What happened
On Friday, August 6, 2010, a Robin DR 360, registration F-GMJE, was performing a local flight at the Valenciennes aerodrome. Following a successful landing, the pilot was taxiing the aircraft toward the parking area. During the taxi, the pilot experienced a sudden blockage in the nose gear, causing the aircraft to come to a complete stop. Upon shutting down the engine and inspecting the landing gear, the pilot discovered that the nose gear had suffered a significant structural failure.
The investigation
The investigation focused on the disassembly and examination of the nose gear, which was a "SAB" type construction. Investigators found that the upper mounting plate of the nose gear had fractured at the weld bead that connects the strut to the upper plate.
Fractographic analysis of the failure site revealed a pattern of progressive fatigue cracking within the weld bead and the plate area. This fatigue crack propagation had gradually weakened the assembly until the final structural rupture occurred. The investigation also reviewed existing airworthiness directives regarding similar failures observed in "Robin" type nose gear constructions.
Findings
- The primary cause of the accident was the presence of undetected fatigue cracks at the weld bead connecting the strut to the upper mounting plate of the "SAB" type nose gear.
- At the time of the accident, existing maintenance procedures and airworthiness directives did not specifically require inspections for cracks on this particular "SAB" model of nose gear.
- While a previous EASA directive (2007-0171) addressed similar failures in other nose gear types, it excluded the "SAB" construction from its inspection requirements.
Safety action
Following the identification of this vulnerability, EASA issued airworthiness directive EU-2010-0231 on November 5, 2010. This new directive expanded the scope of mandatory inspections to include the detection of cracks on "SAB" type nose gear assemblies.