Radio Control System For RC Helicopter


by: Jen Chan

The Transmitter – Transmitter is nothing but the unit you hold in hand and operate the RC helicopter. The modern day transmitters come with in-built LCD screens and programmable memory for better user experience.

The Receiver – A receiver receives the signal from the transmitter and controls your RC model based on the inputs. The system consists of a battery and a converter to convert radio signals to electric signals.

The Servos – The electrical signals received by the receiver needs to be converted into mechanical movements and this task is done by the Servos.

The Receiver Battery and Wiring Harness – the separate battery pack is not mandatory for small RC models as they use a voltage regulator and source power from the main battery. However for larger RC helicopter models, it is necessary to have a separate battery system to ensure longer flights and reliability.

Modes – Understanding Mode 1 And Mode 2

If you are new to flying RC helicopters, you will come across the terms ‘Mode 1’ and ‘Mode 2’ from time to time. It is necessary to understand this term because when you advance with RC helis, you will need sticking to either one.

Mode 1 – Mode 1 is the oldest systems out there, started with the Reed systems. The Mode 1 transmitters came with two buttons for each servo. If the first button drove the servo to front, the second button drove it backwards. The main drawback of Mode 1 is that it was nearly impossible to operate two servos with single hand as the servos are located on the opposite directions of the controller. Mode 1 is the most popular mode in most parts of the world except for the US where Mode 2 is more popular.

Mode 2 – Mode 2 has aileron and elevator on the right stick while throttle and rudder are on the left stick. Mode 2 is very popular in USA as these aircrafts are easy to operate. Almost every radio control unit you get in the US market comes with Mode 2 mode as long as you don’t specify otherwise.

Single Stick – The single stick combines all the features into a single joystick but the model is no longer very popular, being restricted to a few selected models.

Trimming of RC helicopters

Trim is nothing but a small adjustment to your RC Helicopter control to help it fly accurately. An RC helicopter is completely ‘in trim’ when it has minimal or almost no tendency rotate or turn in any direction. The helicopter does not pitch, roll or yaw, but is in stable flying condition and no control system is applied. If a RC helicopter is able to accurately balance itself with a properly installed leveled swash plate, the amount of trim required to keep the helicopter stable should be minimal.

Trim control on the helicopter can be found as digital trim or analog trim, depending on the type and complexity of the RC toy and comes as a switch or a slider by the side of the transmitter’s control stick. Unless you want to go for throttle, the helicopter should require ‘no trim’ position and the slider kept on its central position. However, if you want to go for throttle trim, it should be for consistent engine idle position and can be done on internal combustion motorized helicopters or is generally pulled down in RTF electric helicopters. The setting for such throttle trim totally depends on how the speed controller is designed. 

The benefit of a digital trim is that you don’t have to worry that it would accidently move when you are using the transmitter. This is not the case for analog trim, but the advantage of analog trim is that it is always visible, and can be changed quickly especially when you want a throttle trim, since you can quickly stop a running engine by shifting the trim to the bottom position.

Pitch trim and a hover trim is something new that you can find in some advanced transmitter which allows adjustment in trimming with a slight change on the mid stick, and you can alter the whole pitch rage by moving it slightly down or up.

Trimming your RC helicopter mechanically is always considered best compared to electronic trim. Adjusting your trim through the linkages is always best before you use the radio, as too much of electronic trim may put a restriction on the travel servomotor. 

Flying range and time

If you have a RC Helicopter, the first thing that you should know is its range capability, so that every time you fly, you know what to do. Checking the range of your helicopter is extremely important when you fly outside, where there is a possibility that the helicopter can go farther from you compared to indoor flying.

To understand the rage of a RC heli, we here will take the example of a standard controller that is given with any beginner coaxial or with few FP helicopters. With the help of your controller you need to totally collapse the antenna to full reduced position. Now, you can plug in or turn on your heli and move away from it to a distance of 100ft. If you are testing your heli indoors, then it is suggested that you move away as much as you can.

If you have a coaxial heli, increase the throttle to its full or 15%, and then slowly accelerate the forward stick until you see the trail propeller begins to slowing spin. If you notice that the tail rotor or the main rotor is not spinning, you can be certain that you have a range problem.

In the case of a 2.4GHz radio heli like a Spektrum, you need to put your heli 100 ft away and then with the help of the range check screen you need to follow the manual instructions to check the accurate range capability. 

Channels – Know Everything About Channels 

Channels are nothing but the frequency used to operate the RC helicopters. Radio control systems work with frequencies and each frequency is assigned to a task.

2 channels – this is the very basic radio control system that you will find in RC toy grade helicopters and comes with two simple functions: while one channel controls the speed of main rotor, the second channel controls the tail rotor for navigation and speed control. The 2 channel system is a standard part of toy RCs and is shipped along.

3 channels – the only difference of a 3 channel system to that of a 2 channel is one additional channel installed for operating the secondary blade. 

4 channel – from the 4 channel systems, things start getting serious. In a 4 channel system, one channel is allotted to control the main rotor. The second channel controls the left and right movement, third channel for the forward and backward movement and the fourth channel for controlling the left and right movement. Unlike 3 channel, the 4 channel does not use a tail rotor to control its forward and backward movement, but it uses small motors (servos) to control the specific angle of bottom rotors of the helicopter. Tilting the rotor front or back moves the heli accordingly, and tilting them to the either side makes the heli lean to its specific motion. This is known as aileron. The combination of aileron with front and back movements can help the heli to move diagonally towards the right or the left. The 4 channel system gives the helicopter more agility when compared to a 3 channel control.

Then there are more complex systems such as 5, 6 and even multi channel radio control systems!


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