What happened
On March 1, 2010, an Airbus A300 B4, registration TC-ACB, operated by ACT Airlines, was conducting a cargo flight from Bahrain to Bagram, Afghanistan. During the final approach to runway 21, the crew extended the landing gear and immediately heard an abnormal noise accompanied by vibrations. The crew noted that only two of the three green landing gear lock indicators were illuminated, specifically indicating that the left main landing gear had failed to lock.
Shortly after, the green hydraulic system pressure and level dropped to zero. The crew declared an emergency and performed two low-altitude passes to verify the gear position, which appeared normal to air traffic controllers. During the landing roll, the left main landing gear collapsed toward the rear. The aircraft veered off the left side of the runway and came to a stop on a dirt strip approximately 2,000 meters beyond the runway threshold. All five crew members evacuated the aircraft without injury, though the aircraft sustained heavy damage.
The investigation
The investigation focused on the structural failure of the left main landing gear side brace. Investigators examined the wreckage and analyzed maintenance records from Turkish Technic, where the gear had undergone a major overhaul between April 2008 and March 2009. The inquiry included laboratory examinations of the broken components in France.
Investigators scrutinized the maintenance documentation, specifically the Component Maintenance Manual (CMM) provided by the gear manufacturer, Messier-Bugatti-Dowty. The investigation revealed that the workshop's work cards and follow-up sheets were incomplete and did not strictly adhere to the required manufacturer specifications for several critical steps, including visual inspections and specific chemical processes.
Findings
- The primary cause of the accident was a fatigue fracture of the left main landing gear side brace.
- The fatigue crack likely originated from a corrosion pit that was either newly formed or went undetected during the previous major overhaul.
- Maintenance deficiencies were identified during the overhaul at Turkish Technic; specifically, several mandatory tasks—such as detailed inspections of the side brace journals and certain stages of the cadmium plating process—were missing from the workshop's task cards.
- The investigation concluded that the complexity of the manufacturer's maintenance documentation required a level of rigor and expertise that was not adequately maintained, leading to the use of inadequate and incomplete maintenance instructions.