Airbus A320: NZ investigators identify defect after engine shut down in flight

“This is a risk to future transport safety,” TAIC said in its final interim report released today.

On December 1 last year, the Air New Zealand A320-271N neo had been flying for about 15 minutes when a warning light was triggered.

The captain saw the number two engine indications on a display showing the engine rolling back.

The crew declared a mayday and diverted safely to Auckland.

No injuries or damage occurred.

“The first officer recalled that their first indication that something was wrong was loud clicking noises from the panel behind their seat, which they considered could be indicative of a system power change,” TAIC said in the new report.

The captain initiated the driftdown procedure.

TAIC said that was activated when an aircraft could not keep its cruise level due to engine failure, so descended to where cruise altitude could be maintained with just one functioning engine.

Air New Zealand noticed a fire push button switch for the number two engine on the overhead panel was in the activated position.

“Neither pilot recalled activating the fire switch, and none of the checklists used by the crew required activation of this fire switch.”

Louise Cook, TAIC chief investigator of accidents, said a switch stopping the engine and getting engine fire extinguishers ready “self-activated” and caused the shutdown.

“The switch is part of a panel above and behind the heads of the pilot and co-pilot. Neither had touched the switch, and post-shutdown procedures didn’t tell them to check it,” Cook said.

There were fire switches for each engine on the twinjet and one for the auxiliary power unit (APU).

“The fire switch is only pushed when instructed by a checklist or during routine maintenance procedures on the ground,” the TAIC report added.

The switch, if released, performed jobs including shutting off the full authority digital engine (Fadec) supply.

The Fadec helped control all aspects of aircraft engine performance.

The red light in the fire switch should only come on when a fire is detected, regardless of the fire switch position.

TAIC said the same fire switch was in A330, A340, A350 and A380 aircraft.

TAIC said Airbus was aware of three previous events involving uncommanded fire switch activation.

France’s civil aviation investigator, the Bureau d’Enquetes et d’Analyses (BEA), also examined the matter.

“They confirmed that two events occurred in 2016 and one in 2021. The common factor ... was that when the fire panel was subsequently examined, it was noted that there was damage to the fire panel unit and the pin-locking system within one of the fire switches.”

France’s Safran Electronics & Defense manufactured the panel.

According to TAIC, Safran found the fire panel was damaged by mishandling.

Safran also said: “Two fire panels involved in spurious disengagement have been investigated.”

According to TAIC, Safran added: “The most probable circumstances of shock on the fire panel are the handling of the unit when it is not installed on the aircraft, and during its shipping.”

Safran identified 108 fire panels that should be removed and sent to an approved facility for inspection.

According to TAIC, Air New Zealand identified two other panels and removed them.

Airbus also encouraged operators to return the identified fire panel units to Safran for inspection.

The fire panel in this case was manufactured in 2015 and installed on another A320 delivered to Air New Zealand that year.

The fire panel was sent to the Zodiac Aero Electric22 repair shop in Niort, western France, then fixed and returned to the airline.

Safran was able to identify external damage to the fire switch.

It said damage probably happened when the panel was dropped at some stage.

TAIC said since its investigation started, another panel was found to have experienced a fire switch “uncommanded activation”.

Safran examined that panel too, and said it had signs of external damage.

“The scale and number of damaged fire panels is currently unquantified,” TAIC added.

The commission said Airbus was working with airlines on the fire switch panel issues.

In July this year, TAIC suggested the Civil Aviation Authority work with the European Union Aviation Safety Agency (EASA) to take action.

TAIC said the Civil Aviation Authority discussed the matter with Air New Zealand, which in turn discussed the switch with Airbus.

“Air New Zealand has proactively removed affected fire panels and advocated for clearer inspection criteria in response to Airbus’s inspection service bulletin,” TAIC added.

Service bulletins communicate details of suggested modifications or inspections.

In September, EASA suggested inspections on the A320 family relevant to the issue.

The next month, EASA required inspection of fire panels as outlined in Safran’s relevant service bulletins.

TAIC said Safran documents were made available to airlines, but airlines were not actually aware these documents were available.

The TAIC report said Airbus observed the Air New Zealand incident was the sixth event of its type across the worldwide fleet.

A full TAIC inquiry into the issue was ongoing.

“Upon the completion of the full investigation, the commission will issue a final report on the incident after it completes its inquiry,” TAIC added.

TAIC said it investigated transport incidents with the aim of improving future safety, and did not attribute blame or liability.

Air New Zealand chief safety and risk officer Nathan McGraw said the crew diverted to Auckland, where the aircraft landed safely.

McGraw said the TAIC interim report found a defect in an engine fire switch in the flight deck’s overhead panel had caused the engine shutdown.

“In December 2024, the affected panel was removed from the aircraft and we proactively identified and removed other affected panels from our fleet,” he added.

“Safety is our utmost priority, and we will continue to work closely with all relevant manufacturers and regulators.”