ASN Wikibase Occurrence # 283984
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| Date: | Tuesday 27 September 2022 |
| Time: | 11:35 UTC |
| Type: |  Boeing 787-8 Dreamliner |
| Owner/operator: | Avianca |
| Registration: | N781AV |
| MSN: | 37503/228 |
| Year of manufacture: | 2014 |
| Fatalities: | Fatalities: 0 / Occupants: 254 |
| Aircraft damage: | None |
| Category: | Incident |
| Location: | West of Azores -
 Portugal
|
| Phase: | En route |
| Nature: | Passenger - Scheduled |
| Departure airport: | Bogotá-Eldorado Airport (BOG/SKBO) |
| London-Heathrow Airport (LHR/EGLL) | |
| Investigating agency: | GPIAAF |
| Confidence Rating: |  Accident investigation report completed and information captured |
Avianca flight AV120, a Boeing 787-8, was overflying Santa Maria airspace (Azores) at FL410, when the left engine failed leading the crew to declare emergency to the air traffic control.
The crew handled the emergency and diverted to Lajes Airport (LPLA) at Terceira Island, where it landed without further occurrences at 11:35.
The initial examination of the engine has identified cracks in the engine external gearbox casing around the right-angle input drive.
From the engine damage assessment, analysis of maintenance documentation and information received from the operator regarding the performed maintenance activity, the cause for the uncommanded in-flight shutdown of engine no.1 was the incorrect reinstallation of the radial drive shaft following the execution of a mandatory inspection for wear on the abutting shoulders of the ADS coupling and the IP output shaft splines.
The incorrect installation was such that there was minimal engagement between the splines (most likely just the lead-in splines) of the lower adapter and the TGB input shaft. The weir seal of the lower adapter would have been sitting on the upper shoulder of the TGB input shaft splines which (together with the resistance provided from the upper weir seal, pressed against the splines of the IP output shaft) was sufficient to maintain the drive shaft assembly from dropping under its own weight.
Upon conclusion of the maintenance actions, the engine was subjected to a series of low and high-speed engine ground runs prior to its flight to London. Over six hours into the flight, the lower adapter ultimately separated from the TGB input shaft with ensuing damage to the different components of the drive shaft assembly, TGB casing and loss of drive to the EGB which culminated in the shutdown of the engine.
The following factors contributed to the incorrect installation of the Radial Drive Shaft:
• Complexity of the AMM task, which was compounded by the lack of detailed images as well as similarity of nomenclator used to identify different components and the inconsistent use thereof between Boeing AMM and Rolls-Royce procedures.
This is of particular relevance to maintenance technicians around the world whose first language is not English and where such factors are prone to causing confusion.
• The lack of requirement for an inspection (independent inspection) following the installation of the radial drive shaft, in particular with regards to verification of the four checks required in the AMM instructions to ensure proper installation.
• The maintenance team’s lack of experience with the assigned task, the fact that they had not received any specific training on what is considered a critical and complex procedure (re-installation of the radial drive shaft), and,
• Possible environmental factors (such as lighting conditions) which may help explain the debris which provoked the heat spots.
Accident investigation:
 |
|
Sources:
https://www.eltiempo.com/vida/viajar/avianca-habla-pasajera-sobre-vuelo-que-aterrizo-de-emergencia-en-portugal-705590
https://www.aviacionline.com/2022/09/aviancas-boeing-787-incident-over-the-atlantic-what-we-know/
https://www.flightradar24.com/data/aircraft/n781av#2d9f64f0
GPIAAF
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 29-Sep-2022 07:41 | Gavilan | Added |
| 29-Sep-2022 07:45 | harro | Updated [Aircraft type, Cn, Total occupants, Other fatalities, Location, Nature, Departure airport, Destination airport, Source, Narrative] |
| 05-Oct-2022 09:25 | harro | Updated [Time, Source, Narrative] |
| 03-Nov-2022 15:56 | Anon. | Updated [Destination airport] |
| 06-Apr-2024 16:20 | ASN | Updated [Narrative, Accident report] |
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