Ok good to know, I do have a set of Rail 716s that I’ve done some testing with, but I’m trying to maximize flight time, so I’m betting the Spins will come out on top, but should be interesting to see, I plan to test both. My total takeoff weight is at 18.5lbs, so not sure if I can get down to 1,350 with the Spins at a reasonable hover pitch. The 710 Spins that I’m running are the version VII, the older 710s had a blade width of 65mm, the VIIs have a 79mm width, so significantly more blade area, but I have a set of both.
I tested RotorTech, Spins, Rails and the stock Aligns. The Rails were the best here on both 600 and 700 class heli’s running at ~380 fps tip speed at normal takeoff weights and ~400 fps at full takeoff weight. They didn’t cause as big of a hit on power consumption to increase headspeed as the Spin Blades and the helicopter is much more stable with the Rails. I flew the Spin Blades for over a year, though, and other than excessive vibration in high-speed turns they worked fine.
Just got back from a few more test flights, it has no problem hovering at 1,400, no significant change in hover collective. The bad news is, whatever’s causing this, it seems to be getting worse each time I fly now. I lowered the ACCEL_Z_P value all the way down to 0.03, and it seemed to have no effect at all, if anything the collective oscillations actually got worse, so I don’t think this problem is related to that parameter at all. I’m starting to think this is something mechanical being I didn’t have this issue at all while tuning or after tuning flights, I first started to notice it about 2 weeks ago.
The last time I spooled up the motor, it almost flipped on its side when the skids were on the ground, so it’s definitely getting more severe and pretty scary, for the next troubleshooting tests, I think I’ll have to take the blades off.
I checked the rotor head, swash, and all the linkages, nothing is loose or has excessive play, so I’m wondering if it might be a bad servo? If so, is there any way to detect a faulty servo from the dataflash logs? I’m thinking this might be the cause, because when I was checking everything over, the pitch and roll servos seem fine, but the elevator servo has kind of grinding sound and it doesn’t feel smooth when you move the arm up and down with no power, kind of like the gears are damaged.
There’s no way to tell it from the flash logs. But a servo that makes strange noises is definitely suspect.
Ok, finally solved the problem, all the servos are ok, the problem was one of the servo leads had worked itself loose to the point where it was intermittently losing contact, so that was causing a severe collective oscillation each time it happened. I just re-mounted the pixhawk a 1/4" higher and 1/4" further back and cable-tied all the servo leads together, it was the servo with the shortest lead (barely reached the servo rail previously) that had worked itself loose being it had a slight amount of tension on it, after remounting this problem has been eliminated. Really lucky I didn’t have a crash, but this is why I always do a lot of test flights with any new machine.
Additionally, I adjusted these parameters down to the range you recommended:
ATC_ACCEL_P_MAX,90000 ->50000
ATC_ACCEL_R_MAX,85000 ->45000
ATC_ACCEL_Y_MAX,27000 ->20000
It does make it much more docile, but I noticed it also becomes much more “floaty” in wind gusts, especially when hovering, so I assume lowering those rates will equally reduce the flight controller’s responsiveness for countering wind gusts in both position hold and auto correct?
That is correct. It has a global effect on angular acceleration limit.