aircraft maintenance questions

[rfcPilot]

I have to say Im impressed at this thread.

kwk, crooks ESPECIALLY in the computer industry Which is unfortunate. In any trade.

I do not distrust my AME, but from what I've seen on these forums I cant say I'd trust anyone here.

As you mentioned for the filters, the relief (as I mentioned already) has been replaced, because I'd rather replace a 15 dollar filter rather than a few hundreds of dollars worth of instruments.

Frankly, what started with me asking a question just turned into typical online flame wars...

[kwk]

rfcpilot, About the filters ,, sorry I was just using it as an example, I did see that you had decided to replace it already and wasn't trying to beat you up with it.

[040hurts]

rfcPilot, You got the filters changes to save some money, which in my opinion is smart, however if your 58/80 jug hasnt smartend up, you might wanna take care of that.

The Prop is like a fan, when it stops moving the pilot starts sweating.

[rfcPilot]

Yea I've got another 2 hours to go before I go in for another compression test. At that point, if it hasnt picked up, my AME suggested I get the cylinder overhauled or replaced. Seeing as the engine has only 300 hours on it (last MOH in 1993). It has a TBO of 2400. My AME figures the weakness is due to lack of flying in so many years. Probably a stuck exhaust valve is what he came to. And thats why Im putting a few hours in before another test to confirm.

[tiggermoth]

hello, i just want to say a couple things to rfc, first remember when we engineers sign our name and license number to a maintenance entry in your logbook, WE are responsible if something goes wrong, therefore we will do whatever is necessary to ensure that you are safe when you go flying. Second, you will find that if you wandered into most AMO's or even called up your engineer on the phone and asked him/her your questions they would be happy too help, just accept their advice because AME's are trained in aircraft maintenance. Just like you as a computer tech, GA AME's are a service provider and are not out to screw you over. Third if you want to save a bit of money, check CAR's 625 appendix A for a list of elementary tasks you can do yourself. I would recomend that you get an AME to teach you how to do these things properly first, so that you don't make a mistake. If you want someone who will still provide some service to you after this thread, come out west and look me up, I will help you, but yes I may charge a bit because after all, I have a wife and a kid to feed as well.

[tiggermoth]

by the way rfc, look at the very first answer to your original questions from fixorfukit, they are right on the money.

[rfcPilot]

I may do that... I have a friend in Nanaimo I've been wanting to go see. As for the feedings, thats why I ditched the ladyfriend. The plane was more important

[Hedley]

During the compression test, you can figure out exactly where the leak is.

If it's going past the rings, you can feel the air blowing out the crankcase vent.

If it's going past the exhaust valve, you can hear it coming out the exhaust pipe.

If the exhaust valve is sticking, it's usually lead salts, which can be removed by performing the "rope trick" and reaming the guide out - no need to remove the jug.

[rfcPilot]

My AME suggested a stuck exhaust valve. Or worst, which would involve taking the cylinder off and sending it (and the works of it) for repair. The previous owner did say he thinks it was just that the rings on the piston all aligned and allowed some leakage.

Thanks for the tips on that though Hedley. Curious, where exactly is the crankcase vent, and what is the "rope trick"?

Cheers,

[Hedley]

The precise location of the crankcase blow-by vent will vary with each airframe, but they are generally an aluminum tube pointing out the bottom of your cowl opening, where the air exits below and behind the engine, just ahead of the firewall.

I'm a bit surprised that your AME didn't quickly track down the source of the leak when you did the last compression test - it only takes a minute to verify if it is rings or exhaust (rarely intake).

The rope trick is well-documented via a service instruction from Lycoming, where every 400 hours to avoid exhaust valve sticking, you insert a length of poly rope into the cylinder thru the spark plug hole.

This allows you to rotate the prop, compress the rope, and remove the exhaust valve retainer and keepers. The rope is removed, and the exhaust valve is dropped into the cylinder with mechanical fingers holding it through the port.

You ream the valve guide out, put the valve back in, feed the poly rope into the cylinder again, rotate the prop, and put the valve retainer back on, and you're done.

http://www.lycoming.com/support/publica ... I1425a.pdf

Again, your AME knows all this ... that's why you hire him, right?

P.S. If it's rings, consider a pulling the jug, honing it, and installing a new set of rings. Won't cost you that much. It's possible the engine wasn't broken in properly.

Another thing that can happen is corrosion on the inside of the cylinder. This apparently can happen because of the nitriding process - you park the engine for a long time, you get nitric acid eating away (or so I was told by an engine guy).

Free advice: if you can't cheaply refurb your cylinder, buy a new Lyc cyl assembly. Don't buy one of the crap clone replacements, unless you like reading AD's.

More free advice: hours since major overhaul is almost completely irrelevant. You hurt an engine more by NOT flying it. I used to fly a twin with 5500 SMOH. I flew another aircraft (T-34 in Atlanta, GA) that was flown so hard (and always WOT) that they eventually tore the wings off it in flight, but they flew that TCM IO-550 well past TBO, and when they tore it down at 2600SFN all the parts were within SERVICE LIMITS.

Think about that for a moment.

[rfcPilot]

Yea I've read on the Lycomming website about TBO being either the hour usage which most people refer to, or 12 years (I think it was 12). Which would put my engine in that category as it was last overhauled in 1993. And actually, when it was overhauled, it was at about 1650hrs into the engine's 2400 TBO. Since the 80s the engine has had a history of weak cylinders for number 3 especially and on occasion number 1. 2 and 4 appear to always have been in the 70s.

I have read of cooling issues with the Yankee though because of the small cowl.

I've heard of the acid stuff as well. Possibly from the engine oil itself or something. *shrugs* my plane sat doing nothing for two periods of about 4-5 years, in the 80s and again late 90s to about 2003. Average hours per year was about 150 hours from 1970 to 1980s And after that, it's about 40 hours or less, including those two periods of inactivity.

[Hedley]

my plane sat doing nothing for two periods of about 4-5 years

Ouch. Regardless of what the paper says, an engine that has sat for that long (without being properly pickled as per SI, and no one EVER does) needs to be torn down.

IMHO, a Lycoming that has sat for 2 years without running (or pickling) needs an overhaul. Of course, this length of time will vary with temperature, humidity and the amount of salt in the air. High temp, high humidity, and lots of salt is obviously worst case.

Frankly, I'm amazed that your engine runs as well as it does. I'm pretty sure that in Canada, after 1 year out of service, an internal corrosion inspection (eg pull two cylinder off one side) is legally required to detect these kinds of problems.

[rfcPilot]

Cant say I've never heard of such a rule. The engine does run fine though. I've flown club aircrafts that at times had engines that felt/sounded worst than mine at the moment, it really does sound and work fine. Then again, that'll all change if ever I get a failure ha.

My plane is going for it's annual end of summer so we'll see what comes up. Somehow... I think the list will be fairly long. hmm, transponder correlation check for instance.

[log sheet]

hmm, transponder correlation check for instance[/quote]

Now known as Intergration Test. Reference AWM 571 Appx. F if you are interested.
Cheers!