Taxiway design, flight crew distraction and incorrect mental model, lead to Perth Airport runway incursion

Taxiway design, flight crew distraction and incorrect mental model, lead to Perth Airport runway incursion

Key points:

  • 737 taxied toward active runway; second 737 rejected take-off
  • Taxiway location and design significantly increased the risk of a runway incursion
  • Runway incursions are a significant risk to safe aviation operations and a key global safety priority

 

The crew of a Boeing 737 had to reject their take-off roll when a second 737 did not stop at a holding point and passed through an illuminated stop bar after landing at Perth Airport, an ATSB investigation report details. 

On 28 April 2018, a Qantas Boeing 737, registered VH-XZM, landed on runway 03 at Perth, exiting the runway onto taxiway J2, which led to a holding point for crossing runway 06. The aircraft did not stop at the holding point and crossed an illuminated stop bar (a set of lights embedded across the taxiway surface) without an air traffic control clearance.

At that time, a second Qantas 737, VH-VZL, had commenced its take-off roll from runway 06. An automated warning within the Perth air traffic control tower alerted the aerodrome controller (ADC) of the stop bar violation and the controller issued an instruction for the departing 737 to ‘stop immediately’.

Soon after, the flight crew of VH‑XZM became aware of their position and stopped their aircraft just before crossing the edge of runway 06. VH-VZL’s wingtip passed about 15 metres from VH-XZM’s nose at low speed just before coming to a stop.

Among other findings, the ATSB found that the captain of VH-XZM was not expecting to cross runway 06, having developed an incorrect mental model of their location and thinking the aircraft was on taxiway J1 which led directly to the terminal area.

“Due to this incorrect mental model, and a combination of workload and distractions at key times, the flight crew did not detect the runway crossing issue until their aircraft had almost reached the edge of runway 06,” said ATSB Director Transport Safety Dr Mike Walker.

Taxiway J2 was the preferred runway exit for jet aircraft landing on runway 03, the ATSB’s investigation report notes.

“The location and design of the taxiway significantly increased the risk of a runway incursion onto runway 06/24,” Dr Walker said.

“The relatively shallow intersection angle with the runway and wide turn radius meant pilots were more likely to take the exit at a higher speed, and this combined with the short distance to the holding point gave pilots less time to see the illuminated stop bar lights at the runway holding point and stop.”

Although the junction around taxiway J2 was identified as a ‘hot spot’ on aerodrome charts, there was no detailed information about the reasons for it.

Also, Qantas did not specifically require pilots to brief hot spots during departure and approach briefings.

In response to the runway incursion, Airservices Australia made taxiway J2 unavailable for use, and Perth Airport subsequently removed taxiway J2 from aerodrome charts.

In addition, Airservices changed the settings of an alerting system to ensure tower controllers at Perth Airport performing multiple roles received appropriate aural and visual alerts at their workstation.

“Runway incursions are one of the most significant risks to safe aviation operations and a key global safety priority,” Dr Walker said.

“Airport operators and local runway safety teams are strongly encouraged to identify and mitigate the risk of hot spots, especially those that involve short distances between runways, complicated junctions, and the potential for higher taxi speeds.”

Since the incident, Qantas published a safety information notice to all pilots containing information about the background of runway incursions. The airline also updated its Flight Administration Manual to include a requirement for pilots to brief relevant airport hot spots and their contingency planning to mitigate against the possibility of collision or runway incursion.

“Pilots can help prevent incursions by identifying runway hot spots during departure and approach briefings, and discussing the actions they will take to reduce the risk of a runway incursion,” Dr Walker said. 

“The ATSB also strongly encourages air traffic controllers to provide safety alerts and/or clear instructions – such as ‘stop immediately’ – to the flight crews of all aircraft involved in runway incursions and related occurrences.”

Dr Walker noted that the aerodrome controller and flight crew of VH-VZL exhibited a high level of situational awareness to respond to the incursion.

Read the investigation report AO-2018-032: Runway incursion involving Boeing 737, VH-XZM, and subsequent rejected take-off involving Boeing 737, VH-VZL, at Perth Airport, Western Australia, on 28 April 2018

Last update 01 October 2020

Final report

AO-2018-032: Runway incursion involving Boeing 737, VH-XZM, and subsequent rejected take-off involving Boeing 737, VH-VZL, at Perth Airport, Western Australia, on 28 April 2018