by cliff1066™

An RC helicopter has the main rotor above its fuselage, just like a real helicopter, which produces the main lifting force that makes the helicopter fly. It comprises of two or more rotor blades that extend out from a rotor head assembly. These rotor blades are shaped just like the airfoils on the aero plane wing, but are thinner, narrower and symmetrical on both sides. As these blades rotate through air, they force the air downward compressing the air, hence an equal and opposite reaction from the air lifts the helicopter up. Based on the configuration, the main rotor of the helicopter rotates at constant speeds which range from 1,500 RPM to 3,000 RPM. The amount of lift that is generated is determined by the pitch angle as well as the speed of each rotor blade as it cuts through the air. This angle is also referred to as angle of attack when rotors are in motion. Some of the older RC helicopters also use fixed pitch rotors, where the amount of lift generated by the blades is controlled through the speeding up or down of motor that rotates the rotor head assembly and thus the rotors. But this design makes the responsiveness of fixed pitch rotor helicopter much slower than others (RC HeliSite 2008).

In an RC helicopter, the main motor which rotates the rotor blades usually used two types of engines to achieve its purpose. The most commonly used are the nitro based engines, which use a combination of nitro-methane and methanol as fuel to generate energy though combustion which drives the motor.  The larger then engine size, the more power it can generate, hence, support larger size helicopters. However, most recently, electrical engines have also seen a significant rise in their popularity.

This is due to the fact that advancement in capacity and size of the batteries has allowed them to provide helicopter with longer flight times. While in the past, the motors were able to support only smaller indoor helicopters, electrical engines are now powerful enough to support large outdoor helicopters. These electrical engines are also preferred now because they are also much quieter than nitro engines (Cloe 2009).