AIBN believes that the helicopter accident on Turøy most likely was caused by a fatigue fracture in a planetary gear. The gearbox has been involved in a traffic accident before the crash.
It is the conclusion of a new report from the Accident Investigation Board.
“At this stage of the investigation finds AIBN is most likely that the accident was caused by a fatigue fracture in one of the eight second stage planetgearene. The fatigue seems to have evolved without this being captured by the existing or additional systems to warn of errors that are under development. It has not been determined how the fracture occurred “reads a press release Tuesday night.
The gearbox was in traffic accident
Another new and startling data that appears in the report is that the gearbox aboard the casualty helicopter was involved in a traffic accident on the way in 2015. the AIBN does not provide more information on this accident, beyond that it is aware that it has happened.
“the gearbox was inspected, repaired and released for flight by the manufacturer before it was installed in LN-OJF in January 2016. Whether there is a connection between this incident and the introduction and growth of a fatigue crack is under investigation” writes AIBN in its report .
the AIBN also refers to several similarities between the accident at Turøy and crash off Scotland in 2009.
also in 2009 loosened the rotor of a Super Puma helicopter in the North Sea. 16 people were killed in the crash outside Scotland. the investigation report points to the same failure as the helicopter that crashed at Turøy: Fatigue fracture of the upper set of planetary gearbox.
BT has previously described possible explanations for plane crash in a briefed article.
the gearbox contains several so-called planetary. That freewheel rotates inside a larger sun gear. Planetary function is to reduce the speed of the motor to the rotor. Engine runs at 23,000 rpm, while the rotor is 265 rpm. This means that the main gearbox are subjected to enormous forces.
1. June sent AIBN out a new preliminary report on the accident at Turøy 29 April. 13 people were killed in the crash.
After completing metallurgical testwork parts gearbox, believes AIBN having found clear signs of fatigue fracture of a planetary gear.
BT comes back with more.