Report on aviation accident in the North Sea on 23 November 1977 with Sikorsky S-61N, LN-OSZ
Aviation report 1979/05
LN-OSZ took off from Forus on 23 November 1977 at 09:09 with a crew of 2 and 10 passengers. The purpose was to follow the usual route to Ekofisk Charlie. At 09:31, Stavanger radio had its last contact with the helicopter. Stavanger radio reported it missing when the helicopter did not report the next checkpoint at the expected time. Approximately one hour after the last radio contact, another helicopter traveling from Ekofisk to Forus observed wreckage in the water, which was later confirmed to be from LN-OSZ. None of those on board survived the accident.
LN-OSZ was to fly at 500 feet to Ekofisk Charlie. The wreckage and extent of damage suggest that the helicopter was flying relatively level over the sea, at a high speed, with minimal descent, and in the same direction as its original course.
Despite extensive investigations and a comprehensive analysis of potential contributing factors by the accident investigation board they have been unable to determine why the helicopter crashed into the sea.
The weather was relatively poor, but other helicopters were flying in the area without issues both before, during, and after the accident. Therefore, the accident investigation board believes that the weather was not a significant contributing factor to the accident. The crew was in good condition, well-rested, and had the necessary qualifications to conduct the flight. Additionally, no signs of technical failure have been found that could explain why the helicopter crashed into the sea.
Published 03.05.1979
Facts
| Location | The North Sea |
| Occurrence date | 23.11.1977 |
| Aircraft | Sikorsky S-61 |
| Operator | Helicopter Service AS |
| Registration | LN-OSZ |
| Meteorological conditions | VMC |
| County | Annet/offshore |
| Type of occurrence | Accident |
| Type of operation | Commercial, other |
| Category of operation | Heavy, helicopter (> 2 250kg) |
| Aircraft category | Helicopter, Multi-engine |
| FIR/AOR | ENOB (Bodø FIC/OFIR) |