What happened
On May 27, 2005, a de Havill and DHC8-100 (registration C-GZKH) was operating a scheduled passenger service from St. John's to Deer Lake, Newfoundland and Labrador. The flight was carrying 36 passengers and 3 crew members. Following a routine takeoff, the aircraft entered a right climbing turn, during which the captain engaged the autopilot.
As the aircraft climbed, the airspeed began to decline steadily. The flight crew did not notice the decreasing speed, partly because the first officer was occupied with departure paperwork and the autopilot was maintaining a constant rate of climb. At approximately 14,000 feet, the aircraft entered an aerodynamic stall. The aircraft lost 4,200 feet in a rapid, uncontrolled descent before the crew managed to recover the aircraft approximately 40 seconds later. There were no injuries and no damage to the aircraft.
The investigation
The investigation focused on the flight control settings and the environmental conditions during the climb. Data from the flight data recorder (FDR) revealed that while the crew intended to fly in airspeed-hold mode, the autopilot was actually set to vertical speed (VS) mode. This error went uncorrected because the airline's standard operating procedures (SOPs) did not require the crew to announce or confirm the specific autopilot mode selection.
Investigators also examined the aircraft's anti-ice configuration. Although the aircraft was climbing through freezing temperatures, the crew had elected to leave the pneumatic de-icing boots turned off. Because the aircraft lacked an electronic ice detector, the crew relied on visual inspections, which failed to identify ice buildup on the wing leading edges.
Findings
- The captain inadvertently selected vertical speed mode instead of airspeed mode on the automatic flight control system, an error that went undetected by both pilots.
- The airline's standard operating procedures lacked a requirement to verify or communicate the selection of autopilot climb modes.
- The crew failed to activate the pneumatic de-icing boots while flying in icing conditions.
- Ice accumulation on critical flight surfaces likely caused the stall to occur at a higher airspeed than expected, providing the crew with minimal warning.
- The captain misidentified the symptoms of the stall as severe turbulence and attempted to pull the nose up, which worsened the stall and increased the altitude loss.
- The first officer's focus on administrative paperwork during the climb contributed to the failure to monitor the aircraft's airspeed.
Safety action
Following the incident, the TSB issued safety advisories regarding the importance of verifying autopilot mode selections and the timely use of de-icing equipment. In response, the operator updated its procedures to include a challenge and response protocol for autopilot engagement and prohibited paperwork during critical flight phases. Additionally, Transport Canada released new guidance regarding stall recovery training practices.