What happened
On December 13, 2010, a Cessna 402B, registration PT-IUQ, was performing a scheduled armored transport flight from Fortaleza, CE, to Picos, PI. The flight was operating under Visual Flight Rules (VFR) in calm weather conditions.
Upon landing at Picos Aerodrome (SNPC) on runway 14, the aircraft initially followed a normal touchdown sequence. However, during the landing roll, the right main landing gear unexpectedly retracted. This caused the right wing and propeller to strike the ground, leading to a loss of directional control. The aircraft veered off the right side of the runway, eventually coming to a stop 90 degrees from its original heading, approximately 5 meters from the runway edge. All three occupants—the pilot and two passengers—were uninjured, though the aircraft sustained severe damage to the propellers, wing structure, fuselage, and landing gear components.
The investigation
CENIPA investigators focused on the mechanical failure of the landing gear system. Laboratory analysis conducted by the Institute of Aeronautics and Space (IAE) examined the broken bellcrank of the right main landing gear. The microscopic examination revealed that the threaded eyelet of the component had deformed, and the fracture pattern indicated a failure caused by overload.
The investigation also scrutinized the maintenance history of the aircraft and the condition of the aerodrome. Investigators found that the maintenance facility (CETAM) had failed to fully implement the periodic and geriatric maintenance programs required by the manufacturer for this aircraft model. Specifically, there was a lack of traceability regarding the landing gear torque tube assembly and a lack of specialized tools required to measure stress points in the landing gear system. Additionally, the investigation noted that recent paving work at the aerodrome had left loose stones on the runway shoulder, which likely exacerbated the damage during the excursion.
Findings
- The primary cause of the gear retraction was the overload-induced fracture of the right main landing gear bellcrank.
- Inadequate maintenance supervision and failure to adhere to the manufacturer's specialized maintenance program prevented the timely detection of fatigue or wear in the landing gear components.
- The presence of loose stones and irregular terrain on the runway shoulder contributed to the severity of the aircraft damage.
- The possibility of a previous hard landing or operating the aircraft beyond its weight envelope was considered a potential contributing factor to the component failure.