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EC225 crash near Bergen, Norway April 2016

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EC225 crash near Bergen, Norway April 2016

Old 4th Nov 2016, 07:46
  #1621 (permalink)  
 
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Old 4th Nov 2016, 13:32
  #1622 (permalink)  
 
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Glad that's over.
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Old 12th Dec 2016, 05:40
  #1623 (permalink)  
 
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Thread refreshed

https://www.verticalmag.com/news/airbus-helicopters-sued-three-companies-h225-situation/#sthash.esg0Blh2.dpuf

link copied from other thread for discussion (for pablo332)
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Old 12th Dec 2016, 11:13
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Originally Posted by Concentric View Post
https://www.verticalmag.com/news/airbus-helicopters-sued-three-companies-h225-situation/#sthash.esg0Blh2.dpuf

link copied from other thread for discussion (for pablo332)
Thank you. For some reason I couldn’t find the thread in the 4 pages of Rotorhead threads. Now I can answer my own question.
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Old 12th Dec 2016, 16:38
  #1625 (permalink)  
 
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Could anyone confirm the alleged bad -07 part number was manufactured by FAG and the alleged good -06 part number was manufactured by Timken?
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Old 13th Dec 2016, 16:29
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Originally Posted by Pablo332 View Post
Could anyone confirm the alleged bad -07 part number was manufactured by FAG and the alleged good -06 part number was manufactured by Timken?
Given the litigation already starting, particularly with AH view of "defamation" I wouldn't advise anyone to answer that question TBH, only insiders at AH would be privy to that information and it wouldn't be wise to put one of them in a vulnerable position.
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Old 14th Dec 2016, 00:27
  #1627 (permalink)  
 
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Does anyone know if it was a -06 part number that was the cause of the G-REDL accident?
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Old 28th Dec 2016, 09:18
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At sixes and sevens.

It is difficult to say (even for those who know, perhaps) if it was an -06 gear/bearing that failed in G-REDL. The people who should know that are the UK AAIB.

In their report 2-2011, (page 51 Section 1 – Factual Information), Figure 21 shows a photograph of the remaining 7 gears still attached to the 2nd stage carrier. A number of those gear/bearings can be seen in the photo to carry a particular manufacturer’s markings, though that on the inner race of the failed gear is less distinct but similar in position and spacing. In Figure 22 the AAIB showed a “complete undamaged gear for reference”. This can clearly be seen to carry the part number (7 o’clock position) ending 3335-06. The inner race does not appear to carry manufacturer’s markings, unlike those in the previous photo.

At the time this report was published that did not appear to be significant. However in the light of AH mandating the removal from service of all epicyclic modules containing one or more of specific planet gear/bearing part numbers (and return of those to AH for gear replacement), some searching questions need to be asked. Evidently one operator (currently involved in a law suit against AH) chose to hang on to some of those parts and conduct their own examinations.

So, if the failed gear was a type -06 and the reference gear clearly an -06, why would AH maintain the -06 as the only authorised part?

Or, if the failed gear was actually a type -07 (or an -02, -03, or -05 as detailed in EASB 63A030), was the AAIB aware in 2011 that there were differences in the parts and specifically as stated in the above EASB?

“-The detailed design of the planet gear bearing has an increased damage tolerance.
-Modeling and calculation reveal a lower load level on the external race of the planet gear bearing.
-In-service experience shows enhanced reliability”.

The report (1.16.2, page 60) states that “a detailed analysis, using advanced methods, was undertaken by the helicopter manufacturer to build a three-dimensional stress model of the component. A separate analysis tool was used for the Hertzian stresses”

Given the stated differences in damage tolerance and reliability in the EASB, which part number did the manufacturer model and analyse for the AAIB?

The REDL investigation had access to two planet gears from other L2 MGBs (why not EC225s with their higher loading?). These had been “previously sectioned” by the helicopter manufacturer (ref P62) but it does not state when. Which part number was that sectioned 2nd stage planet gear/bearing?

I do not expect anyone on here to answer those questions but I sincerely hope that the Norwegian AIBN and other involved agencies do seek those answers.
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Old 29th Dec 2016, 09:08
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https://www.eveningexpress.co.uk/fp/news/local/north-sea-helicopter-crash-no-correlation-previous-accident-investigators-say/
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Old 29th Dec 2016, 09:28
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For busy people who don't read past headlines, the "previous accident" referred to was the road transportation accident, not the previous (or any similar) helicopter crash. To equate one with the other is sloppy journalism, as is the statement "The crash was the first fatal helicopter incident involving the offshore industry in 19 years." In the Norwegian sector, possibly.
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Old 29th Dec 2016, 13:36
  #1631 (permalink)  
 
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We don't do newspapers in the North East.
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Old 3rd Feb 2017, 10:46
  #1632 (permalink)  
 
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Brief update on the investigation from the AIBN, 2nd of February 2017

A very brief statement on their website yesterday goes something like:

... The investigation so far has shown that the accident was the result of a fatigue fracture in one of the eight second stage planet gears in the main gear box, a failure with clear similarities with the crash off the coast of Scotland in 2009 with G-REDL. The fatigue crack developed without this being captured by the existing required or supplementary warning systems.

The investiagation is complex and with a broad scope. So far, the metallurgical studies has had the major focus. That is efforts to map and understand how the fatigue crack initiated and developed. This work is not yet completed.

Currently, the main focus of the AIBN investigation is the certification of the main gearbox and the robustness of the previous and current design requirements. This includes follow-up of safety recommendations given by the AAIB in connection with the accident with G-REDL and an assessment of the continuous follow-up of the gear box reliability. This work requires a close collaboration with the responsible parties, primarily the helicopter manufacturer and EASA.

The scope and complexity of the investigation means that it is not yet possible to estimate a date for when the final report is completed. The investigation continues with the same high activity. The Aviation Authorities in Norway and Europe are continually updated about the investigation.

AIBN intends to publish a new preliminary report on the 29 April 2017, unless significant new discoveries necessitates a preliminary report earlier.
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Old 3rd Feb 2017, 21:41
  #1633 (permalink)  
 
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... The investigation so far has shown that the accident was the result of a fatigue fracture in one of the eight second stage planet gears in the main gear box, a failure with clear similarities with the crash off the coast of Scotland in 2009 with G-REDL. The fatigue crack developed without this being captured by the existing required or supplementary warning systems.
Where does that take us?

Shy of small enough bits breaking off the Gear is there anyway the existing detection and monitoring systems would ever work to prevent such a thing from leading to a Catastrophic failure?
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Old 4th Feb 2017, 03:52
  #1634 (permalink)  
 
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The existing systems for monitoring gearbox degradation have demonstrably failed twice with fatal results. The environment in the North Sea is probably harsher than the designers appreciated, with more frequent shock loading of drivetrain components accelerating fatigue crack spreading once a chip or stress point has been formed.

Other areas where helicopters operate in harsh conditions seem to have more stable bad weather. Wind speeds may be higher, but they are more constant. Temperatures also tend to remain more stable over a period of weeks or months. The North Sea can be relatively temperate on day and below freezing the next. Similarly wind speeds are very variable ranging from dead calm to a full storm in a matter of a couple of hours with frequent gusts and squalls.

As usual the planetary gear components need to be hard to prevent wear while being ductile to absorb shock without fracturing. Selective heat treatment and surface hardening are the usual methods used to try and deliver both properties in ine component. A modern day version of damascus steel techniques from the middle ages used to manufacture swords that could cut without snapping when they hit armour. While x-ray, ultrasound and eddy current testing can give an indication that the components have been correctly manufactured, only destructive testing can provide absolute proof. So there is no way of providing an absolute guarantee that every component is flawless.

Chip monitoring and measurement of metallic waste contamination in the gearbox oil filters only works if conducted at frequent intervals and all the chips are actually collected. Even a single hardened metal chip can cause extremely rapid catastrophic destruction of a gearbox if it falls into the mesh between the planetary gears.

As it stands, this gearbox is operating too close to the technical limits of current metallurgy. Either the design needs to be radically changed or the operating limits downgraded, which would severely reduce the operation capabilities of the helicopter.
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Old 4th Feb 2017, 14:41
  #1635 (permalink)  
 
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It just doesn’t make any sense the unbiased pen pushers of EASA have declared the aircraft safe.

Why does this meddlesome non-member (and one soon to be non-member of the EEC) insist on rocking the boat? Money is at stake, sales are not doing well.

Think of the common cause you safety first out landers.
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Old 4th Feb 2017, 14:42
  #1636 (permalink)  
 
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Originally Posted by TipCap View Post
Very good points raised, Gouli
I'm afraid I disagree. Aircraft flying the North Sea normally sit overnight in hangars and are started up soon after being pulled out, so they're not cold soaked in low temperatures. Once started and at operating temperature, it's pretty irrelevant what the oat is. Wind? Explain to me how that can be considered a harsh environment - last time I checked there were rarely 155kt winds in that area, which is what the 225 spends most of its airborne time experiencing. Operating regime? What; flying in a straight line for two hours, hovering for a few seconds and landing? I think this is a better example of a harsh operating environment, with a much more diverse range of dynamic and structural flight loads:
https://m.youtube.com/watch?v=oGUbPdc5CI0
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Old 4th Feb 2017, 14:53
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Originally Posted by SASless View Post
Where does that take us?

Shy of small enough bits breaking off the Gear is there anyway the existing detection and monitoring systems would ever work to prevent such a thing from leading to a Catastrophic failure?
Who knows AH are willing to give it a shot.

Don’t think of it as a flight, think of it as expanding the envelope of human knowledge, who could resist?
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Old 4th Feb 2017, 14:55
  #1638 (permalink)  
 
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I found the first video to be a bit boring....but my Orang Tabby Cat, "JR Mewing" was intrigued and kept trying to catch the Rotor Blades flashing by at the top of the screen!

I would think the North Sea thing is being over blown beyond the Gearbox loading being fairly high but constant for long periods of time.

The stress on a Gearbox in Underslung work like Logging would be far greater in stresses I would imagine.
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Old 4th Feb 2017, 15:55
  #1639 (permalink)  
 
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The military don't fly their aircraft at MAUM and MCP everyday. Bear in mind that the 225 struggles into the air at 11t. AH don't have anyone who truly understands the oil and gas environment particularly the North Sea. Their luck ran out in 2009 and they are still struggling to understand why. They are still mystified why 2 national authorities are uncomfortable with the lack of a solid explanation. Let's remember in both fatal accidents they did everything they could to initially blame the operator. In fact, in 2012 they did the same and were reluctant to admit there was a problem with the MGB design until a different operator ditched a second aircraft. Sorry, a successful water landing according to AH. I think they make great helicopters but as a business when things go wrong, their arrogance is still outstanding. Perhaps it is cultural.
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Old 4th Feb 2017, 16:25
  #1640 (permalink)  
 
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Wind? Explain to me how that can be considered a harsh environment - last time I checked there were rarely 155kt winds in that area,

I have a friend who sold windmills made and tested on the Bay of Biscay coast.
He tried selling them in the Scottish Islands and found that the windmill blades could not cope. Apparently the instantaneous stresses suffered by the blades were much higher in Scotland although the overall environment did not appear to be that different.

Last edited by occasional; 4th Feb 2017 at 17:33.
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