Downloaded from https://www.everyspec.com ADS-79D-HDBK The purpose of these tests is to support the Fault Detection and Characterization diagnostic and to provide sufficient Fault Isolation to support line maintenance operations. Line maintenance operations consist of component replacement and other adjustments made at the LRU level. H.3.3.4 Testing in Depot Environments. Depot tests are run when the Unit Under Test (UUT) is installed outside of the normal operating environment. The goals of testing in a depot environment are to verify that new components function properly and to support the Repair of Repairable diagnostic.
Testing in a depot environment typically includes, but may not be limited to, all of the in situ tests run for an LRU. These tests are run to verify that an LRU has failed or has been repaired and to focus additional diagnostic and repair activities that are available only to the depot, vendor, or hardware developer. Depot tests that are executed below the LRU level typically require the support of additional ATE. The development, standardization, configuration, and use of ATE is its own complex domain and is beyond the scope of this appendix.
H.3.4 Diagnostic Example The current process is lends itself to scenarios where the current testing methods result in Can Not Duplicate (CND) failure for the electronic module. The following scenario is typical in the diagnosing faults for electronic modules: Test Incident #19 : IBIT Fail (050010) "IR focus test― Description of Problem: Unable to manually focus IR video. Root Cause: Undetermined. After the first fail, the receiver was removed from the turret and, when bench test attempted to isolate to the failed item, the failure symptom went away. Efforts to reproduce were unsuccessful. Turret was reassembled and placed back in test. After ~150 hrs the failure returned.
Again the open circuit was verified at bench test within the turret but once the turret was removed, the failure vanished again. Current Status: TBD Number of Occurrences: 2 It is possible the failure is related to operating environments such as high temperature, temperature cycling, humidity, and vibration. The environmental stressors would degrade the connections or cause solders joint cracks or corroded which would cause the intermittent failure. One method to correct this CND failure is to capture the conditions of use and determine the accumulated damage. The sensor will be embedded to the LRU (Temperature, vibration and humidity sensors).
The data would be transfer to base station where it would be simplified and analyzed. The following process outlines the steps to implement an electronics Health Monitoring System to alleviate the CND outcome. 141