Unserviceable aircraft assigned to flight due to communication failure

No fatalities • 30 km north of Perth Airport, Western Australia

A flight departed with an aircraft unable to pressurise after a maintenance omission and administrative error allowed an unserviceable plane to remain on the flight manifest.

What happened

A flight was conducted using VH-QQD, an aircraft type that was unable to maintain cabin pressure because a recirculation fan had been removed the previous day. Although the removal of the fan was recorded in the maintenance log, the aircraft's unserviceable status was not updated in the company's operations management system. Consequently, the flight crew saw the aircraft listed as available on the flight manifest during their pre-flight checks. The crew only discovered the lack of pressurisation capability during the transition altitude checklist.

The investigation

The investigation focused on why the crew proceeded with a flight using an aircraft that could not pressurise. It was found that the operations department failed to remove VH-QQD from the flight assignment despite receiving notification from engineering regarding the unserviceable status of several aircraft. Because the flight manifest showed the aircraft as assigned, the crew had no immediate reason to suspect any issues.

Furthermore, the investigation examined the crew's pre-flight inspection of the aircraft's documentation. While the captain encountered a circuit breaker that had been opened to facilitate the fan removal, this did not prompt a review of the maintenance log. The captain also did not check the log because there were no 'pink pages' indicating permissible unserviceabilities, which would typically trigger such a review. The first officer did not inspect the documentation as there was no specific requirement for them to do so in this context.

Findings

  • The operations department failed to update the operations management system, leaving the aircraft assigned to the flight despite its unserviceable status.
  • The captain did not identify the removal of the recirculation fan because the maintenance log was not reviewed.
  • Expectation bias likely influenced the captain, as the flight manifest and the lack of visible defects suggested the aircraft was airworthy.
  • The absence of the recirculation fan was not detectable during a standard external inspection.

Probable cause

The flight proceeded with an unserviceable aircraft because the operations department failed to update the flight manifest, and the flight crew did not detect the missing recirculation fan due to a failure to review the maintenance log, compounded by expectation bias.

Frequently asked questions

What happened in the 2021-10-20 De Havilland Canada/De Havilland Aircraft of Canada DHC-8-102 accident near 30 km north of Perth Airport, Western Australia?

A flight departed with an aircraft unable to pressurise after a maintenance omission and administrative error allowed an unserviceable plane to remain on the flight manifest.

Were there any fatalities in the 2021-10-20 De Havilland Canada/De Havilland Aircraft of Canada DHC-8-102 accident?

No fatalities were recorded in this accident.

What aircraft was involved and where did it happen?

The accident on 2021-10-20 involved a De Havilland Canada/De Havilland Aircraft of Canada DHC-8-102, registration VH-QQD, operated by Maroomba Airlines, at 30 km north of Perth Airport, Western Australia.

What was the probable cause of the accident?

The flight proceeded with an unserviceable aircraft because the operations department failed to update the flight manifest, and the flight crew did not detect the missing recirculation fan due to a failure to review the maintenance log, compounded by expectation bias.

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