This is what I was doing. I have an OS 46AX that has never been run. It was purchased to go on a Spacewalker2 that is giving me all sorts of problems (that will be another post sometime). What I wanted to do is install the AX on my Ultra Stick 40, that right now has a OS 46FX on it. No problem, right? Well after I install the AX the plane goes nuts. It will not pass a radio check at all! I have not had any problems with the plane or the FX.

What are some options for correcting this? Right now the throttle pushrod connects to the engine with a Z bend. I thought there maybe some metal to metal contact, but the throttle arm on the AX is plastic.

BTW when I say interference, I mean the radio sitting on the ground right beside the plane, both turned on. I am not even touching the radio and the control surfaces are randomly going up and down, etc. I walk away from the plane with the radio in hand, not touching the control sticks and same thing, the plane acting like it is possessed.

Take the engine completely out and see if you still have interference? If you have only replaced the engine and not disturbed anything else and the throtle pushrod isn't touching metal I find it hard to believe that it has anything to do with changing out engines

After spending 30 mins trying to figure out where the interference was coming from, I put the trusty 46FX back in, did a ground check and radio check, then flew it the rest of the day. The only thing that changed was the engine. That is why I am scratching my head.

Also, before someone asks why I was doing this, I wanted to break in the 46AX and leave it on the Ultra Stick. The fuel line is easier to access on the AX than it is on the FX, plus then I could put the FX on the Spacewalker2. The Spacewalker has a cowling, so I installed a fuel dot for refueling.

Nebbie

You got me on that one I can't think of one reason why an AX would cause interference and the FX won't. You sure you didn't reroute things when installing the AX???

I don't believe that I rerouted anything, except maybe the fuel lines. I did the engine swapout at the field. I had one of the oldtimers looking at it also, and he said it must be metal to metal contact somewhere, but neither of us could see any.

<shameless bump>

Mike,
I had a devil of a time trying to figure out interference with one plane that only ocurred between about 1/2 and 2/3rd's throttle. It turned out to be a metal cable that I had for throttle control, and yes I had a plastic arm on the carb, as well as a plastic clevis at the servo.

Once I replaced the metal cable the problem went away.
Dennis-