ordered by the Autopilot.
If required, the audible alarm can also be permanently switched OFF via LIMITS Menu.
To alter/set OHA Delay or OHA Alarm Timeout:-
a. Simultaneously press the “CANCEL” and “CONFIRM” keys for 5 seconds until the
Set Up Menu is displayed with a black cursor highlighting the Set Up parameter
currently selected.
b. Rotate the Autopilot Set Course Control to move the cursor to parameter number
35 (OHA DELAY) or 48 (OHA TIMEOUT).
c. Use the rotary (+/-) illum. control to set time (secs) as required.
To set the OHA Trip Level or switch the Off Heading Alarm OFF:-
d) Use the “LIMITS” key to enter the Limits Menu.
e) Use the “LIMITS” key again to select “O.H.A.” box followed by flashing current
value (2° to 30° or OFF).
f) Use the rotary (+/-) illum. control to set as required.
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