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EC 225 latest ......so quiet

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EC 225 latest ......so quiet

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Old 11th Oct 2016, 17:57
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And now a full commercial and governmental response. Airbus criticises Poland for cancelling helicopter deal - BBC News
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Old 11th Oct 2016, 21:40
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They would say that, wouldn't they? It's their ox being gored.
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Old 12th Oct 2016, 00:25
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Poland have gone with Black Hawks , which are already built in Poland anyway!! Better assault Helo anyway.
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Old 12th Oct 2016, 05:37
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Originally Posted by industry insider View Post
This is no more than basically putting AS332L1 Type gears into all epicyclic modules because they are "known" to be reliable and monitoring them by checking chip detectors and filters every 10 hours.
With respect, I think this is at best misleading. An L1 2nd stage planet gear is smaller than an H225 one (L1 has 9 planets; H225 has 8) so they cannot be interchangeable in the same epi module. The L1 epi would not have the torque capacity for an H225.
It might be there will be some shared characteristic (e.g. bearing vendor or material) between L1 and Type B H225 planet gears but they are not the same item.
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Old 12th Oct 2016, 05:57
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Originally Posted by birmingham View Post
"There are two configurations of planet gear within the current type design. In depth review of the design and service data showed that one configuration has higher operating stress levels that result in more frequent events of spalling, associated with rolling contact fatigue, while the other exhibits better reliability behaviour. By limiting the type design to the gear configuration with lower stress levels and better reliability and specifying a reduced life limit, combined with more effective oil debris monitoring procedures and other operational controls, an acceptable level of safety can be restored."

Redesigning an epicyclic is hardly a trivial exercise and there must have been a very good reason to do so. I don't know the engineering history of this does anyone know if it was in response to earlier failures or simply to increase time between inspections or allow higher loadings?

Also were all the previous MGB accidents (excluding the bevel gear systems) involving type A?
It was mentioned on the crash thread that planet gear types A and B have both been used since introduction of the AS332L2 and subsequently EC225/H225 but are manufactured by different bearing manufacturers. This might simply be for commercial reasons to ensure competitive pricing and security of supply. It has not actually been publicly stated if both crashes involved type A, possibly for legal reasons, but we seem to be steered to that assumption otherwise the change to type B would be foolhardy.


Excluding the bevel gear failures "all" the MGB accidents amount to 2 (the SA330 having a different gearbox). If types A and B are indeed made by different bearing manufacturers then careful perusal of published information confirms both failures were Type A.

Last edited by Concentric; 12th Oct 2016 at 08:35. Reason: Everything becomes clear after a cigarette.
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Old 12th Oct 2016, 14:45
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Originally Posted by industry insider View Post
Concentric

There are 2 types of gear with different part numbers -06 and -07. Each gear has bearings from a different manufacturer. -07 gear bearings have a different span and shape and a corresponding greater contact pressure on the outer race (inner rig of the gear) than -06 gear bearings.

It is thought that the greater contact pressure of the bearing in the -07 gear causes spalling. The -06 gear bearing is not known to suffer spalling according to AH.

Any metal on the plugs or in filter at the 10 hour inspection must be analysed. Any presence 16NCD-13 metal would indicate spalling of the -06 gear bearing. The -06 gear / bearing / cage combination has been in the L and L1 for some time and are regarded as the reliability benchmark.
Industry Insider, a technical question:
In AAIB report on G-REDL, page 17, it is written that second stage on AS332L2 increased the dimension of planet gears and reduced their number from 9 to 8. So, it is really possible to install a -06 gear and its bearing in the L and L1 and their carrier?
Besides, is 16NCD13 steel the material of the planet gear only? Maybe other power gears, apart the bevel shaft of 2012 memory (in steel 32CDV13), are made from the same material.

Last edited by dascanio; 12th Oct 2016 at 14:58.
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Old 12th Oct 2016, 15:17
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Originally Posted by industry insider View Post
Concentric

There are 2 types of gear with different part numbers -06 and -07. Each gear has bearings from a different manufacturer. -07 gear bearings have a different span and shape and a corresponding greater contact pressure on the outer race (inner rig of the gear) than -06 gear bearings.

It is thought that the greater contact pressure of the bearing in the -07 gear causes spalling. The -06 gear bearing is not known to suffer spalling according to AH.

Any metal on the plugs or in filter at the 10 hour inspection must be analysed. Any presence 16NCD-13 metal would indicate spalling of the -06 gear bearing. The -06 gear / bearing / cage combination has been in the L and L1 for some time and are regarded as the reliability benchmark.
Thanks for that info. On reading EASB 63A030 it looks like there are more than just 2 part numbers, in fact -00, -02, -03, -04, -05, -06, -07. Of these the ones I marked in bold appear to require replacement. So what you say appears to be a subset of this. The total number of type-07's listed is 2972 (over 370 gearboxes).

From the AAIB report 2/2011:

"The design of the AS332 L2 MGB was based on the design of the L1 model, and used essentially the same main module as the L1. In order to maximise the benefits of the increased engine power between the L1 and L2, changes were made to the epicyclic gearbox module. These included increasing the size of the second stage epicyclic planet gears and reducing their number from nine, in the L1, to eight. These changes not only took account of the increased power to be transmitted, but were also aimed at reducing the probability of spalling".

So the AS332L1 planet gears are not the same as H225 type B gears (or type -06 if you like)?

Last edited by Concentric; 12th Oct 2016 at 15:28.
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Old 12th Oct 2016, 16:36
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Originally Posted by industry insider View Post
So reading the above from EASB 63A030 if the 06 ones don't require replacement in the 225 gearbox, they must therefore be fitted?
The listed -06 parts total 3597 (approx. 450 gearboxes worth) so just over half of the total combined -06's and -07's. That is not to say how many are actually presently fitted given that some may have previously passed discard criteria and some may be in stock as spares.
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Old 12th Oct 2016, 17:26
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Originally Posted by Concentric View Post
It was mentioned on the crash thread that planet gear types A and B have both been used since introduction of the AS332L2 and subsequently EC225/H225 but are manufactured by different bearing manufacturers. This might simply be for commercial reasons to ensure competitive pricing and security of supply. It has not actually been publicly stated if both crashes involved type A, possibly for legal reasons, but we seem to be steered to that assumption otherwise the change to type B would be foolhardy.


Excluding the bevel gear failures "all" the MGB accidents amount to 2 (the SA330 having a different gearbox). If types A and B are indeed made by different bearing manufacturers then careful perusal of published information confirms both failures were Type A.
Thanks very helpful insight - Despite their admission that the cause is not fully understood the advice is clear - change to type B and up inspections. It is safe to assume that a very thorough evaluation of the service history of the two units has been undertaken and, as you point out, the failures have occurred only in type A. In addition maintenance records must also point to spalling/chip detection data suggesting that type A has proven less durable than type B. If not the advice to go flying is either very brave or very foolhardy. One can therefore assume that the AIBN and AAIB are continuing to examine this theory and obtain more concrete evidence that the problems in A definitely do not exist in B. Proving it happened in A is a very different thing to saying it cannot happen in B hence the extreme caution - the safety and legal consequences of such a statement make it a very high stakes game.

Last edited by birmingham; 12th Oct 2016 at 17:41.
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Old 12th Oct 2016, 17:32
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A word on probabilities...

This hopefully will be obvious to most people but I think worth mentioning anyway.

In the absence of ‘particular engineered differences’ between the 2 planet gear types, statistically the probability of a failed planet gear belonging to one type or the other is proportional to the number of that type in service as a % of the total.

With roughly equal numbers of 2 types, A & B, in service the recurrence of failure in 2 Type A’s might seem (at first) to point to some sort of particular susceptibility or trend. However this is misleading, for the actual random probability of ‘both gears being of the same type’ remains 50-50 since AA and BB both satisfy that definition. The other side of the coin would have been AB or BA.

It is easy when searching for ‘an answer’ rather than seeking the truth, to accept ‘evidence’ that fits a theory without challenging it objectively.

There now does appear to be some stated ‘particular engineered differences’ between the 2 types but there also appears to remain this lack of understanding as to the cause(s) of these 2 gear failures.
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Old 12th Oct 2016, 17:47
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Originally Posted by Concentric View Post
A word on probabilities...

This hopefully will be obvious to most people but I think worth mentioning anyway.

In the absence of ‘particular engineered differences’ between the 2 planet gear types, statistically the probability of a failed planet gear belonging to one type or the other is proportional to the number of that type in service as a % of the total.

With roughly equal numbers of 2 types, A & B, in service the recurrence of failure in 2 Type A’s might seem (at first) to point to some sort of particular susceptibility or trend. However this is misleading, for the actual random probability of ‘both gears being of the same type’ remains 50-50 since AA and BB both satisfy that definition. The other side of the coin would have been AB or BA.

It is easy when searching for ‘an answer’ rather than seeking the truth, to accept ‘evidence’ that fits a theory without challenging it objectively.

There now does appear to be some stated ‘particular engineered differences’ between the 2 types but there also appears to remain this lack of understanding as to the cause(s) of these 2 gear failures.
Absolutely - also given the very small number of occurrences the results would not be particularly significant, hence a scientific understanding of why the gear in this accident (and the previous one) failed is essential to restoring confidence.
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Old 21st Oct 2016, 05:49
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With the EASA lifting the temporary flight restriction, which regions/companies are using the 225 again?
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Old 21st Oct 2016, 06:41
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Have ben told that the following countries are back on the 225 bandwagon.
China, Vietnam, Brazil, Angola, USA, in commercial transport operations.
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Old 21st Oct 2016, 10:58
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Brazil is only the military flying there 725´s , no commercial 225´s operating yet
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Old 22nd Oct 2016, 10:49
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The biggest question remains 'will UK and Norwegian CAAs or offshore customers be satisfied that the Airbus Helicopters 'fix' is sufficient to get back onboard a 225'...I think it will take more than a clearance to fly from EASA.
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Old 22nd Oct 2016, 12:03
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Although I am not very knowledgeable, I would yet question/highlight that EASA is supposelly to take over all sovereign power within the easa members concerning aviation authorities by 2017, thats at least what i was being told about the french DGAC (french CAA counterpart) or maybe am I wrong?
If so that would imply some serious troubles me think in particular keeping in mind brexit...

Last edited by singesavant; 22nd Oct 2016 at 17:15.
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Old 26th Oct 2016, 10:50
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I heard Total are pushing (or being pushed?) to use the 225 again once an appropriate tender comes out. Fundamentally this has been a technical problem with an understandable emotional response. Take away the technical problem and there is no reason for the ac not to come back once the fix has been explained to the workforce and demonstrated to be compliant and safe.

The NS it's done but in other markets it'll be a case by case phased re-introduction. Let's not forget that when the final engineering solution is in place, the 225 is still capable of taking more people further for less money than the alternative. The economics will always win out with some customers, particularly in places with less powerful unions and gutter press screaming every time a warning light comes on.

This is in no way an exoneration of EASA seemingly bowing to pressure from Airbus to let it fly again when no definitive word has been sent by the investigation.

Helicopter operators are gleefully taking all the idle S92s at the moment forgetting that the S92 had major engineering issues when it came in. Those loading up on S92 will find the rug pulled when the 225 comes back online as it cannot compete on price in those places where price is the only thing that matters.

My 5c worth.
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Old 26th Oct 2016, 12:15
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The appeal of the aircraft is that it 'carries more people further', missions which imply maximum demands on the gearbox.
But the technical problems that have produced two catastrophic crashes have not been identified, much less fixed.
The confidence of the workers that the aircraft is safe is not enhanced when the EASA releases the aircraft even before the investigation has wrapped up.
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Old 26th Oct 2016, 12:23
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582 jobs to go at Airbus Helicopters due to the downturn in oil related activity and loss of the Polish contract.

Airbus Helicopters annonce un plan de 582 départs | La Provence
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Old 26th Oct 2016, 14:32
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II, I hate the 225, overwhelmingly a design that is trying to be the constantly evolving French helicopter version of the Porsche 911, without German engineering. But I'm in the industry so I have to be objective and you've taken certain sentences out of context and deliberately ignored my caveats. Let me set you straight.

One the first point you dislike, I noted that EASA have jumped the investigation. I dislike that immensely as well. Maybe my 3rd para was too far down the page for you to read?

The S92 vs 225 argument on commercials is centered around the payload at distance and cost per seat argument, most often used in production. There is almost nothing in the PBH rates, the S92 burns more fuel but a full 225 can go further than a full S92. If you want to go more than 135nm then it's cheaper/ person in a 225. A 225 full goes out to 170nm. And the 225 in OGP fit was a bit cheaper than an S92 in similar.

As for the grounding, your point is valid I agree. But different regulators have different interpretations of issues concerning design faults. It would have been interesting to see EASA's response to the S92 issues and FAA to the 225.

On the final point of costs of heavies, as I noted, if helicopter operators have to price them as super mediums to get customers to contract them, you're not looking at like for like vs the S92. Balance will be altered in markets which allow the 225 back. Do you really think that a safe 225 capability for the price of a SM will be ignored in Angola or other jurisdictions of that ilk? I think you are too North Sea focused in your thought process. I doubt that helicopter operators are sat at home with hundreds of millions of dollars worth of ac sat idle and saying, "ah well I guess we'll just go bankrupt because this conversation is a bit hard"... They'll be back, the industry will just re-balance again.
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