SM F15 elevator servo chatter
 

I am using 8611 per elevator half and each time I power the system ON, they chatter like hell. I know digitals chatter all the time, but this is ridiculous. If I place my hand under the elevator surfaces, kind of suporting them on its center, the chattering stops. Do the elevators need balancing???? are they are heavier on one side of its pivot point?? There is no binding at all anywhere during the entire travel. Just chatters in its resting position.

RE: SM F15 elevator servo chatter
 

Anurag,
This may indicate that there is some slop in your linkages or hinges. I have had this happen with digitals also and this was the cause. The servo is trying to take up slop but overshoots due to the slop, and then reverses to do the same again, and is trapped in this loop. I guess the servo is sensing a varible load. I my case there was some slight slop in the hinges, and when this was removed, the problem was gone.
Regards,

John

RE: SM F15 elevator servo chatter
 

Be sure to check this outside and with the antenna fully extended. I had similar experiences with a plane, when I was in my shop and was programming the radio. There was some jitter that I thought was strange, but when I got outside with the plane and switched the radio on,-- it was all gone.

Of corse, you also need to be sure that there is zero slop in the linkage too.

My 2 cents

RE: SM F15 elevator servo chatter
 

Hi there!
Here are some advice I have picked up by reading this Forum:

- Some servos are very sensitive to operate with a Y-harness with the the problems you describe. However, since you are using them as elevons they must be plugged in to separate channels of your Rx so this can't be the problem.

- Make sure you are using the full travel of the servo to obtain the recommended throw of the control surface. By moving the link one step in to the center of the servo you may reduce the problems you have (because you are reducing the speed and acceleration of the control surface).

- If you currently are running on 5-cell Rx batteries you could try with a 4-cell pack. This will reduce the speed slightly of the servo and probably reduce the occilaton.

- If you have a Tx where you can adjust the servo speed you should have a go at it. Reduce the speed step by step and se what happens. I think there is a good chance it will solve the problem. In my oppinion you don't really need a quick servo for a Jet-model that is supposed to fly smooth and gentle.

- Yes, mass balancing will help and you don't necessary have to get 100% static balance. Take some large coins and attach them temporarely with tape close to the leading edge close to the fuse of the elevons. I'll bet it will reduce the occilation or eliminate it completely.

- Very true you have to get rid of all potential slope in the linkages.

Good luck /Johan

RE: SM F15 elevator servo chatter
 

Anurag,

All of above are very good suggestions to check. The Skymaster F-15 elevator don't require balance. I believe already have hundreds F-15 flight as not balance and no the issue as you describe. The problem you have is not normal, you should check it before fly.