How a Remote Control Helicopter Works
RC Helicopters are one of the most versatile modes of transport available, giving the pilot full access to a completely three-dimensional space. For this reason, helicopters, whether RC or full-size, are one of the most difficult vehicles to learn.
- A train can travel in two directions: forward and backward.
- A car can drive in 4 directions: forward, backward, left and right.
- An airplane can travel in 5 directions: forward, left, right, up and down.
While a helicopter can travel in 6 directions: forward, backward, left, right, up and down. In addition, you can also rotate 360 ??degrees in any direction and do all of it while you are reversed.
In a traditional full-size helicopter, the pilot controls the cyclical with one hand and the collective with the other.
However, in an RC helicopter, it is not always considered as the helicopter, which makes it very difficult to maintain the orientation and to maintain control. I’ve even heard that full size helicopters say an RC helicopter is harder to fly, though in reality this is unlikely to be the case, but to stay aligned when the helicopter is extremely difficult to master.
How do RC helicopters fly?
How does an RC helicopter fly? Someone once said that he overcomes the air in submission, and in fact he somehow does it.
The RC helicopter flight can be divided into 5 basic components and their functions. The main rotor, the tail rotor, the oscillating plate assembly, the collective control and the cyclic control.
The main rotor
- A conventional RC helicopter has its main rotor on the fuselage (body) consisting of 2 or more rotor blades extending from a central rotor head or central rotor assembly.
- The main rotor of an RC helicopter is the one that generates the lifting power that makes the RC helicopter fly. The rotors of an RC helicopter have the shape of an airplane wing, only they are thinner, narrower and both sides are symmetrical.
- As the rotor blades spin through the air, they create buoyancy. The amount of lift generated is determined by the angle of inclination (and velocity) of each rotor blade as it moves through the air. The angle of inclination is called the angle of attack when the rotors are in motion.
- Some of the cheaper RC helicopter models that use fixed pitch rotors generate lift when accelerating or decelerating the engine, and therefore the speed of the main rotors. This results in a much slower responsiveness of the helicopter since some engine speed is needed to accelerate or decelerate. As far as I know, there are no real RC helicopters using a fixed pitch on the market, and they will not pick up at a flea market; There is a reason why they are no longer manufactured.
- Depending on how the RC helicopter is configured, the main rotors typically rotate at a constant head speed in the range of 1500 RPM to 3000 RPM. Larger RC helicopters .60 or .90 generally have a top speed of 1,500 rpm at 2,000 rpm, while smaller .30 or .50 helicopters may have a top speed in the range of 2,000 to 3,000 rpm.
- To increase the push or lift force, you only need to increase the pitch of the main rotor. In an RC helicopter, the joint angle (sound) can be between +15 degrees and -15 degrees, although most RC helicopters are somewhere in the range +11 to -11.
- The angles of inclination of the blades are controlled by the collective and cyclic controls transmitted to the main rotors by the oscillating plate.
The tail rotor
Since Newton’s law states that “for every force, there is an equal and opposite reaction force”, as soon as the RC helicopter leaves the ground, there is nothing to prevent the helicopter from turning in the opposite direction to the torsional force generated main rotors.
To stop the rotation of the body, a force must be applied that counteracts the force of the main rotors to stop it. In a single rotor RC helicopter, this is usually done by a smaller set of rotors attached to a long tail arm called a tail rotor, which is used to control the tilt or rotation of the helicopter.
The amount of thrust produced by the tail rotor is determined by its angle of attack.
Increasing the angle of attachment (tilt) of the tail rotor blade will increase the thrust, which will push the helicopter in the same direction as the main rotor blades, while decreasing the tilt will decrease the amount of thrust, allowing the force of natural torsion of the main rotors so that the helicopter turns in the opposite direction to the main rotors.
A gyroscope, either mechanical or piezoelectric, measures the difference in rotational force between the helicopter and the tail rotor and adjusts the pitch of the tail rotor accordingly to keep the RC heli stable.
The tail rotor is typically mounted at a 90 degree angle from the main rotor and provides a lateral thrust that counteracts the rotational force applied by the main rotors to keep it straight.
Depending on the gear ratios, the tail rotor typically rotates 3-6 times faster than the main rotor.
The tail rotors in RC helicopters are usually driven by a belt or torsion tube that shuts off the main gear that also drives the main rotor. In some cheaper models, a separate motor is used to feed the tail.
The set of Swash plates
The place of swash in an RC helicopter (or full size) is used to translate the commands of the pilots into the movement of the main rotor blades and / or flybar.
The oscillating plate assembly fits the main rotor shaft under the head of the heli and consists of a rotating disc and a non-rotating disc.
The lower non-rotating disk is directly connected to the cyclic and collective controls that are controlled by servos under the command of the inputs of the pilot transmitter.
This non-rotating disk is connected by a bearing to the second rotary disk, which rotates with the rotor and is connected to the pitch horns of the main rotor blade.
The oscillating plate can be made to tilt in any direction according to the cyclic controls, or up and down to change the inclination of the rotors under collective control, allowing the pilot to control the RC helicopter in a three-dimensional space.
Collective control raises the entire oscillating plate assembly as a unit. As the swashplate rises or falls, it changes the pitch (angle of attack) of all the rotor blades simultaneously and to the same degree. This is known as collective control.
Therefore, when collective control is increased, it will raise the entire oscillating plate assembly increasing the angle of attack. Increasing the angle of attack increases the elevation of the main rotor, causing the heli to gain altitude, while decreasing the angle of attack decreases the lift.
Since all blades are changing pitch together, the change in lift remains constant throughout each complete turn of the blades.
The cyclic control operates by tilting the oscillating plate up or down, and individually elevating the pitch of a rotor blade as it rotates so that the angle of attack on one side of the helicopter is greater than in the other.
As the angle of attack changes, the lift produced by each blade changes, and this unbalanced lift causes the helicopter to tilt to any side that experiences the lowest altitude.
This allows the helicopter to move in any direction around a 360-degree circle, including forward, backward, left, and right, or any combination of the 4.
For example, if the cyclic control on your transmitter is pushed forward, the vibration plate tilts forward and increases the angle of attack (and altitude) on the back of your helicopter, causing it to move forward.
The cyclic and collective pitch control of the main rotor blades and pitch attitude control allows the engine speed and thus the speed of the main rotor blades to be kept constant increasing the maneuverability response time.
Your radio transmitter handles all mixes and translations between cyclic and collective movement. All you have to do is think in which direction your helicopter should fly, not in angles of attack or tilting plates.