What happened
On May 23, 2017, during a routine verification of technical logbook entries at the Warsaw (EPWA) maintenance base, it was discovered that a Boeing 737 operated by PLL LOT S.A. had exceeded its authorized flight hour limit for a permanent repair. The aircraft required a permanent repair to the right-hand inboard midflap following the discovery of a crack during a hangar inspection on May 6, 2017. The manufacturer had granted a temporary authorization for the aircraft to operate for a maximum of 100 flight hours (FH) following the initial discovery. However, by the time the discrepancy was identified, the aircraft had exceeded this limit by 14.51 flight hours.
The investigation
The investigation focused on how the flight hour limitation was not properly tracked within the airline's maintenance management systems. It was established that the maintenance organization used AMOS for defect logging, which then interfaced with the TRAX system (the airline's CAMO IT system). While the defect was correctly logged in AMOS, the specific technical authorization (ADD7038) regarding the flight hour limitation failed to transfer to the TRAX system.
During a manual verification of work package summaries on May 11, 2017, a maintenance employee incorrectly closed the defect in the TRAX system. This error occurred despite the fact that the information regarding the defect was present in the source system, leading to a lack of visibility regarding the expiring flight hour limit in the primary tracking system.