During the manufacture of the apex pin, the initial machined profile led to unintended stress concentrations at the quench stage of the material heat treatment process that resulted in the part cracking. The crack was not removed by the final machining process.
Manufacturing process corrected and existing parts checked for airworthiness.
In response to the two pin failures and the subsequent investigation, Safran Landing Systems reviewed the manufacturing process and identified that subsequent to the pins’ manufacture, the manufacturing process had been amended to include a larger initial machining radius under the pin head. This change significantly reduced any stress concentrations under the head that may be induced by the heat treatment process. Additionally, the company generated a design guidance document for radii in high strength steel parts prior to heat treatment.
In response to the two pin failures, Airbus issued AOT A32N018-20 on 23 January 2020, which recalled some apex pins. As a result of analysis conducted, AOT A32N018-20 Rev 01 was issued on 27 April 2020 expanding the number of pins to be inspected. As result, aircraft operators were adequately informed of the issue and could take appropriate action.
In response to the two pin failures and the subsequent investigation conducted by Airbus, EASA issued airworthiness directive AD 2020-0130 on 8 June 2020, which mandated the inspections required by Airbus AOT A32N018-20 Rev 01. As result, aircraft operators were adequately informed of the issue and could take appropriate action.
The ATSB reviewed the above proactive safety action taken by Safran Landing Systems, Airbus, and the European Union Aviation Safety Agency (EASA) and determined the action adequately addressed the issue. The manufacturing processes have been corrected, including the development of design guidance material for the development of any future components with similar features. The existing components that may have contained cracks have been recalled through direct communication and via inspection mandated by an EASA Airworthiness Directive.
