Gpro on 450L Dominator - Snaps sharply to the right (anti-clockwise)

[Pabs]

I'm probably missing something, but as I cannot work out what it is perhaps someone here can!

When I hover my 450L Dominator, the tail pulls/snaps sharply to the right and holds this position - I can move the tail both directions but it seems to return to this position afterwards as though it was locked to this heading. The same appears to occur in rate mode, although I haven't been confident enough to let it go too far so it'd probably just continue to piro.

My tail is set up neutral with 0 degrees, and within the software both left and right sliders are equal.
There is no binding, and on initialisation the tail seems to be centered.
My gain settings are 80 within the software, and I have a switch on my DX8 selecting either 75%, 90%, or -50% for rate mode. Same problem occurs on all gain settings.

My Throttle curve is, for now, a flat line around 65%. (This is to allow me to set it up and gain confidence before I increase it to 70/75%.)


The only thing I can think of is that I need the neutral setting to have pitch on the blades as per the manual (somewhere between 4-10mm measuring across blades) - but i'm concerned that this will only make the problem worse (it'll increase the pitch pulling anti-clockwise)

Any ideas?
Thanks

[coolice]

Hey Buddy.

Definetly the tail with the Gpro does need to have the small amount of offset/pitch on the tail blades to counteract the torque, this makes the tail gyro work much better, so I would advise adding it.

The snap in interesting, as in rate mode the tail shouldn't even return to a previous heading, in fact in high winds it might even weather-**** into wind.
What do you have the other tail parameters set to, off the top of my head there is a P & I gain with the Gpro?
Been a little while since I've flown one sadly as Align seem to have forgot about it with the sudden rush or quads, so I moved away from it to.

Ian

[Grumpy]

The only thing I can think of is that I need the neutral setting to have pitch on the blades as per the manual (somewhere between 4-10mm measuring across blades) - but i'm concerned that this will only make the problem worse (it'll increase the pitch pulling anti-clockwise)

Actually, no, the opposite is true. You set the blades to give clockwise counter torque at neutral. That's to resist the reaction torque of the rotor drive which otherwise would spin the fuselage anti-clockwise.

[coolice]

Actually, no, the opposite is true. You set the blades to give clockwise counter torque at neutral. That's to resist the reaction torque of the rotor drive which otherwise would spin the fuselage anti-clockwise.

Well spotted mate, if he's adding it in the wrong direction.

Another thing you might consider and having done it msyelf and seeing the benefits, is to do the "grip flip mod" to the tail grips. Change them them from leading edge control to trailing edge, this changes the neutral position of the tail slider to make it more centrally located with the required amount of tail pitch to compensate for the torque. Thus allowing a more equal tail throw left & right.

Ian

[Granpappy]

On page 1 of the Gpro setup, does the channel 5 slider accurately reflect the gain settings on the transmitter. Ie switch to HH on Tx and slider should move to + whatever you've set. Switch to Rate mode and the slider should move to - whatever you've set. + 70 and -50 would be a good example. Also on the parameters page take note of your cyclic settings, set beginner mode so all settings including Tail rotor go to beginner settings. Then re-enter your original cyclic settings unless you want to keep beginner mode settings on everything. That should set all your tail rotor settings to basic.

[Pabs]

Hi All,

Ok maybe this is where I'm going wrong - I thought that the torque from main rotors would pull the tail to the left (clockwise) and so you add positive pitch to the tail blades thus pulling the tail to the right to counter the main blades.

The manual looks like they suggest adding positive pitch to the blades as well, which is why I believed that this would make my problem worse?

[Pabs]

Granpappy - yes the tail gyro slider perfectly matches what I've set on the TX - with the figures I've quoted above.

[Pabs]

Ian, I've updated my first post ref the rate mode - I haven't let it go too far as not a confident flyer (still) so I suspect it'd just continue to piro in this mode - suggesting to me that there is too much pitch on the tail blades (or too much torque compensation)

[Granpappy]

I don't understand the above. Even with zero pitch at neutral position the Gpro should still lock directional control with heading hold until you put in a stick movement. After setting up, I always check the gyro sense in heading hold by holding the heli nose in and turning left and right with a tail rotor blade pointing towards the floor. Imagine that blade as a boat rudder so it will turn to counteract the direction of movement. If that makes sense.

[Grumpy]

Hi All,

Ok maybe this is where I'm going wrong - I thought that the torque would pull the tail to the left (clockwise) and so you add positive pitch to the tail blades thus pulling the tail to the right to counter the main blades.

No. If you imagine for a moment you took the tail blades off...Reaction torque would make the fuselage spin anticlockwise i.e. opposite to the direction of blade rotation. The tail rotor therefore needs to produce thrust that pushes the tail clockwise (left) to balance the reaction torque from the main blades.

But Granpappy is correct, even if you set zero pitch the gyro (in heading hold) should still hold the tail reasonably well. If the tail drifts significantly in heading hold then either the gain is too low and/or the headspeed is too low... But this doesnt mean that you shouldn't correctly set the pitch as the manual tells you to.

[Granpappy]

The point I was making earlier is that with Gpro you can have TR direction control set up correctly on the transmitter but the Gyro sense incorrect...ie. opposite way round. Definitely worth checking.

[Pabs]

So hovering today with the pitch in neutral doesn't seem to have made a whole lot of difference, perhaps a less severe kick to the right.
Certainly under rate mode the heli wants to piro unless I counter it with approx. half stick throw to the right, pulling tail to the left.

I've dropped gain on TX to 65% (DX8) which seems to have the model holding OK in a hover, but if I input and rudder from tx it seems to overcompensate or "bounce" around a bit before settling on a heading - not always the heading I expect it to be.

Oh, and I've increased throttle curve a bit to see if that helped, but don't think it has.

Anything else I'm missing?

[Pabs]

See attachment for parameters currently set up.
Thanks!

[coolice]

So hovering today with the pitch in neutral doesn't seem to have made a whole lot of difference, perhaps a less severe kick to the right.
Certainly under rate mode the heli wants to piro unless I counter it with approx. half stick throw to the right, pulling tail to the left.

I've dropped gain on TX to 65% (DX8) which seems to have the model holding OK in a hover, but if I input and rudder from tx it seems to overcompensate or "bounce" around a bit before settling on a heading - not always the heading I expect it to be.

Oh, and I've increased throttle curve a bit to see if that helped, but don't think it has.

Anything else I'm missing?

Hey Buddy.

You need to trim the tail pushrod to hover as close to hands off as you can while in rate mode. So this will set some tail rotor pitch against the torque reaction on the models fuselage, so you'll be having nose right tail pitch input mechanically introduced by adjusting the tail pushrod length.

Are you using govenor mode on the Align ESC? If yes, disable it and just use a linear throttle with flat throttle curves.

Ian

[Mike Sanders]

I am no expert but I would give it some tail acceleration. I would increase both rudder stop settings. I think the setting at the bottom right should be set for small helicopter, not large.