Ugly Crank

[Brad Brady]

If George has strengthened me out you will see a REALY ugly journal....I'm planning to send the crank to Aircraft Specialities service, just because I have used them before, and like their work. Does anyone have a shop they like better......just looking for options.What really gets my goat about this crank, is all the journals measure .001 off new minimums ...for a 55 year old engine just goes to show how bullet proof these engines really are.....

PC010002.JPG

[mrpibb]

Aircraft spec. allways gets our work, seemed to be the best turn around. We send our cams and other steel parts to them too.

[alaskan99669]

Were you expecting to find some internal damage when you tore the engine down (eg. making metal or other signs), or was the engine tore down for other reason? Just curious. Thanks.

[Brad Brady]

Were you expecting to find some internal damage when you tore the engine down (eg. making metal or other signs), or was the engine tore down for other reason? Just curious. Thanks.

I was expecting to find bad stuff.....We lost oil pressure on the way to a flyin...about five miles out of the pattern...flew back and landed, by the time we rolled out the engine was making screaming noises.The funny part is there were no changes in the oil temp or cyl. head temps on the flight back! I thought that is was our gauge went south.....so the landing was just precautionary.....Until I threw off my headset, and heard the engine

[alaskan99669]

...We lost oil pressure ...

Did you find out the cause of the loss of oil pressure?
Thanks again.

[Brad Brady]

Did you find out the cause of the loss of oil pressure?
Thanks again.

Not for the reason that we lost oil pressure....The only thing I can think of is the HUGE hole we created in the #6 rod journal. Every thing else in the engine looked good.....like I said all the other journals were .001 off new minimum standards.....Sooo...I don't think we lost flow.....just pressure. When we had the runway made, and pulled power, oil pressure came back.....not good but good enough......I think that's when the crease in the right seat happened....(from my butt cheeks clenching a vast amount of upoholstry and cushion) I then knew we had a real problem. last annual's compressions were #1 60/80 #2 70/80 #3 70/80 #4 64/80 #5 69/80 #6 74/80. When disassembling the engine, I found no top ring in #4 cylinder.... Pryor to disassembly, I thought for giggles, I would do a compression check.....after the failure the compressions were #1 65/80 #2 70/80 #3 70/80 #4 60/80 (with no top ring) #5 72/80 #6 74/80 Number five cylinder, is the only one that didn't have a broken top ring.... Here's a pic of the #4 piston and like I said all the ring went out that hole at the top and seemingly did no damage to the valve or seat......Go figure Also this was an ongoing problem that a compression check didn't find......That ring left many hours ago.......

[alaskan99669]

Wow, that's some impressive damage. I was hoping you found the smoking gun that led to the whole event so that maybe others could avoid the same fate. May we all be as fortunate to make it to an airstrip should such a failure happen to us!

[Brad Brady]

Wow, that's some impressive damage. I was hoping you found the smoking gun that led to the whole event so that maybe others could avoid the same fate. May we all be as fortunate to make it to an airstrip should such a failure happen to us!

Corey,
That is the smoking gun, #4 piston......The pan was full of crap...(the only way I can describe it) that over many hours was passed by the bad pistion to the oil and accumilated apparently at the #6 rod journal causing it to fail.....the rest is history...

[alaskan99669]

......That ring left many hours ago.......

When you said "many hours ago", I was thinking you meant "several". So do you think more frequent oil changes and inspection of the internals of the oil filter would have possibly shown the warning signs? Maybe since filters are cheap (relative to 8 quarts of oil), one could change the filter twice as often as the oil to inspect for such contamination.

[Brad Brady]

[/quote]
So do you think more frequent oil changes and inspection of the internals of the oil filter would have possibly shown the warning signs? Maybe since filters are cheap (relative to 8 quarts of oil), one could change the filter twice as often as the oil to inspect for such contamination.[/quote]

Corey,
Dad has had an oil filter on that aircraft since I was about 15 years old........I'm the reverse of that now...I've been cutting his filters for 30 years now.....Continental and lycoming say that if you see enough metal to cover your thumb nail......(I guess that's where a thumbnail perspective comes from)....You should check out the problem...I have never seen that much metal...until the last oil filter opening.....(Have seen a lot of carbon in the last three years.....but that's not what I'm looking for).....Maybe I should!!! I'm Taking another tact at looking at filters now.......But another thing I'm looking at is the age of the overhaul......Dad's was 33 years ago......I guess maybe it might be prudent to look at the internal components of an engine a little quicker than that.........

[GAHorn]

Brad, were any rings stuck in their lands other than the top rings? And were you cognizant as to whether or not the broken rings were installed upside down?

I ask because I have seen an engine that ran for many years just fine but when disassembled, the rings on 3 cylinders were broken and all the broken rings were installed upside-down. They were stuck in the lands, of course. Good compressions. Engine just timed out.

[Metal Master]

I have seen piston damage like that before. I am not saying this was the cause. However I can tell you it took only one flight to do the damage. The piston looked exactly like the one pictured here and the damage was done on a flight from Boise Idaho to Friedman in Haley Idaho. The culprit was the magneto firing to the wrong cylinder through a carbon trace inside the distributor block of a Bendix overhauled S-20 series magneto. The magneto only had twenty hours on it. It completely destroyed the crank and filled the engine with metal which could be seen in the bearing shells. TCM who rebuilt the magneto would only cover the cost of the Magneto even though it was the cause of the engine being scrapped. This one sort of miss firing known as Detonation.

Jim

[Brad Brady]

Brad, were any rings stuck in their lands other than the top rings? And were you cognizant as to whether or not the broken rings were installed upside down?

I ask because I have seen an engine that ran for many years just fine but when disassembled, the rings on 3 cylinders were broken and all the broken rings were installed upside-down. They were stuck in the lands, of course. Good compressions. Engine just timed out.

George, Every thing was as it was supposed to be....the broken rings were due to heat build up on final.....I surmise....I quit looking at the cyl. temps when I started pulling seat fabric (all rings were freshly broke except the one that was missing)

[Brad Brady]

I have seen piston damage like that before. I am not saying this was the cause. However I can tell you it took only one flight to do the damage. The piston looked exactly like the one pictured here and the damage was done on a flight from Boise Idaho to Friedman in Haley Idaho. The culprit was the magneto firing to the wrong cylinder through a carbon trace inside the distributor block of a Bendix overhauled S-20 series magneto. The magneto only had twenty hours on it. It completely destroyed the crank and filled the engine with metal which could be seen in the bearing shells. TCM who rebuilt the magneto would only cover the cost of the Magneto even though it was the cause of the engine being scrapped. This one sort of miss firing known as Detonation.

Jim

Yea Jim, I know what you are saying.....The failure had nothing to do with timing......(IE magneto)....It had every thing to do with timing....The age of the overhaul.....In my belief....which may be wrong After landing I asked Dad, "since we cheated death once today.....do you want to take my plane or drive"......We drove....at the fly-in I saw the engine re-builder and asked if he was going to stand behind his engine after 35 years

[Brad Brady]

Kinda on this topic, today my summer time boss, Dave, (I fly a gear nose Thrush for him) asked me what were the limits on an overhaul.....who could overhaul an engine ....what were the time restraints, and who was responsible for the engine ...and for how long?......That last question just smacked me up side of the head......I guess for the time that the engine is running.....I'm responsible......that sucks.....after all I was just kidding with the rebuilder of dad's engine.....but after all he is still responsible.....It's just were friends and we would never put that on his head....still if I'm rebuilding an engine for a friend.....where do I stop my responsibility?...with out my insurance coverage .....and where do they say I'm on my own?......some interesting questions that came up with a couple quick questions....