Elevon odd behavior in stabilize on a S800

Hi guys.
I`ve setup my mini apm in my Reptile S800 wing.

Gone through the elevon setup.
Servo1_function : 77
Servo2_function: 78

In flightmode Normal and stabilize the elevons moves in the right directions on stick input.
But when I switch to stabilize and hold my wing this happens:

Pitch nose down - The RIGHT elevon moves up, and the LEFT elevon stays still.
Pitch nose up - The RIGHT elevon moves down, and the LEFT elevon stays still.
Tilt wing RIGHT - The LEFT elevon moves up, and the RIGHT elevon stays still.
Tilt wing LEFT - The LEFT elevon moves down, and the RIGHT elevon stays still.

So… Is this normal? - The elevon that moves, moves the right direction, but only one of them.
It seems to me that the RIGHT elevon controls the pitch and the LEFT elevon controls the level.

Seems legit?

On my Mini Talon both elevons is moving when trying.

Have I done something wrong :stuck_out_tongue:

it is not normal , use SERVOx_REVERSED to correct elevon behavior in FBWA

I dont see how this will help?
Are you sure you understand the problem?

The SERVO_X reversed are correct :slight_smile:
But only one of them.

On roll one servo is adjusting.
On pitch the other servo is adjusting.

And they go the right way But the opposite servo stays still.

No, probably I’m an idiot answering to your help request just to waste my time.

Wow! Really?
It was an honest question… not negative from my side…

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Make sure you actually apply those parameters – it sounds like your are not actually changing your servo function to 77/78. The activity you describe is consistent with ailerons and elevators - not elevons.

Maybe try rebooting after changing those parameters.

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But on Stick input in Normal mode and stabilized mode everything is working as it should. And the elevons is moving in correct order.

So If i didnt set the 77/78 elevons they wouldnt have worked. Or am I wrong?

I did however needed to reverse my CH2 on my taranis. Maybe this is were the fault is? If I change it back I cant get the elevons to work properly on stick input.

Maybe try following this process that I rewrote – It is waiting to be approved before the wiki is changed. Sorry for the unformatted text, but it should get you in the right direction.

Elevon planes (also known as delta-wings) are popular for their simplicity and robustness.

A typical elevon plane will have 2 servo outputs and one throttle output.

RC Input Setup & Reversal
Set up your :ref:RC inputs <rc-throw-trim> through the calibration process, and verify them for reversal. Reversals are critical to the process. Commanding pitch up and roll right must result in higher PWM values for RCn_in channnels. If the value does not respond correctly reverse the channel before continuing.

You can connect your 3 servo cables to any output of your autopilot, although using the defaults listed above is recommended.

Servo Setup & Reversal
The next step is to get the servo reversals right. You should connect the battery (with propeller removed) and turn on your RC transmitter. Now switch to FBWA mode and press the safety switch (if fitted) to enable servo outputs.

At this point both the autopilot and RC transmitter should have control of the elevons. You now should adjust the reversal and function of the two servos so that you get correct movement.

Correct FBWA (automatic stabilization)movement for an elevon plane WITHOUT PROVIDING RC INPUT is:

Input - Action
Roll right - Left elevon goes up and right elevon goes down
Roll left - Right elevon goes up and left elevon goes down
Pitch down - Both elevons go up
Pitch up - Both elevons go down
If your movements are incorrect then you need to adjust which servo output is left/right and the reversals of each elevon.

The parameters you should adjust are SERVO1_REVERSED, SERVO2_REVERSED, SERVO1_FUNCTION and SERVO2_FUNCTION.

If your left elevon on servo 1 is moving the wrong way for both pitch and roll corrections, set SERVO1_REVERSED to 1.

If your left elevon on servo 1 responds correctly to pitch, but incorrectly to roll, change the SERVO1_FUNCTION.

Repeat the servo reversal or function change for the right elevon.


In rare instances, both servo 1 and 2 will indivicually respond correctly with the same FUNCTION. This is OK.


while rolling the aircraft the autopilot will automatically try to put in some up pitch, as it knows that upward pitch is needed in turns. So you will probably see an asymmetry in elevon movement. The elevon that is going down will not go down very far, or (depending on your settings) may not go down at all.

Verify RC Inputs
Now that the elevons are configured correctly, verify your RC inputs. In FBWA with the airplane level, command pitch-up from your transmitter and confirm that the elevons both rise. Command a roll to the right from your transmitter and confirm that the the right elevon rises and the left elevon lowers. If this is incorrect, read the :ref:RC inputs <rc-throw-trim> page to fix your rc

Switch the plane to MANUAL mode and confirm the same behavior.

Servo Trim
Now stay in MANUAL mode in order to adjust the servo trim values. The servo trim is in the SERVOn_TRIM parameters.

You should adjust the trim values so that the servo is centered when your transmitter sticks are centered. If you find you need to adjust the trim value by more than 50 PWM from the default of 1500 then it is recommended that you instead adjust the trim mechanically.

Servo Throw
Finally you should adjust your servo throw. The throw is the range of movement for each of your servos.

Check any instructions that came with your plane for suggested throw values. These are often specified in millimeters or inches of movement of the edge of the control surface. If your aircraft doesn’t come with any suggested throw values then choose a throw that doesn’t cause your servos to “bind” (which is indicated by a high pitched sound when your servos move too far).

To adjust the throw, change the SERVOn_MIN and SERVOn_MAX values. The defaults are 1100 to 1900. On many aircraft you will want more throw than that, and can change to a throw of 1000 to 2000.

Mixing Gain
The MIXING_GAIN parameter is critical for elevon aircraft. It is the gain used in mixing between roll and pitch output and your elevon movement.

For example, if your MIXING_GAIN is 0.5, then the following outputs are used:

LEFT_ELEVON = (roll+pitch)*0.5
RIGHT_ELEVON = (roll-pitch)*0.5
By adjusting the MIXING_GAIN you can quickly setup the right throws of your elevon aircraft.

Final Setup
After completing the above you should move onto the final setup of your aircraft.

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That’s a great write up Nate, but probably going to confuse in this particular case, as the OP is using an APM, which means ancient code and parameters that don’t match current ones.

Oh crap.

Yeah I didn’t realize that. What version of plane are you running @Jan_Ivar_Haugen?

Its working now, I reset the board, and did it from the beginning following your guide.

Btw: Im using Arduplane 3.8.4.

Again thank you so much :slight_smile:

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The new guide is live: http://ardupilot.org/plane/docs/guide-elevon-plane.html#guide-elevon-plane

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