Buying a used aircraft

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Austin Koch

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Austin_Koch
Hi guys,

I'm looking to purchase a Piper Cherokee. I've been in talks with the owner and I wanted to get a second opinion. The aircraft has been out of annual for 10 years, but has always been hangared. It's got about 975 SMOH. The compression's were tested last week and were measured at:
#1. 75/80
#2. 74/80
#3. 75/80
#4. 62/80

It was boroscoped fairly recently and no defects were found. Cylinder #1 was unbolted and inspected, and no defects or carbon build-up was found. The airframe appears to be in great condition, but I don't want to purchase the aircraft and find a ton of problems with the engine. Any advice on this would be greatly appreciated. Thanks in advance!
 
Austin Koch said:
I don't want to purchase the aircraft and find a ton of problems with the engine.
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Conversely Austin, the common and quite useful advice I have seen is to price used aircraft as if you plan to overhaul - that way, any time you get before you actually do, is gravy.
(It is a regular occurrence that someone buys an airplane and is tearing the engine apart in the first year.)
 
I would be more wary of the engine now that I would be before they removed a cylinder just to inspect it.
 
The compressions are fine. Even the 62 isnt that much cause for real concern. However, if one were going to pull a cylinder to look at why not pull the LOW one??
 
JCranford said:
The compressions are fine. Even the 62 isnt that much cause for real concern. However, if one were going to pull a cylinder to look at why not pull the LOW one??
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Good question, I was curious about the same thing. I’ll have to follow up and ask about that. Thanks!
 
JCranford said:
The compressions are fine. Even the 62 isnt that much cause for real concern. However, if one were going to pull a cylinder to look at why not pull the LOW one??
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I was wondering the same thing. I think to inspect the cam on the o320, you have to pull a cylinder. But I'm no mechanic (I didn't even sleep at a holiday inn last night).
 
JCranford said:
The compressions are fine. Even the 62 isnt that much cause for real concern. However, if one were going to pull a cylinder to look at why not pull the LOW one??
Click to expand...
Turns out the #1 cylinder was inspected prior to checking the compression's. The compressions checked out so the mechanic didn't inspect the #4 cylinder in depth.
 
That just makes 0 logical sense. At this point I would be suspect of anything the mechanic had to say. I mean why would you pull a cylinder before doing a compression check? You know you have to do the compression check so why not combine the inspection with any potential low cylinders.
 
Grum.Man said:
That just makes 0 logical sense. At this point I would be suspect of anything the mechanic had to say. I mean why would you pull a cylinder before doing a compression check? You know you have to do the compression check so why not combine the inspection with any potential low cylinders.
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Wouldn't you need to check the compression of the cylinder after its re-installed? Maybe it was done that way to avoid doing it twice (?). I'm not convinced its nefarious.
 
I’d be more concerned about a rusty cam than anything sitting that long
 
Weekend Warrior said:
Wouldn't you need to check the compression of the cylinder after its re-installed? Maybe it was done that way to avoid doing it twice (?). I'm not convinced its nefarious.
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Compression check is a matter of minutes per cylinder. R&R cylinder a matter of a couple hours plus. I would certainly want to check compression before pulling cylinders. If compressions are low on all of them then pull them all. Or none.
 
alfadog said:
Compression check is a matter of minutes per cylinder. R&R cylinder a matter of a couple hours plus. I would certainly want to check compression before pulling cylinders. If compressions are low on all of them then pull them all. Or none.
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Are you an A&P? (Not being a smart ass, just asking).
Am I right about pulling a cylinder to check the cam on an o-320?

Edit: oops, question answered from your signature.
 
Weekend Warrior said:
Are you an A&P? (Not being a smart ass, just asking).
Am I right about pulling a cylinder to check the cam on an o-320?

Edit: oops, question answered from your signature.
Click to expand...

There are A&P's here with lots more experience than me but yeah. I R&R a cylinder on an O-320 early this year and we tried to get a look at the cam at the same time but it wasn't a great result. I just last week did one cylinder on the O-235 on my American Yankee to address a low cylinder but didn't try to look at the camshaft. Maybe I should have.
 
So rereading the OP, correct me if I'm wrong but I get this impression. Recently, it looks like the owner wanted to assess the condition of the engine for upcoming sale. So he had it borescoped and one cylinder pulled. I'm sure they checked the compression at that time too. It was probably fine. Then last week they check the compression again and you have a low cylinder.

If that's the scenario then I don't see a major cause for concern. Just buy the airplane cheap enough. I've got a nice early Cherokee 140 that hasn't been flying in years and I will sell it to you with a fresh annual for $20K. How's that sound. LOL
 
Weekend Warrior said:
Wouldn't you need to check the compression of the cylinder after its re-installed? Maybe it was done that way to avoid doing it twice (?). I'm not convinced its nefarious.
Click to expand...

i would but not necessarily. My point is do it first since they planned to pull a jug to check for corrosion why not pull the one with low compression.
 
Austin Koch said:
I'm looking to purchase a Piper Cherokee. ... The aircraft has been out of annual for 10 years...
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This may be a decent deal if the risk is factored into the price, but there's absolutely no way for you to catch a good deal of that nature as your first airplane purchase. It's essentially guaranteed to be a dumpster fire of an ownership story.
 
Weekend Warrior said:
Are you an A&P? (Not being a smart ass, just asking).
Am I right about pulling a cylinder to check the cam on an o-320?
Click to expand...

On an o-320 if you're going to pull cylinders to inspect the cam and lifters you're going to want to pull one front and one rear cylinder. There is a main bearing support between the front and rear cylinders that will make it challenging to see the whole thing by just removing one of them. But before any cylinders get pulled there's a chance that you could send a camera in the crankcase and have a look with minimal invasion. You probably won't see much this way though.

With an engine that sat inoperative for a decade I wouldn't be expecting much out of it. But it might be ok...
 
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