RadioLink Turbo PIX User Manual page 37

You can turn off transmitter to check if the Failsafe function setup success(the PWM of CH3 is smaller than
975)
If enabled and set-up correctly the radio Failsafe will trigger if:
(1) The pilot turns off the RC transmitter.
(2) The vehicle travels outside of RC range.
(3) The receiver loses power (unlikely).
(4) The wires connecting the receiver to the flight controller are broken (unlikely).
When a radio Failsafe is triggered one of the following will happen:
(1) Nothing if the vehicle is already disarmed.
(2) Motors will be immediately disarmed if the vehicle is landed OR in stabilize or acro mode and the pilot's
throttle is at zero.
(3) Return-to-Launch (RTL) if the vehicle has a GPS lock and is more than 2 meters from the home position.
(4) LAND if the vehicle has:
no GPS lock OR
is within 2 meters of home OR
the FS_THR_ENABLE parameter is set to "Enabled Always Land"
If the Failsafe clears (i.e. transmitter and receiver regain contact) the copter will remain in its current flight
mode. It will not automatically return to the flight mode that was active before the Failsafe was triggered.
This means that if, for example, the vehicle was in Loiter when the Failsafe occurred and the flight mode was
automatically changed to RTL, even after the transmitter and receiver regained contact, the vehicle would
remain in RTL. If the pilot wished to re-take control in Loiter he/she would need to change your flight mode
switch to another position and then back to Loiter.
Copter also supports Battery, Ground Station and EKF/DCM failsafes.
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