Aircraft UOA fact

Joined
Feb 15, 2003
Messages
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Location
Jupiter, Florida
UOA is a nice way to watch engine trends. However, it's unable to pick up large particulates, such as the typical Lycoming failure. I recently received the following:

"As an aside, I religiously sent samples to Blackstone during my last
engine run...all 1600+ hours...and all came back glowingly perfect. Even
the last one...as I was cleaning metal out of my filter"


This particular owner experienced camshaft failure, very similar to my cam failure. It's common on Lycoming IO360 engines and it DOES NOT show up in UOA results.

A picture of my camshaft failure can be found here: http://cujet.com/html/engine.html

DSC00149_resize_with_arrow.jpg
 
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There have been other cases like this too which are posted from time to time (from car/truck engines). UOA is for oil health, not engine health, but **sometimes** they can show an impending problem.

Nice photos of the engine build!
 
Originally Posted By: 2015_PSD
There have been other cases like this too which are posted from time to time (from car/truck engines). UOA is for oil health, not engine health, but **sometimes** they can show an impending problem.

Nice photos of the engine build!
This and Thanks Cujet !!
 
Thanks for the pics--always curious what these motors look like. Nice buildup too.
 
Beautiful work. A complete small plane ignoramus here. Doesn't an aircraft have to be re-certified every X amount of hours?
 
Ummm...wouldn't this tend to be a fatal failure? I guess the engine was able to limp along?

I used to chip in with a couple private pilots at my first job in TX who would rent a small plane in Dallas and fly up to a really cool catfish restaurant on the Red River in OK that had a dirt landing strip. The first time I joined them, they were meticulously inspecting the aircraft before departure and the guy checking the oil looked really puzzled. Finally, he told the other pilot that it was 8 quarts low and headed off the get some oil.
I thought really hard about bolting for my car because that sounded really bad to me, but I put my big boy pants on and stuck it out. It was really a wonderful trip and I joined them whenever I could from then on.
 
Cardinal is a very nice plane
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The cam failure could be from one of two sources. Either the lobe was soft, or one of the lifters bound up and stopped spinning ... Once that happens it wipes the taper off the lobe in a heart beat and all is down hill from there.

I noticed you had some lifter bore work done. Very wise. The bores need to be a slightly "loose" to make sure if some small debris gets in there, they can still spin.

Really nice engine work. And the interior looks very good too. You do nice meticulous work. Think I'll buy a plane and send it down for you to tinker on
laugh.gif
 
Very nice presentation Cujet. I liked the P portion of the A&P curriculum at Spartan. That was a long time ago. Never put a wrench on a "real" airplane but was successful in power generation.
 
Interesting cam lobe mod for oiling. I notice some high revving bike engines use squirters above the cams lobes, which works well also.
There was a guy on the board with a turbo Grand National that had good UOA's but the engine was in bits inside, his experience left me questioning the value of them for anything other than coolant and fuel dilution and now seeing this even more so.
Very nice work!
 
Originally Posted By: Trav
Interesting cam lobe mod for oiling. I notice some high revving bike engines use squirters above the cams lobes, which works well also.
There was a guy on the board with a turbo Grand National that had good UOA's but the engine was in bits inside, his experience left me questioning the value of them for anything other than coolant and fuel dilution and now seeing this even more so.
Very nice work!


The only way I would do a UOA would be for the condition of the oil. Dirt, fuel, or coolant.
 
Originally Posted By: tig1
Originally Posted By: Trav
Interesting cam lobe mod for oiling. I notice some high revving bike engines use squirters above the cams lobes, which works well also.
There was a guy on the board with a turbo Grand National that had good UOA's but the engine was in bits inside, his experience left me questioning the value of them for anything other than coolant and fuel dilution and now seeing this even more so.
Very nice work!


The only way I would do a UOA would be for the condition of the oil. Dirt, fuel, or coolant.


Exactly, I run the best oil I can find, keep the air filter replaced. If anything is wearing there isn't much I can do about it that doesn't involve pulling it apart. Let it blow and I will rebuild it, I rather put the UOA $$$ into better oil.
 
Originally Posted By: andyd
Beautiful work. A complete small plane ignoramus here. Doesn't an aircraft have to be re-certified every X amount of hours?


Thanks!

In the USA, small, private, piston powered aircraft, used for personal transportation, have very few requirements. An annual inspection with specific items is required, as are all applicable Airworthiness Directives.

The US Constitution really does not allow for Federal control over private individuals and their belongings. Aircraft involved in commerce is another story altogether, with very stringent rules.

Nor can we make the argument that the greater public is at risk from small aircraft accidents. As that threshold is 10 or more seats and/or 12,500 pounds and up.
 
Originally Posted By: BrocLuno


The cam failure could be from one of two sources. Either the lobe was soft, or one of the lifters bound up and stopped spinning ... Once that happens it wipes the taper off the lobe in a heart beat and all is down hill from there.



In the case of the Lycoming 4 cylinder engines, there are a few factors that contribute to the commonly worn exhaust lobes.

First, there are only 2 exhaust lobes on the cam, (4 cylinders) as each ex lobe operates opposing tappets so the lobe is made a little wider....

Second, the cam resides above the crankshaft. Where it's not well oiled upon cold startup. As it relies on crankshaft "throw off" to splash lube the lobes.

That modification with the drilled holes also includes a way for bearing oil pressure to fill the inside of the hollow cam. They put a plug in the end, with a small center hole to relieve any excess pressure.
 
Originally Posted By: Trav
Interesting cam lobe mod for oiling. I notice some high revving bike engines use squirters above the cams lobes, which works well also.
There was a guy on the board with a turbo Grand National that had good UOA's but the engine was in bits inside, his experience left me questioning the value of them for anything other than coolant and fuel dilution and now seeing this even more so.
Very nice work!


Yup, BuickGN. Had peachy keen UOA's and a buggered engine.
 
Originally Posted By: Cujet
Originally Posted By: BrocLuno


The cam failure could be from one of two sources. Either the lobe was soft, or one of the lifters bound up and stopped spinning ... Once that happens it wipes the taper off the lobe in a heart beat and all is down hill from there.



In the case of the Lycoming 4 cylinder engines, there are a few factors that contribute to the commonly worn exhaust lobes.

First, there are only 2 exhaust lobes on the cam, (4 cylinders) as each ex lobe operates opposing tappets so the lobe is made a little wider....

Second, the cam resides above the crankshaft. Where it's not well oiled upon cold startup. As it relies on crankshaft "throw off" to splash lube the lobes.

That modification with the drilled holes also includes a way for bearing oil pressure to fill the inside of the hollow cam. They put a plug in the end, with a small center hole to relieve any excess pressure.


Maybe vw507 certified oil would do a trick
grin.gif
Its low ash...like all aircraft oils...and it has special EP additive that protect cam lobes of vw PD engines
smile.gif
 
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