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EC225 crash near Bergen, Norway April 2016

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EC225 crash near Bergen, Norway April 2016

Old 1st Jun 2016, 19:19
  #1041 (permalink)  
 
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Nail in coffin...
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Old 1st Jun 2016, 19:33
  #1042 (permalink)  
 
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G-REDL

An extensive and complex investigation revealed that the failure of the MGB initiated in one of the eight second stage planet gears in the epicyclic module. The planet gear had fractured as a result of a fatigue crack, the precise origin of which could not be determined. However, analysis indicated that this is likely to have occurred in the loaded area of the planet gear bearing outer race.


LN-OJF

Among the recovered parts were two pieces which together form approximately half a second stage planet gear (ref. Figure 2). Examinations of these parts have revealed features strongly consistent with fatigue. The fatigue appears to have its origin in the outer race of the bearing (inside of the gear), propagating towards the web of the gear teeth. There is sign of spalling in front of the fracture surface.
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Old 1st Jun 2016, 19:42
  #1043 (permalink)  
 
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Airbus respond with an EASB that is H225 specific, what about other variants?

Obviously still trying to promote the suspension bar theory...
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Old 1st Jun 2016, 19:44
  #1044 (permalink)  
 
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Everybody still happy with their choice of toothpaste?
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Old 1st Jun 2016, 20:11
  #1045 (permalink)  
 
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Originally Posted by helicrazi View Post
Airbus respond with an EASB that is H225 specific, what about other variants?

Obviously still trying to promote the suspension bar theory...
That was not a response to the findings announced by the AIBN this afternoon. The EASB was announced yesterday and issued today.
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Old 1st Jun 2016, 20:13
  #1046 (permalink)  
 
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I used the word 'respond' as tongue in cheek, however it was spectacularly timed!
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Old 1st Jun 2016, 20:34
  #1047 (permalink)  
 
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Updated report from AAIB/N issued today: "Recent metallurgical findings have revealed features strongly consistent with fatigue in the outer race
of a second stage planet gear in the epicyclic module of the MGB
. "

http://www.aibn.no/Luftfart/Undersok...-File&attach=1

EDIT: Sorry... did not see that there was already a post that referenced this updated report. Rookie mistake.

Last edited by SpotOn_No; 1st Jun 2016 at 22:04.
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Old 1st Jun 2016, 20:50
  #1048 (permalink)  
 
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Okay, not good news here at all, but not surprising based on earlier photos we saw.


Next hard part is to determine "Why". Parts break when strength is exceeded by load. designers keep that from happening in theory, supported by testing. But if something breaks, you look at both ends of that basic equation. Was the part weaker than designed or are the loads higher than expected. If the former, due to quality issue, that can usually be contained. If the latter, then heads scratch on entire substantiation, heavy inspections, life limits, etc.
Also note (as stated earlier) the symmetry in fractures - and the number of parts affected. Less likely a quality issue, when affects multiple parts, unless same batch. There may well be a vibratory deflection content that was not anticipated, thus not deigned for. The issue that doomed Norne event was a resonance that AH discounted. They probably are paying attention now...
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Old 1st Jun 2016, 21:15
  #1049 (permalink)  
 
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Article from a Norwegian website an hour ago, where the Technical Director of the Norwegian Aviation Authority says that they are "strongly considering" to ground even the SAR 225s (which have been flying after the accident). He also says they are waiting for a reply from EASA, and the article says that this could end in a global grounding of the Super Puma fleet.

Brudd på giret avdekket i ulykkeshelikopteret - samme feil oppdaget også i 2009 - Tu.no
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Old 1st Jun 2016, 21:38
  #1050 (permalink)  
 
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I am curious if this (looks like a) similar crack radiating out from the inner race has ever been discussed since the event.

Don't remember any comments . . . .

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Old 1st Jun 2016, 21:42
  #1051 (permalink)  
 
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I am writing here now, as it becomes evident that the
MGB and Rotor assembly change as claimed by CHC and referred in the media have probably not taken place.


MGB change 17 January 2016
MRA change 27 March 2016


With relation to todays released pictures by AIBN
I find it strange that there is already fatigue cracks in
crucial parts of the Main Rotor assembly. A mere month and few flying hours after the claimed change.


In the Public Electronic Postjournal in Norway all the official correspondance between CAAN and CHC are stored in the
Aviation Technical Folder of LN-OJF.
https://oep.no/search/result.html?1=...Number&start=0




These are available to the public, and is now matter of attention to AIBN.


"Undersøkelser av helikopterets vedlikeholdshistorikk har nettopp begynt og vil trolig gi en bedre forståelse av de mest sannsynlige årsakene"


"Investigations of the helicopters maintainance history have just started and will probably give a better understanding of the most plausible causes."




Here are some main points of the maintainence history:


Last Airworthiness Review Certificate is released
11.01.2016


This is the last record in the Aviation Technical Folder of LN-OJF


It is strange that this is released one week before the change of MGB
but no documents thereafter?


The rest of the maintainance history of the MGB is as follows:
14.11.2014:
CHC send Airbus Technical Agreement on extended TBO on MGB
to CAAN. [Can anyone refer to the main points in extended TBO on MGB technical agreement? ]


20.11.2014:
Application for extended TBO on MGB sent from CHC to CAAN


09.12.2014:
Approval of extended TBO by CAAN


16.12.2014:
Airworthiness Review Certificate sent by CHC to CAAN


09.11.2015:
Application for extended TBO on MGB sent by CHC to CAAN


03.12.2015:
Approval of extended TBO on MGB by CAAN


11.12.2015:
Application for second extended TBO on MGB sent by CHC to CAAN


18.12.2015:
Approval of extended TBO on MGB


11.01.2016:
Last Airworthiness Review Certificate sent from CHC to CAAN.




So these electronic journals of the communication between CHC and CAAN are pointing in the direction that someone has information shared with the Media that is not correct.


Where are the documentation, approval and correspondance between CHC and CAAN
after 17 of January until 27 of March, where the claimed MGB and MRA change have taken place?


After that and until the breakdown incident there are no records.


4 times extended TBO on MGB
and there are found fatigue cracks in critical components.




//T
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Old 1st Jun 2016, 21:54
  #1052 (permalink)  
 
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Originally Posted by TylerMonkey View Post
I am curious if this (looks like a) similar crack radiating out from the inner race has ever been discussed since the event.

Don't remember any comments . . . .

I think if you compare the shape of the inner edge,(raceway) you will see that cracked gear you point to is "ovalised" compared to the other example. The location of the crack is where the tensile loads caused by the ovalisation would be very high. I expect the crack to turn out to be as a result of overload. If it was a fatigue crack it would remain 'tight' ( both fracture faces close together) until the remaining material failed in overload. The fact that this crack is "open" also supports the possibility of an overload scenario.
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Old 1st Jun 2016, 21:56
  #1053 (permalink)  
 
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Originally Posted by TylerMonkey View Post
I am curious if this (looks like a) similar crack radiating out from the inner race has ever been discussed since the event.
Seems like that gear was heavily deformed during (self-?) destruction of the gear box and/or on ground impact.
Does not look properly circular in my eyes.
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Old 1st Jun 2016, 22:00
  #1054 (permalink)  
 
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Originally Posted by turboshafts View Post
I am writing here now, as it becomes evident that the
MGB and Rotor assembly change as claimed by CHC and referred in the media have probably not taken place.


MGB change 17 January 2016
MRA change 27 March 2016


With relation to todays released pictures by AIBN
I find it strange that there is already fatigue cracks in
crucial parts of the Main Rotor assembly. A mere month and few flying hours after the claimed change.


In the Public Electronic Postjournal in Norway all the official correspondance between CAAN and CHC are stored in the
Aviation Technical Folder of LN-OJF.
https://oep.no/search/result.html?1=...Number&start=0




These are available to the public, and is now matter of attention to AIBN.


"Undersøkelser av helikopterets vedlikeholdshistorikk har nettopp begynt og vil trolig gi en bedre forståelse av de mest sannsynlige årsakene"


"Investigations of the helicopters maintainance history have just started and will probably give a better understanding of the most plausible causes."




Here are some main points of the maintainence history:


Last Airworthiness Review Certificate is released
11.01.2016


This is the last record in the Aviation Technical Folder of LN-OJF


It is strange that this is released one week before the change of MGB
but no documents thereafter?


The rest of the maintainance history of the MGB is as follows:
14.11.2014:
CHC send Airbus Technical Agreement on extended TBO on MGB
to CAAN. [Can anyone refer to the main points in extended TBO on MGB technical agreement? ]


20.11.2014:
Application for extended TBO on MGB sent from CHC to CAAN


09.12.2014:
Approval of extended TBO by CAAN


16.12.2014:
Airworthiness Review Certificate sent by CHC to CAAN


09.11.2015:
Application for extended TBO on MGB sent by CHC to CAAN


03.12.2015:
Approval of extended TBO on MGB by CAAN


11.12.2015:
Application for second extended TBO on MGB sent by CHC to CAAN


18.12.2015:
Approval of extended TBO on MGB


11.01.2016:
Last Airworthiness Review Certificate sent from CHC to CAAN.




So these electronic journals of the communication between CHC and CAAN are pointing in the direction that someone has information shared with the Media that is not correct.


Where are the documentation, approval and correspondance between CHC and CAAN
after 17 of January until 27 of March, where the claimed MGB and MRA change have taken place?


After that and until the breakdown incident there are no records.


4 times extended TBO on MGB
and there are found fatigue cracks in critical components.




//T
The maintenance review Cert is an annual check / review of the airframe, at the time of the review.

Given the findings of the investigation I would suggest that it is more appropriate to follow the history of the MGB rather than the airframe.
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Old 1st Jun 2016, 22:14
  #1055 (permalink)  
 
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AW009....I enjoyed the Video's you linked.

With the latest news being discussed extant....you wish to expend some additional effort in discounting the possible involvement of the Epicyclic Module as in the previous tragedy?

It is still early in the investigation and lots of questions remain and more work needs to be done but even as an idle spectator to discussion One simply must think Gearboxes just do not fail that often anymore and for two to have gross similarities resulting in a loss of the Main Rotors as a group.....One must wonder why!

I am quietly waiting to hear how all this turns out but evidence keeps turning up that brings us back to a possible cause a lot of folks just do not want to confront for any number of reasons.
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Old 1st Jun 2016, 23:03
  #1056 (permalink)  
 
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From the sideline it is disturbing to observe the similarities to the G-REDL accident.
It is even more disturbing to read the safety recommendations after G-REDL, and probably also the 2012 accidents which Airbus never satisfactory closed.

Adding to this the latest EASB mandates replacements of all bolts related to suspension bars. Airbus states that one of the reasons are findings of wrong washer installation on the suspension bar fitting bolts. The reality is that the washers found to have missing chamfered face toward the bolt head, was an Airbus production flaw, and NOT a wrong installation.

What is wrong with the Airbus organization, and where is EASA???
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Old 2nd Jun 2016, 00:27
  #1057 (permalink)  
 
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n305fa

Normally an extension to maintenance of any type once agreed with the aviation authority would only require further paperwork to be submitted if for example an ammendment was required. Providing the operator has replaced the component within the agreed timescale no further information would be supplied to the airworthiness authority. So I would assume that the gearbox in this case had been replaced or was still within the agreed extension. I cant see why there would need to be further correspondence with the Norwegian authority. As it appears to have been stated that the box was replaced I see nothing in the documents to suggest that this was not the case.

Pi1ot

The use of chamfered washers is common on all helicopters. The maintenance procedures are clear requiring the chamfer to be fitted against the bolt head. If a washer is installed with the chamfer facing the wrong way or without a chamfer then that is clearly a "wrong" (incorrect) installation that should have been picked up on assembly.

Last edited by ericferret; 2nd Jun 2016 at 00:42.
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Old 2nd Jun 2016, 00:38
  #1058 (permalink)  
 
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Helicopters are relatively inefficient flying machines when compared to fixed wing aircraft. In a hovering and low speed manouvering the engine is required to supply sufficient power to support the entire weight of the aircraft rather than being assisted by aerodynamic lift from winged surfaces. This means that weight is of critical importance in helicopter design. Every gram saved increases performance.

I highly suspect that the designers of the gearbox calculated the minimum size and strength requirements for the gear parts and added the necessary safety factors considering only the total cross sectional dimensions of the gears. This is perfectly satisfactory if the parts are of uniform material construction.

Problems arise when parts are surface hardened or carburised (carburized). The dimension of the parts are unaffected but an hardened and brittle outer layer is produced on the component which gives exceptional wear resistance. If for some reason the brittle hardened outer layer fractures, there may be no obvious signs of failure. The softer inner metal layer remains bonded to the hard outer surface and there may be no metal debris, chips or vibrational changes at all.

However, the load on that part is now being carried completely by the softer inner metal of that part. In effect the cross sectional area has been reduced somewhat and its load carrying characteristics are below what the original designer intended. The part does not fail immediately because of the safety factors designed in, but it is subjected to loads in excess of the design limits. The extra stress slowly causes the softer material to start to break up. The part may start to deform slightly and metallic debris and chips are most likely to be found at this stage.

Eventually the part will fail in overload. The problem is that the time span between a crack or fracture in the hardened surface and deformation and failure of the softer carrier metal cannot be calculated. It is unique for every event and dependent on too many variables to be calculated with any accuracy.

Such a damaged part may continue to function for years or fail suddenly due to a momentary extreme load such as an inadvertant abrupt control input causing a sudden demand for power, or sudden air turbulence imposing greater loads on the drivetrain.

So it may prove in this case that the design has shaved just a little too much off of certain critical parts in order to gain that extra bit of performance.

Aviation is by no means unique in having this type of failure mode. Motor racing has exactly the same problems. Designers keep stiffening components and reducing their weight and size until something breaks. Then it is redesigned and beefed up a bit to perform as it needs to. That is the way design progresses.
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Old 2nd Jun 2016, 03:11
  #1059 (permalink)  
 
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@G0ULI Every gram counts both for fixed wing and rotary (or cars for that matter). It all boils down to economics and market forces. Weight costs fuel consumption. The less the aircraft weighs the more freight it can carry (self loading or not) given a specific engine. In effect the fuel cost per unit of freight is reduces. Almost the same goes for the crew: The more freight any aircraft can take, the cheaper the wages for the crew get per unit of freight.

All the bean counters care about is the cost per unit of freight. They constitute "the market", meaning that market forces will drive the manufacturers to produce lighter and lighter aircraft. If you want to get ahead in the market, the trick is to make it as light as possible both by creative use of materials and design, and by minimizing safety margins/shed excess weight. Those that are the boldest pushing this while managing to make people believe it's still safe, will be the market winner. It's going on everywhere you look in society today.

I know way to little about this particular situation and to which degree this philosophy are used with the different aircraft manufacturers, but ever since I read in this thread that the 225 can carry more passengers while being lighter than it's competitors this immediately popped up on my radar. It might be that they have simply pushed it too far.
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Old 2nd Jun 2016, 04:36
  #1060 (permalink)  
 
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AD No.: 2016-0103-E

Part of a smoke screen or not?
Attached Files
File Type: pdf
2016-0103-E.pdf (349.2 KB, 450 views)
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