S92, en-route, south southwest of Stavanger Norway, 2020

S92, en-route, south southwest of Stavanger Norway, 2020

Summary

On 25 September 2020, a Sikorsky S92A returning from an offshore platform was in descent approximately 40nm from destination Stavanger when main gear box low pressure and left engine oil temperature cautions were annunciated. The affected engine was reduced to idle and a MAYDAY declared. A further related alert prompted descent to 200 feet, and sixteen minutes after the initial malfunction, a normal landing was completed at Stavanger. A significant oil leak found in the main gear box was attributed to oil flow reduction and consequent overheating caused by a loose washer inadvertently left inside the gearbox during routine maintenance.

Description

On 25 September 2020, a Sikorsky S92A (LN-ONQ) operated by Bristow Norway on a North Sea offshore passenger transport flight from the West Elara oil platform to Stavanger had begun descent in daytime visual conditions (VMC) when main gear box (MGB) oil pressure and left engine oil temperature cautions were annunciated. Descent to 500 feet asl was made and a MAYDAY declared. When a more serious related warning then followed, further descent to 200 feet asl was made and maintained until reaching Stavanger, which was the nearest suitable landing option, where it became clear that a significant main gear box oil leak had occurred.

Investigation 

The occurrence was immediately reported to the Norwegian Safety Investigation Authority and a Serious Incident investigation was commenced with the combined voice and flight data recorder (CVFDR) removed and secured the same day. All data subsequently downloaded was of good quality and useful to the investigation.

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