TBO question

[74657]

Im within 100 hours of TBO on the IO-550 in my Missile.  Compressions are all mid-high sixites and low 70's COLD.  Uses 1 qt. every 8 hours.  How many of you guys run past TBO?  This is a 40K expenditure that I am not looking forward to having to do in the next year.  I've read articles that go both ways....  Whats the Mooneyspace consensus?

 

 

[Magnum]

Just depends on what your comfortable with.  Personally I usually don't have any problem with it.  I'd change the oil at least every 50hrs if not more and check the screens and filters.  Very very few engines will go without ample warning.  Do you have an engine analizer? The engine and airplane talk to you, if you listen and pay attention there will be very few major surprises.  Do you fly hard IFR or a lot at night or over very unforgiving terrain?  Would you be comfortable with a forced landing if you didn't see or pay attention to the signs?  All things to take into consideration.  Turbo charged engines usually give less time before problems can occur but there are usually still signs.  Low compression and contaminated oil usually happen quite a bit before catostraphic fialures.  Just my 2 cents worth since you asked.

Kendal

 

[74657]

The engine oil has been changed every 25-40 hours since new.  Oil analysis has always come back good.  It has a JP 700 monitor.  I'm just making sure Im not talking myself into a potentially dangerous situation.

[Cruiser]

Not familiar with the IO-550 but if the engine is running good, compression, oil analysis, oil consumption, leaks, vibrations etc are all normal I would keep going.

 

[Piloto]

One good indication for time for an engine overhaul is the oil pressure at idle with the engine warm. If the pressure drops below the green arc the bearings are likely due for replacement within the next couple hundred hours. If the oil comsumption is low, good compression and good oil pressure leave it alone until one of these parameters is out of range.

José

  

[mooney231]

Oil changes every 25 - 30 hours with good oil analysis results, good compression checks, and appropriate oil consumption may lead you well past TBO.  I have a friend who is currently 400 hours over TBO on his IO-360 with some engine TLC and oil changes every 25 hours and compression checks every 50.  Definitely possible with good engine care and maintenance.

[GeorgePerry]

I'd keep flying it as long as the oil analysis and compressions are good - but if you don't already have one, start putting AMU's into an overhaul fund.  If and when it is time to get the motor done, take a look at JB Engines.  They have a good reputation and their prices are very competative.

http://www.jbaircraftengines.com/

[DaV8or]

Since the prevailing opinion here so far and on the AOPA forums seems to be run it until it won't run no more, I thought I might offer an opposite view point. I consider the TBO to be sort of the engine's annual. It's about getting inside and see all that is going on, or has gone on. Do we really need to annual an airframe once a year? Has anyone ever taken their well maintained airframe in for annual thinking they are going to ace it for sure, only to have the mechanic say, "come here, there's somthing I have to show you"? Engine annalysers, oil annalisis and oil changes can't tell you when something is about to crack and break. Your engine won't talk to you and tell when the cylinder is about to depart the block. There are way too many stories out there about sudden engine breakage for me to be all warm and fuzzy about my latest oil annalisis.

Something to consider might be, how many hours does the engine have in total time, not just the last rebuild. The high stress of an airplane engine combined with the wide temperature ranges does bad things for aluminum. The more cycles the worse. The manufacturer and the FAA don't feel comfortable raising the TBO, I'm sure they have their reasons.

Finally, do you fly mostly by yourself, or with friends and family?

[danb35]

Quote: DaV8or

Since the prevailing opinion here so far and on the AOPA forums seems to be run it until it won't run no more, I thought I might offer an opposite view point.

[airbusflyboy]

Changing gears ............... How about your Aircraft Insurance ? If you run the engine past TBO and have a problem, are they going to pay for it or some of it ? There is some kind of discussion on the web with stats on engine failures at various engine times levels, might be worth a search and check it out ............. ???

[tony]

I would heed Jose's advice.  I wouldn’t put much faith in oil samples or compressions.  As Dan says, a cylinder is just a replaceable part.  What you need to be worried about are the cam, followers, bearings, and crank.  You need to pull the screen and really inspect it, wash it out good with a solvent and look for little tiny pieces.  Run those pieces past a magnet.   Open up the oil filter and do the same.  I would do this on any engine regardless of the time.  What kills an engine faster than anything is non use. 

Personally I feel more comfortable flying in a 2500 hour engine that flies regularly and has been well maintained, than a low time engine that only flies a couple of hours a month.

[RJBrown]

I know cars and airplanes differ quite a bit BUT:

Most current car makers recommend oil change every 5000, or more, some as high as 10,000. They say coolant is "lifetime". The maintenance recommendations are pushed as far out as possible for the car to reach its "TBO" of 100,000 miles. At that point they want to sell a new car they don't want their stuff lasting beyond that. The same car maintained properly will last closer to 300,000 miles. Change oil 2500 and all fluids every 30,000. Most lemons are "made" by their owners.

If, and that is a big word, your oil is changed every 25 hours and you treat the engine carefully and conservatively most will last well beyond TBO. Even a TSIO360LB in a 231 can do it with a LOT of care. That said the original engine in my 231 was replaced at 1200 hour TT and 100 hours after I purchased it. My current 1990 MSE J has 1800 hours and I am considering replacement. Both planes had averaged just under 100 hours per year and were owned by someone else for the majority of their life. On the second plane I had learned not to trust the care of the dreaded DPO. I have the reserve for an engine and every hour I get I consider "free"

TBO is just a number. Maintenance and care are key. Poor care and a hamfisted pilot and you will never make TBO. Meticulous care and a gentle touch will pay off in increased safety throughout the life and some "free" hour near the end.

[acronut]

Quote: Magnum

Just depends on what your comfortable with.  Personally I usually don't have any problem with it.  I'd change the oil at least every 50hrs if not more and check the screens and filters.  Very very few engines will go without ample warning.  Do you have an engine analizer? The engine and airplane talk to you, if you listen and pay attention there will be very few major surprises.  Do you fly hard IFR or a lot at night or over very unforgiving terrain?  Would you be comfortable with a forced landing if you didn't see or pay attention to the signs?  All things to take into consideration.  Turbo charged engines usually give less time before problems can occur but there are usually still signs.  Low compression and contaminated oil usually happen quite a bit before catostraphic fialures.  Just my 2 cents worth since you asked.

Kendal

 

[danb35]

Quote: airbusflyboy

Changing gears ............... How about your Aircraft Insurance ? If you run the engine past TBO and have a problem, are they going to pay for it or some of it?

[Magnum]

The insurance shouldn't be a problem. The aircraft has to be in an airworthy condition and for most of us TBO is only a recommendation. When the aicraft passed the annual (even well beyond TBO) it is airworthy.

A friend of mine had a prop strike with a 1800 TSO engine (IO-360). Calendar time was well above 12 years. He wasn't sure if he should make an overhaul, compressions were good and all cylinders were replaced approx. 500-800 hrs ago. His shop sent him horrible pictures of the inside of the fuel divider, after he saw them he was glad he had the prop strike and did the overhaul. Otherwise he might have lost the engine in the not so far future.

So it all depends. If someone knows his engine, makes oil analysis and flies regularly going beyond TBO shouldn't be a problem. If the engine case wasn't split (or checked with a borescope) for more than 12 years I'd go for an overhaul.

My J had less than 700 hrs and 19 years TSO when I bought her. But the engine case was split 2 years before due to a prop strike. It is a much better feeling to know that all important parts were checked for corrosion etc.

[Jeff_S]

It doesn't look like anyone else here has mentioned this, so for comfort I'd point you to Mike Busch's Savvy Aviator webinar series on maintenance issues: http://www.savvymx.com.

He says repeatedly that the TBO of major engine overhaul is simply a bad idea. The primary reason for this is that the most common time for engine failure is in the first few hundreds hours of new or major-overhaul, as the parts all learn to work together under load.  He's got lots of good charts showing historical data showing how the likelihood of major failure as an engine ages decreases for most components.

There are a few components that he DOES suggest should follow a time-based inspection, most notably the magnetos. But most other parts he recommends just watching for the normal signs of wear, as others have noted in these posts. You can go get much more than TBO time out of a well-maintained and well-flown engine, all else being equal.

[Magnum]

Quote: Jeff_S

He says repeatedly that the TBO of major engine overhaul is simply a bad idea. The primary reason for this is that the most common time for engine failure is in the first few hundreds hours of new or major-overhaul, as the parts all learn to work together under load.  He's got lots of good charts showing historical data showing how the likelihood of major failure as an engine ages decreases for most components.

[danb35]

Quote: Magnum

A lot of engines don't make it to TBO because of oil consumption, bad compressions, etc.