A Virgin Australia Boeing 737-800 came within five metres of a runway excursion after landing at Christchurch Airport because pilots did not configure the aircraft properly for a wet arrival, the Australian Transport Safety Bureau (ATSB) says.
The ATSB final report on the May 12 2015 incident, published on Tuesday, says the pilots on board flight VA134 from Sydney to Christchurch, operated by 737-800 VH-VOP, “misperceived the runway surface conditions”, believing it was damp when it was actually wet.
“As a result, the crew established the aircraft’s landing performance based on a dry rather than a wet runway and the expected Runway 29 landing performance was not achieved,” the ATSB final report says.
“The aircraft came to a stop about 5m from the runway end.”
Christchurch Airport’s Runway 11/29 measures 1,741m in length and is the shorter of the airport’s two runways, with Runway 02/20 at 3,288m in length.
The aircraft touched down on Runway 29 within the touchdown zone, at which time full reverse thrust was applied and the speedbrakes deployed.
“However, after crossing the runway intersection, the aircraft did not continue to decelerate as expected and the crew believed the aircraft appeared to slide or skid,” the ATSB report says.
“In response, the crew overrode the autobrakes and applied hard manual braking while retaining full reverse thrust for longer than used in normal operations.
“The crew also corrected a minor directional deviation.”
There were no injuries to those on board and no damage to the aircraft.
The ATSB report says a review of the recorded flight data found that the approach was stable, the approach speed was normal, the aircraft landed within the touchdown zone and in proximity to the required touchdown point.
Further, deceleration devices such as speedbrakes and autobrakes were deployed in a timely manner.
“It was likely that the initial exceedance of the AUTOBRAKE 3 deceleration rate, combined with the crew’s application of hard manual braking and retaining reverse thrust prevented a runway excursion,” the ATSB says.
The ATSB report notes the pilots were experiencing increased workload prior to landing as there was a change to the runway-in-use at Christchurch Airport from Runway 02 to Runway 29, due to surface wind conditions.
As a result, the flightcrew had to prepare for a revised approach.
There was also a deviation from the prescribed flight track due to expected weather as shown on the weather radar.
The captain focused on entering the approach into the flight management system and assessed the aircraft’s landing performance to determine the suitability of Runway 29, while the first officer managed the weather deviation and focused on the implications of landing on a shorter runway.
“Due to the crew experiencing increased workload, the crew misperceived critical landing information, which resulted in the aircraft’s landing performance being determined based on a damp (dry) runway rather than a wet runway,” the ATSB report says.
The ATSB identified four safety issues arising from the incident.
First, the report notes several months prior to the incident, Virgin Australia had changed its policy on calculating landing performance for damp runways from referencing a wet runway to a dry runway.
Second, there was no regulatory direction from Australia’s Civil Aviation Safety Authority (CASA) on how a damp runway was to be considered for aircraft landing performance.
Third, Virgin Australia did not have a policy requiring crews to independently cross-check environmental information and landing performance calculations in-flight, removing an opportunity to detect crew errors.
And fourth, the in-flight landing distance safety margin may be inadequate under certain runway conditions, which increased the risk of a runway excursion.
In response to these safety issues, the ATSB report says Virgin Australia conducted an initial post-implementation review of the change to its policy that permitted a damp runway to be considered dry for performance purposes.
“A further review of this change is currently underway in response to the ATSB’s investigation report,” the ATSB report says.
“Any policy changes will be incorporated into the aircraft performance training course.”
ATSB executive director for transport safety Nat Nagy said the incident demonstrated how the subjective nature of runway surface reports and braking actions reports can contribute to the risk of a runway excursion.
“There is little standardisation between how pilots, industry and regulators describe runway surface conditions,” Nagy said in a statement.
“Information provided to pilots is often from multiple sources, with undefined terminology that may only be relevant to a certain time or type of aircraft.
“To overcome this, the International Civil Aviation Organization will be adopting the United States Federal Aviation Administration’s (FAA) runway condition assessment matrix in November 2020.”
The ATSB noted CASA plans to align its runway condition definitions with those of ICAO post 2020.
“Until then, pilots are advised to apply a conservative approach when relying other pilot reports for runway surface conditions, in particular, when the conditions are considered damp,” Nagy said.