Failure analysis of a brazed, stainless steel fuel injection line

Abstract

An aircraft fuel line was found to have fractured and caused an in-flight fire. A brief history of the general problem of cracking in brazed stainless steel fuel injection lines places this failure in context. The fracture mechanism was likely to be fatigue due to vibrations. Other factors contributed to the failure, such as an inappropriate braze repair and incorrect bend radius and location dimensions. The effectiveness of current airworthiness directives and manufacturer service bulletins are discussed. Alternative designs are suggested to prevent recurrence.