ComNav Commander P2 & P2VS Installation & Operation Basic Operations
Document PN 29010074 V4.1 - 131 -
Understanding NAV Mode
In
NAV
mode, the autopilot steers the boat as required to maintain a Commanded Heading,
just like it does in
AUTO
mode.
And it also uses the compass source which you have selected for its “current Heading”, for
course-keeping purposes – again, just like in
AUTO
mode.
But there’s an important difference between the two modes:
•
In
AUTO
mode, the autopilot “obeys” the Command Heading you give it (with the
C
C
O
O
U
U
R
R
S
S
E
E
C
C
H
H
A
A
N
N
G
G
E
E
knob) … when you set an initial Heading, and later when you adjust
it, as & when sea conditions change, to keep the boat on a straight Track to your
destination.
•
In
NAV
mode, after you enter a destination, or a route of waypoints, in the Navigation
System, the autopilot uses the “steering & navigation” data received from that system
to determine the Commanded Heading required to get there, and then does it.
Another key feature of
NAV
mode is that, as each waypoint in a route to your destination is
reached, the autopilot can (either automatically, or when you “acknowledge” arrival at the
waypoint) change the Commanded Heading, to turn the boat onto the Track to the next
waypoint.
And then when the destination waypoint is reached, the autopilot will typically steer the boat
so that it orbits that waypoint
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, until the autopilot either is switched out of
NAV
mode, or you
give it new navigation information via the Navigation System.
Checking the Navigation Data
It is important to be sure that the Navigation System is providing good-quality data to the
autopilot. You can test this by following these steps:
1) Make sure the Navigation System is turned on and that a waypoint is programmed in and
activated.
2) Steer the boat close to the Track from the starting position to the waypoint.
3) In the NAV menu, select “CTS” for the “Correction” parameter.
4) Put the autopilot in
NAV
mode.
5) Observe the boat’s response for several minutes.
•
If the boat seems to be continually falling off-course (away from the Track), you
probably need to change “XTE Sense” (Cross-Track Error sense) in the Nav menu
from “Norm” (normal) to “Rev” (reverse). Then repeat this step.
6) If the boat is wandering back and forth, but there are no alarms on the autopilot or
Navigation System, the data being provided to the autopilot may not be good enough.
The most common cause of this is poor signal quality in the sensor or antenna wiring of
the Navigation System. This may be due to:
•
Improper grounding
•
Electrical noise generated in the boat (alternators, power packs, etc.)
•
Poor antenna location
In this case, you should refer to the Navigation System’s manual for how to deal with
poor signal quality, and for what to do to make improvements.
It may also be helpful to consult your ComNav Dealer.
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… although it depends on what the Navigation System is set up to do when the destination is reached.
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