It seems that it I an only hold rather gentle descent rate in loiter. Otherwise it starts to wobble and flop around. I suspect that it is simply descending through it's own prop wash and making the accel go nuts. I can control that with the stick, and I might try messing with the down speed parameters.
Bigger problem is that it does in this in RTL as well. My RTL altitude is 150ft, so from that down to it's "final approach altitude", the thing goes nuts. It is descending way too fast. Once it gets into that final descent phase, it is nice and slow and works fine.
What speeds can I adjust to reduce the maximum descent rate in loiter and RTL?
Replies
I will try this tomorrow when the winds calm down a bit. 15G30 is probably not a good test environment today. I believe the descent phase in RTL works the same as LAND. I have a lot of other P values and trims to adjust as well.
WP_NAV_DN is used for loiter and alt hold descents, and for descending from Current/RTL altitude to 10ft AGL. At 10ft it is essentially final approach and uses the LAND_SPEED value, which is notably slower for obvious reasons.
So it sounds like my WP_NAV_DN is what I need to reduce. I probably should look at the telemetry vertical speed to see what point it starts getting unstable, and set WP_NAV_DN for a hair shy of that. That will keep it from going bonkers while descending in Loiter, Alt Hold, RTL, and LAND. Once it hits 10ft, the LAND_SPEED kicks in and slows it down very nicely.
Sounds like you need to increase your rate P gain a bit if it wobbles a lot while descending.
There are loiter climb and descend parameters in the PID's screen of Mission Planner. I think you can find the RTL descent rate in the full parameters list.