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With the advent of lightweight lithium polymer batteries and powerful yet tiny motors, the genre of mini remote control model helicopters is available for a cheap price (as low as $25). They can be found in mall kiosks, Radio Shack, Best Buy, and similar electronics stores, as well as toy stores and many other outlets. However, the cheapest stuff may not be ideal for you. This guide will explain all the buzzwords, and what to look for when it comes to buying such RC helicopters.

imagePro-hobby RC Heli Sizes

Pro-hobby RC helis generally are classified by either blade length or engine size.

For example, for pro-hobby electric RC helis, you will often see the word "450 class" or "450 size." That means the rotor blade is roughly 450 milimeters (mm) in length, for a diameter of roughly 10cm including mounting points and axes. Similarly, a 700 class or size would use main blade length of 700 mm. The actual main blade size can vary slightly due to different blade tip designs.

For the pro-hobby grade helis with glow (i.e. nitro) engines (see "Classify by Engine") the size class is based on the engine displacement (i.e. how big are the cylinders). These engines are tiny. For example, a "class 30" nitro engine would have a displacement of 0.3 CI, or 0.3 cubic inches. Nitro engines can go up to 90 (0.9 cubic inches). They do not correspond directly to main blade size, but here's a rough translation table (it can and often do vary).

Here's the WLToys V922 next to a can of 12 oz Pepsi... Yes, it's that small, and yes, it's a full 6 CH bird. | Source Types of RC Helicopters
There are three ways to classify RC helicopters: engine, size, and sophistication.

Classify by Engine

There are four types of power used in RC helis: battery, nitro, gas, and turbine.

Battery Power: The vast majority of RC helis are powered by rechargeable battery. Recent advances in lithium polymer batteries allow an impressive amount of power to be stored in a lightweight package, and RC heli makers made use of them to deliver many minutes of flight time in such a tiny package. More sophisticated battery powered helis (mini or midsize) can use replaceable battery packs (keep a couple charged ones around!)

Nitro Engine: For longer flight duration, a nitro engine is needed. Sometimes known as a "glow engine," this type of engine is closer to diesel in that it does not use a spark plug, but uses a mixture of methanol, nitro-methane, and oil. Fuel is expensive though. These engines run at extremely high RPM, up to 17000 and makes a very piercing screech when powered up. Some people call these "gas engines," which is not correct.

Gas Engine: Some larger RC helis use a tiny 2-cycle gasoline engine. These don't generate as much noise as the nitro engines. Gasoline is available almost anywhere and you just need some 2-cycle engine oil to go with it. On the other hand, they are pretty big for RC helis, and generally only appear on full- and large-sized helis (see below on size classifications).

Turbine Engine: For the ultimate in realism, you can't beat a miniature turbine engine. These are extremely expensive, though the power they can generate with such a small engine is truly amazing (that's why they are used in real helicopters!) Parts are hard to come by.

Classify by Size

As you can see from the starting picture, the size of the RC helicopter (its "scale") can vary greatly, from a little 8-inch micro heli (eSky Blade mCX 300) to a 60-inches (5 ft!) Bergen Intrepid. They are generally grouped into five classes.

Micro—This is your typical "toy" RC heli found in Brookstone and Radio Shack. It is about 6-12 inches total, and it fits in the palm of your hand, battery powered. The majority of the RC helis will be in this size category. Prices range from $15 - 125 depending on the level of sophistication and flight time (about 3-8 minutes on a full charge). Electric-wise, this is like 100 to 150 class.

Mini—From 12-24 inches in length, this model appears at a discount in some hobby and toy stores. Most are battery powered, though a more sophisticated version may use the smallest nitro engine available. Cost is between $30-300. This would be 200-350 class.

Midsize—From 24-48 inches in length, this is what the sophisticated RC heli flyers use to achieve those incredible aerobatic maneuvers such as upside down and barrel roll. They usually come with 6-channel control and are very often nitro-fueled instead of battery-fueled. Going by electric size this is 400-550 class. Nitro is probably class 30-60.

Full Size—From 48 to 60 inches in length, these are not adversely affected by wind and Wide Angle Camera can easily fly outdoors. In fact, they are so large that you should NOT even try to fly them indoors (the exhaust fumes from the engines can be a problem). Their mass make them quite stable. This is the 600-700 class (or class 90 if you go by nitro engine size).

Large Size—Longer than 60 inches in length (the size of a child) these models can easily reach an actual (not scale) speed of over 100 MPH and can easily be considered "drones." These can be powered by gas, nitro, or even miniature turbines. These are for very serious hobby flyers and usually require some serious assembly.

Classify by Sophistication

In general, the more sophisticated the heli, the more control channels it has, but usually this is accompanied by increase in size. However, recent miniaturization allow the creation of four-channel helis in 8-inch sizes.

There are three classes of RC helicopters by sophistication: toys, amateur flight, and pro flight.

Toys are the stuff you usually find in electronics and gadget stores, like Best Buy or Brookstone. They run between $25-75. They generally have 2-, 3-, or 3.5-channel control and the latest generation have "gyro stabilization." The heli itself fits in the palm of your hand. Typically these RC choppers have a flight time of 3-8 minutes.

Amateur flight RC helis are usually a bit bigger, from 12-18 inches in length or larger, and have full 4 channel controls, and supports longer flight time and higher speeds. These helis costs from $50-150, though some manufacturers are now making micro-sized 6-channel birds.

Pro flight RC helis are true helicopter miniatures with the ability to change blade pitch (thus using six control channels and often nitro, gas, or even miniature turbine engines). They are capable of inverted flight and full acrobatics. These cost from $150 to $1000.

Please note that size itself, while a general indicator, is not a complete indicator of whether it is a toy or not. The WLToys V922 is a micro flybar-less RC heli that is merely 10 inches long. At first glance, it appears no different from a $15-30 toy RC heli sold in a toy store, but the V922 is a full-fledged 6-channel RC heli. It costs about $100 and uses 2.4 GHz spread-spectrum technology (with plenty of available replacement parts should you break a few things) and is fully capable of inverted flight and other aerobatics. On the other hand, you can get a 3.5-channel toy heli in 26-inch size that simply dwarfs even some 6-channel birds.

Nitro Class Nitro Size Rotor Size Electric Class

30 0.3 CI 500-550 mm 500

50 0.5 CI 600-650 mm 600

60 0.6 CI 650-700 mm 650

90 0.9 CI 700 mm 700
Rough equivalency table of RC heli nitro engine class, displacement, size, and equivalent electric RC heli size class Category 1: Toy RC Helis
Toy RC Helis comes in three types: 2-channel, 3-channel, and the latest variant, 3.5 channel. A 3-channel heli has speed control, gyro stabilization, and other features.

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