What happened
On August 23, 2014, while operating at Warsaw Chopin Airport (EPWA), a Boeing 787-800 experienced a significant failure of the Flight Management System (FMS) Lateral component (FMCL). The incident occurred while the crew was attempting to modify an approach via the Control Display Unit (CDU). The malfunction resulted in the immediate loss of the active route, performance data, autopilot, autothrottle, and both VNAV and LNAV capabilities.
To restore functionality, the crew had to manually reprogram the FMC. The investigation noted that the system initially resisted any modifications, and the crew only succeeded in restoring the necessary data after multiple programming attempts. The pilot reported that this specific type of failure had occurred three times in the weeks preceding the incident.
The investigation
The investigation focused on the software performance of the aircraft's onboard systems. The software manufacturer, Honeywell, was able to replicate the reported issue during testing. It was determined that the failure specifically occurred during STAR (Standard Terminal Arrival Route) procedures containing exactly 14 waypoints when the crew attempted to select an approach not included in that specific procedure.
While the operator engaged in negotiations with Boeing to accelerate a permanent fix, the manufacturer's proposed solution was not scheduled for implementation until late 2015. The investigation tracked the subsequent release of Service Bulletin B787-81205-SB340013-00, which eventually introduced the necessary software modifications for the Flight Management System, Thrust Management System, and Communication Management Function via the Block Point 3 (BP3) update.