The Norwegian Safety Investigation Authority (NSIA) has published the report of its investigation into an oil loss incident on an S-92 operated by Bristow Norway in September 2020. The report says that the oil leak on the left side of the main gearbox was primarily the result of a washer erroneously left behind during earlier maintenance, blocking the flow of oil in the system’s oil passageway and impeding the flow of oil. Although the NISA was unable to define when the washer entered the gearbox, it was able to say that the last opportunity for it was nearly 500 flight hours earlier during work to the generator and accessory module and that, therefore, it had been in the oil system for at least that long before creating the problem.
Concluding its report, the NISA recommended to the Norwegian CAA that it follow with an examination of Bristow Norway’s maintenance procedures, especially those related to FOD control and, particularly, FOD control during gearbox maintenance.
