What happened
On May 1, 2022, a Cessna U206G, registration HK4228, was performing a non-scheduled passenger and cargo flight from Mitú to Camanaos, Vaupés. The aircraft, operated by America’s Air S.A.S., was flying under Visual Flight Rules (VFR) in clear weather conditions.
Upon landing at Camanaos Aerodrome, the aircraft followed a normal deceleration profile. However, as the aircraft slowed to approximately 10 knots while the pilot was applying brakes, the nose gear fork assembly suddenly fractured. The failure caused the nose gear assembly to detach, forcing the aircraft's nose downward. This resulted in the propeller striking the unpaved runway surface, causing an immediate engine stoppage and deformation of two propeller blades. The aircraft came to a halt on the runway. The pilot, the sole occupant, sustained one minor injury to the head.
The investigation
The GRIAA investigation focused on the structural integrity of the nose gear assembly. Investigators examined the fractured fork assembly (P/N: 1243610-28) and reviewed the aircraft's maintenance history. The investigation noted that while the aircraft's maintenance programs were up to date and complied with the manufacturer's supplementary inspection instructions, these instructions only required visual inspections rather than more advanced testing.
Technical analysis of the fracture site revealed evidence of porosity within the metal's microstructure. Investigators determined that the component had likely been subjected to repeated structural overloads due to frequent operations on unpaved, unprepared runways. These stresses, combined with the age of the component, contributed to a phenomenon of structural over-aging and potential material fatigue.
Findings
- The primary cause of the incident was the sudden fracture of the nose gear fork assembly, driven by structural over-aging and/or material fatigue.
- The component's mechanical ability to absorb loads had been significantly weakened by the accumulation of internal pores and micro-cracks over its service life.
- A contributing factor was the inadequacy of the existing maintenance program, which lacked Non-Destructive Inspection (NDI) processes. The absence of NDI prevented the detection of internal structural degradation that visual inspections could not identify, especially given the high-stress environment of unpaved runway operations.