C of G issue?

[mattscupoftea]

Hi there,
I've noticed that my 130x always seems to 'lean' forward on clockwise yaw rotation and backwards on anticlockwise yawing. So right hand hover circuits drive themselves but left hand ones keep needing to be nudged forwards. Piro hovering also needs constant corrections.

I was assuming that it's a c of g problem but moving the lipo, adding weight to the tail, seem to make no difference. Should I expect this sort of constant correction? I know hovers need input and don't fly themselves but this constant repetitive 'fixing' from a steady level hover seems to be something unnecessary.

Any ideas?

[nobbycopter]

I believe, although don't quote me on this one, it's all to do with gyroscopic precession of the rotor disc....if you are traveling forward then when you yaw the heli unless the rotor disc is flat/horizontal the direction of lift changes and hence why the heli pitches up or down (the disc will tilt at 90° to the direction of blade lift, it's like trying to steer a gyroscope in that it goes in a different direction to the one you are trying to force it by turning it!)

Hope that makse sense, probably not explained it that well? If in doubt have a google for gyroscopic precession

[Vikki]

Probably the same reason I find CW banks easier than ACW banks. But I see we are discussing the 130X and my little Limpy banks like he's doing it himself Left, right, he don't care. He sweeps round having masses of fun. Which is why I was mortified I had so much trouble translating that to the 450/500. Thanks again for that lesson by the way. Might get a chance to put it into real life practise when the weather is more ammeanable, sigh.

Yep, what Neil said

[tomatwalden]

I believe, although don't quote me on this one, it's all to do with gyroscopic precession of the rotor disc....if you are traveling forward then when you yaw the heli unless the rotor disc is flat/horizontal the direction of lift changes and hence why the heli pitches up or down (the disc will tilt at 90° to the direction of blade lift, it's like trying to steer a gyroscope in that it goes in a different direction to the one you are trying to force it by turning it!)

Hope that makse sense, probably not explained it that well? If in doubt have a google for gyroscopic precession

I'm not certain that would explain Mattscupoftea scenario as I thought he implied he was just hovering ? To be honest, I can't think of anything that could explain that behaviour - gyroscopic precession wouldn't apply when yawing in a hover ...

Another possibility is the pilot! I certainly find that I climb (+ve collective) on a left hand yaw and drop (-ve collective) on a right hand yaw. The reason why - my left hand thumb doesn't move perfectly sideways, so I always end up giving a bit of collective by accident!

Must practise more ...

[Delarado]

It can be caused by any number of things. Centre of gravity, wind, tracking on the heli, all sorts. Something cheap and un-adjustable like that will never piro completely flat, you just have to learn to live with it im afraid... you could potentially try adding a little mix in your TX to combat it but thats not something ive done before!

[nobbycopter]

I'm not certain that would explain Mattscupoftea scenario as I thought he implied he was just hovering ? To be honest, I can't think of anything that could explain that behaviour - gyroscopic precession wouldn't apply when yawing in a hover ...

My impression was a hover circuit which I thought implied forward movement...

I wonder if it's to do with the tail driving round and tilting the rotor thus causing the movement? Thinking about it now I must subconsciously put left and forward on the clclic when doing a stationary AC pirouette and back and right when doing a CW one...will try on the aim tonight

[mattscupoftea]

So it's happening in level hovering flight and affecting slow hovering circuits, inside with no wind. The moment force of the tail force translated thru 90 degrees due to gyroscopic precession makes sense to me. I can't remember from my aero/astro engineering days (it's been a few years) whether it's the right hand or left hand rule to check the theory. I'll look it up when I get home.

I'm guessing that the reason I haven't seen it with the logo 500 is the weight and size difference. It may be happening but just not as apparent. . .

Maybe I'll post a video to show the behaviour. Maybe I have to accept it and continue to learn to compensate for it.

Just seems odd that it's not 'built into' the fbl system if it is standard and controllable.

[mattscupoftea]

Right. Having looked into it, it makes sense that the tail 'thrust' is causing this issue.

On another forum, it's suggested that there is no piro compensation built into the FBL system on the 130X, probably because it would affect the 3D performance of the heli detrimentally.

They suggest that it is indeed necessary to give a little forward cyclic on a ACW piro and back cyclic during a CW piro to keep the rotor disc level. (I think I have got that the right way round)

I guess it'll keep me on my toes! It's good to know that it's not a centre of gravity problem, but inherent in the system, and that I just have to get used to it. I like to know that something is considered 'normal' or 'expected' when flying before I commit to developing habits.

I believe that the Vbar has piro compensation built in - I was assuming that the scaled-up weight issues may make it less apparent, and perhaps this would be the case, but the compensation takes it out of the equation completely. That is why I was noticing the difference between the two helis, which flagged the issue up with me in the first place!

Hope the above makes sense!

The above issue may also explain why some of us have trouble with ACW circuits compared with CW circuits. It's not just that we learned on before the other!

[dogcow]

Isn't this a normal characteristic of ALL Blade Micro AS3X Heli's? I've had to compensate piro's on my mSRX, 130X and nano CPX? I just got used to it

[heathy]

You might want to check the blades are level with each other @ 0% pitch. All the blade micros have the same problem in that 1 blade is off from the other. Flip 1 round in the grip, set collective to 0 and fold blades tip to tip. Probably 1 is off, then sub trim pitch till level and try again. Should help.