Cobham B712 at Perth on Jun 1st 2012, aborted go-around
Last Update: October 12, 2015 / 15:49:29 GMT/Zulu time
The Australian TSB reported the crew commenced an unstable approach following the initiation of the go-around and continuation of approach and have opened an investigation.
On Oct 12th 2015 the ATSB released their final report concluding the probable causes of the incident were:
- The weather forecast for Perth Airport was amended to include the requirement to carry sufficient fuel to divert to a suitable alternate aerodrome when the aircraft no longer had that amount of fuel remaining.
- The captain, as the flying pilot, continued an approach to land after the approach had been destabilised by initiating a go-around procedure.
Other factors that increased risk
- The flight crew did not update the weather forecast for Perth Airport en route which, although in this instance did not indicate an operational requirement, was a missed opportunity to update pertinent operational information prior to the aircraft being committed to its destination.
- Given the circumstances, when confronted by a choice between completing the missed approach with an indeterminate outcome and landing from a discontinued missed approach, the captain chose the option that was considered to represent lower risk.
- The operator’s procedures in the case of an unstabilised approach were unambiguous and reflected those promoted by the Flight Safety Foundation.
The ATSB reported that prior to departure the crew obtained the weather information including weather forecasts, which did not contain any indication that a weather related diversion could become necessary, as such the aircraft was not required to carry fuel for such a weather related diversion to an alternate aerodrome.
The ATSB wrote: "Despite the lack of a requirement to provide for an alternate for Perth, the aircraft was carrying sufficient fuel to allow for the flight to be diverted to Kalgoorlie until shortly after commencing descent into Perth. Beyond that time, the aircraft was no longer carrying sufficient fuel to divert to another suitable aerodrome."
The crew did not update the weather information while enroute. Descending towards Perth, at 11,000 feet, air traffic control informed the crew of deteriorating visibility at Perth and the first officer noticed a thin layer of cloud between the coast and the aerodrome. The aircraft maneouvered onto an ILS approach to runway 03. While established on the localizer and glideslope the aircraft flew through patches of cloud until descending below 1000 feet AGL, where it entered continuous cloud.
Descending through 320 feet, decision height, the first officer, pilot monitoring, called "nil sighting", the captain, pilot flying, called "go around" and initiated the go around by pressing the go-around button and advancing the thrust levers. Immediately after, before any further actions could be done, the aircraft flew clear of the cloud and visual contact with the runway was established. The captain called "landing", disconnected autopilot and autothrust and manually landed the aircraft without exceeding and flight or landing tolerances.
The ATSB wrote: "The captain later reported being concerned about the unforecast weather deterioration with limited fuel remaining, and not knowing if the weather would deteriorate further after going around and repositioning for a second attempted approach and landing. He reported that this concern influenced his decision to land after initiating the missed approach, during which the aircraft exceeded the operator’s stabilised approach criteria for a landing."
The ATSB analysed: "The aerodrome and trend forecasts for Perth Airport did not predict weather conditions that required the carriage of sufficient fuel to fly to a suitable alternate landing airport, until after the aircraft no longer had sufficient fuel to divert to a suitable alternate aerodrome. This committed the crew to landing at Perth where a safe landing could no longer be assured. In the few minutes before landing, the flight crew observed a rapid deterioration in the weather conditions, and their observations were reinforced by information heard on the aircraft radio. The flight crew were confronted with rapidly deteriorating unforecast weather conditions, and uncertainty about how much further the weather might deteriorate."
The ATSB analysed with respect to weather: "Weather observations do not predict expected weather conditions. In contrast, a weather forecast is intended to provide the best approximation of future weather conditions. Knowledge of any changes to forecast weather at the destination is assured when flight crews request or obtain the latest version of the relevant forecast. For safety purposes, the most relevant time to ensure that the destination’s forecast weather remains suitable for an assured landing is shortly before the aircraft no longer carries sufficient fuel to divert to an alternate aerodrome where a landing can be assured. The crew had a reasonable knowledge of the point in the flight when they were committed to a landing in Perth because of the fuel remaining, and an amended forecast was not issued for Perth Airport before this time. However, by not confirming the latest weather forecast for Perth, and its potential effect on the flight, the crew could not assure themselves of the validity of that understanding."
With respect to approach and landing the ATSB analysed: "The flight crew commenced the instrument landing system (ILS) approach to runway 03 and encountered unforecast and rapidly deteriorating weather, the extent and duration of which was unknown. Similar instrument approaches were available to runways 21 and 24 that allowed for landing in slightly worse weather conditions, but the time taken to change to either of these approaches would, given the traffic situation, have impacted further on the crew’s now less-than-ideal fuel situation. In the event, the captain was confronted with a short-notice choice between completing the missed approach, with an indeterminate outcome, and landing from a discontinued missed approach. He was aware of the risk associated with continuing the landing in what amounted to an unstabilised configuration, but considered this option represented lower risk."
YPPH 311700Z 03006KT 0900 FG OVC001 16/16 Q1017
YPPH 311630Z 01006KT 0900 FG BKN002 16/16 Q1017 RMK WBD 0.2 FM1630 VRB03KT 0300FG
YPPH 311605Z 03005KT 9999 BKN004 BKN011 16/15 Q1017 RMK WBD 0.3 BR FM1605 VRB03KT 9999 BKN005 FM1700 VRB03KT 0300 FG
YPPH 311600Z 03006KT 9999 SCT004 BKN012 16/15 Q1017 RMK WBD 0.3 FM1600 VRB03KT 9999 BKN008 FM1730 VRB03KT 0300 FG
YPPH 311530Z 03006KT 9999 FEW012 16/15 Q1017 RMK WBD 0.4
YPPH 311522Z 03007KT 9999 FEW011 16/15 Q1017 RMK WBD 0.4 FM1530 VRB03KT 9999 BKN008 FM1730 VRB03KT 0300 FG
YPPH 311500Z 03005KT 9999 FEW010 BKN016 16/16 Q1017 FM1500 VRB03KT 9999 BKN008 FM1730 VRB03KT 0300 FG
VRB03KT 9999 BKN008 FM1730 VRB03KT 0300 FG
YPPH 311430Z 01006KT 9999 -SHRA FEW012 BKN022 BKN035 16/16 Q1017 RMK WBD 0.3
YPPH 311400Z 03007KT 9999 FEW015 SCT025 BKN039 16/16 Q1017 RMK WBD 0.4
This article is published under license from Avherald.com. © of text by Avherald.com.
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