EC225 crash near Bergen, Norway April 2016
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.
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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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.
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.
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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?
As for qualification tests performed on an MRGB, take a look at FAR 27.923.
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!
riff_raff,
???? EC225 is a Transport Category aircraft so you would need to apply Part 29 requirements. You may find it a little more extensive.
As for qualification tests performed on an MRGB, take a look at FAR 27.923.
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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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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?
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
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.
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.
Thanks for posting the interesting stuff.
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.
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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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
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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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?
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!!
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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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.
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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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"...
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.
I think it was more than a 'rough ride' or handling.......