APM 2.6, Tricopter 2.6HV (700size) tail servo settings


I was wondering how to set the basics for the tail servo?
I’ve not flown the tri yet, but by testing it in my hands, it seems that the tail rotor servo is reversed in the compensation, but from the rudder control on the TX it seems correct?

And the basic angle of the servo, how can I set it?
I’d like it positioned differently at arming, to avoid rotation of the tri during the phase from ground to hover.

Maybe it is a part of the auto tuning, but I have not come to that part yet.

Depending upon what tail servo you use and just how the mechanism is constructed you may or may not have to do one or two reversals. The first, and obvious one, is to check your RC Tx. Sounds like you already have checked this. But the other potential reversal is to tell the APM to reverse its own control of the servo.

I usually test if this is needed by bringing the tricopter to just barely a hover so that’s it’s just floating on the ground. If it starts to rotate I know the APM control needs to be reversed. This is done by going into the Full Parameter List (under Config/Tuning) in Mission Planner and setting the variable RC7_REV equal to -1. This reverses your Yaw servo channel from the APM’s viewpoint.

I don’t believe there’s any way to set the angle of the tail servo in the APM. It’s usually not necessary as the APM provides the angle needed to do what is being requested of it. There are some programmable servos (Hitech comes to mind) where you can set the servo center and ends point if you wish.

There shouldn’t be any rotation as the tricopter lifts off if the control reversals are correct. It’s perfectly smooth.

Thank you for the reply!

I took the Tri for a spin on my living room floor, and as soon as it has enough power, it tilts the servo fully over, and spins in a circle.

So I tried to do as you say, to switch RC7_REV from 1 to -1, but the software autocorrects it to 255, any idea why it does that? Bug?

Here is a video of the behavior, I only touch the throttle stick.



Anyone know why the software autocorrects my “RC7_rev -1” input to 255 when i press write to controller?

This always causes grief!

This is the proper way to think of the Tricopter Yaw…

Set the tricopter in front of you, with the tail towards you. Turn the Tx on, then the aircraft.

Push the rudder (yaw) stick to the right. The rear motor should tilt to the left, which when flying will swing the nose to the right. Push the stick to the left, and the motor should tilt to the right, which will swing the nose to the left. If this is OK then the inputs are OK.

Now hold the model (props removed!) and swing the tail sharply to the right - the flight controller should swing the rear motor to the left to correct the error. Swing it to the left - the rear motor should go the the right. If it doesn’t you will need to reverse the gyro.

Hope that helps!