History: Pau 120cc MXS Viper. GP 123, Falcon 28x9W, JR XG-14 radio, RG1131BPU receiver, Tech Aero HV IBEC, TailDragger RC 20 awg extensions, JR-S8911 (stock programming) servos on all surfaces, Hitec D930SW on throttle. 100LL mixed Redline 40:1

Maiden 07-18-2018 plane gets flown every week 3 to 4 fifteen minute flights at least 325 flights on the plane with not a single issue.
Problem: Two weeks ago on second flight pre check noticed jitters on rudder and a elevator and lack of smooth movement moving sticks slowly. I grounded the plane and started repairs.
I noted some gear wear and a little slop. So I replaced the servo with a new servo I had no improvement. I replaced the Dubro 3mm ball links, no improvement. I tried two more new servos and a used servo same issue. I cut the Robart hinges off and new Robart hinges installed no improvement. I replaced the servo arm, no improvement. I the started with my JR programmer changing the deadband, holding, dumping settings on all four servos and no changes. I then started by plugging rudder servo direct into a RG1131B receiver powered by a Fromeco Badger switch and a separate 2S lipo and bound it to my back up JR XG-14.
Same issue is still plaguing me.
The rudder swings smoothly before and after the new hinges. The only thing I have not changed is the brand of oil I use or my own thumbs. Any ideas will help.
Thanks

Servo jitter issues (0 min 37 sec)

You get the same effect without the flying surfaces hooked up to the servo?

I didnt see your rudder jitter, and thats the puzzling part to me... Because if/when a servo jitters, its typically translated to the flying surface.

Could the transmitter's stick pots be starting to wear near center?

Originally Posted by Bunky F. Knuckle

You get the same effect without the flying surfaces hooked up to the servo?

I didnt see your rudder jitter, and thats the puzzling part to me... Because if/when a servo jitters, its typically translated to the flying surface.

I filmed from the side, but turn up the sound you can hear it and look close rudder vibrate like paint shaker.

Originally Posted by RCAddiction

Could the transmitter's stick pots be starting to wear near center?

I had that thought but I tested with two radio and the back up only has maybe two hours of use.

So if I have this correct, you swapped servos, tried a different receiver and transmitter along with plugging directly to a different receiver. If that's correct is it possible you have a broken joint in the airframe? No other issues with other planes?

I rehinged the rudder, I am going to check the fuselage closer. Other airplanes are good.

Festivus, check your extensions and check your other servos. Unplug them all to see if it stops. Sounds weird but I once had a servo that was causing the other servos in the plane to buzz and act erratically. I unplugged one thing at a time until I found the culprit. It was not the buzzing servos that were causing the issue in my case.


Nevermind...I just noticed that you had the problem with the rudder servo connected alone. Did you try running a different servo extension to that rudder, or maybe changing the assigned channel to a different port for the rudder?

UPDATE: 10-08-2020
I moved the rudder servo to the opposite side of the fuselage. Checked all hardware, its all new.

I even used a third receiver and both radios still have the same issue.
I plugged the servo directly into the receivers no extensions used.
I put the servo on all channels, throttle, elevator, aileron, rudder etc.

Same issue.
I have inspected, pushed, pulled and twisted the fuselage, I cannot find a crack or broken glue joint.
I guess the next step is too remove the covering from the tail section and inspect, maybe see something hidden by covering.

Try setting the Holding to 20 and Dumping to 10. Everything else stock settings. Test. Continue to increase each of the above values by 5 points per test.

Festivus, this has gotta be so frustrating. You're checking all the logical things and even some that aren't (grin).

Is there anyone at your field that flies a different brand than JR? If you could plug the servo into a another brand radio/RX or even a servo tester to see if it still oscillates...maybe something with the servo is feeding back and causing some interaction with which JR is sensitive.


Where are you testing it? From post #1, it sounds like you initially found the problem at the field and are perhaps now testing in your home shop? Could you take it outside away from the house with the radio far from the plane and have someone hold the radio while you inspect the plane?

Originally Posted by emack203

Try setting the Holding to 20 and Dumping to 10. Everything else stock settings. Test. Continue to increase each of the above values by 5 points per test.

I have done many programming changes including the dead band. I just tested my 43% edge and zero issues, I believe its some how air frame related.
I may just have to test fly it until I find the failure point.

Originally Posted by RCAddiction

Festivus, this has gotta be so frustrating. You're checking all the logical things and even some that aren't (grin).

Is there anyone at your field that flies a different brand than JR? If you could plug the servo into a another brand radio/RX or even a servo tester to see if it still oscillates...maybe something with the servo is feeding back and causing some interaction with which JR is sensitive.


Where are you testing it? From post #1, it sounds like you initially found the problem at the field and are perhaps now testing in your home shop? Could you take it outside away from the house with the radio far from the plane and have someone hold the radio while you inspect the plane?

RCAddiction frustrating is an under statement. I have seven brand new servos sitting on the bench to go into a new Skywing ARS-300, all of them have had a turn in the plane. I am going to try a cheaper servo just to check and eliminate everything.

I just realized I never tested with the tail wheel disconnected. Just did the test and still have the problem. I just also used a new Hitec D930SW and a new Promodeler DS-140DLHV the last two servos are purchased for throttle use.

Is there a chance this is a noise issue? If you have another ignition try that, or pull the plug wires and clean them and then reconnect and see what happens.