An emergency helicopter landing in Stavanger in 2020 was caused by a misplaced washer left in its gearbox, the Norwegian Safety Investigation Authority (NSA) has found.
On September 25, 2020, a Sikorsky S-92A helicopter operated by Bristow Norway made an emergency landing at Stavanger Airport Sola after a loss of oil pressure and overheating of the main gearbox.
The incident occurred as the helicopter descended from 7,000 ft to 1,000 ft during a return flight from the West Elara oil rig on the Eldfisk field.
After the helicopter was parked and the rotor had stopped, a significant oil leak on the left side of the main gearbox was identified.
The two pilots and three passengers onboard were unharmed.
Emergency landing investigation
During a subsequent investigation by the NSIA, a metal stop-washer was found within the oil system of the main gearbox.
The NSIA said the washer reduced the oil flow in the gearbox passageway and led to overheating, which eventually caused a seal to fail resulting in the leak.
In its report, the NSIA said it believes it is “likely that the washer entered the module in connection with maintenance“.
The NSIA could not establish exactly when the washer entered the gearbox and the report recommended the Norwegian CAA examine Bristow Norway’s procedures and routines related to foreign object debris (FOD).
“A helicopter gearbox is a safety-critical component and any possibility of foreign objects entering the gearbox must be avoided,” the report stated.
The release of the report comes after the International Association of Oil and Gas Producers (IOGP) recently warned its members “serious and deteriorating supply chain situation” is presenting safety issues for S-92 offshore helicopters, particularly in relation to gearbox replacements.
In response to the concerns raised by the IOGP, the UK Civil Aviation Authority and Offshore Energies UK told Energy Voice while the situation was “concerning”, the parts shortages were an operational issue and not necessarily a safety concern.