What happened
On 11 July 2022, a Socata MS8．80B, registration EI-BNU, was performing a private local flight at Navan Airfield. During the approach to Runway 27, the aircraft encountered a southerly crosswind. As the aircraft neared the grass runway, the sink rate increased, resulting in a hard touchdown.
During the subsequent ground roll, the left main landing gear failed. The aircraft veered toward the left side of the runway, causing the left main wheel to enter longer grass. This caused the left wing to drop and contact the ground surface. The pilot and one passenger were able to exit the aircraft without injury, and no fire occurred. The aircraft sustained substantial damage to the left main landing gear.
The investigation
The AAIU examined the aircraft's maintenance history and performed a metallurgical analysis of the fractured component. The investigation focused on the aluminum trailing arm of the left main landing gear.
Investigators reviewed the aircraft's maintenance programme, noting that while the maintenance manual contained instructions to check for cracks in the landing gear, these specific tasks were not included in the owner's declared periodic inspection programme. Furthermore, the investigation found that the manufacturer's Service Bulletin regarding landing gear inspections focused on the shock strut attachment rather than the trailing arms.
Findings
- The failure of the left main landing gear was caused by pre-existing fatigue cracks in the aluminum trailing arm, which combined with higher-than-normal landing loads during the touchdown.
- Metallurgical analysis identified two fatigue cracks, each approximately 1.5 mm deep, located on the upper part of the pivot bore.
- The fatigue cracks were likely a result of cyclic stress rather than a material defect.
- The aircraft's periodic inspection programme did not specifically require inspections for cracks on the trailing arms.
Safety action
- The AAIU issued a safety recommendation to the type-certificate holder, Daher, to consider amending the Periodical Inspections Chapter of the Maintenance Manual for the Socata MS880B and similar models to include specific requirements for inspecting the main landing gear trailing arms for cracks.