Beginner’s RC Heli Buyer’s Guide

Okay, so you’ve decided that you want to buy a cool RC heli. You’ve either decided to pass on a toy heli, or you already bought one and are ready for something more. You might be surprised to find that there are a good number of RTF (Ready-To-Fly) Helis available that only cost marginally more than a toy heli, and are much more capable, as well as repairable! First you’ll want to educate yourself on the various formats available to choose the one that’s best for you.

 

Coaxial VS Tail Rotor

Conventional Tail Rotor Heli

Conventional Tail Rotor Heli

Coaxial Helicopter

Coaxial Helicopter

A helicopter uses rotating blades to provide lift. The speed at which they travel (throttle) and the angle at which they cut through the air (pitch) dictate how much thrust is produced. The problem is that the torque produced by the rotors would spin the body of the aircraft around if there weren’t a sideways thrust to compensate. A conventional heli uses a tail rotor to control yaw (the left/right spinning action). While this does produce a slight amount of sideways movement, on board electronics automatically compensate for this motion using a gyrometer, or gyro, for short. A gyro senses tilt using the acceleration of gravity and the on board computer compensates for this tilt by changing the pitch of the blades as they travel around in a circle.

But we’re getting way ahead of ourselves! We’ll talk more about the physics involved in later articles. Right now, we just want to choose a heli that suits us best.

 

A coaxial heli uses counter-rotating blades that both produce lift, but counteract the torque each one produces, since their motion is equal and opposite the other set of blades. While it looks somewhat unusual, this arrangement makes for a very stable helicopter without any built-in sideways thrust since it lacks a tail rotor. To spin around, all that needs to happen is for one set of blades to spin faster relative to the other blades.

 

So why aren’t all helicopters coaxial? Well, for one, they are generally heavier, as there are two sets of main blades, complete with propulsion, gear drives and two main shafts (usually a hollow shaft that contains a solid shaft within). Using a tail rotor keeps the heli lightweight and nimble, capable of unimaginable acrobatics! This is not to say that coaxial helis aren’t nimble, but they do have limitations. One of them is blade strike.

Blade strike occurs when one or both sets of counter-rotating blades is at full pitch, twisting and angling until they hit each other. Most coaxial RC helis have sufficient blade spacing that this will not occur unless you are a very advanced pilot indeed. And extended main shafts are often available to increase the heli’s capabilities as your skills improve.

 

Ok, so it’s fairly obvious that a beginner would be best suited with the stable flight characteristics of a coaxial heli. Some choose to go directly to a heli with a tail rotor design and have great success, as advances in electronics have enabled for much more stable flight. Particularly indoors, were there is little breeze apart from that coming from the rotors. So what else should the beginner pilot take into consideration when choosing their first heli?

 

NEXT: Number of Control Channels.

 


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