EC225 crash near Bergen, Norway April 2016
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Here are all TBO from the EC225 spec sheet
http://airbushelicoptersinc.com/imag..._data_2009.pdf
Let's go through some dates again (from oep.no)
09.12.2014 Approval of extended TBO
03.12.2015 Approval of extended TBO
so a year between those dates. The extended TBO is 100 hours.
So either inbetween 2014 and 2015 the MGB was changed. Or the AC flew
less than 100 hours.
18.12.2015 Second approval of extended TBO
Then the MGB was changed 17th of January 2016.
The changed MGB had 2300 hours.
Estimating from the 2014 date, could be MGB was changed
around January 2015 and flew 2300 hours until January 2016.
Between the 3rd and the 18th is 15 days.
And the TBO is extended with 100 hours. 100 hours - 15 days
Fits with 2300 hours a year, but is off course just speculation.
But I agree 1300 hours in 3.5 months doesn't sound realistic
http://airbushelicoptersinc.com/imag..._data_2009.pdf
Let's go through some dates again (from oep.no)
09.12.2014 Approval of extended TBO
03.12.2015 Approval of extended TBO
so a year between those dates. The extended TBO is 100 hours.
So either inbetween 2014 and 2015 the MGB was changed. Or the AC flew
less than 100 hours.
18.12.2015 Second approval of extended TBO
Then the MGB was changed 17th of January 2016.
The changed MGB had 2300 hours.
Estimating from the 2014 date, could be MGB was changed
around January 2015 and flew 2300 hours until January 2016.
Between the 3rd and the 18th is 15 days.
And the TBO is extended with 100 hours. 100 hours - 15 days
Fits with 2300 hours a year, but is off course just speculation.
But I agree 1300 hours in 3.5 months doesn't sound realistic
Concentric
This is a Rumour Network.
It is not a place for logical, knowledgeable and pragmatic reasoning!
I enjoyed your first post and is the main reason I continue to look at this website as, sometimes (actually, more often than not to be honest) I learn something different about the industry we are in.
One of the things I have learnt is that companies will say and do anything to 'cover ar5e'.
For purely personal reasons I regard CHC (the company and culture) as a despicable company - and yet all employees I have met have been hard-working and professional.
To employ a PR company to provide a vague polish/spin on such a matter is also despicable and lacks credibility - much like when another company described a crash as a 'water landing'!
I guess what I am trying to say is - the speculation on this site is more credible than anything I have heard uttered from the OEM and Operator thus far. The 'manoeuvring' has been contemptible and no doubt confused/elongated the process.
The 'sludge' theory which was deemed one of the root causees for REDL was addressed by redesign - is someone suggesting that that was a 'red herring/window dressing' or maybe the re-introduction was rushed last time - when the airframes were desperately required?
It is not a place for logical, knowledgeable and pragmatic reasoning!
I enjoyed your first post and is the main reason I continue to look at this website as, sometimes (actually, more often than not to be honest) I learn something different about the industry we are in.
One of the things I have learnt is that companies will say and do anything to 'cover ar5e'.
For purely personal reasons I regard CHC (the company and culture) as a despicable company - and yet all employees I have met have been hard-working and professional.
To employ a PR company to provide a vague polish/spin on such a matter is also despicable and lacks credibility - much like when another company described a crash as a 'water landing'!
I guess what I am trying to say is - the speculation on this site is more credible than anything I have heard uttered from the OEM and Operator thus far. The 'manoeuvring' has been contemptible and no doubt confused/elongated the process.
The 'sludge' theory which was deemed one of the root causees for REDL was addressed by redesign - is someone suggesting that that was a 'red herring/window dressing' or maybe the re-introduction was rushed last time - when the airframes were desperately required?
Turboshafts
The document you have produced there is a seven year old sales brochure.
As the document says it is based on data from 2008.
How about producing the figures from the latest version of the maintenance program.
At least then we can be sure what we are looking at.
The document you have produced there is a seven year old sales brochure.
As the document says it is based on data from 2008.
How about producing the figures from the latest version of the maintenance program.
At least then we can be sure what we are looking at.
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The box could have had 1299 flying hours when fitted, no reason to assume it was a new or zeroed box, simply a serviceable part which was fitted to replace a gearbox which needed to come off. It could easily have come from another machine undergoing some other sort of heavy maintenance.
I'm also confused by the idea that specific authorisation is needed to carry out standard maintenance such as changing a gearbox, to get extensions yes, but I would not expect to see any external requests to comply with routine procedure.
I'm also confused by the idea that specific authorisation is needed to carry out standard maintenance such as changing a gearbox, to get extensions yes, but I would not expect to see any external requests to comply with routine procedure.
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EESDL,
Give a man a break, I’m new here!
Seriously though, and to others who have expressed their appreciation, thanks. I didn’t intend to speculate too much but rather just to look at officially released evidence as an engineer and ask questions that others may hold the answers to, or at least to set some minds thinking. If that comes across as promoting a particular theory then that is incidental but perhaps inevitable.
I make no comment about commercial interests, for they are what they are.
Re- the ‘sludge theory’, don’t you mean G-REDW and the vertical shaft failure? I thought G-REDL was fatigue crack propagation in a 2nd stage planet gear thought to originate from raceway spalling. The only re-design I recall after REDL was removal of the row of magnets and trimming of the oil collector plates.
Re-introduction of the EC225 fleet with daily inspections of the vertical shafts and some lube oil spray mods may not have been an ideal solution but it was pragmatic and no further failures of vertical shafts occurred before they were all replaced with the re-designed ones. Fixing the wiring on the EMLUB warning system was something that could have prevented G-CHCN having to set down on water (just a week after I flew in it, incidentally. Shame, it had nicer seats!).
I should point out that my experience is in general offshore/mechanical/structural engineering not specifically aviation though I have probably spent a couple of thousand hours in the back of the Puma family of helicopters since those wonderful days when the welcome sight of a Puma or ‘Tiger’ on the helideck meant getting home quicker than in an S-61 and ‘enjoying’ music through the ear defenders (invariably some Driller’s choice of Country &Western).
Seriously though, and to others who have expressed their appreciation, thanks. I didn’t intend to speculate too much but rather just to look at officially released evidence as an engineer and ask questions that others may hold the answers to, or at least to set some minds thinking. If that comes across as promoting a particular theory then that is incidental but perhaps inevitable.
I make no comment about commercial interests, for they are what they are.
Re- the ‘sludge theory’, don’t you mean G-REDW and the vertical shaft failure? I thought G-REDL was fatigue crack propagation in a 2nd stage planet gear thought to originate from raceway spalling. The only re-design I recall after REDL was removal of the row of magnets and trimming of the oil collector plates.
Re-introduction of the EC225 fleet with daily inspections of the vertical shafts and some lube oil spray mods may not have been an ideal solution but it was pragmatic and no further failures of vertical shafts occurred before they were all replaced with the re-designed ones. Fixing the wiring on the EMLUB warning system was something that could have prevented G-CHCN having to set down on water (just a week after I flew in it, incidentally. Shame, it had nicer seats!).
I should point out that my experience is in general offshore/mechanical/structural engineering not specifically aviation though I have probably spent a couple of thousand hours in the back of the Puma family of helicopters since those wonderful days when the welcome sight of a Puma or ‘Tiger’ on the helideck meant getting home quicker than in an S-61 and ‘enjoying’ music through the ear defenders (invariably some Driller’s choice of Country &Western).
Last edited by Concentric; 12th Jun 2016 at 20:05.
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If any helicopter I am travelling in accelerates vertically from take-off at a rate of 0 - 100mph in 4 seconds I think I would be having a word with the PF as my 2nd top priority.
I calculated the groundspeeds simply from scaling the distances on the map and dividing by the time elapsed between radar returns. Speed before 09:54:44 approx. 152 mph; speed after 09:54:48 approx. 54 mph. I have no idea how accurate the chart produced by AIBN is but it is a pretty large scale as you can see by the houses.
Last edited by Concentric; 12th Jun 2016 at 20:04.
There seems to be a lack of understanding in relation to normal working practises within the aircraft maintenance environment. Components can be new, overhauled, repaired or
used serviceable. The same applies to sub components within an assembly.
used serviceable. The same applies to sub components within an assembly.
Eric, turboshafts seems to be stuck in some strange "conspiracy theory" surrounding MGB TBOs. Personally I'm bored with his ramblings and will simply ignore his postings from now on.
As an aside -- in the late 80s I had an engine failure with an Arial engine in an Astar due to an internal gear failure. The auto went fine and the seat cushion was eventually removed safely.
The cause of the failure was, as best as I recall, that "it was believed that during the engine assembly the gear had been dropped causing a stress point that later propagated into a crack which led to a gear failure."
The cause of the failure was, as best as I recall, that "it was believed that during the engine assembly the gear had been dropped causing a stress point that later propagated into a crack which led to a gear failure."
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I referred only with CHC and AH info,
mostly as an answer to n305fa.
The arguments against that info is fully equitable.
Thanks
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Turboshaft,
I just don't think anybody knows where you are tryi to go with the TBO thing. You keep talking about the extensions on the MGB that was removed. That gearbox is gone to overhaul, with no incident and is not in question. We got that. Then the 1300 hours since January, which is not possible, but even it was, you have already stated the TBO to be 2000. Meaning the gearbox in question would still be 700 hours shy. It is possible that a gearbox with 1300 hours was installed, as already mentioned, but that gearbox would still no likely make it to 2000 hours in 3.5 months either. I'm sure some of the other guys can pipe in, but I'm use to the average yearly hours on an offshore aircraft being between 1000-1500.
Maybe you need to explain exactly what you are getting at rather then going off about extensions. Extensions are a normal part of the aviation industry.
I just don't think anybody knows where you are tryi to go with the TBO thing. You keep talking about the extensions on the MGB that was removed. That gearbox is gone to overhaul, with no incident and is not in question. We got that. Then the 1300 hours since January, which is not possible, but even it was, you have already stated the TBO to be 2000. Meaning the gearbox in question would still be 700 hours shy. It is possible that a gearbox with 1300 hours was installed, as already mentioned, but that gearbox would still no likely make it to 2000 hours in 3.5 months either. I'm sure some of the other guys can pipe in, but I'm use to the average yearly hours on an offshore aircraft being between 1000-1500.
Maybe you need to explain exactly what you are getting at rather then going off about extensions. Extensions are a normal part of the aviation industry.
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All the Gear's in the Box have an ultimate life.
The TBO on these Gearbox's already have ridiculous low hours as it stands, making this Aircraft a very expensive Aircraft to maintain on a good day.
What I would like to know is just what percentage of the Planet's or Epicyclic's make Ultimate Life, if any?
Does the Gearbox Log Book specify the Actual hours of all the discreet Components or only module's within.
Did the TBO goes down as a precautionary thing, or is around 2,000 all the Epicyclic can handle before it begins to wear?
I can't help thinking a dedicated Bearing for the Planet's instead using the Gear as an outer race would prevent these issue's.
It still freaks me out when I see the Epi Ring form part of the Gearbox Structure.
The TBO on these Gearbox's already have ridiculous low hours as it stands, making this Aircraft a very expensive Aircraft to maintain on a good day.
What I would like to know is just what percentage of the Planet's or Epicyclic's make Ultimate Life, if any?
Does the Gearbox Log Book specify the Actual hours of all the discreet Components or only module's within.
Did the TBO goes down as a precautionary thing, or is around 2,000 all the Epicyclic can handle before it begins to wear?
I can't help thinking a dedicated Bearing for the Planet's instead using the Gear as an outer race would prevent these issue's.
It still freaks me out when I see the Epi Ring form part of the Gearbox Structure.
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However, the gear teeth are not designed for unlimited surface contact fatigue life. Gear tooth surface contact durability is similar to that of rolling element bearings. Surface pitting is the most likely failure mode, which progresses slowly and is easy to detect long before it presents a serious problem. The ability to readily detect surface pitting of gear teeth and bearing surfaces long before it becomes a problem is what allows an on-condition service life approach to be used.
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Turboshafts
The document you have produced there is a seven year old sales brochure.
As the document says it is based on data from 2008.
How about producing the figures from the latest version of the maintenance program.
At least then we can be sure what we are looking at.
The document you have produced there is a seven year old sales brochure.
As the document says it is based on data from 2008.
How about producing the figures from the latest version of the maintenance program.
At least then we can be sure what we are looking at.
@ ericferret :
About MGB and Epi TBO, the last update was done by AH on January and give 2000 FH for both Epi module and main reduction module, with a margin of 200 FH. (If it can remove unnecessary speculation).
Gear Life
Thanks, Riff-Raff. A previous poster cited an " ultimate " life for the gears at 5000 hours. I assume he meant the fatigue life or Component Replacement Time (CRT ). Can one assume that the gears are exposed to accelerated load testing, multiple samples, a three sigma curve reduction etc? Assuming this or a similarly rigorous procedure to support the 5000 hour life is in place, there must be some hard work going on at AH to discover what resulted in two fatigue failures well within the CRT for the part. Unless I missed it, there hasn't been any information at all regarding the failure surface striation count, i.e., how long the crack existed prior to failure. There are a couple of posts on this thread that may/may not point toward a factor affecting the gear loads, but I'd guess that by now, the AH transmission people are way beyond that sort of speculation.
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re concentrics' excellent first post...if one of the rear suspension rods failed it is likely the hull would flare, could this bring the disc into brushing contact with the engine intake screens? The ground pics of the disc show light damage a short distance from the hub on 4 blades, but looking at the blurry shots of the disc floating down, there appear to be similar dings in the blades at the same positions, ie before the disc hits the ground?
Thanks, Riff-Raff. A previous poster cited an " ultimate " life for the gears at 5000 hours. I assume he meant the fatigue life or Component Replacement Time (CRT ). Can one assume that the gears are exposed to accelerated load testing, multiple samples, a three sigma curve reduction etc? Assuming this or a similarly rigorous procedure to support the 5000 hour life is in place, there must be some hard work going on at AH to discover what resulted in two fatigue failures well within the CRT for the part. Unless I missed it, there hasn't been any information at all regarding the failure surface striation count, i.e., how long the crack existed prior to failure. There are a couple of posts on this thread that may/may not point toward a factor affecting the gear loads, but I'd guess that by now, the AH transmission people are way beyond that sort of speculation.
Don't know about the published CRT as others are posting about, but we can assume that the fatigue approach is NOT as you say for gears. It is close, however. The standards have not changed much in this area, in general it is a 140% overtorque test that is conducted in a rig. This equates to just under 3 sigma for steel. The load can be reduced further for multiple specimens. It is intended for tooth bending loads. Not sure what was done on this box, how much credit if any was taken for legacy assemblies. Nor do we know what other loads are considered. In the pinion, the cracks shown are not tooth bending, but initiate at the bearing integral race (our guess based on the released photos).
I concur that AH engineers are scrambling, regardless of what the press releases are saying.. in addition to experts from their transmission source, as I understand that it is completely outsourced, including design.
On the loads, Also agree as you suggest that there may be an anomaly, a previously not understood load source affecting the epicyclic, beyond that which it was certified to.
Gears
OneP: Thanks for the correction re gear qual as opposed to main shaft, push rods, servo loads and the like.
It reads like you are well educated re gearbox qual. Admitting to be too lazy to go back and see who posted it, but there was some chat re how those three rollers came to be missing. Is that a realistic possible result of the wrenching forces at work during the initial event? If not, would a gear eccentricity under load produce 1P eccentric loads ( Gear 1P, not main rotor 1P ) which could be a factor to weigh? Sounds pretty far out, perhaps.
It reads like you are well educated re gearbox qual. Admitting to be too lazy to go back and see who posted it, but there was some chat re how those three rollers came to be missing. Is that a realistic possible result of the wrenching forces at work during the initial event? If not, would a gear eccentricity under load produce 1P eccentric loads ( Gear 1P, not main rotor 1P ) which could be a factor to weigh? Sounds pretty far out, perhaps.
John D,
There is a previous post that points out that the gear can be just tilted and the rollers are then only retained by the separator cage.
There is not a huge difference in the MGB design basics throughout the whole
family right back to the Alouette as you would expect, just bigger.
I have worked with an overhaul guy on AS350 MGB's and he used to pop the
bearing rollers out when we changed a bevel module for a quick look at the inner race.
AS 350 shown below - pretty much the same.
There is a previous post that points out that the gear can be just tilted and the rollers are then only retained by the separator cage.
There is not a huge difference in the MGB design basics throughout the whole
family right back to the Alouette as you would expect, just bigger.
I have worked with an overhaul guy on AS350 MGB's and he used to pop the
bearing rollers out when we changed a bevel module for a quick look at the inner race.
AS 350 shown below - pretty much the same.
Thanks John,
Seems to me the roller is probably secondary - The carrier deformation indicates that tremendous inertial forces were in play which could cause pinion deformation and roller ejection. but it could have gone either way. Early, we postulated that the pinion fractures could be the same reason, but the evidence of fatigue tells us otherwise. You are probably on to something about eccentricity. What is strange about this arrangement is the spherical bearings. They allow the pinion to float, but if the alignment of the sun to ring is held, then why need it. The first stage sun gear wear makes it look like a crown gear, but an ugly crown. It some point prior to SHTF, this gear was not aligned correctly with all of the pinions. It could be that a pinion was tilted so we can't say what one was 'wrong'. That goes back to the roller/ raceway..
Something tells me that, in absence of HUMS record, an acoustic analysis of the CVDR would indicate a rising background noise corresponding to epicyclic origins. AIBN does not have to tell us that yet now do they.
Seems to me the roller is probably secondary - The carrier deformation indicates that tremendous inertial forces were in play which could cause pinion deformation and roller ejection. but it could have gone either way. Early, we postulated that the pinion fractures could be the same reason, but the evidence of fatigue tells us otherwise. You are probably on to something about eccentricity. What is strange about this arrangement is the spherical bearings. They allow the pinion to float, but if the alignment of the sun to ring is held, then why need it. The first stage sun gear wear makes it look like a crown gear, but an ugly crown. It some point prior to SHTF, this gear was not aligned correctly with all of the pinions. It could be that a pinion was tilted so we can't say what one was 'wrong'. That goes back to the roller/ raceway..
Something tells me that, in absence of HUMS record, an acoustic analysis of the CVDR would indicate a rising background noise corresponding to epicyclic origins. AIBN does not have to tell us that yet now do they.
