Does anyone know why the motors on the P4 surge a few times after arming them? The props are not self tightening like the P3. It seems like it would create additional stress on the motors and prop assembly.

I would say its a power on self test. Pretty much like a PC when it powers on it tests everything before allowing the machine to Boot up and work.

scarper Posted at 2016-6-2 23:33
I would say its a power on self test. Pretty much like a PC when it powers on it tests everything be ...

Thanks, you could be right

I believe it is a way for the P4 flight logic board to check for the presence of properly attached props on all four motors by looking for resistance to increased motor speed. If you arm your P4 with no props attached, for example, you will typically get a warning message while the P4 is on the ground with motors running.  I can't remember the exact message - something about rotors. This testing is a good thing. For example, if one or more props were not securely mounted (due to incomplete or improper quick mount procedure), then a prop could fly off shortly after takeoff resulting in a crash.