Is there a liquid mecury gravity switch killing props?

What makes you think there is?

Did you mean liquid mercury gravity switch?

The off/kill switch when turning it vertical/(on its side)?  I'm not sure it is mercury involved. I thought they outlawed that stuff.

Hi, thanks for the inquiry. I would like to ask if you're referring to switch that would automatically shut down the aircraft?  If so, you may consider using the CSC mode to your remote controller, however, using this command during the flight would definitely cause the incident. You may refer to the image below. Thank you for your support.

DJI Tony Posted at 6-25 10:01
Hi, thanks for the inquiry. I would like to ask if you're referring to switch that would automatically shut down the aircraft?  If so, you may consider using the CSC mode to your remote controller, however, using this command during the flight would definitely cause the incident. You may refer to the image below. Thank you for your support.

playing back drone mp4 illustrates complete coverage filming until finger double presses intelligent flight battery power on button, all the while under very forcible intense wind from drone blowers highest speeding. dunno why spinning so forcibly intensely, weird.

I doubt it has an analogue device to cut off the motors, Probably a function of the solid state gyroscope.