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Single engine life hours

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Single engine life hours

Old 20th Apr 2008, 12:03
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Single engine life hours

Hi All,

im in the market for a light single and need some clarification about engine life hours.As i understand it the majority are 2000 hrs tbo.I understand that extensions can be granted i believe in the order of 20% eg 400hrs on a 2000 tbo.Ive seen some a/c with engine hrs above 2400 eg 2600 and advertised as in top order still good compresions etc.So just how long can that go on for.I understand that ide be looking at replacing/overhauling such an a/c pretty soon after purchase,but the question is how long and whats the rulings,or piont me in the right direction for the info please.I understand private and commercial ops would probably be different rules,need the info on how it works thanks for your time people
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Old 20th Apr 2008, 13:46
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Robione,

TBO, represents the manufacturers estimate of an average time between overhauls. It's not a limitation except for commercial operations. An engine may or may not make TBO...it may require overhaul sooner, or it may go far beyond TBO.

An airplane operating privately, in other words not in commercial operations, may be operated "on condition." That means that so long as the engine is in acceptable condition and no life-limitations have been exceeded, the engine may continue to be operated.

TBO really only applies to the first run of the engine...when it's factory fresh, before the first "overhaul." The number applies to subsequent overhauls, but it's premised on starting with all new parts with all new tolerances and clearances met...a factory engine. When an engine is overhauled, it's seldom done by the manufacturer, and very often many components are left in the engine...so long as they're within specification, they may remain in the engine unless they're a life limited component. "Overhaul" means nothing more than the engine has been inspected and found to be in tolerance. Point is...it may not last nearly what the published TBO is.

Bear in mind that expensive accessories such as the magnetos are going to require service before TBO expires...you will go about 600 hours max on a set of mags before they need servicing and overhaul...to engine TBO certainly doesn't show the full picture. Consider the propeller, too...especially a constant speed prop. It's going to have it's own TBO and limitations.

On compression checks; these don't mean a whole lot. A compression check will show different numbers if checked twice in a row, or with two different test sets, or by two different people. Much like blood pressure, it's a tool to look at the life of the engine over a series of checks, as a trend. It's also a spot inspection tool to trouble shoot specific problems (such as a leaking valve)...but the lay person tends to put far too much stock in compression tests. Additionally, the numbers can be artificially bumped up during a pre-sale inspection to make the compression seem higher than it really is. Don't base your decisions around the compression, unless it's unusually low.

The operational history of the airplane is important...look at how often it's been flown, and how. An airplane that gets flown once every six months may not make TBO...sitting is hard on airplanes and equipment...regular operation is benificial to the health of the engine and airplane. Look at the logbooks to see what's been done in the past. A history of multiple cylinder changes, for example, shows that the airplane has probably been abused, and that the maintenance may have been subpar. Check that airworthiness directives have ben accomplished...an engine lacking the updated VAR crankshaft, for example...could become very expensive for you after the fact.

Get a mechanic ("engineer") you trust and invest in a thorough pre-buy inspection. Don't count on getting the full TBO life out of the engine. You may, or you may not, but certainly don't count on it if it's not the first run of the engine. If it's already been overhauled, you may get another good run on that engine...or it may require expensive servicing long before. Be prepared for that. Ask for the oil analysis history if there is one, and get a spectrometric oil analysis done. Good luck.
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Old 20th Apr 2008, 15:21
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engine overhaul

On this side of tha atlantic engine overhauls tend to be mor predictable than in the USA due to the certification required to do the job in the first place, however there are company's that have a good reputation and those that don't.

I wont comment on the bad ones here but a bit of asking around the business will find a few answers.

I have found that running the 20% extention is OK as long as you have a good engine but don't go further than that as you are likely to run into problems with re-using the crankshaft due to bearing wear.
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Old 20th Apr 2008, 16:44
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I have recently done a lot of "due diligence" on engine shops, to get my crank swapped under Lyco's SB569.

The UK engine shop scene is best described as mayhem. At one end you get the good shops some of which many take very long (3-4 months) and at the other end you get some right crooks, including some big firms.

The US engine shop scene is easier to get data on because there are more people reporting; one can read surveys in e.g. Aviation Consumer magazine.

I went to a specialist American engine shop.

Cranks and conrods last a very long time - a number of overhauls. As so many smaller parts e.g. inlet valves.

The best thing is to run an engine regularly (once every 1-2 weeks, or more often), and do oil analysis (send a sample to a lab). In that case, there is no particular significance in the 2000hr figure - other than specific lifed items e.g. the engine driven fuel pump which has a 2000hr life and whose diaphragm will eventually go, and dry vac pump of course.

The big caveat to the above is that the average private owner can take several decades to reach 2000hrs, which is far too long, given the amount of internal corrosion etc. Hangarage can also make a big difference to engines flown less often.
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Old 20th Apr 2008, 17:50
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Also in lycoming's service instruction 1009 states engines not reaching TBO hours within 12 years should be Overhauled regardless of hours run
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Old 20th Apr 2008, 18:14
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Also in lycoming's service instruction 1009 states engines not reaching TBO hours within 12 years should be Overhauled regardless of hours run
Very few private ops implement this 12 year limit.

This limit merely serves as a liability limitation for the benefit of the engine manufacturer For example Lycoming have just stuck a 12 year limit (which has becone an AD and is thus mandatory) on about 6000 of their crankshafts...
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Old 21st Apr 2008, 03:17
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Engine Life

Over the years i've had 6 engine rebuilds done here in the UK following TBO + 20%. The general comment that i'm given by those who do this work is that engines that are well in excess of 3000 hours before rebuild are common.

The 3000 hour + engine, when they have been properly maintained, are usually in good condition and need no more work than a TBO compliant engine. Norvick have a terrible reputation for taking forever with 3-4 months not being unusual. I've had engines turned round in a little over a week so Norvick and others like them must have engines sat on the shelf for most of the time. I have yet to pay in excess of 9000 including vat for a rebuild but hear of horror stories well in excess of that.

All the engines that I have had rebuilt have completed their TBO+ afterward with only minor unscheduled maintenance, usually to cylinders. Even cylinder maintenance was reduced when I changed over to Superior cylinders. I understand that Lycoming and Continental have got their act together at long last, with regard to their cylinders, which are now more likely to last the TBO period than they did at one time.

The 12 year TBO period will be very important should you be importing the aircraft into EASA land. EASA, I understand, will not accept an engine over 12years old onto the register.

With regard to purchase. The engine life must be on the side of the buyer. It is the buyer that will foot any bills later. For a standard 4 cylinder engine I would budget 6 pounds per hour for engine rebuild/replacement. Value your proposed purchase assuming a zero hours engine and reduce the purchase price by 6 per hour engine time flown. For any aircaft with an engine over its TBO reduce the purchase price by the full cost of a rebuild/replacement.
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Old 21st Apr 2008, 18:53
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Engine hours mean almost nothing. Engine conditon is determined by 3 things

1) How the engine is operated. That is did the owner allow it to warm up, perform proper runups and did not overheat or evercool it .

2) Regular use. Almost all private aircraft engines expire prematurely from inactivity induced corrosion. A rough guide is the logbook should show a consistant 1 hour per week which about the minimum use to keep the engine healthy.

3) Proper Maintainance. Regular oil changes (the less use the more the oil should be changed) and proper up keep of the baffles, exhaust and airfilter/carb heat box are essential for engine longevity.

An instructive example is the tale of two Lyc 0320's ( 2 C172's ) The first had an engine with 2000 hours in 4 years and a known operator and maintainer history. The second was a 300 hour engine overhauled 10 years ago with a unknown history. I recommended the first, the PPL went for the second and in 2 years has had to replace the camshaft (spalled) and 2 cylinders (corrosion pits) at almost $12,000. The 2000 hour engine airplane now has 2200 hours and other than oil changes the owner has spent zero dollars ahead of the firewall.... and he paid $10,000 less for the airplane.
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Old 5th Apr 2019, 16:40
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what are the engine requirements for a flying school aircraft, is it 2200 hours and then a new one?
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Old 5th Apr 2019, 20:52
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The hour limit depends upon the model of engine, though most are in the range of 2000 hours. The requirement to overhaul or replace the engine is based upon national regulation. It differs from nation to nation and the use of the aircraft, though flying school will be commercial, so to a higher standard. That said, there will certainly be engine maintenance costs along the way to the 2000 hours.
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Old 6th Apr 2019, 17:15
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Our school PA28 O360 is at 2150 hours, in it's 1st extension. It's also at 13 years, in it's 2nd calendar extension. We expect to reach both the end of the hours and calendar extensions this Autumn (nicely timed) We've done about 1,000 hours on this 1976 aircraft in the 3 1/2 years we've owned it. We will send the engine for overhaul to 'zero-time' it in compliance with doing flying training in the UK. At the same time, we're having a 'paint-off' respray, including complete overhaul of the engine bearer/leg assembly and firewall. I've quotes from 2 popular UK engine overhaul facilities and I'm minded to go for the more expensive quote, based on recent experiences of other people. We've a budget of 40k for this exercise and expect it to take 3 months, though both places have quoted much less time (yes, right!) I'd like it to come out cheaper of course, both quotes together come to less than my budget but my experience adds 15% to any quote. There's an impressive list of parts that are replaced 'new', but I suspect that in some cases means components that have been overhauled rather than straight from the manufacturers. I've chosen the paint shop in part because they've recently done a fantastic job on a couple of aircraft locally and because they have the facility for removing and refitting the engine as part of the deal.
None of this is cheap, but we've built in to our hourly rate for this work and have the money ready. I think 6 an hour for an engine fund is a bit optimistic, I've got 10 in my budget. If you get change, great!
By the way, whenever one of our members says they're thinking of buying a plane, I say find out the cost of a replacement engine and have that cash available. Some insurers now do a betterment scheme, but selling an aircraft with no engine is going to be difficult!

TOO
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Old 6th Apr 2019, 20:18
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Lycoming's own literature on the IO360 states, the 2000hour TBO is based on 40 hours of usage a month !
and if is not run for about 2 years with out corrosion protection it won't last very long when put back into service,
generally the camshaft lobes go rusty and wear down very quickly. Very poor design with the camshaft in the top of the crankcase,
the oil drains off after a couple of days and it starts to rust very quickly so beware of aircraft with long periods of no activity.

Last edited by horizon flyer; 7th Apr 2019 at 21:43.
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Old 7th Apr 2019, 20:24
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Originally Posted by TheOddOne View Post
Our school PA28 O360 is at 2150 hours, in it's 1st extension. It's also at 13 years, in it's 2nd calendar extension. We expect to reach both the end of the hours and calendar extensions this Autumn (nicely timed) We've done about 1,000 hours on this 1976 aircraft in the 3 1/2 years we've owned it. We will send the engine for overhaul to 'zero-time' it in compliance with doing flying training in the UK. At the same time, we're having a 'paint-off' respray, including complete overhaul of the engine bearer/leg assembly and firewall. I've quotes from 2 popular UK engine overhaul facilities and I'm minded to go for the more expensive quote, based on recent experiences of other people. We've a budget of 40k for this exercise and expect it to take 3 months, though both places have quoted much less time (yes, right!) I'd like it to come out cheaper of course, both quotes together come to less than my budget but my experience adds 15% to any quote. There's an impressive list of parts that are replaced 'new', but I suspect that in some cases means components that have been overhauled rather than straight from the manufacturers. I've chosen the paint shop in part because they've recently done a fantastic job on a couple of aircraft locally and because they have the facility for removing and refitting the engine as part of the deal.
None of this is cheap, but we've built in to our hourly rate for this work and have the money ready. I think 6 an hour for an engine fund is a bit optimistic, I've got 10 in my budget. If you get change, great!
By the way, whenever one of our members says they're thinking of buying a plane, I say find out the cost of a replacement engine and have that cash available. Some insurers now do a betterment scheme, but selling an aircraft with no engine is going to be difficult!

TOO
I would recommend you look at the advantages of a factory exchange engine and compare your quotations. If you do a factory exchange you will get the upgrade to roller tappets free of charge and the biggest historical cause of premature failure of the engine is removed.

The engine you get from the factory will be at a guaranteed fixed price. If you order it and specify a delivery date it will help your cash flow too.

With some overhaul shops if your crankcase or crankshaft needs rework you are likely to have a large increase in the quoted price. Will any reworks be in accordance with the Lycoming overhaul manual. Welding, line boring crankcases and grinding crankshafts or camshafts do not appear in the Lycoming overhaul manual. Once a crankcase has developed a fatigue crack in one place, it is only time others will appear. It is telling you it has reached the end of its fatigue life. It needs to be replaced not patched up.

Be certain any overhaul shop builds your engine and gives you a log book entry stating in qualifies for the TBO extension as per the requirements of SB1009.

By regulation all factory engines must include all ADs, SBs AND Service Instructions, this does not apply to field overhauled engines. It might not sound much but the mandatory inclusion of Service Instructions mean in reality a much larger proportion of a factory engine will have of new parts in it.

Lastly compare warranty. With a factory engine you can have a warranty all the way to TBO if you fly a lot of hours in a year.

It is a lot of money you are going to spend, just make sure you do your homework and compare apples with apples.

Best of luck and I hope you end up with a great flying machine
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Old 7th Apr 2019, 21:50
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I agree about a factory exchange and roller tappets will give some extra horse power as well, due to reduced frictional losses.
A small extra benefit.
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Old 7th Apr 2019, 23:44
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TheOddOne

Also if you have not already I highly recommend you upgrade to a skyteck starter.
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