Hi,
I have been flying for about two years, but have never really had to do much troubleshooting on my motor.

I recently put my os .46AX in a new Phoenix Extra Arf, and it has been acting up. It is mounted on its side, previously mounted upright, and the gas tank has is pretty much at the same level as the carb. I can get it run great on the ground, do the point up test, and all...but when I start flying and doing axle rolls it will Drop RPMS. If I don't stop my tricks it will go dead stick. If I stay inverted too long it will also go deadstick.

What to do? Where to begin?

Thanks in advance!
~Tip

Have you checked your fuel tank? Check to make sure that the fuel pickup line can move freely in the tank. When you turn the tank upside down the fuel clunk should fall to the bottom of the tank. If you are properly tuning your motor so that does run strong when you hold the plane with the nose pointing up, then there's a great chance that the problem is in your fuel tank. Check the pickup line.

Hope this helps

Ken

Sounds like tank problem. Sometimes the clunk gets stuck in the front of the tank in a "U" turn. When the tank is full, it will run fine even when pointed straight up. If you can get to the tank easily, do a visual inspection. If not, fill the tank only about 1/3 full. Start the engine and hold the plane in various attitudes (nose up, horizontal left side, horizontal right side, horizontal upside down. The engine should run the same in all positions. The only time it should quit is when you point it staight down. Also, as you are doing this, watch for bubbles in the feul line going to the carb.

Most glow engines, once started, will run the same in all attitudes.. Even if the needle valve is too rich or too lean, it will not change the engine by being upside down. That is why I suspect a tank problem.

Is the clunk sticking to the back of the tank because of a slighlty long hose? It could also be stuck to the front of the tank from a hard landing or storage as well.

Also check on the ground to see if there are any bubbles running through the lines due to vibrations or air leaks. It really sounds like a fuel problem, not an engine problem to me.

Check the clunk for clogs or debris in the tank and make sure the tank is not moving inside the fuse.

Good Luck!

WOW, you guys are FAST!!

empty the tank and hold the plane vertical and shake. Do you hear the clunk banging around inside? If not inspect the tank more closely to see that the clunk is not jammed anywhere in the tank

Sounds like I need to start with the clunk and go from there. Any tips on the best way to check for leaks, pin holes, in the tubes besides a visual inspection?

Thanks for the quick reply's!
~Tip

With the tank almost empty, run the engine and hold the plane straight up. Watch the fuel line for bubbles in the fuel. This indicates a hole or air leak somewhere between the clunk and the carb. Often there is a leak in the tubing inside the tank -- where the silicone tube attaches to the brass tube inside the tank. This type of leak does not cause a problem until the tank is less than full.

It could also be a worn O-ring on the NV.

NV?

...Good tip on how to diagnose the air leak. I will plan on spending some quality time with my plane this weekend. I was hoping there was somthing I could do on my bench, after hours.

needle valve