Futaba 9CHP question

[paulw1283]

I have a few questions about the helicopter radio that I will ask in this thread. My radio is the Futaba 9CHP Super and I only started to explore its functions recently.

I have a question regarding the throttle curve and the pitch curve. I understand that the curves shows the relationship between the stick position and the "throttle" and "pitch" respectively. But all I see is a curve, no numbers or values. It's easy to see the stick position on the curve and that's the X-axis, and there is also a vertical line that moves along the X-axis that correspond with the stick when you move it. That way, I know the left end of the X-axis (origin) correspond to the low stick end, and the rightest end of the X-axis correspond with the upper end of the stick position.

But what about the Y-axis? There are no values or anything. If I was looking at a pitch curve, how do I know the pitch value (in DEGREES). The position on the pitch curve is meaningless unless I know what the end point values are. I need to know the pitch that the bottom Y-axis (origin) correspond to, and the pitch the upper Y-axis correspond to (in degrees). I also need to assume the relationship is linear. So if the bottom of the curve correspond to -3 degree, and the upper most of the curve correspond to +10 degree, then I'll assume the mid point is +3.5 degree, IF it's linear, which I'm not sure. Is it?

And how do I know the values that the bottom and top of the Y-axis correspond to? In my example I used -3 and +10, but on the radio there are no numbers. Where do I find this information? Does it have anything to do with servo endpoints?

A little confused.

Thanks.

[Motions]

The only way to find your pitch is by putting a pitch gauge on the blades. There is absolutely no way your radio is going to magically tell you what the pitch is at a given stick input. Every setup is different. Once you use a pitch gauge and know what your pitch setting are, you can use the radio settings as a "reference" from then on as long as nothing changes.

[paulw1283]

I'm not talking about the actual pitch. That I need to use a pitch gauge.

I'm more interested in knowing what the values of the Y axis mean (in a pitch curve or throttle curve) and the how to interpret it.

[MarkD]

The Y axis doesn't really have fixed values as such, they are dependent on how you have set the servos, throw, end points etc. ie on mine at mid stick the Y axis corresponds to 0deg pitch. Someone else may have there heli to hover at mid stick so the same point would correspond to 5-6degs on theirs

The same with the throttle curve there are no fixed values

Or another way of looking at it is if the servos were all set at default ie 100% ATV no sub trim etc then the bottom of the y axis would be min servo throw, middle - mid servo throw and at the top - max servo throw

[paulw1283]

Thanks Mark.

So basically the end points of the Y axis correspond to the end points of the servo travel that I set up?

Let me get this straight. Let's say I want to have -3 to +10 pitch range for my normal mode. I first set up the servo end point to restrict the pitch range to that. Then for that flight mode, the bottom of the y axis on the pitch curve should be -3 right? And the top should be 10? And the relationship is linear right? So the mid point should be +3.5?

And later if I want to have -10 and +10 for Idle up, then the mid point will be 0?

And the servo travel for each flight will be different. For the idle up, the servo will travel more in the negative direction (-10 vs -3).

I just want to get it straight. Correct me if I'm wrong.

[MarkD]

No - setup the servo(s) so that they give you max throw without binding using the servo's endpoints on the radio. I am assuming that you have already set the arm to 90deg to the linkage/servo at mid stick

If you run with 0deg at mid stick all servo arms, linkages, levers on the head should be parallel, this should be set mechanically.

When all the above has been set only then adjust the bottom pitch range by increasing point 1 on the pitch curve to give you -3deg, then point 2 to give a smooth curve to 0deg at mid stick. Then do the same to get 5-6deg at 3/4 stick and finally bring down point 5 to give you your +10deg

If you limit the pitch by adj the servo end points you will never go below -3 when switching to idle 1, 2

[paulw1283]

Ok, so let me get this straight.

First, I set the servo arm 90 degree to the linkage at mid stick. I setup the servos so they give me max throw in either direction without binding using the servo's endpoint on the radio.

If I run with 0 degree pitch at mid stick, the swashplate should be level and all the arms and linkage should be parallel and/or perpendicular. This is the mechanical setup.

At this point, assume I get -10 and +10 if the throttle curve is a straight line from point 1 all the way to 5.

But if I only want to have a minimum pitch of -3, I can just adjust the point 1 (or 2 if needed) on the radio so that the curve never come close to the origin (bottom of y axis, which is -10).

Then if I want more negative pitch on idle up, all I have to do is change the curve from the radio without even touching the mechanical setup.

Is that right?