These following were the steps I did to set up the FrSky TFR8 RX to initiate the fail safe on APM and in case this can help others . I suggest add yours here as well if you have a different TX/RX FS setup.
I suspect other TXs other than the Futaba will work much the same for setting up this TFR8.
1. Disable the fail safe on the Futaba TX. ( MODES, FS, then make sure all settings are set to NOR )
2. Go to END POINT menu and set the throttles lowest end point to 140 or where you can see throttle levels on Mission Planner drop to or below 975. Go out of Modes menu.
3. Make sure all settings on the TX are normal as if not in flight. Rebind the receiver to the radio.
4. Ensure the throttle is in the lowest position where it was reading < 975 and then push the F/S button on the Receiver. (The TFR8 green LED blinks twice when fail safe is set) Now the fail safe is set on the receiver at that position and will go to this setting itself if it loses signal from the TX.
5. Go back into the Modes, END POINT menu and reset the throttle END POINT back to 100%. and your done.
The throttle from the RX in normal use will now only drop to its normal lower level (about 1110) and will only drop to < 975 if it looses signal from the TX.
Make sure when setting the RX FS that all the radios levers and switch settings are in normal position because the receiver will remember what they were set at and will set them back in that position if TX/RX signal is lost.
Its is likely possible that the TFR8 receiver can also be set to initiate any of the flight modes. eg. Land or RTL. if TX/RX connection is lost.