It happened again...

[tsts4]

Wow -- this almost a perfect case study in improper engine diagonistics. With the bad compressions you listed, there should have been other signs something internally in the engine was amiss - excessive oil consumption, trending oil analysis, etc. IMO, absent any other indicators and the fact the engine at least appeared to run strong, this should have been enough for the mechanic who did the test to dig deeper right then.

 

[Jay Honeck]

Wow -- this almost a perfect case study in improper engine diagonistics. With the bad compressions you listed, there should have been other signs something internally in the engine was amiss - excessive oil consumption, trending oil analysis, etc. IMO, absent any other indicators and the fact the engine at least appeared to run strong, this should have been enough for the mechanic who did the test to dig deeper right then.

Agree 100%. The seller is understandably furious, and probably despondent. We probably would have flown home with that plane, were it not for that bogus compression check.

I would NOT want to be that first mechanic right now. Thank goodness the buyer found him, not me.

Sent from my Samsung Galaxy S3...

 

[JHW]

Wow -- this almost a perfect case study in improper engine diagonistics..

the owner shares an equal amount of blame if didn't call BS on 4 bad cylinders knowing his plane ran fine

 

[wabower]

Mike B. said they degraded all compressions to less than 40 psi and still made rated power on the dyno.

the owner shares an equal amount of blame if didn't call BS on 4 bad cylinders knowing his plane ran fine

 

[docmirror]

And another 'bad cyl o-haul' story comes apart.

 

[Ted]

Mike B. said they degraded all compressions to less than 40 psi and still made rated power on the dyno.

When I did the top overhaul on the Aztec's left engine early on, all 6 cylinders were failing. Plane ran great, no problems.

Observable difference after putting on new cylinders: my wallet was lighter.

 

[docmirror]

Mike B. said they degraded all compressions to less than 40 psi and still made rated power on the dyno.

Conti built a O-470 without any compression rings at all once and it made rated power on the dyno. Of course, that was with no leaky valves but still...

 

[tsts4]

the owner shares an equal amount of blame if didn't call BS on 4 bad cylinders knowing his plane ran fine

Concur! Especially with a really low number like a 36. With number like that, I would assume there would be significant oil loss with every engine run due to blowby pressurizing the crankcase and blowing oil out the breather. In any event, I'd never pull a jug just on the basis of a compression test. All the test would do is trigger additonal diagnostics like a bore scope.

 

[tonycondon]

Conti built a O-470 without any compression rings at all once and it made rated power on the dyno. Of course, that was with no leaky valves but still...

so the only point of the rings is to slow down the rate of oil burn?

 

[docmirror]

so the only point of the rings is to slow down the rate of oil burn?

Not what I said. All I know is they built one to prove it would make rated power when the old orifice gauge was reading ~40/80 on the leakdown.

I also presume, but don't know that the rings are to minimize blow by into the crankcase which can cause many other issues.

 

[Skylane81E]

Concur! Especially with a really low number like a 36. With number like that, I would assume there would be significant oil loss with every engine run due to blowby pressurizing the crankcase and blowing oil out the breather. In any event, I'd never pull a jug just on the basis of a compression test. All the test would do is trigger additonal diagnostics like a bore scope.

Negative,

I have seen mid 70 compression engines blow nearly a quart an hour (broken oil control rings found on disassembly) and low 30s run great with no appreciable oil use.

 

[Skylane81E]

What I do what to know is why the mechanic didn't flag on the the noise a compression tester makes when it is leaking like that.

It happened to me yesterday, had a cylinder score "only" 60/80 when the rest were in the mid 70s and there could be no doubt that the air was coming from the spark plug hole. A quick spin of the wrench and it was 72/80

 

[tsts4]

Negative,

I have seen mid 70 compression engines blow nearly a quart an hour (broken oil control rings found on disassembly) and low 30s run great with no appreciable oil use.

Got it, but that reinforces my stance that a compression test by itself is not the basis to do anything other than more diagnostics to determine if there really is cause for concern.

 

[Skylane81E]

Got it, but that reinforces my stance that a compression test by itself is not the basis to do anything other than more diagnostics to determine if there really is cause for concern.

I can agree with that, I am less concerned with the number than I am with the source of the leak

 

[Jay Honeck]

What I do what to know is why the mechanic didn't flag on the the noise a compression tester makes when it is leaking like that.

It happened to me yesterday, had a cylinder score "only" 60/80 when the rest were in the mid 70s and there could be no doubt that the air was coming from the spark plug hole. A quick spin of the wrench and it was 72/80

What has me baffled is that we all heard the air hissing from the worst cylinder -- and it definitely got louder when he pulled the oil dipstick.

Sent from my Samsung Galaxy S3...

 

[Skylane81E]

Well are you positive that the owner is being truthful about the new results? I have never not known when a connection on the tester was leaking.

 

[Jay Honeck]

Well are you positive that the owner is being truthful about the new results? I have never not known when a connection on the tester was leaking.

I'm not there to verify it, but I believe the seller. He's a straight shooter, and we feel terrible about the way this whole thing went down.

From my end, it was a good, if harsh, learning experience. From his end, it was financially disastrous.

 

[RotorAndWing]

My bro-in-law used to work for a law firm that was counsel for one of the major aircraft manufacturers.

I was at a holiday party at his house once and I got on the topic of flying with a group of folks. I ended up telling them about how my dad and I built an airplane in the basement/garage. They said they typical "Oh my. And you feel like you can build an airplane safe enough to fly in!?" My b-i-l broke into the conversation and said "I have seen and dealt with the people that put together the 'real' airplanes. I definitely trust him (me) more than I trust those guys!".

I'm not sure why people continually think that the only people that can pound rivets are the $15/hr assembly line workers at the spam-can factories.

Those assembly lines have "Quality Control" overseeing the process.

While I was at the FAA I got to see my fair share of E-AB's in both certification and accident investigation. The E-AB community does mean job security for the Feds

 

[Ted]

Those assembly lines have "Quality Control" overseeing the process.

While I was at the FAA I got to see my fair share of E-AB's in both certification and accident investigation. The E-AB community does mean job security for the Feds

The problem with E-AB will always be that Joe Planebuilder can either be good, intelligent, and conscientous or a complete idiot. Since most people in the world are idiots, well...

 

[tonycondon]

The problem with E-AB will always be that Joe Planebuilder can either be good, intelligent, and conscientous or a complete idiot. Since most people in the world are idiots, well...

my experience is the idiots don't get too far past buying the plans/kit and putting a few pieces together. very rare that they actually get a complete plane in the air, and if they do, it is pretty obvious to anyone who has seen an airplane that the work is sub-par. Most Ex-AB that i've been around show a high level of workmanship.

 

[Ted]

my experience is the idiots don't get too far past buying the plans/kit and putting a few pieces together. very rare that they actually get a complete plane in the air, and if they do, it is pretty obvious to anyone who has seen an airplane that the work is sub-par. Most Ex-AB that i've been around show a high level of workmanship.

I think you've got two different circles. You and I (and most of the folks here) tend to be in the circle of folks who are good and have good workmanship. So it makes sense that what we see are planes that look good and are safe.

Then there's the cowboy circle. And the accident records seem to indicate that Clyde did a better job building my 310 in his garage with a few buddies than the cowboys. They also seem to indicate a number of cowboys. My guess is those folks seldom come out into the open because they don't want to draw attention to themselves.

 

[wabower]

I think interest, aptitude and patience are the necessary characteristics. I'm 0-for-3 in those areas, found it to be tedious as hell and wouldn't dream of trying to build an airplane. It's not necessarily about just being smart, it's about being smart in the areas in which you need to be smart to achieve what you need. Whether a guy works 2,000 hours building one or works the same amount of hours and buys one doesn't really matter.

my experience is the idiots don't get too far past buying the plans/kit and putting a few pieces together. very rare that they actually get a complete plane in the air, and if they do, it is pretty obvious to anyone who has seen an airplane that the work is sub-par. Most Ex-AB that i've been around show a high level of workmanship.

 

[Jay Honeck]

I think interest, aptitude and patience are the necessary characteristics. I'm 0-for-3 in those areas, found it to be tedious as hell and wouldn't dream of trying to build an airplane. It's not necessarily about just being smart, it's about being smart in the areas in which you need to be smart to achieve what you need. Whether a guy works 2,000 hours building one or works the same amount of hours and buys one doesn't really matter.

Precisely correct.

I've now spent an inordinate amount of time, and a fair piece of money, on just two -8As. (These are just the ones worthy of taking through to a prebuy. There have been many others in play.). However, what I have learned by participating in this process could not be purchased for any less.

Bottom line: Homebuilts are a different breed of cat, and you have to be a bit more on your game when inspecting them. In my opinion, the ones we have taken to prebuy have been superior in workmanship to certificated aircraft.

We didn't bother with ones that were obviously sketchy.

But, hey -- I got to do my first hammerhead stall, a maneuver I've always wanted to try. So it wasn't a completely wasted trip. lol

 

[RotorAndWing]

my experience is the idiots don't get too far past buying the plans/kit and putting a few pieces together. very rare that they actually get a complete plane in the air, and if they do, it is pretty obvious to anyone who has seen an airplane that the work is sub-par. Most Ex-AB that i've been around show a high level of workmanship.

There's more of the idiots out there than you think and they do move far along in the process. Like I said earlier, job security for the feds.........

 

[bbchien]

I'm not there to verify it, but I believe the seller. He's a straight shooter, and we feel terrible about the way this whole thing went down.

From my end, it was a good, if harsh, learning experience. From his end, it was financially disastrous.

I would borescope the lowest cylinder. Just for peace of mind. Somebody in the room doesn't know squat and you don't want that to be you.

 

[Seanaldinho]

But, hey -- I got to do my first hammerhead stall, a maneuver I've always wanted to try. So it wasn't a completely wasted trip. lol

Those are lots of fun!

 

[yakdriver]

One thing that no one has mentioned is that there are a lot of idiots taking care of your certificated airplanes. Just because a guy has an IA doesn't mean he is super mechanic. I have seen some very dangerous stuff but it was signed off and there are IAs out there that will pencil whip an annual for the right price. Don

 

[JHW]

One thing that no one has mentioned is that there are a lot of idiots taking care of your certificated airplanes. Just because a guy has an IA doesn't mean he is super mechanic. I have seen some very dangerous stuff but it was signed off and there are IAs out there that will pencil whip an annual for the right price. Don

ayep. I went 2 years in a row where I was traveling a lot so I turned the plane over to the shop to do the annuals and i didn't participate. I wouldn't have thought a grease gun was difficult to figure out, but apparently it was too much for this guy. So the next year i got to write a $21k check for 2 new propellers and it's a lesson learned about what do do if you want it done right.

 

[Jay Honeck]

ayep. I went 2 years in a row where I was traveling a lot so I turned the plane over to the shop to do the annuals and i didn't participate. I wouldn't have thought a grease gun was difficult to figure out, but apparently it was too much for this guy. So the next year i got to write a $21k check for 2 new propellers and it's a lesson learned about what do do if you want it done right.

Since we moved to Texas, and took on this multi-year renovation project, I haven't had time to do "owner-assisted" annuals. I have been nervous about them since, although I have zero evidence that my mechanic has skated on anything.

I just feel better about my plane when I've participated in the inspection.

WRT the mechanic who screwed up the simple compression check on this RV, I have only sympathy. He seemed entirely competent, and if his equipment was flawed, it's hard to fault him.

The consequences of this failure to the seller were so out of proportion with the problem -- the loss of $80K for lack of a 10 cent O-ring -- make this whole episode sickening.

 

[Chip Sylverne]

The consequences of this failure to the seller were so out of proportion with the problem -- the loss of $80K for lack of a 10 cent O-ring -- make this whole episode sickening.

The seller didn't lose $80k, all he lost was a sale to you. Unless, of course, you're the last RV buyer on earth. Unfortunate, but not sickening. You discovered you really want a controllable pitch prop. He still has a pristine airplane he can sell to someone who can live with the Catto. I mean, it's not like the test went into the logs.

I am of the opinion everything happens for a reason.

 

[N801BH]

Since we moved to Texas, and took on this multi-year renovation project, I haven't had time to do "owner-assisted" annuals. I have been nervous about them since, although I have zero evidence that my mechanic has skated on anything.

I just feel better about my plane when I've participated in the inspection.

WRT the mechanic who screwed up the simple compression check on this RV, I have only sympathy. He seemed entirely competent, and if his equipment was flawed, it's hard to fault him.

The consequences of this failure to the seller were so out of proportion with the problem -- the loss of $80K for lack of a 10 cent O-ring -- make this whole episode sickening.

Personally I am confused on the 80,000 (Yesterday, we looked at one that was absolutely pristine, and flew like a dream, but failed the engine test, RV-8A.........

The guy wants to sell it, the motor has now been found to be a good one... You don't want a Catto prop. The owner still wants to sell the plane...

Offer him 5 grand less and put another brand of fixed pitch prop on it yourself.

You loose 3-5 mph in cruise speed and gain 60+ lbs in useful load with the fixed pitch... And considerably cheaper conditional inspections for years to come without a constant speed prop....


Am I seeing this wrong???

 

[RotorAndWing]

One thing that no one has mentioned is that there are a lot of idiots taking care of your certificated airplanes. Just because a guy has an IA doesn't mean he is super mechanic. I have seen some very dangerous stuff but it was signed off and there are IAs out there that will pencil whip an annual for the right price. Don

And the owners knows he's using a pencil whip guy and is doing so by choice. These IA's (pencil whippers) aren't "sneaking around", when they tell the owner "I'll annual your plane for $200 and we can do it in a couple of hours Saturday morning" is clue enough you're buying a signature rather than an inspection.

 

[Jay Honeck]

Personally I am confused on the 80,000 (Yesterday, we looked at one that was absolutely pristine, and flew like a dream, but failed the engine test, RV-8A.........

The guy wants to sell it, the motor has now been found to be a good one... You don't want a Catto prop. The owner still wants to sell the plane...

Offer him 5 grand less and put another brand of fixed pitch prop on it yourself.

You loose 3-5 mph in cruise speed and gain 60+ lbs in useful load with the fixed pitch... And considerably cheaper conditional inspections for years to come without a constant speed prop....


Am I seeing this wrong???

We now have set the bar at constant speed prop and autopilot. The plane we rejected due to the bogus compressions (which turned out to be just fine) had neither of those.

Thus, although we rejected it for the wrong reasons, 24 hours of reflection allowed us to narrow our search to planes that meet these new parameters.

And...we've got two of them in the bullpen as we speak...

 

[Jay Honeck]

The seller didn't lose $80k, all he lost was a sale to you. Unless, of course, you're the last RV buyer on earth. Unfortunate, but not sickening. You discovered you really want a controllable pitch prop. He still has a pristine airplane he can sell to someone who can live with the Catto. I mean, it's not like the test went into the logs.

I am of the opinion everything happens for a reason.

The only bad thing is that the RV world is tiny, and word immediately spread that his engine was "bad".

This damage will take time to undo. I'm doing my best to help, but bad news always spreads faster than good.

 

[Jaybird180]

Looks like the mechanic may have to do the honorable thing and stick his chin out.

 

[Silvaire]

I don't know any A&P mechanic that doesn't back up Chip's assertion. The difference in cost between new and overhauled cylinders is insignificant, and the performance advantage is clear. Go new, every time.

It's not quite that cut and dried. If the cylinders were all new 500 hours ago then I wouldn't be in such a rush to dump them. The problem with older engines that have had overhauled cylinders put on is that there is no real tracking on those things. You don't really know how many total hours are on them.

 

[Ted]

It's not quite that cut and dried. If the cylinders were all new 500 hours ago then I wouldn't be in such a rush to dump them. The problem with older engines that have had overhauled cylinders put on is that there is no real tracking on those things. You don't really know how many total hours are on them.

And this is why I recommend all new cylinders at overhaul for most people in most cases.

 

[Jay Honeck]

And this is why I recommend all new cylinders at overhaul for most people in most cases.

I literally don't know a mechanic who recommends using overhauled cylinders vs. new cylinders. The price delta is so small, there's just no reason to not go new.

 

[denverpilot]

So, the search continues. I now see that buying a homebuilt is a much more complex task than buying a certificated plane.

Keep in mind when you spend years of your life building something you'll probably only sell it after something makes it untenable to keep it.

Look for the pilot who lost a medical or had a personal financial disaster.

Or... Find the "serial builder" who builds and never flies it more than a year before the building bug bites again.

Anything else, something is probably wrong with their aircraft since they've put a decade of their life into it. It takes a big life change or a big problem to break that bond.

 

[Jay Honeck]

Keep in mind when you spend years of your life building something you'll probably only sell it after something makes it untenable to keep it.

Look for the pilot who lost a medical or had a personal financial disaster.

Or... Find the "serial builder" who builds and never flies it more than a year before the building bug bites again.

Anything else, something is probably wrong with their aircraft since they've put a decade of their life into it. It takes a big life change or a big problem to break that bond.

Exactly! My prime target at the moment is being sold by a wonderful guy who sadly lost his medical.

One guy's catastrophe is another guy's lucky day. 'Twas ever thus.