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ASN Wikibase Occurrence # 86968
Last updated: 22 August 2020
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Date:27-DEC-2010
Time:11:00
Type:Silhouette image of generic AS3B model; specific model in this crash may look slightly different
Eurocopter AS 332L2 Super Puma Mk2
Owner/operator:Government Flying Service
Registration: B-HRN
C/n / msn: 2547
Fatalities:Fatalities: 0 / Occupants: 3
Other fatalities:0
Aircraft damage: Minor
Location:Shing Mun Reservoir -   Hong Kong
Phase: Manoeuvring (airshow, firefighting, ag.ops.)
Nature:Fire fighting
Departure airport:Hong Kong-Chek Lap Kok International Airport (HKG)
Destination airport:
Narrative:
The helicopter was lifting an underslung water bucket filled up with water at Shing Mun Reservoir for fire-fighting operation.
When the helicopter was on transition to forward flight, the No. 2 engine shut down automatically due to an overspeed signal.
The captain decided to ditch the helicopter into the reservoir. All crew members on board evacuated the helicopter without injury.

Casual factors:
1. The automatic shutdown of No.2 engine was due to free turbine overspeed as the result of a slippage of the right freewheel shaft in the MGB.
2. The right freewheel unit slipped because of the unpredicted growth rate of ramp wear and the maximum allowable wear limit of 0.05 mm for the acceptance of the freewheel shaft during the previous MGB overhaul.
3. Due to the deformation of MGB under flight loads and the associated effects on the freewheel rollers, during fire fighting operations the ramp wear grew at a higher rate than those Eurocopter had predicted.

Sources:

http://www.cad.gov.hk/reports/B-HRN%20Accident%20Report.pdf


Revision history:

Date/timeContributorUpdates
27-Dec-2010 05:25 hkaiw Added
27-Dec-2010 05:26 harro Updated [Aircraft type, Cn, Total occupants, Location, Narrative]
27-Dec-2010 05:31 hkaiw Updated [Time, Aircraft type, Destination airport]
27-Dec-2010 09:48 TB Updated [Aircraft type, Cn, Operator, Narrative]
26-Jan-2011 14:28 harro Updated [Source, Narrative]
22-Jul-2013 18:43 harro Updated [Source, Narrative]

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