Bond-related Aircraft Accidents/Incidents: A Review

FAA Technical Library2021PDFTech ReportMomm, Guilherme GIlcewicz, LarryAshforth, CynthiaFleming, DavidFlorida Institute of TechnologyNational Civil Aviation Agency (Brazil)United States. Federal Aviation Administration. Aircraft Certification ServiceUnited States. Federal Aviation Administration. Aircraft Certification ServiceUnited StatesStructural connectionBondingAircraft collisionsTraffic dataAir transportation crashesCrashesstructural bondingcontinued airworthinessin-service datareviewDOT/FAA/TC-21/22Pham, LynnFinal ReportThis work surveyed aircraft accidents/incidents in which a bond failure was a contributing factor. This survey was used to identify potential shortfalls in the certification of bonded structures. We reviewed, summarized, and compiled investigation reports, safety recommendations, and airworthiness directives associated with bond failure-related events. These documents originated mainly from countries with large civil aviation fleets that maintain online, publicly available databases. This survey was limited to typecertified, civil aeronautical products, irrespective of the manufacturer, model, size, or age. A total of 73 bond-related events involving aircraft registered in 13 countries on five continents were found. We grouped these events according to the aeronautical product\u2014transport airplanes, general aviation airplanes, rotorcraft, propellers, and engines\u2014containing the failed bonded joint. Each of these groups is type-certified under specific airworthiness requirements. For each event, we classified the bond failure\u2019s root causes into the following categories: design, production, operation, and maintenance. Analysis of the compiled data revealed that maintenance or production issues often contributed to the reviewed bond-related events. This analysis also emphasized the need for process control/validation and durability substantiation to ensure the long-term safe operation of bonded structures. The data supports a conclusion that no additional layer of protection\u2014e.g., load path redundancy, damage growth arrest features, environmental protection measures, damage tolerance-based maintenance actions, or advanced nondestructive inspections\u2014can alone guarantee the expected joint structural performance in case of substandard bonding without adequate material and process control. These observations are consistent with current certification guidance materials.119