What happened
On July 16, 2018, a 737-8EH, registration PR-GGD, operated by Gol Airlines, was performing a scheduled passenger flight from Congonhas Aerodrome (SBSP) to Tancredo Neves Aerodrome (SBCF) in Belo Horizonte. The aircraft was carrying 136 passengers and six crewmembers.
Upon touchdown at SBCF, the cabin crew reported hearing a loud, abnormal noise. The aircraft was able to taxi to the apron under its own power, and all passengers disembarked without injury. However, a subsequent post-flight inspection by the maintenance team revealed a significant hydraulic fluid leak and structural damage to the right main landing gear assembly. The investigation confirmed that a component of the landing gear had broken, leading to damage to the wing stringer and the aft pressure bulkhead sealant.
The investigation
CENIPA investigators examined the right main landing gear assembly and the history of the components involved. The investigation focused on the aft trunnion pin, a part made of 4/340M steel alloy. The technical analysis revealed that the aft trunnion pin had fractured, which subsequently caused damage to the aft trunnion bearing and the aircraft's wing structure (stringer).
Investigators scrutinized the maintenance history of the landing gear, noting that the component had undergone a general overhaul at a maintenance organization (TAPME). The research focused on the grinding process used during the overhaul of the chrome-plated surface of the pin. The investigation also reviewed the effectiveness of various inspection methods, such as magnetic particle and dye penetrant inspections, in detecting subsurface damage caused by thermal effects during maintenance.
Findings
- The primary cause of the accident was the fracture of the aft trunnion pin on the right main landing gear.
- The fracture was likely caused by a burn in the base metal of the pin, which occurred during an overhaul process due to excessive grinding of the chromium layer.
- The quality control inspections following the grinding of the chrome-plated part were not effective in detecting the heat-induced damage (burning) to the underlying steel.
- The maintenance documentation provided to technicians may have lacked sufficiently clear guidelines or criteria for performing effective visual inspections of these specific components.