Written by Andrew Griffith
Find the entire feature on page 26 in the October 2011 issue.
Read an abridged summary from the article.
NOT LONG AGO, RC helicopters were nothing more than a curiosity. There were only a handful of kits on the market and you practically had to be a mechanical engineer to put one together.
There might be one—or if you were lucky, two—helicopter pilots at a local flying field. Helicopter pilots would usually be left to themselves, subject to an array of whispered jokes such as, “Those things don’t fly; they are so ugly the ground repels them,” or “They don’t fly, they beat the air in to submission,” and others. Knowing looks were exchanged by the airplane pilots that said, “He’s a nice enough guy but he’s a little strange; he flies helicopters.”
Fast forward to today. At many flying fields, the helicopters present at a field can equal or even exceed the number of airplanes. Even if they are hidden in the back seat of their trucks, many of the sneering airplane pilots secretly own an electric helicopter or two.
Now there are so many kits available in nearly every imaginable shape and size that a beginner interested in getting started in the hobby can easily be overwhelmed. Offerings range from RTF helis that you can unpack, charge, and fly, to kits that you have to build from bags of parts.
Sizes range from diminutive electric-powered models that you can fly in your living room to turbine-powered scale masterpieces that require a trailer to transport them to the flying field. A first-time helicopter buyer is likely to encounter a confusing array of terms such as ARF, RTF, BNF, coaxial, fixed pitch, collective pitch, electric, nitro, and gas.
What this article is going to attempt to do is explain these terms and help the first-time helicopter buyer make an informed decision concerning which category best suits his or her needs and interests.
Size (abridged from article):Modern electric-powered helicopters are slightly more difficult to classify size wise, but they generally range from rotor spans in the 7-inch range (the tiny T-Rex 100) to the 700 size, spanning nearly 5½ feet. I’ve seen an electric-powered Scale helicopter with a main rotor span of slightly more than 90 inches!
Loose comparisons can be made to nitro-powered helicopters. A 550 electric is roughly the same size as a .30-size fuel-powered helicopter; a 600 electric is .50 size, and a 700 electric is .90 size. The 100 through 450-size smaller electrics have no mainstream fuel-powered equivalent.
Many factors go into deciding which size helicopter to purchase.
Flight Controls (abridged from article): Not unlike an airplane, a helicopter requires four primary flight controls: pitch (elevator), roll (aileron), yaw (rudder or tail rotor), and throttle. The elevator and ailerons are combined on the right stick (Mode 2) in what is called the cyclic control. This is what gives us directional control of the helicopter.
Rotor Head Designs (abridged from article): As mentioned, we generally have two types of main rotor head design: fixed pitch and collective pitch. The advantage of fixed pitch is that the design is simple so it’s inexpensive to produce.
As the name implies, the pitch angle of the main rotor blades is fixed and the amount of lift produced varies by changing rotor head’s rpm. In addition to the simplicity of the design, a fixed-pitch rotor head requires only one channel to control altitude.
The disadvantages of fixed pitch are that performance is somewhat limited, and if you get the rotor head too slow while descending, you might not get the rpm back in time to prevent impact with Mother Earth.
Tail control (abridged from article): Torque produced by the main rotor has to be counteracted or the heli’s fuselage will spin in the opposite direction of the main rotor. Typically this is accomplished by the addition of a tail rotor.
Like the main rotor system, the tail rotor can be either a fixed-pitch variable-speed design, or a fixed-speed variable-pitch design. Fixed-pitch tail rotor designs have a small motor mounted on the tail and the variable pitch ones drive the tail rotor from the main motor.
Fuel or electric power (abridged from article): The debate between fuel power and electric power has been going like the Energizer Bunny. The winner is … there’s no clear winner. Each has its own learning curves and unique support equipment to purchase.
In the case of fuel power, you need a fuel pump, glow plugs and a way to light them, and, of course, fuel. Then you have to learn to operate and tune an internal-combustion engine. Most fuel-powered helicopters use traditional model fuel (methanol, oil, and nitro methane), but there are two-stroke gasoline-powered engines available as well.
Several flights can be made on a single receiver battery charge so you can get a number of flights in while only stopping to refuel.
If you go with electric power, there are speed controllers, motors, and batteries to purchase. To fully explain how to properly choose your electrical system components such as the speed controller, electric motor, and batteries would encompass a small book.
Fortunately there are a number of packages available, supplied with components chosen from extensive flight testing, that are proven to work well together. Then you have to learn how to properly charge, and handle LiPo batteries.
Read the entire discussion about size, controls, design, and power on page 26 in the October 2011 issue.
Ready to take it to the next level? Read Mark Fadely's RC Helicopter Stunts article also found on page 107 in the October 2011 issue.