What happened
On 22 November 2021, a Network Aviation Fokker F100, registered VH-NHV, was operating flight QF1616 from Perth Airport to Paraburdo Airport, Western Australia. While the initial flight plan indicated weather conditions would remain above landing minima, the crew encountered unexpected low cloud upon arrival.
After the first approach, the crew noted a tailwind and brief visual contact with the runway, leading them to attempt a second approach. However, the second attempt was unsuccessful due to cloud obscuring the runway. Following a third missed approach, the crew faced a critical fuel situation. While they had sufficient fuel to divert to Karratha immediately after the second approach, the third attempt depleted the reserves necessary to reach a suitable alternate safely.
Unable to confirm improved weather at Newman Airport and lacking the fuel to reach Karratha, the crew proceeded with a fourth approach. During this final attempt, the aircraft continued below the required landing minima without visual reference to the runway due to the deteriorating weather and the aircraft's fuel state.
The investigation
The investigation examined the crew's decision-making process regarding diversion and the technical limitations regarding weather updates. It was found that the crew's confidence in their original forecasts diminished after the second missed approach. The investigation also looked into why the low cloud was not predicted, noting that the airport lacked equipment to detect surface-level moisture content, and meteorological modeling limitations contributed to the unforecast conditions.
Furthermore, the investigation identified that the aircraft lacked an operational ACARS, making the crew dependent on air traffic control for weather updates. A delay in receiving weather information for Newman Airport, combined with the crew's lack of urgency in requesting it, further complicated their ability to make a timely diversion decision.
Findings
- The crew elected to continue approaches instead of diverting after the second missed approach because they lacked immediate access to actual weather information for alternate airports.
- The crew lacked sufficient fuel to divert to a suitable airport after the third missed approach.
- Actual weather conditions at Paraburdoo were worse than forecast and were actively deteriorating.
- The aircraft was unable to receive automated weather updates via ACARS and was out of range of the Meekatharra AERIS service.
- Network Aviation had not provided specific procedural guidance for flight crews encountering unforecast weather below landing minima.
- The operator's risk assessments for controlled flight into terrain did not account for the specific threat of unforecast weather below landing minima.
Safety message
- Network Aviation did not include the threat of unforecast weather below landing minima in their controlled flight into terrain risk assessments. This increased the risk that controls required to manage this threat would not be developed, monitored, and reviewed at a management level.