Question 886Navigation General

The correct answer is B) A tracked target entering your preset CPA-TCPA limits. The ARPA (Automatic Radar Plotting Aid) is designed to monitor the movement of tracked targets and provide alarms when certain conditions are met. One of these conditions is when a tracked target enters the user-defined limits for closest point of approach (CPA) and time to closest point of approach (TCPA). When this occurs, the ARPA will emit both a visual and audible alarm to alert the operator of the potential collision risk. The other options are incorrect because: A) The initial detection of a target within a guard zone may trigger an alarm, but this is not specifically an ARPA function. C) The entry of an acquired target into a guard zone may trigger an alarm, but again this is not specific to the ARPA. D) The loss of a tracked target for one radar scan is not sufficient to trigger an ARPA alarm.