ASN Wikibase Occurrence # 314356
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| Date: | Wednesday 17 October 2012 |
| Time: | 20:45 LT |
| Type: |  Boeing 737-838 (WL) |
| Owner/operator: | Qantas Airways |
| Registration: | VH-VXB |
| MSN: | 30101/1045 |
| Year of manufacture: | 2001 |
| Fatalities: | Fatalities: 0 / Occupants: |
| Aircraft damage: | None |
| Category: | Incident |
| Location: | near Canberra Airport, ACT (CBR) -
 Australia
|
| Phase: | Approach |
| Nature: | Passenger - Scheduled |
| Departure airport: | Adelaide Airport, SA (ADL/YPAD) |
| Canberra Airport, ACT (CBR/YSCB) | |
| Investigating agency: | ATSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
On 17 October 2012, a Boeing 737-838 aircraft, registered VH-VXB and operated by Qantas Airways, was conducting a flight from Adelaide, South Australia to Canberra, Australian Capital Territory. The flight crew received an approach clearance into Canberra via a standard arrival route (STAR) and then an Area Navigation (Required Navigation Performance) (RNAV (RNP)) instrument approach to runway 35 at Canberra Airport. Just prior to commencing descent, at about 2030 Eastern Daylight-saving Time, air traffic control (ATC) cancelled the STAR and cleared the aircraft to track direct to the initial approach fix, HONEY, via a high-speed descent. As the aircraft approached 8,000 ft, ATC provided a descent clearance to 7,000 ft and also cleared the aircraft for the approach. As the aircraft approached HONEY it descended below the 7,000 ft altitude clearance limit. After being alerted to this by ATC, the flight crew climbed the aircraft back to 7,000 ft and continued the approach to land.
The ATSB found that, as the aircraft approached 8,000 ft, the auto-flight system vertical mode changed from a flight management computer‑derived and managed vertical navigation mode into the vertical speed mode. This was followed by a number of automated, but unnoticed, and crew‑initiated changes in the aircraft’s auto-flight system vertical mode. The combination of auto‑flight system mode changes and the management of the airspeed during the descent resulted in a high workload environment where the 7,000 ft altitude clearance limit was overlooked by the flight crew.
The ATSB also found that, on receipt of the approach clearance, the Qantas RNAV (RNP) approach procedures allowed the flight crew to remove the current limiting altitude from the auto‑flight system’s Mode Control Panel (MCP) and set the decision altitude. Application of this procedure by the flight crew removed the last automated safety system available to them to prevent descent through the current altitude limitation, well before the aircraft was established on the approach.
Accident investigation:
 |
|
Sources:
NTSB DCA13WA012
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 02-Jun-2023 16:31 | ASN Update Bot | Added |
| 05-Aug-2023 10:05 | harro | Updated |
Corrections or additions? ... Edit this accident description
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