A few comments on how to make the wiki clearer on how to set up Failsafe, and a question on how to test it. Extract from the wiki with my comments:
If you have enabled failsafe (how? I have set my config THR_FAILSAFE to 1 - is that correct?), your copter will RTL back to home, and auto-land after 20 seconds.
To enter failsafe, you must be armed (failsafe does not work when disarmed) and you must set your receiver to output a low throttle signal (below 975µs by default). To send a throttle value that is below your radio's normal neutral throttle value (say 1100), please read your radio's programming manual.
I would make this a bit clearer. For instance, "you must set your receiver to output a low throttle signal (below 975µs by default). This can be done by looking at the Status or Raw Sensor View (Radio) and changing the end point on your low throttle setting so that it is below 975µs. Then programme that into your receiver as a Failsafe setting (refer to your receiver's manual). Then reset your low throttle setting back to what it was e.g. 1100. Test that the receiver Failsafe setting is working by viewing the radio data as above and then switching off your Tx. The Ch 3 setting should now drop to the below 975µs setting. Switching the Tx back on should restore the Ch 3 setting to your normal neutral throttle value. Recalibrate your radio settings once you have completed this exercise.
How do I safely test that this will work? I tried taking my copter outside, powering it up, getting a GPS lock and then arming it and looking in Mission Planner. I could see Ch3 in reducing to 965 when I turned my Tx off, but there was no indication of a change in mode. Oddly enough, I am reluctant to turn my Tx off when I am flying it.
Any guidance on this would be much appreciated as I would like to have this safety feature as insurance to help prevent injury (and crashes and money!).