When the blades of RC helicopters rotate, the body wants to spin in the opposite direction. This force is called torque. To counteract it, you produce sideways thrust with a second rotor on the tail. RC Electric Helicopters may have either a clockwise or counter-clockwise rotating main blade. Depending on this, the tail rotor will be set either on the right or the left.
To control RC Helicopters, both rotors must be adjustable. This is done via the controls on the transmitter, or Tx. This sends signals to the receiver, or Rx, located on the helicopter. This then sends electronic signals to the various components, which translate them into electronic inputs to various mechanical components – for example, the servos or speed regulator on the motor (ESC)
Fixed wing planes have airfoils. The main rotor blades of radio control helicopters are shaped like long, thin airfoils and they work the same way. Increasing or decreasing the angle of attack - i.e. the amount of blade in contact with the air stream – will alter the speed the craft is moving by altering how it “slices” through the air. Lifting the blade increases the angle of attack, lowering it decreases it.
The swashplate varies the angle of attack via a system of linkages to the fly bar and main blade grips, and by servos that alter its plane. Altering the plane of the swashplate alters the tilt of the rotor disc, and thus the angle of attack of the blades. RC Helicopters will follow the path of least resistance, thus varying the angle of attack in different directions (by tilting the rotor disc) will cause the helicopter to follow that direction – this is the cyclic phenomenon.
To generate lift the angle of attack must be increased across the whole rotor disc – or the speed of the blades increased to such a point that lift is achieved independently of this. In collective pitch RC helicopters, lift is achieved by the entire swashplate moving upwards; this allows the angle of attack of the rotor blades to increase until the entire heli lifts off the ground.
In the air, collective and cyclic pitch can be employed together or independently. The tail rotor pitch can also be altered. RC helicopters with collective pitch and belt-driven tails are, as near as dammit, tiny models of the real thing. They are capable of practically anything.
With these electric helicopters, you have true mastery of the sky.