Actually this is the crux of the matter;

So there is one type that has done this. And it's manufacturers response has been to squirm and dissemble.

How does it compare? Well I have a technical interest because this newer 'safer' generation of helicopters seems to be anything but that.

One seems to have issues, some possible caused by marketing hype and the rest by measures which need to be sorted out (4.5 hrs warning and no actions????) and one has what appears to be a fundamental problem which it's manufacturers just want to 'go away'.

Conclusion came before they even find evident is what makes this investigation fishy from the beginning. Claiming MGB failure subsequently teared off the suspension bar which also proved to be false by simulation.

Epicyclic 2nd stage gear found!
https://www.aibn.no/About-us/News-ar...overy-of-parts

https://www.aibn.no/Aviation/Investi...1177_&attach=1

Amazing work to locate that. Whether it will be of much use in the analysis aft that long time in the sea will be interesting. Where are all the planet gears? Fired out radially in all directions along the path of destruction?

Progress!
 

I have with great interest followed this accident thread.
Can any of you with experience please comment on how this important finding might help solve or prove the likely cause of the failiure .
I have to say I am very happy to see the Norwegian Navy finding this important part.
Respectfully
Cpt B

How did the planetary support ring get bent; especially where two spigots seem to have lost there bearings before it went into the sea.

Pretty straightforward really, FED, one or more chunks from the failed gear get carried forwards by the faster rotating sun gear and get entrained between the sun and those next 2 planet gears. With nowhere else to go it pushes the 'spigots' (or carrier pins) outwards causing the carrier to bend and the ring gear to burst.

It appears to have happened quicker and with a lot more energy than REDL where 7 planets and the inner race from the 8th stayed with the carrier.

It is not clear from the other photo (Close-up of the inner race from the failed planet gear) posted by AIBN whether it is showing the loaded arc or the reverse side of the inner race. Once cleaned up, if there is no evidence of pitting it would suggest little or no spalling of the outer race prior to fracture.

I muss say I am very impressed by the recovery of this admittedly very important piece of evidence so long after the fact.

I'm surprised it took 10 days to release the information that it was found. Love to see the details of how they found it. I had thought the search was long over or at least over. Was Airbus supporting the continued effort to find the parts or was it all AIBN? Makes you wonder if they can find this how hard could it be to find MH370. I guess a lot harder.

HC
I think we are having parallel arguments, rather than totally disagreeing with each other.

We both agree, that we wouldn't like to fly (in) a machine that has a known fault. A fault that can't be mitigated or compensated for.

Personally, after what has been claimed by AH up to now, I'm disinclined to believe anything they say, especially in regards a "fix". Apparently within 24hrs of the Norwegian tragedy, there was "no problem" that wasn't "caused by maintenance issues". Disgraceful.

Once the problem has been fixed, and scrutinized by an independent authority, Ill happily fly the Super Doopa Puma again.

The EADS requirement to only fly with the non occurrence type of planetary must have provided a large number of components that can be analysed. What we have here is a specific failure mode not yet fully understood. We still have no idea whether this is a design issue, some type of manufacturing problem or a couple of one off unique occurrences such as the truck accident story. And that's the problem - we can't restore confidence until we know definitively why this happened. Premature statements from the manufacturer and some unfortunate PR hasn't helped. If it turns out the design itself is safe the public will require an explanation they can understand clear and simple. Hopefully the recent discovery of additional parts will help this happen.

Actually, that is the planet carrier. There are no planet gears present, but there is a single planet gear inner bearing race still attached at the 3 o'clock position. You can also see what remains of one of the tabs used to retain the planet gear inner bearing races at the 2 o'clock position. Took a significant amount of axial force to tear all those planet gears off the carrier pins.

riff,

One might assume it took a similar magnitude of axial force to break 4 tabs on REDL as you can see in the photo below (Source AAIB Report 2-2011) but it is interesting that its gears stayed on and there seems to have been a limit to the axial displacement of the inner races – possibly contact with the 1st stage carrier?

Of course, the axial force component on LN-OJF may well have been much, much larger than that needed to just break these tabs.

I think the major difference was in whether the larger gear fragments went outwards between planet cluster and ring gear (G-REDL) or inwards between the cluster and the sun gear (LN-OJF). All consequential to the root cause – fatigue failure of a planet gear.

HC, as you predicted the next fatal incident was indeed an s92 sadly killing an Irish Coastguard crew who were only there to rescue others. At this very early stage no information is available as to what was the cause. I am sure that unless evidence of technical failure is found the S92s will keep flying. If it transpires there was a technical reason and a grounding of S92s as well as 225s is necessary it will be seriously testing for the oil and gas people. For everyone's sake let's hope they can establish the facts quickly. Another sad reminder, if it were needed, of how dangerous helicopter ops can still be.

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.

Whatever the details, in the last few weeks the principle that if a type does all the work then it has all the accidents seems to be settled.

SA less, one advice, do not stay at the bar before posting...

Ok, what am I missing here?
(March 17th 2017)

When I look at the document: https://assets.publishing.service.go..._Header_V1.pdf

The latest comments I see are still from 2015.

an update from the AIBN is due later this month I believe

Confirmed for this Friday:

https://www.aibn.no/About-us/News-ar...iminary-report