Hi BCP,

I've been lurking here and have been looking to purchase an aircraft, probably something with a small Continental C85, C90, O200. In my search I have found many with new cylinders or upgraded crankshafts... Let's not go down the C85 with O200 crank rabbit hole.

But what I can't quite figure out is how a Major overhaul is defined. An example, one aircraft had the Crankcase Replaced and the Crankshaft and Oil Pump reconditioned. Later on 3 of the 4 cylinders were replaced. My basic understanding of engines tells me it's almost been overhauled just not all at once. Am I missing something? When cylinder is replaced are the pistons reconditioned? New rings etc?

Thanks
M

The engine manufacturers have a service bulletin I believe that lists all the items that must be inspected, reconditioned to within specs, or replaced. The overhaul manual for a given engine series lists the required procedures for disassembly, inspection/service limits, and reassembly for everything.

Lycoming SB.

If someone tries to sell you an overhauled engine, ask for the stack of invoices and receipts that show the service and purchase of these items. Logbooks are an important part of an engine's provenance, but when it comes to a field overhaul (an overhaul done outside the scope of the manufacturer or authorized engine shop) the shopping list and service invoices is what would matter to me.

If there is mod like the O-200 crankshaft in a C-90, I believe that's an STC (I could be wrong) so make sure the logs have it.

I recently overhauled an IO-540 for an experimental, but I overhauled it as if it was certified, under the guidance of an A&P IA.

Thanks zzz, I figured there would be a list like that just couldn't find it.

FAR 43.2 defines overhaul. See the link below.

https://www.law.cornell.edu/cfr/text/14/43.2

The part of Overhauling to be aware of is that an item can be overhauled and use either New limits, or Service limits which are more generous. You would have to check the logs to determine which it is. Some of the skepticism that comes from buying an airplane with a field overhauled engine is that the items inside the engine may not be to new limits, but simply cleaned and reassembled with the list of required new parts to the service limits.

Zzz wrote:The engine manufacturers have a service bulletin I believe that lists all the items that must be inspected, reconditioned to within specs, or replaced. The overhaul manual for a given engine series lists the required procedures for disassembly, inspection/service limits, and reassembly for everything.

Lycoming SB.

I recently took a trip to a (respected and well known) engine overhaul shop to have some engine parts inspected during an overhaul I was doing on a Lycoming. I asked specifically about that SB and what they had to say about it and their answer kind of surprised me. They still do not replace with new all the parts on that list and rattled off a list of example items they just inspect and re-install. I thought to myself that "if its good enough for these guys, good enough for me" and promptly followed using common sense.

I'd also note a mandatory service bulletin is not mandatory legally speaking, unless there is an AD somewhere saying it is.

To call an engine Overhauled, you must perform the overhaul in accordance with the manufacturers guidelines. Why? Because this is the only data acceptable to the administrator for performing an overhaul on that engine. If there is other acceptable data that can be used to overhaul a motor, I'd love to see it.

And the overhaul manuals are very specific of what can and can not be re-used. There is no variance or exceptions in these rules. If you don't follow the manufacturer's data for overhauling a motor - It_is_not_an_overhaul.

Continental, for example. If you're not replacing the through bolts, bearings, every bushing, pistons - pins - rings, springs, keepers, rocker shafts ---- it's not an overhaul.
There are also requirements for connecting rod beam width, oil pump gears and all other such bits that will make an old motor overhaul expensive as hell but, they are required by the book.
Continental also states to be an overhaul, all accessories must be overhauled as well including the right angle starter adaptor which is an expensive piece of hardware.

As far as service bulletins, yes they are not mandatory unless:
1. they are listed as mandatory in the Overhaul manual - which you are required to comply with if you are overhauling. and,
2. you are overhauling the engine.
At which point, those Service Bulletins are not mandatory.

Anything less is a repair of the motor that does not reset the clock and to log it as an overhaul is fraud.

Yeah, mechanics will disassemble, clean, inspect, replace bearings, and call it an overhaul but, it's not.

I just went through this with an IO-360 that had a '400 SMOH' that was basically new bearings and a gasket kit. I spent Q4 of 2018 educating myself on overhauls and their associated costs to do it right.

Bagarre wrote:To call an engine Overhauled, you must perform the overhaul in accordance with the manufacturers guidelines. Why? Because this is the only data acceptable to the administrator for performing an overhaul on that engine. If there is other acceptable data that can be used to overhaul a motor, I'd love to see it.

And the overhaul manuals are very specific of what can and can not be re-used. There is no variance or exceptions in these rules. If you don't follow the manufacturer's data for overhauling a motor - It_is_not_an_overhaul.

Continental, for example. If you're not replacing the through bolts, bearings, every bushing, pistons - pins - rings, springs, keepers, rocker shafts ---- it's not an overhaul.
There are also requirements for connecting rod beam width, oil pump gears and all other such bits that will make an old motor overhaul expensive as hell but, they are required by the book.
Continental also states to be an overhaul, all accessories must be overhauled as well including the right angle starter adaptor which is an expensive piece of hardware.

As far as service bulletins, yes they are not mandatory unless:
1. they are listed as mandatory in the Overhaul manual - which you are required to comply with if you are overhauling. and,
2. you are overhauling the engine.
At which point, those Service Bulletins are not mandatory.

Anything less is a repair of the motor that does not reset the clock and to log it as an overhaul is fraud.

Yeah, mechanics will disassemble, clean, inspect, replace bearings, and call it an overhaul but, it's not.

I just went through this with an IO-360 that had a '400 SMOH' that was basically new bearings and a gasket kit. I spent Q4 of 2018 educating myself on overhauls and their associated costs to do it right.

Yep.

Bagarre wrote:To call an engine Overhauled, you must perform the overhaul in accordance with the manufacturers guidelines. Why? Because this is the only data acceptable to the administrator for performing an overhaul on that engine. If there is other acceptable data that can be used to overhaul a motor, I'd love to see it.

And the overhaul manuals are very specific of what can and can not be re-used. There is no variance or exceptions in these rules. If you don't follow the manufacturer's data for overhauling a motor - It_is_not_an_overhaul.

Continental, for example. If you're not replacing the through bolts, bearings, every bushing, pistons - pins - rings, springs, keepers, rocker shafts ---- it's not an overhaul.
There are also requirements for connecting rod beam width, oil pump gears and all other such bits that will make an old motor overhaul expensive as hell but, they are required by the book.
Continental also states to be an overhaul, all accessories must be overhauled as well including the right angle starter adaptor which is an expensive piece of hardware.

As far as service bulletins, yes they are not mandatory unless:
1. they are listed as mandatory in the Overhaul manual - which you are required to comply with if you are overhauling. and,
2. you are overhauling the engine.
At which point, those Service Bulletins are not mandatory.

Anything less is a repair of the motor that does not reset the clock and to log it as an overhaul is fraud.

Yeah, mechanics will disassemble, clean, inspect, replace bearings, and call it an overhaul but, it's not.

I just went through this with an IO-360 that had a '400 SMOH' that was basically new bearings and a gasket kit. I spent Q4 of 2018 educating myself on overhauls and their associated costs to do it right.

This is gospel...and there are quite a few “overhauls” out there that are really just repairs. It’s easy to spot though if you know what to look for in the engine records.

MRebel wrote:Hi BCP,
...
But what I can't quite figure out is how a Major overhaul is defined.
....
M

Recommend reading:
FAA Advisory Circular 43-11, Change 1, - Reciprocating Engine Overhaul Terminology and Standards
(https://www.faa.gov/regulations_policies/advisory_circulars/index.cfm/go/document.information/documentID/99858)
For some reason it’s currently behind the Federal Firewall so if using alternate source http://www.everyspec.com verify it is the 31-years-newer Change 1.