In case of a radio signal loss the radio manufacturers includes a "failsafe" condition into their recievers. All channels will be kept on hold or set to center (a question how it is programmed) and the throttle / esc channel must be turned to "motor off" to avoid too much damage in this situation.
If the ESC / Throttle servo is connected direct to the reciever please read in your radio manual how to program the "motor off" failsafe. Do a bench chek w/o blades. Run the heli (on nitros watching the throttle servo will be enough) and turn the transmitter off. The motor must stop / throttle servo move to throttle closed now.
If the heli flies with SBus or Single Line reciever the ESC / Throttle servos is connected to the VBar. In this case the radio failsafe will only be active when the tx/rx connection goes bad (the same as above). Please program / check as described above.
For usage with Spektrum Satellites, SBus, Single Line and UDI reciever we have a internal failsafe which is active when the Sats, SBus, Single Line, UDI won't deliver a valid signal to the VBar. This failsafe can be set in the PC software. Turn the motro channel to "off" on tx and press the button. Do a bench chek w/o blades. Run the heli (on nitros watching the throttle servo will be enough) and disconnect the Sats / SBus / Single Line / UDI reciever. The motor must stop / throttle servo move to throttle closed now.
Important hint: Having a correct UDI implementation the failsafe will be done by VBar only. The RX does not deliver any signals in a failsafe condition. So we were able to log this situation which might help in a analysis after such issues.
With the VBar Governor we always use the "motor off" value (Gov 2 tab) for internal failsafe in case of VBar input signal loss.