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ASN Wikibase Occurrence # 158925
Last updated: 9 December 2018
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Date:23-AUG-2013
Time:18:17 LT
Type:Silhouette image of generic AS3B model; specific model in this crash may look slightly different
Eurocopter AS 332L2 Super Puma Mk2
Owner/operator:CHC Scotia Ltd
Registration: G-WNSB
C/n / msn: 2582
Fatalities:Fatalities: 4 / Occupants: 18
Other fatalities:0
Aircraft damage: Written off (damaged beyond repair)
Category:Accident
Location:off Fitful Head, 2 mi W of Sumburgh, Shetland Islands -   United Kingdom
Phase: Approach
Nature:Non Scheduled Passenger
Departure airport:Borgsten Dolphin drilling rig
Destination airport:Sumburgh Airport (LSI/EGPB)
Investigating agency: AAIB
Narrative:
At 1717 hrs UTC on 23 August 2013, an AS332 L2 Super Puma helicopter with sixteen passengers and two crew on board crashed in the sea during the approach to land at Sumburgh Airport. Four of the passengers did not survive.

The purpose of the flight was to transport the passengers, who were employees of the UK offshore oil and gas industry, to Aberdeen. On the accident flight, the helicopter had departed the Borgsten Dolphin semi-submersible drilling platform in the North Sea, to route to Sumburgh Airport for a refuelling stop. It then planned to continue to Aberdeen Airport.

The commander was the Pilot Flying (PF) on the accident sector. The weather conditions were such that the final approach to Runway 09 at Sumburgh Airport was flown in cloud, requiring the approach to be made by sole reference to the helicopterís instruments, in accordance with the Standard Operating Procedure (SOP) set out in the operatorís Operating Manual (OM). The approach was flown with the autopilot in 3-axes with Vertical Speed (V/S) mode, which required the commander to operate the collective pitch control manually to control the helicopterís airspeed. The co-pilot was responsible for monitoring the helicopterís vertical flightpath against the published approach vertical profile and for seeking the external visual references necessary to continue with the approach and landing. The procedures permitted the helicopter to descend to a height of 300 ft, the Minimum Descent Altitude (MDA) for the approach, at which point a level-off was required if visual references had not yet been acquired.

Although the approach vertical profile was maintained initially, insufficient collective pitch control input was applied by the commander to maintain the approach profile and the target approach airspeed of 80 kt. This resulted in insufficient engine power being provided and the helicopterís airspeed reduced continuously during the final approach. Control of the flightpath was lost and the helicopter continued to descend below the MDA. During the latter stages of the approach the helicopterís airspeed had decreased below 35 kt and a high rate of descent had developed.

The decreasing airspeed went unnoticed by the pilots until a very late stage, when the helicopter was in a critically low energy state. The commanderís attempt to recover the situation was unsuccessful and the helicopter struck the surface of the sea approximately 1.7 nm west of Sumburgh Airport. It rapidly filled with water and rolled inverted, but was kept afloat by the flotation bags which had deployed.

Search and Rescue (SAR) assets were dispatched to assist and the survivors were rescued by the Sumburgh-based SAR helicopters that attended the scene.

The investigation identified the following causal factors in the accident:
ēThe helicopterís flight instruments were not monitored effectively during the latter stages of the non-precision instrument approach. This allowed the helicopter to enter a critically low energy state, from which recovery was not possible.

ēVisual references had not been acquired by the Minimum Descent Altitude (MDA) and no effective action was taken to level the helicopter, as required by the operatorís procedure for an instrument approach.


The following contributory factors were identified:
ēThe operatorís SOP for this type of approach was not clearly defined and the pilots had not developed a shared, unambiguous understanding of how the approach was to be flown.

ēThe operatorís SOPs at the time did not optimise the use of the helicopterís automated systems during a Non-Precision Approach.

ēThe decision to fly a 3-axes with V/S mode, decelerating approach in marginal weather conditions did not make optimum use of the helicopterís automated systems and required closer monitoring of the instruments by the crew.

ēDespite the poorer than forecast weather conditions at Sumburgh Airport, the commander had not altered his expectation of being able to land from a Non-Precision Approach.

On 19 June 2015 a Scottish Judge approved the release of the CVFDR to the Crown Office & Police Scotland.

Sources:

http://www.bbc.co.uk/news/uk-scotland-north-east-orkney-shetland-23821083
http://www.itv.com/news/story/2013-08-23/helicopter-ditches-in-the-shetland-islands-scotland/
http://www.chcheli.com/AboutCHC/News/Pages/CHC-statement-on-Sumburgh-Aircraft-Incident.aspx
http://aerossurance.com/helicopters/commanders-flying-monitoring/
http://www.aaib.gov.uk/cms_resources.cfm?file=/AS332%20L2%20Super%20Puma%20helicopter%20G-WNSB%20Press%20Release.pdf
http://www.aaib.gov.uk/cms_resources.cfm?file=/S6-2013%20AS332%20L2%20G-WNSB.pdf (S6/2013)
https://www.gov.uk/aaib-reports/s7-2013-as332-l2-super-puma-g-wnsb-23-august-2013 (S7/2013)
https://www.gov.uk/aaib-reports/s1-2014-as332-l2-super-puma-g-wnsb-23-august-2013 (S1/2014)
https://www.pprune.org/rotorheads/522069-as332l2-ditching-off-shetland-23rd-august-2013-a.html
https://www.stepchangeinsafety.net/AS332-L2.cfm
https://www.flightglobal.com/news/articles/human-factors-loom-in-sumburgh-crash-report-390243/
http://www.shetlandtimes.co.uk/tag/sumburgh-helicopter-crash
http://aerosociety.com/Assets/Docs/Events/751/RAeS_Conference_Report.pdf
http://aerossurance.com/news/court-orders-release-cvfdr/
https://www.scotcourts.gov.uk/search-judgments/judgment?id=0452dda6-8980-69d2-b500-ff0000d74aa7
http://www.caa.co.uk/aircraft-registration/
https://www.gov.uk/aaib-reports/aircraft-accident-report-aar-1-2016-g-wnsb-23-august-2013

Safety recommendations:

Safety recommendation 2013-021 issued by AAIB to Sumburgh Airport
Safety recommendation 2013-022 issued by AAIB to CAA
Safety recommendation 2016-001 issued 17 March 2016 by AAIB to EASA
Safety recommendation 2016-002 issued 17 March 2016 by AAIB to EASA
Safety recommendation 2016-003 issued 17 March 2016 by AAIB to CAA
Safety recommendation 2016-004 issued 17 March 2016 by AAIB to CAA
Safety recommendation 2016-005 issued 17 March 2016 by AAIB to EASA
Safety recommendation 2016-006 issued 17 March 2016 by AAIB to EASA
Safety recommendation 2016-007 issued 17 March 2016 by AAIB to CAA
Safety recommendation 2016-008 issued 17 March 2016 by AAIB to EASA
Safety recommendation 2016-009 issued 17 March 2016 by AAIB to EASA
Safety recommendation 2016-010 issued 17 March 2016 by AAIB to CAA
Safety recommendation 2016-011 issued 17 March 2016 by AAIB to CAA
Safety recommendation 2016-012 issued 17 March 2016 by AAIB to CAA
Safety recommendation 2016-013 issued 17 March 2016 by AAIB to EASA
Safety recommendation 2016-014 issued 17 March 2016 by AAIB to EASA
Safety recommendation 2016-015 issued 17 March 2016 by AAIB to EASA
Safety recommendation 2016-016 issued 17 March 2016 by AAIB to EASA
Safety recommendation 2016-017 issued 17 March 2016 by AAIB to EASA
Safety recommendation 2016-018 issued 17 March 2016 by AAIB to EASA
Safety recommendation 2016-019 issued 17 March 2016 by AAIB to EASA
Safety recommendation 2016-020 issued 17 March 2016 by AAIB to EASA
Safety recommendation 2016-021 issued 17 March 2016 by AAIB to EASA
Safety recommendation 2016-022 issued 17 March 2016 by AAIB to EASA
Safety recommendation 2016-023 issued 17 March 2016 by AAIB to EASA
Safety recommendation 2016-024 issued 17 March 2016 by AAIB to EASA
Safety recommendation 2016-025 issued 17 March 2016 by AAIB to EASA
Safety recommendation 2016-026 issued 17 March 2016 by AAIB to EASA


Revision history:

Date/timeContributorUpdates
23-Aug-2013 19:03 harro Added
23-Aug-2013 19:04 harro Updated [Location, Embed code]
23-Aug-2013 19:11 harro Updated [Time, Aircraft type, Operator, Embed code, Narrative]
23-Aug-2013 19:13 harro Updated [Time, Narrative]
23-Aug-2013 19:17 harro Updated [Location, Source]
23-Aug-2013 19:27 harro Updated [Aircraft type]
23-Aug-2013 19:39 harro Updated [Narrative]
23-Aug-2013 20:08 harro Updated [Narrative]
23-Aug-2013 20:26 Black Typhoon Updated [Time, Total fatalities, Other fatalities, Departure airport, Source]
24-Aug-2013 05:15 Geno Updated [Location, Phase, Nature, Departure airport, Destination airport, Source, Narrative]
24-Aug-2013 06:13 harro Updated [Location, Damage]
24-Aug-2013 07:25 harro Updated [Nature, Source]
24-Aug-2013 09:54 JoeF Updated [Total fatalities]
28-Aug-2013 07:27 Anon. Updated [Narrative]
28-Aug-2013 09:50 Anon. Updated [Registration]
29-Aug-2013 00:55 Dr.John Smith Updated [Cn, Operator, Source, Embed code, Narrative]
29-Aug-2013 04:20 Stringfellow Updated [Cn]
30-Aug-2013 08:19 harro Updated [Embed code, Narrative]
31-Aug-2013 20:10 Geno Updated [Source]
08-Sep-2013 08:22 qualityman Updated [Source]
26-Sep-2013 18:12 TB Updated [Location, Source, Narrative]
13-Oct-2013 07:45 MarkStep Updated [Source]
02-Aug-2014 17:20 Aerossurance Updated [Source, Narrative]
22-Aug-2014 09:48 Aerossurance Updated [Source]
20-Jun-2015 08:52 Aerossurance Updated [Source, Narrative]
21-Aug-2015 18:10 Aerossurance Updated [Source, Narrative]
25-Sep-2015 16:35 Dr. John Smith Updated [Operator, Source, Embed code]
02-Oct-2015 23:22 Dr. John Smith Updated [Embed code]
22-Dec-2015 11:54 Aerossurance Updated [Location, Narrative]
15-Mar-2016 14:21 Aerossurance Updated [Time, Departure airport, Source, Narrative]

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