APM 2.6: Battery failsafe behaviour - is this normal?

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1

Hello everybody,

I have recently been doing some battery failsafe tests with the APM 2.6 on my plane
(Firmware from 3 weeks ago). I want to confirm the following behaviour that I encountered:

I was flying a mission in auto and activated the battery failsafe at 65% battery. At some point the failsafe kicked in and the APM changed mode to RTL. Now, I quickly changed modes with my Tx from AUTO to MANUAL and back to AUTO again. I supposed that the APM would automatically switch back to RTL as soon as I entered AUTO mode again. However, I think the plane went on flying the mission, although the battery failsafe has already been triggered.

Is this behaviour normal and can somebody confirm this to me?

Regards,
Roman

2

@tumbili,
What do you have your MIS_RESTART parameter set to?
Regards,
TCIII GM

3

@TCIII
Thanks for the fast reply first of all.

I cannot tell you at the moment because I don’t have the APM with me right now.
However, let us assume the MIS_RESTART param is set to:

  1. RESTART -> I suppose the APM will restart the mission no matter if there has been a battery failsafe before???

  2. RESUME -> here I hope that the APM will switch back to RTL, and will not navigate to the next waypoint in the mission schedule.

Are my assumptions correct?

Kind regards,
Roman

4

@tumbili,
Example:
If it is set to Restart, then going from Auto to Manual and back to Auto will restart the entire mission.
If it is set to Resume, then going from Auto to Manual and back to Auto will cause it to try and finish the mission starting with the next waypoint before the Mode was switched to Manual.
Regards,
TCIII GM

5

@TCIII
Thanks for making this clear. In this case I think the APM’s behaviour can lead to an unwanted situation.
Imagine you are letting your plane fly a mission and you have set a battery failsafe in order for it to come back at some point even if it has not finished its mission yet. The plane will enter RTL mode and head back.
Now imagine you incidentally change the mode of the plane from AUTO to some other mode and back.
In this case I would still believe the plane is still coming back because the battery failsafe has been triggered earlier. However, it will resume or restart its mission and perhaps never come back because it ran out of battery power. The point I am trying to make is that the APM forgets about the failsafe just because the user has restarted or resumed the mission accidentally. I personally think that this can be a dangerous behaviour. Of course you can ask yourself why on earth should you change modes in such a situation but I think this can happen.
If my assumption of this behaviour is wrong, please correct me.
This is by the way closely related to another question I would like to ask. A few weeks ago I flew my plane having set up the battery failsafe to some value. After the failsafe had kicked in I changed the failsafe value to a lower value via telemetry and flew the plane for some more minutes. I was surprised that the APM ignored the second failsafe and never changed mode to RTL again.
Again, can you confirm this from your side.
Sorry for being so annoying but I really want to be sure about this.

Regards,
Roman