I'm looking at an engine logbook that has 5 logbook pages of work that was done to the engine while the aircraft was completely restored. I'm wondering what the criteria is that would constitute a "top overhaul"?
What Constitutes a "Top Overhaul"?
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flyingmoose
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There is no set "criteria" for what is sometime called a top overhaul. Generally what that means is that they most likely changed all the cylinders/pistons with either new or overhauled jugs. The five pages of log entries will/should give you an understanding of what they actually did. But there is no standard really
Typically piston, cylinder, and pins.
poadeleted20
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There is no regulatory definition of the term, but FAA AC 43-11 defines "top overhaul" as follows:
Note that this is a "soft" definition of what it "can" be, not what it is. The only way to find out for sure what was/was not done in a "top overhaul" is to read the documentation in the logbook and/or work order for the job.
N747JB
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As a buyer or seller, I would consider a "top overhaul" to be replacing all the cylinders, pistons, and associated parts with new or overhauled parts. Replacing 3 out of 6 pistons and jugs, in my mind, wouldn't be a top.
MAKG1
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As a buyer or seller, I would consider a "top overhaul" to be replacing all the cylinders, pistons, and associated parts with new or overhauled parts. Replacing 3 out of 6 pistons and jugs, in my mind, wouldn't be a top.
Even if they are inspected and found in spec?
You're confusing an overhaul with a rebuild.
mchesney
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Would the "bottom" be the crank and bearings? If you had a "top" done, how would you know that it didn't need a bottom as well? and why is it so much more expensive getting the bottom done?
People use the word top overhaul very loosely when advertising a plane for sale . If your not sure what was done have a mechanic check the log for you. Also check total time since a major overhaul.
N747JB
Final Approach
No, when I read "top overhaul" I think it means all new or rebuilt cylinders, the OP was asking what constitutes a top overhaul and that is what I consider a top overhaul.
A top overhaul is sort of like a pre-buy inspection, a generic term that can cover a lot or a little, without a clear FAA definition. If they are inspected and found within spec, I wouldn't consider it a top overhaul, I would consider it within spec and make other mention of it in an ad. 
bnt83
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When will cylinders, that were sent out for repair/overhaul, come back marked as "inspected"?
Never.
weirdjim
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It actually by definition goes one step beyond that. If the engine has a test procedure in the maintenance manual that specifies that it be run for so long under thus and such conditions and measured for this and that, then that is part of the overhaul.
If that engine HAS that sort of folderol in the manual, then simply doing a thorough top on the engine (jugs, pistons, rings, valves, etc.) and giving it the old "five minutes on the ground without losing too much oil and then going and flying it for an hour or so" without doing the test procedure is called a "repair" and not an "overhaul".
Jim
MAKG1
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When will cylinders, that were sent out for repair/overhaul, come back marked as "inspected"?
Never.
Why would you need to send out a cylinder for inspection?
It's not like it's hard to inspect a cylinder. You need a bore diameter gauge (but it can be done with a $5 telescoping gauge), a set of micrometers, and a set of decent eyeballs. Valve margins can be tested for condition with ... a valve (and some Prussian Blue or even a viscous fluid like ATF or crankcase oil).
Any decent mechanic should be able to inspect an engine and all its parts as part of disassembly. Otherwise, he's wasting time and customer money on machine work and shipping that isn't necessary. And it's best practice to inspect things coming back from the machine shop as well. It would really suck for the engine to blow itself up the first time it's run up because a clearance was too big or a bearing oil hole wasn't lined up.
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docmirror
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All wear components in an engine are not created equal. The wear component in the engine with the shortest typical life is the exhaust valve, seat, and guide. It gets the worst punishment with hot gasses being pushed out constantly. OTOH, the center main crank bearing probably has the easiest life of any wear component in the engine.
Given this, it's pretty common on many aircraft engines to have the exh valve area get weak after 1000 or less hours, while the main and cam bearings will live > 3000 if taken care of well. This is often what leads to the 'top overhaul'. Also, for planes that don't run much, the rust starts on the cylinders more quickly than on the internal case components. A top overhaul or two is common before the bottom of the engine is wearing beyond any kind of limit.
Tom-D
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There is no FAR definition of a top overhaul. As there is for an engine overhaul, re-build, etc. Ron has shown us an AC which is the FAA's advise as to what it is, But you'll not find a list of parts that constitutes the term.
The term is usually used to describe the parts that can be removed from the engine with out disassembling the cases and crank assembly or the accessory section.
The term is usually used to describe the parts that can be removed from the engine with out disassembling the cases and crank assembly or the accessory section.
Tom-D
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When will cylinders, that were sent out for repair/overhaul, come back marked as "inspected"?
Never.
When they are inspected and found beyond repair.
bnt83
Final Approach
So your going to measure and "inspect" filthy dirty cylinder? You haven't even mentioned equipment needed to clean them yet.
Chances are at least one or more more cylinders will need work anyway. Why else would you be doing a TOH? Instead of blowing all that time on the jugs I would rather work other squawks while those are being worked somewhere else.
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bnt83
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I exchanged all my cylinders over the course of 13 months. 3 cylinders in one annual and 3 more in the next. Also Iran all accessories.
So over the course of about 73 hrs I did a TOP.
I put on cylinders with that nickel nitrate system to reduce rust from not flying weekly.
So over the course of about 73 hrs I did a TOP.
I put on cylinders with that nickel nitrate system to reduce rust from not flying weekly.
Tom-D
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Tony_Scarpelli
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Tom pardon me if I say you are full of **** again. 9 years ago you told me on AOPA forums that there is no such thing as an owner assisted annual(s). So I do not buy into "toms theory" of the way the world works.
NO! I did a top overhaul.... I don't really care what you call it Tom. This is the problem with mechanics and their mind games. They are full of crap.
I have six new cylinders, all new IRAN accessories and new plugs and some want to throw rocks so it completely diminished their credibility.
I will take Mike Busch and the experts in condition based maintenance for their expertise.
MAKG1
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The INSIDE?
The part you need to measure is generally really clean, as piston rings do that for you. If it isn't, something failed internally and a full teardown is called for. Whatever the crap is in there, it's in the oil pump and bearings. For the valves, if the seat is dirty, the valve is likely burned or distorted and you almost certainly need the valves and seats refaced.
Some inspections are really easy. If the cylinder is scored, it's bad. If the crosshatch is gone, it needs at least a hone, and most likely more.
You don't have to wash and blast a cylinder just to mic the bore, measure taper, diameter, out-of-round, etc. That's necessary when you start to get into machine work.
Tony_Scarpelli
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The engine builders around here use a commercial dish washer. Hot, Hot water.
I guess if I were doing to tear down my cylinder in the field I would do the same thing. Pickup a $50 used dish washer and turn the temps up and away you go. Might even put some degrease r in there.
I guess if I were doing to tear down my cylinder in the field I would do the same thing. Pickup a $50 used dish washer and turn the temps up and away you go. Might even put some degrease r in there.
bnt83
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Skipping the cleaning sounds like a poor top overhaul to me. Your gonna miss any cracking on the inside of the head, only obvious after blasting it.
docmirror
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The most important thing to inspect is the exh valve, guide and seat. This is far more true of the Conti big bore jugs than small bore, or Lyc.
Did you know that the exhaust port in an O-470 series jug is the same size as the O-200? If you don't believe me, grab an exhaust stack off an O-200 and fit it up to a O-470. Perfect match. Lots of heat and pressure there.
Did you know that the exhaust port in an O-470 series jug is the same size as the O-200? If you don't believe me, grab an exhaust stack off an O-200 and fit it up to a O-470. Perfect match. Lots of heat and pressure there.
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If you did a top overhaul, show me the FAA required nomenclature for that overhaul.
FAR 43.2 gives the required verbiage for signing off any overhaul. any thing else is a repair.
OBTW no one can assist in any required inspection. You can do all the work, but the inspection is the inspection and you as an owner can not participate. Otherwise the signoff would say we inspected this aircraft IOW _____ and found it to be in an airworthy condition.
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most use a strip tank and steam cleaner, inspect and then a soda blaster. any thing courser will remove too much metal.
txflyer
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I didn't know that.
What about the 0-470-50? The exhaust port I assume is larger which would explain a lot of the horsepower.
poadeleted20
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You can consider it anything you like, but there is nothing in the law which says what you consider it to be is what must be or have been done. Caveat emptor.As a buyer or seller, I would consider a "top overhaul" to be replacing all the cylinders, pistons, and associated parts with new or overhauled parts. Replacing 3 out of 6 pistons and jugs, in my mind, wouldn't be a top.
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poadeleted20
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If the engine is described as "overhauled," then everything in 43.2 including that must be done. If it is described as having had a "top overhaul", no such requirement exists.
poadeleted20
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Since there is no legal definition of what a "top overhaul" must include, nobody (including you) can say legally that what you did was or was not a "top overhaul". It remains a term without binding legal definition.
docmirror
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I didn't know that.
What about the 0-470-50? The exhaust port I assume is larger which would explain a lot of the horsepower.
I don't know what that is, so I can't help you.
I didn't know that.
What about the 0-470-50? The exhaust port I assume is larger which would explain a lot of the horsepower.
Not necessary to assume (I haven't measured and don't know they are or aren't the same size), it's not always advantageous to increase valve size. Flow quality is more important than quantity especially in these low rpm- low compression engines, you can easily lose power by increasing valve size and disturbing the scavenge flow and intake charge swirl.
N747JB
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I think we've already discussed that there is no legal definition of a top overhaul, that's why I said what I considered a top. Most folks that I know in the airplane business use that same definition. The term is used in advertising and like everything else, must be verified with the log books.
weirdjim
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weirdjim
I'll take Tom's A&P/IA over an MBA any day of the week and twice on Sunday.
Jim
Tim
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Its when the Rocker cover gaskets get changed.
Tom-D
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Exactly. !
the terms " owner assisted annual" and top overhaul are the two best misnomers I know of.
neither really exists.
poadeleted21
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Yep, some of the A&P types like splitting hairs on subjects that nobody else gives a **** about, including the FAA, your customers or anyone who looks at the log books in the future. I've also caught on that you defend each other violently.
Get Tom started on "Annual Inspections" vs "13 Month Maintenance Periods"
You guys could go on all day and giggle condescendingly about how your dumbass customers don't know the difference.
I guess it's the FAA brainwashing with inane regulations you go through at A&P school that causes it.
But, to take the bait.
I see nothing in FAR 43.2 that precludes Tony from saying "73 STOH" in his non-existant for sale ad.
poadeleted21
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