I asked this question in the Questions forum but received no response. Thought I'd try here. I noticed something on my Sig Fazer ( OS .52 4 stroke) that I'd never seen before. I think I have a problem but I'm not sure. I was having some idling issues and finally got it adjusted right. I was running the engine on my bench and I noticed that when I got to about 50% throttle, my control surfaces started twitching back and forth. Looking at the servos, both aileron and throttle, I could see the servo arms moving back and forth, just a little, maybe an eighth inch total.. I could see the throttle rod moving back and forth with a slight increase and decrease in RPM. So the ailerons and rudder is twitching back and forth just a little. I didnt see the elevator as it was disconnected. I thought maybe I was getting a little interference from my thottle arm connection but on the .52, the throttle arm is plastic. My servos are Futaba 3004s and I had a fully charged TX/RX. I wondering if this is a vibration that shows up when its on the bench but disappears in the air. Maybe its always been this way, I just don't know. Up until this idling problem, the plane has always flown very well. I may hook up another receiver and see what happens but I wanted you flk's opinion first. As always, thanks in advance

i've ran into that problem before, i just changed recievers and it cleared up, same model reciever, same wiring routes. haven't got around to sending the reciever in to be checked out yet. if you think it's something bench related, you might try holding the model in your hands and letting someone else work the xmitter, or vice versa. also you might conside range checking the model again (might not be the problem, but it never hurts)

keep us informed
Kevin

first question is your tx. antenna fully extended if not you can get some cross over interference . make sure your reciever antenna is routed outside your plane and that it passes radio check with the tx. antenna down at 30 paces away you might need some help with that the engine doesn't have to be running if its O.K then check it with the motor running . thats a start alot of times when my tx. antenna is collapsed I notice some twitching as soon as I extend the antenna it goes away and will fly fine .try it and see.

ClarkFlyer,
There are a few different things that could be causing your problem. The first thing to try though is to look at the receiver. Since you've already said you are going to try swapping that out, let's see what happens there. My guess is that's where your problem is. The vibration of your engine is what's causing the problems in your receiver resulting in uncommanded servo movement. A new receiver should take care of it.

This brings up a great point though. This is why all range checks should be done with your engine running. Just checking it without the engine running won't show any problems caused by vibration.

Hope this helps

Ken

I think what I'll do next is to take the rx out of the plane and just lay it on the bench while I run the engine up...might help me isolate the problem. The point is well taken about checking the radio equipment with the engine running wide open......when I have my throttle below 50%, everything looks fine. Thanks Guys!!

Is the receiver wrapped in foam?
This could have also been your idleing problem? If the receiver is sending erratic commands, your throttle servo could have been glitching also--giving your idle problems. Then again, you said it only showed up at high throttle, so never mind that.
I definitely wouldn't write it off as just a bench problem. Get it fixed before you fly it, or it will cost you the airplane. You could have a damaged crystal that only shows up during times of high vibration!
Is your crystal taped in?
I agree that your receiver antenna should be fully extended and routed properly. However, with no other radios present, your radio should not be glitching with your TX antenna collapsed. This is the basis for all of our radio checks. Do not raise your TX antenna and assume that the problem is fixed. You should not have glitching either way. The only glitching I've ever seen with my antenna down was at the field when another pilot had his TX on. standing right next to me, with his antenna fully extended. I was getting glitching.
I assume that your batteries are charged? (both TX and RX)

Ok...the plot thickens.....I removed the rx from the wing and let it hang free in the air......started it up and everything was fine. I had the rx wrapped in foam and now am wondering if it was packed too tight. Now I seem to have a new problem....I can't seem to adjust the high end to run smoothly. Acts just like an air leak. I tightened all screws on the engine, which were tight, changed the plug, changed the carb fuel line. I'm seeing no bubbles in the line but maybe I'd better tear apart the tank and check those lines.....Geeeez, this plane has always run and flown well and now its kind of falling apart..........Hmmmmmm, could this be a sign that the valves need adjusting? hey, any and all opinions welcomed!