What questions to ask and be cautious of when buying an aircraft?

[TalkingPie]

I'm skeptical of brokers, too, but we're not talking about a real estate agent who took a 3 month course and doesn't do much more than turn on the lights in the bathrooms, tells you when the counters were replaced, and calls the notary for you.

How do you know? Unlike for real estate, there's not even a three month course for being an aircraft broker. Even you could call yourself one tomorrow.

It goes without saying (even though I did say it) that you have to trust the resource that you're using. In my case I have a neighbour who owns the local flight school, has a few thousand hours flight experience, has helped others buy and transport small aircraft across the country, in addition to owning two himself, and who's employed at the same company I worked at. I'd trust that the money I'd pay him would be well worth the value he'd bring to the transaction. I imagine that word of mouth through flying clubs, schools, and pilot social circles could turn up other such individuals. From the sounds of it, there are people in this very thread who'd fill this role quite well.

[ahramin]

Ahramin

If the boroscope raises concerns then for me a cylinder removal becomes a condition of the sale. If the owner won’t go for it then I walk away. I know of one case where that exact issue came up. The guy really wanted the airplane and paid for the removal. It turned out that the engine needed some cylinder work but the engine was basically OK and so he went ahead and bought the airplane.

Ok. I probably overstated the point. But lets say he didn't buy the airplane and 50 hours later the cylinder that was removed and reinstalled comes apart in flight. Now the seller has at best an expensive headache on their hands because they allowed a pre-buy to turn into an invasive procedure that increases the risk of an engine failure. I'm not saying pulling a cylinder never happens, just saying that I would not recommend to any seller to allow it unless there was a non-refundable deposit in place, the rest of the money in escrow, and a clear understanding of what happens depending on what is found.

Allowing a cylinder to be pulled off your aircraft as part of a normal pre purchase inspection is a bad idea.

Also keep in mind that I'm not talking about sales of abandoned or junk aircraft. In loss of licence situations I've had sellers get someone to fly the aircraft every two weeks until sold. I've got a rebuilt F1 Rocket coming up for sale that we're planning on getting absolute top dollar for. We're going to put at least 25 hours on it before it's even offered for sale and will have engine monitoring data, tribology reports, and oil filter inspections to show. Any pre-buy will be very limited.

If we're talking about some aircraft that has been left outside and is being sold for a fraction of what it would be worth as a flying aircraft then I could see a seller having no choice. Actually I did sell a complete basket case a few years ago but we priced it as a basket case and sold it without any pre-buy. We didn't even post contact information on the sale ad, just the aircraft location. Two people took the trouble to go look at the plane, and the second one bought it. My fee on that one was low, but it was the easiest sale ever. Trying to sell junk aircraft is more trouble than it's worth.

[ahramin]

Well, the pictures show it tied down in a hangar at least...

That’s right. My first instinct to sell my well-kept always-hangared airplane, is to, uh, move it out into the snow, for the, uh, exposure. :-O

How about a little more info... the aircraft is said to have been moved from one small airport to a more busy one for better exposure with a "For Sale" sign on it. You're right - and I thought about it anyway - the exposure thing could just be total B.S. But if we take it that way, everything about this aircraft could be total BS and I should just forget about it and buy a brand new one; which I can't afford, of course. So for now, I'll just assume the guy who gave me the information (and his position would tend to make me think it is not in his best interest to bullshit me) is honest and I'll see on-site anyway. For now, what I have seen in the photos and videos does not tell me this A/C was parked and left in crappy weather conditions. And yes, those pictures could be photoshopped, eh?

Has the aircraft been flying since it was exposed? What is the reason for the sale?

[CpnCrunch]

Here is why cylinder removal for any reason is a risky procedure:

https://www.aopa.org/news-and-media/all ... y-business

If a plane required cylinder removal to adequately assess its condition, there is no way I'd buy the plane. As long as it's flown regularly, compressions are reasonable, and oil filter doesn't have any metal, you should be fine.

[Big Pistons Forever]

Here is why cylinder removal for any reason is a risky procedure:

https://www.aopa.org/news-and-media/all ... y-business

If a plane required cylinder removal to adequately assess its condition, there is no way I'd buy the plane. As long as it's flown regularly, compressions are reasonable, and oil filter doesn't have any metal, you should be fine.

In the case of the OP’s aircraft you would be 1 for 3. The airplane has not been flown regularly and the O 300 generally do not have oil filters, just an oil screen which generally is only good enough to catch metal that is large enough to have a readable part number. I would also suggest that there is a poor correlation between engine health and cylinder compression. As photo alluded to someone who knows what they are doing can see a lot with a boroscope, however there are somethings you can only see with disassembly.

I personally think the dangers of removal and reinstalling a cylinder are over stated and I have never had an issue with an airplane that had a cylinder(s) replaced. One place where I flew
Navajos the boss insisted on leaning to book fuel flows. We used to joke that the AME’s should just use Velcro to hold them on because we had so many cracked cylinders that had to be replaced.

[photofly]

I personally think the dangers of removal and reinstalling a cylinder are over stated and I have never had an issue with an airplane that had a cylinder(s) replaced.

I don't think it's a danger, but I took the trouble to have the exhaust removed on an engine because of a leaking gasket, and lo and behold a stud failed- the exhaust not having been removed in 1800 hours. My AME preferred to have it properly fixed, so off comes the cylinder and away it goes to the engine shop who refused to tag it because the bore was out of limits. So I had to buy a replacement cylinder. Maintenance induced maintenance.

If I had gone through all that to please a potential purchase I should be quite annoyed.

For reasons similar to those expressed in that AOPA article, there's no way I'd permit two cylinders to be removed at the same time.

[shaynemarshallporath]

I don't think it's a danger, but I took the trouble to have the exhaust removed on an engine because of a leaking gasket, and lo and behold a stud failed- the exhaust not having been removed in 1800 hours. My AME preferred to have it properly fixed, so off comes the cylinder and away it goes to the engine shop who refused to tag it because the bore was out of limits. So I had to buy a replacement cylinder. Maintenance induced maintenance.

The last 2 engines i looked at i pulled 2 cyls on a 700 hr SMOH engine ( 4 cyl) and another one 1000 old cyls (6 cyl) and found 50% of the valves eroded and line cut to the point of being DANGEROUS ! Valves drop in engines because they were fine until they failed catastrophically ! Mike Busch is okay, but sometimes goes too far in his ideas to make a name for himself!

BTW That last engine had 2 studs broken because of EXACTLY what Busch says about the near impossibility of getting bolt stretch right on cyl inst.

Even pulling an exhaust when they leak ( they will not last the life of the engine without leaking) does give opportunity to catch a valve ready to let go! Doing a boro with an instrument that works every 200 hrs is a good idea! Cam lobes and lifters go relatively slowly and generally show up in SOAP or the spin-on. Even the notorious H2AD cam eating engines deteriorated without catastrophe!

On the other hand, when conditions indicate, pulling 2 jugs is a very WISE insurance policy when purchasing an A/C at retail value !

[photofly]

I take photographs of all my exhaust valves every annual with a great borescope I bought. All good with them, so far.

[Big Pistons Forever]

I personally think the dangers of removal and reinstalling a cylinder are over stated and I have never had an issue with an airplane that had a cylinder(s) replaced.

I don't think it's a danger, but I took the trouble to have the exhaust removed on an engine because of a leaking gasket, and lo and behold a stud failed- the exhaust not having been removed in 1800 hours. My AME preferred to have it properly fixed, so off comes the cylinder and away it goes to the engine shop who refused to tag it because the bore was out of limits. So I had to buy a replacement cylinder. Maintenance induced maintenance.

If I had gone through all that to please a potential purchase I should be quite annoyed.

If I had gone through all that to please a potential purchase I should be quite annoyed.

On the other hand If I was the purchaser I would be quite happy an unserviceable cylinder was replaced before I bought the airplane.

As an aside I can't say I agree with your assessment that this was "maintenance induced maintenance". I would suggest it is an example of a good AME doing his/her job to ensure it was as you put it "properly fixed". I can say from significant personal experience that sometimes, actually make that most of the time; "properly fixing" an airplane involves spending a lot of money

[photofly]

The AME did a good job, and made the right decisions. But there’s no requirement to measure cylinders on a working engine, and no suggestion that the engine wasn’t airworthy. It’s an old engine, and if you go poking around you may have to pay to replace things. And sometimes you end up having to replace things other than the ones you wanted to poke around in, things which otherwise wouldn’t have needed replacing. Beware.

On the other hand If I was the purchaser I would be quite happy an unserviceable cylinder was replaced before I bought the airplane

It wasn’t, and isn’t for sale, and I never play the game of “I’ll buy it if you do/fix thing/tasks X,Y and Z”. You want it, make me an offer, buy it, and you fix it. If you don’t want it, that’s cool too. As a buyer I’m much happier fixing defects myself, that way I know they’re done right.

[Big Pistons Forever]

As a buyer I’m much happier fixing defects myself, that way I know they’re done right.

That is an excellent point. For most defects uncovered in a pre-purchase, a price adjustment would be preferable to the seller completing the repair.

A bit off topic but your example of the leaking exhaust gasket which leads to a cylinder change is a good example of the challenge of aircraft maintenance, especially, engine and radio repair. For engines small repairs can lead to bigger ones as unanticipated faults are brought to life. A good example occurred to a fellow I know. His 1500 hr Lycoming had a failing cam shaft, a common problem on lightly used private aircraft. When the engine shop split the case they found other issues which led to a full overhaul. There was a further $ 5000 dollar upcharge because the crank shaft was found to be cracked in addition to other parts which were not repairable.

What started out to be a $7000 repair turned into a $32,000 overhaul. So yes he had a new engine but the cost of the overhaul was close to what he paid for the whole airplane the year before.....

Similarly repairs of old radios can be a death by a thousand cuts as the radio repeatedly goes to the shop for $500 - $1000 a pop repairs. Pretty soon you are not far from what a new one would cost and you still have an ancient unreliable model boat anchor in your panel.

Old transponders with cavity tubes (ie KT 76, AT50) are not worth repairing when, not if, the cavity tube fails.

[Big Pistons Forever]

As a general comment, it appears to me that the private piston GA marketplace has stratified into 2 levels.

The first is what I think are now the majority of airplanes offered for sale. They are to put it impolitely "junkers". That is they have many years of deferred maintenance and little use. In many, if not most cases the bill to bring them back to a reasonable condition is so high the purchase makes no sense and unless there is some overriding desire to own a particular airplane, like it was the one you father used to own or something like that; run away.

The other level is the opposite of the first. These are really nice airplanes either because they have always had conscientious owners or the previous owner bought a junker and dropped a ton of cash on it. These are IMO the airplanes to buy. The problem is they are not that common and when they do come up for sale they are really expensive.

However my personal opinion is that in the long term the best thing to do is buy off the top of the market.

[shaynemarshallporath]

It is wise to pull ALL cyls midtime on an engine OH cycle especially when they need it (60/80 exhaust leakage, oil fouling oil consumption ) and toss away or overhaul. Midtime may be 1200 hrs on a engine that has a 1800 hr O/H cycle recommended by the manufacture A galling lifter will grind down a cam lobe in no time as compared to a refreshed ( reground ) lifter in a mid-time engine allowing the engine to go its full life , MANY variables !

[photofly]

I don't see any need to pull a cylinder with 60/80 compression. I've been running an engine for hundreds of hours with some compressions varying between 48/80 and high 50's. The lowest compression cylinder actually went up a lot, between the last annual, and the one before. The performance is unaffected.

The advice from Continental is that if a compression measures below 40, go and run the engine, and try again. If you can't get it above 40, then it may need work.

[Big Pistons Forever]

Where a cylinder is leaking air is much more important than what the absolute value of the pressure test is. A cylinder that is 50 over 80 and all the air is coming out of the exhaust pipe is definitely worth a look inside with a boroscope to see what the exhaust valve looks like.

If all the air is coming out of the breather then carry on. Also change in DP’s is a good indicator of problems. If the cylinder was 55 last year and it is 52 this year no worries. If it was 78 last year and is now 48 then further investigation is warranted.

In any case it is always worth a second engine run and test before doing anything. You may find the problem has gone away.

[Found]

Realistically you are going to spend a MINIMUM of 6 to 8 K a year before you turn the propeller.

I feel lucky now, I have been no where near 6 K a year, to be fair I haven't needed avionics work (besides a used altimeter and a altitude encoder) or major engine work (some exhaust parts and an oil sump gasket that was a lot of labour). It is a fixed pitch prop Cessna 172 so insurance is also cheap.

We have pulled cylinders on pre-purchases and have had other shops do the same on aircraft we maintain, if done right there is nothing to worry about.

[shaynemarshallporath]

Agree fully with the last 2 posts ! If there is a large exhaust leak at 60/80 you should investigate! BUT it may only be the extra heat that causes the head of the valve to break off when there is excessive erosion of the valve stem and radius!

[Big Pistons Forever]

Realistically you are going to spend a MINIMUM of 6 to 8 K a year before you turn the propeller.

I feel lucky now, I have been no where near 6 K a year, to be fair I haven't needed avionics work (besides a used altimeter and a altitude encoder) or major engine work (some exhaust parts and an oil sump gasket that was a lot of labour). It is a fixed pitch prop Cessna 172 so insurance is also cheap.

We have pulled cylinders on pre-purchases and have had other shops do the same on aircraft we maintain, if done right there is nothing to worry about.

I should have been clearer. The 6 to 8K figure was total annual fixed costs, maintenance, insurance tiedown and miscellaneous. On top of that you would have to , of course, pay for fuel and oil when you flew. 6 K will pay for 35 hours of renting which is close to what most PPL's fly in a year. There are many good reasons to own an airplane, I should know as I own 2, but saving money is not one of them. I raised this issue of total costs of ownership because I see a lot of pilots new to aviation that don't have a good understanding of the reality of airplane ownership.

[Squaretail]

I see a lot of pilots new to aviation that don't have a good understanding of the reality of airplane ownership.

That’s not surprising, if one goes by aviation forum content, the venn diagram of pilots and “understanding reality” are two non overlapping circles.

[Big Pistons Forever]

I see a lot of pilots new to aviation that don't have a good understanding of the reality of airplane ownership.

That’s not surprising, if one goes by aviation forum content, the venn diagram of pilots and “understanding reality” are two non overlapping circles.

On the other hand you have lot's of airplane owners, my self included, that have a good understanding of reality, go ahead and own airplanes anyway. Sometimes you have to override the brain and listen to your heart