[TMGsi]

guys, I have a problem with the rtb. 

when activating the switch for this function the drone starts the rtb at full speed, on osd it showed that it arrived at 37km / h and when it arrives at the place from which it took off, where it only remains to descend, for the high speed it is in that process of controlling  the inertia of high speed and sudden stop.  What can this be?  thank you.

[TheOtherCliff]

From what I recall, there is a bug reported there.  There are forum threads about this.  I have used RTB but I can't say that I have ever had this issue.

Here is the setting for this:
- It should obey System -> Settings -> FlightModeSettings:ReturnToBaseVelocity

Here are some settings you should know about, they could be good work-arounds:
- It should also obey System -> Settings -> VtolPathFollowerSettings:HorizontalVelMax
- It should also obey System -> Settings -> VtolPathFollowerSettings:MaxRollPitch (bank angle)

One thread says that if you engage from a GPS mode it is one speed, but from a non-GPS mode it is another speed.
https://forum.librepilot.org/index.php?topic=4466.msg30547#msg30547

Another thread:
https://forum.librepilot.org/index.php?topic=4619.0

[TMGsi]

Now yes.  knowing this bug helped me a lot.  really, when starting rtb by positionhold (or some flight mode dependent on the GPS) the drone goes crazy, it rises vertically and horizontally at the same time and at maximum speed.  start the rtb in the stabilized mode it rises vertically first and then starts to move horizontally and at the right speed.  now with this high value detail it will be safer.

[TMGsi]

I was almost satisfied to know about the bug and to know how to get around.  now another problem arose, when turning off the radio and simulating a signal loss something happened.  three times everything went well, but the fourth time the drone just fell and almost hit the ground, it stabilized again after falling.  I think the FC has restarted or something.  what could that have been?  on the computer inside the librepilot application I saw that the Revolution processor was at 50% on my desk, in flight the processor could be at more.

[TheOtherCliff]

For safety, by default, most (all?) flight modes stop the motors if the throttle stick is all the way down.  On some transmitter or receiver/servo protocols, I can imagine that whatever channel is currently being sent gets a bad value, and immediately after that, it goes into failsafe.  My best guess.

If you look at the health screen in the GCS Flight Data page, you will see a CPU box.  As long as that is green, everything is OK.  I recall that the CC3D gets up around 80% CPU and we try to keep it below that to avoid issues.  I wouldn't worry about Revo having even 75% CPU as long as the CPU health stays green.

I suspect that you could also work around the RTB speed problem with those work-arounds I listed.  Reduce maximum speed or reduce maximum bank angle.

[TMGsi]

strange that he completely stopped the engines after about two seconds after I turned off the radio.  problem with speed in rtb is over. (after you mentioned the bug when rtb activated via gps mode) rtb now only active when in stabilized mode to work well.  It was so good that I doubled the landing speed and the returntobasevelocity.  I will return them to the default values.

[TMGsi]

I returned the default values ​​for landing and returntobasevelocity and even then the same problem happened again (the engines stop and then start again) but only when I turn off the radio to simulate a signal loss.
 

[TMGsi]

 
I think I discovered the reason for the drone to fall when I turn off the radio to enter RTB.  The radio was with loss of active signal and with accelerator to activate in 15%

 I made new test flight and now it did not fall once when I turn off the radio, it does the rtb completely.

    now I can make some safe longrange flights

[TheOtherCliff]

Yes.  It is important to know the difference between RC failsafe (handled entirely in the radio, the FC does not know there is a failsafe) and FC failsafe (RC receiver stops sending signals and FC does all failsafe settings).  Some radios can do both or only one of these.

Some radios can only do "hold last command forever when out of range" and those are "a fly-away that is just waiting to happen".   FC continues to receive a signal from receiver and thinks you are still flying it.