CHC Helikopter Service Flight 241

CHC Helikopter Service Flight 241
A Eurocopter EC225LP Super Puma similar to the one that crashed
Accident
Date 29 April 2016 (2016-04-29)
Summary Gearbox failure, rotor separation
Site Skitholmen, Øygarden, Hordaland, Norway
60°27′8″N 4°55′49″E / 60.45222°N 4.93028°E / 60.45222; 4.93028Coordinates: 60°27′8″N 4°55′49″E / 60.45222°N 4.93028°E / 60.45222; 4.93028
Aircraft
Aircraft type Eurocopter EC225LP Super Puma
Operator CHC Helikopter Service
ICAO flight No. HKS241
Call sign HELIBUS 241
Registration LN-OJF
Flight origin Flesland Airport, Bergen, Norway
Stopover Gullfaks B platform, North Sea
Destination Flesland Airport, Bergen, Norway
Occupants 13
Passengers 11
Crew 2
Fatalities 13
Survivors 0

On 29 April 2016, a CHC Helikopter Service Eurocopter EC225 Super Puma helicopter, carrying oil workers from the Gullfaks B platform in the North Sea, crashed near Turøy, a Norwegian coastal island 36 kilometres (22 mi) from the city of Bergen. The main rotor assembly detached from the aircraft and the fuselage plummeted to the ground, exploding on impact.[1][2] All thirteen people on board were killed.[3]

The subsequent investigation concluded that a gear in the main rotor gearbox had failed due to a fatigue crack that had propagated under-surface, escaping detection. Various safety recommendations were made, including for Airbus Helicopters, the current manufacturer of the type, to consider redesigning the affected gearbox.

Aircraft

The accident aircraft was an EC225LP Super Puma helicopter, manufactured by Eurocopter (now named Airbus Helicopters), registration LN-OJF.[4][5]

Background

At 10:05 local time (UTC+2), HKS241 took off from Bergen's Flesland Airport, five minutes behind schedule. It arrived at the Gullfaks B platform on time and departed at 11:16, carrying two pilots and eleven passengers, employees and subcontractors of Norwegian oil company Statoil.[6] It was scheduled to land back at Flesland Airport at 12:08.[1]

Crash

At 11:53, as the helicopter approached Sotra off the coast of Bergen, several witnesses observed the flight, stating that nothing was out of the ordinary until the sound suddenly changed and the helicopter started to sway. Moments later the main rotor assembly of the helicopter detached, causing a sudden drop in speed and altitude, as confirmed by flight telemetry. With all control lost, it crashed on the islet of Skitholmen between the islands of Turøy and Toftøy at 11:54:35 local time and exploded on impact.[2] Most of the wreckage then slid off the islet into the sea. A video recording of the detached main rotors spinning to earth was made shortly afterwards.[6] The rotor came to rest several hundred metres away on the island of Toftøy. According to flight tracking data, the time between the detachment of the rotor and the crash itself was only eleven seconds, with the helicopter diving 640 metres (2,100 ft) in that time.[2]

Response

At 11:55, local police received reports of a helicopter crash. Six minutes later, at 12:01, this was relayed to the national rescue service. Rescue workers, police and fire fighters arrived at the scene at 12:20, and the wreckage was located partially submerged soon after. At 13:15, authorities confirmed that the wreckage had been found, and that they did not expect to find survivors.[2]

Norwegian Prime Minister Erna Solberg described the crash as "horrible". King Harald V and Queen Sonja cancelled a visit to Sweden[4] that was to have marked King Carl XVI Gustaf's 70th birthday.

Crew and passengers

On its final flight the aircraft was carrying eleven passengers and two pilots.[7] Authorities confirmed that eleven of the people on board were Norwegian, with one British passenger and one Italian crew member. The eleven passengers were employees of six different companies: Halliburton (four employees); Aker Solutions (three); and one employee each of Statoil, Schlumberger, Welltec and Karsten Moholt. On 2 May the names of all the crash victims were released.[8]

Investigation

The Norwegian Accident Investigation Board (AIBN) is responsible for investigating aviation accidents in Norway.[9] The British Air Accidents Investigation Branch (AAIB) and French Bureau d'Enquêtes et d'Analyses pour la Sécurité de l'Aviation Civile (BEA) each dispatched a team of investigators to Norway to assist the AIBN in its investigation. Representatives from Airbus Helicopters and engine manufacturer Turbomeca were part of the BEA team.[10][11] The European Aviation Safety Agency (EASA) also participated in the investigation.[12]

The aircraft's combined cockpit voice recorder (CVR) and flight data recorder (FDR) was sent to the AAIB in the United Kingdom for data retrieval.[13] Data were successfully downloaded on 1 May and sent back to the AIBN which confirmed that the received data were of good quality and useful for further investigation.[14]

On 1 May, the BBC reported that the helicopter had been forced to land on 26 April, over fears of a technical problem after a cockpit warning light had illuminated a few minutes into a flight.[15]

In a press conference on 3 May, the AIBN stated that the initial investigation and analysis of data from the combined FDR and CVR convinced them that pilot error could be ruled out and that there were no indications of any malfunction until one second before the end of the recording, which they assumed was the moment when the rotor detached.[16][17] An AIBN spokesman said the accident was down to a technical fault and "not an accident caused by human error".[18] Later that day Airbus Helicopters updated their press release bulletin with a request for verification of the correct installation of all main gearbox suspension bar attachments for the EC225LP. They also stated that "similar measures will be published shortly for the EC725AP in a specific ASB" (Alert Service Bulletin).[19]

Within a week of the accident, an underwater sled with magnets had been developed and deployed to find small critical metal fragments from gearbox and bearings to support the investigations.[20]

On 27 May the AIBN confirmed that scenarios under consideration included failure of epicyclic module, suspension bar (lift strut) attachment and MGB (gearbox) conical housing.[21] On the same day Airbus Helicopters updated their press release bulletin and stated that in their opinion only failure of the attachment of a suspension bar could be assessed as probable based on the information available by that date,[19] an opinion also stated by Airbus during a safety meeting on 20 May.[22][23]

On 1 June the AIBN released an update to the preliminary investigation report including an urgent safety recommendation to the European Aviation Safety Agency. The recommendation was based on metallurgical examinations where signs of fatigue in parts of the second stage planet gear were found.[24]

The gearbox had suffered "unkind treatment" (road accident) during transport in Australia, and was repaired before being mounted in LN-OJF.[25] On 15 June, Airbus requested operators to check for metal residue in oil and to report unusual gearbox events.[26]

On 28 June the AIBN released a new preliminary report where they stated that the most likely cause to the accident was a fatigue fracture in one of the second stage planet gears. They had not yet determined what initiated the fracture.[27][28] AIBN draws similarity to the 2009 Bond Helicopters Eurocopter AS332 crash, also caused by a gearbox fracture. Whereas particles had been detected in the Scottish gearbox's oil prior to the crash, no such indication was present for the Norwegian gearbox.[29] As of February 2017, AIBN continued investigations with no indication of when a conclusion could be made.[30][31] Also in February 2017, EASA issued a notice for operators to investigate the oil cooler for 16NCD13 alloy from the gearbox.[32][33]

On 28 April 2017 the AIBN released a new preliminary report with an update of the investigation progress one year after the accident. In this report they stated that the accident was a result of a fatigue fracture in one of the eight second stage planet gears in the epicyclic module of the main rotor gearbox and that the crack initiation appeared to be a surface micro-pit. The origin of the micro-pit was considered unknown at the time when the report was published.[34] Also unknown is whether the fracture occurred momentarily or over several flight hours, and whether fracture fragments were spalled for detection by maintenance systems as happened in G-REDL. The issue is related to the airworthiness certificate of the aircraft.[35]

On 5 July 2018 the AIBN released the final report, they determined the cause as the following: The accident was a result of a fatigue fracture in a second stage planet gear in the epicyclic module of the main rotor gearbox. Cracks initiated from a micro-pit at the surface and developed subsurface to a catastrophic failure without being detected. 12 recommendations were made, one of the recommendations stated that Airbus should take another look at the design of the main gearbox of the Super Puma.[36]

Aftermath

Shortly after the accident oil companies and helicopter operators voluntarily grounded similar helicopters until further notice,[37] except for aircraft being used for search and rescue purposes.[38] This was later followed by a grounding by the Civil Aviation Authority of Norway, specified to public transport flights and commercial air transport operations with EC225LP helicopters.[39] Later that day the British Civil Aviation Authority issued a Safety Directive which grounded all EC225LP helicopters on the United Kingdom Civil Aircraft Register, or flying in United Kingdom airspace, except for aircraft being used for search and rescue purposes.[40][41] On 30 April, Airbus Helicopters issued a Safety Information Notice expressing their support of the decision to put all commercial passenger flights with Super Puma helicopters of model EC225LP "on hold". Other versions of the Super Puma were not included in this decision.[42]

On 1 May Airbus Helicopters stated in a press release that "Considering the additional information gathered during the last 48 hours, Airbus Helicopters’ decision, at this stage, is to not suspend flights of any nature for the EC225LP". They did not specify the nature of the additional information leading to this decision.[19]

On 11 May the Norwegian Civil Aviation Authority and the UK Civil Aviation Authority jointly agreed to extend the grounding, now also including Super Puma helicopters of model AS332L2.[43][44] The decision was based on similarities between the two helicopter models.

On 2 June the Norwegian Civil Aviation Authority and the UK Civil Aviation Authority extended the grounding of EC225LP and AS332L2 helicopters, now also including search and rescue flights.[45][46] The updated directives were results of a recommendation in the preliminary report published by the AIBN on 1 June.[24] Later that day the European Aviation Safety Agency decided to prohibit all flights with EC225LP and AS332L2 helicopters in Europe.[47][48] On 3 June the US Federal Aviation Administration (FAA) issued a directive prohibiting flights with EC225LP and AS332L2 helicopters.[49][50]

The similar military Eurocopter AS532 Cougar and Eurocopter EC725 of Germany and Brazil were grounded around 7 June in response to the accident,[51] and the South Korean Surion was grounded in July 2016.[52] By July 2016, 80% of the world fleet was on ground. The French military continued to operate its fleet.[53]

Statoil, who had contracted the helicopter in the crash, permanently ceased use of the Super Puma family of helicopters, even after some restrictions were lifted, and stated their plans were instead to use the Sikorsky S-92 helicopter to replace the Super Puma in contracts going forward.[54]

As of January 2017, the H225 remains grounded in the U.K. and Norway, and some had returned to service in Asia.[55]

See also

References

  1. 1 2 "Helikopterstyrt i Hordaland – 13 bekreftet omkommet" [Helicopter crash in Hordaland – 13 confirmed dead]. Verdens Gang (in Norwegian). 29 April 2016. Retrieved 29 April 2016.
  2. 1 2 3 4 Lura, Christian; Bolstad, Jon; Njåstad, Marthe; Nave, Ingvild (29 April 2016). "Politiet: Alle 13 er trolig omkommet" [Police: All 13 are probably dead] (in Norwegian). NRK. Retrieved 29 April 2016.
  3. ↑ Pryser Libell, Henrik; Karasz, Palko (29 April 2016). "Helicopter Crashes Off Norway, Leaving No Signs of Survivors". The New York Times. Retrieved 29 April 2016.
  4. 1 2 "Norway helicopter crash: 13 killed near Bergen". BBC News Online. Retrieved 29 April 2016.
  5. ↑ "Photo of LN-OJF". Jetphotos.net. Retrieved 6 May 2016.
  6. 1 2 "La hélice del helicóptero que se estrelló en Noruega se desprendió en vuelo" [The rotor of the helicopter that crashed in Norway came off in flight]. El País (in Spanish). 30 April 2016. Retrieved 1 May 2016.
  7. ↑ Malm, Sara; Gordon, Amie (29 April 2016). "Norway helicopter crash kills 11 people including Briton". Daily Mail. Associated Press. Retrieved 29 April 2016.
  8. ↑ "Dette er de omkomne" [These are the crash victims] (in Norwegian). nrk.no. 30 April 2016. Retrieved 30 April 2016.
  9. ↑ "Aviation". Accident Investigation Board Norway. Retrieved 29 April 2016.
  10. ↑ "The AAIB is deploying a small team to assist the Norwegian AIBN". Air Accidents Investigation Branch. Retrieved 29 April 2016.
  11. ↑ "The Helicopter Accident: The work continues". Statens Havarikommisjon for Transport. Retrieved 1 May 2016.
  12. ↑ "Accident of an Airbus Helicopter EC225 in Norway - Update". European Aviation Safety Agency. 2 June 2016. Retrieved 2 June 2016.
  13. ↑ "Helikopterulykken: Havarikommisjonen har startet arbeidet på ulykkesstedet" [Helicopter Accident: AIBN has started work on accident] (in Norwegian). Statens Havarikommisjon for Transport. Retrieved 29 April 2016.
  14. ↑ "The Helicopter Accident: Data from the combined FDR and CVR retrieved. Data is of good quality". Statens Havarikommisjon for Transport. 2 May 2016. Retrieved 2 May 2016.
  15. ↑ "Super Puma crash: Helicopter 'showed warning light'". Bbc.co.uk. 1 May 2016. Retrieved 1 May 2016.
  16. ↑ "Fatal helicopter crash off Norway due technical error: investigators". Reuters. 3 May 2016. Retrieved 3 May 2016.
  17. ↑ "Rotoren forsvant på et sekund" [The rotor disappeared in one second] (in Norwegian). Bergens Tidende. 3 May 2016. Retrieved 3 May 2016.
  18. ↑ "Fatal helicopter crash 'caused by technical fault'". STV. 3 May 2016. Retrieved 3 May 2016.
  19. 1 2 3 "ACCIDENT IN NORWAY". Airbus Helicopters. 27 May 2016. Archived from the original on 31 May 2016. Retrieved 28 May 2016.
  20. ↑ Tore Stensvold (20 February 2017). "Havarikommisjonen fant ikke alle delene etter Turøy-ulykken – utviklet unikt verktøy". Teknisk Ukeblad. Retrieved 20 February 2017.
  21. ↑ "The Helicopter Accident: Updated preliminary report". Statens Havarikommisjon for Transport. 27 May 2016. Retrieved 27 May 2016.
  22. ↑ "Airbus-sjef frikjente girboksen. 12 dager senere kom rapporten som indikerer det motsatte". Teknisk Ukeblad. 9 June 2016. Retrieved 11 June 2016.
  23. ↑ Anders Røsok. "Ekstraordinært møte i Samarbeidsforum for helikoptersikkerhet på norsk kontinentalsokkel 20.mai 2016" Civil Aviation Authority of Norway, 20 May 2016
  24. 1 2 "The Helicopter Accident: New preliminary report". Statens Havarikommisjon for Transport. 27 May 2016. Retrieved 27 May 2016.
  25. ↑ "Hovedgirboksen "ublidt behandlet" under transport - måtte tilbake på verksted før den ble montert i ulykkeshelikopteret". Teknisk Ukeblad. 2 June 2016. Retrieved 11 June 2016.
  26. ↑ "Hastemelding fra Airbus: Sjekk om girkassa har vært utsatt for noe "uvanlig"". Teknisk Ukeblad. Retrieved 16 June 2016.
  27. ↑ NTB (28 June 2016). "Havarikommisjonen: Utmattingsbrudd forårsaket helikopterulykken". Retrieved 29 June 2016.
  28. ↑ "Investigation of helicopter accident at Turøy near Bergen in Hordaland county, Norway". Accident Investigation Board Norway. 28 June 2016. Retrieved 14 August 2016.
  29. ↑ "Klare likheter mellom to fatale Super Puma-ulykker". Teknisk Ukeblad. Retrieved 22 July 2016.
  30. ↑ https://www.aibn.no/Aviation/Investigations/16-286
  31. ↑ Thierry Dubois (2 February 2017). "AIBN struggles with metallurgical analysis in H225 investigation". Vertical Magazine. Retrieved 4 February 2017.
  32. ↑ http://ad.easa.europa.eu/ad/2017-0042
  33. ↑ https://www.bbc.co.uk/news/uk-scotland-north-east-orkney-shetland-39106837
  34. ↑ "Investigation of helicopter accident at Turøy near Bergen in Hordaland county, Norway". Accident Investigation Board Norway. 28 April 2017. Retrieved 28 April 2017.
  35. ↑ "Turøy-ulykken: På disse punktene er havarikommisjonen og Airbus Helicopters fortsatt uenige". Teknisk Ukeblad. 8 May 2017. Retrieved 8 May 2017.
  36. ↑ https://www.aibn.no/Aviation/Published-reports/2018-04
  37. ↑ "Eni Norge stanser helikoptertrafikk" [Eni Norge halts helicopter traffic] (in Norwegian). NRK. 29 April 2016. Retrieved 4 May 2016.
  38. ↑ "Norway, UK suspend H225 operations following crash". Flight International. 30 April 2016. Retrieved 1 May 2016.
  39. ↑ "The Norwegian CAA issues Safety Directive on EC225LP". Luftfartstilsynet. 29 April 2016. Archived from the original on 19 May 2016. Retrieved 4 May 2016.
  40. ↑ "UK Super Pumas grounded after Norway crash leaves 13 dead". Independent Television News. Retrieved 29 April 2016.
  41. ↑ "Safety Directive Number: SD–2016/001" (PDF). Civil Aviation Authority. Archived from the original (PDF) on 5 May 2016. Retrieved 29 April 2016.
  42. ↑ "Safety Information Notice No. 3030-S-00" (PDF). Airbus Helicopters. 30 April 2016. Retrieved 1 May 2016.
  43. ↑ "Safety and operational directive No. 16/05616-5" (PDF). Luftfartstilsynet. 11 May 2016. Retrieved 11 May 2016.
  44. ↑ "Offshore helicopter restrictions extended". Civil Aviation Authority (United Kingdom). 11 May 2016. Retrieved 11 May 2016.
  45. ↑ "SAFETY AND OPERATIONAL DIRECTIVE - Airbus Helicopters EC225LP and AS332L2 - Limitation of all operations in the Kingdom of Norway due to fatal accident on the 29th of April 2016" (PDF). Luftfartstilsynet. 1 June 2016. Retrieved 2 June 2016.
  46. ↑ "Airbus Helicopters EC225LP and AS332L2 Limitations of Operations due to a Fatal Accident in Norway on 29 April 2016" (PDF). Civil Aviation Authority (United Kingdom). 2 June 2016. Archived from the original (PDF) on 17 June 2016. Retrieved 2 June 2016.
  47. ↑ "Update regarding the crash of a Norwegian Helicopter on 29 April 2016". European Aviation Safety Agency. 2 June 2016. Retrieved 2 June 2016.
  48. ↑ "2016-0104-E : [Correction] FLIGHT PROHIBITION". European Aviation Safety Agency. 9 June 2016. Retrieved 16 June 2016.
  49. ↑ http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgad.nsf/0/e8afb3f556876b0b86257fc7006d82e2/$FILE/2016-12-51_Emergency.pdf
  50. ↑ "EMERGENCY AIRWORTHINESS DIRECTIVE" (pdf). 3 June 2016. Retrieved 14 August 2016.
  51. ↑ "HeliHub German and Brazilian military ground AS532 and H725M". Retrieved 11 June 2016.
  52. ↑ "H225 crisis grounds South Korea's Surion". 8 July 2016. Retrieved 22 July 2016.
  53. ↑ "More bad news for Airbus Helicopters Super Puma family". FlightGlobal. 20 July 2016. Retrieved 22 July 2016.
  54. ↑ "Statoil drops Airbus Super Puma helicopters for good". Reuters. 6 Dec 2016. Retrieved 6 Dec 2016.
  55. ↑ Thierry Dubois (31 January 2017). "Airbus Helicopters CEO hopes for stable sales in 2017". Vertical Magazine. Retrieved 4 February 2017. the H225, which remains grounded in the U.K. and Norway
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