What happened
On August 26, 2023, at approximately 16:30 UTC, a Tecnam P92 Echo MKII, registration LV-S135, was performing a local recreational flight departing from Saladillo Aerodrome in Buenos Aires province. After 40 minutes of flight under visual meteorological conditions, the aircraft attempted to land on runway 18. Shortly after touchdown, the right main landing gear assembly failed, causing the aircraft to veer off the runway.
The aircraft sustained significant damage to the right main landing gear assembly, including a detached spring and a fractured attachment bolt. The right wing tip also sustained a bend, and there was minor damage to the fuselage. The pilot and one passenger both sustained minor injuries.
The investigation
The investigation conducted by the JST focused on the technical failure of the landing gear assembly. Metallurgical analysis of the fractured bolt revealed a significant fatigue mechanism. While the investigation identified isolated coarse-series D-type inclusions within the bolt material that could reduce fatigue resistance, the primary driver of the failure was identified as inverted bending loads acting on the component.
Investigators found that at the time of the accident, the aircraft's maintenance manual did not include specific procedures for detecting fatigue cracks in these main landing gear attachment bolts. Furthermore, a manufacturer-proposed modification (Job Card No. 1882) intended to alter the stress distribution around the bolt attachment points had not yet been implemented on this aircraft.
Findings
- The right main landing gear assembly failed immediately after ground contact due to the progressive fatigue of an attachment bolt.
- The aircraft was operating within approved weight and balance limits, and weather conditions were favorable.
- The existing maintenance practices at the time were insufficient for detecting the specific fatigue failure occurring in the gear assembly.
- The presence of material inclusions in the bolt material acted as a contributing factor to the reduction of the component's fatigue strength.