To overhaul or not, that is the question...

[Guest]

When does infant mortality end?  A number of months, years or hours?  I know of a 1300 hour IO360 which had a new Superior crankshaft which snapped in two through a main crank journal.  Luckily they pilot made it to an airport

No engine is bullet proof, new, old or in the middle, when they quit calling AAA is not an option.

Clarence

Edited November 7, 2017 by M20Doc

[jetdriven]

2 hours ago, gsxrpilot said:

Well since I was responding to "this" discussion and not making a general statement about airplanes that quit making power, I still stand by my statement. 

The context here is whether an overhaul would prevent the failure of the engine. And while running out of gas might be just as disastrous as blowing a cylinder off from the perspective of the poor guy in the left seat, it wouldn't apply for this discussion as there's nothing about an engine overhaul that would have prevented that "engine failure."

There are plenty of examples of freshly overhauled engines that have failed as well. And it's also very unlikely that Lycoming or Continentals TBO calculations assume the best of modern engine monitoring, oil analysis, or borescope technology either. 

Everyone is entitled to their opinion on this topic and I don't think any opinions are wrong. All I was stating, and I still believe that with PROPER usage of a modern engine monitor with data logging, and with regular oil analysis, and with regular borescoping of valves, an engine such as this that has been running problem free for a thousand hours, will not just suddenly fail but rather will give advance indications. So without any regard for cost and only thinking of safety, I would continue to run the engine until it shows signs of failure.

I tend to agree except for the 7/16” valves that tend to snap off after 1300-1500-1800 hours. You can’t predict that. It does happen. It’s happened to 3 people I know. 

[Aviationinfo]

3 hours ago, M20Doc said:

When does infant mortality end?  A number of months, years or hours?  I know of a 1300 hour IO360 which had a new Superior crankshaft which snapped in two through a main crank journal.  Luckily they pilot made it to an airport

No engine is bullet proof, new, old or in the middle, when they quit calling AAA is not an option.

Clarence

I believe Busch says it's a few hundred hours, although there are always exceptions.  

[ArtVandelay]

Speaking of risk, don’t know your experience level, but doing a field overhaul seems risky to me. When the time comes for me, I’m sending it to a well know shop with long history of quality. Are you expecting to save a lot of money vs sending it to a well known shop?

[Raptor05121]

1 hour ago, teejayevans said:

Speaking of risk, don’t know your experience level, but doing a field overhaul seems risky to me. When the time comes for me, I’m sending it to a well know shop with long history of quality. Are you expecting to save a lot of money vs sending it to a well known shop?

Correct me if I'm wrong, but unless its sent to directly Lycoming, even that "well known shop" is still legally called a field overhaul...

[Bob_Belville]

11 minutes ago, Raptor05121 said:

Correct me if I'm wrong, but unless its sent to directly Lycoming, even that "well known shop" is still legally called a field overhaul...

Someone will answer more definitively but I suppose a "field overhaul" is descriptive of an overhaul done by an A&P and not by a certified "Repair Station".

 

[RobertGary1]

15 hours ago, M20Doc said:

When does infant mortality end?  A number of months, years or hours?  I know of a 1300 hour IO360 which had a new Superior crankshaft which snapped in two through a main crank journal.  Luckily they pilot made it to an airport

No engine is bullet proof, new, old or in the middle, when they quit calling AAA is not an option.

Clarence

My factory new IO-360 had 1000 SFEW when the piston end cap came apart. It was out of warranty but Lycoming did give me a break on the core (since mine had almost no core value afterwards).

-Robert

[RobertGary1]

42 minutes ago, Bob_Belville said:

Someone will answer more definitively but I suppose a "field overhaul" is descriptive of an overhaul done by an A&P and not by a certified "Repair Station".

 

Is "field overhaul" a term? I thought it was just either an "Overhaul" or "Re-manufactured". Only Lycoming can do the latter with 0 time logs.

 

-Robert

[mike_elliott]

15 hours ago, M20Doc said:

When does infant mortality end?  A number of months, years or hours?  I know of a 1300 hour IO360 which had a new Superior crankshaft which snapped in two through a main crank journal.  Luckily they pilot made it to an airport

No engine is bullet proof, new, old or in the middle, when they quit calling AAA is not an option.

Clarence

BUT calling Clarence is

 

[ArtVandelay]

11 minutes ago, RobertGary1 said:

Is "field overhaul" a term? I thought it was just either an "Overhaul" or "Re-manufactured". Only Lycoming can do the latter with 0 time logs.

 

-Robert

I don’t know official definition, I thought of a FO the way Bob described it. 

[Marcopolo]

FWIW,

 

Lycoming Factory Overhauls are built to (within) service limits and are time-continued engines in the logbook.

Lycoming Zero-Time Rebuilts must meet new drawing specifications.
Since Lycoming designed and built your original engine, only Lycoming has the ability to rebuild this engine to “new-quality” specifications and tolerances. Any reused part used on a Zero-Time Rebuilt must also meet new part specifications.

 http://www.lycoming.com/support/tips-advice/key-reprints/pdfs/Key FAQ.pdf 
 

[DonMuncy]

15 hours ago, M20Doc said:

When does infant mortality end?  A number of months, years or hours?  

I don't have the information readily at hand, but (if memory serves) Mike Busch's webinars have graphs showing engine failures vs time. Ordinarily, one would intuitively think that such a graph would show that failures would be almost nil in the first hour and would perhaps climb slowly until some number similar to TBO, and then climb rapidly. Instead his numbers showed a relatively high failure rate at the start, then a fairly steep slope down to a low level. Then that rate stays relatively stable for a long time. There seems not to be a lot of data for numbers well past TBO, presumably because most owners don't allow them to go that long before a preemptive overhaul. 

[RobertGary1]

Legally an overhaul by a shad tree A&P must meet the same specs as any of the big overhaul shops In truth few A&P's have the equipment to do the overhaul themselves so it just means they disassemble, send everything out and reassemble.

 

-Robert

[ArtVandelay]

7 minutes ago, RobertGary1 said:

Legally an overhaul by a shad tree A&P must meet the same specs as any of the big overhaul shops In truth few A&P's have the equipment to do the overhaul themselves so it just means they disassemble, send everything out and reassemble.

 

-Robert

But they have to go through all the SBs to figure out what applies based on model, year, etc.  I’m betting the overhaul manual is out of date the moment it’s printed.

Sort of like asking a nurse to be your surgeon...they know the basics, but I want the surgeon and the experience that comes with being one.

 

[cliffy]

7 minutes ago, Marcopolo said:

Lycoming Zero-Time Rebuilts must meet new drawing specifications.
Since Lycoming designed and built your original engine, only Lycoming has the ability to rebuild this engine to “new-quality” specifications and tolerances. Any reused part used on a Zero-Time Rebuilt must also meet new part specifications.

This is a little misleading. The terms "rebuild" and "overhaul" have different meanings.

There are two different ways to "overhaul" and engine- new parts tolerances or "service limits" tolerances. Either can be done by anyone with an A&P or a certified engine shop.

A "rebuilt" engine can only be supplied by the manufacturer or their designee after the manufacturer has "rebuilt" it using new parts or used parts meeting new part standards in fits and quality and including all the pertinent Service Bulletins and ADs applicable to that engine. With this the manufacturer can issue a new "ZERO" time log book as if the engine never had a previous history. In other words, it's essentially the same as brand new.

With a service limit overhaul parts can be worn to a certain "limit" and be reused in the overhaul and still supposedly provide a full TBO run according to Lycoming or Continental.

In a new limits overhaul (which anyone can do ) everything is measured just as in a service limits rebuild but only those parts meeting "new part" sizes will be reused. All other parts are bought "new" with new limit sizes. 

Anyone can field overhaul to "new" limit fits and sizes just like the manufacturer but only the manufacturer  can call it a "ZERO" time engine  and give it a new log book. All field overhauls to new limits get the old log book with TT and TSO recordings.

Here is a AC 43-11    that goes into detail about the definitions.    http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/248e88f9cbd60f9f862572b100634598/$FILE/AC 43-11_CHG1.pdf

 

[cliffy]

20 hours ago, N601RX said:

I had a friend who is an IA help me overhaul my engine a few years ago. A few months later we overhauled his engine as well as another mutual friends engine. All three of them turned out well. In addition to the stuff Cliff mentioned above the other big miss is the lycoming overhaul manual. It is lacking and rather than update it lycoming releases service bulletins and instructions . The only way to get all of these is to buy a subscription to them. There are several hundred of them and you will spend a lot of time looking through them deciding which ones apply to your engine and organize them in a sequence that follows your assembly order. During assembly you will have to repeatly go back and fourth between the overhaul manual and sb/si. Sometimes the manual will tell you to look at a particular sb, other times it does not like they just expect you to know that one exist. Also if you are using pma parts they may have their own sb which may or may not be the same as the Lycoming ones. 

YES and the stack of S/Bs to go through is tall. Lycoming doesn't make it easy to decipher which ones apply to your engine It would be very easy for them to do a spread sheet searchable by model number but they didn't when I needed it. Search for applicable S/Bs and purchase on line BUT NO you have to by all the S/Bs from day one for all engines.

I think they use the S/Bs as a profit angle rather than a safety service on their product. 

BTW, the overhaul manual IS very old in printing date and you MUST refer to the S/Bs for the most up to date information for each engine. 

This is why I said the outcome depends on how much effort you put in to the details. There are good overhauls and poor overhauls. Good ones can be done in the field if the effort to do it right is put forth. 

Details, details, details. 

[RobertGary1]

I think that is understood. The point is just that the term "re-manufactured" means it was done by Lycoming to new specifications. An A&P that overhauls to new specifications is still producing an "overhauled" engine. There does not appear to be any definition to the term "field overhaul".

-Robert

[DXB]

I've always wondered why the Lycoming 2000 hr TBO gets so much more attention in terms of maintenance and aircraft valuation than their 12 year guideline.  Clearly both the time and years guidelines are too stringent from an owner perspective, where the risks associated with infant mortality outweigh those of continued operation beyond  these very conservative numbers.  The debate is merely where the tipping point lies between continued operation risk and infant mortality risk,  and there might be insufficient data from really old engines answer it adequately.  But clearly at some point age would have to become the dominant consideration, as OP of this thread implicitly acknowledges by his decision to overhaul.  

[cliffy]

"RE-manufactured" has NO defined meaning in the FAA lexicon as stated in AC 43-11.

"Re-built" does. Only the manufacturer can use the the term "rebuilt" and that comes with a new log book. Anything else, by anyone else, is an "overhaul" by definition. The term "field" overhaul has only common usage definition, not legal definition. Some say any "overhaul" by anyone other than the manufacturer is a "field overhaul".  

The only term  (singular) defined in the FARs is  "rebuilt" in 91.421 and that allows an "operator" to use a NEW log book on an engine "rebuilt" by the manufacturer. 

Again, this is all contained in the AC 43-11 that I attached to my previous post. 

[RobertGary1]

I think we've somehow devolved down a road of terminology that wasn't intended or ever disputed rather than addressing the question

-Robert

[Raptor05121]

To answer OP:

No

[Guest]

The factory gets to “Zero” the log book because they have no idea of the time on the jumble of parts they assemble and sell.

You're better off with an engine done by a conscientious builder in many cases, regardless of what you want to call it.

Clarence

Edited November 8, 2017 by M20Doc

[jaylw314]

21 hours ago, M20Doc said:

The factory gets to “Zero” the log book because they have no idea of the time on the jumble of parts they assemble and sell.

You're better off with an engine done by a conscientious builder in many cases, regardless of what you want to call it.

Clarence

There is an advantage to rebuilds over overhauls.  Rebuilds are frankensteins, with various random parts from old engines that still meet limits (along with some new parts).  When you overhaul an engine, many parts that do not meet limits have to be ordered new.  Statistically, this means there is a higher percentage of old parts in rebuilds that have already survived infant mortality, unlike overhauls where there are a lot of new parts that are vulnerable to infant mortality.

[DonMuncy]

1 minute ago, jaylw314 said:

There is an advantage to rebuilds over overhauls.  Rebuilds are frankensteins, with various random parts from old engines that still meet limits (along with some new parts).  When you overhaul an engine, many parts that do not meet limits have to be ordered new.  Statistically, this means there is a higher percentage of old parts in rebuilds that have already survived infant mortality, unlike overhauls where there are a lot of new parts that are vulnerable to infant mortality.

Interesting thoughts. I had figured that infant mortality was due to assembly errors, rather than part failures. Obviously, failures can be because of either. I have never heard Mike Busch (or anyone else) differentiate between the two. It would be interesting to see numbers. Next time he has a webinar where the subject of infant mortality comes up, I will ask him if he has any numbers that show that.

[RobertGary1]

55 minutes ago, jaylw314 said:

There is an advantage to rebuilds over overhauls.  Rebuilds are frankensteins, with various random parts from old engines that still meet limits (along with some new parts).  When you overhaul an engine, many parts that do not meet limits have to be ordered new.  Statistically, this means there is a higher percentage of old parts in rebuilds that have already survived infant mortality, unlike overhauls where there are a lot of new parts that are vulnerable to infant mortality.

BTW: Lycoming disputes this. When I bought my engine they said that in actual fact the vast majority of parts are actually new, they claim to not use many preowned parts. I don't remember the rundown the guy actually gave me. The biggest benefit for me was the 2 year warranty. I ended up getting a new set of mags free as a result 16 months later because an SB came out on mine.

 

-Robert