Align GP790 in T-Rex 450, using Spektrum DX6i, can't get heading hold mode?

[Sannan75]

Hi there,

As per the title really, have spent the last few weeks building my first helicopter slowly but surely and I'm now doing tail servo / rudder setup however I can't seem to get the Gyro to come on in heading hold mode which I believe is a green light, I have a steady red light.

I know I'm doing something simply and stupid but not sure what so thought it worth asking.

On the gyro itself I've gone through the setting and made sure it's on 1520 and digital to match the trail servo, Nor/Rev is set to normal and I've not touched limit or delay. I can't really see anything I can do here so I'm guessing there are some toggles on the radio that need to be a certain way when I power on but the Spektrum DX6i manual seems to assume more knowledge than I have and I can't make sense of what should be set where on the switches.


Any idea's or help greatly appreciated, it's sooooooo close to being spun up for the first time and being stopped dead with this at the moment is really frustrating

(oh, and any advice on other radio settings that need to be made related to the gyro also greatly appreciated, I've touched nothing under the 'gyro' on the radio menu or under 'travel adjustment', not sure if I need to?)

Dave

[waveydavey]

Yes you do, you have a gain channel assigned to the gyro that you will need to set +ve for HH mode. I've not used the GP790 but I'll go and take a look at the manual. There'll be a separate plug that you've probably put into the gear channel on your Rx, that is the channel that needs sorting out

[Sannan75]

Yes you do, you have a gain channel assigned to the gyro that you will need to set +ve for HH mode. I've not used the GP790 but I'll go and take a look at the manual. There'll be a separate plug that you've probably put into the gear channel on your Rx, that is the channel that needs sorting out

Thanks waveydavey, the gain lead went into the 'Gear' channel on the receiver, but I'm not sure what that becomes in the radio menu's, or what I'd have to do with it if I did know lol.

[waveydavey]

Yep, you're gain channel needs to be above 50% for HH and below for rate mode, so start at around 65%

[waveydavey]

Thanks waveydavey, the gain lead went into the 'Gear' channel on the receiver, but I'm not sure what that becomes in the radio menu's, or what I'd have to do with it if I did know lol.

You can leave it assigned to one of the switches or you can use the gyro menu and assign a %age for each flightmode I think, I'll take a look at the DX6i manual

[waveydavey]

Yeah you can leave it assigned to a switch or the stunt mode (fm) switch, you need to got to the gyro menu and change from inhibit to whichever method you want to use.

It's channel 5 if you just want to change the endpoints on the channel directly

[Sannan75]

Ok, you'll have to forgive my complete n00bness but never done any of this before.

I've gone into the gyro menu on the radio and it is set to SW-Gyro, I can set two values, both default at 50% and the second has a left arrow next to it. If I increase the first value above 50% the Gyro light goes from red to green and the behaviour of the rudder changes (from self-centering to staying wherever I put it) but if I spin it up like this the tail turns more than when the Gyro was red light.

I guess what I really need is a kind soul to step me through the DX6i menu's and values related to Gyro/HH and what they should be set to to be good to go with HH (in terms of it working, fine tuning will be fine from that point), and what toggle settings I need on the controller (like 'gear/fmode' switch to gear, 'flap/gyro' switch to gyro, etc.


Proper 'let's step Mr Clueless through this' level

[waveydavey]

No you're doing great and what you've seen with the HH is right. It sounds like the gyro sense is in the wrong direction. When you went through the setup did you get this right, IE bend the bottom tail blade out so it looks like the rudder on a boat. Pick the heli up by the tail and slowly move it to the left or right in HH mode, you should feel the tail blade turning the way that you are pushing the tail IE to the left the blade will turn to the left. I'm not too sure about how high the gain needs to be but start at 65%

[Sannan75]

Thanks for the encouragement, been at this all day now Ok, so I've gone to the gyro and the third setting light is Nor/Rev and I set this to 'Rev' (red light) and now with HH enabled it seems to be much better behaved. I had to reverse the rudder servo on the radio to get the tail rotor moving the right way (stick right, nose right) so maybe I just needed to set the Gyro to think the right way?

Enough for today, will get on with fine tuning the tail servo movement and centering another day, thanks again for your help, fingers crossed that last change has got it

[waveydavey]

No need to cross fingers just make sure that at every step the tail is doing the right thing and you'll be fine, hoping that you've got it right is where it all goes wrong

You've done the right thing by reversing the rudder in the Tx, make sure by using the same method above make the bottom tail blade look like a rudder and move your stick to the left the tail blade should do the same, same with the gyro sense direction. Set the gain to 65 or so, set the limits and you're good to go