How Fixed Pitch RC Helicopters Work
Every RC helicopter needs to control its direction and altitude. Most often, this is accomplished by changing the pitch of the rotor blades. This results in a change in airflow from the blades and causes the RC heli to move in the desired direction. By changing the pitch of the rotor blades, fine control can be achieved. RC helicopters can be built that eliminate the need for pitch control. Fixed pitch RC helicopters are a great way to start flying RC helicopters, because of their simple controls. In this article, how they work will be explained.
In order to understand how fixed pitch RC helicopters work, we will consider a fixed-wing aircraft. Airplanes fly because as air moves over the wings, a difference in air pressure between the top and bottom is created, causing lift. Increasing the lift we can be done in two ways. The velocity of the air moving over the wings can be increased, or the curve of the wing can be steepened. The rotors on an RC helicopter are like the wings on a plane, so the simplest way to increase lift is to make them spin faster. This will make the helicopter travel upwards. Likewise, when we want the helicopter to descend, the speed of the rotors is decreased.
RC Heli Design – Quad-Rotor
Several RC helicopters are built with four main rotors, mounted at a right angle to the aircraft. The quad rotor design allows four-channel control, without the complexity of variable pitch. A flight computer can read the input from a radio receiver and then change the speed of each motor so that the direction of the helicopter changes. This also allows automatic stabilization of the helicopter.
RC Heli Design – Conventional
The travel direction of a fixed pitch RC helicopter can be changed in two ways. If a rear rotor is included, which is mounted at a right angle to the fuselage (body of the helicopter), it can be used to push the nose of the helicopter in a certain direction.
RC Heli Design – Coaxial
Bladerunner Coaxial RC HelicopterTwo main rotors can be linked to separate motors. By spinning each rotor at a different rate, the yaw (direction) of the helicopter can be controlled. Each rotor can be placed on the same axial. The coaxial design reduces the size of the helicopter so that it can fly indoors. You can read more about coaxial helicopters. The fixed pitch coaxial design also frees an extra channel of control. If we don’t need the tail rotor to control the direction (yaw or pitch, depending on the application) of the RC helicopter, we can instead mount it in the same direction as the main rotor blades, allowing pitch control of the helicopter.