A $5000 annual and I get to take my airplane home in pieces

[Bill Greenwood]

Eric I don't think your problem is that the airplane was certified. That just means it met some minimum standards back then. Maybe you can save some money doing some of the work yourself, but to be safe that work still has to be done at a reasonable level. Compression of only 40to 45 is pretty low and almost certainly something in there is worn. Maybe rings, maybe a valve, but it is unlikely to fix itself. And you say, "it might be true" as if you think the a a&p is not telling you the truth. You should stand right next to him when he does the compression test and look at the figures on the gauge yourself. One way to tell if the wear is valves is to listen at the exhaust when the pressure is in the cylinder and see if you hear where the air is espcaping. If not valves, put at small amount of oil into the cylinder to seal the rings and retest.

Do you think you could buy a 54 year old automobile, for a rock bottom price, perhaps $2000 and have it be in excellent
shape and not need any service? Wish you could but in airplane terms that is not realistic.

Can you buy a flying RV for $20,000 and if so how good a plane is it?

Still, $5000 for an annual sounds awfully high. What did they do, was it something major like replacing the fabric?

Hope you get it right in the end and enjoy flying.

[Eric Marsh]

Bill, I think that the compression was low - I'm more interested in why. The engine had less than 100 hours since being gone though. We live in a replace it rather than fix it world and the shop's solution was to replace the cylinders. My approach is to examining them and see if they are in suitable shape to correct the problem without complete replacement and hopefully save myself a thousand or so.

The deal here is that the aircraft had passed the previous annual and I simply did not anticipate this kind of expense. The most major thing that was done is that the bungies were replaced. Fifteen hours went into building an AD log.

I don't think that comparing a $20k (not $2k) Tripacer to a $20k RV is reasonable. The going range for Tripacers tends to be between about $15k-$30k.

Anyhow, I'm heading down now to yank the wings.

[martymayes]

Eric, I'm curious. Was the annual inspection completed?

[Eric Marsh]

I believe that it's still open while I get these issues sorted out.

[tom_walter]

Mike Busch had an excellent column in the June 2012 Sport Aviation on one owners "low compression" reading. A recent article by Mike outlined ground rules for shops doing annuals, well written. Not sure what month that was.

I'm slowly building my Bearhawk, but keep looking for a "cheap plane, something to fly while building". Uh, I think I remember why I'm building after reading everyone's comments.

Tom

link to article:
http://www.oshkosh365.org/saarchive/.../2012_6_11.pdf

[tom_walter]

Two articles by Mike Busch worth reading:

"Is your engine airworthy?"
http://www.oshkosh365.org/saarchive/.../2010_4_25.pdf

Talks about why NOT to trust compression readings.

How to flunk an annual Inspection
http://www.oshkosh365.org/saarchive/.../2012_3_13.pdf


I'll keep looking for the one about annuals and dealing with shops.

Tom

[Eric Marsh]

Tom, thanks for the links. I just read the one about compression. My oil consumption has gone from about a quart every 3 hours to one about every 5 1/2 as the engine has broken in. The FAA inspector is going by Lycoming's statement that anything under 80/60 is un-airworthy. I suppose if you are going by the book you are going by the book. I was doing a little math in my head and inserting some guesses into the variables and here's my line of though.

You have a 160 hp engine where two cylinders are at 50% compression (for the sake of round numbers). What is that going to do to the production of power? My experience with cars is that you might feel a low cylinder at idle but not at higher speeds because there's less time for the compression to leak down. Undoubtably it's not as good as the perfect cylinder but how bad is it? Anyhow, lets say just for the sake of argument (and this may be way off) that 50% compression equates into a 50% power loss. So two holes are making 20 hp each instead of 40 hp and the 160 hp engine is only making 120.

That's almost as much as the first year Tripacer made (125 hp) and it's more than the Tripacer Colt made with it's 108 hp engine.

Be that as it will. It's a moot point at this time anyway.

The wings are off and she's ready to come home.

[tom_walter]

Irony is they are not at 50% compression.

Once warmed up, they will seal up nicely, and you have full power. If you climbed out at 800 fpm, that is a strong engine!

I suspect if most mechanics tested the compression after a full rebuild, they would be shocked to see low numbers. Sigh, as the article from Mike points out time to look at the complete engine, not just a compression reading.

[Tom Downey]

Read what you can about dynamic compression, where the leak can't loose enough air in the time it takes to make the compression stroke and ignition. which isn't enough to effect the operation of the engine.

The guidance given by the FAA is only that. but it is thought of by many A&P-IAs as law.

[Kyle Boatright]

Read what you can about dynamic compression, where the leak can't loose enough air in the time it takes to make the compression stroke and ignition. which isn't enough to effect the operation of the engine.

The guidance given by the FAA is only that. but it is thought of by many A&P-IAs as law.

Tom is absolutely right here. Low compression doesn't mean the engine is necessarily down on power. However, something is amiss in those two cylinders - bad rings, stuck rings, bad valve, etc. A ring could unstick. Or a defective ring could break and allow chunks of iron to fall into your sump - that could get really expensive.

Tom - what does a mechanic typically charge to pull and reinstall a Lycoming cylinder, assuming no work is done to the cylinder? I realize the baffles are probably as much trouble to remove as the cylinder itself.