Pitch and throttle curves-
Ok, you just lightened your wallet on a brand new heli and it’s time to
set this bad boy up. Now, what kind of pitch curves are you going
to use? Lets assume that we are using a radio with five-point pitch
and throttle curves. If the fast talking salesman or Ultimate Combo
left you with a radio that only has three points, you will at least be
able to get a taste of flying to see if r/c helis are really your thing.
Then if you decide to stick with it, later on you are going to want a 8+
channel radio with 5+ points for the pitch and throttle curves.
Mechanical setup- Most helicopter instruction manuals tell you how to set the helicopter up for hovering and learning only. This means that the suggested ball link positions on the servo wheels, linkages, and pitch arms are optimized for a beginner, something probably about –1 to +9 degrees. This will work great for learning. Because the entire range of your transmitter stick only controls 10 degrees total travel, it will not be very sensitive. Also, with only –1 degree on the bottom you wont risk slamming your helicopter into terra firma quite as easily. But what happens when you get into forward flight and are ready for –5 to +10 degrees pitch? Now you will have to go back and mechanically set up the helicopter for your newly desired pitch range. These changes will throw off the settings in your radio too, forcing you to basically re-setup how the helicopter flies. As you get even better and are ready for –10 to +10 degrees, you will once again have to mechanically change the helicopter’s linkages yet again and re-setup your transmitter. This method works fine, it was how I taught myself to fly. One thing is for sure, you will become an expert at mechanically setting up your heli; which is not necessarily a bad thing, it is just more time consuming.
Now that I have been down this road, I realize that there is a far better way of setting up the helicopter. However, if you know you are totally clueless about r/c helicopters and radios, stick to the method described above. You will learn the most through experience and by discovering setup tricks and techniques for yourself. On the other hand if you have done a fair share of reading and think you have a pretty good idea what makes an r/c helicopter fly, you might want to go with method two.
Method two means that you set your helicopter up for full blown 3D the first time. Please note I am NOT saying you should go try to learn on a +10 to -10 setup!! Although the heli is ready for the full pitch range, you still adjust your transmitter for a beginners pitch curve. Then when it is time to change, all you need to do is adjust the percentage in the radio to what you want. As you progress, your heli will always be ready for more, and you will only need to make slight changes in your radio to change the way it flies. Having the heli setup for full 3D also allows for another advantage- your instructor can set up another model memory in your radio for aerobatics even though you might only have it setup for hovering. It can be a real confidence booster seeing someone else wring out your helicopter and then hand the transmitter back to you, assuring you that mechanically the heli is set up fine and you only need to make some tweaks to your radio setup to do what he just did.
To set the heli up for full 3d, first see what maximum pitch range your helicopter is capable of, (say 24 degrees for now), and split this in half, -12 and +12 degrees pitch. Our goal here is that at 0 degrees, all mixing arms, swashplate, servo arms, etc will all be in the center of their travel and at right angles to their linkages. 50% on your pitch curve should also be 0 degrees. 100% should be +12 degrees, and 0% should be –12 degrees. If this isn’t happening, figure out why and make the change now. Don’t use subtrim or ATV’s, do it the old fashioned way by trying a different arm or hole on the servo wheel. Say you can only get +/- 8 degrees, then a longer servo arm is in order on the pitch servo. Maybe 0 degrees pitch is not 50% on your pitch curve, see if the swashplate is in the center of its travel and if not adjust the long links to the mixers in the head. Our goal is symmetry between postitive and negative pitch. Later on we want 60% on the pitch curve to be the same amount of positive pitch as 40% is for negative pitch. Does this make sense? The bottom line is, do it right now so you won’t have to later.
Now that your helicopter is ready for 3D pitch curves, it’s time to consider the transmitter. By now you have probably heard the two schools of thought on what hovering point you can use. The two choices are half stick, and ¾ stick. Back in the old days when helis only flew upright, half stick was used, giving a nice broad pitch range that was not overly sensitive. The full range of the transmitter stick only controlled maybe 10 degrees of pitch. This worked great for hovering, but what about when people needed some negative pitch to do rolls? At first they just shoved this negative pitch into the bottom point on the pitch curve, giving them something that looked like –4, 0, 5, 7, 9. With this curve they were still hovering at half stick, yet it was possible to do rolls with the negative pitch. Now what happened when they wanted –9 to do an inverted climbout? –9, -2, 5, 7, 9 gave them that good old half stick upright hover, but look at how sensitive the negative portion of the stick was! It was time for something better, a fully symmetrical curve with zero degrees at half stick and a ¾ stick hover. It looks like this: -9, -5, 0, 5, 9. As you can see, unlike a beginner setup that controlled 10 degrees if pitch over the entire stick travel, we are now controlling 18 degrees or more, making it somewhat more sensitive but capable of a lot more in flight.
If you are new to helis and setting your heli up to learn on, once it is mechanically set up for full 3D, all you need to do is tone down the settings in the transmitter. Decide now where you want to hover (1/2 or ¾ stick) and using a pitch guage, make that point on your curve 5 degrees. The percentage is not important, all we care about is that each point has the correct pitch value at the blade. Now make the top point 9 degrees. Lastly, fill in the rest of the curve with something simple such as:
Sample beginner pitch curves. ½ stick hover: -1, +2, +5, +7, +9
¾ stick hover: -1, +1, +3, +5, +9
Keep in mind if you start with a ½ stick hover, you will have to relearn your hover position when you advance to linear pitch curves and a ¾ stick hover. Remember, when you are ready to move on to more advanced pitch curves, your heli will be ready. All you need to do is put a pitch guage on the blades and change the pitch curve percentages until you get the desired pitch range. No more adjusting linkages at the field!
so now you are getting pretty good at this flying egg beater and you want
your idle ups (stunt modes) to have a linear –9 to +9 degree pitch range
with a ¾ stick hover. Great, but what about normal mode (for
takeoff and landing)?
This is where I see a lot of creative solutions at the field. Some people still prefer a ½ stick hover in normal mode so they can bring it in and land it smoothly and easily. However, when they flip into stunt mode their pitch curves change drastically, causing the heli to jump. While they had 5 degrees of pitch in normal mode for that ½ stick hover, as soon as they flip into stunt mode they now have 0 degrees pitch at ½ stick, causing the heli to fall until they can correct with the stick. In the right hands, this switch can be done smoothly, but why make it so difficult? Why not just hover at ¾ stick in normal mode too?
This is exactly how I set up my helis and suggest that other people do it. By making all my pitch curves (normal, idle ups, hold) identical on the top half of the travel (0, +5, +9 degrees), I can flip into any mode while in a hover and nothing changes except the headspeed. The only difference in my pitch curves is that in idle ups I have –9, -5, 0, +5, +9 degrees, and in normal mode I have –5, -2.5, 0, +5, +9 degrees. The reason for less negative pitch in normal mode is so that when you are spooling up/down, your heli does not attempt to drive itself into the earth with so much negative pitch. It also allows you to make your throttle hold pitch curve the same as normal mode (-5, -2.5, 0, +5, +9) for practicing autos! While this curve looks like it will not give a linear feel, during an auto you will not feel this change since your heli is descending. You can practice your autos in normal mode and the throttle will come back up when you flare out. When you have an approach that looks good, throw the throttle hold switch and nothing changes except the throttle stays at idle. This is the secret to successfully learning to auto.
Normal mode pitch: -5, -2.5, 0, +5, +9
Idle up 1+2 pitch: -9, -5, 0, +5, +9
Throttle Hold pitch: -5, -2.5, 0, +5, +9*
*(You may want to increase for throttle hold)
One last piece of advice: Set up your helicopter with a low headspeed
in normal mode. This makes it easy to takeoff and land since the
heli will be a bit sluggish, AND, you won't attempt to go inverted in normal
mode since the low headspeed will be a constant reminder and a dead giveaway.
email me: jbond007 at lycos.com