Aging avionics-what causes it and how to respond

Considering the issues of aging hardware and usable life and determining when to retire an avionics unit from service is a key factor to provide uninterrupted, reliable, and safe performance of our avionics products. The period of useful life for different components and subsystems can vary significantly and the period when the hazard rate is increasing can be difficult to pinpoint. Hardware in this phase of life may have intermittent and differing causes of failure that are hard to isolate and wearout mechanisms can be complex and may exhibit different failure modes. This condition may account for some avionics units sometimes called "a rogue unit." When fielded hardware exhibits a clear and unambiguous increase in failure rate is several years old (ten-plus) and has high logged operating hours, an assessment of the remaining life of the products should be considered. If it can be demonstrated that an end of life condition is being approached by a piece of hardware, particularly avionics hardware in a safety of flight subsystem, then it would be prudent to remove the hardware from service. The rationale is that the hardware was certified based on an analytical process defining an achievable level of safety. Central to the safety analysis is the reliability of the hardware. As the hardware degrades and is no longer capable of its original predicted or demonstrated level of reliability, then the top level safety may also no longer be achievable.