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  #21  
Old 03-03-2020, 01:16 PM
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Thermos Thermos is offline
 
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Default Information from the FAA

I just finished a phone call with the FAA certification engineer who's overseeing this AD process. The affected crankshafts were actually made by ECI, not Superior.

The FAA has given to Superior the metallurgy analysis that confirms the abnormal "white layer" mentioned in the AD and they've received little pushback from Superior or industry so unless something changes in the next week and a half, the AD will likely become law.

Dave
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Last edited by Thermos : 03-03-2020 at 01:35 PM.
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  #22  
Old 03-03-2020, 04:16 PM
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Tandem46 Tandem46 is offline
 
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Quote:
Originally Posted by Thermos View Post
The affected crankshafts were actually made by ECI, not Superior.
Wait...what?!?!?! The affected cranks have Superior serial numbers?? Also, what about all that business the other day about ?Bill Ross and Superior claim that the crankshafts that failed had all been tested by an "independent" (Superior's words) organization...?? Why would ?Bill? be defending the cranks if they weren?t even Superior cranks. Lastly, the AD clearly states Superior, not ECI.

Anyway, I?m confused.
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  #23  
Old 03-03-2020, 06:08 PM
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Originally Posted by Tandem46 View Post
Wait...what?!?!?! <snip> Anyway, I’m confused.
Not making ‘em up, just passing on the information I was given. Feel free to call the FAA directly to confirm.

And yes, the crankshafts were made by ECi. In fact, the last Superior engine kit my engine shop received came with an ECi crank. I’m also told by my engine shop that Lycoming also subs out their crankshaft manufacturing.

ds
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Last edited by Thermos : 03-03-2020 at 07:11 PM.
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  #24  
Old 03-04-2020, 02:33 PM
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I just got off the phone will Bill Ross myself. He indicated to me that the three metallurgical results he has

1) do not indicate that "white layer" or any other material problem caused the failures
2) all three failed crankshafts met the relevant SAE or ASTM standards and in particular the white later was well below the one thou maximum called out in the standards as well as the cranks exceeding the hardness requirements
3) there is actually no evidence showing white layer reduces, and may even increase, surface hardness (which is beside the point)
4) all lycoming, superior, titan, and eci cranks are made to the same standards particularly the max white layer thickness, approved by the faa
5) all three cranks failed at different locations
6) the serial numbers called are are simply due to lot tracking. the nprm calls out all cranks made in the lot that included the failed cranks
7) no materials or process changes occurred prior to or after the lot in question,iow they are identical for all intents and purposes to pretty much all the same model crank in all lots and for all engine companies
8) if the standard itself is called into question, pretty much any ga piston engine will be affected

All that being said, speaking from 1st hand experience, the faa is the faa, and once its made up its mind it is impervious to facts. In fact, facts just make the faa dig their heels in harder.

I specifically asked "regardless of fact, if the faa moves forward with this AD, what plans does superior have to stand behind its customers?" (I had previously alluded to crank replacement and covering labor). Bill said no plans had been made all efforts to date were to work with the faa to prevent an AD.

Superior is putting together is package of metallurgical analysis to meet the nprm deadline.
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  #25  
Old 03-04-2020, 04:15 PM
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Exceeding the hardness specs is probably not a good thing. Hardness reduces ductility and I've seen a couple of too-hard cranks in the race world suffer sudden breakages in only a few hours.

White layer formation always increases hardness in that area. Again, that may not be what you want.

Generally you only want the surface hard which is why most cranks undergo some form of gas or liquid nitriding. This should give a hard surface for wear resistance and a "skin" of hi tensile steel for fatigue resistance' A glass hard crank all the way through would be a recipe for failure, just like putting a bending load on a hand file. It doesn't bend far, just snaps.

The fact that the cranks all broke in different places is especially worrisome in my view.

Will be interesting to see what the next round of metallurgical analysis shows.
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RV10 95% built- Sold 2016
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Last edited by rv6ejguy : 03-04-2020 at 04:22 PM.
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  #26  
Old 03-04-2020, 04:39 PM
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Quote:
Originally Posted by rv6ejguy View Post
Exceeding the hardness specs is probably not a good thing. Hardness reduces ductility and I've seen a couple of too-hard cranks in the race world suffer sudden breakages in only a few hours.

White layer formation always increases hardness in that area. Again, that may not be what you want.

Generally you only want the surface hard which is why most cranks undergo some form of gas or liquid nitriding. This should give a hard surface for wear resistance and a "skin" of hi tensile steel for fatigue resistance' A glass hard crank all the way through would be a recipe for failure, just like putting a bending load on a hand file. It doesn't bend far, just snaps.

The fact that the cranks all broke in different places is especially worrisome in my view.

Will be interesting to see what the next round of metallurgical analysis shows.
I agree with all your statements except I consider that they broke in different place to indicate that there were likely different reasons, or at least in my mind reduces the likelihood of a weak location or specific process problem.

I may have worded my statement when I said "exceeded" hardness. I meant was within standards, higher than the minimum requirement.

Bill also read to me verbatim the conclusion of all three reports. Two included a phrase indicating ductility was not an issue. The third had a phrase to the effect of (or something like) operation below temperature may have had an adverse effect on ductility.

Anyway, we need to wait and see for at least another 12 days.
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  #27  
Old 03-04-2020, 05:40 PM
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Quote:
Originally Posted by walkman View Post
I agree with all your statements except I consider that they broke in different place to indicate that there were likely different reasons, or at least in my mind reduces the likelihood of a weak location or specific process problem.

I may have worded my statement when I said "exceeded" hardness. I meant was within standards, higher than the minimum requirement.

Bill also read to me verbatim the conclusion of all three reports. Two included a phrase indicating ductility was not an issue. The third had a phrase to the effect of (or something like) operation below temperature may have had an adverse effect on ductility.

Anyway, we need to wait and see for at least another 12 days.
Ok, within hardness spec means that's probably not causal.

My concern with the 3 different breakage locations, (assuming no other outside influences), is that they may not be able to find the smoking gun as easily and this more likely then points to material flaws in these 3 examples.

If all material, heat treatment and hardness is within specs and the engines were operated within specs with approved props so harmonics are not an issue, these cranks should not have broken.

Might take some deep digging and analysis here...
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Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 448.3 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
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  #28  
Old 03-04-2020, 05:42 PM
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Quote:
Originally Posted by walkman View Post
I agree with all your statements except I consider that they broke in different place to indicate that there were likely different reasons, or at least in my mind reduces the likelihood of a weak location or specific process problem.

I may have worded my statement when I said "exceeded" hardness. I meant was within standards, higher than the minimum requirement.

Bill also read to me verbatim the conclusion of all three reports. Two included a phrase indicating ductility was not an issue. The third had a phrase to the effect of (or something like) operation below temperature may have had an adverse effect on ductility.

Anyway, we need to wait and see for at least another 12 days.
Ok, within hardness spec means that's probably not causal.

My concern with the 3 different breakage locations, (assuming no other outside influences), is that they may not be able to find the smoking gun as easily and this more likely then points to material flaws in these 3 examples.

If all material, heat treatment and hardness is within specs and the engines were operated within specs with approved props so harmonics are not an issue, these cranks should not have broken. Multiple reasons for failure may open more cans of worms.

Might take some deep digging and analysis here...
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Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 448.3 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
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  #29  
Old 03-04-2020, 11:36 PM
rwtalbot rwtalbot is offline
 
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Having seen a number of these types of issues with cranks and cylinders, I would say that the manufacturers seldom go down easily. Not that I am implying that anyone does anything untoward, but there is often a difference of opinion as to cause and effect.

Crankshafts should not break in service - ever. They are engineered to last indefinitely. Even to crack due to a previous prop strike is a concern, as that shaft should have been subject to MPI and other inspections. Cold weather? not that either.

As a consumer I am happy for someone else to make a (conservative) call. I am quite certain last time I bought a crank I paid a heavy premium for that level of safety and traceability.

No doubt Superior will come to the party if necessary. There will be some aggravation and cost for some, but if it wasn't like that we would all be flying behind lawn mower engines.
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  #30  
Old 03-05-2020, 03:41 AM
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All that being said, speaking from 1st hand experience, the faa is the faa, and once its made up its mind it is impervious to facts. In fact, facts just make the faa dig their heels in harder.
I respect your opinion based on experience but I must disagree with your blanket categorization of the FAA as fact-resistant, especially in an area like this where engineering analysis is involved.

I’m familiar with the AD process, having worked for several years as a flight test engineer in an FAA aircraft certification office. There are multiple levels of review happening here, not only in Fort Worth where the AD was initiated, but also by the staff in Boston who oversee engine certification at a national level. This issue would never have risen to the NPRM level if these organizations didn't believe that their data and risk analyses warranted it.

I'm sure that Bill Ross and Superior are committed to safety - I hope so, because I have one of their engines ready to fly on my RV-7. But they're also facing the potential for a >$1M hit if this becomes a legal issue so it's in their interest to interpret their data as they do. The cert process is (or should be) about safety checks and balances, and that's why I won't dismiss the FAA's position.

ds
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Last edited by Thermos : 03-06-2020 at 09:08 AM.
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