Yes, a critical failure of the flight controller or power system can still cause it to fall from the sky. I've never had that happen personally and I've logged a lot of hours on custom built quads.
If you are using alpha/beta FC firmware or your settings are still being tweaked you shouldn't anywhere near people anyway.
I've lost engines that resulted in nasty crashes. As I fly quads almost exclusively they are always nasty. As such, I never fly over or near people (other than myself).
I've read of full power loss, but never personally experienced it.
In any case I think I'd be more afraid of bad FC firmware that resulted in a fly-away event. Those are super dangerous as the machine just takes off into the air and away from you. That has the potential to be MUCH worse as the altitude they eventually fall from is significant. If you've never seen a full-power ascent of a multicopter then you're in for a surprise at the speed at which they can disappear while going straight up.
If you are using alpha/beta FC firmware or your settings are still being tweaked you shouldn't anywhere near people anyway.
I've lost engines that resulted in nasty crashes. As I fly quads almost exclusively they are always nasty. As such, I never fly over or near people (other than myself).
I've read of full power loss, but never personally experienced it.
In any case I think I'd be more afraid of bad FC firmware that resulted in a fly-away event. Those are super dangerous as the machine just takes off into the air and away from you. That has the potential to be MUCH worse as the altitude they eventually fall from is significant. If you've never seen a full-power ascent of a multicopter then you're in for a surprise at the speed at which they can disappear while going straight up.