Fixed wing launch mode failsafe fixes

[breadoven]

Closes #10483.

[Jetrell]

I gave it a test by taking off in Auto Launch and letting it climb for a while, then switched to FS mode.
It proceeded to enter RTH and once it got close to the Safehome it started the LAND procedure, which I have enabled.. I tested it twice and it performed the same.. So the fix appears to work.

RTH state and decides it's failed causing failsafe to default to Emergency Landing instead

Can I assume you had to do a scheduling work around to get this to initialize ? I noticed when it entered FS in AutoLaunch ALL the OSD screen characters will systematically flash. Like an OSD refresh was missed at that moment (Analog video).
This is no big issue. I just thought it worth mentioning.
EDIT: Having another look. It may just be that SDIO logging issue with the F765. It affects the OSD too, when more demanding tasks are being performed. Even with a low 3% rate.

Guess not many people have Failsafe's during launch because these bugs have been there for a long time.

I've never had a FS happen at launch.. But after reviewing old mates video.. He was at 325m and AutoLaunch was still going.
At that altitude the TX/RX antenna's would have been operating in their null's.

And as a side note to this being an old bug.. I remember an issue report being opened by a user back in INAV 2.0.. I had a look, but couldn't find it.
It was about a guy who auto launched his plane. And at the moment he threw it, the throw inertia disconnected his RX plug, and the FC entered FS.
From what I vaguely remember. At the time, Konstantin wanted to leave it as DROP... In cases like this, when entering an nav_rth_altitude mode that has no climb out, could cause the plane to turn into an object like a tree, if a FS condition was entered straight after the throw.
Back at the time there was debate about this and nothing was obviously done... In hindsight I think a method to deal with this would be to have nav_rth_altitude overridden to EXTRA, if an Auto Launch FS occurred at less than 40m above the arming altitude.

But in any case, I think your fix was more needed than not.

[b14ckyy]

Finally managed to run some HITL tests last night as well. Can confirm that no issues appeared when FS during Autolaunch, even with long climbs and distances. That was on a F405 though.

[MrD-RC]

So the lowest spec supported MCU 😉

[MrD-RC]

Both tests look positive. So I'll merge it for RC2.