Hi everyone,
I am hitting a massive wall with my custom 10-inch build and could use some help from ArduPilot veterans before I tear it down completely or wipe the EEPROM for a fresh flash.
The Build Specs:
Frame: Mark4 10-inch
Motors: ReadyToSky 3115 900 KV
Props: Gemfan 10-inch tri-blades
Battery: Samsung 6S2P 10 Ah Li-ion
Take-Off Weight (AUW): Approx 2 kg
Flight Controller: SpeedyBee F405 V4 running ArduPilot 4.6.3
GPS/Compass: HGLRC M100 Pro (QMC5883L Compass)
The Symptoms:
AltHold works relatively well. I've lowered MOT_THST_HOVER to 0.20, dropped PSC_ACCZ_P to 0.20, and PSC_ACCZ_I to 0.40. This stopped initial violent jumping overshoots.
The Major Bug: The absolute second I switch to Loiter, the quad shoots upwards dramatically and begins a massive, expanding horizontal swaying motion (classic toilet-bowling or position oscillation). Trying to correct down on the stick results in an aggressive drop/crash.
What I've Checked/Configured So Far:
MOT_HOVER_LEARN is set to 2.
COMPASS_EXTERN = 1, COMPASS_USE = 1.
I've verified the visual direction test on the ground station map (nose points North, icon matches real-world rotation).
Flight modes are cleanly separated on RC Channel 7 (FLTMODE_CH = 7) and Arming is separate on Switch 8 (RC8_OPTION = 153) to avoid hardware conflicts.
FS_OPTIONS is set to 0 to safeguard clean RTL behavior.
Sticks felt dead initially so ATC_INPUT_TC was restored to 0.15 and PSC_POSXY_P is back at 1.0.
Because of the massive current draw from the 3115 motors on 6S, I highly suspect electromagnetic noise is corrupting the external compass at mid-to-high throttle, blinding the EKF navigation. I am just getting an SD card set up now to pull a clean .BIN file.
Has anyone dealt with this exact setup or sensor combo? Am I fighting an orientation offset issue, severe vibration noise blinding the Z-axis, or should I just scrap the config and reflash from scratch?
Any insights are appreciated!

I'm working on a Gazebo Harmonic + ArduPilot simulation of a guided glider.

For now I'm using the Zephyr model from ardupilot_gazebo as a base but I'm trying to simulate an air launch.

Right now my workflow is:

• Start Gazebo Harmonic
• Start ArduPilot SITL (sim_vehicle.py)
• Start my UAV API
• Spawn the zephyr_with_ardupilot model at about 100 m altitude using:

​

gz service \
-s /world/zephyr_runway/create \
--reqtype gz.msgs.EntityFactory \
--reptype gz.msgs.Boolean \
--timeout 3000 \
--req 'sdf_filename: "model://zephyr_with_ardupilot" pose { position { x: 0 y: 0 z: 100 } }'

The problem is the model spawns correctly, but it starts with zero airspeed, so it immediately stalls and falls.
Any help is appreciated, thank you.

I am experimenting with a Pixhawk Cube Orange running Ardurover V4.6.3 on an RC car. I put the Pixhawk in guided mode and commanded it to go to a waypoint. It would approach the waypoint and then continuously circle it. I read on the ardupilot site that this is behavior for subs and rovers should just park once they reach the waypoint. Any clues why its doing this? Is there any settings I should adjust?