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New (February 2020) FAA AD - Superior Air Parts Crank Shaft

I emailed Superior to enquire about the AD as I was unsure if it will affect our engine - unfortunately it does. 150TTSN engine (sad face).

Would love to know at what engine hours the failures occurred and in what applications those engines were used.

Attached is the response I got from Mr Ross from Superior. Very chuffed with the quick feedback from them, but looks like it’s a case of “let’s wait and see”.

Superior Response:

Mr. Grobler,

I received your inquiry from a member of our customer service team. Our records indicate the engine serial number you provided was equipped with crankshaft serial number SP14-0161. This serial number does fall within the affect range on the proposed AD.

However, Superior only became aware of this proposed AD during the week of Feb 3. We are still gathering information from the FAA and working to a resolution. The metallurgical examination performed by an independent laboratory on each conclude there is not a metallurgical issue with the crankshafts and cites abuse as probable reason for fracture. The FAA has performed no metallurgical testing on these or any Superior crankshafts. Experimental aircraft are not affected from a regulatory point of view. However, Superior is committed to the safety of its customers and will immediately contact each if it is determined that an unsafe condition does in fact exist.

Thank you,

Bill Ross
VP of Product Support
 
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I wonder if the FAA or the NTSB has published the finding to the root cause of the fatigue cracking yet other than just issue the AD.
 
I wonder if the FAA or the NTSB has published the finding to the root cause of the fatigue cracking yet other....

Yes, its in the AD.

...”gaseous nitrocarburization resulted in excessive residual white layer forming on the assemblies. This white layer is brittle and can lead to spalling or fatigue cracking of the crankshaft assembly as a result of the normal mechanical loads during engine operation. ”
 
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Interesting!

I also contacted Superior about the proposed AD after first checking the engine log?s parts inventory. Their representative confirmed from their records that my engine?s crank does not fall within the proposed AD. Lucky I guess!

While I don?t know Bill Ross personally, my few conversations with him at AirVenture lend me to believe Superior will try to work with their clients if the problem stems from a manufacturer?s defect. Let?s hope.
 
For those with Superior engines (like me - we have one on our Tundra), if you;re wondering about the affected range of cranks, I checked with the company, and it appears that the cranks in the AD were from the 2012 - 2014 timeframe. Ours was from back in 2004, so we’re clear. This might help with the angst...at least for those with older or younger cranks!

Paul
 
I always wondered where the term ‘You’re a bit CRANKY” was derived. Now I know.
My apologies by those affected. Truly a bummer....
 
Anyone have an idea of the timeline looks like for an AD like this? What to expect in the near future and how to get into the air again ASAP? This is the first time I?ve been affected by an AD and have no idea what I?m in for...

Also, if it gets confirmed after said timeline (a week, a month, 6 months - I have no idea) that the affected crankshafts need replacing, does Superior send each operator a new crankshaft for their account and the labour is for the owner?s account or what is usually the outcome? Just need to know if I should start budgeting for a crankshaft, only the labour or a new (read Lycoming) engine...(me trying to make a joke to lift my own spirits on the matter).

Some clarity will be most appreciated!
 
Anyone have an idea of the timeline looks like for an AD like this? What to expect in the near future and how to get into the air again ASAP? This is the first time I’ve been affected by an AD and have no idea what I’m in for...
The FAA’s comment period for this AD closes on 16 March. At that point they will look at inputs from Superior, AOPA and other interested parties and decide to either keep the AD as-is (likely), amend it (possible) or withdraw it (unlikely). If the AD is put into US law, it’s up to the SACAA to determine how it applies to you but most CAAs have reciprocal agreements to recognize other countries’ ADs. So best case, I wouldn’t expect to see anything definite before late March.

Like you, I’m affected (and only a few weeks from being finished and ready to fly :mad:). The shop that built my engine, Unlimited Aero Engines, repaired one of the failed engines that led to the AD and Superior was very good about sending replacement parts at no charge and paying for labor. I hope they’ll be as responsive in this case.

Unlimited is communicating with Superior this afternoon and I’ll pass on what I find out.

Dave
 
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The FAA?s comment period for this AD closes on 16 March. At that point they will look at inputs from Superior, AOPA and other interested parties and decide to either cancel, amend or keep the AD as-is. If the AD is put into US law, it?s up to the SACAA to determine how it applies to you but most CAAs have reciprocal agreements to recognize other countries? ADs. So best case, I wouldn?t expect to see anything definite before late March.

Like you, I?m affected (and only a few weeks from being finished and ready to fly :mad:). The shop that built my engine, Unlimited Aero Engines, repaired one of the failed engines that led to the AD and Superior was very good about sending replacement parts at no charge and paying for labor. I hope they?ll be as responsive in this case.

Dave

Thanks for the feedback Dave. Exactly what I wanted to know. Let?s hope for the best!
 
Yes, its in the AD.

...?gaseous nitrocarburization resulted in excessive residual white layer forming on the assemblies. This white layer is brittle and can lead to spalling or fatigue cracking of the crankshaft assembly as a result of the normal mechanical loads during engine operation. ?

Does anyone know if this gaseous nitro carburization occurred during mfg, like during nitriding etc, or is it something that occurs during operation? I have never heard this term before.
 
Does anyone know if this gaseous nitro carburization occurred during mfg, like during nitriding etc, or is it something that occurs during operation? I have never heard this term before.

White layer formation can only happen during the manufacturing process. Nitro carburization is an intentional, surface steel hardening process used similarly to gas nitriding but at lower temperatures to minimize part distortion.

My understanding is that quench oil vapor contamination during part heating is thought to be a likely cause of white layer formation but someone with more real-world knowledge of heat treating, hardening and quenching processes could say more on the subject.

White layer formation is often hard to detect, say optically, without an actual hardness (ball) test. I know some machinists have run into the problem where high temps induced by the machining process can cause a white layer to form which kills the tool pretty fast.

It would appear to be a process control defect or oversight here to cause this issue as is usually the case where some cranks fail while the majority of them live for thousands of hours. We have seen process control issues at Lycoming also before as well as alloy recipe changes, resulting in crank failures. Nobody is immune. This stuff is all really critical to get consistently reliable cranks. A tiny change in the established and validated processes or material can cause premature failure.

I learned a bit about hardening and quenching steel decades ago from a old and wise gunsmith friend. My memory maybe isn't correct on some details here so someone with intimate knowledge of this subject, please correct any errors.
 
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White layer formation can only happen during the manufacturing process. Nitro carburization is an intentional, surface steel hardening process used similarly to gas nitriding but at lower temperatures to minimize part distortion.

My understanding is that quench oil vapor contamination during part heating is thought to be a likely cause of white layer formation but someone with more real-world knowledge of heat treating, hardening and quenching processes could say more on the subject.

White layer formation is often hard to detect, say optically, without an actual hardness (ball) test. I know some machinists have run into the problem where high temps induced by the machining process can cause a white layer to form which kills the tool pretty fast.

It would appear to be a process control defect or oversight here to cause this issue as is usually the case where some cranks fail while the majority of them live for thousands of hours. We have seen process control issues at Lycoming also before as well as alloy recipe changes, resulting in crank failures. Nobody is immune. This stuff is all really critical to get consistently reliable cranks. A tiny change in the established and validated processes or material can cause premature failure.

I learned a bit about hardening and quenching steel decades ago from a old and wise gunsmith friend. My memory maybe isn't correct on some details here so someone with intimate knowledge of this subject, please correct any errors.

This sounds quite accurate compared to what I was taught in engineering school.

Does anyone here know at what engine hours these crankshaft failures occurred? Is there a trend or was it random high/low hours? It?s not going to make me fly if all failures were at high engine times, but I?m curious and might as well make up some time while waiting for answers from FAA/Superior...(sigh)
 
Does anyone here know at what engine hours these crankshaft failures occurred? Is there a trend or was it random high/low hours?
IIRC from the conversation with my engine builder, the crankshaft he replaced (one of the three failures that triggered the AD) had a little under 700 hours on it.

Dave
 
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Unlimited is communicating with Superior this afternoon and I’ll pass on what I find out.
I just got off the phone with my engine builder, who had just finished a conversation with Bill Ross from Superior.

Bill Ross and Superior claim that the crankshafts that failed had all been tested by an "independent" (Superior's words) organization who verified that each crankshaft met its ASTM materials standards. Nothing new here, they've already said as much in a press release.

They also claimed in this morning's call that these crankshaft failures were the result of abuse - one due to an engine overspeed, another due to a previous prop strike, and the third due to the throttle being advanced to full power on an engine that hadn't warmed sufficiently. I don't know the conditions surrounding the first two failures, but the third is sending up some BS flags for me as I live in New England - if firewalling the throttle on a cold engine is enough to fail the crankshaft, then we'd have engine failures galore around here every Winter.

Unfortunately, this AD could drag on for awhile after the comment period closes if the FAA and Superior can't come to an agreement on root cause and methods of compliance.

Dave
 
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Previous prop strike-valid cause, overspeed- valid cause, Revving up when cold- I hope the design is not that marginal...
 
Previous prop strike-valid cause, overspeed- valid cause, Revving up when cold- I hope the design is not that marginal...

I wholeheartedly agree with you. Sounds like their grasping at straws here...

I hope the wait doesn?t have to continue much longer after 16 March. And I do hope the best decision is made to get everyone safely back in the air again. I don?t want to fly behind an engine I don?t trust...been there, done that, got the T-shirt!
 
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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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.
 
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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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.
 
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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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.
 
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...
 
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...
 
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.
 
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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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.

Those are good words, Ross. These are PMA'd crankshafts so Superior/ECi had to show that they meet the same design and production standards as the original Lycoming part. To the best of my knowledge, Lycoming's crankshafts haven't had problems and it's reasonable to assume that they've been exposed to the same usage spectrum as Superior/ECi's products.

Dave
 
If ... the engines were operated within specs with approved props so harmonics are not an issue, these cranks should not have broken..

This is part of the problem. From memory at least one of the reports indicated a possible prior prop strike.
 
Anyone with latest news on this matter? Burning to get back in the air!

There's no AD at the moment, and you're flying an experimental anyway. There's nothing keeping you on the ground except your own suspicions.

If I wasn't down for maintenance I'd do at least local flying. Maybe not long over water or IFR legs though.

Mar 16 is the date on the NPRM
 

Thanks for the link.

But delay the entire process by another 2 months? I?m sure most operators would rather just like to get this resolved as quickly as possible?

If I knew the risk is minimal, I would still be flying, but getting up in the air now feels like playing russian roulette - knowing you have a potential issue, choose to ignore it and then just ?hope for the best?... not the way I think a good aviator should take to the skies.

Aviation, especially general aviation, is a game of risks and when we take to the skies we take calculated risks, be it with weather, fuel reserves, runway lengths, takeoff weight or mechanical dependability. Maintaining the aircraft I fly to the highest standard has always been my goal to know I can trust the machine I carry myself and loved ones in. Knowing there is a potential flaw (probably fatal) in the system and going for a flight is borderline reckless in my opinion.

We spent tens of thousands of dollars of our hard earned money buying a ?Superior? engine that now turned out to be ?inferior?. I think it?s time for Superior to step up to the plate and give a decent response as to how we are going to get this resolved ASAP.

The FAA won?t send a serious note like this out ?for the fun of it?. I?m sure they will have valid reasons for their evaluation of the flaw in the crankshafts. AOPA extending the comment time won?t make the crankshafts fix themselves over said period. They have to be replaced at one stage or another anyway.

Maybe my view on this is flawed, but it is how I see it and I truly hope it can be resolved for once and for all.

JP
 
Just read Superior?s response.

Cliff?s notes as I read it:
An independent lab looked at each crank.
All three cranks were well within the ?white layer? spec.
All three cranks showed signs of abuse.
All three cranks were in a flight school environment.
 
Superior Crankshaft Failures

I found it interesting in the second metallurgical report they found:
?The tensile properties of the Crankshaft material were outside the range of the specified limits?
They went on to say this wasn?t the cause of the failure but if your crankshaft as manufactured doesn?t meet specifications for tensile strength isn?t that a problem ?
 
Requirements

I found it interesting in the second metallurgical report they found:
?The tensile properties of the Crankshaft material were outside the range of the specified limits?
They went on to say this wasn?t the cause of the failure but if your crankshaft as manufactured doesn?t meet specifications for tensile strength isn?t that a problem ?

According to the Superior response, 2 of the 3 crankshafts failed to meet requirements.
 
.....All three cranks were in a flight school environment.

This is news to me and very telling. Not saying the cranks should fail so easily but new students can definitely be very hard on engines. Maybe SAP has a case after all.
 
I heard a rumour that should the AD go through, we will only start receiving cranks 12 months from now :(

Anyone else with first hand info on this? Would?ve loved to get back in the air after lockdown as we aren?t allowed to fly during our lockdown in South Africa.

Frustrating to say the least!
 
Interesting, can you share the source of that information? But it doesn't surprise me...my engine builder says there are a limited number of companies producing crankshafts for Lycoming, Superior and ECi.

Dave
 
Interesting, can you share the source of that information? But it doesn't surprise me...my engine builder says there are a limited number of companies producing crankshafts for Lycoming, Superior and ECi.

Dave

The AP across from our hangar mentioned to me that he heard from Superior that it will take that long to push out the crankshafts as he enquired about a new engine he want to purchase for his client.

So don?t quote me on this as it is far from first hand info, but hopefully it won?t take as long. If the risk was negligibly small, I would?ve been flying by now. But not sure what the risk is.
 
My day job is in oilfield compression, and we are having a hard time sourcing crankshafts for our compressors as well. There are just a small number of shops with the ability to do this work, and things get backed up sometimes. I can only imagine the headaches the FAA process would add to that.
 
This is news to me and very telling. Not saying the cranks should fail so easily but new students can definitely be very hard on engines. Maybe SAP has a case after all.

With the exception of a ground strike, I don't know what an operator can do with an engine to fail the crank. This does not make sense to this engine engineer of 40 yrs.

I accessed the AD proposal and docket and it was lacking in detail information/documentation for the determination of root cause. Nothing on the engine specifications or hours.

One failure was 1/4" subsurface, which screams metallurgy and/or heat treat to me. I can not see how a surface site layer has anything to do with that. 99% of all part loading have peak stresses on the surface of the part.
 
With the exception of a ground strike, I don't know what an operator can do with an engine to fail the crank. This does not make sense to this engine engineer of 40 yrs.

I accessed the AD proposal and docket and it was lacking in detail information/documentation for the determination of root cause. Nothing on the engine specifications or hours.
I spoke with the FAA engineer overseeing this AD, I think that's their position as well. But they haven't publicly released their metallurgical analyses so we only have Superior's side of the argument.

ds
 
The 60-day extension period has come and gone. Any news from the FAA or Superior regarding the matter?

Does anyone know if Superior has been working on this? (not sure what the conditions in the US currently is with regards to lockdown etc from COVID-19)
 
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