TakeOff Command direction with Believer

I hand launch my Believer by putting it in TakeOff mode, shaking it to spool up the motors and then throwing it. This is working well however the direction the plane takes off in isn’t straight ahead where I’m pointing it. Instead it always takes off about 30-35 degrees to my right. It hasn’t caused me any issues but it does make it cross the flight line which can cause quite a drama at some air fields. It might also be a problem if I have to launch with trees in that direction. Is there anything I can do to make the plane launch straight ahead?

The most recent flight log is located here.

Your plane looks like it’s flying really well, so I don’t have much to offer. And Take-off mode seems to be a hot topic right now so maybe others will offer insight.

TKOFF_LVL_ALT is commanding wings level until 30m. So it may come down to how the plane is being thrown. It looks to me like right after the throw the plane rolls to 60, but the controller is demanding level wings. Might come down the flick of the wrist. So what ever direction the plane is at once with wings level out is where it’s going, until it’s 30m up. TKOFF_LVL_PITCH is trying to hold the plane to 30 degrees nose up and the plane never really get’s there. Closest it gets is 25 degrees just before it reaches the 30m altitude. Maybe, (and it’s a long shot) try TKOFF_LVL_PITCH at 25 or even 20. My hope is that will let the plane accelerate faster, giving the controls more authority, and possibly minimizing the directional error.

Edit: Sorry, I had it in my mind the Believer was a wing, not a v-tail. I’ll leave my comments here for debate fodder, but I may re-think answer on this. Now I’m more curious about why it had the roll after the throw.

Thanks. It might come down to just how I’m throwing it. I had a look at a recent video of me launching it and the direction wasn’t that bad. See 37 seconds in this video of hand launching the Believer. But most of the launches I’ve done so far it would fly so far right as to go outside the frame of that video.

I notice some people recommend using the TakeOff command in an Auto mission with one waypoint to improve the direction. I’ll give that a try as well.

I noticed some differences between takeoff mode and TakeOff item in a mission.

also talked about in this thread is poor heading hold on takeoff. My solution is create two missions for any given flight field, one for each takeoff direction. pick appropriate mission on the day based on wind direction.

make Takeoff altitude very low, like 5m. then make the next waypoint 50m high and a couple of hundred m away. it will takeoff, climb to 5m, then correct it’s heading and climb to the next waypoint.

I hope Adrupilot adopts improvements to heading hold during takeoff, but until then, this method works well for me.

Oh @dale2020,
I thought it really did not matter where you placed the first waypoint in the mission, it only holds the takeoff parameters but the direction it will try to hold is set wherever the plane was pointing at the moment of entering Auto mode.

I have not tried this yet on my wings since I always find it scary to have a WP just placed anywhere. not sure if I understand the Wiki correctly. Maybe its more to it?

Note that the takeoff direction is set from the direction the plane is pointing when the automatic takeoff command is started. So you need to point the plane in the right direction, then switch to AUTO mode.

Just for clarity of anyone new jumping into this auto-take off discussion: that’s only for auto take-off in a mission. Don’t do that in Take-off MODE or you could end up with a plane entering a loitering at 5m. Unless you’re into that kind of excitement. From the wiki: “It will then loiter, as in LOITER mode, at TKOFF_ALT altitude until the mode is changed.”


thank you @Allister - I completely agree. another fun fact - if you set this one to 0, thinking it will takeoff then come back and circle overhead, you’d be wrong. not going to name names here, but “someone” thought it would be a good idea to set this to 0 and learned the hard way that it leaves the ground and immediately begins circling up to altitude, doing it’s best to find trees on it’s way.

“TKOFF_DIST” (0m - 500m) This is the distance from the takeoff location where the plane will loiter. The loiter point will be in the direction of takeoff (the direction the plane is facing when the motor starts)

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Wow, I can only imagine the colourful language that also would have been flying at that point.

That might be a good update for the wiki to change that minimum distance.

Hi Allister,
Hands toss take off does not fly straight. Can you tell me how to fix it?

Clarify what you mean by not flying straight? I’ll make some guess here.

Maybe sure your launch is level and a good throw. Some times people will push off with there thumb and create a roll, so be really mindful of how you’re releasing the airplane.

The airplane will take the direction of travel from where it was pointed when you armed it and set Auto-takeoff mode. I will leave the plane on the ground in the direction I plan to launch, arm it, set take-off mode, then pick it up and throw it. I try not to turn it much while I’m picking it up. I’m probably being overly careful but it’s working for me.

Before you launch, make sure your heading reported on your GCS or telemetry is what the plane is actually facing (or at least close enough that you’re comfortable) If there is a big discrepancy that may be why the plane is rolling one way or the other.

Yes, I did exactly same as you described. arm the plane heading to the direction where the plane does auto takeoff. I have uploaded the vedio from the cam on the plane and third person view together with the flight log. I have tried about 10 times hand launching. it is always turn to right once the plane left hands. I can the message from the screen with direction degree. is it possible we can set this number.


Post a .bin file with the take off and then hopefully myself or someone else here can find out if there’s something going on.