On 1 March 2011, a QantasLink Bombardier Inc DHC-8-315,
registered VH-TQL, was conducting a regular public transport flight
from Tamworth Airport to Sydney Airport, New South Wales. The crew
were conducting a Sydney runway 16 left (16L) area navigation
global navigation satellite system (RNAV(GNSS)) approach in
Vertical Speed (VS) mode. The aircraft's stickshaker stall warning
was activated at about the final approach fix (FAF). The crew
continued the approach and landed on runway 16L.
The stickshaker activated at a speed 10 kts higher than was
normal for the conditions. The stall warning system had computed a
potential stall on the incorrect basis that the aircraft was in
icing conditions. The use of VS mode, as part of a line training
exercise for the first officer, meant that the crew had to make
various changes to the aircraft's rate of descent to maintain a
normal approach profile.
On a number of occasions during the approach the autopilot
pitched the aircraft nose up to capture an assigned altitude set by
the pilot flying. The last recorded altitude capture occurred at
about the FAF, which coincided with the aircraft not being
configured, the propeller control levers being at maximum RPM, and
the power levers at a low power setting. This resulted in a
continued speed reduction in the lead-up to the stickshaker
activation.
Each factor that contributed to the occurrence resulted from
individual actions or was specific to the occurrence. The
Australian Transport Safety Bureau is satisfied that none of these
safety factors indicate a need for systemic action to change
existing risk controls. Nevertheless, the operator undertook a
number of safety actions to minimise the risk of a recurrence.
In addition, the occurrence highlights the importance of
effective crew resource management and of the option of conducting
a go-around should there be any doubt as to the safety of the
aircraft. Transport Canada, which regulates the aircraft
manufacturer, advised that it will publish a summary of this
occurrence and recommend that operators consider using it in their
scenario-based crew resource management training programs.