What happened
On February 27, 2017, at approximately 10:24 UTC, the crew of a Boeing 787-800, registration SP-LRF, flying flight LOT6523 from Warsaw to Mauritius, notified Bratislava ACC of a technical issue. The crew reported that the left engine was experiencing vibrations exceeding permissible levels and subsequently decided to return to Warsaw (EPWA).
Two minutes before crossing the national border, the crew requested permission to perform a 10-minute fuel jettison at flight level 330. This request was denied by Bratislava ACC. Following the crossing of the Polish border at 10:29 UTC, the fuel jettisoning process commenced and concluded at 10:38 UTC.
At 10:39 UTC, the crew reported 252 persons on board and an instantaneous fuel load of 29.5 tonnes, noting that no dangerous goods were being carried and that no emergency assistance was required for landing. Warsaw Tower declared a Level 1 alarm. The aircraft landed on runway 33 at 11:03 UTC and taxied to stand 45 by 11:08 UTC, after which the alarm was cancelled.
The investigation
The investigation focused on the technical failure of the propulsion system. Following the landing, maintenance personnel performed a borescope inspection of the left engine. This inspection revealed damage to the high-pressure turbine blades. As a result, the engine was flagged for replacement and sent for overhaul.
Findings
- The primary cause of the incident was damage to the high-pressure turbine blades in the left engine.