What happened
On September 23, 2016, during a scheduled C14+CPCP+15MO maintenance inspection at the LOTAMS technical base (EPWA), technicians discovered structural damage to a component. The inspection revealed severe cracks in the middle left internal flap rib (P/N 65C2GES10-25, S/N 2054). This specific component had been removed from the Boeing 737-400 aircraft registered as SP-LLF.
Upon discovery of the damage, the faulty flap rib was replaced with a new unit. The operator, PLL LOT SA, was notified of the findings by the LOTAMS maintenance facility.
The investigation
The investigation was conducted by the operator's internal team. The process focused on the inspection findings at the technical base and the condition of the component removed from the aircraft.