Many Avionics Failures are Caused by Tolerance Irregularities in Mechanical Interfaces 861781

Electronic equipment used in complex air, sea, and space vehicles is designed to be “line replaceable” in order to facilitate maintenance without major disruption of schedules. Unscheduled removals trigger a chain of events exposing the suspect equipment to none-to-gentle shipping and handling enroute to the test bench. Hare often than not a failure is not indentified, and the equipment is subjected to further abuse on the way back to the line. This paper discusses some of the potential causes of these “unconfirmed” failures and suggests some practical design approaches to minimize the problem.
AERONAUTICAL AND AVIONIC engineers can take great pride in the advances they have made in their individual disciplines over the past 40 years. Despite the effectiveness of each, aircraft continue to be plagued with unconfirmed avionics removals, just as they were in the past. It is in this area that it seems little progress has been made.
This paper enumerates the various reasons for the continued problems with avionics and recommends the establishment of a new discipline, a new industry, as it were, to accept responsibility for assuring that avionics function as effectively in the aircraft as on the test bench. This is a critical necessity. While the avionics are generally squawked when they fail to function properly, neither aeronautical nor avionics engineers are in a position to probe for the real causes of the removals. As a result, avionics removals continue to self-perpetuate.
This lack of a discipline to direct the interface between the host platform, or airframe, and the avionics is costly to both commercial airlines and the military.


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