Detecting intermittent test failures with the aid of environmental stress screening

Confirmation of avionics field failures by a depot maintenance organization is often performed on Automatic Test Equipment (ATE) which is designed to certify a module as "fit to fly". When the ATE does not confirm the failure, the field failure is generally regarded to have been an intermittent event. For any application, these are a major cost driver, and for safety-critical applications, intermittent events are intolerable. As part of the depot maintenance plan to assure a reliable repair operation, an Environmental Stress Screening (ESS) process is employed to detect and eliminate latent defects induced by the repair operation. The time available during this process allows the application of test and monitoring equipment designed specifically to detect and identify intermittent failures.