Strange behavior after GPS glitch while in ALTITUDE mode

Hi all.

I’m building a 6 inch quad and I’m experiencing some interferences from my CADDX VISTA affecting my GPS.

This has been a long nightmare, with a lot of trial and error moving the antenna and GPS as far as possible, but with no luck till today. Maybe someone on the same page can share how to overcome this issue with their own build.

On the attached log file you may see that a EKF failsafe is triggered after a GPS glitch while flying in ALTITUDE HOLD.

My issue is that this failsafe makes my quad unflyable, crazily moving towards a direction and barely not reacting to my sticks commands.

From my humble opinion seems that the quad is trying to move to the incorrect received GPS position or reacting somehow to the EKF failsafe, but I cannot understand how is this possible while flying in ALTITUDE HOLD, where the GPS should not be used by the EKF engine, even worst in case of a failsafe.

If this happens in ALTITUDE HOLD, I’m almost sure it will happen in STABILIZE mode.

Maybe my though is completely wrong and so:

  1. Can someone understand the behaviour of the quad and how far from reality is my though?
  2. If my though is somehow correct, would a second GPS help on avoiding GPS glitches and this behaviour?
  3. Does someone face the same issue with the CADDX VISTA interference and any ideas how to overcome the issue?

Currently my GPS is 15 cm way from TX and antenna (a TBS antenna), which are installed at the front of the quad, and the GPS is at the rear.

My setup:

  • Arducopter V4.2.2
  • Frame: Rekon 6 with custom parts
  • GPS: matek gps m8q-5883
  • FC: goku f745 aio
  • RC: Crossfire nano SE
  • Motors: T-Motor F2203.5 KV1500
  • Video: CADDX VISTA with Polar Starlight camera + TBS Triumph Pro antenna

Thank you.

2022-08-18 (624.2 KB)

Tiago I suggest you remove the VTX that is causing the interference, activate the notch filter, properly tune the copter based on the instructions on the documentation. Then read the RTL and failsafe documentation to understand what is happening with the copter and only after that enable the VTX. Good luck.

This happened because the Vibration Compensation FS triggered. Note that it’s not just vibration that can trigger this (read the Wiki), it can be a combination of things causing an EKF error. The GPS Glitch certainly contributed.

Innovation are out to lunch (>1) and then the FS was triggered:


Just a feedback regarding this issue.
I’ve replaced VISTA for a DJI AIR Unit and had no more problems with GPS or EKF issues.
So, folks facing similiar issues, you should note Vista has a lot of RF leakage and managing to install it in small quads without interfering with GPS is not an easy task.

That’s interesting. You should probably look into the vibrations as well. It’s also quite interesting what happens when the copter goes into vibration failsafe, that can/will affect alt.hold performance.