Dangerous landing at Christchurch Airport caused by Virgin Australia's landing policy
Shortly after midnight, the aircraft landed on runway 29 at Christchurch. Runway 29 was shorter than the main runway at Christchurch, Australian Transport Safety Bureau said.
The aircraft landed within the required touchdown zone, using full reverse thrust, speedbrakes, and the autobrake system engaged the wheel brakes.
Recorded flight data showed that the aircraft initially achieved, and at times exceeded the selected AUTOBRAKE 3 target deceleration rate.
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.
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. The aircraft came to a stop about 5 m from the runway end. There were nil recorded injuries or aircraft damage.
The ATSB found that, due to increased workload, the crew misperceived the runway surface conditions and believed it was damp when in fact it was wet.
As there was no regulatory direction on how a damp runway was to be considered for aircraft landing performance purposes, the operator’s policy was to treat a damp runway the same as a dry runway. 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 also found that, several months prior, the operator had changed its policy whereby damp runways had previously been treated as wet runways.
Based on the crew’s observations and a review of the available recorded data, it was very likely that the surface conditions on the later part of the runway had degraded to the extent that they adversely affected the aircraft’s braking capability. It was also possible that the aircraft experienced viscous aquaplaning. However, the initial exceedance of the target deceleration rate, combined with the crew’s actions, likely prevented a runway overrun.
Further, a post-incident analysis of the flight data recorder by the aircraft manufacturer found that a 5 kt tailwind existed on final approach and landing. This also significantly affected the aircraft’s landing performance and further reduced safety margins.
Additionally, and along with the United States Federal Aviation Administration, the ATSB found that the 15 per cent in-flight safety margin applied to actual landing distances during landing performance calculations may be inadequate under certain runway conditions. In these conditions, additional conservatism is encouraged.
This incident highlights the adverse consequences of crew experiencing a high workload during critical phases of flight, including missing important information needed to determine an accurate landing performance.
In addition, runway surface condition and braking action reports (intended for the benefit of other pilots landing aircraft after them) can be subjective, and the terminology used to describe these can be inconsistent. Considerable efforts have been made by organisations such as the United States Federal Aviation Administration to address this issue with the introduction of the runway condition assessment matrix, Australian Transport Safety Bureau said. ■