If so it's generally used to make the control response 'softer' around the centre position so the plane doesn't feel so twitchy, yet still have full control throw available for when you want it.

Actually, that's a funny play on words. If one were to enter a negative number for exponential, then you could call it expedential, since output would be faster at stick center, so servo movement is sort of expedited. I like it!

And don't forget, whether or not you want negative or positive exponential depends on the brand of transmitter you are using. If Futaba or Tactic you want negative exponential, if Spectrum or JR you want positive to tame down throws at center stick.

"Exponential" or "expo" is a feature named after the "exponential function" in mathematics. Without going into too much detail, it's when a value starts by growing very slowly but then accelerates and spikes up quickly. This is what it looks like on a diagram:

Why is this important to RC modelers? Well, if you look at the curve above and imagine you have stick movement on the X-axis (horizontal) and servo movement on the Y-axis (vertical). You'll see that for the first half of the stick travel, you only move the servo maybe 10%. However past the mid point, you'll move the remaining 90% very quickly.

This gives you almost automatic dual rates. For small stick movements, you have very low rates but you have very high rates towards the extremes of the stick travel. If you fly e.g. 3D or aerobatics, this is crucial, as you need precision in your harriering, hovering and straight lines, but extreme rates in spins and tumbles. It also helps to take the "twitchiness" out of models.

Most modern radios allow you to set the degree of expo you want, ranging from a straight (linear) curve to very a aggressive exponential curve.

A negative exponent would be DIVIDING instead of multiplying. Thus it starts at a steep curve and then approaches a flat line. (which is why Futaba's notation is mathematically wrong)

"Exponential" or "expo" is a feature named after the "exponential function" in mathematics. Without going into too much detail, it's when a value starts by growing very slowly but then accelerates and spikes up quickly. This is what it looks like on a diagram:

Why is this important to RC modelers? Well, if you look at the curve above and imagine you have stick movement on the X-axis (horizontal) and servo movement on the Y-axis (vertical). You'll see that for the first half of the stick travel, you only move the servo maybe 10%. However past the mid point, you'll move the remaining 90% very quickly.

This gives you almost automatic dual rates. For small stick movements, you have very low rates but you have very high rates towards the extremes of the stick travel. If you fly e.g. 3D or aerobatics, this is crucial, as you need precision in your harriering, hovering and straight lines, but extreme rates in spins and tumbles. It also helps to take the "twitchiness" out of models.

Most modern radios allow you to set the degree of expo you want, ranging from a straight (linear) curve to very a aggressive exponential curve.

I hope this helps!

Uhhhh.....Thanks?

Lol! If anyone can come up with am easy way of describing expo, he/she deserves a prize!

Lol! No, I know what expo is so I didn't make it past the first sentence when the graph was involved and looked technical. I just wanted to have fun with the eternal struggle of explaining expo to beginners. I hoped the last sentence clarified that without insulting anyone, which apparently some other people feel the need to do. (Not you NJ)

What is the purpose of putting Expediential on your TX

Yup
Exponential is a little interesting to describe, perhaps the best way to learn how it works is to have a model set up with zero expo, fly it, then set it up with a reasonable amount of expo, and fly the same model again. The difference will be quickly apparent. On the other hand, some people like it, a few don't.

You will find it is much easier to do very small changes in rate of climb or dive, or do a little bit of "Wing Leveling" with expo set at perhaps 35% or so.

DennyV
Retired and the days are just too short, busier than ever!