What happened
On September 2, 2021, at 02:55 UTC, a Boeing 787-8 operated by PLL LOT was landing at Incheon International Airport (RKSI) in Seoul, South Korea. During the landing roll, the flight crew attempted to deploy the thrust reversers on both engines; however, the reversers failed to open despite multiple attempts. The aircraft was able to decelerate safely using the runway and subsequently utilized a taxiway to bring the aircraft to a complete stop.
The investigation
The investigation reviewed documentation provided by the maintenance organization and technical inspection records performed by Korean Airlines. The inquiry focused on the maintenance procedures performed on the engines prior to the flight. The investigation established that personnel responsible for the deactivation and activation of the thrust reversers failed to adhere to the required maintenance documentation. Specifically, lockout pins used during the deactivation process were not marked with identification flags after installation. Consequently, these pins went unnoticed by personnel closing the access panels. Because the pins remained in the modules, the thrust reversers could not be engaged for flight.
Furthermore, the investigation found that following the improper deactivation, the maintenance staff did not complete the full activation procedure (Trust Reverser for Ground Maintenance – Activation DMC-B787-A-R78-31-00-20G-730BA). A recommended functional test of the reversers was not performed, which would have revealed that the blocking pins were still installed.
Findings
- Failure to follow maintenance procedures regarding the marking and removal of lockout pins.
- Incomplete activation procedure for the thrust reversers following maintenance tasks.
- Omission of a functional test that would have identified the presence of the blocking pins.
- Lack of a permanently designated coordinator for aircraft maintenance tasks.
- Improperly prepared maintenance execution documentation.
Safety action
Following the incident, several preventive measures were implemented:
- Materials from the investigation are being used in periodic training for this aircraft type.
- A Safety Bulletin derived from the event has been placed on an e-learning platform for mandatory review by maintenance personnel.
- Maintenance execution documentation regarding thrust reverser deactivation is being revised to prevent the use of incorrect tools and to ensure independent inspections are not bypassed.
- The certification privileges of the personnel involved in the maintenance task were suspended pending the full resolution of the investigation.