Virgin Australia B773 at Melbourne on Aug 15th 2013, waypoint 2.8nm out at 50 feet above runway

Last Update: July 15, 2015 / 15:56:28 GMT/Zulu time

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Incident Facts

Date of incident
Aug 15, 2013

Classification
Incident

Airline
Virgin Australia

Flight number
VA-24

Departure
Los Angeles, United States

Destination
Melbourne, Australia

Aircraft Registration
VH-VPF

Aircraft Type
Boeing 777-300

ICAO Type Designator
B773

A Virgin Australia Boeing 777-300, registration VH-VPF performing flight VA-24 from Los Angeles,CA (USA) to Melbourne,VI (Australia), was on the LIZZY 7V STtandard Arrival Route (STAR) into Melbourne using the automation in LNAV and VNAV mode to be followed by a visual approach to Melbourne's runway 34, the captain was pilot flying and the first officer pilot monitoring, when after passing the last waypoint SHEED of the STAR the autopilot increased the rate of descent from 700fpm to about 1500 fpm. The crew noticed the abnormal descent and discussed the anomaly, the first officer who focussed on looking out of the window noticed the approach looked low and alerted the captain. The captain agreed with the assessment and attempted to reduce the rate of descent by adjusting vertical speed of the automation, then disconnected the autopilot and levelled the aircraft manually at 700 feet MSL (500 feet AGL) about 2.8nm before the runway threshold. The aircraft maintained 700 feet MSL until intercepting a 3 degrees glidepath again and continued for a safe landing on runway 34.

The ATSB opened an investigation into the occurrence rated an incident and reported, that the FMS had been programmed for the LIZZI7V STAR followed by a visual approach to runway 34. To accomplish the visual approach to runway 34 the FMS provided two waypoints, RWY34 at 330 feet marking the threshold of the runway at true altitude of 330 feet with the recommendation by the operator to ammend that altitude to 380 feet to cater for overflying the threshold at 50 feet AGL, and a mirror waypoint RWY34X that effectively was the same as RWY34, however could be freely moved along the final approach path by the crew to mark the point where the aircraft should become aligned with the extended runway center line.

The captain had been preparing the FMS for the approach some time before landing, the relief first officer was still in the cockpit at that time, and had moved RWY34X to about 2.8nm before the runway threshold. The first officer returned to the cockpit afterwards and cross checked the approach procedure programmed by the captain.

Both pilots did not detect however, that the altitude constraint for RWY34X had been set to 380 feet MSL, which prompted the automation to aim crossing that point at 380 feet MSL and thus caused the increased rate of descent.

The investigation is estimated to conclude by January 2014.

On Jul 15th 2015 the ATSB released their final report concluding the probable causes of the incident were:

Contributing factors

- When programming the approach into the flight management computer, the captain inadvertently entered the runway threshold crossing altitude into the runway extension waypoint, resulting in the flight management system calculating a vertical flight path that was below the intended approach path and a consequential high descent rate after passing the SHEED waypoint.

- When checking the flight management system, the first officer did not detect that the runway threshold crossing altitude had been entered into the runway extension waypoint, missing the opportunity to prevent the unintended approach path and resulting high descent rate after passing the SHEED waypoint.

- After passing the SHEED waypoint, the captain's attention became focused on the high rate of descent instead of monitoring external flight path cues as part of the visual approach, causing the first officer to shift their attention to the external cues and leading to a delayed recognition and response to the aircraft's position below the intended approach path.

Other factors that increased risk

- The flight crew were probably experiencing a level of fatigue known to have a demonstrated effect on performance.

- The presentation of the runway 34 visual approach procedure in the operator's Route and Airport Information Manual increased the potential for the runway threshold crossing altitude to be entered into the runway extension waypoint. [Safety issue]

The ATSB analysed: "During the entry of the visual approach into the FMS, the captain inadvertently entered the runway threshold crossing altitude of runway threshold elevation + 50 ft into runway extension waypoint RX34, instead of into the intended RW34. RW34 corresponded with the runway threshold. This resulted in the aircraft descending after SHEED to meet this erroneous waypoint altitude constraint, which was 2.8 NM or about 5 km from the runway threshold and therefore necessitated a higher than normal descent rate to achieve the RX34 altitude constraint as set. The erroneous entry of the runway threshold crossing altitude at the RX34 waypoint was almost certainly a skill-based error known as a ‘slip’, which is an error in the execution of an action (Reason 1990). Skill-based actions are those which have become so rehearsed and automatic that the individual does not need to closely monitor each stage of the action sequence in the way that they would if the task was less familiar or unknown. Due to this reduced monitoring, the individual will generally not realise that they have carried out an incorrect action until it is either too late to change, or there has already been an unforseen consequence."

The ATSB analysed with respect to fatigue: "While research indicates that less than 6 hours sleep in the previous 24 hours can increase risk (Thomas and Ferguson 2010), the captain had about 10 hours sleep in the 24 hours prior to departure and the operational FO had about 12 and a half hours. In addition, the flight crew reported obtaining adequate ‘good quality’ sleep during the layover in Los Angeles and feeling well rested at the commencement of the flight. However, the effect of extended wakefulness for both crew and workload due to training duties for the FO meant that both crew were probably experiencing a level of fatigue known to have a detrimental effect on performance. ... The types of errors made by the crew, the slip and then the non-detection of the incorrect waypoint RX34 altitude constraint, are broadly consistent with the effects of fatigue."

The ATSB reported that as result of the occurrence Virgin Australia removed the SHEED arrival from use by their Boeing 777 crews.
Incident Facts

Date of incident
Aug 15, 2013

Classification
Incident

Airline
Virgin Australia

Flight number
VA-24

Departure
Los Angeles, United States

Destination
Melbourne, Australia

Aircraft Registration
VH-VPF

Aircraft Type
Boeing 777-300

ICAO Type Designator
B773

This article is published under license from Avherald.com. © of text by Avherald.com.
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