Anxious to start test flying after winter, I did some quick hover testing of my Wing Wing Z-84 QuadPlane in my backyard which has been snow-free now for 3 days. It was 45 degrees with a 9mph wind.
The initial hovering isn’t bad and I had good control on the sticks. The side-to-side or roll axis may need some PID tuning as the length of the wing and the shorter distance between the booms created some rocking at times. However, even with the difficult roll corrections, it never lost control. I need to test and tune in a larger park area next.
I changed Q_A_RAT_RLL_P from 0.2 to 0.3 and the wing seemed much better at controlling side-to-side roll perturbations. I’m really liking QGC on my Android tablet as it allows for easy changes during the testing phase. It even supports QuadPlanes. The image below shows me using it with the larger FX-79 wing.
Although it was a bit too windy to fly, I decided to perform a hover test at the park in 10-15mph wind. In QStabilize mode, the wing did a pretty good job holding position facing into the wind. I’ll wait for a calmer day to test transitions to FBWA and CRUISE modes.
My initial attempt to transition to forward flight showed that I needed more thrust to counter the added drag from the quad booms. When it stalled and started dropping, I could save it by switching back to QSTABILIZE from FWBA mode. I never posted the video.
My initial quick fix was to change the 2-blade 5x3 prop on the forward flight motor to a 3-blade 5x3 prop. The power system should handle this increase without issue. I await testing on a calm day…
The 2nd forward flight test of my Wing Wing Z-84 QuadPlane had the same issue after changing from a 2-blade 5x3 prop to a 3-blade 5x3 prop. The plane starts moving forward in FBWA mode but then twirls around on itself. I’m not sure if the plane is stalling or a parameter needs to be changed until I look at the log file. I have been too busy to look at the logs yet so any help is appreciated.
Zipped Log is here. (5.2mb)
Bin file is here. (10mb)
Param file is here. (17kb)
I think that is normal operation. When Q_ASSIST_SPEED is 0, it keeps the quad props spinning until the end of the initial transition from QSTABILIZE to FBWA. It doesn’t help after that.
It might be that my ESCs are not calibrated, making one stay on longer which turns it around. On Flight 1, a different non-posted video, I was able to fly around to the left in a half-circle using full left aileron. It then flipped around as I let go of the stick. Kind of weird…
Thanks for looking! I still haven’t had time yet, maybe this weekend…
Thank you for taking a look. My suspicion has been that I didn’t have enough thrust so I tried a simple change to use a 3-blade prop but it was a cheap GWS style prop. Perhaps I need a bigger motor that can drive a 6" or 7" prop.
Perhaps the 18m/s is too high. I did not set it so it must be the default setting…which I thought was much lower around 10-12m/s. Here are two speed graphs from my non-VTOL wing testing. The first one was in lower wind and the second one was in higher wind. If I choose a calm day, perhaps I can try 10m/s or 12m/s?
Greg, here is my 2 cents, maybe the forward fly makes the front propeller windmill and creates an induced lift (like a canard) that cannot be conter-balanced by an ailevon because its missing the arm leverage of a stab. In this case you could try to activate brake on ESC ?
It’s a good suggestion, thanks! The ESCs are some older version of BLheli so I don’t have a programmer for it. From Rolf’s graph, it seems like the quad motors should not have turned off yet because I was below 18m/s.
I am thinking of lowering the ARSPD_FBW_MIN value per Rolf and also changing the Q_ASSIST_SPEED from 0 to something low like 10 to see if it helps with recovery.
My 3-blade GWS prop may be crap so I may also try a better 2-blade 6" prop. I should post the video and logs for the one time it did transition to FF and I got a nice wide turn with near full left aileron.
Here is the video I referenced above. This is the initial flight of my Wing Wing Z-84 as a QuadPlane. I’m using the same 2-blade 5x3 prop for forward flight that I used before it was a QuadPlane. Although it hovered fine, the transition to FBWA mode has an issue. It did fly for a while and then lopped around again. I was able to save it by going back to QStabilize mode. The wing is so light, it may not have hurt itself in a crash.
How heavy is the Z84 ?
I estimate your average airspeed while cruising was 10 m/s (graph Wingz84Flight7.bin) respectively 12 m/s (graph Wingz84Flight9.bin). The stall speed of this non-VTOL-Z-84 could be 8-9 m/s. But this Z84 was still not converted to a quadplane and the take-of-weight of the VTOL will certainly be higher and therefore stallspeed too. How heavy is the Z84 ?
Another issue: What about the COG in relation to the quadmotors ?
The motors at outputs 5 and 6 are saturated while motors 7 and 8 are floating at 1500:
The Wing Z-84 is RTF without the quad assembly at 15oz using the 3s 1300mAh Lipo pack. With the two quad bars, the additional weight is 6.6oz for a total QuadPlane weight of 21.6oz (612g). The quad booms were mounted to maintain CG.
Motors 5 and 6 could be saturated to fight the breeze. There isn’t much power in these motors.
One thing I was going to do was to re-calibrate the ESCs. I never re-calibrated them from when I stole them off my 230mm quadcopter.
P.S. In your graph above, the first minute was the video. We then walked over to the saved QuadPlane and tried another flight with the same result.
I checked the motor calibration and they all started together so maybe they were calibrated and I don’t remember. However, you are correct about the C5 and C6 throttle being much higher than C7 and C8.
It looks like I have QUAD and H-FRAME set up so my assumption that C5 and C6 throttle being on the front two motors was incorrect. The motors for X or H frame are in the same position but the rotation is different. If there was a CG issue, I would expect C5 and C7 outputs to be saturated or C6 and C8. I can’t explain why C5 and C6 are saturated so perhaps I need a re-calibration to eliminate this as a reason.
Channel 5: Front right motor, clockwise
Channel 6: Rear left motor, clockwise
Channel 7: Front left motor, counter-clockwise
Channel 8: Rear right motor, counter-clockwise
I re-calibrated the ESCs with Q_ESC_CAL=1 procedure. It worked fine and all motors started together on low throttle. I then did a short hover in my backyard with some breeze.
My RCOU graph still shows a difference with C5 and C6 which correspond to the descriptions below. I also verified H-frame rotations using Motor Test. Perhaps I have some bad motors or ESCs and they are making the wing go nuts during transition to FBWA.
Channel 5: Front right motor, clockwise
Channel 6: Rear left motor, clockwise
