What happened
On March 2, 2016, a Boeing 787-800 operated by PLL LOT SA was being pushed back from its parking stand at Warsaw Chopin Airport (EPWA) to begin flight LO79. During the taxi phase, the flight crew discovered that the control column was locked and the elevator was unmovable. The aircraft was subsequently returned to its parking position.
Following the discovery, a maintenance team arrived to assess the defect. During this period, a mechanic from the maintenance provider, LOT AMS, entered the forward electronics bays and removed the control column locking pins without notifying the crew on board. The mechanic then informed the team that the issue was resolved but declined to record this specific action in the aircraft maintenance logs.
The investigation
The PKBWL investigation established that the aircraft had undergone a maintenance check at LOT AMS between February 29 and March 2, 2016. During this period, specifically on February 29, maintenance tasks required the use of E1 and E2 rig pins to check elevator deflections.
The investigation found that the unremoved elevator control locks were the direct cause of the flight control restriction. It was further determined that the rig pins, part of a Boeing kit, were stored loosely within their container, making it difficult to verify if the set was complete after use. Additionally, the investigation highlighted a failure in quality control and a breach of established maintenance procedures regarding tool usage and task completion documentation.