What happened
On January 1, 2020, an Airbus A350-941 arriving from Phuket, Thailand, was performing a night approach to runway 07R at Frankfurt/Main Airport under visual meteorological conditions. The flight was a scheduled passenger service carrying 306 passengers and 18 crew members.
During the approach, the aircraft failed to maintain a stabilized profile. While following a preceding aircraft, the flight crew began descending through the glideslope at a high rate of descent. By approximately 3,300 ft AMSL, the aircraft was continuously undershooting the glide path. As the aircraft reached an altitude of 668 ft AGL, approximately 6 NM from the runway threshold, the crew recognized the unstable approach and initiated a go-around maneuver.
The investigation
The BFU investigation examined the flight data recorder (FDR) and cockpit voice recorder (CVR) to reconstruct the sequence of events. The analysis focused on the automation modes, including the Flight Mode Annunciator (FMA) transitions, and the crew's performance during the approach. The investigation also reviewed the Flight Management System (FMS) programming and the communication between the pilots, noting that much of the cockpit discussion regarding the approach was conducted in Thai.
Findings
Several contributing factors led to the unstable approach:
- Errors in FMS programming regarding the established waypoints.
- Improper use of the automated flight control system during the approach phase.
- Reduced situational awareness of the flight crew regarding the aircraft's position in space.
- Deficiencies in cockpit communication and crew coordination.
The aircraft's descent rate increased significantly, reaching over 3,000 ft/min, and the deviation from the glideslope exceeded 4 dots before the go-around was executed.