EC 225 latest ......so quiet
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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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"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?
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?
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 07:35. Reason: Everything becomes clear after a cigarette.
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.
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.
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 13:58.
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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.
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.
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 14:28.
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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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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.
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 birmingham; 12th Oct 2016 at 16:41.
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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 As 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.
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 As 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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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.
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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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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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...
If so that would imply some serious troubles me think in particular keeping in mind brexit...
Last edited by singesavant; 22nd Oct 2016 at 16:15.
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.
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.
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.
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.
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
Airbus Helicopters annonce un plan de 582 départs | La Provence
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.
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.