Virgin Australia B738 at Sydney on Jun 4th 2013, went through localizer and caused loss of separation
Last Update: August 10, 2015 / 12:55:56 GMT/Zulu time
A Jetstar Airbus A320-200, registration VH-VFL performing flight JQ-423 from Coolangatta Gold Coast,QL to Sydney,NS (Australia), was on final approach to Sydney's runway 16L on an independent parallel visual approach.
The Australian TSB reported that after receiving clearance for the visual approach to runway 16R both Virgin crew were confident the APP push button had been pressed and the autopilot would thus intercept the localizer, neither of the pilots referred to the announciators to cross check whether the approach mode had indeed been armed. Consequently the aircraft continued to track through the localizer until a TCAS traffic advisory alerted the crew to another aircraft in close proximity soon followed by a resolution advisory to descend, the crew disconnected the autopilot, complied with the TCAS instruction to descent, turned the aircraft to intercept the localizer from now the other side and continued the approach for a safe landing about 3 minutes later.
The Jetstar crew rceived a TCAS resolution advisory to climb, aborted their approach, were instructed to fly basically a 360 and continued for a safe landing on runway 16L about 9 minutes later.
Australia's Transport Safety Board (ATSB) rated the occurrence a serious incident and opened an investigation estimated to conclude by March 2014.
Radar data suggest, the separation between the aircraft reduced to zero feet vertical and about 1.0nm lateral, later 500 feet vertical and 0.5nm lateral.
On Aug 7th 2015 the ATSB released their final report concluding the factors into the serious incident were:
- The flight crew applied insufficient force to the approach mode push-button on the mode control panel to arm the mode, which was not identified during their subsequent check of the flight mode annunciator.
- Due to their expectation that the aircraft approach mode was armed, and a subsequent degradation in monitoring the aircraft’s systems, the flight crew did not anticipate that the aircraft’s automated systems would not capture the runway 16R localiser and did not immediately detect the flight path deviation.
- The flight crew did not recognise that the traffic advisory alert provided by the aircraft’s traffic collision avoidance system 12 seconds prior to the aircraft passing through the runway centre-line was a potential indication of a problem with the aircraft’s flight path.
Other factors that increased risk
- The Virgin Australia procedures did not require its flight crew to, whenever practicable, announce flight mode changes. [Safety issue]
- Air traffic control did not, and was not required to provide traffic information to aircraft using adjacent runways and abeam each other during independent visual approach procedures at Sydney. [Safety issue]
- Relative to other approaches or flight operations, there is a relatively high rate of traffic collision avoidance system resolution advisory alerts during independent visual approaches at Sydney Airport.
In addition the ATSB released following safety message:
During an IVA (independent visual approach), accurate interception and tracking of the runway centre-line is essential to maintain separation with aircraft using the parallel runway. This occurrence highlights the importance of pilots remaining vigilant during this type of approach, including to the consideration of and response to all RAs. The importance of crews conducting comprehensive checks of the mode control panel and flight mode annunciator to ensure that the flight mode selected is consistent with the crew’s intention is also reinforced.
The ATSB analysed: "While conducting an independent visual approach (IVA) to runway 16R at Sydney Airport, the flight crew of a Boeing 737 (737), registered VH-YIR and operated by Virgin Australia (Virgin), passed through the runway centre-line as an Airbus A320 aircraft, registered VH-VFL, was conducting an IVA to parallel runway 16L. Both flight crews received a traffic advisory (TA) followed by a resolution advisory (RA) through their aircraft’s traffic collision avoidance systems (TCAS) and acted in accordance with their respective RA instructions. At that time, the 737 captain realised they were passing through the extended runway 16R centre-line and disengaged the autopilot before manually flying the aircraft back towards the centre-line. The flight crew then armed the approach mode, which captured the localiser course. The flight crew of the A320 performed a go-around, and both aircraft landed safely. Although the occurrence was far from developing into a collision, and both aircraft were in visual meteorological conditions, this analysis examines the crew actions and IVA procedures at Sydney Airport and their influence on the development of the occurrence."
With respect to flight mode awareness the ATSB analysed: "Although it seems logical that a pilot would check the FMA, research has shown that they do not always do so, even when flight crews are required to call out auto-flight mode changes (Björklund and others 2006). Other research has suggested that 32 per cent of pilots do not observe the FMA within the first 20 seconds of a manually-selected mode change (Mumaw and others 2001). ... In this occurrence, it was found that, contrary to their intentions, the 737 flight crew did not arm the approach mode, probably as a result of applying insufficient force to the mode push-button. Subsequently, the crew’s check/confirmation, if any, of the mode change using either the MCP or FMA was ineffective. This meant the crew’s belief of their selection of the approach flight mode led to an incorrect expectation that the aircraft would automatically capture the localiser. Virgin did not mandate that its crew announce mode changes at the time of the occurrence. Despite the absence of this procedural requirement, the 737 captain made a verbal call announcing their selection of the approach mode. However, the flight crew did not effectively verify via the FMA display that approach mode was armed."
The ATSB analysed with respect to flight path monitoring: "As the 737 turned on final to intercept the extended runway 16R centre-line, the flight crew expected that the aircraft’s autopilot system would capture the localiser via the automated approach mode. As the flight continued, the flight crew did not anticipate that the aircraft was about to fly through the centre-line. About 16 seconds prior to passing through the centre-line, the TA provided by the aircraft’s TCAS was the first indication of a potential problem with the aircraft’s flight path. The first officer (FO), who was the pilot monitoring, reported hearing the TCAS TA and that they considered it may have been due to the previously-advised medical traffic departing Bankstown. Although the captain, who was the pilot flying, described the medical traffic as a minor distraction, the FO remained concerned about its location. This distraction probably reduced the crew’s ability to fully appreciate the location of their own aircraft and anticipate its future position relative to the runway centre-line."
Aircraft Registration Data
This article is published under license from Avherald.com. © of text by Avherald.com.
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