What happened
On February 23, 2010, an Embraer EMB-110P1, registration PT-SOG, was performing a taxi flight from Fazenda Paiaguás (SIXP) to Cuiabá (SBCY) in Mato Grosso, Brazil. The aircraft was carrying two crew members and 14 passengers.
During the landing roll on runway 35 at Cuiabá Airport, the aircraft began deviating to the left. The excursion lasted approximately five meters before the aircraft came to a stop. The commander took control of the aircraft in an attempt to correct the deviation. Upon stopping, the crew discovered that the left main landing gear strut linkage had disconnected, leaving the wheel free to rotate independently of the aircraft's direction.
All 16 people on board were uninjured, though the aircraft sustained light damage.
The investigation
CENIPA investigators examined the aircraft and analyzed photographs provided by the operator. The investigation revealed that the left wheel had been running misaligned with the aircraft's trajectory, evidenced by specific wear patterns on the tire.
Investigators found that the connection between the upper and lower parts of the landing gear strut had failed because the threads on the upper semi-strut could not withstand the tensile force applied to the connection bolt. This overload caused the threads to deform and strip.
However, the investigation was significantly hindered because the operator moved the aircraft and performed maintenance before notifying the regional investigation office (SERIPA VI). The degraded condition of the components due to subsequent maintenance made it impossible to determine the exact moment the cotter pin failed or the specific reason for the initial thread degradation. There was a possibility that a cotter pin, intended to prevent the rotation of the connection bolt, had detached previously, allowing the bolt to rotate during the compression and extension of the landing gear strut.
Findings
- The disconnection of the landing gear strut linkage caused the left wheel to rotate misaligned with the aircraft's path, creating higher friction on the left side and pulling the aircraft off the runway.
- The threads on the upper semi-strut failed due to an overload of tensile force.
- The failure to report the occurrence to the investigation authorities prevented a proper on-site inspection and compromised the ability to identify all contributing factors.