What Happens When Your Engine Reaches 0 Hours Left Before Major Overhaul?

[GeneralT001]

Typically it seems that a 4 cylinder IO Lycoming engine has a lifespan of 2000 hrs before a major overhaul is required? What exactly happened when you get to those hours? Is it a mandatory inspection that determines what needs to be "fixed" or do you have to replace the entire engine? Can you get an exemption to fly it longer? What is the cost of a major overhaul for this type of engine??

Curious as I do not have a clue

[EricJ]

Nothing happens.   If you're maintaining it and it's running fine and passing inspection then nothing happens.   Flight schools often get 3000 hours out of Lycoming four cylinders.

[Brian2034]

Currently flying a Piper Warrior 0-320 160 hp. with 2300hrs considered “on condition” in Canada. I’m guessing the same for aircraft engines in the U.S.

We change oil every 50 hours and do oil analysis with the oil changes to monitor the engine.

[GeneralT001]

8 minutes ago, EricJ said:

Nothing happens.   If you're maintaining it and it's running fine and passing inspection then nothing happens.   Flight schools often get 3000 hours out of Lycoming four cylinders.

So you just keep flying until an issue shows up like say low compression numbers?

 

If so then whats the point of the "TBO" number? Also, does going beyond that number effect insurance or do you just need to pass the annual to keep your insurance?

Edited September 19 by GeneralT001

[OR75]

14 minutes ago, GeneralT001 said:

Typically it seems that a 4 cylinder IO Lycoming engine has a lifespan of 2000 hrs before a major overhaul is required? What exactly happened when you get to those hours? Is it a mandatory inspection that determines what needs to be "fixed" or do you have to replace the entire engine? Can you get an exemption to fly it longer? What is the cost of a major overhaul for this type of engine??

Curious as I do not have a clue

I am pretty sure the prop will not stop spinning at 2000.01 

[GeneralT001]

2 minutes ago, OR75 said:

I am pretty sure the prop will not stop spinning at 2000.01 

Understood...but I'm kinda curious if that affects insurance coverage?

[Brian2034]

7 minutes ago, GeneralT001 said:

So you just keep flying until an issue shows up like say low compression numbers?

 

If so then whats the point of the "TBO" number? Also, does going beyond that number effect insurance or do you just need to pass the annual to keep your insurance?

TBO is a number set and recommended by the engine manufacturer 

I believe commercial operators have to adhere to the manufacture.

 

 

[ta2too]

4 minutes ago, GeneralT001 said:

So you just keep flying until an issue shows up like say low compression numbers?

 

If so then whats the point of the "TBO" number? Also, does going beyond that number effect insurance or do you just need to pass the annual to keep your insurance?

In addition to engine hours, TBO also includes calendar years, 12 yrs. is very common. You do not see anybody doing overhauls on time in service though

[1980Mooney]

20 minutes ago, GeneralT001 said:

So you just keep flying until an issue shows up like say low compression numbers?

 

If so then whats the point of the "TBO" number? Also, does going beyond that number effect insurance or do you just need to pass the annual to keep your insurance?

As long as your IA signs offs on your Annual then your plane is Airworthy.  Airworthy is Airworthy - regardless of 2,500 hours on your engine or only 100 hours.  Some would argue that a newly broken in engine is a higher risk than one near TBO due to infant mortality.

However, people have posted here that a buyer cannot get financing on a plane with an engine over book TBO.  I don't know if that is true in all cases.

[EricJ]

38 minutes ago, GeneralT001 said:

So you just keep flying until an issue shows up like say low compression numbers?

Yup.   Part 91 maintenance, and even a lot of Part 121 (airline) maintenance is "on condition", in other words, as long as it is in condition to be serviceable and operate safely you can keep running it.   For some things in different regulatory environments some components are life limited, e.g., many parts on helicopters have to be replaced at the end of the life limit.   For Part 91 operation the TBO "life limit" isn't a limitation.

And to your example of low compression numbers, even then you can just repair or replace the items that caused the issue, e.g., a valve lap, guide, or maybe if you're unlucky a new cylinder, may fix the issue and you can keep running it.

38 minutes ago, GeneralT001 said:

If so then whats the point of the "TBO" number? Also, does going beyond that number effect insurance or do you just need to pass the annual to keep your insurance?

There are some regulatory environments (e.g., carrying revenue passengers), where life limits can matter, so the TBOs are observed for those operators.   Some organizations just choose to observe them as well, like CAP.   For Part 91 they do not need to be observed.   I don't know of any insurance policy that cares about them, either.

There are also some things that muddy the waters, like an engine that underwent an IRAN rather than an overhaul.   Such an engine may have had most things done that would qualify as an overhaul, but not quite all, so it doesn't qualify to be called an overhauled engine.   My engine had an IRAN teardown after the previous owner had a prop strike, that changed all of the main bearings, etc., rehoned cylinders, etc., etc., nearly an overhaul but not quite.   I've put over 800 hours on it since then, and the official "TSMOH" is about 2400.   Still works fine.    As mentioned before, flight schools often run engines to 3000 hours and beyond.   If it is running fine and passing inspection it can be wasteful to tear it down when it still has service life left.

[GeneralT001]

Thanks all....really good info

[Paul Thomas]

20 minutes ago, EricJ said:

As mentioned before, flight schools often run engines to 3000 hours and beyond.   If it is running fine and passing inspection it can be wasteful to tear it down when it still has service life left.

I've often wondered if we are too conservative or if the manner and frequency in which they fly affects TBO.

[201Mooniac]

6 minutes ago, Paul Thomas said:

I've often wondered if we are too conservative or if the manner and frequency in which they fly affects TBO.

I think it is a little of both.  Some owners I know have a hard time accepting that the manufacturers TBO isn't because of extensive testing that shows it will die soon afterwards.  I also think flight schools flying the planes very often eliminate so many issues that are caused by inactivity.  As many here have said, it is better to buy a plane that has been flown often than one that has been sitting.

[AndreiC]

I got the impression from reading other threads (but I may be wrong, and am curious what others think about this) that running an engine way past TBO increased the chances that some expensive parts inside the engine would need to be replaced at overhaul (crank out of machining limits, for example), costing more money to do the overhaul. 

Is this accurate or an old wives tale?

[Paul Thomas]

1 minute ago, AndreiC said:

I got the impression from reading other threads (but I may be wrong, and am curious what others think about this) that running an engine way past TBO increased the chances that some expensive parts inside the engine would need to be replaced at overhaul (crank out of machining limits, for example), costing more money to do the overhaul. 

Is this accurate or an old wives tale?

It can be accurate but one of the flight schools around here just open up a 3500+ hours engine and everything looked good. It's one of those things that just depend. Some engines incur serious damage prior to TBO. Depending on how far past TBO you get, even if you lose expensive parts, you may still be ahead.

[LANCECASPER]

What Happens When Your Engine Reaches 0 Hours Left Before Major Overhaul?

 

You celebrate with a bottle of champagne, wait at least 8 hours and then go flying until the oil analysis or compression check or borescope says to do something.

[Ragsf15e]

It doesn’t affect insurance but does/may affect the ability of a new buyer to finance the airplane.  Different lenders have limits on the % of engine hours / tbo.  I’ve heard 75% or 20 years equals no financing.

[EricJ]

1 hour ago, AndreiC said:

I got the impression from reading other threads (but I may be wrong, and am curious what others think about this) that running an engine way past TBO increased the chances that some expensive parts inside the engine would need to be replaced at overhaul (crank out of machining limits, for example), costing more money to do the overhaul. 

Is this accurate or an old wives tale?

It's easy to blame the additional time when there's wear, but wear doesn't necessarily accelerate past TBO.   I'd vote that it's an OWT.

[BlueSky247]

Dang guys. I clicked on this thread fully expecting someone to have taken a jab along the lines of "It depends on which brand your engine is." 

[cruiserflyer]

General aviation engines don't tend to "wear out" they are more "abused out". Things like not flying often enough, poor maintenance, abusive engine settings, corrosive environments, are what causes engines to not make it to TBO. If properly maintained, flown often, with good engine management skills the odds are you'll go way past TBO with no signs of the kind of trouble that would make you split the case.

[OR75]

there is a good seminar from Savvy about how typically you sense old engines slowly but surely getting tired (less power, more oil consumption, good old noise engine, ...) while new engines are more prone to catastrophic failure.  

so, if I was an insurance company maybe new engines should go with a higher premium !

having said that, what I am seeing with my good old engine - an IO-360-A3B6D about 500 hours past TBO (good compression, no metal in the oil) - is that the accessories start getting tired (governor for example) and the appearance is not so great (chipped paint, some rust points,  ...)  

I do fly it regularly about once a week 

[kortopates]

The vast majority of owner flown aircraft engines suffer from corrosion. It’s really much less about total hours and more about calendar time and infrequent use and how the aircraft is stored between flights.

Flight schools are pretty much the opposite side of the spectrum compared to the infrequent use by the average owner.

Mike Busch is an example of an owner flown engines going over 3500 hrs before overhaul.

Everybody has their opinions though about going past TBO, many shops set a limit where they won’t annual a plane past a certain number of hours past TBO and the DPE’s under my FSDO won’t do a checkride when the engine exceeds 3000 hrs. Yet there is no statistical data to support any of that.


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[Fly Boomer]

8 minutes ago, OR75 said:

having said that, what I am seeing with my good old engine - an IO-360-A3B6D about 500 hours past TBO (good compression, no metal in the oil) - is that the accessories start getting tired

Absolutely right.  Anything that's bolted on may need attention long before splitting the case becomes necessary.  BTW, Mike Busch says he treats cylinders like accessories -- if one is beyond help from a ring flush or lapping a valve in place, then it comes off just like a mag or an alternator. and gets some attention.

[Will.iam]

Engines rust out more often than wear out. The vast majority of people would understand this if they drove their car only once every month and then you would see more rusted out car engines. Or put it another way if people flew as often as they drove their car they would see their engines last like they do in their car. 
so for loan companies what happens if you buy your airplane and a few years later fly past TBO does the loan company then demand payment in full or demand an engine overhaul?

[Hank]

35 minutes ago, Will.iam said:

The vast majority of people would understand this if they drove their car only once every month and then you would see more rusted out car engines. Or put it another way if people flew as often as they drove their car they would see their engines last like they do in their car.

It's shocking how infrequently I drive my car since taking early retirement on 31 May. Poor Carfax keeps telling me that I'm overdue for an oil change, but I still have another 1000 miles to go (I change the oil every 5000 miles in the car and every 50 hours in the Mooney). Guess I'll keep my eyes out for car trouble, but next month I'll have had my truck for 36 months, and it's only got 17,500 troublefree miles. Guess I need more 18 mile trips to the hangar!