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EC225 crash near Bergen, Norway April 2016

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EC225 crash near Bergen, Norway April 2016

Old 14th Jun 2016, 18:20
  #1321 (permalink)  
 
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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.
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Old 14th Jun 2016, 19:54
  #1322 (permalink)  
 
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Gears

RVDT and One-P, thanks for the illuminating education. Good thought re the acoustic signature, and the AH group is undoubtedly all over that if the evidence is usable and shows anything. The idea of eccentricities or even gear resonances is probably getting a good look. The CH-47A production prototypes at the Army Aviation Test Board at Ft Rucker had at least two incidents ( 1962-3 ) where the engine nose box literally exploded and the parts were ingested into that engine, making a further mess and resulting in unplanned landings, one on the Officers Club Golf Course. Traced to a gear resonance and the short term fix was to change the Nr from 204 to 230. Stuff happens.

It's a bit surprising to read some of the "End of the 225" thread posts. I may be a former member of what the AH folks probably refer to as the Evil Empire, but having been involved in a few of these particularly thorny investigations, I'm actually quite sympathetic to the situation facing the operations and test troops there. Two failures in so many hours suggests patience.
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Old 14th Jun 2016, 21:35
  #1323 (permalink)  
 
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Originally Posted by OnePerRev View Post
John,
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.
Having done the SA330 ( Puma ) course in 1970, I remember that the MGB was designed and manufactured by FIAT AVIAZONE.
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Old 15th Jun 2016, 03:08
  #1324 (permalink)  
 
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Originally Posted by JohnDixson View Post
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?
One fatigue analysis case used to design helicopter transmission components like gears/bearings/etc is based on a composite (cubic mean) of the various speed/load operating conditions and times over a typical mission profile. The 5000 hour number is likely a minimum design requirement at the composite speed/load condition. There are also other fatigue analysis cases considered, such as OEI and max torque, that involve far lower numbers of load cycles.

As for qualification tests performed on an MRGB, take a look at FAR 27.923.
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Old 15th Jun 2016, 03:30
  #1325 (permalink)  
 
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Originally Posted by BedakSrewet View Post
Having done the SA330 ( Puma ) course in 1970, I remember that the MGB was designed and manufactured by FIAT AVIAZONE.
You are absolutely correct BedakSrewet, this transmission was indeed designed and manufactured by Fiat Aviazone. I seem to remember it was all the parts painted blue on the SA330 and subsequent evolution of helicopters that originated there. As another poster earlier noted, this organization evolved into Avio, which is of course now owned by General Electric. GE in turn is further involved in the leasing activities affected by the CHC actions, as well of course as the manufacturer of the CT7 engines in the S92. You couldn't make this stuff up if you tried!
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Old 15th Jun 2016, 05:43
  #1326 (permalink)  
 
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riff_raff,

As for qualification tests performed on an MRGB, take a look at FAR 27.923.
???? EC225 is a Transport Category aircraft so you would need to apply Part 29 requirements. You may find it a little more extensive.
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Old 15th Jun 2016, 05:55
  #1327 (permalink)  
 
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Originally Posted by Cyclic Hotline View Post
You are absolutely correct BedakSrewet, this transmission was indeed designed and manufactured by Fiat Aviazone. I seem to remember it was all the parts painted blue on the SA330 and subsequent evolution of helicopters that originated there. As another poster earlier noted, this organization evolved into Avio, which is of course now owned by General Electric. GE in turn is further involved in the leasing activities affected by the CHC actions, as well of course as the manufacturer of the CT7 engines in the S92. You couldn't make this stuff up if you tried!
Indeed Cyclic Hotline. One of my ( Dutch ) colleagues referred to it as 'KLM blue'. The lawyers will have a 'field day' ( years ) once they commence legal action against AH and the OEM of the MGB.
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Old 15th Jun 2016, 12:00
  #1328 (permalink)  
 
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Post 1335

Thanks, Riff Raff,

I did look at my 1999 copy of AC 29-2C ( just assuming that something similar applied to the EC225 design/qual effort ), which provides the test/qualification methods the FAA expects to see that support compliance with the basic FAR Pt 29. In this case 29.923, and those procedures look like they pertain to the tie down aircraft endurance runs etc, so the underlying requirement would remain as One-P described, a design to 140% of max load. There is a statement I found offering an alternative test to 10-7th cycles with an appropriate power spectrum. Does that square with where you were going?

Last edited by JohnDixson; 15th Jun 2016 at 12:01. Reason: Typo
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Old 15th Jun 2016, 17:34
  #1329 (permalink)  
 
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29.923 is endurance, which evaluates wear and general durability - different than fatigue. Fatigue comes from 29.571. The regulation does not specify handling any different for gears, but the AC does have an entire section on gear fatigue. It is intended, as it states, to be specifically for gear tooth bending, however it does mention that "fatigue damage other than tooth fatigue should be considered for test validity and the integrity of the affected part confirmed as necessary" The pinion rim failure mode should now, if it was not originally, be considered a catastrophic failure mode. This would then necessitate that the fatigue evaluation be conducted for it using the non-gear guidance -which will be quite complicated. Why? besides multiple specimen, 3 sigma, the initiation is coming from a bearing integral raceway. This gets tricky now, as the puma family is not certified to the latest damage tolerant standards, so the evaluation could simply assume surface finish as new. A little bearing wear, lubrication concerns, and/ or load changes, make this a complicated scenario. If there is no replacement time for the pinion, then they could be re-using pinions at overhaul with an unknown number of hours. Of course we still don't know if this is an early symptom, or the root cause.
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Old 15th Jun 2016, 18:04
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WOW...used to think I was not terribly bright but the last few posts lead me to believe I am the burned out bulb on the old "connected in series" xmas tree light string.
Thanks for posting the interesting stuff.
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Old 15th Jun 2016, 18:19
  #1331 (permalink)  
 
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29.923

Only mentioned that as Riif Raff had referenced it above.

Your explanation of the implications of the pinion failure mode as a catastrophic failure and to be treated as such against the updated damage tolerance standards, if accepted, will certainly increase the sales of Pepto-Bismol in certain sectors of the industry. Gets back to waiting for the AIB and AH people determining the underlying cause and progression of the failure.
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Old 15th Jun 2016, 19:30
  #1332 (permalink)  
 
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This came from AH this afternoon
15/06/2016
[EC 225]
"E"ASB 05A049 TIME LIMITS - MAINTENANCE CHECKS – Main rotor drive - Check of the Main Gearbox (MGB) oil filter and chip detectors, limitation of the epicyclic modules. - Rev0
Through this ALERT SERVICE BULLETIN, Airbus Helicopters introduces the following precautionary measures for helicopters which are not subject to EASA Airworthiness Directive No. 2016-0104-E: - inspection of the MGB oil filter and chip detectors after the last flight of the day, - identification of the epicyclic modules which have been involved in an unusual event since new or Complete Overhaul, for a return for Complete Overhaul.
Download EASB / TA document
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Old 15th Jun 2016, 21:50
  #1333 (permalink)  
 
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It seems that the MGB transport supply chain is under the spotlight as it may be a contributing factor here. Could the fix be relatively simple?
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Old 15th Jun 2016, 22:03
  #1334 (permalink)  
 
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Originally Posted by terminus mos
It seems that the MGB transport supply chain is under the spotlight as it may be a contributing factor here. Could the fix be relatively simple?
Yeah. Sounds like it - a wee 'fragile' sticker on the crate and it'll be grand.

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Old 16th Jun 2016, 07:36
  #1335 (permalink)  
 
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So we have an MGB that has to be treated like a crate of eggs?

I've watched freight forwarders handle goods, and it usually ain't pretty. How is anyone at each end of the supply chain (operator or MRO facility) meant to know exactly what has happened to the crate during transit?

Oh dear, what a mess!!
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Old 16th Jun 2016, 08:31
  #1336 (permalink)  
 
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Impact Indicators | G-Force & Go/No-Go Monitoring Devices that Alert to Mishandling | ShockWatch

simple really
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Old 16th Jun 2016, 08:49
  #1337 (permalink)  
 
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I can see the future as we speak.
All you Aerosexual Aviation Freaks will love this.

Lets start with the acronym first.

SCRTVDL

"Self Contained Real Time Vibration Data Logging" for anyone who gives a half a flying f.u.c.k. about the transport of anything worth more than they can afford to lose.

You can buy this Bad Boy on EBAY right now
LUTRON BVB-8207SD 4 Channels Vibration Meter Recorder Real Time Data Recorder



So for just $1250 US you can shove the Overhaul cost of your next Engine or Gearbox right up the Shipping Company's you know what.
This reply started out as a joke, but you watch the concept become reality.

Last edited by buzz66; 16th Jun 2016 at 09:22.
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Old 16th Jun 2016, 09:27
  #1338 (permalink)  
 
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You might be a bit late out of the blocks there buzz.


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Old 16th Jun 2016, 09:55
  #1339 (permalink)  
 
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Yeah I saw the previous post after I wrote, but yeah fair call.
It's a simple no go indicator but I think it needs a bit more than that.

It's not uncommon for a Gearbox to sit on the back of a truck for extended periods of time on less desirable Roads here in Australia. I would think an AIR Ride Truck would be mandatory?
Would a Truck with Bad Vibs @ X frequency over X Time be OK with the residual oil as protection..?.....you would think so.

This is where you need to see the big picture. If in transport an item is subject to what might be considered undue stress. The Shock Dot won't depict when it happened.
This is bad news for Greedy Corporations that want to pin the blame on someone.

What you need is my solution so the World's balance of true Distortion & Greed remain intact and keep everyone happy.
The Shock Dot is far to Practical, Simple, & Reliable to ever be put in place in Aviation.
The other problem with your solution is the "Made in USA"...

Last edited by buzz66; 16th Jun 2016 at 11:00.
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Old 16th Jun 2016, 11:48
  #1340 (permalink)  
 
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I think it was more than a 'rough ride' or handling.......
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