Tailsitter Duorotor Feedback


I have met you this question, now the aileron and elevator is reverse, I set the pitch_90.
In addition, your motor and steering gear is connected to the 1, 2 and 5, 6 on it?

另外你的电机和舵机是接在了 1、2 和5、6上了吗?


Hello, everyone!

We made a Caipiroshka VTOL and carried out several test flights.
When we transited it from mc to fw mode, it seemed lost control in the roll angle of fw mode, which means the plane flied upside down before successfully transited into fw mode.

We checked the code in “src/modules/vtol_att_control/tailsitter.cpp” and finded that in Line 262-263, it is

	if (_airspeed->indicated_airspeed_m_s > ARSP_YAW_CTRL_DISABLE) {
		_mc_yaw_weight = 0.0f;

	} else {
		_mc_yaw_weight = 1.0f;

I can not understand why the mc_yaw control should be closed in the transition stage.

I am also wondering whether this caused my “upside down” flight before entered fw mode.



The MC yaw control is disabled only for the multicopter control as above a certain airspeed this should no longer be controlled by the multicopter but the fixed wing.

It seems unlikely that yaw (which moves over the horizontal plane) could cause a flip, but tailsitters is not my specialty.


Thank you very much for your kindly help.
I understand your point and it make sense to me. however, it looks like the fw roll control will be involved if the vehicle reach the certain airspeed and a certain pitch angle. I wondering if we just reach the fw airspeed without reaching the pitch angle? what will happen?

our vehicle was not flip every time in test, but quite a lot. That makes me confused…


hi ,

I have built a caiperinha vtol, which flight mode should I use to test my first hover , is it stabilise.

also is there any documentation available to help set up.


yes you can use stabilize mode for hovering. you can find the documentation in PX4 Developer Guide for setting up. BTW, you still need airspeed sensor even for simple hovering.


hi thanks for the response, how is your project going. the Dev guide seems to stop at motor , elevon channel setup. I can’t quite work out orientation. I have my pixhawk mounted with the arrow to the nose of the plane, is this classed as no orientation or pitch 90. also I can’t quite work out how to set the transition switch is this explained anywhere, btw I have airspeed sensor fitted and calibrated. should I be able to gently build up throttle to take off , at the moment the plane just drops forward, I’m not sure if I should try to tether it and start it away from the ground. or give it more aggressive throttle at take off to clear the ground.


hi there goosewso, just watching your videos, I was wondering if you managed to solve these problems, I am just about to make my maiden flight with a caiperinha vtol and wondered if you had some tips.


@thedudevt Did you figure out what is going on. I have the same issue and as @tumbili commented below, yes my aircraft is sitting on my desk. I am using the analyzer in QGroundControl to monitor the servo output but i see no yaw response when i move the stick


also when i flip the transition switch to FW, in Manual mode i dont see and stick response being translated to servo output on the analyzer in QGC but when i switch to Acro mode i can see pitch and roll stick commands translated to servo output on the analyzer but no Yaw out again…I have absolutely no idea what is going on.


hello @PKocmoud did you solve the problem, turns out i have the same issue. Unlike the Caipirinha mine is a quad + configuration though.


@y2kare are you talking about differential thrust for FW yaw?


Yes, but not in MC mode … only for FW mode




Any updates on differential thrust in FW mode for yaw?



Our platform, when we hit the transition switch from hover to fixed wing, does one complete roll, always to the left, before giving me control over the platform. Has anyone seen this before?

Kind regards,



If you don’t close the yaw control of mc,the speeding time will be longer.


当然是万能的淘宝啊 骚年。。。。。。。。。。。。。。。。。。。。


Did you solve your problem?? I’m passing through the same issue


Hi,I have build a duo tailsitter with z84,and calibrated the sensor with PITCH_90,leveled the airframe with PITCH_90 and nose-up,and modified the mixer file to make the response of control surface is correct. when I test it on my hand in multirotor mode with stabilize flight mode,the response of roll/yaw/pitch control is correct,but when I speed up the motors,the airframe tilt down to the ground.I don’t know why.can anybody help me?my controller is pixhawk 2.4.6,firmware is the dev master 1.6.0,thanks very much.

maybe I have to enlarge the control surface area?
I do calibration with fllowing steps:
1.calibrate compass with PITCH_90;
2.calibrate Gyroscope (keep the airframe on the PITCH_90(nose up) position);
3.calibrate Accelerometer with PITCH_90;
4.Level Horizon(keep the airframe on the PITCH_90(nose up) position);

I’m not sure it’s right?