IO550 Camshaft Gear SB - If becomes AD, Then Costly

[mooneyflyer]

Got this email from Mike Busch on a potentially costly AD on IO550, if FAA so decides...

Important News for Continental 520/550 Owners View this email in your browser SAVVYMX SAVVYQA PREBUY ANALYSIS BREAKDOWN Important News for Continental 520/550 Owners Extremely costly AD may be in the works Late last week, Continental Motors issued Mandatory Service Bulletin MSB05-8B affecting all 520- and 550-series engines (plus a few IO-470s). Now normally Part 91 operators are not required to comply with manufacturer's service bulletins. However, when Continental issues a Mandatory Service Bulletin, it means that they have asked the FAA to issue an Airworthiness Directive (AD) to make compliance compulsory. That's the case with MSB05-8B. The backstory began in 2005, when Continental issued Service Bulletin SB05-8 announcing the release of an improved camshaft gear (part number 656818) to replace earlier camshaft gears (part numbers 631845, 655430, 655516, and 656031). The new-style gear was slightly thicker (by 0.060") than the older-style ones. SB05-8 recommended (but did not require) that the new-style camshaft gear be incorporated at the next engine overhaul or whenever replacement of the camshaft gear was necessary. Then in November 2009, Continental revised another service bulletin (SB97-6) to make it mandatory for the older-style camshaft gear to be replaced with the thicker 656828 camshaft gear at engine overhaul. (SB97-6 is the service bulletin that specifies what engine parts must be replaced at engine overhaul, and so compliance is required to call it an "overhaul" as opposed to a "repair.") Replacing the camshaft gear can only be accomplished if the engine is completely disassembled (crankcase split), so the only reasonable time to perform this replacement is when the engine is being overhauled, or when the case is split for some other reason (e.g., a post-prop-strike inspection). It also turned out that for Permold-case engines (used in Bonanzas, Barons, Cirruses, Columbias and twin Cessnas, among others), the new thicker camshaft gear had an interference problem with the crankcase, so the crankcase must be modified in order to use the new-style gear. So far, no problem: The new-style gear has to be installed when the engine is overhauled. Now, for many years Continental's official recommendation has been that their engines should be overhauled at some recommended number of hours (TBO) or after 12 years in service, whichever comes first. This is only a recommendation, not a regulatory requirement, so many owners run these engines past TBO and almost nobody pays any attention to the 12-year calendar-time recommendation. Is it coincidental that on the 12-year anniversary of SB05-8, Continental Motors has "promoted" its service bulletin to "mandatory" status, and asked the FAA to issue an AD to make it compulsory? Hard to tell.  Exactly why Continental decided to do this now is not entirely clear. So far, they aren't saying. My best guess is that this may have arisen from December 2015 engine failure incident involving a Beech Bonanza that experienced a catastrophic engine failure and made a successful forced landing. The cause of the engine failure was ultimately determined to be fatigue fracture of three adjacent teeth on the camshaft gear, which was an older-style 655516 gear. (The engine was a Continental factory rebuilt engine manufactured in 2001.) So far, I have not been able to uncover any other recent camshaft gear-related engine failures in Continental 520- or 550-series engines, although Continental apparently told the FAA late last year that it has seen a few damaged gears that could possibly have progressed to failures had they remained in service. Best I can tell, such failures are extraordinarily rare events. Savvy manages the maintenance of many hundreds of 520- and 550-powered aircraft with the older-style gear installed, and in the eight-plus years we've been doing so we have yet to encounter a single camshaft gear failure. In the wake of the Bonanza incident, Continental's legal department may want to get all the older-style gears out of the system ASAP for liability reasons. (A more cynical school of thought holds that issuance of an AD requiring immediate teardowns would create a big financial windfall for the company. Personally, I'm more inclined to blame the lawyers than the bean counters.) Now here's the rub: MSB05-8B calls for replacing the gear "within the next 100 hours of operation, at the next engine overhaul (not to exceed 12 years engine time in service), or whenever the camshaft gear is accessible, whichever occurs first." If the FAA were to do what Continental is asking, any engine built, rebuilt or overhauled prior to 2005 would have to be torn down immediately, and any newer engine would have to be torn down within 100 hours unless it can be shown that the new-style thicker gear is already installed. FAA may not buy into the 100-hour compliance requirement, but very well might go with the 12-year requirement (only a guess). Another school of thought is that the FAA may not have an appetite to take on such an expensive and controversial AD under the anti-regulation climate of the current Administration (but I wouldn't bet on it). For now, all we can do is wait for the other shoe to drop and see what the FAA's Notice of Proposed Rulemaking (NPRM) says. I urge every Continental owner whose engine(s) might be affected to keep a close eye out for the NPRM and reply to the rulemaking docket during the public comment period (which is usually only 30 days). Unless the FAA can make a compelling case for a genuinely unsafe condition (rather than a freak failure or two), I think the owner community should fight this AD tooth and nail. Maybe we'll get lucky and the FAA will decline to issue the AD that Continental is asking for. Or maybe the FAA will issue an AD that calls for camshaft gear replacement only at the next overhaul or teardown (with no 12-year or 100-hour limit). Otherwise, this could get extremely expensive for a lot of aircraft owners. Michael D. Busch A&P/IA CEO Savvy Aviation mike.busch@savvyaviation.com   https://www.savvyaviation.com 2008 National Aviation Technician of the Year

[aviatoreb]

I got that email too - if it were to come to pass - if ALL the conty 520 and 550 s needed to comply within 100 hours - that would overwhelm the engine shops and the production abilities of parts and the GA fleet would be disabled for a few years waiting in queue for mechanic time at an engine shop.

i doubt this will come to pass but thank you Busch for sounding the alarm.

[Simon]

I just got the same email and as someone who's currently looking at buying one of two different M20S Eagles this definitely gives me some pause.

It seems like I would be better off waiting until a decision is made on this one...and thank goodness for Savvy.
They just did a managed pre-buy on a 1982 M20J that was FULL of corrosion.  The estimated repairs on that plane ran from $50 - $70k.

I cannot say enough good things about them.  When I eventually find the right Mooney they will managing the maintenance no question.

 

 

[carusoam]

See other threads. For more input...

 

looks like a third thread... here..

Looks like it could be limited to a small number of bad gears.

The ability to trace the gears through the system is going to be tested.

1) Earlier IO550s have a less robust gear.  

2) The next set of IO550s got a more robust gear but needed a clearance space machined into the gear.

3) The most recent IO550s got the robust gear and the clearance machined in.

4) It seams like the #2) group is the high risk group.

5) To tell what cam gear you got, it should be available from the engine build sheet. Or any logged maintenance on it.

6) to skip the paperwork and go right to the looking at the gear will work. 

7) the procedure for this must be somewhere in the MMs...

8) If you are looking at the cam gear and you don't see a machined clearance mark, you may have the less robust gear which is a smaller problem than the thicker gear with no clearance mark.

9) Fortunately TCM is indicating they changed the part# to identify these variations of the part design.

10) Good luck with your search, hopefully it is just a paper exercise.

11) the Savvy guys have done a nice job of adding photos to the MSB.  The missing teeth of the cam gear is pretty telling.  

PP ideas only.

Best regards,

-a-

Edited April 5, 2017 by carusoam

[Yetti]

I wonder if this is why the Cirrus's have been falling out of the sky recently

[flight2000]

Want a fun read, go to Beechtalk where it is up over 17 pages of discussion already.... 

https://www.beechtalk.com/forums/viewtopic.php?f=37&t=136515

Full MSB is here:  http://www.tcmlink.com/pdf2/MSB05-8B.pdf

Bottom line, if this becomes an AD, anyone with an engine that does not have P/N 656818 will need to split their case and change the gear on the engine if written as the MSB currently shows.  Most estimates I've seen are somewhere between $9-$11K.  The new gear is $1,200.   

I just find it really funny that the revised SB comes out 12 years after the original one was published.

The alphabet organizations are already working on it, at least ABS and AOPA are that I know of for sure.

AOPA article on the issue written back in December:

https://www.aopa.org/news-and-media/all-news/2016/december/20/camshaft-gear-failures-generate-airworthiness-concern-sheet

Cheers,
Brian

II

[kortopates]

Maybe a little good news on this should the FAA go nuclear and adopt a rule requiring the new gear before overhaul as TCM advises. It is possible to replace the camshaft gear in situ without splitting the case. The engine still needs to come out with enough removal of things to drop the oil pan to give access to the gear. The rub is with the permamold cases that require just a little machining of about .060" of material that will interfere with the new gear. Continental wants the case split and a specialty shop like DIVCO to machine it. But someone is already producing a jig to position a grinder to accurately remove the very little metal that needs to come off. It's in a very small area. If this method is approved then the sting of replacing the camshaft gear can be tremendously lessened since it won't require splitting the case and R&R cylinders. Therefore far less invasive and requiring far fewer replacement parts - if approved.


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[DonMuncy]

2 minutes ago, kortopates said:

Maybe a little good news on this should the FAA go nuclear and adopt a rule requiring the new gear before overhaul as TCM advises. It is possible to replace the camshaft gear in situ without splitting the case. The engine still needs to come out with enough removal of things to drop the oil pan to give access to the gear. The rub is with the permamold cases that require just a little machining of about .060" of material that will interfere with the new gear. Continental wants the case split and a specialty shop like DIVCO to machine it. But someone is already producing a jig to position a grinder to accurately remove the very little metal that needs to come off. It's in a very small area. If this method is approved then the sting of replacing the camshaft gear can be tremendously lessened since it won't require splitting the case and R&R cylinders. Therefore far less invasive and requiring far fewer replacement parts - if approved.


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That makes too much sense for the FAA to adopt it.

[co2bruce]

Spoke to some engine rebuilders yesterday in Lakeland and they said there have been 2 failures (broken teeth) on these gears and both followed starter adapter failures. In all his rebuilds he has never seen a problem with this gear.

[MB65E]

I think Maintenance induced failures will far exceed the gear issue if the AD becomes active. (If cases are split)

-Matt

[flight2000]

4 minutes ago, MB65E said:

I think Maintenance induced failures will far exceed the gear issue if the AD becomes active. (If cases are split)

-Matt

Yep, agree with that 100%.

Brian

[Simon]

To clear up my own confusion about this MSB I called Continental Teledyne directly.  They must be getting a ton of calls

from worried owners because the the guy I spoke to knew what I was calling about without even telling him.  So my

new understanding is that this is absolutely mandatory.  From the original email from Savvy it seemed like there

was some question whether this would be enforced by the FAA, however I was told that the FAA has already instructed

Continental to make this mandatory.

The original date of the SB was 2005 so any engine could have had this work performed voluntarily between then

and now.  For all other engines it must be done according to the rules of the SB (12 years/ 100 hours).

Both Eagles I am looking at would need this work.  Perhaps the reason they are for sale?  Who knows.

 

I attach MSB05-8B.

MSB05-8B.pdf

[gsengle]

Mandatory SBs are not mandatory for part 91 aircraft.


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[Simon]

I didn't see anything about that distinction...however I'm pretty new at all of this

[DonMuncy]

If you are part 91 (like virtually all of us), unless it is an AD from the FAA, we don't have to do it. No matter how "mandatory" a factory tells us it is, we still are not bound by it.

[Simon]

34 minutes ago, DonMuncy said:

If you are part 91 (like virtually all of us), unless it is an AD from the FAA, we don't have to do it. No matter how "mandatory" a factory tells us it is, we still are not bound by it.

Continental made it sound like the FAA had already instructed them to made it mandatory - so I understood that to mean it was mandatory across the board (ie an AD)

Probably my mistake with interpreting the word "mandatory".

I'm beginning to understand all of this now...

[flight2000]

Response from the American Bonanza Society:

https://www.bonanza.org/community/member-forum/maintenance/posts/apr-2017/continental-motors-revises-camshaft-gear-guidance/

I wasn't logged into the website when I opened it, so it should be available to all.  Let me know if it's not and I'll find another solution.

Cheers,

Brian

[Guest]

On April 7, 2017 at 9:16 PM, kortopates said:

Maybe a little good news on this should the FAA go nuclear and adopt a rule requiring the new gear before overhaul as TCM advises. It is possible to replace the camshaft gear in situ without splitting the case. The engine still needs to come out with enough removal of things to drop the oil pan to give access to the gear. The rub is with the permamold cases that require just a little machining of about .060" of material that will interfere with the new gear. Continental wants the case split and a specialty shop like DIVCO to machine it. But someone is already producing a jig to position a grinder to accurately remove the very little metal that needs to come off. It's in a very small area. If this method is approved then the sting of replacing the camshaft gear can be tremendously lessened since it won't require splitting the case and R&R cylinders. Therefore far less invasive and requiring far fewer replacement parts - if approved.


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What would stop Superior from making their own copy of the gear with an SL prefix, then installing it would be a fix to the SB/AD as the part number would be different than the CMI part in question?

Clarence

[kortopates]

1 hour ago, M20Doc said:

What would stop Superior from making their own copy of the gear with an SL prefix, then installing it would be a fix to the SB/AD as the part number would be different than the CMI part in question?

Clarence

If I understand your point Clarence, let say Superior did get FAA PMA approval to manufacture their version of 656818, which they provide as SA656818. If so why would any of the documentation cited in the MSB or forthcoming AD need to be updated since under the PMA, the Superior p/n SA656818 could be used to substitute for the OEM required p/n 656818; just like SA parts can be used to substitute for any of the required CMI replacement part numbers at major overhaul as specified now in Appendix C of M-0. In the FAA eyes they are interchangeable. Am i missing something?

Edited April 11, 2017 by kortopates

[Guest]

26 minutes ago, kortopates said:

If I understand your point Clarence, let say Superior did get FAA PMA approval to manufacture their version of 656818, which they provide as SA656818. If so why would any of the documentation cited in the MSB or forthcoming AD need to be updated since under the PMA, the Superior p/n SA656818 could be used to substitute for the OEM required p/n 656818; just like SA parts can be used to substitute for any of the required CMI replacement part numbers at major overhaul as specified now in Appendix C of M-0. In the FAA eyes they are interchangeable. Am i missing something?

Hi Paul,

That's it exactly, the Superior part bearing a different part number would not be subject to the requirements of the s/b.  An AMOC via a PMA, applicable if it becomes an AD.

Clarence

[carusoam]

CMI has several part numbers that are fitting that gear at the end of the camshaft.

It is important to know which one is in the engine you are about to acquire, or have...

A paper search should be all it takes. To know if you have a part with the machined surface on it or not.

There is a particular time in history that engines received the 'bad' part number.  The new part was designed with a machined surface and a new part number was given for this modernized part.

If you are buying a plane with this engine, you want to know that it has the new part. The serial number of the engine should be all it takes to search what parts it has.  If an OH was done, the part number should be listed with the engine records.

When buying a plane a PPI is used to check for all the ADs and compliance that the aircraft has.  Know how to get a proper PPI.  

If a paper search doesn't work. Visually inspecting the gear seems to be the next step. Having to change the gear looks pretty challenging after that.

The newer the engine, the better chances of having the newer cam gear will be. Calling CMI with the serial number in hand is the best way to find out what partnumber is on the gear that is in the engine.  Unless it has been overhauled by somebody other than CMI...

PP thoughts on this, not a mechanic.

Best regrads,

-a-

Edited April 12, 2017 by carusoam

[gsengle]

The article I read implied there aren't good records for this part. Not sure how that could be. :/


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[mike_elliott]

On 4/8/2017 at 11:25 AM, co2bruce said:

Spoke to some engine rebuilders yesterday in Lakeland and they said there have been 2 failures (broken teeth) on these gears and both followed starter adapter failures. In all his rebuilds he has never seen a problem with this gear.

It does smell of fixing an effect and not a cause

[triple8s]

I dont understand why the cases have to be split to change a cam gear or machine the 60ths off the back of the case. A jig could easily be made to do the milling if acc. case was removed, of course I'm only an old truck mechanic.

[kortopates]

Mike had a 1 hour call with the FAA on this topic with some other stake holders representatives. He's going to be issuing an another e-blast update over the weekend. Although nothing has been resolved yet and it doesn't look like we'll see the FAA do so till May, but right now I think Mike was relieved and happy to see the FAA's attitude on this. Mike will share the details very soon.