What happened
On July 20, 2014, a Boeing 787-800 was descending toward Warsaw Chopin Airport (EPWA). While the aircraft was near the BIMPA waypoint, Air Traffic Control (ATC) instructed the crew to change the approach direction from runway 15 to runway 3/33. As the crew attempted to transition the Standard Terminal Arrival Route (STAR) from the BIMPA 3P to the BIMPA 4U procedure, the Flight Management System (FMS) lost all position indications. The crew requested vectors from ATC to runway 33 and subsequently completed the approach and landing under visual conditions. It remains unknown whether the FMS position data recovered following the landing.
The investigation
The investigation involved interviews with other Boeing 787 pilots during pre-flight briefings. These interviews revealed that similar loss of position indications had occurred previously, but because the indications typically restored themselves quickly, no Air Safety Reports (ASR) had been filed.
Software manufacturer Honeywell was able to replicate the error in a controlled environment. The investigation established that the software glitch specifically occurs during STAR procedures containing exactly 14 waypoints when the crew attempts to select an alternative approach not included in that specific procedure.
Findings
- The primary cause of the incident was limitations within the aircraft's onboard software systems.
- The error was linked to a specific logic failure in the FMS when handling certain waypoint counts during procedure transitions.
- The aircraft manufacturer and Honeywell worked toward a software solution via the Block Point 3 (BP3) modification, which included updates to the FMS, Thrust Management System (TMS), and Communication Management Function (CMF).