General How to set throttle curve expo in DX7?

[mooserider]

Hi all, I would like to add expo to my heli (Trex 450), because it's really difficult to keep it hovering vertically in position. The throttle stick is so touchy (up/down). Tony had suggested I add some expo a long time ago. I just watched his video on expo and dual rates, and it makes a lot of sense.

But here's the question. I would expect that I'd want to set the expo for the throttle curve, but there is only elevator, aileron, and rudder expo options in my DX7. I must be missing something obvious...?

Thank you for any advice you have!

 

[mooserider]

Actually, I think I just found this right after posting. In the Pitch Curve settings you can toggle expo on/off. I think this is what I'm looking for.

Maybe someone can tell me if this sounds good before I try flying it tomorrow. My pitch curve was linear. Now I've changed it so it flattens out a little around mid stick: 0, 35, 50, 65, 100

I have been using a throttle curve of: 80, 78, 70, 78, 80. Which is unchanged, and I guess it shouldn't matter. The pitch curve should be independent of the throttle curve I hope.

 

[Smoggie]

The 'expo' you see in the pitch and throttle curve is something different to expo in aileron/elevator and rudder. All the expo does on the pitch and throttle curve is make the curve a smooth curved line between the point you set. Without Expo the 'curve' is just a series of straight lines between the set points. Expo on throttle or pitch curve wont really help you to be honest.

I find that the best way to make a heli easier to control on collective pitch is to use a governor to keep the head speed constant at all times. Pretty much all heli ESC's have governor function. Once you enable governor in the ESC then all you do is set the throttle curve to be a flat line, usually in the range of 70-85%, depending on what head speed you want (expo is then irrelevant because the 'curve' is straight). To start and stop the motor you use throttle hold.

If for some reason you dont want to use governor then the objective is still the same, you want rotor RPM to be constant so the throttle curve should be close to flat line. Governor just makes it a lot easier and better.

To adjust the responsiveness to collective it's the pitch curve you need to adjust. The general rule is a more gradually sloped pitch curve will give softer response, a steeper curve gives snappier response. Don't make the slope of the curve too flat though or the heli will became very sluggish.