Turøy helicopter crash investigators find vital part / News / The Foreigner

Turøy helicopter crash investigators find vital part. As the investigation into the Eurocopter Super Puma tragedy continues, Norwegian divers discover a key piece of the aircraft’s gear mechanism. The EC 225 LP’s epicyclic gear second stage planet gear carrier (a type of holder inside the Main Gearbox - MGB) was found in the sea between the area of the main rotor separation and the crash site on 23rd February this year. This helicopter type is fitted with a sun and planet gearbox (called epicyclic gearing). It has a central shaft which drives the so-termed sun gear surrounded by eight small gears (called planet gears). These drive a ring gear around the outside of the entire gearbox.

h225, ec225, helicopter, bergen, crash, paywall



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Turøy helicopter crash investigators find vital part

Published on Thursday, 9th March, 2017 at 10:40 under the news category, by Michael Sandelson   .

As the investigation into the Eurocopter Super Puma tragedy continues, Norwegian divers discover a key piece of the aircraft’s gear mechanism.

The 2nd stage planet gear carrier
The 2nd stage planet gear carrier including the inner race belonging to the failed planet gear (to the right).The 2nd stage planet gear carrier
Photo: AIBN


The EC 225 LP’s epicyclic gear second stage planet gear carrier (a type of holder inside the Main Gearbox - MGB) was found in the sea between the area of the main rotor separation and the crash site on 23rd February this year.

This helicopter type is fitted with a sun and planet gearbox (called epicyclic gearing). It has a central shaft which drives the so-termed sun gear surrounded by eight small gears (called planet gears). These drive a ring gear around the outside of the entire gearbox.

Planet gears are mounted on a metal “carrier” plate that holds them together. The gearbox would suffer a catastrophic failure if one or more of the planet gears broke up.

According to the Accident Investigation Board Norway (AIBN), their examinations show that the accident was a result of a fatigue fracture in one of the eight second stage planet gears in this holder.

This supports their initial conclusions following the crash that it was not caused by human error.

“Several key components still missing”

13 people were aboard the helicopter (registration number LN-OJF) that was enroute to Bergen Flesland from Gullfaks B on 29th April 2016 when the Main Rotor Head (MRH) and mast suddenly detached from the aircraft (now called an H225).

2nd-stage planet gear main parts (without sungear)
2nd-stage planet gear main parts (without sungear)
AIBN
All perished in the ensuing crash, and manufacturer Airbus grounded all of their civilian traffic helicopters. The European Air Safety Agency (EASA) ordered Super Puma inspections following the disaster.

Norway’s Accident Investigation Board released their first preliminary report on 13th May. At that time, their focus was on examining the MRH suspension bar assembly, Main Gearbox, and main rotor head.

“However, several key components are still missing. A significant sea and land search is ongoing in order to retrieve these components,” it was stated.

The AIBN released an update to their preliminary report on 27th May, where they said that some key components were still missing.

“These components are in particular the epicyclical second stage planet gear carrier and parts of the forward suspension bar. […] At this stage, the AIBN can confirm that the scenarios under consideration include failure of epicyclic module, suspension bar (lift strut) attachment and MGB conical housing.”

Inspection routines

Another preliminary report was issued on 1st June. In it, they recommend carrying out inspections of the Main Gearbox.

An H225 helicopter
An H225 helicopter
Airbus Helicopters
“Recent metallurgical findings have revealed features strongly consistent with fatigue in the outer race of a second stage planet gear in the epicyclic module of the MGB. It cannot be ruled out that this signifies a possible safety issue that can affect other MGBs of the same type,” they wrote.

“The nature of the catastrophic failure of the LN-OJF main rotor system indicates that the current means to detect a failure in advance are not effective. The AIBN therefore recommends that EASA take immediate action to ensure the safety of the Airbus Helicopters H225 Main Gearbox,” added officials.

The European Air Safety Authority responded to this the same day, and issued and Airworthiness Directive (AD).

28th June saw a fourth preliminary report by the Accident Investigation Board. Officials said that “the accident most likely was the result of a fatigue fracture in one of the [eight] second stage planet gears.”

Some five months later, both the Norwegian and British CAAs maintained their respective EC225LP bans following EASA’s decision to permit use of this helicopter type.

Norway’s Accident Investigation Board has stated that it is not sure that present inspection routines would have uncovered the fault.

“It appears that the fracture propagated in a manner which was unlikely to be detected by the mandatory or supplementary systems intended for warning of an imminent failure,” they write.

The investigation continues.



Published on Thursday, 9th March, 2017 at 10:40 under the news category, by Michael Sandelson   .

This post has the following tags: h225, ec225, helicopter, bergen, crash, paywall.





  
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