RC Helicopter Buyer's Guide
By R. Allen Gilliam
Recent technological improvements in batteries and motors have allowed a rapidly growing market for remote control (RC) helicopters. Liquid fueled RC helicopters have existed since at least the 1970's, but cost around US$1,000 putting them out of the reach of all but the most dedicated hobbyists. There are now several kinds of electric RC helicopters. Making an intelligent choice requires significant technological understanding. This page is my modest attempt to help.
The sellers of RC helicopters have an incentive to, for example, give the impression that they're all easy to fly, or fail to point out that the electric motors wear out fairly quickly. I make money from the ads on this page, but I have no monetary incentives to deceive you about RC helicopters. I was not paid to put up this page, nor do I sell helicopters.
Rotor: The rotating parts of a helicopter, including the main rotor or rotors, and the tail rotor.
Blade: A single projection out from the shaft which actually presses against the air.
Axis: The line around which something rotates like a wheel rotates on an axle.
RPM: Revolutions per minute. The speed at which something rotates.
Overcorrect: Moving the control sticks too far and/or for too long than is necessary to reverse an undesired movement of the helicopter. This is most often caused by pilots who wait to see the helicopter change its movement before returning the stick to the neutral position. Since there's a delay in response, you must end the correction before it takes effect. With experience you will learn how far to move the sticks and for how long in order to achieve the desired correction.
Pitch: Confusingly, this word has two definitions relevant to helicopters. (1) The angle that a rotor blade is tilted so it can press against the air as it rotates. (2) Rocking movement forward and backward, the nose goes down while the tail goes up, and vice versa.
Roll: Rocking movement from side to side.
Yaw: Rotation around the main rotor shaft as if the helicopter's body were a tire on an axle. In other words, rotation that makes the tail trace out a circle in a plane parallel to the ground.
Gyro: An electronic sensor that detects rotation of the helicopter's body around the rotor shaft (yaw), and automatically corrects for it. Gyro's are not perfect. The nose of the helicopter will still drift around, but gyros make it much more controllable. Smaller helicopters these days have solid state gyros built into their receivers. Larger helicopters have separate gyro modules.
Coaxial Helicopter: Coaxial refers to the two main rotors, one above the other, turning in opposite directions. The coaxial design keeps the helicopter level enough that it only drifts around slowly without needing much correction by the pilot. Coaxial helicopters can not roll over and crash spectacularly like single rotors. They often have poor yaw control because they must vary the speed of their two main rotors to control yaw. This takes longer than varying the speed of a small tail rotor, so the control is less responsive. Also, since the shaft of one rotor passes through the hollow shaft of the other, there's a lot of friction transferring energy between the rotors randomly. Inexpensive coaxial helicopters without gyros are constantly rotating all over the place and simply can't be precisely controlled no matter how much practice you put in.
Fixed pitch (FP) helicopter: The two blades of the main rotor are connected together at the center, so their pitch can only be changed together, one side reducing pitch and the other increasing it. This allows the helicopter to move parallel to the ground, but not straight up or down. Fixed pitch helicopters must change the RPM of their main rotors to go up or down. These helicopters are not able to fly up-side-down (inverted) nor do elaborate acrobatics.
Collective pitch (CP) helicopter: The two blades of the main rotor are not joined, so they can adjust their overall pitch to make the helicopter go up or down. Some collective pitch helicopters can fly inverted by completely reversing the pitch of their main rotor blades.
Swash plate: The round plate at the base of the rotor assembly that's tilted by the servos. It transfers this tilt to the rotating parts of the rotor mechanism.
Servo: An electronic, motorized box with a rotating arm used to move the swash plate or other control mechanisms. Servos are rated by their speed and force.
Simulator: An application for a personal computer that simulates specifically remote controlled, model aircraft for the purpose of practice. I use Flying Model Simulator (FMS). It's freeware.
2 channel coaxial: These are just toys. They fly slowly forward all the time. You control their height and their yaw (rotation around the vertical axis). They can't deal with even a slight breeze and will just blow away. They make a good gift for a child, but don't be surprised if it's broken by the end of the first day.
3 channel coaxial: Same as 2 channel, but with forward and backward movement. This is achieved by a small propeller with a vertical axis on the tail that can push up and down to lean the helicopter forward or backward. Because this propeller pushes up and down, it makes the whole helicopter move up and down as well as forward and back which must be corrected for. This makes them actually a bit more difficult to control than more complex helicopters. They can fight a slight breeze, but just barely. You'll still want to fly indoors almost exclusively. Their ability to stop and descend straight down allows them to be landed on small spots which can be a fun challenge. If you want to start out as inexpensively as possible, you might as well buy one of these since they're not much more expensive than 2 channel helicopters. Both 2 and 3 channel helicopters will allow you to learn to control altitude, and learn to reverse left and right when the helicopter is pointing toward you. Be aware though that the forward and backward behavior of these helicopters is very different from 4 channel and above helicopters. Also, the sticks are often different, with yaw and forward/backward being on the right stick. You'll have to unlearn having the yaw on the right stick if you move up to a 4 channel. Best to do that in a simulator.
4 channel coaxial: There is a significant jump up in cost for these helicopters because of their greater complexity. They have a swash plate controlled by 2 servos. This allows the pitch of the lower rotor blades to be varied as they rotate, just like a 4 channel single rotor. This allows lift to be shifted in any direction to lean the helicopter and produce forward, backward, left, and right movement. Some have gyros which solve the rotation problems of the coaxial design. They often have decorative, non-functional tail rotors like the one pictured here. 4 channel coaxials have a greater capacity to fight the wind, but they're still mainly indoor helicopters. They're about the same price as 4 channel single rotors, so it might be more cost effective to skip this easier-to-fly type as long as you're sure you want to learn to fly a single rotor. However, if all you ever want to do is fly slowly around your living room, and you're not willing to put in dozens of hours of practice, a 4 channel coaxial may be a good choice for you. They can't fly very fast because the coaxial design makes the helicopter fight to stay level. Even a large coaxial can only go about 6 feet per second, about 4mph. The 4 channels do allow precise enough control to land on small spots which can be a fun challenge. Be aware that serious RC hobbyists don't consider coaxial helicopters to be "real" helicopters because they're so much easier to fly than single rotors. If you take one to an RC field, don't expect anyone to be impressed by your flying skills.
4 channel, fixed pitch, single rotor: There's a big jump up in difficulty with these helicopters. You simply won't be able to keep one in the air for more than a few seconds until you put in many hours of practice. If you try to fly one with no experience, you'll almost certainly have a damaging crash before you can completely learn to fly it. In exchange for this difficulty, these helicopters are fast and maneuverable. They can fly circles around 4 channel coaxials. They can lean way over and absolutely hurtle around. They can also fight the wind quite well, even the tiny palm-sized ones. It's best to spend enough time, perhaps 30 hours on average, flying a 4 channel RC helicopter in a simulator to learn to keep it in the air before you even buy a real helicopter. You may find that you're not as keen on getting one after seeing how difficult they are just to keep in the air.
6 channel and above, collective pitch, single rotor: These are serious machines. People spend years learning how to do amazing acrobatics. It's easy to find impressive videos on YouTube. They're significantly more expensive than 4 channel helicopters because of the added complexity of the collective pitch rotor, and the usually much more powerful motor. The up and down movement is controlled by a collective pitch channel which replaces the throttle on the left stick. The fifth channel controls the throttle (the RPM of the rotor) so it can be slowed for landing or to save power, and stopped when you're done flying. The sixth channel allows the gyro to be adjusted in flight. Many 6 channel helicopters can fly inverted by completely reversing the pitch of their main rotor blades. Many are electric these days, but the largest are powered by liquid fuel, piston engines burning nitro methanol fuel.
There are many videos on YouTube.com showing people flying various kinds of RC helicopters. They can give you an idea of the speed and maneuverability of the various types and specific models. But be aware that many of the videos show pilots with hundreds of hours of practice demonstrating their hard-won skills. Pay attention to whether the video is a first-time flight or an experienced pilot. Professional promotional videos invariably use extremely skilled pilots to make it look easy and thereby increase sales. Also, pay particular attention to shots that show the transmitter and helicopter at the same time. Watch how frequently the control sticks need to be moved.
Paddle stabilizer bar vs. weighted stabilizer bar rotors: With both designs, the mass at the end of the bar produces a gyroscopic effect that resists leaning in any direction. When the helicopter leans, the stabilizer bar tries to stay in the same orientation and exerts force through linkages to change the pitch of the main rotors in the proper direction to compensate for the movement. This reduces how fast the helicopter can roll and pitch, but unlike coaxial helicopters, does not make the helicopter level itself automatically. It only gives the pilot more time to correct.
The advantage of the paddle bar rotor design is that the paddles amplify the force exerted by the servos to control the pitch of the main blades. If you look carefully at the rotor, you can see that the servos change the pitch of the paddles, and they in turn catch the air, rock to one side or the other, and change the pitch of the main blades. This allows the servos to be smaller and lighter, and that reduces cost and increases flight time. Paddle bar helicopters tend to be more maneuverable because they can pitch their blades more. However, this isn't necessarily a good thing for inexperienced pilots because it makes it easier to overcorrect. The bars that have only weights don't help the servos at all. They only stabilize the helicopter. If the servos are strong, a weighted bar helicopter could be just as maneuverable as one with a paddle bar, but I don't think that's usually the case. The weighted bar design may allow more precise control because there are fewer linkages between the servos and the blades.
So, a weighted bar helicopter will be able to hold its position more precisely. While a paddle bar helicopter will be able to lean over and accelerate more quickly. The top speed isn't affected, though a paddle bar helicopter will likely be able to change its direction more quickly.
Brushless vs. brushed motors: Brushed motors have carbon or metal contacts that rub on the rotating part of the motor to convey electricity. The brushes wear out after as little as 5 hours of flight, though there's a good deal of variation depending on the quality of the motor. New brushed motors cost around five dollars, are widely available, and are not difficult to install. If you're planning to fly your helicopter for more than a few months, it might make economic sense to invest in a helicopter with brushless motors. New pilots might not want to spend the extra money though since there's a good chance they'll crash badly enough to need a new helicopter before they wear out enough motors to break even on the extra cost. You can't just change the motors from brushed to brushless since they require different electrical power. You need a brushless receiver module or an extra driver board for brushless motors. It doesn't usually make economic sense to upgrade a brushed helicopter to brushless since such an upgrade costs about half as much as a whole new helicopter.
Variable pitch tail rotors: Rather than change the tail rotor's RPM, this kind of tail rotor uses a servo and linkages to change the pitch of the tail blades. This allows the tail rotor to be driven at a constant RPM by the main motor by shaft or belt. They are more expensive, but more responsive and require less maintenance since there's no second motor to wear out. I've only seen them on 6 channel helicopters.
Some helicopters have belt-driven tail rotors which are quieter and lighter.
The two types of radios can be identified by their antennas. The older FM radios have 5-foot-long, telescoping antennas, while the 2.4 Gigahertz (GHz) radios have little, 6-inch antennas that hinge at their base. The main advantage of the 2.4GHz radios is that they send coded, numerical signals which do not interfere with each other. FM radios have only a handful of channels. Two aircraft can't use the same channel at the same time. When buying an FM remote control, you must be aware of the radio regulations in your country. Generally you want 72MHz if you live in the United States and 35MHz for the rest of the world. Within each of these two bands there are several channels separated by small differences in frequency. The 2.5GHz radios must "bind" when they are turned on. During this process the two radios communicate with each other to decide on an unused code to use between them. First, you set the throttle stick and trim tab to minimum, set the yaw trim to center, and turn on the transmitter. Then you turn on the receiver, usually by connecting the battery in the helicopter. The lights on both radios stop flashing when binding is complete. Only one set of radios can be bound at one time, but it only takes a few seconds.
The stick assignments are designated Mode I or Mode II. Mode II is by far the most common and has the throttle and yaw on the left stick, and the pitch and roll on the right. Mode I reverses the sticks. Many transmitters can be easily switched. Be sure you get the mode you want if the remote can't be switched. Research the remote separately by model number or download the manual if the seller doesn't specify the mode.
The first thing to do is get an RC aircraft simulator for your computer. While it is possible to learn to fly a 4 channel helicopter without using a simulator, it really is a no-brainer. Flying Model Simulator (FMS) is free. All you need to buy is a US$15, USB, RC-style, dual joystick. This is a fraction of the cost of a 4 channel helicopter. It's impossible to learn to fly on a real helicopter without doing at least $15 worth of damage to it.
Most RC transmitters now have plugs that let them be connected to a computer for use with a simulator. However, since a new transmitter is at least US$59 while a dual joystick is US$15, I think it's a mistake to wear out your transmitter by using it with a simulator. The transmitter's variable resistors (potentiometers) that read the stick movements don't last forever. Also, a transmitter consumes batteries even when used with a computer. A USB joystick does not.
Don't be overconfident after learning to fly a helicopter on a simulator. The real thing is quite different. But a simulator can allow you to learn how to judge the orientation of the flying helicopter, learn how to take into account which way the helicopter is facing, and learn to separate right and left into two kinds of right and left: rotate right or left, and lean right or left. It takes practice to separate these concepts in your awareness of how the helicopter is moving. You'll see it rotating to the left and think, "Go right." and you'll mistakenly lean it right. You'll also find it difficult to do two different corrections simultaneously, say lean right and rotate left. When such situations come up, you'll be likely to get confused and crash. You can get past these problems in a simulator.
Before I got my first, 4-channel helicopter, the Walkera 4#3B, I practiced in the FMS simulator. I was able to keep the model of this specific helicopter hovering tail-in indefinitely in the simulator. With the real helicopter, after 30 minutes of in-air practice, I was able to keep it hovering tail-in within a 10-foot-wide area for 30 seconds or so at a time before I got into trouble and had to land (or crash land). It wasn't until after 200 minutes of practice that I was able to hover tail-in for the whole 10 minutes the battery lasts. This was due to a few differences between the simulator and the real helicopter: (1) A real RC helicopter tends to lean to its right because of the force exerted by the tail rotor. The FMS simulator doesn't show this, so you tend to try to level the real helicopter and this makes it move to its left. (2) Up and down control is more difficult than in the simulator. You need to make corrections every few seconds. Also, after a few seconds in the air, my helicopter seems to loose power and I have to increase power to maintain altitude. I guess this is due to the heating of the motor or electronics. At first, I kept flying up 3 feet and then coming down and hitting the ground. Also, since it's a fixed-pitch helicopter, there's a good deal of lag in up and down response. You have to make a correction and then wait 2 seconds or so to see it take effect. It's very easy to nearly hit the ceiling and then cut too much power and slam into the floor. You have to learn to anticipate this. If the helicopter is descending, you'll want to give it a brief strong increase in power, and then drop back to slightly more power than before. (3) It was more difficult to see the orientation of the rotor than in the simulator. I fixed this by adding strips of white labels to the tips of the rotors. It makes a big difference. (4) The helicopter behaves differently when close to the ground. The simulator doesn't show this at all. Within about a foot of the ground, the helicopter is considerably more difficult to control due to turbulence from the flow of air hitting the ground. Tentative new pilots often make the mistake of trying to hover too close to the ground in order to avoid a bad crash. This makes the helicopter seem far more difficult to fly. When taking off, quickly get it up to at least 2 feet. Also, the helicopter's lift increases as it gets near the ground. This allows it to hover and bounce along like a hovercraft. This is called ground effect. When landing, you need to cut power even more when the helicopter gets about 6 inches from the ground.
Once you learn in the simulator how to keep the helicopter under control with it's tail facing you (called the tail-in orientation) you can begin flying the real helicopter tail-in. Then you can learn the other orientations in the simulator. I truly can't stress enough the importance of learning the proper stick directions for different orientations in a simulator. A single mistaken, opposite control movement can send your expensive machine into a wall or the ground and break not only the easily replaced blades but more expensive and difficult to replace parts. And crash damage accumulates. You may crash a few times and think your helicopter can take it, but parts are getting fatigued and will eventually start breaking.
You may want to color the tips of the rotors white above and below to make a more visible circle. This will help you see the orientation, especially if you want to fly the helicopter far away from you outdoors. Do this with spray paint or add bit of light-colored tape or an adhesive label. Wrap the tape around the leading edge of the rotor so the air pressure will keep it on rather than peel it off. Whatever you add to the rotor, add the same amount to each end so you don't unbalance it.
Battery chemistry: Most RC helicopters now use lithium polymer (LiPo) batteries. The older nickel metal hydride (NiMH) batteries don't provide as much flying time because they have less power for any given weight.
Battery ratings: Batteries are rated by their voltage, total energy capacity, and their maximum rate of discharge. Voltage is the force pushing electricity through the wires. Current, measured in amps, is a measurement of how much electricity actually flows. The current depends on the voltage and the resistance of the load on the battery. Current (in amps) equals voltage (in volts) divided by resistance (in ohms). The capacity of a battery is listed in amp hours (Ah), or milliamp hours (mAh) which are 1/1000 of an amp hour. 1000mA equals 1 amp. A 400mAh battery will put out 400 milliamps for an hour. The time and current are inversely proportional. For example, a 400mAh battery will put out 200mA for 2 hours. The maximum current a battery can put out continuously without overheating, or having its voltage fall too much, is listed as a "C" value, for example "10C." Multiply the C number by the battery's capacity to get the maximum current. For example, a 10C, 400mAh battery can put out a maximum of 4000mA's (4 amps). A new battery will be safe to use in your helicopter if the voltage is the same, and the C value is at least as high as the original battery. Sometimes the voltage is stated as the number of cells in the battery. A LiPo cell is 3.7 volts. A NiMH cell is 1.2 volts.
A higher capacity battery (larger mAh rating) won't necessarily increase your flight time because it will weigh more. But it will reduce the maximum speed your helicopter can climb and therefore also its maximum horizontal speed. It's probably best to use only the same capacity batteries as the one that came with your helicopter.
As LiPo batteries age, their maximum current output drops. So batteries with greater current output capability will have longer working lifetimes. For example, if you use a 20C battery in a helicopter that needs only 10C, the helicopter will fly normally until the battery has lost more than half of its current output capability.
Extra batteries: Obviously, your initial flying time starting with all your batteries charged will last as long as you have batteries. After that, it gets complicated. Say your helicopter flies for 10 minutes on a charge and takes 30 minutes to recharge. With one battery and one charger, you can fly for 10m out of 40m. Since you can't charge both batteries at once, a second battery won't double your continuous flight time. If charging takes 3 times as long as flying, a second battery will only reduce recharge time by one third, allowing you to fly for 10m out of 30m. A third battery won't help at all unless you get a second charger. Two batteries and two chargers will let you fly for 20m out of 40m. To fly continuously, you would need 4 batteries and three chargers. This is why there are more expensive chargers that can charge several batteries at once. Flying continuously isn't necessarily possible, though. Your helicopter's motor may need to cool for a time after using up a battery charge. For example, my Walkera 4#3B must cool for 10 minutes after flying for 10 minutes. Read your helicopter's manual.
Many helicopter receivers have little screw adjustments. The extent or "ext" adjustment narrows or widens how far the servos move. Reducing the extent can help new pilots avoid overcorrecting. More experienced pilots will want maximum maneuvering power to change direction more quickly. If your receiver doesn't have an extent adjustment, you can achieve the same effect by changing which hole on the servo arms the linkages are attached to. The gyro adjustment, often labeled "sensitivity," changes how strongly the helicopter corrects its yaw. If the sensitivity is too high, the helicopter won't rotate as quickly when you move the stick, and/or its tail will constantly swing from side to side. If it's too low, the helicopter will yaw when you increase or decrease power. If you give the helicopter a tiny bit of power, the gyro will start responding to yaw. You can actually hold the helicopter in your hand and turn it and the tail rotor will spin to try to stop the movement. You can hear and feel changes to the sensitivity adjustment this way.
The paddle bar and paddles can easily get knocked out of adjustment. The paddles should be flat relative to each other, and they should be at the same angle as the swash plate as you look down the bar from the side of the helicopter. The paddles should also be the same distance from the rotor. The plastic part of the paddle is screwed onto the little brass collar, so don't try to rotate the paddle without loosening the collar. You'll just loosen the paddle on the collar and it'll go out of adjustment again as soon as you start flying. Some paddle bars have flat spots under the screws to keep everything aligned. With such bars, if the paddles are out of alignment, it's due to the plastic part of the paddle coming unscrewed a bit from the brass collar. It the paddles are too loose to stay aligned, they can be glued onto the brass collar. Unscrew them completely, put glue in the hole, screw them back on, and wipe away any extra glue. Plastic Welder epoxy is best. You could even file down a small flat spot in the threads to give the glue more grab, but I haven't tried this yet.
In palm-sized helicopters, there are lots of tiny screws in the rotor mechanism. When adjusting your helicopter, be careful not to strip them. It's very easy to strip the threads out of a 0.5mm hole in aluminum (a fairly soft metal) not to mention plastic or carbon fiber. Tighten the screws only enough to hold things in place. Don't use even half your full strength. Tighter is not better. If you need to take a screw completely out, be careful not to cross-thread it when you put it back in. Turn it counterclockwise until it clicks, then tighten it, putting very little pressure on it as you first thread it in. Periodically check the tightness of all the screws on your helicopter. If one falls out during flight, you'll never see it again, even indoors.
An adjustment often neglected is the spacing between the motor's gear and the main gear. The motor mount allows the motor to be moved toward and away from the gear. If there's too much space, the plastic main gear's teeth can get stripped off. If it's too tight, your flight time will be reduced, and you might even overheat the motor and burn it out.
Keeping an RC helicopter flying can be expensive. After 14 hours of flight over 31 days, I ordered US$56 worth of parts for my US$128 helicopter, including two new batteries. You can easily wear out US$10 worth of LiPo batteries per month.
When flying indoors, the tail rotor will collect hairs and get tangled up. This eventually causes the rotor to bind and yaw control becomes erratic. Use tweezers to pull the hairs out as necessary. Or be less of a slob than me and vacuum your house more than four times a year.
You'll want to get extra main rotor blades. I broke the tip off my first blade only four days after getting my first single rotor heli. They're not expensive. Some helicopters come with an extra set. Other than not crashing, the best way to avoid breaking a rotor blade is to kill the power completely before hitting anything. If you grind the rotor into the ground or an obstacle, it'll break. It also helps to avoid flying near anything with a sharp vertical edge such as chair legs that have a square cross section. A blade is far more likely to break crashing into a chair leg than a flat wall.
Both the main and tail rotor can be repaired with Super Glue, Plastic Welder epoxy (probably the best), PVC cement, or even cellophane (Scotch) tape, but that's probably not worth the work for most people. To glue a blade, tape it together on one side, unfold it, apply the glue, fold the blade flat again, and spread the extra glue flat along the blade. Once it dries, remove the tape and smear some glue on the tape side. Let PVC cement dry for three days before using the blade. Please note that repairing rotors can be dangerous. If the broken part comes loose in flight, it could pose a danger to your eyes. If you don't wear glasses like me, and if you have to fly close to yourself or others due to lack of space, you may want to forego repairing your rotors.
Once you start breaking rotor blades and repairing or replacing them, you'll run into rotor balance problems. If the rotor is unbalanced, the vibration confuses the gyro, the helicopter's yaw becomes unstable, and it becomes much more difficult to control. It's sad that many people, not understanding the problem, and not wanting to buy a new helicopter, simply give up on learning to fly when this happens. To balance the rotor without removing it from the helicopter and balancing it on some sort of thin edge, simply power-up the helicopter, hold it in your hand, and get the rotor spinning slowly. You'll be able to feel the vibration, and see it by looking at the center of the rotor. With a palm-sized helicopter, wrap a two inch piece of cellophane tape around the tip of one rotor. This will make the vibration noticeably better or worse. You can then add and remove tape to balance the rotors easily. A small amount of vibration is normal. You'll need proportionally more tape for larger helicopters.
If the tail boom of your heli breaks, you may be tempted to cut off the broken part and reassemble it. Don't. The length of the boom is critical for the gyro to control yaw. A shorter boom gives the tail rotor less leverage and messes everything up.
Several things can reduce flight time as a helicopter ages:
Worn bearings: Oiling the bearings with a light oil like 3-in-1 will extend their life. If you find that the bearings need oil to have normal flight time, then they're worn and will need to be replaced soon. There are 2 bearings on the motor and 2 on the rotor shaft. There's the swash plate bearing, and bearings in the tail and tail motor. Learn where they all are and take care of them. Oil can be placed precisely by putting a drop on a toothpick or using a small syringe. Rotate the toothpick between your fingers to keep the drop from falling before you want it to.
Loose or dirty battery connectors: A loose connector on the heli can cut your flight time and power in half. A loose connector on your charger can prevent the batteries from being fully charged. If it's a bladed plug, just bend the blades so they're twisted slightly relative to each other.
Damaged wires: Crashes and vibration can cause the threads of wire inside the insulation to break. This reduces power and flight time by increasing the wire's resistance. Eventually the power will cut in and out randomly. This most often happens to the wires leading to the battery because the heavy battery can fly out during a crash and yank the wires. A wire with most of the threads broken inside the insulation will waste power as heat and require a higher voltage from the battery to climb. The helicopter may loose the ability to climb when the battery still has half its charge remaining. Plugs can be rewired, just push the metal parts out of the plastic housing and solder on new wires. There's usually a little tab that can be pressed in with a tiny screwdriver or needle to release the metal part from the plastic.
If you've made repairs to the frame and blades of your heli with glue, the extra weight can of course reduce flight time.
Poorly adjusted paddles: If the paddles are not parallel to each other, they can actually push the heli down.
If you're good with a soldering iron, you can increase power and flight time by replacing any plugs with soldered connections. I removed the plug between my speed controller and motor, shortened the wires, and soldered them. This tripled my flight time with older batteries and doubled my climbing speed. Be careful to use as little solder as possible (it's heavy).
The maximum horizontal speed of a single rotor helicopter depends on the power of the main motor. When a helicopter leans forward, it looses altitude. The power must be increased to maintain altitude. The more power it has, the further it can lean without loosing altitude, therefore the faster it can go. The top speed is important for fighting the wind. If the helicopter can go 15mph, then it can hold its position against a 15mph wind, though it won't be able to make any headway.
Some RC helicopters are sold on the Web from Asia directly to customers worldwide. There's nothing terribly wrong with this, but be aware of two things. It will take a good deal longer for your helicopter to arrive. And, if you need to return it because it's the wrong item or it's defective, you'll have to pay a good deal more for international shipping. It's probably worth paying a bit more to order from a retailer in your own country.
If you think there are any errors on this page, please let me know.
Disclaimer: The information on this page is accurate to the best of my knowledge, but I am not responsible for any losses or harm caused by its use. Take my advice at your own risk.
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