@Aussierob: Redundancy (technical mechanics), resonance (harmonic oscillations, interferences, stimulations of vibrations), realiability (bolts, washers & nappy pins), please see my comments before. E.g. http://www.pprune.org/9372108-post612.html
or what do you think about the 3-leg-theory and its redundancy? As well as a 4-rotorblade-system should have 4 suspension bars and a 5-rotorblade-system should have 5 suspension bars and those should be symmetrical? Ask some pilots which are also engineers.

Buzz66:
Simple physics?!..Buzz, you made me laugh a little today..thanks.

Let's face it...Airbus knows exactly what happened. They've known all along... and by now they've backed up their theory with real physics. (finite element analysis)

The AIBN will need to address the root cause soon..and it's tough.. this catastrophe was caused by a "maintenance event(s)".

You seem awfully sure that anything AH is saying is true. Personally I don't trust anything that comes from commercial sources, they always have an agenda other than the truth. Unless I've missed something, they haven't backed up anything, they've just made their claim more clear. They haven't described the other 6 "possible scenarios" and why they were so unlikely. I think it's very hard to have any confidence in claims without any description of the thought process behind it.

The last time I checked AIBN doesn't have to come up with anything - they will take the time needed to figure it out and then present the final report. That's the beauty of (commercially) independent bodies/entities.

If suspension bar fails, for whatever reason, and the head flaps dramatically, this would put huge strain on the conical housing. If the conical housing ruptures, and in this case it has, the mast splined end in the upper stage epicyclic would impact a huge lateral bending loads on the planet carrier which in turn would compress the gear train and put huge lateral loads on the ring gear in the moments before catastrophic failure of the whole assembly.

There are many ways to de-construct the scenario. I think we should keep an open mind.

Nadar>> You wouldn't trust the RFM (Flight Manual) that is issued by Airbus Helicopter?
More Generally, you don't trust cars, planes, restaurants, soap, toothpaste??

Nadar>>But then you go on to say that they have to present the final report.. So which is it??

The finger of blame
 

What I find distressing about all crash threads is the almost desperate attempts of some contributors to apportion blame. In this case the person/people who posted "blaa blaa 'firewall' blaa blaa 'hangar floor'" etc. That specific post has been removed or taken down which is good, but there has been a common theme since that post which I find depressing at best.

Airbus have followed a similar nudge wink marketing/mitigation line since about day two. They couldn't possibly have 'known all along' what was the cause of this accident or there wouldn't be three or four possible causes now. All we can say for sure is that something above the cabin roof detatched from where it should normally be or broke and the aircraft fell to earth.

I would like to know what happened in this case. I am sure the families of those involved are desperate to find it out.

However, it is important to realise who in this or any crash has a vested interest in a particular outcome. The operators have an interest. One operator would like it to be the fault of the manufacturer and all the others would like it to be a maintenance error. The manufacturer also want a maintenance error to be found as the cause.

I have heard it said that the AIBN are biased. I don't believe this and were it true would the CAA or AAIB or BEA or any other party involved let that pass? Absolutely not.

So, the only unbiased view will be that of the investigation board.

With this in mind, some posters should have a little sensitivity towards the people directly involved, the engineers specifically. Fine to hypothesize, just as long as what you are saying doesn't point the all to easy to point finger at one or two individuals. It is wrong to do so and those doing it either lack the intelligence to realise it or are deeply unpleasant. That is me pointing the finger at you, you know who you are! :=

Folks,

It always makes me smile when people say we should wait for the final report. Why? it is perfectly reasonable to discuss what happened. What we should do is avoid wild speculation and recognise that the various parties are subject to constraints we are not. Please also remember that the people at AH, CHC, AAIB etc. are professionals and while they have slightly different agendas in my opinion and experience are certainly not dishonest.

I think the reason AH have started to push what they see as the probable cause is that the 225 programme won't survive another 9 month suspension. This is nothing to do with the cause of the accident (although they clearly believe that is associated with the failure of the transmission shaft suspension). It is to do with the fact that NS is in decline, the oil price is low, the helicopter business is surviving on military orders, the operators are in financial distress and machines are being returned to lessors at an unprecedented rate. Lessors may see this as an oppopportunity to restructure their civil heicopter portfolios while their fixed wing business is boyant.

Thus the Pumas may end up effectively withdrawn well before the AIBN issues its final report and whatever that concludes.

Well said Hompy, I agree wholeheartedly.

Birmingham, I think the emphasis here is on the word "conclude". Hypothesizing and discussing is in my opinion fair game at this point, but to conclude and point fingers is not.

As the investigators initally responded to the press about AH statements: "There are still many doors open, we will close them one by one."

Airbus Helicopters issued a statement after a relatively brief examination of only the partially recovered wreckage to the effect that their product was not at fault. The Norwegian air accident investigation team have since recovered more wreckage and have had the opportunity to examine it in detail, yet they have made no comment as to the precise cause.

In order to be able to make such a statement Airbus Helicopters either had immediate access to information that is not in the public domain, or, that this was a known problem that they knew could happen but on the balance of probabilities they thought unlikely.

From the victim's (and their families) point of view, it is immaterial if the gearbox split and severed a suspension bar or the suspension bar failed causing the gearbox to rupture. The end result was the main rotor separating from the aircraft and that is an unacceptable design flaw in any rotor craft.

It is immaterial if analysis shows that such failures can be expected only once in 100 million hours of operating. It has happened on at least three occasions in helicopters of similar design to date. The problem with probability is that supposedly rare events can happen in close clusters and when that happens the psychological impact is such as to overcome the rational thought process. People are disinclined to trust their life to such a machine, even though it can be demonstrated that such failures are extremely unlikely.

NASA had an enviable safety record when allowed a virtually unlimited budget, but engineering compromises and cost cutting measures eventually resulted in the loss of two space shuttles. Have commercial pressures reduced Airbus Helicopters to a similar situation where a known design weakness has been ignored because it was cheaper to budget/insure against a crash or two rather than fix the root cause?

Back in the day, the 332L suspension bars were lifed, inspected every 750 hrs and X-Rayed every 12 yrs. I do not understand why there are, apparently, two failures of a bar leaving a centre portion missing. If the bar failed at the top, the bottom part would, presumably, remain with the fuselage. If it failed at the bottom the upper part would stay with the MRH. I do not know how the bars are constructed, can someone advise on this?
It is possible the the Main Rotor Shaft damaged the MGB parts when the MRH and blades departed.

Quote:

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Oldlae: I do not know how the bars are constructed, can someone advise on this?

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Have’nt you seen all those fotos, pictures and graphics of suspension bars, MRGB and MR-Head uploaded in present thread? (https://www.yumpu.com/xx/document/vi...nsion-bar-h225)

Wow Buddy you sound really terrified.
It was my never my intent to distress you or any Punters on this forum.
This is not my first time to display the blunt facts as I see them.
I know it comes home hard with some people. I feel your pain Buddy it's ok to let go!

The more things go off track the louder I get.
Some people want me louder others not.

Yes I agree. That is the Big Picture
Well Said!

AW009
Thanks, I missed that reference.

Airbus = Mast stress causing Conical housing to rupture as a result of Sus Bar or Foot Fail

So the vertical force on the Barby Plate can withstand more force in a variable angle to the TQ in which it's design was intended enough to shatter the Conical housing.

Good luck selling that


Like to see the sales pitch on that Bad Boy!

Some have said, on here, that the Puma family has run up 9 million hours over all marks.
In that time it has had 3 visualy similar (tho not causal) MRH failures where we can ALL graphically imagine the results.

My questions are;

1 At what point does the statistical likelyhood of this event occuring 3 times stop being chance and become an inherant weakness ?- for whatever reason.

2 Does any other type (same operating area/same hours) have similar record of such a failure?

We should remember that as far as the "public" is concerned an aircraft loss is an aircraft loss - "most" people will neither know nor care whether it was caused by human error or mechanical failure. They will simply have the preception that a newer (or different) aircraft is safer simply because they,ve crashed less !

I think it unfair that on aircraft types that this is the case - but, how long did the chinook family survive public opinion?

On a personal note - ever since I saw the picture of the MRH buried in the ground with an intact strut minus its lower attachment pin, I,ve had a bad feeling.
AAIB and AH will have the final say.

Quote:

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Letmein: … this catastrophe was caused by a "maintenance event(s)".

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Maintenance events are not only a question of human error, but also of functional and fail-safe design. And up to now there are’nt any evidences given for maintenance events, although this might be welcome by AH.

Holy Crap really...You should quit while no-one still knows who the hell you are.

Where to start..

9 Mill flights hours has mostly be carried out by the good old L & L1's thank you very much!!!!!!!!!!!!!!!!! Both Model's are still flying right now.
So you clearly don't work for Airbus or you would already know that.

1. Because the bloody Jesus bolts all came from the same cause. the gearbox failed...It doesn't matter what caused it every time the fact remains, the end result NOT well received.
2, Ohh dear refer above

I simply cannot believe you actually put this in in print to anyone...Fark me do you deserve everything about to come your way, Hang on for the ride!!!!

We should remember that as far as the "public" is concerned an aircraft loss is an aircraft loss - "most" people will neither know nor care whether it was caused by human error or mechanical failure. They will simply have the preception that a newer (or different) aircraft is safer simply because they,ve crashed less !

Perhaps it's not so much to apportion blame, but to understand a cause. Understand the cause to reduce the chance it could reoccur, particularly as a result of a factor introduced by the person speculating. This is a personal growth/learning exercise.

Personally, other than for grossly malicious action, I have no desire to point at a fellow aviation person, and say "you did it!, you're in trouble". I wish much more to do my part to understand and prevent unsafe situations. In this case, I have considered factors which may be involved here, and that will make me a more safe aircraft maintainer in the future. Had speculation not occurred in this forum, I would not have those better ideas, which will now stay with me to make my aircraft more safe. That is irrespective of the outcome eventually found.

Several times I have maintenance check flown an aircraft and found a maintenance failing - which was the purpose of the flight! I've not returned and waved an ugly finger at the maintainer and said "look what you did!!!", It's been I have found this, and it needs to be corrected before I'll sign for the aircraft, can we work this out, and I'll take for a flight afterword.

Sensitivity to families and our peers is great here, and empathy for someone somewhere who might have a big lump in their throat right now, because they do understand the cause . But, I like the discussion, and am learning from it.

Hey Buzz,

The last time I checked we were allowed our own opinion.

There are 371000 views on this post.
That represents about 0.000053% of the worlds population.
Hence the comment "most people"
Even allowing for interest drift.

The Public (you and I) DO NOT KNOW WHAT CAUSED THIS ACCIDENT
Do you? For sure, and in court defendable?
Well, we,re waiting.
No, I didn,t think so.

My question 2 was genuine.
Does any other type have any history of MRH detaching?
I know of one....you?
Let us all know.

I apologise if I have offended.
Best I hide before "anyone finds out who I am"