Yaw and Roll mixed in Acro / FPV mode

[sommermeister]

Since yesterday I have the following problem:
When flying any map (no matter whether race or free flight) in Acro mode and with FPV cam enabled, the Yaw control behaves in a weird way. When I turn left (on the Yaw stick only), the drone does a roll to the right side as if I had pushed the Roll stick almost to the maximum right. The little yellow stick simulation on the bottom of the screen shows that only the Yaw stick is moved to the left, Roll stick stays in the middle position. And vice versa: when I yaw right, the drone rolls left. This happens with any input device, even with the digital keyboard using 'A' and 'D' for Yaw left and right. The only way to turn the drone with the horizon staying level is to push the Yaw and Roll sticks to the same side at the same time. Otherwise (when only using Yaw) the horizon will always turn like when you are rolling.

This does not happen if I switch off the FPV cam. Seen from the outside cam the drone turns perfectly fine and "in level" (without rolling). In the other flight modes (GPS, Angle) it also works fine. And I'm pretty sure this did not happen in Acro / FPV mode before yesterday.

I'm on Windows 10. I use Mode 2 configuration (Gas and Yaw on the left stick). But I also tried Mode 1 without success. As a controller I typically use my Spektrum DX8 with the SmartPropoPlus driver. But as said - this also happens with the keyboard since yesterday.

I already tried to disable the SmartPropoPlus driver. I tried disabling any other input devices such as my XBOX controller. I tried to change all settings I could find. The effect remains the same.

Does anyone have a hint what I can try to identify the root cause of this problem or what I can do to overcome this situation?

Thanks in advance!

[Cir(oOo)cleS]

Thats a thing me thinks.
You need to yaw and roll together to stay level in acro, something to do with the camera angle and drone pitch. Im sure someone can explain it properly.
If you set your camera tilt to zero it wont happen.

[DCL]

correct.
yaw roll and pitch work based on the axis of the frame (the plane where the motors are, specifically, around the center of mass of the drone)
the fpv camera is installed at an angle (that you can customize).

because of geometry, if the drone yaws to the left and the camera is, for example, at 45 degrees, it will appear to be "rolling" to the right.

if your camera angle is set at 90 degrees, when you yaw it will appear that you roll and vice versa

[sommermeister]

Wow - thank you so much for this explanation! Of course this is true and totally correct physics!

The mistake I made in my head was that for the test in fpv mode I pointed the camera towards the horizon (by pitching the nose of the frame down ~45 degrees because that's my camera angle). I did this in order to see whether the horizon would roll. Whereas when testing in non-fpv mode I kept the drone frame horizontally leveled. Of course Yaw always only did what it should do in both cases. Hahaa - stupid me ;-)

Thanks again!