When does an engine needs an overhaul? There are several indications that the engine is comming to the end of its life. But what do people really look for to decide an engine is to go to overhaul.
Low oil pressure, High oil temperature, Low cylinder compression, Loss of power. Which is the factor that maters most. For example low cylinder compression can easily be fixed replacing the cylinder not necessarilly an overhaul.
Of course I am talking about part 91 operation. I have heard people that run engines 1000 hrs and far more than ten years past TBO.
For those of you who decided to overhaul your engine. What made you spend the big buck?
When does an engine needs an overhaul?
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zero.one.victor
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GAHorn
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Wow. What a subject froth with pitfalls!
Here's the deal.
An engine mfr makes an engine, and predicts it's life based upon it's design and materials. After it's been in the field a few years, improvements and operating experience allows the mfr to increase the expected TBO. Eventually, it's pretty well known at what term of operation it no longer meets it's performance and/or it's design life (which offers certain guarantees with regard to safety, reliability, and economy.)
As a measure of some of these parameters certain tests are devised such as compression tests.
Under the best of circustances the engines are operated regularly, correctly, with the proper materials and within the proper limitations, and the engine gets all the way to TBO. (Originally 600 hours with our C145/O300's, extended finally to 1800 hrs.) When that engine gets to that point without any failures whatsoever,...it is said to be ready for overhaul by actual measure and by design.
Now when those engines, either by happenchance or by improper or infrequent operation or by other reasons, becomes unairworthy due to a worn-out or damaged part, then a repair scheme is allowed to bring the engine back into compliance with it's design for the purpose of continuing towards TBO. Typically, most of the fleet is made up of engines with part-time parts incorporated within them at some point short of TBO. Those parts may not be worn out, but the rest of that engine has reached the limit of economical overhaul by that time.
The private owner may wish to extend his luck quite legally if he wants, but he's very much out there on his own with regard to the design of that engine. Yes, I know. There are fudge-factors built into the safety equation here, and our personal safety is our own responsibility. But the question was: "When does an engine need an overhaul?"
Answer: If your engine makes it to 1800 hours without major failure and without excessive oil consumption and rattling noises,....it's time to overhaul it. It has done it's designed job, and now it's time to rebuild it so it can do it again.
Do you legally have to? Of course not (under Pt 91). Neither do you have to overhaul an old wooden boat hull if it's not sinking before going out to sea, nor do you have to throw out the potato salad just because it's been sitting in the refrigerator for two weeks.
Reliable engines don't usually fail catastrophically on any given flight. They are more likely to do it many flights after their design lives are exceeded. But a less than catastrophic failure, even if no airframe or personal injuries are sustained, 100 miles from home is suddenly a lot more expensive than the planned rebuild at the shop of your choice that wants to keep your other repair business.
How about the "top overhaul"? There is no "one size fits all" situation, but when the 1800 hours is reached,...it's the lower end, ....the one without the simple compression tests and easily inspected mechanisms that are most in need of rebuild. A top overhaul, in my opinion, is for the purpose of getting the lower end to overhaul,...not to take it beyond.
But that's just the way I feel about my equipment and family and friends. It's not what anyone else has to do.
Here's the deal.
An engine mfr makes an engine, and predicts it's life based upon it's design and materials. After it's been in the field a few years, improvements and operating experience allows the mfr to increase the expected TBO. Eventually, it's pretty well known at what term of operation it no longer meets it's performance and/or it's design life (which offers certain guarantees with regard to safety, reliability, and economy.)
As a measure of some of these parameters certain tests are devised such as compression tests.
Under the best of circustances the engines are operated regularly, correctly, with the proper materials and within the proper limitations, and the engine gets all the way to TBO. (Originally 600 hours with our C145/O300's, extended finally to 1800 hrs.) When that engine gets to that point without any failures whatsoever,...it is said to be ready for overhaul by actual measure and by design.
Now when those engines, either by happenchance or by improper or infrequent operation or by other reasons, becomes unairworthy due to a worn-out or damaged part, then a repair scheme is allowed to bring the engine back into compliance with it's design for the purpose of continuing towards TBO. Typically, most of the fleet is made up of engines with part-time parts incorporated within them at some point short of TBO. Those parts may not be worn out, but the rest of that engine has reached the limit of economical overhaul by that time.
The private owner may wish to extend his luck quite legally if he wants, but he's very much out there on his own with regard to the design of that engine. Yes, I know. There are fudge-factors built into the safety equation here, and our personal safety is our own responsibility. But the question was: "When does an engine need an overhaul?"
Answer: If your engine makes it to 1800 hours without major failure and without excessive oil consumption and rattling noises,....it's time to overhaul it. It has done it's designed job, and now it's time to rebuild it so it can do it again.
Do you legally have to? Of course not (under Pt 91). Neither do you have to overhaul an old wooden boat hull if it's not sinking before going out to sea, nor do you have to throw out the potato salad just because it's been sitting in the refrigerator for two weeks.
Reliable engines don't usually fail catastrophically on any given flight. They are more likely to do it many flights after their design lives are exceeded. But a less than catastrophic failure, even if no airframe or personal injuries are sustained, 100 miles from home is suddenly a lot more expensive than the planned rebuild at the shop of your choice that wants to keep your other repair business.
How about the "top overhaul"? There is no "one size fits all" situation, but when the 1800 hours is reached,...it's the lower end, ....the one without the simple compression tests and easily inspected mechanisms that are most in need of rebuild. A top overhaul, in my opinion, is for the purpose of getting the lower end to overhaul,...not to take it beyond.
But that's just the way I feel about my equipment and family and friends. It's not what anyone else has to do.
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N2663V
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When does an engine needs an overhaul?
When does an engine need an overhaul?
In my case, there were multiple signs that the engine was worn out:
* Hard to start, especially when outside temps were below 40 F
* Fuel consumption was gradually increasing
* Oil consumption was nearing 3 hrs/quart
* Oil temps were gradually increasing
* Engine had approx. 850 smoh 18+ yrs ago.
* Last OH was done by local A/P VoTech school
The engine seemed to run and perform OK and it had passed its last annual OK, with all compressions 68 /80 or better.
On tear down, compression rings in two cylinders were broken and the oil screen was full of debris (had checked OK at annual 6 months previously) from one crank bearing in process of self destruction. Crank was beyond the -0.01" limits.
I did a complete OH with new cylinders, new crank, new pushrods, and new oil pump, in addition to new exhaust, alternator conversion, and new windshield. I am glad I did what I did when I did, and am pleased with the results.
Warren
In my case, there were multiple signs that the engine was worn out:
* Hard to start, especially when outside temps were below 40 F
* Fuel consumption was gradually increasing
* Oil consumption was nearing 3 hrs/quart
* Oil temps were gradually increasing
* Engine had approx. 850 smoh 18+ yrs ago.
* Last OH was done by local A/P VoTech school
The engine seemed to run and perform OK and it had passed its last annual OK, with all compressions 68 /80 or better.
On tear down, compression rings in two cylinders were broken and the oil screen was full of debris (had checked OK at annual 6 months previously) from one crank bearing in process of self destruction. Crank was beyond the -0.01" limits.
I did a complete OH with new cylinders, new crank, new pushrods, and new oil pump, in addition to new exhaust, alternator conversion, and new windshield. I am glad I did what I did when I did, and am pleased with the results.
Warren
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Tom Downey
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In part 91 operations the FARS do not require an operator to overhaul any engine
The only thing that dictates when an engine gets overhauled in part 91 is when the operator desides that they want to overhaul it, otherwise it can be repaired as often as required to return to service.
I know that you folks maintain your aircraft to a higher standard that that, but that is the bottom line, no overhaul is required in part 91.
But remember this regulation must be met to the letter.
§43.2 Records of overhaul and rebuilding.
(a) No person may describe in any required maintenance entry or form an aircraft, airframe, aircraft engine, propeller, appliance, or component part as being overhauled unless-
(1) Using methods, techniques, and practices acceptable to the Administrator, it has been disassembled, cleaned, inspected, repaired as necessary, and reassembled; and
(2) It has been tested in accordance with approved standards and technical data, or in accordance with current standards and technical data acceptable to the Administrator, which have been developed and documented by the holder of the type certificate, supplemental type certificate, or a material, part, process, or appliance approval under §21.305 of this chapter.
(b) No person may describe in any required maintenance entry or form an aircraft, airframe, aircraft engine, propeller, appliance, or component part as being rebuilt unless it has been disassembled, cleaned, inspected, repaired as necessary, reassembled, and tested to the same tolerances and limits as a new item, using either new parts or used parts that either conform to new part tolerances and limits or to approved oversized or undersized dimensions.
The only thing that dictates when an engine gets overhauled in part 91 is when the operator desides that they want to overhaul it, otherwise it can be repaired as often as required to return to service.
I know that you folks maintain your aircraft to a higher standard that that, but that is the bottom line, no overhaul is required in part 91.
But remember this regulation must be met to the letter.
§43.2 Records of overhaul and rebuilding.
(a) No person may describe in any required maintenance entry or form an aircraft, airframe, aircraft engine, propeller, appliance, or component part as being overhauled unless-
(1) Using methods, techniques, and practices acceptable to the Administrator, it has been disassembled, cleaned, inspected, repaired as necessary, and reassembled; and
(2) It has been tested in accordance with approved standards and technical data, or in accordance with current standards and technical data acceptable to the Administrator, which have been developed and documented by the holder of the type certificate, supplemental type certificate, or a material, part, process, or appliance approval under §21.305 of this chapter.
(b) No person may describe in any required maintenance entry or form an aircraft, airframe, aircraft engine, propeller, appliance, or component part as being rebuilt unless it has been disassembled, cleaned, inspected, repaired as necessary, reassembled, and tested to the same tolerances and limits as a new item, using either new parts or used parts that either conform to new part tolerances and limits or to approved oversized or undersized dimensions.
Tom Downey A&P-IA
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GAHorn
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I rather cavalierly used both "overhaul" and "rebuild" in my previous message, and Tom Downey has correctly pointed out the difference.
Thanks, Tom.
In short: An overhaul is a repair scheme to make an engine airworthy in accordance with the manufacturer's specifications for engines continuing in service with cumulative time. A rebuild is a repair scheme which returns an engine to "new" condition in accordance with the manufacturer's specifications. (And a remanufactured engine, which is no longer available from Continental on our C145/O300's, when performed by the manufacturer is a rebuild with a new, zero-timed log book.)
Thanks, Tom.
In short: An overhaul is a repair scheme to make an engine airworthy in accordance with the manufacturer's specifications for engines continuing in service with cumulative time. A rebuild is a repair scheme which returns an engine to "new" condition in accordance with the manufacturer's specifications. (And a remanufactured engine, which is no longer available from Continental on our C145/O300's, when performed by the manufacturer is a rebuild with a new, zero-timed log book.)
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Tom Downey
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Overhaul/rebuild terms have nothing to do with who can or cannot start a new "0" time log on a serial number engine.
Only the manufacturer can issue new log with "0" time sence new.
anyone can start a new log with continuing time.
your post refers to "new limits" and "service limits" Which can influence how long an engine will serve before requireing repairss
All engines are manufactuered to limits, new limits may be .002" but service limits may be .005" on the same part. An engine that is overhauled to service limits may require no new parts to be considered overhauled IAW FAR 43. Yet the same engine overhauled to new limits may require ALL new parts to be considered overhauled IAW FAR 43.
The sign off in the log is the same. the only sure method of knowing what was done and what was replaced, is to read the work order of the facility that did the work.
The normal sign off in the log should be
"this engine meets. FAR 43.2 for "0" time since overhaul, at XXXX hours total time, see work order #XXXX at this facility for details."
That is the only entry that should be written, any time you see a "What was done entry" The mechanic is sticking thier butts out for some civil lawryer.
Only the manufacturer can issue new log with "0" time sence new.
anyone can start a new log with continuing time.
your post refers to "new limits" and "service limits" Which can influence how long an engine will serve before requireing repairss
All engines are manufactuered to limits, new limits may be .002" but service limits may be .005" on the same part. An engine that is overhauled to service limits may require no new parts to be considered overhauled IAW FAR 43. Yet the same engine overhauled to new limits may require ALL new parts to be considered overhauled IAW FAR 43.
The sign off in the log is the same. the only sure method of knowing what was done and what was replaced, is to read the work order of the facility that did the work.
The normal sign off in the log should be
"this engine meets. FAR 43.2 for "0" time since overhaul, at XXXX hours total time, see work order #XXXX at this facility for details."
That is the only entry that should be written, any time you see a "What was done entry" The mechanic is sticking thier butts out for some civil lawryer.
Tom Downey A&P-IA
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funseventy
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Warren,
I've been talking about the decision on whether or not I should top or major my engine lately. But now you have me concerned. I have a new windshield in my airplane now, but if I overhaul the engine without installing a new windshield can I still call it "0" SMOH?
Sorry Warren, they were getting to serious and I used you to lighten it up a bit.
There are tons of things to mention on this topic, like you cannot fing the terms Top Overhaul in the FAR's. But I didn't think it was worthy of mention along with other items that go along those lines.
My engine has 750 hrs on it and I think it is time for overhaul. It has 28+ years on it and I live in the mountains. If you find yourself thinking about it often, then it is time to Overhaul IT!
Kelly
I've been talking about the decision on whether or not I should top or major my engine lately. But now you have me concerned. I have a new windshield in my airplane now, but if I overhaul the engine without installing a new windshield can I still call it "0" SMOH?
Sorry Warren, they were getting to serious and I used you to lighten it up a bit.
There are tons of things to mention on this topic, like you cannot fing the terms Top Overhaul in the FAR's. But I didn't think it was worthy of mention along with other items that go along those lines.
My engine has 750 hrs on it and I think it is time for overhaul. It has 28+ years on it and I live in the mountains. If you find yourself thinking about it often, then it is time to Overhaul IT!
Kelly
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Tom Downey
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""""you cannot find the terms Top Overhaul in the FAR's. But I didn't think it was worthy of mention along with other items that go along those lines. """"
Because there is no such thing.
what a top overhaul actually is, is a REPAIR to correct low compression, or high oil consumpsion.
there only 4 things that can be done to any aircraft, engine, or component.
repair, overhaul, modify, or rebuild. those terms have meaning, the other terms are just some ones opinion of what they thought was done.[/code]
Because there is no such thing.
what a top overhaul actually is, is a REPAIR to correct low compression, or high oil consumpsion.
there only 4 things that can be done to any aircraft, engine, or component.
repair, overhaul, modify, or rebuild. those terms have meaning, the other terms are just some ones opinion of what they thought was done.[/code]
Tom Downey A&P-IA
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barchiola
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what should I expect to spend for a quality overhaul?
Hi gang,
I've read the posts on determining when to do the overhaul and would like to know if anyone could estimate how much it would cost to do a Mattituck or Penn Yan quality overhaul.
Thanks,
Bart
I've read the posts on determining when to do the overhaul and would like to know if anyone could estimate how much it would cost to do a Mattituck or Penn Yan quality overhaul.
Thanks,
Bart
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GAHorn
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When I called Mattituck with that question they quoted me $20,995 for a "new limits" overhaul on an O-300A. When I asked them where they would obtain a "new limits" crankshaft, there was a long pause.....and they said, "Well, you'd have to guarantee your crankshaft would meet new limits or you'd have to pay extra for one."
When I repeated my question, "Where would Mattituck obtain a "new limits" crankshaft for an O-300A"....they didn't seem to know. (So clearly they can't be counted on to perform a "new limits" overhaul.) They did however say that O-300D crankshafts could be obtained in "new limits" condition. So I asked them how much they'd charge to overhaul my O-300C engine to new limits.....and they wouldn't quote it stating they didn't know what a C engine was. (The ONLY difference between a C and an A is that the C uses the same crankshaft as the D which has only 6 prop bolts.)
In other words, I have made the decision that Mattituck will not do any of my engine work,...at least until they know a little bit more about 1) quoting overhauls 2) definitions of "new" vs "service" limits and 3) more about the Continental engines they supposedly service as a TCM subsidiary. If I were to be willing to ship my engine off somewhere for an overhaul I'd certainly consider shipping it to Tom Downey. Otherwise I'd find a qualified, locally-observable shop to do the work, which would also be more convenient in case of unexpected difficulties.
When I repeated my question, "Where would Mattituck obtain a "new limits" crankshaft for an O-300A"....they didn't seem to know. (So clearly they can't be counted on to perform a "new limits" overhaul.) They did however say that O-300D crankshafts could be obtained in "new limits" condition. So I asked them how much they'd charge to overhaul my O-300C engine to new limits.....and they wouldn't quote it stating they didn't know what a C engine was. (The ONLY difference between a C and an A is that the C uses the same crankshaft as the D which has only 6 prop bolts.)
In other words, I have made the decision that Mattituck will not do any of my engine work,...at least until they know a little bit more about 1) quoting overhauls 2) definitions of "new" vs "service" limits and 3) more about the Continental engines they supposedly service as a TCM subsidiary. If I were to be willing to ship my engine off somewhere for an overhaul I'd certainly consider shipping it to Tom Downey. Otherwise I'd find a qualified, locally-observable shop to do the work, which would also be more convenient in case of unexpected difficulties.
Last edited by GAHorn on Tue Aug 19, 2003 10:48 pm, edited 1 time in total.
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Bruce Fenstermacher
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That's interesting George. Up here in the North East Mattituck is highly regarded. I had a good experiance with them and a Lycoming engine which I think they have just a bit more expertise with. That is until they where bought buy Continential. You did know they are owned by TCM didn't you.
CAUTION - My forum posts may be worth what you paid for them!
Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
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GAHorn
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The fact that they were owned by TCM and didn't know about O-300 engines was exactly my point. I was very disappointed that the famous Mattituck didn't know the most basic differences on the engines they supposedly are expert at overhauling and don't have any idea where to obtain "new limit" Continental parts for the "new limits" overhauls they quote.
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N1478D
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The July 2003 issue of Aircraft Maintenance Technology has an article on this subject. It reinforces Tom's statements. It states that out of the 12 rules that apply to FAA certificate holders six address record keeping and the most important of these six is section 43.2.
It also discusses examples like a log entry error "overhaul the brakes" when all that was done was replace the brake pads. The word "replaced" should have been used.
The article suggests that the easiest way to remember when to use the term rebuild or overhaul is whether or not you used a micrometer or any other kind of specialized tool in order to make precise measurements. If you used a micrometer and recorded the dimensions, most likely you are either rebuilding or overhauling the part. If you just used hand tools, you are either repairing or replacing the part and it should be so noted in the logbook entry.
It also discusses examples like a log entry error "overhaul the brakes" when all that was done was replace the brake pads. The word "replaced" should have been used.
The article suggests that the easiest way to remember when to use the term rebuild or overhaul is whether or not you used a micrometer or any other kind of specialized tool in order to make precise measurements. If you used a micrometer and recorded the dimensions, most likely you are either rebuilding or overhauling the part. If you just used hand tools, you are either repairing or replacing the part and it should be so noted in the logbook entry.
Joe
51 C170A
Grand Prairie, TX
51 C170A
Grand Prairie, TX
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GAHorn
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That's why I put the term "top overhaul" in quotes, as if to say "what is referred to as a 'top overhaul'..."Tom Downey wrote:""""you cannot find the terms Top Overhaul in the FAR's. But I didn't think it was worthy of mention along with other items that go along those lines. """"
Because there is no such thing.
what a top overhaul actually is, is a REPAIR to correct low compression, or high oil consumpsion.
.[/code]
"What we have here is a failure to communicate." - Cool Hand Luke
One of the FAA's most recent headaches is that they've finally allowed owners to perform preventive maintenance,....but they've failed to teach them what constitutes preventive mx and how to make logbook entries. An excellent example of this is (as Joe just mentioned) when someone does a brake-job and even if they follow the exact techniques using genuine parts and the Cleveland Wheels and Brakes Technician's Service Guide (which will have them perform all the exacting definitions mentioned previously...." (1) it has been disassembled, cleaned, inspected, repaired as necessary, and reassembled; and (2) It has been tested in accordance with approved standards and technical data, or in accordance with current standards and technical data acceptable to the Administrator, which have been developed and documented by the holder of the type certificate, supplemental type certificate, or a material, part, process, or appliance approval under §21.305 of this chapter. "...
...the problem is that the Technicians Service Guide issued by Cleveland nowhere upon it has the magic words "FAA APPROVED". So it is not approved data and cannot be called an overhaul. It is a repair.
In my own aircraft logs, I don't even call it a repair. I called it "brake inspection and brake linings replaced with new linings, Cleveland PN's 066-00105"....and then I had my A&P SIGN IT OFF because brake repairs are not preventive maintenance and may not be performed by an owner/pilot except under the supervision of a licensed mechanic.
Another common error is the belief that owner/pilots can replace their ELT batteries. Appdx A (FAR 43) isn't especially pointed about the meaning of item 24 "Replacing and servicing batteries" but the FSDO's are pretty universal in their position that it is only the main aircraft battery that is approved for being replaced/serviced,...not appliance/avionics batteries. (Now don't someone start in on flashlight batteries! Flashlights are not installed equipment.)
Anyway, it's a subject for consideration.
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