Date:	Wednesday 23 September 2020
Time:	10:00 UTC
Type:	Airbus Helicopters H-175B
Owner/operator:	CHC Scotia Ltd
Registration:	G-EMEB
MSN:	5030
Fatalities:	Fatalities: 0 / Occupants: 2
Other fatalities:	0
Aircraft damage:	Minor
Category:	Incident
Location:	Aberdeen International Airport (ABZ/EGPD) -   United Kingdom
Phase:	Standing
Nature:	Test
Departure airport:	Aberdeen International Airport (ABZ/EGPD)
Destination airport:
Investigating agency:	AAIB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
AAIB investigation to Airbus Helicopters EC175B, G-EMEB: Alternator pinion bearing failure within the left accessory gearbox, Aberdeen Airport, 23 September 2020. The incident took place while the helciopter was ground running at Aberdeen Airport, and was the subject of an AAIB Investigation, published on 22 April 2021:

"Synopsis
A failure of an alternator pinion roller bearing in the left accessory gearbox (LAGB) occurred during a post-maintenance ground run following a scheduled replacement of the main gearbox. The investigation identified that the roller bearing was subjected to an excessive axial load during operation, caused by compression of grease and air within the alternator shaft link during installation by the operator of a 10 kVA alternator to the LAGB. The cause of the incident was identified as the application of an excessive quantity of grease to the alternator pinion cavity, as required by the aircraft maintenance manual instructions. The method used by the operator to attach the alternator to the left accessory gearbox was identified as a contributory factor in the incident.

The manufacturer has amended the content of the aircraft maintenance manual to ensure that any excess grease is removed from the alternator shaft link cavity and has communicated this information by issuing a Safety Information Notice to EC175 operators.

Safety action
In response to this incident the manufacturer released Safety Information Notice (SIN) 3599-S-63, alerting EC175 operators to the potential hazard of excessive grease within the alternator shaft link cavity. The manufacturer has also revised the content of AMM tasks 24-21-00, 4-1 (Removal/Installation – Left Alternator 10 kVA) and 24-21-00, 4-2 (Removal/Installation – Blank or Left Alternator 10 kVA Equipment on LAGB), requiring that any excess grease is removed from the shaft link cavity prior to installation of the alternator on the LAGB. The SIN also highlighted the need to follow the published AMM procedure when installing the alternator, by attaching it using the V-band clamp.

As the mounting of the DC generator on the RAGB has a similar design to the 10 kVA alternator, the manufacturer also revised the related AMM installation procedures for the DC generator.

Conclusion
The failure of the F1 bearing was caused by an axial load applied to the roller bearing in excess of the bearing’s rated capacity. The axial load occurred due to the compression of excess grease and air within the sealed alternator shaft link cavity when the alternator was mounted to the LAGB. The method used to mount the alternator to the LAGB was not in accordance with the instructions in the AMM. This contributed to the generation of the axial load, which was up to four times greater than would have been the case had the AMM
instructions been followed.

The manufacturer has amended the content of the AMM to ensure that any excess grease is removed from the alternator shaft link cavity and has communicated this information by issuing a Safety Information Notice to EC175 operators."

Damage Sustained to airframe
Per the AAIB report: "Bearing failure within the left accessory gearbox". The helicopter was repaired and returned to service.

1. AAIB Report 22 April 2021: https://assets.publishing.service.gov.uk/media/607fceace90e076ab6cbdced/EC175B_G-EMEB_06-21.pdf
2. https://www.helis.com/database/cn/47562/
3. https://www.flightglobal.com/helicopters/lci-takes-first-h175-helicopter-for-operation-by-chc/126528.article
4. https://www.flightradar24.com/data/aircraft/G-EMEB
5. https://www.radarbox.com/data/registration/G-EMEB
6. https://en.wikipedia.org/wiki/Aberdeen_Airport

Built 2017. First registered 14 December 2017 as G-EMEB to CHC Scotia Ltd (on charter/lease from LCI Aviation (Lease Corporation International). After the incident at Aberdeen Airport on 23 September 2020, G-EMEB was repaired and returned to service. Total amount of flying hours accumulated on the airframe: 4.495 as at 15 November 2023.

G-EMEB: Airbus Helicopters H175 at Norwich Airport, Norwich, Norfolk (NWI/EGSH) 27 August 2020

Date/time	Contributor	Updates
11-Nov-2024 08:51	Dr. John Smith	Added
11-Nov-2024 08:51	ASN	Updated [Accident report, ]
27-Nov-2024 16:42	Dr. John Smith	Updated [Aircraft type, ]