ekimneirbo
Well-Known Member
The intent of the original thread on using a Lyc or Continental in someones experimental
airplane is rather long and often drifted into either discussion of auto engine suitability or
comments about my knowledge of certified engines. This synopsis is hopefully ONLY
about these two aero engines and what you should consider when choosing to use one.
It is not intended to suggest that some other option is better, but only to point out the
positives and negatives so you choose wisely when considering an aero LyCont engine.
In the original thread my postings were met with a lot of discord, and even though I
specifically asked that any mistatements be corrected.....nothing factual was submitted.
It pretty much deteriorated into a pissing contest with a few factual comments now and
then. So here is what I feel is helpful and factual in a somewhat condensed version.
After posting this in its entireity, anyone can make any comment they wish...but the
meat of the information will be here in one semi-organized post. Who ever takes the
time to read it can decide for themselves if it has any worth to them.
LyConts have developed a great record for reliability when purchased new , maintained
and flown regularly.You MUST maintain and fly regularly to expect great reliability.
If you purchase a USED LyCont because it is easier to adapt to your airplane and you
feel the cost of initial purchase will be similar to or even less than the cost of some other
option...you may be right. Later I will point out some of the pitfalls that can occur after
the purchase, but for now the initial cost of purchase and installation is attractive.
No matter how the engine turns out, even if it is essentially perfect, you should think
about the following considerations.
1. These engines built their record of reliability by being maintained on at least a yearly
basis by professionally trained mechanics, adherence to ADs, and replacement of parts
when needed....per the inspections and ADs.
Your now Experimental engine will not be required to comply with these requirements
any longer. Common sense would tell you that if you wish for your engine to be as reliable
as when it was certified, you will still need a professional to inspect it, and you
probably need to comply with any ADs for the engine even though nether of these is
a LEGAL requirement. If you are competent and confident enough to do your own work,
then you can, but be honest with yourself about your abilities.
So, your easily installed and reasonably inexpensive purchase may need to have the
same expensive attention in order to stay reliable. Many builders have friends who are
APs and may recieve these services free or cheaply....many builders will have to pay.
Decide which scenario applies to you.
2. Will you be able to find a licensed AP who is willing to work on your engine and sign
off on the work now that the engine is installed in an experimental airplane? Remember
now that your airplane is now being possibly worked on by an uncertified individual(you)
and that if your airplane should fail for any reason, the FAA will be in contact with HIM.
So it is possible that finding mechanical help could prove difficult, especially on a long
flight.
3. If you expect to do all your own work on the LyCont, you will need to purchase
some special tools which are specific to LyConts along with service manuals to supplement
your knowledge. If you are handy with tools and mechanical things
you may be able to do your own work....but since your life may depend on how
well you do it, I would still suggest getting some knowledgeable assistance.
4.Those are specific considerations that should be viewed even if your engine is in
perfect condition when you buy it. If your engine turns out to be in less than perfect
condition, then you will need to make immediate monetary choices on how to proceed.
Talk to some APs and get a feel for the "what ifs" will cost if the engine you purchase
needs certain items replaced. Research if there are any ADs that apply to the type of
engine you wish to buy and then you can check for compliance before buying. If not,
you may need to purchase and install the parts even though not Legally required to.
Its a matter of safety not legality on an experimental airplane.
One of the comments made was that 99% of all experimentals will be powered by an
engine made specifically by an aero engine manufacturer. While thats probably some
where near the truth, the point of this thread is to make you aware of some of the issues
with the used engines that are available. While some may interpret that as pushing you
toward conversion engines, it can also be interpreted as pushing you toward a NEW
aero engine, or educating you about what you may get with a rebuilt engine. So its
really not pushing you anywhere....its just pointing out some facts.
[h=2]To aero engine or not to aero engine.......that is the question[/h]
When building an airplane one of the first questions a builder must consider is cost and type of engine. Now let me say right up front that choices will vary greatly with the type of airplane you wish to build. Small and smaller engines generally
are used in smaller,lighter,and slower flying airplanes. There are specialized exceptions. Then you move into the midsize area where choices begin to expand somewhat with water cooling and turbocharging sometimes being employed. Moving on up to engines above 350 cu inches........almost anything can be made to work if it produces plenty of power because you generally are using an airplane designed for the heavier engines. Nothing is always true,you have to use generalities until
you get specific about what airplane you want to build and what its purpose in flight will be. Fast,slow,crosscountry,STOL, single passenger, etc. Define what YOU want and then you can narrow down your choices. If you decide to go with a non-
traditional aero engine, there will be plenty of people to tell you why not. Its impossible to address auto conversions because the absolutes of conversion do not apply.I say this because each conversion has its own set of details to work out. Putting an VW or Corvair will not carry the same benefits or detriments that a water cooled V8 will entail. So, when discussing conversions, don't let the naysayers convince you that it can't be done. Oshkosh is full of success stories every year.
Back to the purpose of this thread........to aero engine or not
I'm sure that everything I say here will be construed negatively by believers in only using an aero engine, thats just the way things are. But, the things I say here will be my considered opinions and true as far as I know.
First, let me say that from its birth at the factory, most commonly used naturally aspirated aero engines are very reliable and expensive. There have been some notable exceptions and a few duds from the factories, but for the most part they are
pretty reliable.
Once the engines begin to work in the real world, used by ordinary imperfect human beings, many things can happen to them.
Each engine will come with a log book where every detail of its life and maintainance will be thoroughly documented. Don't believe that myth. While its a good selling point and gives the buyer a feel good moment....it really not reliable.
What can go wrong....everything from a dishonest seller to an honest omission.
"Well it was just a minor prop strike in grass, nothing to be concerned about. If I document it, the engine will need to be torn down for inspection and thats pretty expensive. Guess I'll just check the run out and if its ok, that'll be fine"
"Hmm noticed a little rust inside the crankshaft, but there is always some in these engines, probably nothing to worry about"
"Cylinder head temps seem a little high these days, but the engine runs fine....probably nothing to worry about."
"The oil sample showed a little metal in it but it was within specs, so I guess it doesn't need to be documented."
Lots of things go undocumented in the life of an engine. I remember one day many years ago walking along the grass at a local airfield and coming upon a member of the local club who had his Cessna 150 engine partially disassembled. Being new to the sport I didn't realize what was going on. I stopped to talk and he stressed the point that I should not mention to the AP/airfield owner what he was doing. Eventually the fellow was forced out of the aero club because of his continued attempts to circumvent proper mainataince and insurance for his airplane. He had a garage/hangar that backed up to the airfield. One day he landed his airplane
and rolled it in the hangar. Shortly thereafter the airfield owner placed a large dirt berm right next to his hangar door so the airplane could not be taken out again. About ten years later I bought the airplane and removed the wings and brought it home. After a while I decided it would be too expensive to repair the engine and sold the whole airplane to a dismantler.
Another time I worked on an engine that had been recently rebuilt by an AP and found that he didn't know the engine was supposed to have oil squirters in it.....and he was teaching me.
You have to remember that the fifties, sixties, and seventies were a totally different era from today. We didn't have computers everywhere. Information was not at our fingertips or even available. People had less disposable income and had to make do
with less than optimal conditions.A lot of todays engines were manufactured during that time and are still doing duty today.
You do not know what has transpired in the life of these engines no matter what log books say....and many engines don't even have a log book. Did you ever wonder why someone would lose the log book for an expensive engine?
Another thing, when aero engines do go bad all of the attendant parts are always salvaged and stored for some future use.
While rebuilding several engines, I was directed to a stack of connecting rods from salvage engines to replace one in the engine I was assembling. Although they all looked similar, I decided to employ an old racers trick and weighed the connecting rods. I couldn't believe how much difference I found in the weights. No wonder those engines vibrate.
My point is that its difficult to consider the myriad number of things that have happened in an engines life, or to believe that all of these things were properly documented by the thousands of different individuals who have been involved with them.
While I'm sure I can't think of all of them, here is a list of things to start the potential buyer thinking.
1. Why is this engine for sale? Where did it come from?
I would have to wonder why this engine was pulled from a perfectly good airplane.
2. If the airplane was sound, and the engine run out (TBO)....why wasn't this engine rebuilt and reinstalled?
3. If the airplane was sound, why wasn't the engine used as a core for a replacement?
4. If the airplane wasn't sound, why was it no longer usable?
5. If the airplane was no longer usable due to setting, how long did it set and have the internal parts rusted.
(remember that no entry would be made in the logbook because no maintaince has been performed)
6. If the airplane was no longer sound due to a crash or ground incident, the owner of the aircraft might not be around to document the incident and his heirs are just getting rid of stuff.
(I noticed today that there is an airplane and engine for sale on HBA that had an incident many years ago which supposedly damaged a wing and was never flown again. His heir is now putting the engine up for sale.
While it may be perfectly sound, I would have to wonder about the engine and documentaion...and now there probably isn't anyone who could give a detailed account of what happened. So, does the log book tell all...or not?
7. Has the engine you are buying had all ADs completed or will you have to buy parts to bring it up to compliance?
8. Have you researched the "type" or model of the engine to see if it was one of the problematic versions.
9.Is the engine a thick or narrow deck model and will parts always be available for narrow deck versions?
10. How many total hours does the engine have on it? How many times has it been overhauled? Do you know if the crank was ground or polished undersize?
11. Have any modifications or parts swapping been done in its history? (compression ratio changes etc)
12. Are the magnetos still viable and serviceable and are parts available for them?
13. Is the engine you are buying know for having or susceptable to internal crankshaft rusting? (This can result in scrapping the crankshaft)
14. Are all the cylinders on the engine made with the same internal surface and does the log book reflect that?
15. Have any of the valve train components ever been replaced? (If lifters were galled and needed replacement, then the camshaft probably has some issues. If lifters were replaced...was the camshaft inspected or replaced too?)
16.Has the carburetor ever been rebuilt? If you have a high time engine its not unreasonable to think that the internal parts and surfaces of the carb may need reconditioning. It may still work but you should check it out.
Note: A friend of mine completely rebuilt a Champ. On its maiden flight,the engine sputtered and quit and the airplane was a total loss. Upon investigation it was discovered that the float had a large hole in it....and he had just had it
rebuilt by a well known airplane carb rebuilder. The insurance company took the airplane and sold it. Did the log books reflect what had happened? I don't know............
The thing I want to point out here is that a well maintained aero engine is usually a robust and reliable engine....but it must be maintained well in order to continue that reliability. The simple fact that a builder is trying to locate a used engine demonstrates that they are looking for a cheaper way to get flying....and that in and of itself reflects the fact that many decisions about the engine you buy and use will be economic in nature. While these engines built their reputations for reliability and safety based on their original condition as delivered from the factory and many have continued after a 2000 hr TBO........you have to realize that the engine you are buying is essentially not the same engine. Runs as good as new is not the same as being mechanically new. My neighbor sold his well maintained 92 Chevy pickup the other day. It ran perfect with 249,000 miles. It ran "as good as new" but I'm sure most mechanically inclined people would realize its only a matter of time before the timing chain gives up or some other singular part reaches its limit. So "runs as good as new" really doesn't tell you much about the true condition of an engine or what may be lurking inside the engine.
. I have to give up the fact that an aero engine for the most part is easier to install and get running than any aero conversion will be
Its all about what you enjoy doing and what makes you feel comfortable with YOUR build. While ongoing problems in a conversion
will ruin some peoples aero experience, those who successfully complete a conversion will have an added sense of pride in their
accomplishment. Hope you enjoyed reading this. If I forgot anything, please add it in. If you disagree with my opinion, well throw that in too.
Lifter Galling and Oil Analysis
I think I will gradually begin to identify some of the things that happen to certified type engines. While this may be interpreted as a treatise against aero engines, I say that is not the purpose. The purpose is to identify the real life issues that aero engines have. The purpose is that rather than be pro aero engine and blind to any deficiency....be a realist...that aero engines have both an upside and a downside
On another thread, a poster mentioned that his aero engine received a partial rebuild and at appx 4700 hrs was running as good as new. He stated that he had replaced the lifters in the engine but did not mention the camshaft. Further he referenced that the oil sample taken from the engine was good showing no abnormal wear. I would imagine that in his mind he genuinely believed he had demonstrated that the engine repair had gone as planned and there were no concerns. This throws a red flag up for me though. If the lifters were galled, it would seem there should also be some camshaft discord on the lobes. That should transfer into metal particles in the oil. In an automotive application where a flat tappet camshaft is used (as opposed to a roller camshaft) the breakin of the cam followers (lifters) is critical during the first running of the engine after parts replacement of any cam and lifter. The lifter or the cam may be destroyed within minutes after startup. So I have questions in my mind whenever lifters are replaced. Looking at the oil analysis, you have to wonder how accurate it was, and if oil analysis in general is accurate.
Here are a couple of exerpts from a book that are avaiable on the web. If you are considering buying a used aero engine, I highly recommend purchasing this book prior to spending your money. Now,read what they have to say about cam followers and oil analysis.
Now as I mentioned before, people often think they are honestly representing the engine they are selling, but there is often more to it than it
appears. Obviously if the oil analysis came back with high concentrations of metal particles it would be cause for concern, but the lack of any
large concentrations does not necessarily mean there isn't any problem.
Here again, I say........The purpose of this thread is not to knock aero engines but to provide honest insight and real information so that builders are informed when they buy or decide.
[h=2]Re: To aero engine or not to aero engine.......that is the question[/h]
Crankshaft Strikes
Sky Ranch Engineering says" You cannot predict whether the engine has been damaged. MINOR strikes
can result in crankshaft damage."
I have mentioned that minor strikes are sometimes checked by using a dial indicator to inspect the run out
of the crankshaft flange, and if there is no abnormal runout or only a small amount, crankshafts are often
deemed as acceptable. Sky Ranch says otherwise.
So now I go back to the reminder that the used engine you are buying may have originated in the 50s or 60s
when documentation and information was not immediately available and training of mechanics at grass roots
facilities was less formal. In those sixty or so years that have passed your engine may have been worked on
and flown by many different people in many different locales and conditions. Did all of them keep accurate
log books and were all of them honest.........Something to consider.
Again I give credit to Sky Ranch Engineering and recommend you buy their book for the full story.
Fatigue Analysis
I have said many times that one of the questions in my mind is the continued use of used components
in a rebuilt engine. The other day I saw a Lycoming engine for sale that had 9000 hours total time on it.
Now you have to admit that is a remarkable feat and a testament to reliability and durability.....or is it?
I don't have any details on the engine, so I don't know if it had a crankshaft replacement along the way.
I feel with certainty that its had many pistons and cylinders replaced and have to believe the crank has
been ground at least once. So what is a person getting if he buys such an engine? First, the most expensive
component is the crankshaft. Maybe it still has one more grinding or polishing operation left, but you would
need to verify that before purchase....not an easy task.
Probably going to need cylinders, pistons and rings, and bearings. How much for that.
What about the rest of the components....camshaft,lifters,rocker arms,valve springs,oil pump, magnetos,
carburetor, internal gears, crankcase (fretting),connecting rod bolts.......are they all still "good as new"
even if the engine is still running "good as new" ?
I'm going to be quoting Sky Ranch Engineering quite a lot in this thread, so be prepared for that. It gives
(IMHO) some credence to what I have been saying, and I need all the help I can get. But it also provides
a source for a wealth of information for builders.
SRE quote "Regardles of the claims of marketing departments, you can zero time a logbook but you cannot
zero time the metalurgy. Engine parts have a wear life and they have a fatigue life. The primary reason
components catastrophically fail in service is due to metal fatigue."
"Common types of failures include: exhaust valve breakage in older 80 octane Lycoming engines,spalling
of camshaft followers,and failure of the crankshaft flange on Lycoming 'lighting hole' crankshafts" (edited)
Again, I point out that many of these engines have been around a long long long time and you have to realize that
the economics of flying often dictate that components are reused rather than replaced. A workable component
from a damaged engine will be salvaged if there is no apparent damage to the part. So, if an airplane crashes
and the engine is damaged beyond repair......what happens to all those components that "aparently" weren't
damaged in the crash? They go on some APs parts shelf for use in another engine. Think about this for a moment.
When that airplane crashed and had a moving prop strike....the crankshaft had an immediate stoppage and was
ruined. But the pistons also immediately stopped too. The rod bolts were subjected to exponential forces also...
but suffered no "apparent damage". Would you want that rod in your engine? The camshaft also stopped
immediately along with the gears driving it and the oil pump. Any questions in your mind about suitabily of those
components for later use even though there was no apparent damage? Magnetos have momentum when operating,
any apparent damage there? Were any of the components disassembled and magnafluxed or just eyballed and
maybe rotated to see if they still operated. Any hidden stress risers anywhere?
Going back to the "Zero Time" comment. I once read an article about zero time engines. I wrote to the author and
asked him if the factory was using used crankshafts in "zero time" engines as long as they met "factory specs"...
whatever that meant. He did not know and was unable to get the factory to answer the question...so I never got
an answer. Anyone out there know the answer to that question?
I have since been told that used crankshafts may be ground undersize and reused. I have not personally verified
that information. I did see a crankshft for sale the other day that had 9000 hrs on it. Certainly a testament to
durability, but not one I would want in my engine. Wonder whose engine it ended up in.....
Crankshaft Considerations
Lycoming had a major recall on crankshafts and a nasty court battle with the subcontractor who had manufactured them. Against the recommendations of the man-ufacturer, Lycoming changed the metalurgical specs of the crankshafts resulting in crank breakage and recalls. I attached this previously but think it was lost in the shuffle among the comments....so I'm trying to get back to being informational. I think Lycoming has resolved their manufacturing problems with the purchase of modern manufacturing equipment and is again producing a fine albeit expensive product. The problems I'm trying to address concern the economics of used engines.
I am attaching a copy of an article explaining what happened with the crankshafts and the ultimate resolution or lack of resolution of the crankshaft problem. http://www.tomsaircraft.com/Article-LycomingEnginesMSB569A.pdf
About page 3 it starts to explain that while Lycoming offered repair kits at greatly reduced prices ($2k), it apparently was up to the owners of the airplanes in question to follow thru on purchasing them......and apparently some/many didn't. As I understand
it the kit offer has expired and now is about $18k. This means that there are still engines flying that contain suspect crankshafts.
Also, if it was up to an owner to buy the kit and have it installed, I don't believe there was any verification of work performed.
An owner might buy the kit and if he never installed it before selling the airplane, he would have a valuable asset for $2k. If he did install the crankshaft, what happened to the crankshaft that was removed. Did it become airboat or experimental material.
I admit that I am speculating here. If I'm incorrect then please correct me.
That being said, there are many things that happen to aero engines. I always have to wonder what happened to any engine which now has its crankshaft for sale....especially it its bearing journals are std. size. Here are some excerpts from some ads.
Ad #1
Lycoming Crankshaft w/Form 8130-3 (Yellow Tagged) TO-360-C1A6D (Big Main)
.440 Crank Flange (w/lightening holes). Part Number: LW-12172
Main Journals = Std
Rod Journals = Std
Condition: Overhauled, includes Form 8130-3 (Yellow Tags)
Note: It is the responsibility of the buyer to ensure airworthiness and compatibility when installing these parts on an aircraft.
Ad #2
A Non-Certified crankshaft for expiremental or airboat use only. There is corrosion on the #1 main. The mains are -.010 and rods are standard.
Ad #3
$2500
A Lycoming airboat crankshaft. The part number is 13E27622 and fits an IO-540 engine model. It was reconditioned to be certified, but was not because there are heat cracks on the #4,5, and 6 rods. The rods and mains are both standard size.
Ad #4
The parts we sell in Ebay are serviceable, unless, otherwise noted. They may be overhauled or only inspected
visually and cleaned. Parts are cleaned and treated for anti-corrosion for storage purposes. A yellow tag/FAA
8130-3 Authorized Release Certificate may be available on some parts that are inspected.
Airworthiness is to be determined by only the person or persons installing said item on aircraft.
Ad #5
Up for sale is a Overhauled Lycoming LW-17725 Fits IO-540
Large Mains, Large Rods, Uses 10646 or 19332 Rods.
Main -M003
Rods -M003
This Crankshaft is Airworthy.
Dial tested to verify true.
Magnaflux to verify no cracks.
Polished
We will install new bushings when purchased.
This last one is selling for $8000 and says its is air worthy. I'm not doubting this vendor, but I still have to ask myself how this extremely valuable component became available? While I may be overly cautious, I still have to wonder what the story is behind each of these items, and if faced with expensive replacement costs, will some builder try to use these crankshafts in an airplane?
(This is not meant to cast any aspersions on any of the people placing the adds and selling the components, only to point out the fact that purchasers of the components are left to their own conscience on how they may use the components.)
Last edited by ekimneirbo.; July 26th, 2015 at 10:40 AM.
How Do Aircraft Engines Fail
Depending on your point of view, this can be taken as somewhat of a testimonial to their durability. It does agree with TFF that engines should be rebuilt
based on their condition rather than a preset term of operation. I did find it interesting that they mentioned "unreported prop strikes" , so it apparently
happens often enough to be on the radar screen of the manufacturers. That just re-enforces my comments about the accuracy of log books............
Other than that, this site pretty well considers aero engines very reliable.
How Do Piston Aircraft Engines Fail? « Opinion Leaders
How I would proceed with buying an engine with no history ....doesn't mean its the only way, but at least something to consider when buying your used engine.
How you would deal with having been "given"
an IO-360 with no known history,no log books and its identification tag removed....
here is my rather detailed explanation of how I would proceed. I would also proceed this way if it was
a case of just not having any log books.
.Since the purpose of this thread is to help people decide on when to buy and use a used
airplane engine, here is how I personally would proceed given the scenario that was presented.
I'm going to answer the questions out of order because that seems the best way to do it. This will
be a fairly detailed explanation.
If I were in possession of a used aero engine that I didn't know the history on, didn't have a log book,
and the engine had the data plate removed.......then the first burning question in my mind that just
won't go away is ...Why was this engine removed? Its just not normal to remove a perfectly good
engine and remove the data plate and log book even if it has reached TBO.
1. The first thing I would do is purchase a new log book, make an Experimental Case number up
and write an explanation of when and why this log book came to be. Experimental IO-360-XXX
Then if the teardown results in a usable engine, you have a complete record of its condition at
teardown and what was done prior to reassembly. To many people building a homebuilt or
possibly buying your airplane from you, this might be as good as a factory log...it would certainly
be better than nothing. I would also place some kind of disclaimer in the book because of the fact
that it is for experimental use. Also use your digital camera to make a record of the engine and its
disassembly...making close ups of components and their condition.
2. Next I would inspect the engine visually and place a dial indicator on the crankshaft and check
its runout and fore and aft movement. I would pull the spark plugs and rotate the engine to see
if there was reasonably smooth rotation and if possible set it up to do a cylinder leakdown test.
3. Next, I would remove the cylinders marking each one for replacement in its original position.
The cylinders would be visually inspected for flaws and casting flash. Remove any flash and
lightly smooth the intake and exhaust passages while also removing any carbon buildup.
Check the valve springs for tension and length. Check the valve guides to see if their is any
looseness or wear on valve stems....especially the exhaust valve. If all is OK, lap the valves
in the seats using dykem blue to see that width and concentricity are acceptable. Inspect the
rocker arms for wear. Be sure to organize and tag all parts for reassembly to the exact same
place they were removed from.
4. Begin disassembly of the crankcase. I would not use the engine without doing this step because
of the log book/data plate unknowns. Personally, I consider this a critical decision given the
mystery of why the engine was originally removed.
5. Be sure to remove the parts in an organized manner so that all parts gets placed with their original
mating parts. Make a list for later entry into the log book. The list will contain info such as the
following: First visually inspect the pistons for any obvious problems and note anything such
as minor scoring or wear. Make a note of the condition. Then place each piston and rod assembly
on a scale as a combined assembly and record the weights of each assembly. Then disassemble
the rod/piston and record each individual components weight. If there is much difference, I
would consider trying to make everything closer in weight. Find the lightest of each component
and try to get all the others to the same weight. Rods are weighed by a special fixture that allows
each end to be verified separately. Since most people won't have access to one of these fixtures,
I would at least try to insure that the overall weight of the rods is similar. If its sufficiently wrong
to begin with, then evening them out probably won't hurt anything. Note! Before doing to much to
insure similar weights, I would replace all rod bolts with new ones.
6. The crankshaft! This is the key component in this scenario if up to this point you have found no
reason why the engine was removed and the id tag removed. I would mic all journals and record
what I found. I would visually inspect the crankshaft and photograph it in detail. Personally, my
whole decision on what I do with this engine is probably going to revolve around the results of
trip to the repair facility for magnaflux and possible grinding.. My logic here is that if the crankshaft
is good, I will know it, and now is the time to make the in case components bulletproof and as good as new.
The log book will show
the care you have taken and hopefully if there is any needed repair for this engine in the future, it
will only consist of things that can be done without splitting the cases. Why gamble on this when
you can be sure and probably never have to deal with it again in your flying life.
7. The camshaft : I would visually inspect it for rust or corrosion and then take a mic and measure
from the base of each lobe to top of each lobe and compare the readings. This doesn't specifically
tell you a lot other than being able to compare them for similarity and log them for future reference.
The correct way to check the cam is to place it between centers or in a Vblock and use a dial indicator
to check the lift and concentricity of the shaft. Also mic the bearing sizes and record them. When
you inspect the engine cases , you may want to use the cam to check how much clearance is between
the cam bearings and the case since there is no real bearing used.
8. Engine cases: Clean the engine cases thoroughly and perform a visual inspection . You may want
to take them to a transmission shop and see if they will clean them. Be very careful about cleaning
and flushing the oil passages. You may want to lap the mating surfaces to freshen them up. Then its
up to you whether you want to send them to the repair station.
9. Oil Pump: Be sure to check how much clearance the oil pump has and maybe install a new spring
10: Gears: If noting else has been found wrong, I would clean and visually inspect them.
There are a few other things to make some decisions on using, but if a this point you have found
nothing out of sorts, you should be feeling pretty good about your engine. One last thing, even
though your engine is no longer a true certified engine, I would check for any ADs that may apply
to that type of engine. Then I would make a new engine tag and affix it to the engine case proclaiming
this engine to be an experimental engine with your made up identification number/new log book
My point thru all this is the unknown background of the engine originally gave me a feeling of concern
because it just didn't seem to make any sense. Normally anything that could be fixed via a top overhaul
would just let the engine continue as a certified engine. Its when you have to split the cases that expenses
may rise to the point of putting an engine in salvage. Even at that point, the engine will normally be rebuilt
unless there is something requiring crankshaft replacement. Crankshaft replacement cost is the only viable
reason I can think of that might cause someone not to rebuild the engine or sell it as a rebuildable core.
Thats why I think the one thing I would be sure to do when purchasing an engine with no tag or even
just without a log book...is to have the crank inspected.
If the crankshaft failed the inspection due to cracks,run out, or anything that indicated it had a stoppage,
then I would have to reconsider using any of the rotating parts and maybe the cases. I don't think in good
conscience I could put these parts up for sale to anyone that might use them in a flight engine. There are
some components that still have value, but I would be extremely cautious about rebuilding the engine.
I'm sure I missed something, but at least I tried.......and thats how I would proceed...but each builder
must make their own choice.....but hopefully you have the right questions to ask now.
At this point the original thread seemed to develop into a bunch of personal attacks and much of what followed was of no real use to anyone just wanting to increase their knowledge. There are a few insightful posts from some others about things which actually happened to them and their experiences with aero engines. I don't want to include those posts as they were not originated by me. My suggestion is if you read the original thread, when you notice personal comments being made...whether by me or someone else...just skip over them and concentrate the factual stuff.
Let me say this in closing: All the self proclaimed experts assure me that used engines are still reliable and bullet proof and there is
no wide spread failure rate. One of them did reference the fact that "according to him" the failure rate of experimental aircraft was
very high when compared the rest of the GA fleet. He also steadfastly stated that 99% of them are powered by dedicated aero
engines......but assured me that aero engines really don't have enough problems to worry about. You decide what that means.
For myself, the graphs I have seen don't seem to show much difference between the two entities, but like always, we can always
find a chart that agrees with our personal view of things. You have to decide for yourself what you believe. I hope if you took the
time to read all of this you learned something from it that will be helpful to you in your search for an engine. Statistics really don't
mean a darn thing unless its your airplane that has an engine quit. So if you choose to proceed wisely or blindly, its your choice.
ekimneirbo
airplane is rather long and often drifted into either discussion of auto engine suitability or
comments about my knowledge of certified engines. This synopsis is hopefully ONLY
about these two aero engines and what you should consider when choosing to use one.
It is not intended to suggest that some other option is better, but only to point out the
positives and negatives so you choose wisely when considering an aero LyCont engine.
In the original thread my postings were met with a lot of discord, and even though I
specifically asked that any mistatements be corrected.....nothing factual was submitted.
It pretty much deteriorated into a pissing contest with a few factual comments now and
then. So here is what I feel is helpful and factual in a somewhat condensed version.
After posting this in its entireity, anyone can make any comment they wish...but the
meat of the information will be here in one semi-organized post. Who ever takes the
time to read it can decide for themselves if it has any worth to them.
LyConts have developed a great record for reliability when purchased new , maintained
and flown regularly.You MUST maintain and fly regularly to expect great reliability.
If you purchase a USED LyCont because it is easier to adapt to your airplane and you
feel the cost of initial purchase will be similar to or even less than the cost of some other
option...you may be right. Later I will point out some of the pitfalls that can occur after
the purchase, but for now the initial cost of purchase and installation is attractive.
No matter how the engine turns out, even if it is essentially perfect, you should think
about the following considerations.
1. These engines built their record of reliability by being maintained on at least a yearly
basis by professionally trained mechanics, adherence to ADs, and replacement of parts
when needed....per the inspections and ADs.
Your now Experimental engine will not be required to comply with these requirements
any longer. Common sense would tell you that if you wish for your engine to be as reliable
as when it was certified, you will still need a professional to inspect it, and you
probably need to comply with any ADs for the engine even though nether of these is
a LEGAL requirement. If you are competent and confident enough to do your own work,
then you can, but be honest with yourself about your abilities.
So, your easily installed and reasonably inexpensive purchase may need to have the
same expensive attention in order to stay reliable. Many builders have friends who are
APs and may recieve these services free or cheaply....many builders will have to pay.
Decide which scenario applies to you.
2. Will you be able to find a licensed AP who is willing to work on your engine and sign
off on the work now that the engine is installed in an experimental airplane? Remember
now that your airplane is now being possibly worked on by an uncertified individual(you)
and that if your airplane should fail for any reason, the FAA will be in contact with HIM.
So it is possible that finding mechanical help could prove difficult, especially on a long
flight.
3. If you expect to do all your own work on the LyCont, you will need to purchase
some special tools which are specific to LyConts along with service manuals to supplement
your knowledge. If you are handy with tools and mechanical things
you may be able to do your own work....but since your life may depend on how
well you do it, I would still suggest getting some knowledgeable assistance.
4.Those are specific considerations that should be viewed even if your engine is in
perfect condition when you buy it. If your engine turns out to be in less than perfect
condition, then you will need to make immediate monetary choices on how to proceed.
Talk to some APs and get a feel for the "what ifs" will cost if the engine you purchase
needs certain items replaced. Research if there are any ADs that apply to the type of
engine you wish to buy and then you can check for compliance before buying. If not,
you may need to purchase and install the parts even though not Legally required to.
Its a matter of safety not legality on an experimental airplane.
One of the comments made was that 99% of all experimentals will be powered by an
engine made specifically by an aero engine manufacturer. While thats probably some
where near the truth, the point of this thread is to make you aware of some of the issues
with the used engines that are available. While some may interpret that as pushing you
toward conversion engines, it can also be interpreted as pushing you toward a NEW
aero engine, or educating you about what you may get with a rebuilt engine. So its
really not pushing you anywhere....its just pointing out some facts.
[h=2]To aero engine or not to aero engine.......that is the question[/h]
When building an airplane one of the first questions a builder must consider is cost and type of engine. Now let me say right up front that choices will vary greatly with the type of airplane you wish to build. Small and smaller engines generally
are used in smaller,lighter,and slower flying airplanes. There are specialized exceptions. Then you move into the midsize area where choices begin to expand somewhat with water cooling and turbocharging sometimes being employed. Moving on up to engines above 350 cu inches........almost anything can be made to work if it produces plenty of power because you generally are using an airplane designed for the heavier engines. Nothing is always true,you have to use generalities until
you get specific about what airplane you want to build and what its purpose in flight will be. Fast,slow,crosscountry,STOL, single passenger, etc. Define what YOU want and then you can narrow down your choices. If you decide to go with a non-
traditional aero engine, there will be plenty of people to tell you why not. Its impossible to address auto conversions because the absolutes of conversion do not apply.I say this because each conversion has its own set of details to work out. Putting an VW or Corvair will not carry the same benefits or detriments that a water cooled V8 will entail. So, when discussing conversions, don't let the naysayers convince you that it can't be done. Oshkosh is full of success stories every year.
Back to the purpose of this thread........to aero engine or not
I'm sure that everything I say here will be construed negatively by believers in only using an aero engine, thats just the way things are. But, the things I say here will be my considered opinions and true as far as I know.
First, let me say that from its birth at the factory, most commonly used naturally aspirated aero engines are very reliable and expensive. There have been some notable exceptions and a few duds from the factories, but for the most part they are
pretty reliable.
Once the engines begin to work in the real world, used by ordinary imperfect human beings, many things can happen to them.
Each engine will come with a log book where every detail of its life and maintainance will be thoroughly documented. Don't believe that myth. While its a good selling point and gives the buyer a feel good moment....it really not reliable.
What can go wrong....everything from a dishonest seller to an honest omission.
"Well it was just a minor prop strike in grass, nothing to be concerned about. If I document it, the engine will need to be torn down for inspection and thats pretty expensive. Guess I'll just check the run out and if its ok, that'll be fine"
"Hmm noticed a little rust inside the crankshaft, but there is always some in these engines, probably nothing to worry about"
"Cylinder head temps seem a little high these days, but the engine runs fine....probably nothing to worry about."
"The oil sample showed a little metal in it but it was within specs, so I guess it doesn't need to be documented."
Lots of things go undocumented in the life of an engine. I remember one day many years ago walking along the grass at a local airfield and coming upon a member of the local club who had his Cessna 150 engine partially disassembled. Being new to the sport I didn't realize what was going on. I stopped to talk and he stressed the point that I should not mention to the AP/airfield owner what he was doing. Eventually the fellow was forced out of the aero club because of his continued attempts to circumvent proper mainataince and insurance for his airplane. He had a garage/hangar that backed up to the airfield. One day he landed his airplane
and rolled it in the hangar. Shortly thereafter the airfield owner placed a large dirt berm right next to his hangar door so the airplane could not be taken out again. About ten years later I bought the airplane and removed the wings and brought it home. After a while I decided it would be too expensive to repair the engine and sold the whole airplane to a dismantler.
Another time I worked on an engine that had been recently rebuilt by an AP and found that he didn't know the engine was supposed to have oil squirters in it.....and he was teaching me.
You have to remember that the fifties, sixties, and seventies were a totally different era from today. We didn't have computers everywhere. Information was not at our fingertips or even available. People had less disposable income and had to make do
with less than optimal conditions.A lot of todays engines were manufactured during that time and are still doing duty today.
You do not know what has transpired in the life of these engines no matter what log books say....and many engines don't even have a log book. Did you ever wonder why someone would lose the log book for an expensive engine?
Another thing, when aero engines do go bad all of the attendant parts are always salvaged and stored for some future use.
While rebuilding several engines, I was directed to a stack of connecting rods from salvage engines to replace one in the engine I was assembling. Although they all looked similar, I decided to employ an old racers trick and weighed the connecting rods. I couldn't believe how much difference I found in the weights. No wonder those engines vibrate.
My point is that its difficult to consider the myriad number of things that have happened in an engines life, or to believe that all of these things were properly documented by the thousands of different individuals who have been involved with them.
While I'm sure I can't think of all of them, here is a list of things to start the potential buyer thinking.
1. Why is this engine for sale? Where did it come from?
I would have to wonder why this engine was pulled from a perfectly good airplane.
2. If the airplane was sound, and the engine run out (TBO)....why wasn't this engine rebuilt and reinstalled?
3. If the airplane was sound, why wasn't the engine used as a core for a replacement?
4. If the airplane wasn't sound, why was it no longer usable?
5. If the airplane was no longer usable due to setting, how long did it set and have the internal parts rusted.
(remember that no entry would be made in the logbook because no maintaince has been performed)
6. If the airplane was no longer sound due to a crash or ground incident, the owner of the aircraft might not be around to document the incident and his heirs are just getting rid of stuff.
(I noticed today that there is an airplane and engine for sale on HBA that had an incident many years ago which supposedly damaged a wing and was never flown again. His heir is now putting the engine up for sale.
While it may be perfectly sound, I would have to wonder about the engine and documentaion...and now there probably isn't anyone who could give a detailed account of what happened. So, does the log book tell all...or not?
7. Has the engine you are buying had all ADs completed or will you have to buy parts to bring it up to compliance?
8. Have you researched the "type" or model of the engine to see if it was one of the problematic versions.
9.Is the engine a thick or narrow deck model and will parts always be available for narrow deck versions?
10. How many total hours does the engine have on it? How many times has it been overhauled? Do you know if the crank was ground or polished undersize?
11. Have any modifications or parts swapping been done in its history? (compression ratio changes etc)
12. Are the magnetos still viable and serviceable and are parts available for them?
13. Is the engine you are buying know for having or susceptable to internal crankshaft rusting? (This can result in scrapping the crankshaft)
14. Are all the cylinders on the engine made with the same internal surface and does the log book reflect that?
15. Have any of the valve train components ever been replaced? (If lifters were galled and needed replacement, then the camshaft probably has some issues. If lifters were replaced...was the camshaft inspected or replaced too?)
16.Has the carburetor ever been rebuilt? If you have a high time engine its not unreasonable to think that the internal parts and surfaces of the carb may need reconditioning. It may still work but you should check it out.
Note: A friend of mine completely rebuilt a Champ. On its maiden flight,the engine sputtered and quit and the airplane was a total loss. Upon investigation it was discovered that the float had a large hole in it....and he had just had it
rebuilt by a well known airplane carb rebuilder. The insurance company took the airplane and sold it. Did the log books reflect what had happened? I don't know............
The thing I want to point out here is that a well maintained aero engine is usually a robust and reliable engine....but it must be maintained well in order to continue that reliability. The simple fact that a builder is trying to locate a used engine demonstrates that they are looking for a cheaper way to get flying....and that in and of itself reflects the fact that many decisions about the engine you buy and use will be economic in nature. While these engines built their reputations for reliability and safety based on their original condition as delivered from the factory and many have continued after a 2000 hr TBO........you have to realize that the engine you are buying is essentially not the same engine. Runs as good as new is not the same as being mechanically new. My neighbor sold his well maintained 92 Chevy pickup the other day. It ran perfect with 249,000 miles. It ran "as good as new" but I'm sure most mechanically inclined people would realize its only a matter of time before the timing chain gives up or some other singular part reaches its limit. So "runs as good as new" really doesn't tell you much about the true condition of an engine or what may be lurking inside the engine.
. I have to give up the fact that an aero engine for the most part is easier to install and get running than any aero conversion will be
Its all about what you enjoy doing and what makes you feel comfortable with YOUR build. While ongoing problems in a conversion
will ruin some peoples aero experience, those who successfully complete a conversion will have an added sense of pride in their
accomplishment. Hope you enjoyed reading this. If I forgot anything, please add it in. If you disagree with my opinion, well throw that in too.
Lifter Galling and Oil Analysis
I think I will gradually begin to identify some of the things that happen to certified type engines. While this may be interpreted as a treatise against aero engines, I say that is not the purpose. The purpose is to identify the real life issues that aero engines have. The purpose is that rather than be pro aero engine and blind to any deficiency....be a realist...that aero engines have both an upside and a downside
On another thread, a poster mentioned that his aero engine received a partial rebuild and at appx 4700 hrs was running as good as new. He stated that he had replaced the lifters in the engine but did not mention the camshaft. Further he referenced that the oil sample taken from the engine was good showing no abnormal wear. I would imagine that in his mind he genuinely believed he had demonstrated that the engine repair had gone as planned and there were no concerns. This throws a red flag up for me though. If the lifters were galled, it would seem there should also be some camshaft discord on the lobes. That should transfer into metal particles in the oil. In an automotive application where a flat tappet camshaft is used (as opposed to a roller camshaft) the breakin of the cam followers (lifters) is critical during the first running of the engine after parts replacement of any cam and lifter. The lifter or the cam may be destroyed within minutes after startup. So I have questions in my mind whenever lifters are replaced. Looking at the oil analysis, you have to wonder how accurate it was, and if oil analysis in general is accurate.
Here are a couple of exerpts from a book that are avaiable on the web. If you are considering buying a used aero engine, I highly recommend purchasing this book prior to spending your money. Now,read what they have to say about cam followers and oil analysis.
Now as I mentioned before, people often think they are honestly representing the engine they are selling, but there is often more to it than it
appears. Obviously if the oil analysis came back with high concentrations of metal particles it would be cause for concern, but the lack of any
large concentrations does not necessarily mean there isn't any problem.
Here again, I say........The purpose of this thread is not to knock aero engines but to provide honest insight and real information so that builders are informed when they buy or decide.
[h=2]Re: To aero engine or not to aero engine.......that is the question[/h]
Crankshaft Strikes
Sky Ranch Engineering says" You cannot predict whether the engine has been damaged. MINOR strikes
can result in crankshaft damage."
I have mentioned that minor strikes are sometimes checked by using a dial indicator to inspect the run out
of the crankshaft flange, and if there is no abnormal runout or only a small amount, crankshafts are often
deemed as acceptable. Sky Ranch says otherwise.
So now I go back to the reminder that the used engine you are buying may have originated in the 50s or 60s
when documentation and information was not immediately available and training of mechanics at grass roots
facilities was less formal. In those sixty or so years that have passed your engine may have been worked on
and flown by many different people in many different locales and conditions. Did all of them keep accurate
log books and were all of them honest.........Something to consider.
Again I give credit to Sky Ranch Engineering and recommend you buy their book for the full story.
Fatigue Analysis
I have said many times that one of the questions in my mind is the continued use of used components
in a rebuilt engine. The other day I saw a Lycoming engine for sale that had 9000 hours total time on it.
Now you have to admit that is a remarkable feat and a testament to reliability and durability.....or is it?
I don't have any details on the engine, so I don't know if it had a crankshaft replacement along the way.
I feel with certainty that its had many pistons and cylinders replaced and have to believe the crank has
been ground at least once. So what is a person getting if he buys such an engine? First, the most expensive
component is the crankshaft. Maybe it still has one more grinding or polishing operation left, but you would
need to verify that before purchase....not an easy task.
Probably going to need cylinders, pistons and rings, and bearings. How much for that.
What about the rest of the components....camshaft,lifters,rocker arms,valve springs,oil pump, magnetos,
carburetor, internal gears, crankcase (fretting),connecting rod bolts.......are they all still "good as new"
even if the engine is still running "good as new" ?
I'm going to be quoting Sky Ranch Engineering quite a lot in this thread, so be prepared for that. It gives
(IMHO) some credence to what I have been saying, and I need all the help I can get. But it also provides
a source for a wealth of information for builders.
SRE quote "Regardles of the claims of marketing departments, you can zero time a logbook but you cannot
zero time the metalurgy. Engine parts have a wear life and they have a fatigue life. The primary reason
components catastrophically fail in service is due to metal fatigue."
"Common types of failures include: exhaust valve breakage in older 80 octane Lycoming engines,spalling
of camshaft followers,and failure of the crankshaft flange on Lycoming 'lighting hole' crankshafts" (edited)
Again, I point out that many of these engines have been around a long long long time and you have to realize that
the economics of flying often dictate that components are reused rather than replaced. A workable component
from a damaged engine will be salvaged if there is no apparent damage to the part. So, if an airplane crashes
and the engine is damaged beyond repair......what happens to all those components that "aparently" weren't
damaged in the crash? They go on some APs parts shelf for use in another engine. Think about this for a moment.
When that airplane crashed and had a moving prop strike....the crankshaft had an immediate stoppage and was
ruined. But the pistons also immediately stopped too. The rod bolts were subjected to exponential forces also...
but suffered no "apparent damage". Would you want that rod in your engine? The camshaft also stopped
immediately along with the gears driving it and the oil pump. Any questions in your mind about suitabily of those
components for later use even though there was no apparent damage? Magnetos have momentum when operating,
any apparent damage there? Were any of the components disassembled and magnafluxed or just eyballed and
maybe rotated to see if they still operated. Any hidden stress risers anywhere?
Going back to the "Zero Time" comment. I once read an article about zero time engines. I wrote to the author and
asked him if the factory was using used crankshafts in "zero time" engines as long as they met "factory specs"...
whatever that meant. He did not know and was unable to get the factory to answer the question...so I never got
an answer. Anyone out there know the answer to that question?
I have since been told that used crankshafts may be ground undersize and reused. I have not personally verified
that information. I did see a crankshft for sale the other day that had 9000 hrs on it. Certainly a testament to
durability, but not one I would want in my engine. Wonder whose engine it ended up in.....
Crankshaft Considerations
Lycoming had a major recall on crankshafts and a nasty court battle with the subcontractor who had manufactured them. Against the recommendations of the man-ufacturer, Lycoming changed the metalurgical specs of the crankshafts resulting in crank breakage and recalls. I attached this previously but think it was lost in the shuffle among the comments....so I'm trying to get back to being informational. I think Lycoming has resolved their manufacturing problems with the purchase of modern manufacturing equipment and is again producing a fine albeit expensive product. The problems I'm trying to address concern the economics of used engines.
I am attaching a copy of an article explaining what happened with the crankshafts and the ultimate resolution or lack of resolution of the crankshaft problem. http://www.tomsaircraft.com/Article-LycomingEnginesMSB569A.pdf
About page 3 it starts to explain that while Lycoming offered repair kits at greatly reduced prices ($2k), it apparently was up to the owners of the airplanes in question to follow thru on purchasing them......and apparently some/many didn't. As I understand
it the kit offer has expired and now is about $18k. This means that there are still engines flying that contain suspect crankshafts.
Also, if it was up to an owner to buy the kit and have it installed, I don't believe there was any verification of work performed.
An owner might buy the kit and if he never installed it before selling the airplane, he would have a valuable asset for $2k. If he did install the crankshaft, what happened to the crankshaft that was removed. Did it become airboat or experimental material.
I admit that I am speculating here. If I'm incorrect then please correct me.
That being said, there are many things that happen to aero engines. I always have to wonder what happened to any engine which now has its crankshaft for sale....especially it its bearing journals are std. size. Here are some excerpts from some ads.
Ad #1
Lycoming Crankshaft w/Form 8130-3 (Yellow Tagged) TO-360-C1A6D (Big Main)
.440 Crank Flange (w/lightening holes). Part Number: LW-12172
Main Journals = Std
Rod Journals = Std
Condition: Overhauled, includes Form 8130-3 (Yellow Tags)
Note: It is the responsibility of the buyer to ensure airworthiness and compatibility when installing these parts on an aircraft.
Ad #2
A Non-Certified crankshaft for expiremental or airboat use only. There is corrosion on the #1 main. The mains are -.010 and rods are standard.
Ad #3
$2500
A Lycoming airboat crankshaft. The part number is 13E27622 and fits an IO-540 engine model. It was reconditioned to be certified, but was not because there are heat cracks on the #4,5, and 6 rods. The rods and mains are both standard size.
Ad #4
The parts we sell in Ebay are serviceable, unless, otherwise noted. They may be overhauled or only inspected
visually and cleaned. Parts are cleaned and treated for anti-corrosion for storage purposes. A yellow tag/FAA
8130-3 Authorized Release Certificate may be available on some parts that are inspected.
Airworthiness is to be determined by only the person or persons installing said item on aircraft.
Ad #5
Up for sale is a Overhauled Lycoming LW-17725 Fits IO-540
Large Mains, Large Rods, Uses 10646 or 19332 Rods.
Main -M003
Rods -M003
This Crankshaft is Airworthy.
Dial tested to verify true.
Magnaflux to verify no cracks.
Polished
We will install new bushings when purchased.
This last one is selling for $8000 and says its is air worthy. I'm not doubting this vendor, but I still have to ask myself how this extremely valuable component became available? While I may be overly cautious, I still have to wonder what the story is behind each of these items, and if faced with expensive replacement costs, will some builder try to use these crankshafts in an airplane?
(This is not meant to cast any aspersions on any of the people placing the adds and selling the components, only to point out the fact that purchasers of the components are left to their own conscience on how they may use the components.)
Last edited by ekimneirbo.; July 26th, 2015 at 10:40 AM.
How Do Aircraft Engines Fail
Depending on your point of view, this can be taken as somewhat of a testimonial to their durability. It does agree with TFF that engines should be rebuilt
based on their condition rather than a preset term of operation. I did find it interesting that they mentioned "unreported prop strikes" , so it apparently
happens often enough to be on the radar screen of the manufacturers. That just re-enforces my comments about the accuracy of log books............
Other than that, this site pretty well considers aero engines very reliable.
How Do Piston Aircraft Engines Fail? « Opinion Leaders
How I would proceed with buying an engine with no history ....doesn't mean its the only way, but at least something to consider when buying your used engine.
How you would deal with having been "given"
an IO-360 with no known history,no log books and its identification tag removed....
here is my rather detailed explanation of how I would proceed. I would also proceed this way if it was
a case of just not having any log books.
.Since the purpose of this thread is to help people decide on when to buy and use a used
airplane engine, here is how I personally would proceed given the scenario that was presented.
I'm going to answer the questions out of order because that seems the best way to do it. This will
be a fairly detailed explanation.
If I were in possession of a used aero engine that I didn't know the history on, didn't have a log book,
and the engine had the data plate removed.......then the first burning question in my mind that just
won't go away is ...Why was this engine removed? Its just not normal to remove a perfectly good
engine and remove the data plate and log book even if it has reached TBO.
1. The first thing I would do is purchase a new log book, make an Experimental Case number up
and write an explanation of when and why this log book came to be. Experimental IO-360-XXX
Then if the teardown results in a usable engine, you have a complete record of its condition at
teardown and what was done prior to reassembly. To many people building a homebuilt or
possibly buying your airplane from you, this might be as good as a factory log...it would certainly
be better than nothing. I would also place some kind of disclaimer in the book because of the fact
that it is for experimental use. Also use your digital camera to make a record of the engine and its
disassembly...making close ups of components and their condition.
2. Next I would inspect the engine visually and place a dial indicator on the crankshaft and check
its runout and fore and aft movement. I would pull the spark plugs and rotate the engine to see
if there was reasonably smooth rotation and if possible set it up to do a cylinder leakdown test.
3. Next, I would remove the cylinders marking each one for replacement in its original position.
The cylinders would be visually inspected for flaws and casting flash. Remove any flash and
lightly smooth the intake and exhaust passages while also removing any carbon buildup.
Check the valve springs for tension and length. Check the valve guides to see if their is any
looseness or wear on valve stems....especially the exhaust valve. If all is OK, lap the valves
in the seats using dykem blue to see that width and concentricity are acceptable. Inspect the
rocker arms for wear. Be sure to organize and tag all parts for reassembly to the exact same
place they were removed from.
4. Begin disassembly of the crankcase. I would not use the engine without doing this step because
of the log book/data plate unknowns. Personally, I consider this a critical decision given the
mystery of why the engine was originally removed.
5. Be sure to remove the parts in an organized manner so that all parts gets placed with their original
mating parts. Make a list for later entry into the log book. The list will contain info such as the
following: First visually inspect the pistons for any obvious problems and note anything such
as minor scoring or wear. Make a note of the condition. Then place each piston and rod assembly
on a scale as a combined assembly and record the weights of each assembly. Then disassemble
the rod/piston and record each individual components weight. If there is much difference, I
would consider trying to make everything closer in weight. Find the lightest of each component
and try to get all the others to the same weight. Rods are weighed by a special fixture that allows
each end to be verified separately. Since most people won't have access to one of these fixtures,
I would at least try to insure that the overall weight of the rods is similar. If its sufficiently wrong
to begin with, then evening them out probably won't hurt anything. Note! Before doing to much to
insure similar weights, I would replace all rod bolts with new ones.
6. The crankshaft! This is the key component in this scenario if up to this point you have found no
reason why the engine was removed and the id tag removed. I would mic all journals and record
what I found. I would visually inspect the crankshaft and photograph it in detail. Personally, my
whole decision on what I do with this engine is probably going to revolve around the results of
trip to the repair facility for magnaflux and possible grinding.. My logic here is that if the crankshaft
is good, I will know it, and now is the time to make the in case components bulletproof and as good as new.
The log book will show
the care you have taken and hopefully if there is any needed repair for this engine in the future, it
will only consist of things that can be done without splitting the cases. Why gamble on this when
you can be sure and probably never have to deal with it again in your flying life.
7. The camshaft : I would visually inspect it for rust or corrosion and then take a mic and measure
from the base of each lobe to top of each lobe and compare the readings. This doesn't specifically
tell you a lot other than being able to compare them for similarity and log them for future reference.
The correct way to check the cam is to place it between centers or in a Vblock and use a dial indicator
to check the lift and concentricity of the shaft. Also mic the bearing sizes and record them. When
you inspect the engine cases , you may want to use the cam to check how much clearance is between
the cam bearings and the case since there is no real bearing used.
8. Engine cases: Clean the engine cases thoroughly and perform a visual inspection . You may want
to take them to a transmission shop and see if they will clean them. Be very careful about cleaning
and flushing the oil passages. You may want to lap the mating surfaces to freshen them up. Then its
up to you whether you want to send them to the repair station.
9. Oil Pump: Be sure to check how much clearance the oil pump has and maybe install a new spring
10: Gears: If noting else has been found wrong, I would clean and visually inspect them.
There are a few other things to make some decisions on using, but if a this point you have found
nothing out of sorts, you should be feeling pretty good about your engine. One last thing, even
though your engine is no longer a true certified engine, I would check for any ADs that may apply
to that type of engine. Then I would make a new engine tag and affix it to the engine case proclaiming
this engine to be an experimental engine with your made up identification number/new log book
My point thru all this is the unknown background of the engine originally gave me a feeling of concern
because it just didn't seem to make any sense. Normally anything that could be fixed via a top overhaul
would just let the engine continue as a certified engine. Its when you have to split the cases that expenses
may rise to the point of putting an engine in salvage. Even at that point, the engine will normally be rebuilt
unless there is something requiring crankshaft replacement. Crankshaft replacement cost is the only viable
reason I can think of that might cause someone not to rebuild the engine or sell it as a rebuildable core.
Thats why I think the one thing I would be sure to do when purchasing an engine with no tag or even
just without a log book...is to have the crank inspected.
If the crankshaft failed the inspection due to cracks,run out, or anything that indicated it had a stoppage,
then I would have to reconsider using any of the rotating parts and maybe the cases. I don't think in good
conscience I could put these parts up for sale to anyone that might use them in a flight engine. There are
some components that still have value, but I would be extremely cautious about rebuilding the engine.
I'm sure I missed something, but at least I tried.......and thats how I would proceed...but each builder
must make their own choice.....but hopefully you have the right questions to ask now.
At this point the original thread seemed to develop into a bunch of personal attacks and much of what followed was of no real use to anyone just wanting to increase their knowledge. There are a few insightful posts from some others about things which actually happened to them and their experiences with aero engines. I don't want to include those posts as they were not originated by me. My suggestion is if you read the original thread, when you notice personal comments being made...whether by me or someone else...just skip over them and concentrate the factual stuff.
Let me say this in closing: All the self proclaimed experts assure me that used engines are still reliable and bullet proof and there is
no wide spread failure rate. One of them did reference the fact that "according to him" the failure rate of experimental aircraft was
very high when compared the rest of the GA fleet. He also steadfastly stated that 99% of them are powered by dedicated aero
engines......but assured me that aero engines really don't have enough problems to worry about. You decide what that means.
For myself, the graphs I have seen don't seem to show much difference between the two entities, but like always, we can always
find a chart that agrees with our personal view of things. You have to decide for yourself what you believe. I hope if you took the
time to read all of this you learned something from it that will be helpful to you in your search for an engine. Statistics really don't
mean a darn thing unless its your airplane that has an engine quit. So if you choose to proceed wisely or blindly, its your choice.
ekimneirbo
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