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3. ARP OPERATION
3-22
3.12 Setting CPA/TCPA Alarm Ranges
The ARP continuously monitors the
predicted range at the Closest Point of
Approach (CPA) and predicted time to CPA
(TCPA) of each tracked target to own ship.
When the predicted CPA of any target
becomes smaller than a preset CPA alarm
range and its predicted TCPA less than a
preset TCPA alarm limit, the ARP releases
an audible alarm and displays the warning
label COLLISION on the screen. In addition, the ARP symbol changes to a
triangle and flashes together with its vector.
Provided that this feature is used correctly, it will help prevent the risk of collision
by alerting you to threatening targets. It is important that GAIN, A/C SEA, A/C
RAIN and other radar controls are properly adjusted.
CPA/TCPA alarm ranges must be set up properly taking into consideration the
size, tonnage, speed, turning performance and other characteristics of own ship.
Note: The reference point for CPA/TCPA calculation may be chosen from
antenna position or conning position. For further details, see paragraph
1.50.
3.12.1 Setting CPA/TCPA alarm ranges
To set the CPA/TCPA alarm ranges, do the following:
1. Roll the trackball to choose the CPA LIMIT box. If only “CPA LIMIT OFF”
appears press the left button to show the CPA and TCPA boxes.
CPA LIMIT 0.5NM 10MIN
TCPA LIMIT Box
CPA LIMIT Box
CPA LIMIT and TCPA LIMIT boxes
2. Push the left button or roll the wheel to choose the CPA LIMIT box and then
push the wheel.
Left button: 0.5, 1, 1.5, 2, 3, 4, 5, 6(nm)
Wheel: 0.5 - 20(nm), 0-20 nm in 1 nm increments, 0.5 nm increments
thereafter
3. Roll the trackball to choose the TCPA limit box.
4. Push the left button or roll the wheel to choose TCPA value desired and then
push the wheel.
Left button: 1, 2, 3, 4, 5, 6, 12, 15(minutes), Wheel: 1-60 m, 1 m increments
CAUTION
CPA/TCPA Alarm
The CPA and TCPA alarm feature should
never be relied upon as the sole means for
detecting the risk of collision.The navigator
is not relieved of the responsibility to keep
visual lookout for avoiding collisions,
whether or not the radar or other plotting
aid is in use.