I hope that someone can shed some light over this matter. I have a Phantom FX61 with a 4S setup. I has about 10h of flight time and is stable in flight. Mostly FBWA and B is used. It can loiter for a long time, did 10mins without any problems. However, when engaging RTL strange things will happen. It circles good and is heading home. Then it starts to wag its wings, first slowly then more and more and after 2 min it dives in to a stall spin. I have saved it every time. This can be reproduced over and over.
FBW min was set to 10m/s and that is working in all other modes. This is just now raised to 12m/s and that helped with the issue when I tested this yesterday. Was it this simple or are other factors involved?
The model is built perfectly and everything is trimmed and straight.
What can cause the wing waggle? Leaking airspeed sensor? Bad roll pids?
Im attaching a log and a video to understand the issue. The log from the APM does not have all the info but if someone can use whats in it and point at the right direction it would be very helpful!
Not sure any of this helps, but just some observations…
If you plot DesPitch and Pitch it appears to demand more and more pitch until it flips out on you i.e. it just stalls.
Now why it’s demanding more pitch I’m not sure. It’s descending to ALT_HOLD_RTL which is set at 100m.
As soon as you complete that last turn before engaging RTL, it slows down dramatically, at least as far as ground speed goes, alas there is no airspeed logged which would have been really useful.
The following is VERY ROUGH approximations using google earth…
It stalls with about 1.1km to go and about 114 meters altitude to lose. Since engaging RTL it’s lost about 80m alt in 800meter travelled which puts the decent rate about right to meet the ALT_HOLD_RTL of 100m. I don’t know how accurate it tries to be, but it could just be that it calculated it would end up below ALT_HOLD_RTL and was trying to reduce the descent rate.
Sounds like increasing the minimum airspeed is a good move to begin with and it might be worth reviewing other params that come into play in the RTL scenario.
Thanks! Yes I will have a look at the TECS parameters. Im just curious why the wings started to wag and then poff, it stalled. I will experiment a bit more.
Thanks! Yes I will have a look at the TECS parameters. Im just curious why the wings started to wag and then poff, it stalled. I will experiment a bit more.
Regards,
Carl[/quote]
I have a FX-61. What are your PIDs? I’ve not found auto tune reliable and your are tuning at a more sensitive level. Please post PIDs