Gentleman - I recently acquired a Hangar 9 P47 150, never flown, with a Fuji 32 EI Gas engine, run once. Whenever the engine is running, one of the two Flap servos moves, randomly, up and down, slightly. The servo on the other Flap does not jitter. I am using an HD reversing Y harness. I put in a new Y harness and switched from JR 537 analog servos to DS811 digital servos. The same Flap jitters. The servo leads go directly from the wing to the Y to the JR 649 receiver. I am using a JR9303 on PCM. I switched from a 6 volt battery to a 4.8 volt battery. No change. I moved the receiver and servo extentions around. No change. It does not happen when the engine is off. There are 10 servos in the plane. Each Aileron has it's own servo on different channels. The same with the Elevators and the Mechanical Retract serovs (S791).

Is it possible that the ignition could be glitching just one servo on a particular channel?

I am waiting for the rain to stop so I can put the plane together and try some other things. I have flown the plane 4 times. The engine runs great and starts easy. No problem with range, with or without the engine running. I first noticed the Flap moving on the second flight, but I thought the Transmitter was swamping the receiver. Not a hint of irregularity while flying, but since I put in the DS811 servos, the Flap deflection is just a little too much.

Any ideas on how to Diagnose this problem?

Busch,
Take the plane to the field when other gas guys are there. Have one of them runup their engine with your radio on and see if the problem accures. If it does, it is in your rx/tx system. If not, It is something generated by your ignition.

Dave

I just got an email from someone who had a similiar experienc. They felt that the Reversing Y was picking up some RF and that is why it only affected one side of the Y. The Y is not marked as to which is the Reversed lead, but I can connect each flap servo, one at a time, to the Receiver, and see which side is reversed and whether the Y is part of the problem.

It rained all day today, so I could not put the plane together and test it.

those reversing Ys are --not a good idea

Also, What type of throttle rod are you using? If you are using a metal rod, you may be picking up interference from that. The rod will carry signal from engine to the radio and will cause that same problem with the control surfaces flapping.

Jamie

The throttle rod is a plastic nyrod. I will try reversing one of the flap servos and using a regular Y or switching to a matchbox

Really just throwing a dart in the dark here, but did you try putting a different control surface on that channel just for kicks?

I replaced the reversing Y with a JR Matchbox. It took me a while to get the one Flap servo to reverse. I have never used a Matchbox before, but I could only get the servo reverse by setting the Flap switch to the Mid Flap position. The manual calls for the Transmitter stick to be at Neutral, when you press the button on the Matchbox to reverse the servo. I called Horizon, but they did not say anything about having the stick at Neutral. I tried pressing the button at full up flaps and nothing happened. I just happened to try it at Half Flap and it worked

I agree that as a test, I need to try plugging the affected flap servo directly into the receiver. That would help determine if the Y was involved in the problem.