Date:	23-AUG-2013
Time:	18:17 LT
Type:	Eurocopter AS 332L2 Super Puma Mk2
Owner/operator:	CHC Scotia Ltd
Registration:	G-WNSB
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:	Offshore
Departure airport:	Borgsten Dolphin drilling rig
Destination airport:	Sumburgh Airport (LSI/EGPB)
Investigating agency:	AAIB
Confidence Rating:	Accident investigation report completed and information captured

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 helicopter’s instruments, in accordance with the Standard Operating Procedure (SOP) set out in the operator’s 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 helicopter’s airspeed. The co-pilot was responsible for monitoring the helicopter’s 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 helicopter’s 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 helicopter’s 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 commander’s 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:
•The helicopter’s 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.

•Visual 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 operator’s procedure for an instrument approach.


The following contributory factors were identified:
•The operator’s 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.

•The operator’s SOPs at the time did not optimise the use of the helicopter’s automated systems during a Non-Precision Approach.

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

•Despite 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.

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 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

Date/time	Contributor	Updates
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]
25-Dec-2020 14:51	harro	Updated [Nature]
24-Dec-2021 09:46	harro	Updated [Accident report]