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EC225 crash near Bergen, Norway April 2016

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EC225 crash near Bergen, Norway April 2016

Old 25th Apr 2017, 13:10
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Originally Posted by HeliComparator
Much as I like to score points with SAS on the S92 vs 225, I do hope this latest isn't a sudden catastrophic failure as that would seriously scupper N Sea ops. But it does show the dangers of having pretty much a one-horse town.

Obviously we have no idea yet but if it turns out to be CFIT during an instrument approach in bad weather, it does raise the question of whether one sort of fatal accident is worse than another. I'm thinking that, e.g. the Sumburgh L2 accident could have happened to both an L2 and an S92, but not to a 225. What if this accident could not feasibly have happened to a 225?

From the pilots' point of view, we hate the idea of a sudden rotor detachment as it's out of our control. Even though the probability of a CFIT is perhaps greater, we dismiss that as being something that couldn't happen to us because we are competent. And yet it still does.

From the passengers' point of view, I doubt that such a distinction is made since either scenario is out of their control.
From what the investigators have told us would seem some form of CFIT incident is much more likely here - no evidence so far of any technical failure
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Old 25th Apr 2017, 16:49
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Glad to hear that the new report is coming out. Hopefully it will shed some new light on this tragic event.

JOKE
Ok we need to divide our responses to the upcoming report.
Need volunteers for various groups. Tasking for each group, A to G, outlined below.
A) Reject any and all findings.
B) Correct any grammar, spelling or punctuation errors.
C) Explain why the 225 is the safest, most comfortable and longest range helicopter in the world.
D) Trash the S-92.
E) Call everyone else mouth drooling idiots.
F) Accept the report and compliment those who prepared it on their dedication and professional conduct.
G) The largest group ..to argue with groups A, B, C, D, E and F.
CLOSE JOKE
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Old 25th Apr 2017, 16:54
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You forgot group (H) - god complex.

Looking forward to the report, hopefully it will give more answers than questions...
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Old 25th Apr 2017, 17:10
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Helicrazi
Rotorheads is a forum that is the epitome of politeness and rational debate when compared to some other forums.
There is one forum on PPrune where posting "Great sunrise today, going to be a great day for flying!" will start a fight that will go on for 20-30 pages. Friendships will be torn assunder, reputations trashed, and folks will be challenged to duel to the death.
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Old 26th Apr 2017, 10:20
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Norway crash

https://www.energyvoice.com/oilandga...-crash-report/

Super Puma ban to remain in place following latest crash report...
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Old 26th Apr 2017, 13:55
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Originally Posted by sinnon7
https://www.energyvoice.com/oilandga...-crash-report/

Super Puma ban to remain in place following latest crash report...
As it says the AIBN is obliged to publish this report within a year of the accident.
It does seem that despite a huge effort we still only know what happened, not yet why.

“CAA UK and CAA NO continue to work closely on agreeing the next steps required to be sufficiently satisfied in order to remove our Operational Safety Directives.

Developments on the lifting and the detection capability look promising and we are hopeful that after obtaining further information we will be closer to removing our directives. At this time however the directives remain in place.

It would obviously be much easier for them if a specific reason for the failure could be established.
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Old 28th Apr 2017, 11:37
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New preliminary report out today.

https://www.aibn.no/Aviation/Investigations/16-286

"The observed failure mode in this accident, i.e. crack initiation and propagation with limited spalling, seems to differ from what was expected or foreseen during the design and certification of the main rotor gearbox. The fracture propagated in a manner which was unlikely to be detected by the maintenance procedures and the monitoring systems fitted to LN-OJF at the time of the accident."

Last edited by FNTC; 28th Apr 2017 at 11:54.
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Old 28th Apr 2017, 13:52
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AH has recently added a "Super Puma Information Centre" section to its website. This gives a lot more detail from them and information on the programme to return the H225 and H215 to service. This shows that out of the 341 aircraft affected 49% are now back in service whereas in O&G it is only 15%. Obviously one fact in this is location as many of those 127 are located in UK/Norway where they are formally grounded. The site show the hours being accumulated by the flying aircraft and the total hours accumulated by the types to date. It acknowledges that while they know what happened and have been able to introduce measures to mitigate the risk of a recurrence that more investigation needs to take place to understand why as FNTC noted "in a manner which was unlikely to be detected by the maintenance procedures and the monitoring systems fitted to LN-OJF at the time of the accident".

The failure mode was not what would be expected and despite a huge technical effort there is still no obvious "smoking gun". The metallurgical understanding of the events is now very thorough and it would seem that further work here offers the best chance of getting to the bottom of this one.
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Old 28th Apr 2017, 14:27
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Originally Posted by albatross
Tasking for each group, A to G, outlined below.
I think you left out the group that needs to advocate UAV/unmanned transport modes.
On a more serious note ...
The fracture propagated in a manner which was unlikely to be detected by the maintenance procedures and the monitoring systems fitted to LN-OJF at the time of the accident."
Addressing that is critical to restoring confidence in the aircraft. If you don't get a hint/warning that 'things are going wrong in the box full of metal gears' you don't get the chance to fix, or replace, that critical component. Ouch. (Best wishes to the engineers/designers in coming up with a mode/tool/kit that can address this "graceful degradation" issue).
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Old 28th Apr 2017, 14:58
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Originally Posted by birmingham
AH has recently added a "Super Puma Information Centre" section to its website. This gives a lot more detail from them and information on the programme to return the H225 and H215 to service. This shows that out of the 341 aircraft affected 49% are now back in service whereas in O&G it is only 15%. Obviously one fact in this is location as many of those 127 are located in UK/Norway where they are formally grounded. The site show the hours being accumulated by the flying aircraft and the total hours accumulated by the types to date. It acknowledges that while they know what happened and have been able to introduce measures to mitigate the risk of a recurrence that more investigation needs to take place to understand why as FNTC noted "in a manner which was unlikely to be detected by the maintenance procedures and the monitoring systems fitted to LN-OJF at the time of the accident".

The failure mode was not what would be expected and despite a huge technical effort there is still no obvious "smoking gun". The metallurgical understanding of the events is now very thorough and it would seem that further work here offers the best chance of getting to the bottom of this one.
My bold. I see these statements as contradictory.
If you don't know why it happened, how can you mitigate the risk of recurrence?
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Old 28th Apr 2017, 15:33
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Originally Posted by Twist & Shout
My bold. I see these statements as contradictory.
If you don't know why it happened, how can you mitigate the risk of recurrence?
They know what happened so they can definitely mitigate the risk - one type of mgb, reduced time between inspections etc. What you cannot do is to ensure prevention of a recurrence. That can indeed only be ensured when you know why.

I agree that is the basic difficulty here and unless the reason can be established and the problem definitively resolved it will be close to impossible to get this back in the NS O&G sector. Even then the damage may already have been done.

Last edited by birmingham; 28th Apr 2017 at 15:44.
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Old 28th Apr 2017, 15:58
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I'm amazed people still think there's a chance of its return, the industry has moved on.
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Old 28th Apr 2017, 17:32
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Originally Posted by helicrazi
I'm amazed people still think there's a chance of its return, the industry has moved on.
But moved where? Even in an O&G slump we've moved into an era of S-92 accidents. What happens if O&G activity picks up? I am very concerned about unintended consequences of hurried changes in fleet composition.
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Old 28th Apr 2017, 18:51
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Money talks, supermediums are the future, no need for 2 heavies, S92 is doing the job. Pax numbers reducing, gone are the days of full loads of 19 on every leg. Supermediums are filling the void, 225 has lost its place. If the industry picks up it all seems to be moving ESB or the Atlantic, which shuttling out of shetlands isn't a problem for the supermediums.
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Old 28th Apr 2017, 19:17
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Helicrazi

I think your last 2 points are on the money. Having spent 2 hours reading this report (it needs more study and it's an excellent factual piece of work) I cannot see myself making a recommendation to return the 225 to service to my BOD.

I wonder how similar the 175 MGB architecture is to the 225?
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Old 28th Apr 2017, 20:22
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Onceuponatime. 1981 or thereabouts, the North Sea was going to be infested with Sikorsky S76s. Range and payload-not enough.
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Old 28th Apr 2017, 22:26
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Originally Posted by birmingham
They know what happened so they can definitely mitigate the risk - one type of mgb, reduced time between inspections etc. What you cannot do is to ensure prevention of a recurrence. That can indeed only be ensured when you know why.

I agree that is the basic difficulty here and unless the reason can be established and the problem definitively resolved it will be close to impossible to get this back in the NS O&G sector. Even then the damage may already have been done.
I understand the sentiment, but what if the next rotor to detach is the other brand of gearbox with a TTIS of 35hrs?

They have taken steps they think might mitigate the likelihood of a reoccurrence, but if they don't know why it happened, they can't know if their recommendations will have any mitigating effect whatsoever.
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Old 28th Apr 2017, 22:36
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At 1.16.3.11 there is a description of the pattern of compressive stress in a FAG second stage epicyclic gear from OJF. There is no equivalent information for the SNR gear but a statement appears at the final paragraph of 1.6.8.3 that "differences in the finishing process performed by the suppliers can affect the outer race surface residual stress, with FAG having a significantly higher compressive stress at the race surface". The pattern described in 1.16.3.11 seems quite severe in that it appears to have sudden enough changes to be potentially damaging in this operating environment. It would be interesting to know what the equivalent stress pattern was for the SNR gears and the differences in process characteristics.

I wonder where else these factors occur.
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Old 28th Apr 2017, 22:49
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FED,

You are talking 76A's.....and a very long time ago.

Had the S-70 design been thought through and designed for the Civil Market along with the US Military....perhaps it would have been the 70 we were all driving around in.

Actually.....had the 61 been modernized perhaps they would still be flogging around the Oil Patch.

But....we are talking about what could have been.
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Old 29th Apr 2017, 01:38
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The detail in this report is amazing. The micrographs of the fracture surfaces absolutely stunning. I have never before seen cracks propagating through the grains of a material rather than follow around the grain boundaries. Perhaps of even more significance is that cracks were forming and propagating extensively through the interior material without leaving any significant trace at the surface, apparently due to the compressive carburization hardening process. This certainly has provoked a degree of controversy among the various groups responsible for the investigation as to what initiated the cracking and the speed and method of propagation. The lack of surface damage limited the possibility of spalling metallic chips being generated and detected by devices intended to identify early signs of damage and potential failure of components.

My interpretation of this mode of crack propagation is that the materials used were operating at the absolute limits of their ability to cope with the stresses involved. Once damage started to occur, progressively greater stress was put on the remaining intact structure. A common enough failure mode, but in this case, the cracks were passing through grain structures that were designed to resist cracks.

I can only conclude that the engineering design of the gearbox exceeded the ability of current materials and manufacturing techniques to cope. Simply beefing up the components a little bit will not be enough. Without even more robust materials, cracks will still form and propagate through the metal. It may take longer for a failure to occur, but it will still happen. We appear to have hit the ultimate limits of material science for the time being.

This catastrophic failure mode is a rare event with only three remarkably similar accidents and a couple of near misses recorded. The problem is that there is no reliable current method of detecting impending failure before it occurs. That suggests that the MGB needs to be totally reengineered or the aircraft operated at a much reduced capacity to provide an extra safety margin.

Either way, I can't see it ever being allowed back into North Sea operations again.

Last edited by G0ULI; 29th Apr 2017 at 01:52.
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