Engine specs for dummies anyone?

[AN2 Driver]

Folks,

question to you engine experts, and thanks for the information you gave me earlier :)

How would you guys determine the actual state of an engine at any given time? Say, you come across some O320 or O360 engine at mid time (roughly 1000 hours SMOH), all AD's done and verified, oil analysis done and filter cut, all looks fine. What compressions should get one's attention? Below 75? 70?

At the same time, someone tells me that continentals (such as the E225 or similar) have generally less compressions at the checks than comparable Lycomings, can't really see any logic in that, is there one?

Finally, what does qualify as a Major overhaul? I was looking at a IO360 which had 4 cylinders and crankshaft bearings overhauled 100 hours ago, but this does not seem to qualify? What is a Top Overhaul and how does it affect TBO for a privately operated plane?

Let me run some engines I have been looking at (all in appropriate airframes) by you and tell me what you think.

Lycoming IO360, total time 1500 hours since new in '74, had the above overhaul (4 cylinders and crankshaft bearings done) at 1350 hrs 10 years ago... been locked up in a hangar since about a year.

Lycoming O360, 1600 hrs since overhaul but was converted from constant speed prop to fixed pitch prop at 700 hours into the current 1600. Does that mean the potential of this engine would be higher than 2000 hours for private ops?

Lycoming O320, 450 hrs since overhaul (date unknown) but obviously not used a lot. What to look for in such rarely used engines and how to bring them back into normal use without damaging them?

Finally, a continental E225 with about 1200 TSO and all compressions around the high 60ties (67 and higher, but none above 70), plane and engine in mint condition otherwise.

Thanks guys. For the usual perspective owner/pilot these things can become really confusing and your inputs have shown to be spot on in recent memory :)

Best regards
AN 2 driver

[IO540]

Can't help with the legal definition of an overhaul (there might be something on the Textron/Lycoming website) but an engine that has not been run for a year is highly suspect, due to internal corrosion.

In the early 2000s, a certain well known IFR tourer manufacturer installed a number (at a guess, some dozens) of IO540 engines which were stored in their warehouse for about a year. Quite magically, the period between the shipping date from Lyco (which is verifiable, by calling Lyco) and the installation/ first run date (which is not verifiable) was just a few days short of a year, as evidenced by the engine logbooks. Quite magically....

Over the following years, quite a few of the owners found heavy scoring in the barrels and one I know found the engine nearly seizing during flight. Another I know found corrosion in all cylinders despite (like the previously mentioned one) flying more or less every week since new.

I would consider the engine as needing an overhaul by default, so £10k-15k off the price. Otherwise, take a walk.

If you really want it, do a borescope and oil analysis and if possible pull a cylinder to inspect the camshaft and at least that cylinder (the corrosion may be below the piston top and not visible on a borescope).

[AN2 Driver]

Thanks for your reply, guess that goes for almost all of them. It was exactly the concerns you voice which got me to open this thread.

I used to own a single Cessna years ago which was flown about 30-50 hours a year and I was lucky, never had any problems whatsoever. What I did however was to run the engine bimonthly during times I could not fly. I am looking for some reliable wings again now and I do not want to be dropped into a money pit from a height.

The IO360 you refer to resides in an aircraft which is in absolutely pristine condition outward but like you, I am very hesitant to touch an engine which has not had a decent outing in a while and not a lot before that either. If I do recall the log correctly, it has maybe spent 10 hours a year flying and was sitting around otherwise, I'm told the engine was run bi-monthly during the time it's been for sale, but how to verify that... Apart that it has moved hangar spaces several times when I went there. And looking at the fact that the cylinder and crankshaft overhaul was done in the late 80ties and it has only done 150 hours since also does not really inspire confidence. I also wonder why the overhaul mentioned was necessary when they did it, which the current owner does not know.

The crux today is that most of the planes in the low end market today are sold due to underuse, lack of time, exploding maintenance cost e.t.c which would make them very suspect for such stuff. I have not yet seen the logs of the O320 with the 450 hours since overhaul, which normally would be a very nice reserve, but again, I suspect it's been sitting around for ages doing nothing. The E225 and the O360 are regularly used, they fly between 20 and 50 hours a year in recent years, but is that enough to keep an engine happy?

What do you regard the maximum time interval between runs before an engine like that becomes suspect?

What I have been considering is to ask a local overhaul center (they do complete overhauls for all piston makes) to assess the various engines, which might mean moving the aircraft where they are, but that is still a lot less costly than finding out that the engine is no good in flight. :uhoh:

Best regards
AN2 driver

[IO540]

What do you regard the maximum time interval between runs before an engine like that becomes suspect?

AFAIK opinions vary widely and it must depend on whether hangared etc and where, type of oil used, but I guess that regular sittings of 4 weeks plus are likely to cause problems.

So, 50hrs/year should be absolutely fine if the owner took it for a 1hr flight each week. However I think such regular use is relatively rare for privately owned planes, and this is why one needs to look into it deeper.

I have also been advised by old hands in the maintenance business that with a very low hour plane one gets a high likelihood of equipment e.g. avionics failures. I don't know why that should be IF the plane was hangared but if standing outside then one can see this because condensation etc will rarely get a chance to be displaced.

To state the obvious, however, much must depend on the value of what you are buying. If it is a £150k IFR tourer then a good specimen with your preferred equipment already installed could be worth a lot of due diligence, at your expense, and a certain amount of doubt re the engine can be factored into the price. Whereas if you are spending £25k on something which is worth more or less just the residual engine time then the engine needs to be looked at all the more carefully because if it turns out to be trashed then you have bought a pile of worthless junk.

[gasax]

A long time ago i bought an aircraft which had flown about 50 hours in the preceeding 10 years. 2 years later it became quite reliable - and I was an expert on that engine and its accessories.......

So the advice has to be if it has n't been used regularly in today's market leave it.

The same advice might apply to the E225. From conversations with an owner of a Navian in the US I recall getting the right spares was a real issue. Majors are possible but only from a couple of sources. There is a big differnce in the prices between the E225 and O-470 versions because of this. The only other airframe I can think of is the early V-35 and that is a whole different set of issues.

And no there should be no difference between Lycoming and Continental compressions.

[AN2 Driver]

Hi guys,

thanks again for the input. I am completely open minded, have been on the lookout for a while now, the nice thing is, while looking out the budget gets a bit higher :p while the planes have gotten cheaper :) . Which has brought some airplanes into the game I could not have dreamt of when I set out.

Originally, I looked at "simple" planes, such as PA28's for low maintenance costs and simplicity of systems. There are still several on the shortlist. Temptation however has thrown 2 others into the game, one of which has the range I'd want but the engine in doubt, the other one is, as gasax has rightly identified, a 1951 V Bonanza, which has a very short range (400 NM)but is a lot of airplane for the money, particularly as it is in a VERY nice condition.

I'll keep looking for more opinions here on Pprune, IO540 and gasax thanks for your replies. I must admit, half the fun of looking for some new toy is to learn as much as you can about all of them. And as flying is about learning as long as you're in it, I'll just continue my research until something does look and feel right and all the experts show their :ok: .

Thanks again.

Best regards
AN2 Driver

[SNS3Guppy]

Compression values are highly overrated, and given far too much importance by the average layman.

The chief value of performing a compression test isn't the compression numbers, but the ability to identify the leak location, if indeed there's a leak. Pressurize the cylinder, listen for the leak (exhaust, crankcase, intake).

Compression values go up and down with the test unit in use, the person performing the test, the temperature of the engine, and vary from time to time when the tests are performed. It's not uncommon for test values to go up since the last time the test was performed. The actual values identified during a cmpression test...aren't really very significant unless a substantial decrease occurs.

[EchoMike]

Unflown engines - use a borescope, check for cylinder wall corrosion. If the cam is on top (O-320/360 Lycoming), cam wear (rust, pitting, spalling) can be a problem in seldom-flown engines. For some reason, Continental engines (cam under crank) are not as affected by this.

Overhauls - there's overhauls and there's overhauls. Take the engine that has only a few hundred hours since major and has been sitting. Most probably, it needs to be taken apart and corrosion related items replaced (along with all the gaskets, lock rings, etc, etc.) and this job will probably be mostly labor. On a high time engine, we are also looking at worn parts, and if you add corrosion from non-use, now we are talking serious money.

Definitions - top overhaul - cylinders only, some engines you can change the rod bearings without splitting the case (O-200 Continental). This does NOT cover anything in the bottom end - crank, cam, case, etc.

Major overhaul - engine completely apart, there is a factory list of parts which MUST be changed for this to legally be a major, otherwise it is a repair.

Lycoming specifies an engine has to be overhauled every 10 years or X,XXX hours, whichever is first. This is their lawyers speaking - they are playing CYA (or C Lycoming's A), and just the years usually isn't a problem.

Continental has no time in service recommendation.

Many engines will run two top end cycles for each bottom end - "1,500 since top" is a red flag - when was the bottom done? Are we at the end of the second cycle (3,000+ since major)? This is gonna be expensive . . .


On the early model Bonanza, be very careful here. The airplane is cheap, and has probably had a series of owners who couldn't quite afford it (like an older Porsche), consequently some very expensive maintenance may have been neglected. There was an article in AOPA mag (I think) about restoring an older Bonanza, the magnesium wing attach "bathtub" fittings were corroded, the corrosion was hidden and they found it because they had a Bonanza expert looking at the airplane - it would not have been obvious to the average owner - and oh, my was this ever an expensive repair! Remember that parts prices are based on the NEW and expensive airplane and just because this is now an OLD and cheap airplane the parts prices are not coming down to match.

There's also frequently corrosion inside the ruddervators (also magnesium) and the only cure is replacement. There's also a vital AD note regarding the tail - if the AD note hasn't been done, the top allowable speed is much lower than normal, you aren't buying a Bonanza to go 125 mph.

Personally, and this is just me, I'd be looking to buy something that I can afford to maintain properly even if it means I'll be going somewhat slower. Don't EVER buy the fastest airplane you can - speed costs money, and the maintenance costs go up very fast on fast, complex airplanes.

If you have to strain to keep it flying, you won't fly as much, and you won't be a sharp as you should be. One fine day you may get into a situation that you might have been able to handle if you were more current, but if you've only flown 20 or 30 hours in this airplane this year, well, maybe things won't work out so well.

Best Regards,

Echo Mike

[IO540]

Magnesium must be hell on an aircraft. I machine various components (not aviation related) out of magnesium. The stuff cuts easily (I have a turret mill) and weighs little. I've got a stack of magnesium ingots in the workshop. The stuff corrodes in a funny way. You get a little pinprick. About a year later it has grown into a massive blister, about 10mm diameter and sticking out of the ingot by about 5mm. The corrosion is probably 2-5mm deep too. This is in dry indoor conditions! I reckon that if an elevator was skinned with magnesium, and you got a tiny scratch in the paint, a year or two later you can forget the elevator. The skin is only ~ 2mm thick.

Tell you what though.... it makes a fantastic show if chucked onto a bonfire.

I'd be looking to buy something that I can afford to maintain properly even if it means I'll be going somewhat slower.Couldn't agree more. You have to be able to afford the plane without major issues. At the piston level of things, you need to be able to write a £20k cheque anytime, in case of suprises.

It also has to fit the mission profile; if you fail on that score then you will always be miffed with it, no matter how much money you have. This is why a fair number of (wealthy) owners who ended up flying turboprops all of a sudden chuck it all in.

[AN2 Driver]

Hi Echo Mike,

thanks a lot for the definitions, saved for further reference.

The Bonanza I am looking at has had it's owner for many years, he is selling due to age, possible upcoming medical problems and lack of time. He could easily afford it but you have a very valid point in questioning if I can or want to, that is why I research the heck out of it first. By the figures I have heard from him and others, you are right on the aspect of it being expensive just for the routine maintenance, factor 2 of comparable aircraft. I will investigate the magnesium issue in depth, this example has spent all of it's long life hangared, but still, I'll look at it carefully. The AD has been done a long time ago and maintenance is up to speed, but as you say, there are many things which can go expensively wrong with a plane this age and make. I'll keep that in mind, also the fact that the short range is most probably ending up as the show stopper.

Unflown engines - use a borescope, check for cylinder wall corrosion. If the cam is on top (O-320/360 Lycoming), cam wear (rust, pitting, spalling) can be a problem in seldom-flown engines. For some reason, Continental engines (cam under crank) are not as affected by this.

Right, this would mean this IO360 is probably a good candidate for it then :sad: .

Personally, and this is just me, I'd be looking to buy something that I can afford to maintain properly even if it means I'll be going somewhat slower. Don't EVER buy the fastest airplane you can - speed costs money, and the maintenance costs go up very fast on fast, complex airplanes.

Well, this was my philosophy at the outset but I did get carried away a tad when prices started to fall through the floor. I hear you though, and this kind of reminder is exactly why I post in this forum. People who've been there, done it and got a drawer full of t-shirts to prove it will always be able to tell you the facts as I need them.

@IO540

Couldn't agree more. You have to be able to afford the plane without major issues. At the piston level of things, you need to be able to write a £20k cheque anytime, in case of suprises.

Well, yes if you need to cover an engine replacement/overhaul at any given time. Unfortunately, and this includes me, very few people will have this kind of reserve from the outset but will amass it during the first couple of years by putting higher allowances onto the hourly calculated rate. Clearly, this indicates how very important it is to make sure the engine is in a reliable condition. If I had the financial freedom to simply take any plane I wished for and run an overhaul the moment I buy it, the decision would have been taken a lot easier and a few months ago. But I will need a few flying seasons head time before I can think of a complete overhaul of an engine.

It also has to fit the mission profile; if you fail on that score then you will always be miffed with it, no matter how much money you have. This is why a fair number of (wealthy) owners who ended up flying turboprops all of a sudden chuck it all in.

Very true but difficult to make happen. My typical mission would need a range of 800 NM, which save for one none of the planes can do, so it will always be a question of intermediate stops. The question is, can I live with this limitation or not. I reckon I can. The other side is, a 100 KTAS plane makes trips like these kind of loooong, so 120 to 140 kt would be useful.

Taking all that and what you have told me here into account, I'll have a thorough check done on the one plane which would fit the profile and my pocketbook at the same time and see what the outcome will be.

Again, thanks for your inputs.


Best regards
AN2 Driver

[IO540]

My typical mission would need a range of 800 NMThat does not appear to be a problem.

My TB20 will do 1300nm, zero wind, zero fuel, power reduced to 140kt TAS at FL100. 20"/2200/9.0GPH/LOP. At normal cruise, say 155kt TAS, FL100, max possible power, LOP, it will do 1100nm.

800nm is a problem only if there is significant headwind.

Intermediate fuel stops are a real PITA. You can waste half a day sitting around some place if you are unlucky. Plus PPR, Customs, all that cr*p. And since the delay is indeterminate, the onward flight plan cannot be reliably filed in advance so one ends up filing it online (mobile internet) sitting in the cockpit... life's too short.

Re the £20k cheque :) you do need to be able to cover that eventuality, otherwise if you get an engine issue what will you do? Sit there for 2 years, with the plane grounded and all but worthless, with the engine corroding, etc, while you are saving up for the repair?

[wsmempson]

"My typical mission would need a range of 800 NM, which save for one none of the planes can do, so it will always be a question of intermediate stops. The question is, can I live with this limitation or not. I reckon I can. The other side is, a 100 KTAS plane makes trips like these kind of loooong, so 120 to 140 kt would be useful."

At the risk of thread drift here, what about a normally aspirated Piper Arrow III? with 77 usg tanks (out of which 72 useable), that gives 135kts at 23/23 and 10usg/p/h - which gives you 830nm range with an hours reserve.

Not nearly as glamorous as the opposition, but pretty predictable operating costs, due to the fact that you are running the aviation version of a ford Cortina. £50-60 for a really nice one with a low hours engine....if you can find one, that is!

A chap at the flying club explained to me that if you have to by parts for a Beechcraft, not only does he have to pay a stiff price for the parts, but he also has to pay a seperate charge , based on how long the part had sat on the shelf - a rental charge for the space!

[IO540]

830nm range with an hours reserve.

That's much too tight for an 800nm distance.

You need destination, then alternate, then 45 mins at cruise speed to be FAA IFR legal.

Also the alternate doesn't want to be next door because bad weather is likely to be widespread. And Europe often has a poor choice of alternates. So for an 800nm trip one needs a range of 900nm plus the 45 min reserve. Plus any headwind - a 20kt headwind will make that 1030nm plus the 45 mins reserve.

In any case, to fly long legs like this, an accurate fuel flowmeter / fuel totaliser is a must otherwise one is making a wild guess as to what is really in the tanks.

[wsmempson]

Sure, of course you're completely right Peter - but in practical terms, it isn't the fuel which dictates endurance, it's the size of the bladder. 3-3.5hrs is about as far as anyone other than a camel is capable of lasting, without resorting to a catheter or peeing in a bottle.

Whilst, in extremis and flying by myself, I have been known to pee in a bottle - my Mrs refuses point blank. I even bought one of those special red pee-bottles they advertise in the transair catalogue, with a 'lady jane' adapter - which seemed to make Mrs. E even angrier....

I also find that arriving at a airfield clutching a brimming bottle of pee, interferes no end with my self image of being an international man of mystery.

3-3.5hrs gets you to Bergerac or Lyon in an Arrow in one hop and, if I'm honest, is about as far as I'd want to go in one hop without a co-pilot.

If the budget is less of an issue, a TB20 would get you further in more comfort as it's a far more comfortable, newer, more capable machine - but I suspect that £50-60k wouldn't buy you a well equipped Socata TB20 with a new-ish engine, so budget will dictate the choice.

Drifting back to engines, the received wisdom tends to suggest that engines need to be used regularly, otherwise they quickly develop a range of problems and, if you spend any time IFR, over open water or over mountains, you have to decide whether that is a chance you're prepared to take. Personally, having just been through the engine overhaul experience involving an out of time engine that seemed to run just fine with decent compressions, but proved to be missing most of two cam lobes and have a crack in the crank, I'd want to be sitting behind a known quantity!

[AN2 Driver]

Yes, a TB20 would do nicely, but they are definitly outside budget. The ones I have seen which are not over TBO already will set one back 100k Euros +.

Of what is available and within, there is a HR100, which will do this nicely, but has the problem of having been stored too long for comfort, apart from the obvious Robin/Apex part problems. Anything else I have looked at and which has a degree of financial realism attached will need stops in between, which is not too much of a hassle because the mid point is in Croatia, which has very reasonable taxes and fuel prices.

Re the £20k cheque you do need to be able to cover that eventuality, otherwise if you get an engine issue what will you do? Sit there for 2 years, with the plane grounded and all but worthless, with the engine corroding, etc, while you are saving up for the repair?

I get your drift. Yes, eventually (and probably quicker than this too) this reserve needs to be built up and it will. Let's say, they are not in the "airplane budget" per se at this time but if the engine really decides to quit within the first half year or so, some ressources will be available to get the plane back going under the planned ops.

At the risk of thread drift here, what about a normally aspirated Piper Arrow III? with 77 usg tanks (out of which 72 useable), that gives 135kts at 23/23 and 10usg/p/h - which gives you 830nm range with an hours reserve.

Arrows have two problems in this here country. If it is registered here it will be expensive like heck, if not it will need a silencer built in before it can get under this register. If at all possible I will try to find something which is under this register for this reason, but this does limit the choices. Apart, the question in my mind is if the Arrow is worth the financial effort over, say, a Cherokee. Ok, about 20 kts speed difference but a lot higher maintenance due to the variable prop and gear. 830 NM is way too tight for comfort, particularly if you have no alternate within 40-60 NM which carries Avgas. If it can't get there in the first place, a 550 NM range with 1 stop will do the job.

I'd want to be sitting behind a known quantity!

So do I and not even considering IFR or long water legs. That was the main reason to start this thread, to figure out how the engine issue is to be taken into calculation.

My advantage is that I am not in a hurry, have time to collect facts and figures and wait for the proper chance to appear.

Best regards
AN2 driver.

[IO540]

it isn't the fuel which dictates endurance, it's the size of the bladder

I know I bang on about this one but it is time this was put to bed. No serious pilot is going to have flights limited by having to pee. One can go without a pee for quite a few hours especially if one goes to a lot of trouble to dehydrate beforehand (which isn't great for one's brain) but on a cold flight (and most high altitude flight in IMC or below cloud, or in the winter anytime, or any flight at night, is very cold, due to the lack of solar gain into the cockpit) one needs to pee more often. It isn't great to be desperate for a leak when trying to fly an approach, and having to land for a pee has to be the biggest time waster ever.

The bottle solution is dead easy for a bloke and workable for a woman.

I would never depart without a bottle :)

I do fully understand the "international man of mystery" however ;) That IS important.

[AN2 Driver]

Peter,

friend of mine who used to do ferry flying told me his standard reply to the kind souls who greet him at refuelling airports with "Welcome to .... " was "Thank you, where is the toilet?".

I did read a great account of a German fellow who flew a motor glider from Germany to Australia. He had a small bag with him for use when he needed relief which he would then empty out of the storm window. It took a few tries until he found which end to push through first in order not to generate a spray can necessitating a thorough shower as first order of business after landing. :}

Those bottles are good solutions, some of them even come with rather cleverly designed bags to carry them in, which make them look like camera bags or handbags for the Jane variant.

Best regards
AN2 Driver