The test modes use test switches on the sonar set to initiate special test signals within the system to permit the operator to test all system components either on the ground or in flight. Front panel advisory indicators illuminate to indicate a GO/NO-GO status, and PPI, RANGE RATE-METER, dome control and BT recorder indicate quantitative test results. During normal operation, the test circuits sample major system functions and voltages. Fault conditions will occur with open or short circuited depth or cable payout potentiometer; with helicopter height less than 20 ±10 feet; or if the rate of change in height exceeds approximately 5 feet per second. If a sampled function exceeds preset limits, the FAULT indicator illuminates for the length of time that the fault exists. Rate faults can occur in the VERT ACCEL or RDR ALT mode and are indicated by a flashing FAULT light on the sonar indicator. If the fault cannot be cleared in the VERT ACCEL or RDR ALT mode, sonar operations are to be discontinued.

A malfunction in a power supply causes the POWER/FAULT indicator to illuminate until the power fault circuit is reset by depressing the POWER/FAULT indicator. Depressing the TEST/READY indicator illuminates all system indicator lamps except the SEAT lamp located on the dome control. To test the SEAT lamp, the SEAT indicator/push-button shall be depressed. Setting the TEST switches to any position other than 0-0 causes the TEST indicator to illuminate. The READY indicator illuminates after a delay of between 2.5 to 8.5 seconds, depending on the test. Some tests will also provide calibrated displays on the BITE selection.