Report on Aviation incident offshore by Ekofisk Lima in the North Sea on 25 September 2021 involving Sikorsky S-92A, LN-ONH operated by Bristow Norway AS
Aviation report 2022/08
On Saturday 25 September 2021 a Sikorsky Aircraft Corporation S-92A, LN-ONH, operated by Bristow Norway AS had completed SAR training and was returning to Ekofisk Lima. The helicopter experienced a sudden loss of oil pressure in the main gear box with related aural and visual warnings. The crew turned immediatly towards Ekofisk Lima for a short final and landing. The landing was performed without problems and no persons were injured. The investigation has found that the loss of oil pressure was due to the Vespel spline adapter driving one of the oil pumps was completely worn down.
The Norwegian Safety Investigation Authority sees it as likely that a combination of factors casued the excessive wear of the Vespel spline adapter. A higher service life on the component than logged, natural variation in production and materials of the Vespel spline adapter, and the individual torque load on the pump are all contributing factors.
The loss of oil pressure did not lead to immediate risk of failure of the main gearbox.
Sikorsky has after the incident adjusted the service life of the Vespel spline adapter to prevent reoccurence.
Published 23.09.2022
Facts
| Location | Offshore Norway, Ekofisk Lima |
| Occurrence date | 25.09.2021 |
| Aircraft | Sikorsky øvrige |
| Operator | Bristow Norway AS |
| Registration | LN-ONH |
| Meteorological conditions | VMC |
| Type of occurrence | Serious incident |
| Type of operation | Offshore |
| Category of operation | Heavy, helicopter (> 2 250kg) |
| Aircraft category | Helicopter, Multi-engine |