A few hours ago I had a flyaway event with my Quadcopter using an original 3DR Pixhawk Autopilot (don’t know the FMU version).
I was flying for a few minutes in Loiter Mode when the Quad suddenly tilted around 35 degrees forward and started quickly flying away. Stick inputs had some effect although very minor - it kept moving away from me very quickly.
When it became hard to spot I switched from Loiter mode to Althold and was able to bring the copter close to me. I descended and crash laded on a small bush in the area (no damage to the quad).
You had a GPS glitch about the time it pitched forward. Then you raised the throttle to max and it climbed. Not sure if this is the event you are talking about. That is a very old (2016) version of Arducopter you are running.
Yes, it seems like the event. I raised the throttle to get it higher then a building in the area.
I saw the GPS glitch in the logs - it looks very brief.
Yet the lack of control was longer - I think it was from the moment of the glitch till I switched to Althold.
How can I determine how the autopilot reacts in the event of such a GPS glitch ?
How Arducopter handled a loss of GPS 5 yrs ago I don’t recall. I think it had GPS failsafe action but the glitch had to be >5 sec, then it would switch to Land mode or AltHold. You should really update the firmware. Even if you have a 1mb Flash Pixhawk (I have one) it will run the latest version lacking a few features that were not in 3.3.3 anyway.
That’s a long jump from 3.3.3, there are probably twice as many parameters. But yes, I would do all of the mandatory calibrations and then read thru the Tuning Guide. Update Mission Planner to latest beta and use the Alt>A plug-in to set the basic tuning parameters. Unless it has props >24" that is.
The FS action in 4.0.5 is much more sophisticated than what you were flying. That brief glitch you experienced probably wouldn’t have been noticed.
If you use QGroundControl and navigate to the firmware install screen and connect it will say what the flash size is.