Strange looking cylinder wall - Page 3

sblack · #21 02-22-2016, 03:57 PM

Ok I just reread the OP so it all fits. It will be an education to see the insides. Sorry that it is at Kevin's expense but I am happy that this was all found on the ground and we will learn from it. Thanks Bill.

I watched Mike Busch's webinar called "the perils of cylinder work". It was an eye opener for sure. Highly recommend it.

Robski · #22 02-23-2016, 07:06 AM

Quote:

Originally Posted by Kevin Horton

... after consulting with three Aircraft Maintenance Engineers ... I flew the aircraft for two hours and checked the filter again. I counted 7 flakes, so I flew 10 more hours

Man, you are waaaay braver than I am!

When my engine's plugs were oily with I pulled the cylinders. Once the cases were open I found a dying camshaft, so that was that anyway!

I hope yours is just the one dead cylinder and piston and the flakes haven't done any damage to the oil pump/accessory case: the contaminated oil will have gone through that on its way from the sump to the filter!

Walt · #23 02-23-2016, 07:22 AM

Bottom line... Once an engine starts producing ferrous material in the filters/screens no amount of hoping or praying is going to fix it.

SMO · #24 02-23-2016, 09:50 AM

Kevin, wonder if this is in any way related to the overspeed event you experienced a few years ago. IIRC you had the engine disassembled and inspected and no damage was found. Two unusual events in the same engine may just be coincidence............

Kevin Horton · #25 02-23-2016, 06:16 PM

Quote:

Originally Posted by SMO

Kevin, wonder if this is in any way related to the overspeed event you experienced a few years ago. IIRC you had the engine disassembled and inspected and no damage was found. Two unusual events in the same engine may just be coincidence............

I've been wondering the same thing. The engine was disassembled and inspected by Aerosport Power after that event, but some types of damage are hard to see.

I hope to pull the jug on Saturday, assuming one of my potential helpers is available, and the weather isn't too terrible.

maniago · #26 02-23-2016, 06:34 PM

Did I miss this or have you commented on what the top of the piston looks like? Any signs of detonation hence a melted piston top at the affected area? Can happen quick...and..... it can detonate and have nothing happen to the piston. Just curious.

Kevin Horton · #27 03-01-2016, 05:53 PM

Lee, a coworker, helped me remove the #4 cylinder on Sunday afternoon. The strange cylinder wall seen during the borescope inspection was quite visible. There is definitely some wear all the way up the cylinder wall, but it isn't very keep at all. I'm guessing it is perhaps 0.001", which isn't nearly enough missing metal to explain what I found in the filter. Drat.

The piston has a stuck lower compression ring, and signs of significant blow by. The cylinder and piston would obviously need sorting out before the aircraft goes back into service, but the bigger issue is the ferrous metal in the oil filter.

Now that the cylinders have been ruled out as a source, there aren't any good options left. If it is cam or crank, then the engine needs to come off and head to an overhaul shop. If it is the oil pump, or in the accessory gear box, that could probably be sorted out here, but the engine would need to come off the mount.

I'll use a mirror and borescope to inspect what I can see of the cam from the #4 cylinder area whenever we get a break in the weather, and work allows me to get to the hangar.

Does anyone has any bright ideas on possible wear sites that could be corrected with the engine on the mount? If not, it looks like the next step is to remove a front cylinder, to get a look at that part of the cam. If that checks out, I'll have an AME (Canadian equivalent of an FAA A&P) help me inspect inside the accessory case. If nothing is seen in there, I'll ship it to an overhaul shop.

tim2542 · #28 03-01-2016, 06:54 PM

Kevin you'll most likely find the lifters going south. They fail ahead of the cam usually, so run your finger across the face of each one and check for pits, you may have to remove the rocker arms so you can run your finger under the lifter face of any cylinders still installed. So while on the way look close for broken valve springs, etc. Unfortunately you'll have to pull another cylinder to inspect the other end of the cam shaft and those lifters unless of course you find something where your at now.
You could have a look at the gears as best you can through the mag holes, or even pull the sump and look up into that area, especially the crank gear, idler gear shafts and retaining bolts. Be sure to look over the impulse coupler also.
If you have only ferrous metal, no brass, copper, al., etc its most likely going to be the cam and lifters. A bad crank bearing will throw several different metals.
Good luck
Tim Andres

sblack · #29 03-01-2016, 07:02 PM

Darn, that's unfortunate. Do you have any pics of the flakes you found in the filter?

BillL · #30 03-01-2016, 07:41 PM

Kevin, You might be able to look at the cam with your scope. Note there are some particles embedded in the skirt, and the top ring face looks rough. It is hard to tell in that photo. If the ring face disintegrated (root cause), it could cause the flakes, and then the blow-by overheated the ring (and top land) and froze the ring. Skirt FOD elevated the aluminum.

It seems too much a coincidence that you shed cam flakes at the same time as a ring failure.