I have been flying for about 4 months with Pixhawk and a custom airframe, weighing about 10kg fully loaded. Every so often I get severe EKF errors such as velocity and position variance. I attribute these errors to GPS glitches, because in the map you can see the plane jumping from place to place. These errors result in severe problems with the PFD: the pitch and the roll can be seen jumping all over the place and the plane has to be taken over in manual mode. The pitch can go from -70 to +70, something this airframe would never be able to do. Sometimes it happens when on the ground (when in FBWA, the control surfaces go crazy for a few seconds), sometimes it happens when flying. Most of the time I don’t get this error at all and the plane flies beautifully.
When I fly with my Skysurfer, I sometimes get EKF errors but the PFD is still normal and the plane can still navigate without problem.
The NK* values in the logs are all over the place, and I can’t pinpoint what could possibly cause this problem. The Pixhawk is located at the middle of the airframe and affixed using Velctro. The wingspan is about 3 meters and the power source is 2 8000mAh 6s batteries in parallel. The magnetometer and the airspeed sensor are not used. I have never had any problem with vibrations with this airframe. I believe it is well tuned as I already made many tuning flights. The GPS is mounted on top and has a clear view of the sky, but I believe it has trouble during turns.
The Pixhawk itself is a genuine 3DR product, as is the GPS (Neo7). It is about 6 months old. We use custom made connectors that are microscope inspected.
I hope I provided enough details and I’d really be happy to have some suggestions. thank you very much
PS The attached log is a bit long, sorry about that, but it takes us a while to takeoff for many reasons