Tach Time?

I've actually seen numerous Lycoming O-360s make it well past TBO.
Mike does not say don't overhaul. What he says is to use conditional based maintenance verses time based maintenance. Conditional based maintenance has been used for years by 121 carriers while using time based maintenance introduces the "Waddington Effect".
I saw this effect first hand in the military where we insisted on doing phases on the UH-60 every 500 hours, even if there was nothing wrong with the aircraft. Inevitably an aircraft would be in great shape going into phase yet would come out an absolute dog due to the number of man hours involved in doing a phase and the corresponding inevitable human error introduced.
So far every response has been what people feel verses actual numbers and statistics involved in exceeding TBO. I present actual numbers- the most dangerous engine is that which has just been installed.
 
BTW, last I checked Cape Air was approved for running their engines past TBO and was averaging 3000 hours between overhaul. That is about the average of what I saw on the -360 series engines in flight school environments, hardly an environment that is ideal for engine wear (aside from the frequent flying).
 
Blackhawk said:
So far every response has been what people feel verses actual numbers and statistics involvedinexceeding TBO.
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What I see is an opinion from an avweb author and an opinion from an aopa author (link actually says opinions in it). These opinions based on the stats/numbers they've seen; hardly all inclusive. And I see Rogers opinion based on what he's seen. Also stats and also not all inclusive.

I'd be interested to know what insurance companies would say if you balled it up after an engine failure 50 percent past tbo. Also what do the manufacturers say is acceptable. Just because something happens isn't proof of whether or not it should happen.
 
shdw said:
What I see is an opinion from an avweb author and an opinion from an aopa author (link actually says opinions in it). These opinions based on the stats/numbers they've seen; hardly all inclusive. And I see Rogers opinion based on what he's seen. Also stats and also not all inclusive.

I'd be interested to know what insurance companies would say if you balled it up after an engine failure 50 percent past tbo. Also what do the manufacturers say is acceptable. Just because something happens isn't proof of whether or not it should happen.
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The opinions I included are based upon stats and numbers.
Insurance companies could care less about TBO and have never turned a claim that I am aware of. Please cite the court case where this has occurred in the US. You won't find one.
Manufactures don't say squat about exceeding TBO. If anything the opposite. From TCM:

"NOTE: The TBO's provided in this Service Bulletin are only estimates..."
 
Blackhawk said:
BTW, last I checked Cape Air was approved for running their engines past TBO and was averaging 3000 hours between overhaul. That is about the average of what I saw on the -360 series engines in flight school environments, hardly an environment that is ideal for engine wear (aside from the frequent flying).
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That's great for cape air, they have a fleet of 80+ airplanes running the same engines under the same conditions and the same maintenance program and the ability to prove statistically to their powers that be that it is safe. Few piston engine operators have that (I'm sure my FSDO would be very accommodating if I showed up with a proposed revision to our D101 showing a TBO double what TCM recommends based on "well this one engine we just pulled seemed to be doing alright, and a couple dudes on the internet say it'll be fine").

Also, comparing the Lyc 360 with a TCM 520 like what I deal with is apples to oranges. The Lyc is a fairly bulletproof, dead simple little motor that is pretty overbuilt. The 520 is a piece of garbage (at least the model of it that I am familiar with). I'm curious how many of 9K's 520s actually make it to that 3000 TBO they are allowed to use, and what kind of man hours, aircraft down time, and parts they put into them along the way (I'm guessing they wind up doing cylinders and turbos at least twice along the way). Because they have a big fleet and have things figured out, again, I'm sure it works for them but for a small operation? I remain skeptical.
 
Roger Roger said:
That's great for cape air, they have a fleet of 80+ airplanes running the same engines under the same conditions and the same maintenance program and the ability to prove statistically to their powers that be that it is safe. Few piston engine operators have that (I'm sure my FSDO would be very accommodating if I showed up with a proposed revision to our D101 showing a TBO double what TCM recommends based on "well this one engine we just pulled seemed to be doing alright, and a couple dudes on the internet say it'll be fine").

Also, comparing the Lyc 360 with a TCM 520 like what I deal with is apples to oranges. The Lyc is a fairly bulletproof, dead simple little motor that is pretty overbuilt. The 520 is a piece of garbage (at least the model of it that I am familiar with). I'm curious how many of 9K's 520s actually make it to that 3000 TBO they are allowed to use, and what kind of man hours, aircraft down time, and parts they put into them along the way (I'm guessing they wind up doing cylinders and turbos at least twice along the way). Because they have a big fleet and have things figured out, again, I'm sure it works for them but for a small operation? I remain skeptical.
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The last part of what you wrote summarizes the fact that you have no idea what conditional based maintenance is. Cape Air was not given a TBO of 3000 hours, they were operating under conditional replacement which requires such things as regular oil analysis, filter and screen examination at each oil change and operating the engines for maximum life. This is a much more scientific method than that used by the manufacturers to determine TBO. In spite of what you and others might think they pretty much SWAG it.
 
Blackhawk said:
BTW, last I checked Cape Air was approved for running their engines past TBO and was averaging 3000 hours between overhaul. That is about the average of what I saw on the -360 series engines in flight school environments, hardly an environment that is ideal for engine wear (aside from the frequent flying).
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Cape Air runs their airplanes in a way that is ideal for maximum engine life. The average GA pilots does the exact opposite.
 
Blackhawk said:
The last part of what you wrote summarizes the fact that you have no idea what conditional based maintenance is. Cape Air was not given a TBO of 3000 hours, they were operating under conditional replacement which requires such things as regular oil analysis, filter and screen examination at each oil change and operating the engines for maximum life. This is a much more scientific method than that used by the manufacturers to determine TBO. In spite of what you and others might think they pretty much SWAG it.
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I'm fairly certain they got a TBO approved based on evidence they were able to present to their FSDO. I don't know about where you have been, but like I said my FSDO won't just sign any old numbers in D101 and I doubt that capes folks are any different. I respect your input in most matters but it's clear from this and from the last time we discussed anything mx related that you have a pretty high opinion of your maintenance knowledge, maybe higher than what it should be.
 
@Blackhawk, I wish conditional based maintenance/statistical process control were more widely used in maintaining equipment (not just aircraft engines, but most any kind of equipment). Long ago I worked in the manufacturing sector, and we would see wide swings in the tolerances of the parts we were manufacturing. We learned about statistical process control (SPC) and implemented it. We found that our routine equipment maintenance was causing much of the variability in the tolerances of the parts we were manufacturing. By replacing the scheduled maintenance program with one based on SPC we were able to reduce the tolerances (a desirable thing) and reduce the maintenance workload (also desirable).

SPC is a great way to identify changes that are indicative of pending failures. All aircraft maintenance facilities gather the data that can be used in SPC, but they don't realize it, and the data go unused.

@Roger Roger , my employer operates a large number of IO-520s, and they seem to do pretty well. None of our mechanics exhibit the disdain for them that you do. Maybe it's a matter of differences between models, the conditions in which they are operated, or the way they are operated. On ours, common problems are starter adaptor drives and alternator failures (belts off pulleys and voltage regulators seem to be the most common). Cylinder changes do occur from time to time, but I don't have a good gage on how often they occur - it's not like they happen all the time.
 
So ILL said:
Thanks that's a real eye opener. I didn't know tach time could be so cryptic. The reason I ask is the cessna may be available through a family friend but I only had time so swing by the airport and look inside. I was wondering about engine time before next overhaul was due.
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When you look at logbooks be sure to look at what year the engine was installed as well and find out how often the airplane has been flying. Airplanes that have been sitting, both recently and in general over a long period of time can end up costing you way more than you might anticipate. From my perspective I would rather have and engine within a few hundred hours of TBO than an engine with 300 hours but that's been 25 years since overhaul. Just be careful what you're buying and get some eyes on it that know a lot about it.
 
Plata said:
@Blackhawk, I wish conditional based maintenance/statistical process control were more widely used in maintaining equipment (not just aircraft engines, but most any kind of equipment). Long ago I worked in the manufacturing sector, and we would see wide swings in the tolerances of the parts we were manufacturing. We learned about statistical process control (SPC) and implemented it. We found that our routine equipment maintenance was causing much of the variability in the tolerances of the parts we were manufacturing. By replacing the scheduled maintenance program with one based on SPC we were able to reduce the tolerances (a desirable thing) and reduce the maintenance workload (also desirable).

SPC is a great way to identify changes that are indicative of pending failures. All aircraft maintenance facilities gather the data that can be used in SPC, but they don't realize it, and the data go unused.

@Roger Roger , my employer operates a large number of IO-520s, and they seem to do pretty well. None of our mechanics exhibit the disdain for them that you do. Maybe it's a matter of differences between models, the conditions in which they are operated, or the way they are operated. On ours, common problems are starter adaptor drives and alternator failures (belts off pulleys and voltage regulators seem to be the most common). Cylinder changes do occur from time to time, but I don't have a good gage on how often they occur - it's not like they happen all the time.
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Usually people who "like" working on gold colored engines are suffering from Stockholm syndrome because that's all they've ever done.
 
ATN_Pilot said:
Cape Air runs their airplanes in a way that is ideal for maximum engine life. The average GA pilots does the exact opposite.
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I agree that this is part of the problem, but there is also the problem of many GA pilots buying into the "more maintenance is better" crap. Kind of like some people who buy into "more medicine is better" crap. As the wife of a highly respected orthopeadic surgeon, I can tell you surgery is the last option she leaves on the table, not the first. She would never replace a hip or knee due to TBO, but would do so due to "condition based maintenance" after all other options were exhausted. In the same respect too much maintenance just introduces the error-prone human element into aviation.
And BTW, I'm not unfamiliar with the TSIO-520, having been the CP for a 135 company that operated 210s and 310's equipped with them. We also had permission to operated them past TBO using conditional based maintenance. We never had the issues with them described by others even though operating in the desert Southwest, not exactly the most forgiving place.
 
Blackhawk said:
The opinions I included are based upon stats and numbers.
Insurance companies could care less about TBO and have never turned a claim that I am aware of. Please cite the court case where this has occurred in the US. You won't find one.
Manufactures don't say squat about exceeding TBO. If anything the opposite. From TCM:

"NOTE: The TBO's provided in this Service Bulletin are only estimates..."
Click to expand...

The insurance companies don't care,

the plaintiff's lawyers however...
 
Roger Roger said:
Usually people who "like" working on gold colored engines are suffering from Stockholm syndrome because that's all they've ever done.
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I mean, to be fair Roger your first experience with an IO520F was in 51, right? That may be enough to give anyone heartburn, lol.

Honestly, the IO520F model is still my favorite piston engine I've flown.
 
Put me down firmly in the "don't open it up unless there is a problem" camp. I honestly would never split the case of an engine unless metal started showing up in the oil. The only thing splitting the case does is allow you to inspect the bearings, which if there is no metal in the oil should be fine. If a cylinder has bad compression, then that cylinder gets replaced.

The average TBO for the average american male's heart is 55 years. Would you schedule yourself for open heart surgery because you are 60 years old, despite a history of clean EKGs, normal BP, and no family history?

I knew a guy who flew pipeline patrol in a 172 with 8000+ hours on it. He flew the plane virtually every weekday, monitored the oil with every change, and knew exactly what power it should be putting out.

Mike Busch's argument that engines are most dangerous during the "infant mortality" phase is compelling.
 
ppragman said:
I mean, to be fair Roger your first experience with an IO520F was in 51, right? That may be enough to give anyone heartburn, lol.

Honestly, the IO520F model is still my favorite piston engine I've flown.
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Worked on a few more and the 550 since then. Still hate em.
 
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