What Happened
On the evening of Friday 27 January 2023, a Boeing 777-319ER registered ZK-OKN, operated by Air New Zealand, was returning to Auckland after a flight from Melbourne. As the aeroplane approached Auckland, heavy rain was encountered and the wind changed in direction and strength. As the aeroplane neared the runway, it began to drift right of the runway centreline. Soon after touchdown, it veered off the runway onto a sealed shoulder, striking six runway edge lights before returning to the centre of the runway.
The aeroplane was taxied to the gate and passengers offloaded. An inspection revealed five of the six right landing-gear tyres were damaged and one had deflated. There was also damage to the right brake assembly and wiring harness. There were no injuries.
Sequence of Events
The flight crew consisted of a captain, a first officer, and a second officer. The captain was the pilot flying (PF) and the first officer was the pilot monitoring (PM) for the return leg. At 1700, about 15 minutes before descent, the PF obtained the current aerodrome weather information: runway wet, visibility 5 km reducing to 3000 m in rain, cloud 800 ft, surface wind 030° at 23 kt. The crew discussed the significant moisture and possible storms.
At 1706, the PM contacted Auckland approach control. The aeroplane was cleared for a standard arrival (STAR) and an ILS approach for runway 05R. Descent began at 1716. At 1735, the crew was established on the localiser and switched to tower frequency. The tower controller noted visibility on final approach was around 2000 m.
At 1737 the preceding Metroliner landed. At 1738:21, the tower controller cleared the Boeing to land, reporting surface wind 020° at 14 kt. At 1740:03, the PF reported the runway in sight at about 320 ft above the runway. Fifteen seconds later, the PF disengaged the autopilot at 90 ft AMSL (67 ft AGL). Three seconds later, the PF started flaring. At 1740:32, the PM called "you're left of centreline" (flight data confirmed the aeroplane was right of centreline). Touchdown occurred at 1740:34, with reverse thrust selected immediately. The PM advised "Centreline's just to the left, come to the left". The nose wheel touched down at 1740:40.
About 20 seconds after landing, the PM observed a tyre-low-pressure indication on the right main landing gear. The PM informed the tower controller of potential debris. The aeroplane exited at taxiway A3 and taxied to the gate. After shutdown, the rear inboard tyre on the right main landing gear was deflated. Five tyres were damaged. The tower controller advised a subsequent Air New Zealand flight, which elected to go around and divert to Christchurch. The runway was closed for inspection and reopened later that evening.
Why It Happened
The Transport Accident Investigation Commission (the Commission) found that the heavy rain likely contributed to the decision to disengage the autopilot low in the approach. The timing of the autopilot disengagement combined with the technique used by the pilot flying very likely resulted in insufficient time to correct the flightpath before landing. The pilot flying was therefore unable to prevent the aeroplane drifting away from the centreline before landing and stopping it veering off the runway after landing. The weather, while inclement, was above the minimum weather requirements throughout the approach and landing. The Commission found it exceptionally unlikely that heavy rain contaminated the runway to the extent that it caused the runway excursion. While it was exceptionally unlikely that poor briefings contributed to the excursion, the Commission found that the approach and landing briefing did not meet the operator’s guidelines.
Additional Findings
The Commission noted that operator and aircraft manuals and procedures are designed to help ensure safe flight in normal and adverse circumstances. It emphasised the importance of crew cohesion and thorough briefings as core elements of crew resource management.