Swash changes height when swithching banks

VBC Touch and Neo VLink with Pro/Rescue.

When I switch banks, the swash changes height. The swash lowers when I switch from Bank 1 to Bank 2, and from Bank 2 to Bank 3, and vice versa. I have the same collective pitch curve on all three banks. Throttle (head speed) is the main difference between banks.

This is causing the helicopter to change change height when switching banks.

What can I do so that the swash stays the same height when switching banks?

Lightness?

regards (EN) / Gruss (DE)

Rainer Vetter

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Yes. I have lightness dialed. It is a 380 size heli, and lightness makes it more enjoyable to fly. I did not realize that “lightness” would affect collective when switching banks. I was under the impression that lightness only affected when shifting from upright to inverted and viceversa.

Hi,

lightness actually shifts the collective curve, and adaptive/dynamically, using the accelerometers.

On the ground, what you see is an offset, which increases with more lightness dialed in.

Kind regards

Eddi

Born to fly ...
forced to work.

I have the same lightness number on all three banks. Same pitch curves on all three banks also. The major difference between the banks is the throttle %. Does it still make sense for the swash to move down as I switch up the banks, and up as I switch down the banks?


**********EDIT**************

I thought I had the same lightness number dialed on all three banks. This was not correct. I had "35" on bank 1 and "0" on banks 2 and 3. So it made sense that the heli would climb down when switching from bank 1 to bank 2 and climb up when switching from bank 2 to bank 1.



Edited 1 time(s). Last edit at 02/12/2021 01:19AM by johnahamelv.

Hi,

please zero out Lightness in all three banks and check. This way, we can determine if it's Lightness-related, or something else.

Thing is, Lightness is not a static mixer, like on some other systems which try and mimic the feature, and I can not tell what goes into it.
But using it on the 200, I didn't find anything odd with it, when switching head speeds. Actually, Lightness with the sensors in the loop should even compensate for unwanted collective jumps.
Only thing I had to get used to is, if I spool up at zero collective _stick_ the main blades already have a slight positive angle, with Lightness.

Usually, the only other thing which goes into collective (apart from stick control and the control loop loading, on the ground, without sensor feedback) is auto trim (inside setup, none, outside setup, whatever there is), so you might notice a difference in swash plate orientation and resulting angles there.

If in doubt, save the setup so you can go back to it later, start over with a new one, just dial in the basic things, no Lightness, and check.

—Eddi

Born to fly ...
forced to work.

I did not realize that lightness would automatically add collective pitch during hover. I was under the impression "lightness" would only activate when rotating from upright to inverted or vice versa. I tested lightness on the bench. It looks like lightness adds collective pitch away from ground even if just hovering in place.

Lightness is a great feature. It makes small helis like the Buddy 380 feel lighter during upright to inverted (and inverted to upright) transitions. However, I wish I had understood the potential pitfalls or limitations associated with it. I was pretty close to the ground when I switched from bank 1 (lightness 35) to bank 2 (lightness 0). The heli drove down to the ground and cracked the skids. Had I understood how lightness worked, I would have made sure to use the same amount of lightness on all three banks and/or switched banks at a higher altitude.

I did not understand your statement about about what seems to be an interaction between "autotrim" and "lightness". Should I dial lightness to "0" when performing an autotrim flight?

Hi,

about auto trim, it's just that these values are _on top_ of the actual trims inside setup.

Inside setup, you trim the swash plate to be level. With Auto trim, you add fine trim so the heli is in balance in a hover, which might require some aileron against the tail rotor thrust and some elevator e.g. to compensate slight CoG offsets.

Means, even without lightness, the swash plate will 'jump' to the auto trim angle when you exit setup, or to level, when entering the setup, and if you have a pitch gauge mounted, it will show the offset, obviously. This confuses people, at times, although it's perfectly normal, explainable, and wanted.

About lightness, what can make a heli feel light or even almost weightless (as in: anti gravity ...)? Lots of Helium or more collective pitch.
Of course, the system can not tell between on the ground, or in the air, so what it does, in layman's terms, it adds collective (like a mixer, shifted pitch curve), but it also uses the accelerometers, to fine tune itself, so you do not have to react yourself (and with much more delay).

Example: fly a small model like LOGO 200 in high wind conditions. Without 'AG', it feels uncomfortable, the model bumping up and down in gusts, and more often than not unpredictable. So you're constantly working the stick, to maintain altitude, and in descents, flares, in a hover, it's even worse.
Cyclic control and tail control is not an issue, it's quick, and it's stabilized.

With AG, the VBar senses the bobbles before you even see it, and it smoothens collective out before you have to, so you can concentrate on your flying.

At the same time, it adds the extra punch or lightness you need, in 3D, and always dependent on the flight attitude.

And at the same time, it makes your flying—no matter what style—more convenient, especially with a small helicopter, because it does the quick collective inputs for you which you might know are needed if you fly such helis all-manual, to keep them from dropping suddenly in certain situations.

Downside, if you switch between Lightness settings, the amount of assistance changes instantly, so if you switch between high Lighness and none, the model will jump like it would if you switch between collective curves, where the handover point or hovering point is not congruent or close by.

Usually I'd disable any assistance, during trim flight, just out of common sense (means, Optimizer, Auto Trim, and now also Lightness).
Also, I would not use Rescue or Beginner / Hovering aid mode, during a trim flight.

But I guess, with light settings as in the LOGO 200 by default (1-digit values afaik, and indoors), it doesn't interfere.
When test-flying the 200 and trimming it, before packing it, everything's already set to the default flight parameters, including Lightness.

Best,

Eddi

Born to fly ...
forced to work.