Thirteen On Board Were Fatally Injured, Three Possible Scenarios Under Consideration

The Norwegian Accident Investigation Board has updated its preliminary report from an accident involving an Airbus Helicopters H225 in which the Main Rotor Head (MRH) and mast suddenly detached from the aircraft enroute from the Gullfaks B oil rig to Bergen Airport Flesland. The helicopter impacted on a small island east of Turøy. All 13 people on board were fatally injured.

AIBN is now performing detailed examinations of particular components of the helicopter. The examinations are performed in Norway, England and France. The organized search for parts on land and in the sea is temporarily paused. However, important components are still missing, and the AIBN will likely resume the search in June.

According to the report, the helicopter was cruising at 2000 ft when the Main Rotor Head (MRH) and mast suddenly detached. The helicopter impacted on a small island and caught fire. The main wreckage thereafter ended in the sea where it came to rest at a depth of 1-9 meters. The accident was not survivable.

The recordings on the CVFDR showed that everything appeared to be normal until a sudden catastrophic failure developed in 1-2 seconds. The CVFDR recordings ended abruptly at the same time. There are no indications that flight crew actions were a factor in the accident. A spectral analysis of the CVR data has been carried out. There was no obvious indication of an abnormality before the sudden detachment of the rotor head.

On May 5, all the retrieved parts from the helicopter wreckage were taken from Haakonsvern to the AIBN premises in Lillestrøm, where all parts of particular interest for the investigation have been selected for more detailed inspections/examinations.

The AIBN has collected and secured relevant maintenance documentation. This material is currently the subject of a thorough analysis in parallel with the technical examinations. Detailed metallurgical examinations have been ongoing since 19 May, but are still at an early stage. So far, these examinations have not identified a conclusive primary cause of the accident.
Preliminary Analysis

The investigation team has discussed a list of scenarios that Airbus Helicopter prepared based on fault tree analysis. At this stage, the AIBN can confirm that the scenarios under consideration include failure of epicyclic module, suspension bar (lift strut) attachment and MGB conical housing.

(Images provided with AIBN report)

FMI: www.aibn.no/Aviation/Investigations/16-286?iid=19830&pid=SHT-Report-Attachments.Native-InnerFile-File&attach=1