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A late-night mistake by flight crew led to an unstable approach on an Alliance Embraer E190, the ATSB has found.
VH-UZI (pictured) was operating QantasLink flight QF1887 from Cairns to Brisbane at about 10:43pm on 9 May last year when the captain disengaged the autopilot for a manual approach, and asked the first officer to adjust the flight path reference line on the primary flight display.
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While the plane was stabilised on the runway 19L instrument landing system (ILS) approach at the time, the approach became unstable after the first officer accidentally pressed the wrong button, said ATSB Director Transport Safety Stuart Macleod.
“The first officer had a correct understanding of the situation, but inadvertently pushed the flight path angle button – a ‘slip’ type error, which unintentionally disengaged the ILS approach mode,” he said.
Surprised by the mode change, over the next 10 seconds the flight crew focused on resolving it, rather than conducting a go-around.
“During this time, the pilots were not effectively monitoring the aircraft’s flight path, and it exceeded the glideslope limit requirement of the operator’s stabilised approach criteria,” said Macleod.
Once the captain identified the aircraft was low, they began to increase pitch, but at this time, the enhanced ground proximity warning system (EGPWS) generated a glideslope warning, in response to which, as it was night, the operator’s procedures required the flight crew to perform the operator’s terrain avoidance manoeuvre.
Subsequently, the flight crew instead continued the approach and landing.
Macleod said the incident highlights how quickly a disruption can result in an aircraft transitioning from a stable to unstable approach.
“When pilots are faced with unexpected events, effective crew resource management, with each crewmember performing their procedurally assigned roles of flying and monitoring, is essential to ensuring the continued safety of flight while the disruption is investigated and managed,” he said.
“Early recognition of an unstable approach and prompt execution of a go around, rather than continuing the approach, significantly reduces the risk of approach and landing accidents.
“Further, flight crews must also execute the correct response to ground proximity warning systems alerts without hesitation to ensure obstacles or terrain are avoided.”
In response to the incident, Alliance Airlines has amended its cyclic training program, issued a relevant Operational Notice, and conducted a thematic review of unstable approaches, analysing data for further review.
