What happened
On 15 November 2016, a Bombardier BD-700-1A11 (Global 5000), registration VP-CKM, was conducting a private flight from Beijing to Hong Kong International Airport. During the arrival phase, the crew was navigating an approach to Runway 07L. While the aircraft was cleared to a minimum altitude of 1,700 ft amsl, it descended to as low as 390 ft amsl.
During the descent, the crew experienced several lapses in coordination. The co-pilot mistakenly referenced altitudes from a different approach type, and the commander disconnected the autopilot to fly the aircraft manually. This manual maneuver, involving a steep bank, caused the descent rate to accelerate to 3,600 fpm. As the aircraft neared the surface, the Terrain Awareness Warning System (TAWS) triggered multiple alerts, including "sink rate," "glideslope," and "pull up." The crew eventually initiated a climb and stabilized the aircraft above 1,000 ft amsl before landing safely.
The investigation
The AAIB investigation focused on the crew's performance, the aircraft's automation settings, and the operator's oversight. Investigators examined flight data from the FDR and cockpit voice recordings. The investigation established that the commander was suffering from acute fatigue, having had insufficient sleep prior to the flight. Furthermore, the investigation found that the crew failed to communicate critical changes in altitude selections and flight modes, leading to a loss of situational awareness. The investigation also looked into the operator's management of professional standards and the effectiveness of their Standard Operating Procedures (SOPs).