Pre-buy inspection. Is it reasonable?

[Kristin]

A lot of these narratives are from the perspective of the buyer, which is because the OP was "the buyer". I have been both buyer and seller, many times over. I just sold my PA30. I priced it right. It cost me insurance (May) and an annual (October) if I was to keep it. I could have sold that plane 6 times the first week, including two buyers who wanted to wire me the total amount with hours of me agreeing to sell to them. One of those was for MORE than my asking price. But I already made a deal with a nice guy who flew in to look the second or third day I had it listed. It was bad WX so no flying, and it was almost impossible to pull it out of the hangar as we were iced in. He said "no problem, I am taking it at asking price" but he wanted to bring a mech who was also a CFI, and do a pre-buy. I had no issues as I was not impatient, but other sellers in my shoes might take one of those wire transfers, and I would not blame them. It is a weird market. I hate to say it, but throw a lot of conditions at a seller might mess up that deal. He might just say "my other line is ringing.....stand by". I also wanted the buyer to be comfortable buying my plane and to know as much about it as can be known.

As a seller, there is a benefit to having the buyer do a pre-buy. If the buyer has a mechanic bless it, then you have another layer of protection in case the buyer decides to claim that it was misrepresented or deficiencies were not disclosed. Sellers often innocently misrepresent that all AD's are up to date. They base this on what their IA has told them. But if the IA is wrong, then the buyer may be able to come after the seller, who may then either have to eat it, or go back against the IA who gave the seller bad information. I have had buyers purchase a plane from me and I begged them to get a pre-buy, but they chose not to do so. At least my begging was in writing.

 

[Gino Shtirlits]

Gentlemen! My idea was not so bad. Just recently prospectively purchase Cessna150 could not reach at least 110 knots at 2500 feet above see level and 2600 rpm. Definitely I supposed problems with the engine. Later I have found 66 and 68 in compression reading (two cylinders). So I was right. I have rejected this Cessna from my wish list without any doubts. The requested price as much as $35000 is looking absolutely not reasonable for this plane. Now this guy is selling his plane at "barnstormers" and "trade a plane". Сcondolences to a buyer. I will use my simple test next times.

 

[Salty]

Gentlemen! My idea not was so bad. Just recently prospectively purchased Cessna150 could not reach at least 110 knots at 2500 feet above see level and 2600 rpm. Definitely I supposed problems with the engine. Later I have found 66 and 68 in compression reading (two cylinders). So I was right. I have rejected this Cessna from my wish list without any doubts. The requested price as much as $35000 is looking absolutely not reasonable. Now this guy is selling his plane at "barnstormers" and "trade a plane".

How fast are you expecting a 150 to go at 2500 and 2600 rpm?

66 compression is not a direct indication of anything bad.

 

[Gino Shtirlits]

How fast are you expecting a 150 to go at 2500 and 2600 rpm?

66 compression is not a direct indication of anything bad.

I expect the speed what indicated in the POH. 112-115 knots. So I would like to see at least 110. Low compression is low compression. It could lead to cylinder replace or repair. IMHO.

 

[Salty]

I expect the speed what indicated in the POH. 112-115 knots. So I would like to see at least 110. Low compression is low compression. It could lead to cylinder replace or repair. IMHO.

Good luck finding a 50 year old plane that does book numbers and has perfect compression. There are some that will do the former, but very seldom will you see the later, and compression in the 60's is more often than not, no big deal.

 

[jim73CQ]

I will use my simple test next times.

Yes, your (IM)HO is truly an HO. You will wait until he!! freezes shut to find a early 150 that will come anywhere NEAR "book" numbers. And when you can put A&P or even better IA behind your name I might listen to you.

More engines have been prematurely overhauled when the aviation industry went to leakdown tests instead of true compression tests and oil usage data than should have been. I'd be willing to bet a whole bunch of money that your "66" leakdown test would have been something on the order of 120 psi compression and that engine would have lasted you most of your flying career.

I got my A&P when the Wright Brothers were digging the remains of the Flyer out of the Kitty Hawk sand. As a young and stupid mechanic I used to do prebuys until I ran into a couple of unlearned folks like you. One of them took me to court FIVE YEARS and 200 HOURS after the prebuy because the camshaft had spalled and i didn't catch it. They lost, of course, but I haven't done a prebuy in the subsequent 50 years. And I sleep well at night.

Before you dismiss me as another greasy mechanic who couldn't spell "cat" if you spotted me the "c" and the "a", I can put MSEE behind my name too.

Your credentials?

Oh, and you might want to find when to use the plural "times" for a singular verb.


Jim
A&P IA

 

[jim73CQ]

Not exactly sure what a “Lycoming wobble test is, but a lot of good points have been mentioned so far.

I don't think it is particular to Lycomings. I use them on nearly every version of engine. You simply rotate the engine until the particular valve you want to measure's tappet is clear of the valve stem. Then you use your finger to "wobble" the valve stem. There HAS to be some clearance between the valve guide and valve stem, and the "wobble" should not produce a "clank". That "clank" indicates that the valve guide has worn beyond serviceable limits.

Is this an approved manufacturer test? Probably not. Is it what we use in the field to find worn valve guides?

I can't say, as using an UNAPPROVED test isn't listed in the APPROVED service manual. Nor would I **EVER** suggest that what we do in the field is an APPROVED procedure.

At least for the last 50 years of how I've been doing it.

Jim

 

[Gino Shtirlits]

They lost, of course, but I haven't done a prebuy in the subsequent 50 years. And I sleep well at night.

It means any A&P wants to sleep well at night and pre buy inspection means nothing just because A&P wants to sleep well at night. That's was my first question.

 

[jim73CQ]

It means any A&P wants to sleep well at night and pre buy inspection means nothing just because A&P wants to sleep well at night. That's was my first question.

And I could give a rat$ a$$ less.

Goodbye, go find a a mechanic that can translate your language into American and give you what you want. Best wishes.

Jim

 

[Kristin]

Gentlemen! My idea was not so bad. Just recently prospectively purchase Cessna150 could not reach at least 110 knots at 2500 feet above see level and 2600 rpm. Definitely I supposed problems with the engine. Later I have found 66 and 68 in compression reading (two cylinders). So I was right. I have rejected this Cessna from my wish list without any doubts. The requested price as much as $35000 is looking absolutely not reasonable for this plane. Now this guy is selling his plane at "barnstormers" and "trade a plane". Сcondolences to a buyer. I will use my simple test next times.

You have absolutely no clue about evaluating or buying an aircraft. Fortunately for all concerned, your ill informed benchmarks are likely to keep you from buying a plane, which in the long run will save a lot of people a lot of grief.

 

[Witmo]

You have absolutely no clue about evaluating or buying an aircraft. Fortunately for all concerned, your ill informed benchmarks are likely to keep you from buying a plane, which in the long run will save a lot of people a lot of grief.

I agree with the above. Most people, pilots included, don't have an understanding of the term "airworthy." Airworthiness requires that a standard category aircraft is safe to operate and that it conforms to it's Type Certificate or has been properly altered or repaired.

I've seen mechanically adept pilots pretty good at understanding the intracies of a powerplant and its operation. But many of those same pilots don't understand what to check to insure that engine conforms to its type certificate data sheet. A prospective owner needs to know that the aircraft in question is not only safe to operate (admittedly very important) but that the entire aircraft isn't a money pit when it comes time to annual and certified "legal" to operate.

A prebuy is only as good as the person's experience in inspecting aircraft and familiarity with a particular model, and the buyer's willingness to spend money on hiring that experience. A 150/152 is on the low end of complexity and its proliferation makes finding someone experienced relatively easy. Since its cost is also on the low end, risk is also low. I bought my first aircraft, a 150, before I was an A&P and I didn't do a prebuy. I did know the mechanic maintaining it and discussed its condition in detail. I didn't expect it to be perfect and in new condition and there were unforeseen expenses that no prebuy would have caught--that's what ownership entails.

Most part 91 operations don't require compliance with "mandatory" service bulletins put out by manufacturers unless the FAA issues an AD requiring their implementation or they are part of FAA approved Instructions for Continued Airworthiness. A part 91 aircraft never needs its engine overhauled--ever--provided it is inspected and repaired as necessary. A part 91 operation might use an engine with 10,000 hours since MOH but that engine might have had every part replaced at some point multiple times during that 10,000 hours of operation. Those repairs would constitute several overhauls in the agregate but since they were done individually "as necessary" they couldn't be called major overhauls since they weren't done at the same point in time.

 

[NordicDave]

Good luck finding a 50 year old plane that does book numbers and has perfect compression. There are some that will do the former, but very seldom will you see the later, and compression in the 60's is more often than not, no big deal.

Legacy (through the mid-1980s) POHs are ridiculously optimistic. Let's take Piper Arrow III POH cruise data from 1976 and 1995. 4000', 20C and 75% leaned to best power. 1976 says it should do 143 knots and by 1995 they were only claiming 135 knots. That's the same exact airframe at the same gross weight with the same engine and propeller.

Yes, and..

Remember these book values in the POH were made between the marketing department and professional test pilots. These are the MOST idealistic numbers. Remember why good CFI’s always tell us round up fuel consumption and round down TAS for a navlog and pad extra minimums?

Slight variances is an atmospheric conditions as well as very subtle changes to control surfaces or changes to the skin of the airframe like adding an extra antenna will cause some loss of cruise performance.

It takes time and perfect trim in cruise flight for extended time for an aircraft to eek out the last few percentages of speed available to the airframe. When the plane was test flown, was there a zero deflection of the control surfaces and was the rudder no more than 1° out of alignment with slip or skid?

Was the...
* Mixture perfectly at peak EGT as per the POH? Couple of knots
* Were the mechanical engine instruments perfectly calibrated? Very likely not, 1 knot or 2
* Plane freshly washed and waxed? That’s good for a knot or two.
* Prop changed and when was it repitched? Couple knots impact or more.
* A GPS antenna added to the air frame for ADS-B compliance, there’s a couple knots.
* Where the fairings snug to airframe? Couple knots

Engine compression testing says little about the engine’s performance, it’s a diagnostic tool and NOT A direct indicator of engine performance. If someone goes to the doctor for a check up they take your pulse, blood pressure, listen to your breathing, listen to your heart, maybe take an x-ray or an MRI. No doctor makes a diagnosis out of just measuring your pulse. Compression test is one of many diagnostic tools to consider for the health of an engine.

 

[mondtster]

I agree with the above. Most people, pilots included, don't have an understanding of the term "airworthy." Airworthiness requires that a standard category aircraft is safe to operate and that it conforms to it's Type Certificate or has been properly altered or repaired.

I've seen mechanically adept pilots pretty good at understanding the intracies of a powerplant and its operation. But many of those same pilots don't understand what to check to insure that engine conforms to its type certificate data sheet. A prospective owner needs to know that the aircraft in question is not only safe to operate (admittedly very important) but that the entire aircraft isn't a money pit when it comes time to annual and certified "legal" to operate.

A prebuy is only as good as the person's experience in inspecting aircraft and familiarity with a particular model, and the buyer's willingness to spend money on hiring that experience. A 150/152 is on the low end of complexity and its proliferation makes finding someone experienced relatively easy. Since its cost is also on the low end, risk is also low. I bought my first aircraft, a 150, before I was an A&P and I didn't do a prebuy. I did know the mechanic maintaining it and discussed its condition in detail. I didn't expect it to be perfect and in new condition and there were unforeseen expenses that no prebuy would have caught--that's what ownership entails.

Most part 91 operations don't require compliance with "mandatory" service bulletins put out by manufacturers unless the FAA issues an AD requiring their implementation or they are part of FAA approved Instructions for Continued Airworthiness. A part 91 aircraft never needs its engine overhauled--ever--provided it is inspected and repaired as necessary. A part 91 operation might use an engine with 10,000 hours since MOH but that engine might have had every part replaced at some point multiple times during that 10,000 hours of operation. Those repairs would constitute several overhauls in the agregate but since they were done individually "as necessary" they couldn't be called major overhauls since they weren't done at the same point in time.

Well said. I highlighted the part of what you wrote that I think is the essence of a PPI.

Many prospective buyers seem to believe that having an annual inspection completed on an airplane will determine the overall condition of the airplane and signify that it is ok to buy. As you point out, it does not; all an annual does is say that it is safe to operate and that it conforms to a set standard. I've seen some real garbage that will meet those minimum requirements.

What I'd be looking for in a PPI would be what you describe - confirm that the airplane won't be a money pit and that the overall condition/value of the airplane matches the agreed upon price. With some purchases that requires very little effort. For others, it can require days worth of work by an expert.

The handful of PPIs I've done have been a joke. No time to really look at the airplane because they won't pay anything and I advised against buying on 2/3 of the ones I've done. Then the purchaser bought them anyway. It makes no sense, why bother asking the opinion of someone deeply involved in aviation if you're simply going to ignore the findings and then complain afterward anyway?

 

[Timbeck2]

MSEE

I had to look that one up. You're becoming one of my favorite posters here. I was going to make a comment about the compression test numbers but I couldn't ever come up with something better than what you posted.

<---- just a Bachelor's in Human Resource Management which I'll never....ever...ever use.

 

[schmookeeg]

Gentlemen! My idea was not so bad. Just recently prospectively purchase Cessna150 could not reach at least 110 knots at 2500 feet above see level and 2600 rpm. Definitely I supposed problems with the engine. Later I have found 66 and 68 in compression reading (two cylinders). So I was right. I have rejected this Cessna from my wish list without any doubts. The requested price as much as $35000 is looking absolutely not reasonable for this plane. Now this guy is selling his plane at "barnstormers" and "trade a plane". Сcondolences to a buyer. I will use my simple test next times.

!

We need a facepalm emoji around here.

 

[jim73CQ]

Was the...
* Mixture perfectly at peak EGT as per the POH? Couple of knots
* Were the mechanical engine instruments perfectly calibrated? Very likely not, 1 knot or 2
* Plane freshly washed and waxed? That’s good for a knot or two.
* Prop changed and when was it repitched? Couple knots impact or more.
* A GPS antenna added to the air frame for ADS-B compliance, there’s a couple knots.
* Where the fairings snug to airframe? Couple knots

And ...

Cessna Marketing was no dummy...

*Get the LIGHTEST test pilot you can find ... and put sandbags in the back to bring the CG to absolute aft at max gross...
*Make sure the tensiometer on the aileron cables was at max permissible to keep aileron droop to a minimum...
*Don't put ANY of the antennas on the test aircraft...
*Don't put the tiedown rings on struts or under the tailfeathers...
*This is day VFR. Don't put the lights on the wingtips...
*This was before GPS precision. Was the airspeed indicator perfectly calibrated ...
*And the static source connections bolted to the max...

NOW go take the test data and always remember to round UP decimal places.

jw

 

[NordicDave]

And ...

Cessna Marketing was no dummy...

*Get the LIGHTEST test pilot you can find ... and put sandbags in the back to bring the CG to absolute aft at max gross...
*Make sure the tensiometer on the aileron cables was at max permissible to keep aileron droop to a minimum...
*Don't put ANY of the antennas on the test aircraft...
*Don't put the tiedown rings on struts or under the tailfeathers...
*This is day VFR. Don't put the lights on the wingtips...
*This was before GPS precision. Was the airspeed indicator perfectly calibrated ...
*And the static source connections bolted to the max...

NOW go take the test data and always remember to round UP decimal places.

jw

And stop this shenanigans, Generic POH’s to a model type are history, and today we have AFM’s serialized to a specific aircraft.

Kind of explains a good C150 gets 97 knots/ 112mph cruise at optimum altitude.

 

[schmookeeg]

I feel like a rube for assuming a 68/80 continental cylinder was freshly topped, since that's how mine act. Apparently only 80/80 or better will do for the true C150 connoisseur and gourmet.

YOUR PRINCE IS OUT THERE SOMEWHERE OP! KEEP KISSING THOSE FROGS!

Underneath one of the famed Ziggurats of Wichita, in Clyde Cessna's long lost tomb, could be one of the C150s he was embalmed and buried with. That's the one you want to hold out for.

 

[Timbeck2]

YOUR PRINCE IS OUT THERE SOMEWHERE OP! KEEP KISSING THOSE FROGS!

heh heh

 

[jim73CQ]

I feel like a rube for assuming a 68/80 continental cylinder was freshly topped, since that's how mine act.

The saying is that the guy at Continental designing the bottom end used to work for Caterpillar, but the jugs were designed by a TonkaTruck engineer.
jw

 

[George Mohr]

Prebuys are really vital for the unexperienced buyer (and really anyone that doesn't know the type intimately). But they are not foolproof. The thread linked above is a worst case example, but there are lots of less egregious examples including my own. I bought my 182 from a seller in Texas. I had a very reputable Cessna shop do a (pricy) pre-buy, and they gave the plane a clean bill of health, with the exception of a short punch list. So I purchased the airplane.

• On the flight home, after about an hour in the air, the alternator cut out. Resetting it would work for a short time, but then it would fail again. This led to a full charging system replacement.
• After a couple of weeks, a leak became apparent in the left fuel tank. This started me down a rabbit hole and cost a TON of money.
• Transmitting a longer message on com2 would swamp out the GPS signal to the 430, causing it to lose position and have to reacquire

Problems like these are hard to spot on a pre-buy, and can be very costly to diagnose and fix. So don't think it is a golden bullet when purchasing.

My best advice aside from the pre-buy, is to buy the plane from a private owner who loved it and flew it regularly. And hope they are honest about the squawks.

-G

 

[Jdm]

For some reason most buyers don’t even consider having the airplane test flown by a professional. Probably because they were taken for a flight by the seller or the broker had someone take them up. I normally offer to do a full test flight with my prebuys. I always find inflight items that would not have been identified on the ground as a mechanic. My goal on a test flight is to evaluate every system and put every piece of equipment to work until I determine it’s capable of performing as it should. It’s crazy the things we find!

The seller usually explains the discrepancy by saying “Oh that thing hasn’t worked for years”, or “It just does that sometimes”, or “that’s something you have deal with on this type airplane”, or “Its not even worth having that old thing fixed”.
I had one guy who kept saying the most annoying damn thing! “I keep this one in top shape because my family’s on board”. Of course it was one of the more illegal and neglected airplanes I’ve ever seen in my life!

 

[guzziguy]

Gino Shtirlits said: ↑
If a plane has valid annual? Can I trust to it and avoid pre-buy inspection?

I'd never trust an annual not done by my own mechanic (or at least one I trusted very highly).

WARNING!!
I bought my aircraft with exactly this scenario. Perhaps my experience can be an warning to you?
When I found my aircraft, I was told by the broker (i'll never buy another aircraft from him again) that the previous buyer backed out after his prebuy and that the owner had addressed all the issues that the previous pre-buy discovered. This led me to believe that a pre-buy would not be necessary (I know, I know). I was also told that while the items were repaired, it was turned into an annual, so I was walking into the deal with a 'fresh annual' and all items repaired from the previous pre-buy.
So why should I spend $$$ on a pre-buy only to confirm what was already found/repaired? (I know I know)
Turns out the mechanic was a friend of the seller and completely pencil whipped the annual. I flew it across the country like this and when it was time to do my first annual with the plane, I was shocked to discover how poor shape the plane was in. My mechanic told me I was lucky to be alive and he even told my story to his OTHER A&P friends.
A short list of findings on a supposedly 'freshly annualed' airplane:

1. Alternator hanging loose on its bracket
2. 3 or 4 dead spark plugs
3. corroded through empennage skin under the battery box
4. prop hub rusted beyond repair requiring replacement
5. propellor requiring replacement
6. 60 year old hoses
7. frozen/dragging brakes with lines filled with gooey brake fluid
8. loose fittings on the landing gear
9. mis-rigged (I knew about this one and was just living with it)
10. Brake linings and brake calipers requiring replacement
11. rusted through risers on the exhaust
12. I'm sure I'm forgetting a few things...

Since then, I've been slowly replacing those items that the piece of crap previous owner neglected on the plane, namely:

• New Alternator
• New Starter
• New Power Pack
• 2x new magnetos (OH'd)
• New ignition harness
• New hoses
• A bunch of nitnoid stuff...

Incredibly, doing all this, I was also still able to modernize the panel and redo the interior. My new CFII commented yesterday on how smoothly the plane ran. Yeah, hard won, my friend!

 

[mondtster]

For some reason most buyers don’t even consider having the airplane test flown by a professional. Probably because they were taken for a flight by the seller or the broker had someone take them up. I normally offer to do a full test flight with my prebuys. I always find inflight items that would not have been identified on the ground as a mechanic. My goal on a test flight is to evaluate every system and put every piece of equipment to work until I determine it’s capable of performing as it should. It’s crazy the things we find!

The seller usually explains the discrepancy by saying “Oh that thing hasn’t worked for years”, or “It just does that sometimes”, or “that’s something you have deal with on this type airplane”, or “Its not even worth having that old thing fixed”.

Not only is this true for a PPI but it is also true for annual inspections. I've found all sorts of things while test flying airplanes that potentially would go unnoticed during an annual inspection if I didn't have the opportunity to fly before and/or after working on it. As you note, many of those things get dismissed as "it has always done that" or "sometimes it works" when the owner is presented with the findings from the test flight. Maybe it has always had a problem but that doesn't make it acceptable.

I had one guy who kept saying the most annoying damn thing! “I keep this one in top shape because my family’s on board”. Of course it was one of the more illegal and neglected airplanes I’ve ever seen in my life!

That seems to be the mantra of many owners in my area. The pilots who are the most resistant to recurrent training and the owners that are the most resistant to actually fixing things are the often the ones that need the most help. Thankfully there are plenty of other instructors and mechanics that will take these guys on so I don't have to worry about it.

 

[Gino Shtirlits]

So finally. I appreciate all your responds, gentlemen. I have found the following:
- senior mechanic doesn't want to do pre-buy inspection because he wants to sleep at night quietly.
- junior mechanic would make pre-buy but he is junior.
I have bought my C150 without pre buy just basing on my experience, education background and logical judgment. I am happy with my plane now.
Also I was recommended here to study English. I really appreciate this recommendation, definitely I have to but I am too old. I am more than 60 and it would be pretty difficult for me.

 

[samiamPA]

Congrats and good luck with your airplane, I hope it is as trouble free as my 150 has been.

Be sure to sign up for the 150/152 club, it is WELL worth the membership price.

 

[WannFly]

So finally. I appreciate all your responds, gentlemen. I have found the following:
- senior mechanic doesn't want to do pre-buy inspection because he wants to sleep at night quietly.
- junior mechanic would make pre-buy but he is junior.
I have bought my C150 without pre buy just basing on my experience, education background and logical judgment. I am happy with my plane now.
Also I was recommended here to study English. I really appreciate this recommendation, definitely I have to but I am too old. I am more than 60 and it would pretty difficult for me.

Congrats on the bird.

Don’t take the “you should learn better English “ too personally, I know there are some people here who would get hung up on it and start acting like 4rth grade school teacher seemingly forgetting that it’s a means of communication and that’s all it matters. There is a place for first class English or any language for that matter, online pilot forum is definitely not one of them.

 

[Gino Shtirlits]

Be sure to sign up for the 150/152 club, it is WELL worth the membership price.

Sure! Where could I find out the club? Thank you.

 

[Gino Shtirlits]

Don’t take the “you should learn better English “ too personally,

Definitely I must confess English is not my first language. Thank you for your words.

 

[Gino Shtirlits]

My best advice aside from the pre-buy, is to buy the plane from a private owner who loved it and flew it regularly. And hope they are honest about the squawks.

I have bought my Cessna from private owner who flown regularly.

 

[455 Bravo Uniform]

Sure! Where could I find out the club? Thank you.

https://www.cessna150-152club.com

 

[somorris]

Welcome to airplane ownership, Gino! I hope you get many, many hours of enjoyable and trouble free flying!

 

[pfarber]

Repeat after me:

An annual/100 means on THAT day the aircraft was airworthy. So 1 day out of 365 an MX has said officially it's in compliance. The other 364 days it's up to the owner/operater/PIC

 

[steingar]

I looked at an aircraft I nicknamed "eyesore", because the paint was so bad. On preliminary inspection the aircraft looked otherwise OK, and was priced such that a paint job would not have me spending more on the aircraft than its actual value at the time. Had I bought the aircraft sans inspection I would have bought some lovely spar cap corrosion which takes as much money to fix as a much nicer aircraft would be worth. Indeed the next time I saw eyesore was at an aircraft scrapyard where it had been relegated due to said corrosion.