What happened
On July 14, 2011, a Mitsubishi MU-2B-60, registration PT-LHH, was performing an aeromedical transport flight from Salvador to Ilhéus, Brazil. The aircraft was carrying two pilots, a physician, and a nurse.
During the landing at Ilhéus Aerodrome (SBIL) at approximately 21:35 local time, the aircraft touched down on the runway. Following the touchdown, the pilot lost directional control of the aircraft, causing it to veer off the left side of the runway. During the excursion, the nose gear struck a runway edge light support. The aircraft traveled approximately 50 meters across the grass, where the left engine propeller blade struck the ground, and the right nose gear wheel became detached. The aircraft sustained grave damage to the nose gear assembly, doors, left wing, and tip tank, while the occupants remained uninjured.
The investigation
CENIPA investigators examined the wreckage and the aircraft's maintenance records. Technical analysis by the Institute of Aeronautics and Space (IAE) focused on the fractured components of the nose gear, specifically the trunnion pin and the upper torque link assembly. The investigation also reviewed the operator's maintenance history, noting a pattern of tire pressure issues in the fleet.
Investigators evaluated whether the failure was due to fatigue or an external overload. The analysis of the fracture surfaces indicated that the failure was caused by an overload rather than material fatigue. The investigation also looked into the possibility that improper wheel hub assembly or inadequate pre-flight inspections contributed to the unstable condition of the aircraft's landing gear and tires.
Findings
- The primary cause of the loss of control was the structural failure of the nose gear trunnion pin and upper torque link assembly due to an overload.
- This overload was likely triggered by a forced command by the pilot to bring the nose gear into contact with the ground, occurring simultaneously with the application of the right main gear brake.
- The left main gear tire was found to be completely deflated at the time of the accident.
- There was evidence of inadequate systematic monitoring of tire pressure and potential issues with the assembly of wheel hubs within the operator's maintenance procedures.
- The investigation could not rule out that the crew failed to identify the low tire pressure during the pre-flight external inspection.