To failsafe or not to failsafe, that is the question


A question that might be important when flying for real:

My Hexa has a PixHawk running APM 3.1.5 and it’s running with 3DR Power Module with a 4S - 5800 mAh battery.

Today I was outside testing some new programming on my radio and had the Hexa without propellers. I connected a fully charged battery and armed the copter and was using several flight modes with Throttle above 80%.

As the hexa was without props I could do my radio programming without fear of “unwanted” reactions.

As I was programming the radio I decided to wait for a battery failsafe to occur that is set at 14V and behavior is set to RTL. The Failsafe did occur and the mode changed (I was looking for that using APM Planner 2.0.11) but the motors kept spinning happily and the low battery beeping was on, and although the hexa was always on the ground nothing occurred…

When the voltage dropped below 13V I decided to manually switch the mode to stabilize and disarm the hexa.

Wasn’t it supposed to stop spinning the motors or even reduce their speed to the speed they have when armed?? What is the expected behavior in this situation??

The worst is yet to come.

I decided to rearm the hexa, and although the Voltage was at 13V - which is below the Failsafe - it armed and allowed throttle and flight mode changes like nothing was wrong, not even a miserable beeping of low battery. I’ve waited a few minutes but no Failsafe occurred and I’m sure that it would happily continue until the batteries were completely damaged…

What’s up with this??? Besides the possibility of damaging the batteries if it would be flying I imagine when or where it would fall without warning.

I’m adding the log