What happened
On a scheduled flight from Toronto/Lester B. Pearson International Airport to Kingston, Jamaica, an Air Canada Boeing 767-233, registration C-GAUE, experienced a significant loss of airspeed and a high pitch attitude during its initial climb. Following takeoff in instrument meteorological conditions, the aircraft climbed through approximately 2,500 feet above sea level.
During the climb, the flight crew initiated a flight level change to 5,000 feet. As the aircraft transitioned into altitude capture (ALT CAP) mode, the autopilot was engaged. The aircraft's pitch increased to approximately 29.5°, causing the airspeed to drop significantly. The airspeed decreased to a minimum of 109 KIAS, triggering the stick shaker to alert the crew of an impending stall. The pilot flying eventually deactivated the autopilot and pushed the control column forward, successfully recovering the aircraft from the near-stall condition. There were no injuries to the 85 passengers or the seven crew members on board.
The investigation
The investigation examined the flight control computer software, the flight data recorder (FDR) data, and the crew's performance. Analysis of the FDR confirmed that the aircraft's pitch increased sharply while the airspeed decayed. The investigation also looked into the aircraft's flight control law configuration, noting that this specific aircraft was equipped with a software option that provided passive stall protection rather than active speed protection.
Investigators also reviewed the crew's monitoring of the flight instruments and their response to various cockpit warnings. Maintenance records were reviewed, and while a left angle-of $ ext{attack} $ vane sensor was replaced following the event, inspections found no anomalies with the sensor itself.
Findings
- The altitude capture profile was too aggressive for the aircraft's available energy, leading the autopilot to increase pitch to maintain the commanded altitude.
- The flight crew relied too heavily on automation, with the pilot flying focusing on engine gauges rather than scanning flight instruments.
- The pilot flying did not correctly interpret flight director and autopilot mode failure indications, such as the disappearance of command bars and the amber ALT CAP light.
- The captain did not adequately monitor the aircraft or the pilot flying, remaining unaware of the deteriorating flight conditions until the stick shaker activated.
- The crew failed to respond to multiple visual and aural warnings, including the master caution light and the aural stall warning.
- The autopilot was functioning according to its design specifications during the event.