What happened
On May 13, 2021, a Cessna 208B Caravan was conducting a skydiving operation at the Los Cuatro Diablos Aerodrome (SCME) in Melipilla, Chile. During the initial takeoff roll, the pilot experienced a loud impact from the landing gear, which was attributed to the unpaved surface of the airfield. Following the takeoff, the pilot noted that the right rudder pedal felt heavy, suggesting a potential mechanical issue.
To mitigate risk, the pilot completed the jump mission at 13,0-000 feet before returning to the aerodrome. During the landing on runway 26, the pilot utilized aerodynamic braking by keeping the nose wheel elevated as long as possible. While performing a 180-degree left turn on the runway to taxi back to the apron, a second heavy impact occurred. This caused the nose gear fork to disconnect, leaving the aircraft immobilized on the runway. The pilot and one passenger were uninjured, though the aircraft sustained significant damage to the nose gear assembly.
The investigation
DGAC Chile investigators examined the aircraft's maintenance records and the physical condition of the landing gear. The investigation focused on the two bolts securing the nose gear fork. Laboratory analysis of the components revealed two distinct failure modes. One bolt exhibited a brittle fracture characterized by fatigue striations, indicating that cracks had been progressing through the material over time due to cyclic dynamic loads. The second bolt showed a ductile fracture resulting from excessive tensile and lateral loading.
Investigators also reviewed the aircraft's maintenance program, noting that the specific bolts in question were managed on an "on-condition" basis, meaning they were not subject to scheduled periodic inspections. The investigation confirmed that the aircraft's maintenance was up to date and compliant with all approved programs.
Findings
- The primary cause of the incident was the fracture of the nose gear fork bolts, which resulted in a loss of directional control.
- One bolt failed due to material fatigue caused by the cyclic dynamic loads inherent in landing and taxiing operations.
- The second bolt failed due to excessive stretching and traction forces during the aircraft's turn on the runway.
- The maintenance program did not require specific inspections for these bolts, making the fatigue-related crack difficult to detect through standard procedures.