Investigation of an aviation incident after departure from the Linus offshore oil installation on the Ekofisk field
On 5 June 2023 a Sikorsky S-92A helicopter had an uncommanded engine failure shortly after take-off from the offshore oil installation Linus platform near the Ekofisk field in the North-Atlantic.
LN-OMI had picked up passengers at platform Linus. Shortly after take-off, the crew heard a loud noise and were also notified by a warning light in cockpit that the left engine had stopped.
The crew determined that the engine had stopped and continued the flight on the other engine. An emergency message was sent to the air traffic service. It was decided to fly on one engine to Stavanger Airport, where they landed without further complications. No one was injured as a result of the incident.
The Norwegian Safety Investigation Authority (NSIA) visited the helicopter company the following day and started a preliminary investigation. As part of the ongoing preliminary investigation, an initial inspection of the helicopter's CT7-8 type engine was carried out in collaboration with the engine's manufacturer, General Electric, at the end of July.
The investigation revealed that twelve bolts joining the compressor and gas generator turbine had ruptured.
There are no known similar incidents with the engine type.
Based on the inspection of the engine, the NSIA has chosen to start a full investigation of the incident. It involves metallurgical and fracture engineering investigations.
Aft flange of the centrifugal Impeller. Photo: NSIA
Forward flange of the turbine shaft. Photo: NSIA
Overview engine. Illustration: General Electric
Close view of affected connection. Illustration: General Electric
Status of investigation
The NSIA has carried out a metallurgical examination of the twelve bolts. Fatigue has probably started in two of the bolts. The load then increased on the remaining bolts and after a while all twelve bolts ruptured.
So far it has not been possible to conclude about a possible cause.
No safety recomendation has been given so far in the investigation.
Latest update: 20.06.2024
Facts
| Occurrence date | 05.06.2023 |
| Aircraft | Sikorsky øvrige |
| Operator | Bristow Norway AS |
| Registration | LN-OMI |
| Meteorological conditions | IMC |
| County | Rogaland |
| Type of occurrence | Incident |
| Type of operation | Offshore |
| Category of operation | Heavy, helicopter (> 2 250kg) |
| Aircraft category | Helicopter, Multi-engine, Turboprop/turboshaft |
| FIR/AOR | ENSV (Stavanger ATCC) |