aircraft engine sealants

[astjp2]

https://www.savvyaviation.com/wp-content/uploads/articles_eaa/EAA_2013-04_a-little-dab-ll-do-ya-in.pdf

Another article from Mike Busch

[Robert Lees]

Thanks Tim for the reminder (although I already knew that cylinder hold-down torque is very critical)

Rob

[at7615]

Enjoy! You have to hold the opposite nuts on through bolts, common sense but missed by some unfortunately!

http://pceonline.com/wp-content/uploads/2017/04/M-0standardpractice2017-01-15.pdf

[3Dreaming]

I was trying to fix some oil leaks on a gentleman's 172 once. I found 2 cylinder base nuts missing and laying in the inner cylinder baffle. I called Lycoming and ask what should be done. It was suggested to reinstall the nuts and go through the whole cylinder torque procedure, which I did. Upon run up the engine ran for about 30 seconds before the propeller came to an abrupt stop, and it could not be moved easily by hand. I made another call to Lycoming and spoke with a different rep. He said now the fix is easy to figure out, "You have to tear the engine down and split the case. On disassembly I found RTV on the cylinder bases on all 4 cylinders. Luckily the customer was very understanding in that I was not the cause of the issue.

I also know of a Piper Arrow that had a cylinder separate in flight, with a forced landing on the main airport in Knoxville TN. The cause for the separation according to the FAA was a cylinder replacement and not following proper cylinder torquing techniques.

[at7615]

You have to be careful when the torque is removed from the cylinder through bolts. I do not agree with MIke about being afraid to change cylinders, I change them often. Follow the maunuals and procedures and all will be good. Adding RTV in places it does not belong is a recipe for disaster. When I was a technician in the Air Force, every manuals first page stated that "A TECHNICAL ORDER IS A WRITTEN ORDER" which meant if you deviated from the manual you violated a written order! All kinds of nasty things could happen then!

[astjp2]

You have to be careful when the torque is removed from the cylinder through bolts. I do not agree with MIke about being afraid to change cylinders, I change them often. Follow the maunuals and procedures and all will be good. Adding RTV in places it does not belong is a recipe for disaster. When I was a technician in the Air Force, every manuals first page stated that "A TECHNICAL ORDER IS A WRITTEN ORDER" which meant if you deviated from the manual you violated a written order! All kinds of nasty things could happen then!

Yeah, I put an F-15c on black letter initial, first time it had ever been done on base, QA found out, and sent 5 inspectors one from each specialty out, they found one screw in the wrong place on a pylon, I got written up for a DSV because I dared to have an aircraft on black letter initial. So I did it again the next day, same 5 inspectors show up...no defects noted and it flew 3 flights that way...so I get following the manual.

[Guest]

I was trying to fix some oil leaks on a gentleman's 172 once. I found 2 cylinder base nuts missing and laying in the inner cylinder baffle. I called Lycoming and ask what should be done. It was suggested to reinstall the nuts and go through the whole cylinder torque procedure, which I did. Upon run up the engine ran for about 30 seconds before the propeller came to an abrupt stop, and it could not be moved easily by hand. I made another call to Lycoming and spoke with a different rep. He said now the fix is easy to figure out, "You have to tear the engine down and split the case. On disassembly I found RTV on the cylinder bases on all 4 cylinders. Luckily the customer was very understanding in that I was not the cause of the issue.

I also know of a Piper Arrow that had a cylinder separate in flight, with a forced landing on the main airport in Knoxville TN. The cause for the separation according to the FAA was a cylinder replacement and not following proper cylinder torquing techniques.

Hi Tom,

That was unfortunate about the 172. Were you able to understand why installing and torquing the base nuts "seized" the engine?

I am curious about that.

Were the nuts on thru bolts? If so any theory about how the RTV effected that?

Were they merely deck nuts? If so any theory there?

Thanks, Dave R.

[3Dreaming]

Hi Tom,

That was unfortunate about the 172. Were you able to understand why installing and torquing the base nuts "seized" the engine?

I am curious about that.

Were the nuts on thru bolts? If so any theory about how the RTV effected that?

Were they merely deck nuts? If so any theory there?

Thanks, Dave R.

Dave,

It has been several years. At least one of the nuts must have been on a through bolt. The engine seized because the torque had been loose enough and long enough for the crankcase halves to fret. When the nuts were tightened back down it squeezed the crankcase halves together taking away the clearance between the bearing and the crankshaft.

For the RTV, the cylinders are designed to be metal to metal contact. The RTV creates a cushion, and prevents the metal to metal contact when torqued. With time the RTV compresses and allows the torque to loosen. The loosened torque allows the engine to wear in places it is not designed to wear. This wear aggravates the loosening of the torque. This is what allowed the nuts to come loose and the case halves to wear. In the original post it is what allowed the cylinder to separate.

[Ragwing nut]

Would it not have been better to post a link to the Continental M-O rather than Mike Busch propaganda? I can't stand his "Sky is falling, here it first on the 10 'o clock news" articles.

[at7615]

Well, I change cylinders, oil pumps, rebuild engines, whatever is required. The opposed air cooled engine is designed to be field serviceable by competent personnel. I have no problem changing all 4 jugs at the same time for a TOH, "get er done". My Tq wrenches are calibrated annually, have current data, and ensure completion of all steps. Doing my Job. Mike is overreacting to a problem that is experience/training related. GA is a completely different world from military or commercial. I worked in helicopters for decades and that will put the fear of God in any sentient being! It goes south real quick in that world! So to me GA is an Oasis of clean fun twisting wrenches and turning props. And I get to fly the birds for the maintenance check flight when done.