Drifting to the right during piro's

[scornflake]

Hi,

Continuing my Spirit learning / experience.
I've been checking tail performance, and part of that is piro's. Not flips - just straight piros.

I'm seeing significant drift to the right when performing left or right piros.
I realized later (once home) that I didn't have the canopy on when I tried this. This makes the model not 100% perfect in CG (it is tail heavy, every so slightly). When I hold it by the blades and bring the boom parallel to the ground, there's a 1/2s delay as it slowly rotates so the tail points down. However; it's not like it's tail heavy by 50g or anything.

What should I check here? This is on a Warp 360.

Cyclic gain: 50%
Rudder Gain: 1x
Revomix: 0
Ele filter: 1
Piro Consistency: 175
Flight Style: 4
Elevator Pitch up comp: 0
CFF: 5

I've included a video, along with slow-down of the prob as well. When I looked at it, it almost seems as if things begin to go wrong when it's 180 degrees into the turn and it tilts backwards. Direction doesn't seem to matter.

See the first one (Doing pirouette with Warp & Spirit) : https://www.icloud.com/photostream/#A3GY8gBYGTgvcQ

It flies basic flips/rolls and hovers fine otherwise, as far as I can tell.

[Jman841]

Are you certain that piro optimization is correct? For it to tilt that much on a turn I would guess the piro optimiaztion is reversed.

Ensure that it acts like a compass, the swash should always point in the same direction when you spin the heli when you test your piro optimization.

[scornflake]

Good question. I've double checked it, and yes it appears correct.

As I rotate the heli around (like a piro) the swash points to the same direction, aka: like a compass.

[ZeXx86]

Hi,

this is most probably caused by servo settings - cyclic must be leveled with cyclic leveler during Subtrim (tuning) enabled while servo horns are at 90° deg. After subtrim settings, your blades pitch should be zero degrees.
If not, it should be changed with two push rods that are coming to main blade holders..

Alternatively it is reversed piro optimization. There shouldn't be more options.

[scornflake]

I will go double check. The initial setup was done with a Soko tool, so I was pretty sure I was correct on mid and top/bottom setups to ~0.1 degrees. I will double check the entire head setup now.

[ZeXx86]

Please check your piro optimization first.
If you did some settings (especially sensor Z axis reverse) after you have configured this parameter it is possible it is wrong.

[scornflake]

OK, using stock link mm measurements, I was unable to get 0 deg on the Warp360.

I tuned centre of swash to get zero deg, and this results in the arms being "upward" by a few degrees or so.
I am able to set the servo travel correction so that I have exactly 12.5 deg on every link, both in +ve and -ve pitch, while retaining zero deg at centre stick.

Given servo travel correction is setup, MUST the servo horns be centered? I would have though servo travel correction would be doing interpolation between centre and max/min deflection?

[scornflake]

I completely re-did the head setup with my Soko, and on the next flight it was 100% fine.

I then of course managed to tip it over on the landing, and wreck two servos. It was so light I'm surprised; and I'm wondering if the servos were in fact tight before hand, contributing to the issue in the first place. Either way; the flight showed there was nothing wrong in the FBL unit itself. Yay!

[ZeXx86]

Hi,

if you enable Subtrim (Tuning) in the software, servo arms must be centered as precise as possible. If it is not done properly, helicopter can drift and flight behavior not correct.

[scornflake]

In my case there was a reasonable amount of "off center" for each servo arm. Perhaps as much as 5 deg off centre. I setup the offsets (Servo Travel Correction) for both the top and bottom of pitch travel as well. Regarding the drift, I think the swash itself may not have been level. Can't be sure because I've fixed it now

But back to one of my original questions: Am I correct in presuming that even if my swash arms are not level at zero deg, that the linear interpolation done by STC (within the spirit) would correct for this? Yes, I know that I should really go back and fix the mechanical, but even if I chose not to, wouldn't the Servo Travel Correction be sufficient to "correct" this?

Don't get me wrong here: I'm not suggesting that a imprecise mechanical zero pitch setup is ideal. I'm just curious as to if my assumption is in the correct direction. Ideally of course I should go and get everything as close as possible to perfect mechanically before applying sub trim. I get that. Just I was being lazy in this previous case.