Copter: GCS failsafe should trigger if in Guided mode and loss of telemetry

[rmackay9]

Currently the GCS failsafe will trigger an RTL if the user is flying using the virtual sticks. Theoretically if the user is only using guided mode they might not be using the virtual sticks so the RTL would not trigger.
In practice this may not be a problem because the GCS might be overriding the rc controls even while in guided mode because it needs to raise the throttle above zero.

[squilter]

related to #566

[Hwurzburg]

I tried this today with 3.2 release....no rc radio at all, using Droidplanner...push button arm, push button takeoff, then entered follow me mode...GCS failsafe was set to RTL...pulled the radio off the phone....copter just loitered indefinitely...also tried it while going to a Guided WP...arrived at WP and just loitered...had to be using RC override, since no radio and RX puts out low throttle, neutral everything else when not bound...so, in practice, it does seem to be an issue

[rmackay9]

@Hwurzburg, great, thanks for the confirmation. I believe you're the first person who has actually demonstrated the issue.

[ultrojo]

related to DroidPlanner/Tower#1308 ?

"I lost telemetry signal during follow me. Then mode change from GUIDED to RTL only for a second, then after telemetry signal re-established, mode change from "RTL" to "STAB". not "GUIDED". so the quad crash cause my throtle already in lowest position. "

[Hwurzburg]

not sure...RX was putting out LOITER and low throttle since the TX was never on....my copter always just stayed in guided mode and just loitered.....either during follow me (which is guided mode) or guided mode directly....if RC override had been released, it would have descended since rc throttle channel was at idle...It appears to just never see the GCS failsafe

[R-Lefebvre]

This is fixed with this commit.

R-Lefebvre/ardupilot@8360b3d

Need commentary on if this will be satisfactory for cases where Guided mode is being used for a companion computer. I think it might work, as if the companion computer communication is lost, it will also RTL. The only problem there, is the master parameter is called "GCS_Failsafe", not "MAVlink Failsafe". Randy, you know this companion computer functionality better. Would this all be acceptable?

[rmackay9]

As discussed earlier today this looks good to me.