FBL Gyro Tail swinging to the right (half circle) during initial spool up

[kywildcats]

Found this site on youtube and it has helped me tremendously during my new 450L build. So far so good on the build and doing flight testing now. Just about have most of the flight settings complete until I get to the very end of my flight. Ok, let me back up a sec. During first spool up to bring up head-speed the nose with yaw left (if standing from rear, tail-in) for about a half a circle until my head-speed climbs then it lifts off with no issues. The heli hovers wonderful. It hovers like someone thumbtacked the thing in mid air. I'm very surprised after reading and hearing all the negative press about the 3gx. It flies good so far. Forward flight seems fine. Turning is the same. Then the second part I am not understanding. When I come down to land in IU1 then hit throttle hold when I'm very close to the ground it will land then start spinning rapidly, causing a slight blade strike. No big deal, but damaged my blades. Below are my settings.

Version: 3GX v5.0
Radio: DX8
Pitch curve: All linear
Throttle curves: Normal: 0-25-50-75-100 IU1: 85% Flat across IU2: 95% flat across
Heading Hold mode (green light on 3gx).
Transmitter gyro setting: normal: 32% IU1: 30% IU2: 27%
3GX PC software Rudder gain is 36. When I adjust my gain on my transmitter from 32% in normal mode the slider on the pc software increases. You think by increasing this value this could correct the tail swing right on lift off and after hitting throttle hold during landing? What rudder gain value should I be at? I know this is all relative, but does 36 sound low to you compared to what you have seen? If so, I'm going to try and update this value 36 to around 45-50 in the pc software and see if that makes a difference.

Any input or help would be so appreciated.

 

[Slobberdog]

I would try raising your gain as you said, raise it till you get wag then back it down a few points, say 5%, sounds like the only thing that could explain the spin on landing is the loss of authority, when you auto get it down as quickly as possible as you will lose tail authority as your head speed reduces.

your throttle curve in norm would be better at 0-40-75-75-75, this will help with the spool up a bit but you will still get a little tail movement on spool up but not 180% worth, you need head and tail speed to combat the thrust/torque your getting off the pitch on the main blades,

 

[Graham Lawrie]

In the 3GX program do you write it when you have made changes? If not changes may not be saved

 

[Lee]

What are you landing on? If its very slippy, the heli will always spin on take off and landing.
Try it on something with a bit of grip.

 

[Tony]

If it's swinging to the right when you spool it up, that is normal if you don't have good slow start up. It's over powering the tail. As long as it doesn't do it in flight, you are fine.

 

[kywildcats]

Hey guys! Thank you for your insight. I took your advice (slobberdog) and adjusted my throttle curves to 0-40-75-75-75 and that seemed to really help in addition to me working with the tail rudder gain adjustments. I ended up with a TX gain setting in the 33-35 range on normal and 28-30 on IU1 and IU2. Tail seems to hold well, hardly any spinning now. Seems to have good speed transition between normal and the IU1 and IU2. I tell you, this 450L really sounds intimidating for such a small heli. I fly my 550 DFC and this 450L makes me pucker more it seems. lol.
Appreciate all your comments and suggestions.

 

[Chordline]

Hello
I'm having this same issue with my 450l 3gx spins at least 180 on spool up.
I'm using a Dx6i tx and in rate mode (50%) I cannot seem to adjust the push rod far enough to eliminate the right tail yaw. In heading hold mode (66%) the tail still spins 180 to the right on spool up, but when I pick up into a hover the tail is rock solid. If I up the gain any higher the tail starts to wag and does not seem to help with the spool up problem. Can you elaborate on what it is you did to fix this or can anyone else help?

 

[Slobberdog]

Do you have soft start set up on your esc, sounds like it's kicking on start up due to the main rotor torque the when tail speed gets up it holds well

 

[Tony]

Put some rubber on the skids, this will help stop the issue. Also, as stated above, make sure you have a really good soft start in your ESC. As long as it's holding steady in the air, you should be fine. ,