FFS. I need a new hobby.

They have a case that can be reconditioned to the k1g5d spec.
You’re getting a new case to get the traditional two mags and dump the single dual mag system you currently have? Unrelated to the set screw propeller problem.
 
You’re getting a new case to get the traditional two mags and dump the single dual mag system you currently have? Unrelated to the set screw propeller problem.
No. The D at the end of the model means dual mag.
 
You’re getting a new case to get the traditional two mags and dump the single dual mag system you currently have? Unrelated to the set screw propeller problem.
Neal has it. Sticking with the g5d. Going to a g5 would require sourcing another crank, accessory case, and a bunch of gears. Maybe the cam, too, id have to look. Decided to pursue speed and cost rather than the upgrade. I know all those parts are good on my engine.

Id like to move to a Seneca in a couple years anyway. Because doubling the number of aircraft engines in my life seems like a good idea :rolleyes:
 
Ah / so you’re fairly convinced your current case got damaged with the latest kerfuffle
 
Ah / so you’re fairly convinced your current case got damaged with the latest kerfuffle
There's some scarring in the bore where the shaft lives. Since the shaft isn't supposed to spin, it'd likely be fine, but I'd hate to get it apart and find it's out of spec and has to be worked over, then have to wait for that. Also, the threads in the plug hole are flattened. Again, probably okay, but but one less thing to worry about, as is the set screw hole, which is clearly deformed to some extent. Finally, there's that niggling doubt in the back of mind that Chris is right and there's something wrong with the case....

Fresh, clean case gives loctite and staking the best chance of not having this happen again. I think my mechanic will feel better about having the reconditioned case as well.
 
The ride of any rotational hardware connected to or driven by the rear end of a crankshaft that has a flywheel/propeller at the other end, is a complicated analysis situation of a hellish environment. There is a lot of torsional vibration at the rear of a crankshaft of any multi-cylinder piston engine, in the low hundreds of hertz frequency, at various harmonics of the firing frequency. Design games are frequently played with 2 or more swinging harmonic damping weights that effectively operate at an critical radii well under 0.100 inch. These pendulum weight systems are tuned to absorb some or most of the harmonic resonant frequencies. This is especially important for an aircraft engine since it always runs at the same rpm for hours, which just might happen to be an otherwise bad rpm. The actual damping system frequency performance will be severely compromised with just very minor variations in the dimensions of the bushings and pins that determine the harmonic absorption. If that torsional damping system is out of tolerance, strange fatigue failures can be expected. The dual mags, the oil pump, and whatever else (like the prop governor and its drive gear system) is connected to the crank rear sees this ringing.

Also, suspicious is the prop governor (which I presume includes a gear boost pump) creates another hydraulic ripple in the hard line going to the propeller hub.

All the above could reflect into radial loads of the cantilevered shaft retained only by set screws, Loctite, or roll pins, none of which are really appropriate for nigh-cycle fatigue.

Whatever, assuming this is a one-of failure (which I doubt) the harmonic damper system should be considered guilty until proven innocent.
 
Glad you didn't have to bring this one in with the oil spray.

I'm going to be a jerk about this one. Not to OP, but to the mechanic. I'm not a lawyer, but do work a bit with them every day. To me, if the mechanic followed the manufacturer instructions, then it would be a warranty issue. But the statement "I don't follow the service instructions", to me, is the same as saying "I'm designing this repair method". I'd sue the guy even if an attorney wouldn't take it on contingency. Just to get the guy to say "yeah, I left out the Loctite because my method is good enough". It's not possible to convene a jury in the United States where at least one member doesn't know what Loctite is. Or what following the f&*&ng directions means.

I'm being a jerk because, from my understanding, this guy ignored the directions, installed the part wrong, and could have killed your family. The 20k hurts, but the alternative would be unforgivable. Guy should not be turning wrenches.

If a mechanic is going to deviate from the rules, they need to get the OK from the poor SOB that's going to be flying the aircraft, at a minimum.
 
“Id like to move to a Seneca in a couple years anyway. Because doubling the number of aircraft engines in my life seems like a good idea”

Judging by your Avatar, seems like that works for kids as well! :)

Glad to hear a way forward has emerged. :fcross:
 
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The ride of any rotational hardware connected to or driven by the rear end of a crankshaft that has a flywheel/propeller at the other end, is a complicated analysis situation of a hellish environment. There is a lot of torsional vibration at the rear of a crankshaft of any multi-cylinder piston engine, in the low hundreds of hertz frequency, at various harmonics of the firing frequency. Design games are frequently played with 2 or more swinging harmonic damping weights that effectively operate at an critical radii well under 0.100 inch. These pendulum weight systems are tuned to absorb some or most of the harmonic resonant frequencies. This is especially important for an aircraft engine since it always runs at the same rpm for hours, which just might happen to be an otherwise bad rpm. The actual damping system frequency performance will be severely compromised with just very minor variations in the dimensions of the bushings and pins that determine the harmonic absorption. If that torsional damping system is out of tolerance, strange fatigue failures can be expected. The dual mags, the oil pump, and whatever else (like the prop governor and its drive gear system) is connected to the crank rear sees this ringing.

Also, suspicious is the prop governor (which I presume includes a gear boost pump) creates another hydraulic ripple in the hard line going to the propeller hub.

All the above could reflect into radial loads of the cantilevered shaft retained only by set screws, Loctite, or roll pins, none of which are really appropriate for nigh-cycle fatigue.

Whatever, assuming this is a one-of failure (which I doubt) the harmonic damper system should be considered guilty until proven innocent.
The only harmonic dampening system I'm aware of is the crankshaft counterweight system. What more can one do beyond replacing the bushings as Lyco requires whenever the engine is opened? I've been considering sending the rotating assembly out to be balanced, although I'm not sure how much this will achieve as it was balanced by the original builder and none of the parts have been changed.

FWIW, this governor setup is on the front of the engine. After the initial occurrence I had the prop and governor overhauled for fear that one of them might have contributed to the failure.

Glad you didn't have to bring this one in with the oil spray.

I'm going to be a jerk about this one. Not to OP, but to the mechanic. I'm not a lawyer, but do work a bit with them every day. To me, if the mechanic followed the manufacturer instructions, then it would be a warranty issue. But the statement "I don't follow the service instructions", to me, is the same as saying "I'm designing this repair method". I'd sue the guy even if an attorney wouldn't take it on contingency. Just to get the guy to say "yeah, I left out the Loctite because my method is good enough". It's not possible to convene a jury in the United States where at least one member doesn't know what Loctite is. Or what following the f&*&ng directions means.

I'm being a jerk because, from my understanding, this guy ignored the directions, installed the part wrong, and could have killed your family. The 20k hurts, but the alternative would be unforgivable. Guy should not be turning wrenches.

If a mechanic is going to deviate from the rules, they need to get the OK from the poor SOB that's going to be flying the aircraft, at a minimum.
Been thinking about that. I'm going through the service letter list myself right now, and I'm beginning to understand how easy it would be to miss one. That said, the Lycoming overhaul manual still refers to the "spring pin", which no longer exists, so you'd think that'd cause someone following the manual to go looking. When I realized that his charge was 11K, not 20 (that included the R&R & prop), I decided it wasn't worth pursuing, but I tend to agree with your assessment. It seems like the whole point of sending the engine work out is to get it to an expert who wouldn't miss stuff like this. I am looking forward to opening the case and getting a good look at the screw area, and particularly seeing if there's any loctite in there.
With his current and future needs, probably should just get something more “future proof”.

View attachment 134544
Yeah, in all honesty I can't afford an airplane big enough to cart everyone comfortably. A twin commander, a 414, a Navajo. The oldest is 16, so I'm looking forward to kicking her butt out of the house, which frees up a seat.
 
Yeah, in all honesty I can't afford an airplane big enough to cart everyone comfortably. A twin commander, a 414, a Navajo. The oldest is 16, so I'm looking forward to kicking her butt out of the house, which frees up a seat.
She's old enough to solo. Just get another plane. What's the difference? Still 2 engines to maintain.
 
But the statement "I don't follow the service instructions", to me, is the same as saying "I'm designing this repair method".
I believe the quote was “We don’t do SI’s unless specifically requested but do the AD required.” So I don’t find where he designed his own repair method or deviated from the rules. Perhaps he used a different OEM reference for the work? But its tough to make a complete assessment without the shop here to give their side. Regardless, I think the OPs current plan is one that I would have also recommended based on what has been posted so far.
 
I believe the quote was “We don’t do SI’s unless specifically requested but do the AD required.”
Help me out here

In order of priority you have
• Service Information Letter
• Service Bulletin
• Special Airworthiness Information Bulletin
• Airworthiness Directive


While legally you’re only required to do the AD, wouldn’t any one of these supersede the original service and repair manuals?

What reason is there, what is the benefit to skip any of these?
 
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<SNIP>

Yeah, in all honesty I can't afford an airplane big enough to cart everyone comfortably. A twin commander, a 414, a Navajo. The oldest is 16, so I'm looking forward to kicking her butt out of the house, which frees up a seat.

Maybe 8 or 9 years...
 
While legally you’re only required to do the AD, wouldn’t any one of these supersede the original service and repair manuals?
Depends. First some context. Each AD is an actually a new regulation that revises Part 39 and everyone must comply them. A SAIB is for informative purposes only and has the least priority even below ACs, SBs, and SLs. OEM documents are optional unless required by a regulation. For example, if an SB is called for in an AD, Part 39.xxxxx makes the SB mandatory, or if the OEM issues an Airworthiness Limitations Section, then 43.16 and 91.403 make the ALS mandatory for everyone.

As to superseding the original service manuals, the guidance defines that the service manuals used when performing maintenance only need to be current as of the date the aircraft was manufactured. And in some cases, using the latest revision of a mx or parts manual on an older aircraft may actually cause more grief than needed.

What reason is there, what is the benefit to skip any of these?
It is strictly up to the owner whether they want to comply with OEM recommendations and bulletins. And you’ll find a number of Part 91 private owners tend to lean toward not following those OEM items mainly due to cost and no real bang-for-buck to their operation.

From my standpoint, I usually recommend a combination of the regulatory minimum requirements and various OEM recommendations to build a solid foundation for maintaining the aircraft. However, there are private owners who do follow all OEM recommendations to include using the OEM inspection guidance and all OEM bulletins. So basically the decision is very subjective to the owner and where they want to be with their aircraft. If that makes sense.
 
And you’ll find a number of Part 91 private owners tend to lean toward not following those OEM items mainly due to cost and no real bang-for-buck to their operation.

Agreed, and some consideration also has to be given to the possibility of maintenance-induced failure. Complying with some SBs may risk creating a new problem, possibly one that's worse than what the SB is addressing.
 
Ye gads - so how does one decide which ones to do? Such as whether to use locite on a propeller control set screw.
 
Ye gads - so how does one decide which ones to do? Such as whether to use locite on a propeller control set screw.

You'll learn a lot from type clubs, type experts, and experienced A&Ps. (Not to mention NTSB reports. :devil: ) And POA, of course. Can't forget POA.
 
At least our old airplane engines were designed and built to be repairable. :(
Anything is repairable, and more appropriately economically viable for repair, if you ensure the cost of its replacement is even higher.
 
Anything is repairable, and more appropriately economically viable for repair, if you ensure the cost of its replacement is even higher.
Maybe…but if you don’t make parts or manuals available, it makes the cost of repair pretty high.
 
Agreed, and some consideration also has to be given to the possibility of maintenance-induced failure.
I’ve always found this to be an interesting concept: don’t perform maintenance due to the chance the mechanic will FU. Its been my experience that if an owner is proactive, using qualified mechanics, they will always end up way ahead of all MIF concerns.

Complying with some SBs may risk creating a new problem, possibly one that's worse than what the SB is addressing.
Depends on the bulletin. I’ve found that in most cases where the bulletin has you looking for a certain condition, you’ll end up finding that condition or something else similar. What I think is more important is to at least address the topic of bulletin vs dive in head first just because.

Ye gads - so how does one decide which ones to do? Such as whether to use locite on a propeller control set screw.
Depends on what the maintenance request is. For example, if an overhaul then most OEMs require all applicable bulletins to be complied with in order to sign off an OH. However, with IRAN work there can be too many variables to give a specific answer. Any guess how many bulletins could be affected by splitting a case? As to the Loctite question, what if the shop used an alternate OEM document that covered the work performed, but it did not include the use of Loctite as in the other document?
 
I’ve always found this to be an interesting concept: don’t perform maintenance due to the chance the mechanic will FU.

Having seen a few A&P screw-ups, and having practiced engineering in aerospace for decades and seen a number of technician-induced failures, I can assure you the concept is not only interesting, it's valid.

Remember this one, from just a few months ago? https://www.pilotsofamerica.com/com...-save-in-a-grumman-aa-1c.147421/#post-3523218 The mechanic was complying with an AD (so there was no option to skip it), and could have killed the pilot by botching the installation of the crankshaft plug. The failure the AD inspects for is extremely rare; in fact, the only documented failures can be traced to prop strikes. But compliance introduces the opportunity for a disastrous failure.


Depends on the bulletin.

Certainly! But maintenance-induced failures are real and should be considered.
 
The only harmonic dampening system I'm aware of is the crankshaft counterweight system. What more can one do beyond replacing the bushings as Lyco requires whenever the engine is opened? I've been considering sending the rotating assembly out to be balanced, although I'm not sure how much this will achieve as it was balanced by the original builder and none of the parts have been changed.

FWIW, this governor setup is on the front of the engine. After the initial occurrence I had the prop and governor overhauled for fear that one of them might have contributed to the failure.
My Bad! - I did not fully understand the governor location...but on review, the camshaft is actually driven by the back of the engine so torsional vibration at the rear could just be compounded by the camshaft windup to make a still worse torsional vibration environment at the governor. Much depends on Lycoming doing their sums correctly during the design, and seems to this MechEngr that they were getting painted into a corner simply with the requirements.

You are correct that the only vibration dampers (also called dynamic absorbers) are the so-called "counterweights", but their function is not traditional balancing or even smooth engine operation. Rather they are to suppress torsional vibration in the crank-propeller system. Torsional vibration is weird stuff in that it doesn't make noise or jiggle your seat etc, but rather stresses hell out of things by silently but dynamically torqueing (winding) them up. It can stress big iron stuff like the crankshaft to the point of fatigue induced fracture. In most applications it does not displace any air and that is why it can be so silent - but it still is a silent fatigue killer. My 150 hp 172M had no damper system in it but I could actually hear a torsional vibration ringing (about middle C on a piano) when operating near 1900 rpm. Apparently that mild 4 cylinder engine didn't generate enough dynamic torque and of course was rarely operated at that rpm that it wasn't felt necessary from a design standpoint. That same engine being simply upgraded to 180 hp got into needing dynamic absorbers in many models. Virtually all aircraft 6 cylinder engines have dynamic absorbers except the older O-300 Continentals, which interesting enough used absorbers in the latest "O-300D" series.

The tuning frequency(s) of these absorbers is determined by the diameter differences in each sleeve/pin assembly. The assembly manual describe how to measure these respectively and should be rechecked carefully.

FWIW - I have engineered spinning torsional vibration test systems for car drivelines, but my initial experience (I'm 86 now) was using the same technique to control sway in high rise buildings. The principles are the same. o_O
 
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But maintenance-induced failures are real and should be considered.
Mechanic errors are one thing. But not scheduling a SB due to the “opportunity” for mechanic error is something completely different which is the interesting part. Or maybe I’m just not following your point? Perhaps give a specific example of where you would not have an SB performed due the chance of a mechanic error?
 
Or maybe I’m just not following your point? Perhaps give a specific example of where you would not have an SB performed due the chance of a mechanic error?

My point is simple. SBs are optional. When considering complying with a SB, one should consider the possible consequence of not complying versus the amount of dissassembly and reassembly required and the opportunity for inducing a failure, as well as the possible consequence of that induced failure. One might also consider delaying a SB until some type of mandatory maintenance requires the dissassembly anyway, rather than creating two separate opportunities to induce a failure.

All maintenance introduces a possibility of a mistake that causes a failure. Unneccessary maintenance therefore introduces an unneccessary possibility of a mistake. I'm simply suggesting that an owner consider whether the risk of doing the maintenance action is worthwhile.

In the short time I've owned my plane, I have not had to make a decision whether to comply with a SB or not. Given a choice, I might decide not to comply with the crankshaft AD, as the probablility of having a failure is negligible, whereas the probably of a mechanic-induced failure is less negligible. The FAA has taken that decision away from me, though.
 
I'm simply suggesting that an owner consider whether the risk of doing the maintenance action is worthwhile.
You'll find the higher risk is usually in not performing the mx action vs how that action is performed by the mechanic. Mechanic error is not caused by the task, but by the improper performance of the task. And those 2 points are not directly connected. And since a number of SBs, SLs, etc are usually preventative in nature, delaying the task compliance is what causes a higher "failure" rate.

For example, years ago Piper came out with SB 1006 to pull the fuel tanks and check the spar for corrosion. A lot of discussion went on about collateral damage issues of pulling the tanks just as you mention. Some wanted to wait till the recommended 7-year date. Some didn’t think it was worth the "risk." I and others recommended at the next annual regardless of calendar time. Of 2 aircraft that had it complied with at next annual, both had corrosion but were repairable. Key part.

So in the context of Post 177, and in my experience of performing these mx tasks, you'll be money ahead to make the topic of the SB or mx task paramount vs the potential issues in having the task complied with. Regardless, it’s your call as owner, but if mx error is a concern, simply hire better mechanics.
 
I believe the quote was “We don’t do SI’s unless specifically requested but do the AD required.” So I don’t find where he designed his own repair method or deviated from the rules. Perhaps he used a different OEM reference for the work? But its tough to make a complete assessment without the shop here to give their side. Regardless, I think the OPs current plan is one that I would have also recommended based on what has been posted so far.
I read it as there was a specific written repair method documented for this problem, and that the mechanic explicitly chose to not follow that procedure. I absolutely could have misunderstood it. If he invented his own method to effectively re-design a part on a certified aircraft, I'll stand by recommendation, though. AFAIK, modifying part of the power system isn't something to be taken lightly.

Completely agree about their being two sides to the story, but in this case the OP is someone that always seems level headed, and I'd say seems to be in this circumstance, too.
 
Just curious, do you do regular oil sampling analysis. With that much scoring I would have expected it to show up in the oil
 
Just curious, do you do regular oil sampling analysis. With that much scoring I would have expected it to show up in the oil
That's a great question. Yes, I do. Looking back, I see my iron number is above "universal averages", but no so much that I or the analyst ever paid attention to it. Makes me question the value of oil analysis.

oil anal.jpg
 
But that part of the shaft doesn't get any oil right?
 
But that part of the shaft doesn't get any oil right?
As I understand it, not directly, but there is an oil supply for the gears & their bushings. I believe the shaft intersects an oil galley because when the first one popped out, oil pressure dropped to almost nothing and it pumped the oil out through the hole within a minute or so. There should be more than enough oil moving around there to flush the metal into the sump. Never found any ferrous chunks in the filter either.
 
As I understand it, not directly, but there is an oil supply for the gears & their bushings. I believe the shaft intersects an oil galley because when the first one popped out, oil pressure dropped to almost nothing and it pumped the oil out through the hole within a minute or so. There should be more than enough oil moving around there to flush the metal into the sump. Never found any ferrous chunks in the filter either.

When is that analysis from? Several things to consider:
1. Any wear on the set screw may not have started or was just beginning.
2. The wear may have been minimal.
3. There is/was no wear on the set screw that invaded the oil system.
4. The set screw is a red herring for the iron levels.
5. Any of the above in various combination.
 
When is that analysis from? Several things to consider:
1. Any wear on the set screw may not have started or was just beginning.
2. The wear may have been minimal.
3. There is/was no wear on the set screw that invaded the oil system.
4. The set screw is a red herring for the iron levels.
5. Any of the above in various combination.
The most recent is from March of this year. The set screw and shaft didn't lose much metal, but that cap.... It's steel. The shaft removed at least .080 of material based on the height of the last remaining thread. I'm guessing it was more than that, but I don't have a new cap to compare it to.
 
The most recent is from March of this year. The set screw and shaft didn't lose much metal, but that cap.... It's steel. The shaft removed at least .080 of material based on the height of the last remaining thread. I'm guessing it was more than that, but I don't have a new cap to compare it to.
Send the current oil off to Blackstone for oil analysis and see what comes up. I'm wondering if because your engine has had unit averages for Iron near 46-48 at points in the past, it doesn't raise alarms despite being above universal averages. Also not sure if their universal averages are specific to your engine model or all piston-GA models. It would be interesting to know what data set it uses to show the universal averages.
 
Yeah, current oil might have shown different results, but obviously not useful for prediction.

If you had used AeroShell, this would have never happened :p
 
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