How can I control my plane in FBWA mode

ArduPlane Plane 4.4
,
1

My setup:

  • I am using Ardupilot SITL to simulate a plane.
  • I will have no GPS in my plane.
Setting Value Purpose
EK3_ENABLE 1.0 Fly by inertia
EK2_ENABLE 0.0 Fly by inertia
AHRS_EKF_TYPE 3.0 Fly by inertia
AHRS_GPS_USE 0.0 Fly by inertia
EK3_SRC1_POSXY 0.0 Fly by inertia
EK3_SRC1_VELXY 0.0 Fly by inertia
EK3_SRC1_POSZ 1.0 Fly by inertia
EK3_SRC1_VELZ 0.0 Fly by inertia
EK3_SRC1_YAW 1.0 Fly by inertia
INITIAL_MODE 5.0 FBWA mode
FLTMODE1 5.0 FBWA mode
FLTMODE2 5.0 FBWA mode
FLTMODE3 5.0 FBWA mode
FLTMODE4 5.0 FBWA mode
FLTMODE5 5.0 FBWA mode
FLTMODE6 5.0 FBWA mode

(I wasn’t sure which flight mode needs to be in FBWA mode, so I set them all)

Assume that I fly the plane up to some 1000 meters above ground manually before I start sending this message 5 times per second:

SET_ATTITUDE_TARGET {
    time_boot_ms: now_millis(),

    target_system: 1,
    target_component: 1,

    roll_rate: 0.785,  // (ca 45 degrees in radians to the right)
    pitch_rate: 0.0,
    yaw_rate: 0.0,
    thrust: 0.5,

    type_mask: 128,  // I *believe* this ignores the quaternion I'm not setting.
}

https://mavlink.io/en/messages/common.html#SET_ATTITUDE_TARGET

My assumption is that this should make the plane cork screw very hard to the right, but this doesn’t happen.

  • When the plane is in GUIDED mode, this makes it go forward and slightly up, so it slowly gains altitude. It doesn’t roll.

  • When the plane is in MANUAL mode, it pitches up very strongly and starts looping that way instead. It doesn’t roll.

  • In both modes, if I stop sending the messages, the plane falls out of the sky.

  • What am I doing wrong?

  • How do I know how often a message needs to be resent?

  • Do I need to be in GUIDED or MANUAL mode for this to work?

Edit:

As it turns out, I misunderstood something. The documentation isn’t super detailed, so I ended up interpreting a lot into it that wasn’t there. I discovered this when I was studying some existing code: https://github.com/dronekit/dronekit-python/blob/master/examples/set_attitude_target/set_attitude_target.py#L87-L114

I noticed that they hard code their rates to zero and provide a quaternion, so I now compute the quaternion, set the roll, pitch, and yaw rates to 0.0, and type_mask to 0, and I’m able to make the plane fly in a circle by rolling it 10 degrees.

My plane is in GUIDED mode.

It’s a step closer to what I wanted to do, but some questions still remain unanswered:

  • What am I doing wrong? I feel like there’s ample opportunity to mess something up or misunderstand something.
  • How do I know how often a message needs to be resent?
  • What are the yaw, pitch, and roll rates?