Australia's air safety investigator has highlighted the risks associated with landings following an unstable approach incident involving a Skippers Aviation Bombardier Dash 8 Q300 last year.
On 17 May 2012, the crew of the aircraft, registered VH-XFZ, was approaching Laverton aerodrome in Western Australia after departing from Perth, the Australian Transport Safety Bureau (ATSB) says in a report on the incident.
“In conditions of low cloud, the crew positioned the aircraft on a close base leg to maintain visual reference with the runway threshold,” says the ATSB.
“This led to a steep final approach and a high rate of descent that triggered alerts from the aircraft’s enhanced ground proximity warning system (EGPWS) and exceeded the operator’s stable approach criteria. The crew heard some alerts from the EGPWS and knew they had a high rate of descent but at the time did not identify an unstable approach. The crew continued the approach and landed.”
Upon landing, the crew discussed the landing, but were unsure whether the aircraft had been stabilised at the operator’s minimum stabilisation height of 300ft (90m). They did not report the incident at the time. A week later, however, Skippers’ chief pilot learned about the EGPWS warnings, and reported it to the ATSB, which commenced an investigation.
The ATSB attributed the incident to a heightened crew workload given the low cloud conditions, which impacted the crew’s situational awareness as both pilots were focused outside the cockpit at the runway.
“The crew’s monitoring of the aircraft’s rate of descent and altitude relative to the minimum stabilisation height was secondary to their monitoring of their position in relation to the ground,” says the report. “This external focus degraded the crew’s overall situation awareness. The increased cognitive workload may also have interfered with the crew’s perception of the risk involved.”
The ATSB recognised no organisational issues with Skippers that contributed to the incident, but says the operator has taken a number of safety actions.
Following the incident, the crew involved competed a ground and flight re-training package. All crews received a memorandum reiterating procedures following an EGPWS warning, and meetings were held with crews to discuss stabilised approach criteria.
Skippers also amended its stabilised approach criteria, and incorporated an EGPWS warning event into its Dash 8 simulator training programme.
According to Flightglobal’s Ascend Online Fleets database, VH-XFZ entered service in 1993 with Germany’s Augsburg Airways, and was purchased by Skippers in 2008.
Skippers specialises in resource charter operations in Western Australia, and also has a limited scheduled network.