I was flying my Eagle 2 today and something happened that I'd like to know more about. This is my first year with glow engines.

Conditions:
- Wind N at 10
- 70% Humidity
- Baro - 30.02
- Temp 37 F
- Engine - OS 40 LA with about 15 or so flights on it.
- Fuel - Omega 10% Castor/Synt blend

I was about 8 minutes into the flight, when I noticed the motor rising and falling in pitch (at about half throttle). About a minute later I brought it in on a dead stick landing. I noticed that the fueld residue seemed to be blacker than normal, and it almost looked like there was some carbon residue that had made into the fuel tank compartment.

I eventualy got it running again, after some fiddlin' around. I basicaly closed the needle, and started over tuning it like the manual says for a new engine, and that seemed to get it running again. What happened? What did I do wrong?

Thanks,
Doug

Not much to go on. Are any mounting bolts loose, any bolts loose on the engine, carb. and muffler on tight? Does the needle valve seem to easily turned in or out? How long since the last time you flew? Kinks in the fuel feed or vent lines. Did you run it overly lean one time, or was the engine too lean this time?

Sounds like an air leak somewhere....hole in fuel line,loose carb? I'm guessing that if it was running way too lean because of an air leak it might cause the blacker then usual residue and I would also guess its possible for the residue to pushed from the pressure line from the muffler back to inside the tank. Makes me wonder after a flight just how crappy the left over fuel is inside my tank.....even on a good running flight.

Just watch because even if you got it running again,you might not notice an air leak until its put under the same flying conditions. I've noticed that if you notice your engine not wanting to come down to idle rpms,theres a good chance your leaking air thats makes your engine run fast(lean). And the emptier your tank gets the harder the engine has to suck for fuel and thats when the leak may show its face.....perhaps moreso during a straight up climb.

Test you engine by only putting minimal fuel in the tank and hold the nose of the plane straight up in the air at full throttle for awhile, like maybe close to 10 seconds or more,enough for the fuel thats already in the line to be used up and create that vaccum affect from the carb. Make sure your tank plug is tight and not leaking too and that the clunk lines etc. inside the tank are good.

Let us know how you make out!

black residue is a sign of metal to metal contact,a loose muffler bolt,backplate even a loose engine mount bolt will cause black residue also internal parts like piston wearing.check all screws and bolts to see if any are loose and you may want to replace the glow plug as any aluminum particles on it will cause it to burn out.

Hmmm... this doesn't look good. I pulled the fuel tank, and checked it out good. The black residue on the tank is a dust, and if the light hits it just right, it sparkles real pretty. I would be willing to bet the pretty sparkle is some kind of metal. It wasn't wet under the fuel hatch cover, just the black dust.

I noticed to that the fuel residue was blacker than normal though, usualy it's that med-dark pink, but it was definatley blacker this time. The engine is practicaly brand new. It can't have more than 15 - 20 flights on it. Oh, and I should point out that the exhaust port on the muffler had rotated on this flight, and was pointing towards the fuse. If you look at the plane/engine from the rear, it was directed at about the 7 or 8 o'clock position - instead of the ideal 4 or 5 o'clock (away from the fuse) position.

I hope it's nothing internal. If anything, I think I was running it a little too rich. I had burned out a glow plug after about 4 or 5 flights after break-in, so I thought that maybe I was running to lean. I turned it richer and have had several flights since.

If the muffler turned this is probably were the balck is coming from your getting Al. to ALl. wear that creat a very black color

its called fritting corrision..you can spot a loose rivet on a full scale because it leaves a black streak...the revving of the engine could have been caused by the loose muffler..pressure in the fuel tank fluxing because the muffler was flexing....tighten the muffler by taking off the nut in the back, loosening the screw in the front, position the muffler where you want it and tightening everything back down..

I've noticed those little metal looking sparkling things in the exhaust oil on my planes many times and never understood what it was from. The engines never seems to be affected,so I concluded that it was metal flakes coming loose from the finish on the inside of the muffler etc. And I think I was right. I dont see it near as much if at all anymore since my engines are all broke in now and have some time on them.

Also,I have an SU-31 with an evolution .61 on it and the stinkin muffler would rotate on me by the end of every flying day. I couldnt get it to stay in place no matter how many times I tried to tighten it. I eventually ended up drilling a tiny hole through the muffler where the 2 pieces join together and put a little screw through both pieces with some lock-tite on. Its never moved since!

Sounds like to me your engine is getting an air leak or bubbles in the line my Irvine 46 done the same and it was down to carburation as for the black stuff I had tones of it come out off my Irvine when it had its bearings replace all I done with my engine was wash it out after I used it and oil it up after a while it stopped but if you don’t wash the engine the little metal bits could keep wearing metal away mines had about a gallon of fuel through it before my engine really settled down

Do what jetmech says and see if it's cured. I'd bet it will be. Pressure fluctuations is the clue.

BTW, any time you run muffler pressure there will be black gunk pushed up the pressure line into the tank. Different pressure tap locations and different engines will give different amounts.

I re-did the muffle exhaust angle and tightened everything down. Seems like it helped. Tell me more about eh "black gunk pushed up the pressure line into the tank."

I think what rock means is that say for example the pressure line from your muffler back to your fuel tank comes out of the bottom of your muffler......all the gunky residue and left over un-burnt oil that could collect on the bottom of your muffler will get pushed through the line back to the fuel tank because the line is coming out the bottom of the muffler. And if that gunky,oily stuff gets to be too much it could cause blockage or at least make it harder to pressurize your tank. So although,I've never thought about it before its good to keep your pressure line toward the top of your muffler to prevent gunk from getting drawn into it. Below is a pic of the return line on my big stick which is at an ideal place. If it were coming out the bottom of my muffler,the exhaust pressure would probably push all that "gunk" that spits out the muffler when running......back into my tank through the return line.

This could likely be an issue if your engine is mounted sideways or upsidesdown moreso then if its mounted in the upright position like mine is. Or if you rotate your muffle alot.

The oil that exits the engine and into the muffler gets bounced around a lot inside the muffler when it hits the cone or baffle plate. As it migrates back and forth inside the muffler it picks up any metal particles that developed from the loose muffler halves. The muffler pressure nipple connects directly to the inside of the muffler, allowing contaminated exhaust oil to re-enter the gas tank via the tank pressure line. Funny that most never realize that they are burning a higher oil ratio in the engine the farther they get into the tank volume.