RC Aircraft Radio Control Systems Explained

Every radio control aircraft (nitro and electric) uses an electronic system to control its flight. This article will explain how radio systems work.

Radio Control System Components

The radio system is what is responsible for moving the control surfaces of the RC aircraft. The individual components vary among different systems, but here is a list of the basic components which are common to all radio systems:

• RC Aircraft Transmitter - The transmitter sends the radio waves which control the RC aircraft. When the pilot moves a stick on the transmitter, the transmitter emits a series of radio signals which control the RC aircraft.
• RC Aircraft Receiver - The receiver is a device mounted inside the RC aircraft, which intercepts the radio signals sent by the transmitter. It then decodes these signals and moves the different control surfaces of the aircraft by telling the servos how to move.
• RC Aircraft Servos - Servos are small electric motors which move the control surfaces of the RC aircraft. Each servo consists of an electric motor, several gears, and a plastic case. Servos are mounted inside the fuselage of the RC aircraft, and attached to the various control surfaces via push rods (linkages, usually made of a plastic, wood, or flexible nylon rod).
• RC Aircraft Battery - Both the transmitter and the receiver need a power source. Normally, NiMh (Nickel Metal Hydride) or NiCd (Nickel Cadmium) batteries are used. Newer radio systems use lithium polymer batteries due to the increased capacity. Make sure that both the transmitter and receiver batteries are fully charged before flying.
• RC Aircraft Crystals - The transmitter and receiver use a crystal, which determines the frequency that they operate on. Radio control aircraft are limited to the 72Mhz (72 million cycles per second) band, but there are various sub frequencies within this main band. As long as RC aircraft are operating on different frequencies, the can be flown together. Newer radio systems use a 2.4 gigahertz freqency. The transmitter and receiver scan for an unused band, and then lock to that frequency. This eliminates the need for frequency control, and also prevents crashes caused by two transmitters using the same frequency.

Radio Control Functions

Each radio system uses a number of channels to control its servos. The term channel can refer to either the frequency that the radio system operates on or the number of control functions available. Usually, the number of channels equals the number of servos. Here is a picture showing the different control functions on a typical RC transmitter.

• Red - Antenna . The antenna is the long telescopic wire at the top of the transmitter. The radio signal that controls the RC aircraft is sent over this wire.
• Green - Left Control Stick. The left control stick controls the rudder and throttle. Moving the left control stick upwards increases the throttle, and moving it downwards decreases the throttle.
• Likewise, moving this control stick to the left will move the rudder to the left. Moving it to the right has the opposite effect.
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• Yellow - Right Control Stick. The right control stick controls the elevator and ailerons. Moving it to the left will move the left aileron up and the right aileron downwards. This will result in a roll to the left. Exactly the opposite occurs when this control stick is moved to the right. Pulling the right control stick downwards will cause the elevator to move upwards, causing the pitch of the aircraft to increase. Pushing the right control stick downwards will cause the aircraft to pitch downwards.
• Purple - Power Switch. Use the power switch to turn the transmitter on or off.
• Left Blue - The left blue switch on this transmitter lets the pilot teach a student using a buddy box. When this switch is held down, the student has control of the RC aircraft. As soon as the instructor senses trouble, he / she can release this switch and take control.
• Right Blue - This switch controls an extra channel, for dropping payloads, controlling landing gear, etc.

Your radio transmitter will come with a manual that clearly describes all of these functions. Refer to it when installing your radio system in your RC model aircraft.

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