Hey Gainey , welcome to the forum!
Never played with the FRSKY gear, but their Telemetry based RX's can send back RSSI (received signal strength indicator), wich is an indicator you're nearing full range. be advised, your radio link is dependant on the orentation of your airframe to your Transmitter. if you haven't placed your antennas in good places, you could get a weakening RSSI, then as you turn around you suddenly loose the link becasue your antennas find themselves in the airframe/motor/ESC/battery/whatever's shadow.
Failsafe is a feature of the RX, and it generally has a few flavors:
- no failsafe: servo/ESC commands stop as soon as the link is lost.
- preset failsafe: servo commands go to a predefined "position" when the link is lost. there are a handfull of flavors of this, and it generally not advertised which is on which RX.
-- flight channels only: only the first 4 channels (T,A,E,R) go to a predefined command while the remainder stay locked at "last known command"
-- All channels: all the servo commands go to a predefined state
- holding failsafe: All the channels hold the last known servo command (some of these will exclude Throttle, which goes to no command which disarms most ESCs)
How to set up a pre-defined failsafe usually involves powering the RX with the bind plug attached, with the TX sticks in the desired failsafe position (for most fixed wing, it will include a touch of rudder/aileron to turn the plane in circles, and a good glide elevator, and low or no throttle) , it's generally set when you remove the bind plug . . .
. . . but *READ YOUR RX MANUAL* they're all a little different, and the manual should tell you how to do it right. Some RX's are able to change which type of response it gives depeding on how it's setup -- tht should be in the manual.
For what you're trying to do with throwing an autopilot (AP) into RTH, first, you need to read up on your AP and see how it responds to a loss of servo signals from the RX, and read up on your RX to determine what kind of failsafe it can do. you've got two primary strategies, and how everything is setup will determine which you choose:
- if the AP can be configured to go into RTH when the RX stops talking to it: Set this up, and if your RX goes into "no failsafe", the AP should sense the RX has dropped and click over into RTH.
- if the AP cannot go into RTH automatically when it looses RX or the RX cannot give a "no failsafe" response: set one of your mode ports on the AP to RTH, and set an aux switch on the RX to failsafe to the RTH setting. if you loose the link the failsafe on
the RX kicks in and tells your AP to go home.
- If your RX only has the "flight channels only" or "holding" failsafe . . . you're kinda hosed -- you'll want a different RX. In this case, the AP has *NO IDEA* that you've lost the link becasue the RX is hiding the fact from it. Teh RX is not stopping valid commands or going to a pre-defined state you set as "I've lost my link", so it has no way of knowing it's gone on a jounry of self discovery . . . .
