Saturday, August 13, 2011

Helicopters: Controls

Know your heli controls

By Lood Birk

Ermelo Radio Flyers

This is quite a strange article to write about and I know that most of you will probably laugh to think that I am writing an article about what happens on the heli when you give certain control inputs on the transmitter. Yet, many of the new guys that buy their first heli either don’t read the manual of the heli or they don’t understand what they read, so I still end up having to explain just what happens when you move the stick forward. A couple of years ago, I wrote something similar for a kid who lived far from “heli help” and it aided him to no end, so I decided to do this for everybody else out there.

For this article, I am going to use a standard variable pitch chopper. If you are starting with a coaxial chopper, don’t worry, the principles are exactly the same except that instead of pitch you will talk about rotor speed to make your heli rise. I am also using a mode 2 radio as example as most heli pilots flies mode two. To understand what is meant by mode, read my article on transmitter modes.

On your transmitter you will find two control sticks, also sometimes called gimbals. There is a left hand one and a right hand one. By moving each stick in either a horizontal or a vertical direction, something specific will move on your heli’s control surfaces. It is these interactions that you need to know before you attempt to fly your heli. If you don’t know them your road to flying your heli is going to be a bumpy one.

First let’s look at the different controls that is required to make a heli fly. You need cyclic, pitch and throttle and lastly rudder control. Cyclic is the control that makes your heli tilt forward and backward as well as rolling it from left to right.

Pitch and throttle control is based in two places. Throttle is either on your engine’s carburetor or the ESC in the case of an electric heli.

Pitch is the tilting of the main rotor blades to produce more or less lift as you move the stick.

Rudder control is when you move the tail of your heli left and right and is better known as yaw.

I am now going to look at them individually, starting with the cyclic. As I said the cyclic controls the forward backward and roll of the heli. Take your transmitter and look at the right hand stick. You will notice that the stick can move in a forward/backwards movement as well as a left/right movement. If you move the stick forward, you will notice the swash plate move forward and the heli’s nose will tilt down. Move the stick backwards and the swash plate moves backwards and your heli’s nose will move upwards.

Move your stick to the left. Here you will notice that the swash plate tilts to the left and the heli will roll to the left. Move the stick to the right and the swash plate will tilt right and the heli will roll to the right. Moving your cyclic does not cause the heli to climb or descend. Below is a snapshot I took from a heli manual.

Moving over to the left hand stick. This stick controls two different parts of the heli, so a bit more thought has to go into what you do there.

Let us look at the forward backward motion of the left hand stick first. The forward backward motion of the stick makes the swash plate move up (when pressed forward) and down (when pulled backwards). This will increase the pitch (stick forward) and decrease the pitch (stick backwards) of the main rotor blade. Increasing the pitch will make the heli climb and decreasing the pitch will make the heli descend. Blow is a picture I took from a heli manual as a visual reference.

Coupled with the pitch is your throttle. Now on the throttle side you do not have to worry to much, because it is directly linked to the pitch of the chopper and it will increase or decrease as you increase or decrease the pitch on the main rotor blade. It does require some fancy setup on your radio, but you don’t have to worry about it at this stage.

Lastly we look at the left/right movement of the left stick. The left/right movement does not move anything in the heli’s rotor head. Instead you have to look towards the back of the heli at the rudder. The rudder controls the yaw of the heli. Yaw is when the tail of the heli moves from side to side. When you fly, however, you DON’T look at the tail, you look at the nose of the chopper. It is just easier this way. So, if you move the left hand stick to the left, the nose of the chopper will yaw left. If you move the left hand stick to the right, the chopper’s nose will yaw right. Once again, I include the picture from my heli manual for you.

Flying your heli is an action of continuously giving input on both sticks and in all four directions per stick. You can probably see now that knowing which stick input controls what helps you to understand the control inputs necessary to keep your chopper airborne.

Happy Landings.

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