AP 09 Hornet in my Schoolboy ARF dieing mid-flight. Need help !

The overheating would be my first suspicion, If you have had help with the needle setting and you are convinced that is not the problem, the next thing I would suspect is a problem with the fuel pick up line in the tank. If there is a hole in it that is exposed when the fuel level drops below where the hole is, then it would suck air instead of fuel, go lean, and quit. Check or replace the fuel pick up to rule this out.

Regards Ed

funny wrote:

I have an AP 09 and it runs great. You possibly coule have to large or small a prop. To large will make it overheat and die. I can't remember what size I have on mine. Boy that helps doesn't it?? If I can remember when I get home I'll look and see. Eddie Fulmer

Your setting is too lean. Fill your tank 1/3 to 1/2 and adjust the needle for dependable running. Then turn it off, fill the tank, start the engine and fly it.

I run a 7x4 prop.

What you got on yours? Strange thins is that if i run the plane on the ground - it seems to run without any problems. Thats why i thought i was either needle problem, or tank elevation.

Can you give me settings for your engine? how much needle is turned and what fuel are you running.

Thanks Yuki

Thats the thing - it seems to run fine while on the ground, but in the air - it will die mid flight.

Whats the procedure for figuring out if its too lean or rich ? Sorry, im a newbie- so have to ask all these silly questions.

Thanks Yuki

engines lean out as RPM rises.

Its too rich if it burbles at full throttle. Open up the main needle on the ground till it is *just* burbling and then lean off ONLY enough to stop the burbling, not enough to get peak RPM.

If it still cuts, get someone at the club to check the installation.

It has been run in I suppose?

Burbles meaning ...?

Ill try your suggestion. Yes, we went through the brake-in procedure as instructed. People looked at it and said its all installed well, but the engine dies - so i know there is something wrong.

Has anyone taught you the nose-up test?

Adjust the engine to maximum RPMs by ear. At full throttle, have a helper lift the plane and point the nose straight up into the air. Listen to the engine as he/she does this.

If the engine speeds up signifigantly, you're running a bit rich. Put the plane down, close the needle valve a little, and try again.

If the engine sags or slows down, you're a bit too lean. Put the plane down, open the needle valve a little, and try again.

You're trying to adjust the engine so that the RPMs increase SLIGHTLY when you point the nose up in the air.

It should be, "Hmm, it's hot... This is uncomfortable... Maybe I should let go now," hot. Too hot is, "JEEZ! I can't even touch it, it's so hot," hot. If it sizzles when you touch it, it's too hot. If you have cooling fin lines branded on your fingertip after touching it, it's too hot.

Yes. If you're getting a few air bubbles on the ground, you're getting LOTS of air bubbles in the air. This is bad. The air is displacing fuel. When the engine is starved of fuel, it goes lean, gets hot, and quits.

One mystery solved. We know why it's quitting on you. The other mystery is to find exactly WHERE the leak is.

Im going to try your test today.

I ran the engine to see how hot it gets and while on the ground it gets VERY hot. Which may not be the case in the air as air there will be colder and will be moving away from the engine faster