Throttle and pitch curves tutorial

Normal mode with Pitch in blue and THR in pink, L stick is at 0, M is at 50 and H is at 100.

Hello again,

I know there are a ton of info on the web regarding this topic, but I will try to explain in a more beginner friendly manner.

Let me start with the assumption that you have a digital transmitter with the function that allows you to acces throttle and pitch curves, and that you mechanically did your swash and pitch to be on 0 at mid stick.

Ok, now to the theory part :)

As you might now, the simple 4 channels or even coaxial rc helicopters have the throttle on the stick and nothing more…Switching to the 6 or more channels heli, things change a bit, and let’s start with the name:

CCPM ?! if you wondered what this stands for, it translates to Collective/Cyclic Pitch Mixing and with this you can give both throttle input and also cyclic input in one transmitter channel…Nice… When I first bought my Esky Belt CPX, I remember somebody telling me that the best up-grade I can do to it is not metal rotor head, but a digital TX, boy he was right.

Now, you already know some basic things, which is good, and I will explain about these curves, but first:…

You must also understand that the 6 channel heli’s have at least 2 flight modes : Normal and Idle up mode (or sport, 3D etc…); some TX have more than 1 Idle up mode, for example my Walkera Devo 10 has 2 IDLE up modes first one for just simple flight, second one for full 3 d flight.

Normal mode is used most of the times for hovering and taking off/ landing most of the time, and Idle up is used for forward flight and 3d flight, meaning all kind of nice aerobatics that a heli can do over a plane.

It is important to understand the available flight modes, because based on this you will set-up the throttle and pitch curves for each of them.

Ok, enough info, let’s get to real business here…First, we will look on the normal mode since it is the place to start with, so to speak.

As you know there should be a minimum of 3 points for any throtthe or pitch curves, more high-end radios have 17 points or more, but we are not 3d world champs, yet :)

You need the lowest position of the throttle stick, usually named “L”, then the medium position, usually named “M” which is exactly at the mid-stick position, and the highest position of the stick named “H” where your motor is at maximum power output. You can define, exactly how much throttle you want for each of these three positions, and the transmitter will calculate the connecting points with a straight liniar line, so you don’t have to worry about it. Now depending on how you wish to have it , you might have 0% throttle at L, (for example in Genius CP heli, at 0 and no throttle subtrims to lower maximum position, the motor will start) or negative throttle value, using throttle subtrim which I recommend and is safer. Also for H position, I don’t recommend keeping it to 80-90% max, since the ESC will not like it too much, better option is to use a smaller motor pinion if your head speed is too high. It may seem complicated but it is actually simple and I hope it makes sense so far. You can find many examples on different THR curves, I am focusing on making you understand how things work. Ok, enough with throttle curve for normal mode, let’s talk about idle up. In IDL up mode the throttle curve is at 100% maximum values at each L or H stick position, and anywhere between 50 to 100% at mid stick. This means you have full power at the ends for fast lift and down speed, but a bit milder in the middle since this is the point where in IDL up the pitch curve is changing. You can understand how THR curve works better from below diagrams: 

IDL 1, with -3 deg pitch at L stick, 0 pitch at M and +11 at H stick. THR curve is pink with with 100% at L and H and 85% at M stick

IDL 2, with -11/+11 pitch at L/H stick, and 95% THR at midstick, usefull for hard 3D flight

 

Ok, now a quick summary: Normal mode, you have 0% or better -10% throttle on the L stick, and based on preference maybe 50% THR on M and 100% on H stick

For IDL up you have -100% on L stick, 50-100% on M and 100% on H stick

One more mention before moving on to Pitch curves, about governors. This is a nice feature that some ESC have, and by enabling this, you have constant head speed, kind of similar to a cruise control in your car…you set it up to a value, and the ESC will try keeping it to that(usually 100&) no matter what motor load you have.

Now, moving on to my favourite part: the pitch curves.

As you already know, on a 6 channel CCPM heli, by moving the throttle stick, you also change the blades pitch, that create lift, either positive or negative. A good way to observe the pitch changing is by UNPLUGGING your motor, or by setting up Throttle hold pitch curve to have -11 to +11 degrees pitch at L and H stick positions, and then you can safely observe the blades pitch change with throttle stick movement.

So, again, in the normal flight mode, I suggest having around -2 or -1 degrees pitch al L stick, enabling you to land even in stronger winds that will lift your helicopter, and slowly transition to 0 pitch at M stick, and finally +100% pitch at H stick. Many people don’t do this, and have +1/+2 positive at L stick, maybe 5 degrees at M stick and +11 degrees at H stick. Having this, when you switch to IDL up mode with the stick in M position the heli will jump down because of the pitch difference… I recommend that after M stick position, the pitch curves to be identical for Normal and IDL up flight modes like 50% - M and 100% H stick. An usual IDL up curve for 5 points transmitter would be 0%-L 25% 50%-M 75% 100%-H, meaning you have maximum negative at L stick, 0 at M stick and maximum positive at H stick.

If your transmitter has the pitch range from -100% to +100% then the -100% should be considered as you maximum negative pitch setting, 0 should be set for M stick and +100% should be the maximum pitch setting. The main difference for IDL up is that as you remember for maximum stick positions, L and H you have maximum throttle for the motor, also for the same L and H you should set-up to have maximum pitch to match with the throttle curve, enabling you for example to have enough lift for upside down flight. Personally, I have IDL up 1 where I only set-up -3 negative to +11 positive at both ends, this is allowing me to do nice forward flight and circuits, and -11 negative to +11 positive in IDL up 2 for upside down flying and hard 3d.

I really hope that it is all clear for you now, and it will help you understand how you can set up your own curves based on your own preference and liking.

Until next time happy flying and blue sky !