Guide to Remote Control RC Model Helicopters: What Are 2, 3, 3.5, 4, and 6 Channel Helis? What Is a Gyro?
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.
Pro-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).
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 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.
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.
These RC Helis are almost always ready-to-fly (RTF) out of the box. Just put in some batteries, charge up the heli itself, and you can start flying. No assembly is required.
The 2-channel RC Helis
A 2-channel RC heli is no more than 6-8 inches long and will fit in your hand. They are only capable of:
- Up / Down
- Turn left / Turn right
Controls are Infra-red based, so you cannot fly them outdoors (the light will intefere with the controls). You also have to point the controller at the heli. Don't fly it around a corner or behind an obstruction. The range is limited to about 20-25 ft.
The primary remote control usually requires from six to eight AA batteries. There is a cable to charge the heli with has an on-off switch. Due to the size of the helicopter (and thus the battery) flight time is limited to from 3-5 minutes. Recharge time is 5-10 minutes. There may be flashing lights to indicate a full charge.
This sort of RC heli only has two controls: throttle (Z-axis up-down) and turn (i.e. left right). This version usually has two rotors: The main rotor on top, and a tail rotor that points to the side. (See example). Some models have two counter-rotating main rotors instead of just a single rotor, but both rotors are driven by the same motor.
This version can only fly up/down and turn left/right. The vertical Z-axis movement is controlled by varying the main rotor speed. The heli turns left/right by varying the tail rotor speed.
The helicopter body is slightly nose-heavy. This gives the heli a constant, slow, forward speed. You can adjust the speed slightly by adding a small bit of weight to the nose of the helicopter, but don't overdo it.
This sort of helicopter is designed as a disposable toy. Generally the rotors are plastic and the body is foam. If you crash it, expect it to break, especially if it falls from a great height.
As these are disposable, there are no replacement parts (though some Radio Shack models may have replacement main rotors available). With the advent of better chips, these have mostly gone extinct except "novelty" helis of unusual shapes or themes.
NOTE: Usually only one can fly in a room at a time, as the IR signals are not coded to specific "channels" and signals can get mixed up.
Pros: easy to handle, cheap to start ($15-30)
Cons: limited flight capabilities, cheaply built and easily broken, indoor only
Look for a cheap price, as these are disposable.
The 3-channel RC Helis
The 3-channel RC helis usually fits on your hand, no more than 6-8 inches long, almost same size as the 2-channel birds. Though some slightly larger ones can go 12 inches or even longer. They are capable of:
- Up / Down
- Turn left / turn right
- Forward / backward
Controls are Infra-red based, so you cannot fly them outdoors (the light will intefere with the controls). You also have to point the controller at the heli, and don't fly it around a corner or behind an obstruction. The range is limited to about 30 ft.
Usually, you have the primary remote control where you need to put in a lot of AA batteries (6 to 8). There's a cable you release from the remote to charge the heli which has a tiny port on the side with the on-off switch. The small ones have 3-5 minute flight time with a full charge. The larger ones may go up to 10 minutes.
The 3-channel RC helis offers variable forward speed by changing the rotor arrangement. They have two counter-rotating main rotors, one going clockwise and the other counter-clockwise, and controlled by two separate motors. There is a third rotor in the tail (controlled by a 3rd motor), but this one points upward rather than side-ways like the 2-channel birds.
The 3-channel RC helis have a bit more freedom of movement in that it now has variable forward speed, rather than the fixed speed of the 2-channel birds. The vertical rise and fall is still controlled by the main rotors. By adding/subtracting RPM to both main rotors together, the heli rises and falls. By adding RPM to only one rotor, the rotational inertia causes the heli body to spin in the opposite direction, thus allowing the heli to turn left or right. Finally, by spinning the tail rotor, the tail can be pulled up inducing forward motion (or pushed down, thus fly backwards). Each channel controlls one motor.
These helis look cool, are relatively nimble, but they cannot fly sideways and do tricks real helicopters can. At the edge of performance the helis are not stable. It is quite possible to make the tail rotor pull so hard it flipped the heli over and cause a crash.
Construction-wise, the cheaper birds are still made of plastic and foam body shell, though higher-quality ones are available with metal skeletons and variety of replacement parts. Look for the ones with replacement parts available, or already in the box. Rotors and such do get beat up.
The 3-channel birds are the current "standard" though they are rapidly replaced by the newer "3.5 channel" birds. You can find 3 channel birds for about $25 online, $40 retail.
NOTE: Some 3-channel birds may allow setting to different "control channels" so two birds can play in the same room. if you don't see this listed as a feature, assume they are "solitary", i.e. only one in each room.
Pros: still low cost, okay to handle
Cons: limited flight capabilities, not very stable at limit of performance, delicate and breakable
Look for: metal skeleton, replacement parts either already in the box or available for purchase
The 3.5-channel helis
The 3.5-channel RC helis are basically the same physically as the 3 channel birds. They usually fit in your hand, as they are no more than 6-8 inches long (some slightly larger ones can go up to 12-18 inches, like the 26-inch Double Horse).
Controls are usually Infra-red based, so you cannot fly them outdoors (the light will interfere with the controls). You also have to point the controller at the heli, and don't fly it around a corner or behind an obstruction. The range is limited to about 30 ft. Some of the bigger ones may use 2.4 GHz radio control and their large size would allow them to be fly outdoors, albeit still with range of about 50-75 ft. Some recent variants use WiFi control and register as a device on your WiFi network. This gives you even more range depending on your local WiFi environment.
Usually, the primary remote control requires six to eight AA batteries.. There's a cable you release from the remote to charge the heli with an on-off switch. The small ones have 3-5 minute flight time on a full charge. The larger ones may go up to 20 minutes. The latest ones may feature a microUSB port for charging and the big ones may even have swap-out battery packs.
Some recent models don't use regular remote control, but instead feature an IR transmitter that you plug into your smartphone and control with an app. However, this method is imprecise and not recommended.
Gyro / Stabilization / .5 channel
In response to concerns about unstable 3 channel birds, toy makers added tilt sensors or "gyros" (the same ones in your smartphones) to the birds' control logic which act as a dampener for the input. For example, the gyro senses that the chopper is already going nose-down at 30 degrees and any more would cause the heli to crash. It will stop any further tail rotor command to pull the tail up.
However, limiting the controls is frustrating to more experienced users, so manufacturers added two sets of parameters. In the "amateur," or low-speed mode, the controls are capped by the gyro at a lower level, thus limiting the amount of maneuverability you have. This, also lessens speed and potential damage. There is an option to switch to professional, or high-speed mode, which caps the controls at a higher level, giving the player higher maneuverability.
This available selection of high vs. low speed became known as the 0.5 channel, as a "feature" to make them better than the 3-channel birds.
NOTE: Some of the better 3.5 channel birds can be set to different control channels to allow more than one bird in the same room at the same time.
Some of the 3.5 channel birds may have special features like actually shooting little plastic missiles, or allowing two helis on different control channels to "dogfight" and "shoot" each other down. Onboard sensors register hits and the victim drops three feet and spins "out of control."
Pros: More maneuverability, more stability, often replacement parts are available for repairs.
Cons: Still not true helicopter flight, low flight time, more complex than ever.
Look for: Metal skeleton, replacement parts in the box or available for purchase, multiple channels so several people can play at once, and radio instead of infra-red control.
Category 2: Amateur RC Helis
Amateur RC Helis have four channels of control, allowing them to perform:
- Up / Down
- Turn left / Turn right
- Forward / Back
- Sideslip left / Sideslip right
There are two general ways to do this: the toy-grade, and the hobby grade.
Toy grade method to achieve four channel
Recent advances in battery and manufacturing have allowed toy makers to make four channel flyers cheaply by adding two side rotors (one on each side) to a 3-channel bird. However, this is just a kludge, as it is nowhere close to a real helicopter flight.
To fly sideways, you simply have the side motors do a differential thrust: One goes up, the other goes down, which pushes the whole thing one one, and vice versa.
The rest of the chopper is identical to the 3-channel birds. These are toy-grade helis with IR controls, and often with no replaceable parts. Once they break, that's it.
Hobby-Grade method to achieve four channel
Seeking to attract a more sophisticated audience who want a more realistic flight experience, some manufacturers have scaled up the model size. Typically, the hobby grade 4-channel birds are 18-24 inches in length with a single main rotor. (There are exceptions, like the E-Flite Blade series, which are only eight inches long) THESE ARE NOT TOYS. You can hurt someone if you crash it into them. Both the blades and the body can cut people. Don't fly these indoors unless it's a BIG space, like a gymnasium. They use 2.4 GHz radio control, and thus the range is up to 80 feet.
A real helicopter dynamically adjusts the "pitch" (or how much the blade cuts through the air) of the main rotor and uses that to control which way to fly. To fly forward, the blades adjust so the "rear half" of the rotor disc produces more lift (higher pitch) than the front. To fly to the left without turning, the "right half" of the rotor disc adjusts to have more lift than the left.
This sort of fine control is not possible with a 4-channel bird, as their main rotor is "fixed pitch," and does not change like a real helicopter. Instead, they have other tricks to allow them to achieve sideslip: Moving the rotor axis itself through a set of servos right on the main rotor. By tilting the main rotor slightly the bird can go forward or backward and sideslip left and right.
There is another type of 4-channel hobby bird, the co-axial type, with two main rotors that counter-rotate (one clockwise, the other counter-clockwise). These are very stable, as both rotors act as "gyros" to stablize the craft. But as a result, this model has a very different flight charactertistic than the fixed-pitch single-main-rotor 4 channel hobby birds, as they don't have a tail rotor.
These 4-channel birds are hobby grade and will cost anywhere from $50-200. However, they are carefully built pieces with all replaceable and upgradable parts. Servos, motors, rotors, gyros, antenna, even a battery pack. A good one is about $120.
Should you go this route, it would be wise to get a tool kit, a training gear landing skid, quite a few replacement parts, a extra battery and charger. Consider also a PC "trainer" where you practice flying on a PC before you try it with your hobby RC heli.
Pros: More maneuverability and lots of replacement parts are available for repairs
Cons: Four degrees of freedom means more training is needed. Still not full maneuverability.
Look for: Metal frame, metal rotor mechanism, 2.4 GHz radio frequency control, spectrum-spectrum anti-jam, gyro stabilization assistance, and available replacement parts
Category 3: Pro Hobby RC Helis
The "professional" Hobby RC helis features full 6-channel control, which means full 6-degrees of freedom. These helis costs up to $1,000 and is capable of full acrobatic maneuvers, including flying upside down, barrel rolls, and more. The high-end ones will be using nitro fuel instead of just regular batteries.
These 6-channel pro hobby birds emulate a real helicopter's rotor mechanism by allowing individual main rotor blades to change their pitch (pushing more or less air) as they rotate. The rotor mechanism is going to be far more complex than the toy models, but the result is far more maneuverability and true helicopter flight.
Older generations of the birds have an additional "flybar" to act as a balancer/gyro, though the latest generation does not have a flybar. Also, instead of a 2-bade main rotor, some 3-bladed designs have appeared, making them looking more and more like a real helicopter instead of just an approximation. You can see the eSky HoneyBee CT video below, which is a tri-blade, flybar-less design. It looks like a helicopter static model, not an RC heli, yet it flies.
The performance differences between a 4-channel and a 6-channel hobby heli are night and day. Watch above what a 6-channel bird can do. Keep in mind this is probably a $750 bird with customized parts, nitro-engine, and so on, but it's still a bird you can buy off the shelf. In this video, you'll witness this heli doing barrel rolls, switch between right-side up and upside down, loop, Immelman climb and dive, nose-up sideways flight, and much more. Watch, and be amazed.
The pro hobby 6-channel RC heli requires a bit of experience and is not something you should jump into right away. There are some RC helis on the market that can switch between 4- and 6-channel operations. Though I do recommend you visit Xheli.com, which has a lot of tutorial videos, tweaking and tuning tips, and such.
On the other hand, something like the V922 is fully capable of inverted flight and other aerobatic tricks, albeit at a much reduced "micro" scale when flown indoors.
There are plenty of design innovations worth investigating.
The first and the most famous is the AR Drone by Parrot. Sold through Sharper Image, it's usually controlled through an Android or iOS device with an app and onboard WiFi. It also has a camera onboard. The latest version, AR.Drone 2.0, has a 720p HD camera for an even better picture from aloft. You can fly it indoors with the "bumper" shell to protect the rotors, or fly it outdoors without to make it lighter. It is, of course, a bit expensive.
For those who think the AR.Drone is a bit too rich, there's now the WLToys V959 quad with a camera. This model is a cheaper and smaller version of the AR.Drone. The camera is not as good, and there's no transmitter as the camera records to a microSD card (you do get a reader). According to reviews, the camera is detachable, and you can buy extra items like a winch, plastic missiles, and even a tiny squirt gun for remote launches.
Quadcopters comes in various sizes, and they are very stable due to their quad-rotor nature. Their battery life could be better, however.
Rather than using toy-grade controllers that look like toys, some fancier manufacturers introduced control via WiFi and Smartphone IR module.
AR.Drone was the first to introduce WiFi control. Basically you pair your smartphone (Android or iPhone) WiFi to the AR Drone, which acts as a limited hotspot, and it will receive the control signals and send back video via the same channel. Your compatible app will sort it out. This control scheme was borrowed by some makers for their much simpler RC helis. The controllers are done via touch-screen pads on the smartphone.
Recently there's another variation that uses Bluetooth instead of WiFi, but it's the same idea.
Some makers, to distinguish themselves and look more hi-tech, tossed the dual-stick RC and include a tiny IR transmitter that plugs into the smartphone's earphone jack. The transmitter sends the control signal, but it is the same signal sent by the RC controller. You also run an app that sends the IR signals via onscreen control pads on the smartphone.
I don't like the smartphone controls, as they never quite feel right. There is not enough physical feedback from the controller if you go touchscreen. It just feels too gimmicky.
So what should you buy?
In general, I do not recommend buying any of the "toy" micro-sized RC helis, even if they are four channels. They are okay for indoor fun, maybe buzz the cat or dog for your amusement, but no more. Once they crash a few times, they are pretty much done for. The motors are not expected to last for too long, and battery with constant charging and discharging wears down quickly as well. If you do get one in this category, do not buy those drugstore specials. Buy the good ones with plenty of replacement parts. The WLToys V922 micro Heli mentioned before comes with several spare parts and has replaceable batteries (and rechargeable) for 15 minutes or more of flight time with one hour of charging.
For proper hobby flying you should get a "mini" or "mid-sized" 4-channel RC heli as your starter. You can learn how to fly with one of those properly, and transition later to a proper 6-channel RC heli. You will pay more to start, but with plenty of parts available, you can maintain and keep your heli running without buying a replacement every few months. It's recommended by most that you should get a 600 or 700 class heli for practice, as those can be easily flown both indoors and outdoors.
The best way to start, in my opinion, is to buy an eSky training kit for about $25. This gets you a USB RC controller replica so you can practice controlling an RC helicopter or aircraft and crash as much as you want. Once you're sure you can control such a beast, go ahead and buy the real thing.
In conclusion, I hope you have found this quick guide to RC helicopters helpful in reaching a decision about your purchases. Have fun out there.
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