anyone flying HK phantom FX61 flying wing with APM/Pixhawk are welcome to discuss here. to start with i had a major issue in initial setup of AP 2.78. By default the params RLL2SRV_IMAX, PTCH2SRV_IMAX, YAW2SRV_IMAX should have been 1500 as per the notes by default. but they are set to 500 when u download the firmware. this decides the range of control to be used by the integrator. 1500 means ± 15 deg. so everyone correct these parameters on downloading. i discovered this since craft was not responding at all in FBWA mode whereas it was very responsive in ‘manual’ mode.
Hi
I have similar problem with the FX-79 which is the larger brother of the FX-61
I increased the RLL2SRV_P to 0.8 from 0.6 it improved but very little. I thought to increase it more; nevertheless I am not sure that is the problem.
I am using the Old style elevon (plane.ardupilot.com/wiki/ardupla … evon-mode/)
Meaning that the elevon mixing done within my RC. On manual it gives about +/- 75 degree on the each servo for manual when push up+left (left wing) up+right (right wing).
Leaving the RLL2SRC_IMAX and PTCH2SRV_IMAX the default setting of 1500 centi-degrees, the integrator will be limited to ± 15 degrees of servo travel.
I will try to increase these values to 3000.
I think that the default values are for standard plane and not elevon setup
Avi
I am very interested in your findings, I am building the fx61 currenrly…
…by theway: I had the phenomen on my Skywalker 2012 1880 as well: Stabilize was fine, Fwba was fine. When switching to loiter, the thing started to loose height and accelerated to the ground. GPS was fine all the time. I was able to rescure it before hitting the ground, but it was very close, maybe one meter.
I had that “spiral dive” problem on my skyhunter when I had a combination of:
FBW_MIN too low
and
LIM_PITCH_MAX too high
It would pitch up and slow down until it stalled, then nose over and spiral towards the ground. I’d have to switch to manual to get it to recover. I encountered it two times. Once when switching back to auto after clicking out in the middle of a mission and where it was far from the next waypoint. The second time was when I hit RTL from an altitude significantly below the RTL altitude.
[quote=“Noircogi”]I had that “spiral dive” problem on my skyhunter when I had a combination of:
FBW_MIN too low
and
LIM_PITCH_MAX too high
It would pitch up and slow down until it stalled, then nose over and spiral towards the ground. I’d have to switch to manual to get it to recover. I encountered it two times. Once when switching back to auto after clicking out in the middle of a mission and where it was far from the next waypoint. The second time was when I hit RTL from an altitude significantly below the RTL altitude.[/quote]
If it is stalling and spinning in auto modes, you need to follow the TECS tuning guide.
Stalls in FBW-A are quite possible by design, as it is an attitude control mode only, and does not control airspeed. The plane will spin if it is uncoordinated. If you have a rudder, you can configure the yaw damper and the stall will always break level on most, if not all planes.
Well, I am quiet sure that I had the impression that the plane immediate speeded up like hell and lost height…not in fwba, that was fine. But in Loiter fbwb and loiter it becomes crazy. I did not see a stall really…but I ordered my telemetry and will follow your tuning guide and hope that the tremendous amount of work needed will pay off with a plane that flies much better than witha simple fy-dos…