ASN Wikibase Occurrence # 284067
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| Date: | Monday 19 September 2022 |
| Time: | 09:00 UTC |
| Type: |  ATR 72-600 (72-212A) |
| Owner/operator: | Aer Lingus Regional, opb Emerald Airlines |
| Registration: | EI-GPN |
| MSN: | 1300 |
| Year of manufacture: | 2015 |
| Fatalities: | Fatalities: 0 / Occupants: 36 |
| Aircraft damage: | None |
| Category: | Serious incident |
| Location: | Near Belfast City Airport (BHD/EGAC) -
 United Kingdom
|
| Phase: | Approach |
| Nature: | Passenger - Scheduled |
| Departure airport: | Leeds/Bradford Airport (LBA/EGNM) |
| Belfast City Airport (BHD/EGAC) | |
| Investigating agency: | AAIB |
| Confidence Rating: |  Accident investigation report completed and information captured |
Aer Lingus flight EI3671, an ATR 72-600 operated by Emerald Airlines, was on approach to Belfast City Airport (BHD) when the crew reported a partial electrical failure and a number of aircraft systems dropped off-line including some necessary for landing. The flight crew, experiencing natural effects of startle and surprise, and without a specified procedure to follow, continued with the approach, restoring systems by turning off the Transformer Rectifier Unit (TRU). The aircraft continued for a safe landing on runway 22.
The aircraft returned to service 4 days after landing.
Conclusion
The aircraft was operating under EASA Emergency Airworthiness Directive E-AD 2021-0120-E which had been introduced to de-risk potential problems within the battery master toggle switch and the 1PA contactor. This meant that the TRU was selected on and the 95PA and 96PA contactors were energised throughout all flights.
In this case the 95PA contactor failed when the Transformer Rectifier Unit (TRU) was selected ON and thereby not properly energising, disconnecting the DC output from the TRU to the STBY and EMER BUS bars. This caused a number of vital aircraft systems to drop off-line during the aircraft’s approach to Belfast City Airport.
The extreme, unforeseen, and dynamic nature of the failure caused characteristic startle and surprise effects in the flight crew. Without a specified procedure to follow, they continued flying the approach, successfully restoring systems by turning off the TRU which restored electrical power to the affected systems by de-energising failed relay 95PA.
The effect of a malfunction of the 95PA or the 96PA contactor when the AD was issued may not have been fully understood, and so an in-flight rectification procedure had not been introduced into the QRH to allow the flight crew to identify, troubleshoot and restore systems. The report considers situation management methods for helping crew mitigate startle and rebuild situation awareness before completing an approach.
Technical cause of the contactor failure
The failure of this 95PA contactor fitted in EI-GPN was caused by a slippage between the plunger and pin assembly operating under increased cycles. The slippage resulted in poor connection, localised arcing and subsequent loss of continuity across its A1 and A2 terminals. A definitive cause of the pin and plunger slippage with the 95PA contactor
fitted to EI-GPN and several other contactors manufactured during 2015, could not be fully determined.
Accident investigation:
 |
|
Sources:
1. https://bea.aero/en/investigation-reports/notified-events/detail/serious-incident-to-an-atr-72-operated-by-emerald-on-19-09-2022-near-belfast/
2. https://www.gov.uk/government/publications/aaib-current-field-investigations/air-accidents-investigation-branch-current-field-investigations
Media:
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 30-Sep-2022 07:09 | harro | Added |
| 30-Sep-2022 07:11 | harro | Updated [Time, Location, Narrative] |
| 30-Sep-2022 14:56 | Dr. John Smith | Updated [Source, Embed code, Narrative] |
| 21-Nov-2022 05:22 | Ron Averes | Updated [Location] |
| 29-Feb-2024 10:16 | ASN | Updated [Total occupants, Narrative, Accident report] |
| 29-Feb-2024 10:16 | ASN | Updated [Embed code] |
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