Usually when a servo is doing this there are 2 possible causes

#1 The servo is worn...meaning the pot and or the gear train are worn...The Servo is "skipping" through center then catches itself on the other side.

#2 The control surface is too much load for the servo. A rudder on a bigger 1/4 scale and larger plane has much mass and the servo because its digital is fighting for center. The reason it keeps over shooting is because the inertia of the control surface as it comes back to center...This specific servo (I'm not a futaba guy but Chad ...CAN773 is one.) but from the Info I looked up on it via the web is not designed for the application you are using. It was designed for Gyros on the tail rotors of Heli's.......This servo is so fast and so accurate in its attempt to get to center that the mass of the rudder is too much.....

And this situation if flown will lead to Problem #1 showing up as well.



As for any other servos doing it because they are digital....I would say that your setup is not correct. I have used tons of 8411's and 8411SA's as well as every other Digital Servo made by JR. The only time I get the oscillation is after many many flights when the pots and gear trains become worn.....

The metal gear trains get more slop quicker. This is a function of the alloy gears wearing on each other and with the vibration of the engine and flight loads we are putting them through....The 8411SA and the 8231's last a really long time with the all Nylon gear trains....(8411SA has a metal output gear....)


The alloy gears are designed to handle the flight loads placed on some situations.

I don't understand why you would want a gyro on the rudder of your 1/4 scale plane....In all honesty it won't help you learn to hover...In fact it will hinder it! A gyro will interfere with you learning to do that stuff.....You have to learn to use the left hand stick to do some of these things.....and a Gyro will not help you learn it. I've seen rare situations in some scale planes that a gyro actually will help.....and of course in Heli's.....

Just my opinion, I know others have theirs also......

Get a more powerful servo!

A minimum servo requirement on a 1/4 scale rudder in my mind is in the 90oz range....your servo is rated at 1/3 of that....according to the Tower ads its 27.8oz-in


This is a hand launched sailplane power level...or a 30-45 sized Heli Tail rotor...which is what it was designed around.


this is truly a shame as you could have used a JR 8411SA and saved $30 and got way more performance out of it........

My recommendations would be an 8411SA aprox $99 for a Digital 155 oz-in

or the the JR 4721....$85 and 120oz-in.....


Either servo would work superbly in your situation....

Troy Newman
Team JR