What happened
On the night of 26 November 2005, an Airbus A3/2-231, registration VT-ESF, was taxiing at Singapore Changi Airport toward its departure for Chennai. While moving along Taxiway EP, the aircraft experienced a structural failure in its left-hand main landing gear. Specifically, the bogie beam fractured at the center point where the main landing gear strut is attached. The failure caused the left landing gear to drag along the ground for approximately 50 meters, gouging the asphalt of the taxiway. The aircraft was able to come to a complete stop between taxiways B2 and B3, and there were no injuries reported during the incident.
The investigation
Investigators examined the fractured components and analyzed grease samples to determine the failure mechanism. Laboratory testing conducted in Singapore, the UK, and France revealed that the fracture originated at the radius intersection of the bogie pivot pin bore and the cross bolt hole. The analysis showed that corrosion pits had developed underneath the protective cadmium plating and paint. Furthermore, the investigation found that during a previous overhaul in July 2003, the cadmium plating thickness at the cross bolt hole did not meet the required minimum specifications. Additionally, testing of the grease indicated a high level of chromium, suggesting significant wear in the pivot pin bushing area due to a lack of adequate lubrication.
Findings
- The primary cause of the bogie beam fracture was stress corrosion cracking initiated by fatigue cracks that grew from pre-existing corrosion pits.
- These corrosion pits were present during the July 200 and were covered by protective layers, making them undetectable during standard visual inspections.
- The overhaul process failed to ensure the cadmium plating met the minimum thickness requirements at the critical cross bolt hole area.
- Evidence of wear in the pivot pin bushing contact area indicated a lack of sufficient lubrication.