RTH wanky behavior

[neistow]

Problem

When using RTH, Cruise, and LOITER modes, the plane begins oscillating (?) on the yaw axis, then loses altitude and turns completely sideways.

I've attached a video with a sample footage (no black box, unfortunately). There might be a second or two of desync between the footage and the OSD, but overall, it represents an accurate OSD.

Things worth pointing out:

1. On all the footage, the home arrow seems to be alright, EXCEPT the last one, where it goes completely crazy (maybe OSD desync, but I doubt it)
2. I checked the GPS coords and compared them to the video footage, and they seem to be correct.
3. Plane is mechanically sound and flies well in ACRO/ANGLE
4. RTH seems to work fine till some point on the clip with autolaunch.
5. I did notice a weird behavior from my GPS: 2-3 timeouts and a couple of errors, also it alternated between 12 and 0 sats. This was when the plane was still on the ground, powered by a USB from a phone. There were no warnings/errors during the flight.
6. Don't mind the artificial horizon being way too down. I was messing with the osd_horizon_offset and left it set to -2.

Hardware details

Model: heewing t1 ranger
FC: Speedybee f405 WING (not mini)
GPS: HGLRC M100-5883 M10 GPS
RX: BetaFPV SuperD Diversity ELRS
VTX: Walksnail Moonlight

Software details

Firmware: INAV 8.0.1
Plane type: airplane without rudder
Enabled sensors: Gyro, Accel, Baro, GPS, Virtual Pitot

Additional info

Flight footage: https://youtu.be/D6zvXhlyaiY

Please let me know if you need additional info

[shota3527]

Hi, it is hard to debug via the DVR
Could you display the heading and the course over gound on osd next time you flying?

[neistow]

Hi, I will. Thanks for the reply

[MrD-RC]

I'm not being funny, but even in Angle it didn't seem very stable on the roll axis. What is the chance of recording a blackbox log and providing a diff all. What aircraft is this? A fair amount of the flights seemed pretty slow.

[neistow]

It is heewing t1 ranger. I can provide diff all, but I won't be able to fly in the next few months or so, but I'll record blackbox as soon as possible

[Allerhopp]

Is there any chance this behaviour is related to M10 GPS? My wing flew flawlessly with a Beitian BN180 GPS. I wanted to improve the waiting time for GPS fix (was about 4 min), that's why I switched to a BE182. Fix was indeed faster but the wing showed a very strange behaviour in position hold - very similar to the behaviour in this issue. The only difference between the two setups was the GPS type.
No time for a crosscheck, maybe next week ...

[sensei-hacker]

The M10 (BE) chip even with the small 182 antenna should be good enough in most cases. Unless you're in a canyon / between buildings or under tree cover, or there is a lot of interference from other RF sources.

The M9 (BK) is the higher performance chip, and a larger antenna improves performance. So a BK-880 would be "better".

The T1 isn't a tiny whoop, so you don't have to use the smallest GPS antenna.

But again, in most cases the GPS you have is sufficient.

[neistow]

Didn't have the ability to fly for almost a year. I reflashed to INAV 9, enabled, and calibrated the compass, changed the PIDS and default navigation modes throttle values, and now the issue seems to be resolved. The plane successfully returned from a distance of 1.2 km back to home against the wind

@MrD-RC If there is a way to strip GPS data from logs, I can share a flight log if you're willing to look at it

[sensei-hacker]

if there is a way to strip GPS data from logs

Run blackbox_decode to turn the binary log into text. Then, near the top you'll see the GPS coordinates of the home point. Those are the only actual GPS coordinates. All of the other location data is relative to home, "150 meters south of home".
So you can adjust those a little bit.

1 degree change is about 69 miles / 111 kilometers, enough to maintain some privacy without really messing up the math.

[breadoven]

You can get GPS data to display in Blackbox viewer (https://github.com/iNavFlight/blackbox-log-viewer) but only by replacing the files in the last release version 7.0.1 with the corresponding files from PR #102. Install 7.0.1 then go into the installation folder and you should be able to find the files that need replacing. At least it works on windows that way. If you do get it working look in settings to enable the GPS data and it should be available to view. Unless there's a nightly build of Blackbox viewer that included #102, I couldn't find one.