APM 2.6 running 3.30 on a Skywalker airframe which has had 30+ flights and seems to loiter and fly basic missions pretty well. It was ‘tuned’ on autotune=5, I haven’t worked thru any TECS tuning process. Stall Prevention is disabled as I have struggled with hand launches in FBWA since updating to firmware supporting this feature, tho I’m not sure whether this affects that or not.
Wind on the day was NW, light winds (haven’t tried to work it out from the logs).
In the minute leading up to the stall…
Flying in FBWB mode (generally into wind), it is slowly losing altitude ( approx 30ft/min), during this time it’s applying throttle on and off and gradually increasing the amount of elevator applied all with no effect on altitude hold. Over the same period of time, airspeed falls from around 14.5m/s to 13 m/s (TRIM_ARSPD_CM :1100 )
I turn downwind and it loses a little airspeed (down to just above 12m/s) at which point the APM applies a boot load of elevator and throttle which starts a stall. Airspeed increases to over 20m/s as I engage manual mode to eventually recover the model after losing about 120 meters alt and a little more hair.
For comparison, a flight earlier in the day which involved 4 minutes of ‘loiter’ whilst re-calibrating the airspeed sensor (for no particular reason), it maintained it’s altitude ok, but the airspeed was dropping despite the APM applying increasing amounts of elevator/throttle.
A few settings :
TRIM_ARSPD_CM 1100 (24.6mph/40kmh)
Video : youtu.be/IoXS5p2h9HI
If anybody could take some time to have a look and offer any advice on this or anything else you can see in the logs in general it will be greatly appreciated. I understand the time required to trawl thru logs so if you get to take a good look, name your charity and I’ll make a donation.