ASN Wikibase Occurrence # 224058
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| Date: | Sunday 14 April 2019 |
| Time: | 00:10 LT |
| Type: |  Pilatus PC-12/47E |
| Owner/operator: | Royal Flying Doctor Service |
| Registration: | VH-OWJ |
| MSN: | 1411 |
| Year of manufacture: | 2013 |
| Fatalities: | Fatalities: 0 / Occupants: 4 |
| Aircraft damage: | None |
| Category: | Serious incident |
| Location: | Merredin, WA -
 Australia
|
| Phase: | Initial climb |
| Nature: | Ambulance |
| Departure airport: | Merredin Airport (YMDN) |
| Jandakot Airport, WA (JAD/YPJT) | |
| Investigating agency: | ATSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The pilot of a Pilatus PC-12/47E aircraft, registered VH-OWJ and operated by Royal Flying Doctor Service - Western Operations (RFDS), was conducting a medical transport flight under instrument flight rules from Merredin to Jandakot within Western Australia. A RFDS aeromedical crew consisting of a flight nurse and doctor were on board with a non-critical patient who was being transferred to a hospital in Perth. For the midnight departure, there were almost clear skies with minimal ambient and celestial lighting.
About 1.5 minutes after take-off, ‘Pitch Trim Runaway’ warnings activated and the pitch trim continued to move nose-down without any pilot or autopilot inputs. The pilot initiated the applicable emergency procedure but inadvertently selected the Flap Interrupt switch rather than the Trim Interrupt switch. Consequently (before the next checklist item was actioned), the pitch trim continued to runaway until it reached full nose-down with associated serious control difficulties.
The pilot did not identify the mis-selection and continued to address the emergency procedure without resolving the full out-of-trim condition. With the assistance of the doctor seated in row 2, the pilot managed to return to Merredin for a flapless landing. The aircraft was undamaged and the occupants uninjured.
Contributing factors
- Soon after take-off in dark-night conditions, the pitch trim system continued to operate in a nose-down direction without pilot input or autopilot commands (pitch trim runaway) because of a malfunctioning relay in the manual (main pilot-engaged) stabiliser trim system.
- In response to the Crew Alerting System warnings, the pilot initiated the Pitch Trim Runaway emergency procedure but inadvertently selected the Flap Interrupt switch rather than the Trim Interrupt switch (item 1). Consequently (before the next checklist item was actioned), the pitch trim continued to runaway until it reached full nose-down with associated serious control difficulties.
- After the pilot addressed items 2 and 3 of the emergency procedure, the malfunction was neutralised and the alternate stabiliser trim system was available to adjust the trim. However, the pilot did not identify those positive conditions and continued with items 4 to 8 of the procedure, which disabled the alternate stabiliser trim system, prevented pitch trim adjustment and prolonged the serious control difficulties.
- The similarities between the Trim Interrupt and Flap Interrupt switches and the proximal location of the two switches unnecessarily increased the risk of mis-selection and contributed to the excessive out-of-trim condition.
- The emergency procedures and systems information in the PC-12 Pilot’s Operating Handbook/Airplane Flight Manual and Quick Reference Handbook did not provide effective guidance or sufficient information for pilots contending with a pitch trim runaway. If the pilot selects the Trim Interrupt switch early in the sequence and does not need to adjust the pitch trim, the risk is not significant. In this case, the lack of effective guidance and systems information probably had an adverse influence on the pilot’s capability to resolve the uninterrupted trim runaway condition and was a critical factor.
Accident investigation:
 |
|
Sources:
https://www.atsb.gov.au/publications/investigation_reports/2019/aair/ao-2019-019/
https://flightaware.com/live/flight/VHOWJ
https://www.jetphotos.com/photo/8937797
Images:
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 16-Apr-2019 19:43 | harro | Added |
| 17-Apr-2019 03:33 | Geno | Updated [Departure airport, Destination airport, Source] |
| 19-May-2020 19:56 | harro | Updated [Time, Total occupants, Phase, Narrative, Accident report, ] |
| 31-May-2022 22:25 | Ron Averes | Updated [Operator] |
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