HI I'M HAVING PROBLEMS WITH MY SU-31. I HAVE A FUJI 43CC IN MINE WITH ALL SERVOS IN TAIL (3305) AND THE HYDROMAX 3600MAH FOR RECIEVER PACK, WAS A LITTLE TAIL HEAVY BUT FLEW ANYWAY. FIRST FLIGHT WENT OK KNOWING AIRCRAFT WAS TAIL HEAVY. I TOOK HOME, REBALANCED, MOVED BATTERY FORWARD AND ADDED 8OZ TO FIREWALL NOW THE PLOBLEMS!!!!!!!!! TOOK TO FIELD AND HAD ALL KIND OF RADIO INTERFERENCE IM USING AN OLDER FUTABA 8U WITH PCM RECIEVER NEVER HAD HAD PROBLEMS IN PAST BUT DOING READING ON HERE THERE IS A PROB WITH ELEC IGNITION WILL GOING TO 2.4 HELP OR DO I HAVE OTHER ISSUES. WHAT I DON'T UNDERSTAND IS WHY I DID NOT HAVE PROBLEMS FROM GET GO. PLEASE HELP.

did u try putting the battery back where it was and recheck it ??? mabe when u rerouted the wires that caused it ..im only guessing though..not familiar w/ the gas/pcm stuff... YET

Basic radio installation 101:

When using a gasoline engine with an ignition system that fires thousands of volts to a spark plug.........................................

Keep all your RX stuff at least 12" away from the ignition (magneto), ignition switch and ignition battery if using electronic ignition.

That means you keep your RX battery, servos, RX, switch and everything else related to the receiver at least 12" away from that engine/ignition/sparkplug/switch.


Dump the PCM RX and get an FM PPM RX for the initial range checks. When you get it all sorted out and you have no more glitches using the PPM RX, THEN you switch back to the PCM RX.

PCM will hide glitches and RF problems. Hiding a problem like that will bite you in the butt one of these days. Use the PPM RX to "prove" your installation because it won't hide anything. If you have a problem, it will show up during range checks with the PPM RX. Once you get it all sorted out you can switch back to PCM if you want.

Of course, I'm probably a total idiot and somebody MUCH smarter than me will come on here and tell you it's the metal clevis on the elevator pushrod.

OK I HAVE A R168DF RECIEVER THAT I TRIED MOVED THE BATTERY BACK TO OLD LOCATION APPROX 14" AWAY FROM IGNITION AND ALL KINDS OFF PROBLEMS (I HAVE NO CONTROL OVER ANY CONTROL SURFACE) WHEN I GET 5 FT FROM AIRPLANE NO IDEA WHAT TO DO!!!!!!

There are a million threads re interference in RCU, and a million different opions. Just keep to the basics. Move the Rx as far away as possible from the CDI/ Magneto. Use 2 battery packs (no Y leads to one battery) - one for the Rx and the other for the CDI if you have one. No metal to metal to the throttle. Resistor spark plugs and good grounding from the CDI to engine or magneto. Make sure the servo extension leads are firmy plugged in etc etc.
2.4 is good, but it will NOT prevent CDI / magneto interference, it will only mask it. You will still need to follow all the basic rules when using Gas.

I've seen this problem before! solved it with dielectric grease beneath the spark plug boot. hope it works for you!