Using eBay to purchase remote control helicopters can seem daunting at times, especially if you are new to the hobby. The biggest problem is not knowing what the many terms used to describe RC helicopters mean and it’s exactly this that can lead one to disappointment, either by buying a too advanced or too simple helicopter or purchasing a helicopter that performs undesirably.
A few things that you should get to know before looking at purchasing RC helicopters over eBay or even locally:
Channels: RC helicopters come in all shapes and sizes but most importantly, they can come in different channels. The following list explains RC helicopter channels and explains roughly what each means. Note however, these descriptions are only for the actual helicopters available channels and not of the remote controls available channels (some remotes have access to more channels than the helicopter has available).
2CH or 2 Channel: 2CH RC helicopters are the most basic form and are aimed at the beginner level of flying. 2CH means that the helicopter has 2 available channels to change its movement. 1st been collective/throttle adjustment and 2nd can be rudder or elevator adjustment but not both (It can depend on the 2CH helicopter you purchase for which you get). Basically the helicopter can only move up and down and forward and back or up and down and turn left or turn right. 2CH lack full control of helicopter's movement and I’d recommend them only to beginners or just for fun as they are usually quite cheap.
3CH or 3 Channel: 3CH RC helicopters are a step above 2CH but can still be considered a beginner level helicopter. 3CH allows the helicopter to have control over the throttle/collective (up and down), elevator (forward and back) and rudder adjustment (turn left and turn right). 3CH helicopters give the pilot control over the helicopters movement and allow them to fly the helicopter to desired locations. I'd recommend this type of helicopter to any RC hobbyist as they are easy to control for both beginners and professionals, however they aren't easy to control right out of the packet, it will take some practice to get use to the helicopters controls.
3.5CH or 3.5 Channel (with gyro): 3.5CH helicopters generally have only one addition to a 3CH helicopter and that’s gyroscopic stabilisation. With Gyro, the microchip inside the helicopter will attempt to stabilise the helicopter in flight and keep it still on all axis’s (up/down, left/right and front/back). Gyro isn't always 100% effective but it can make flying a RC helicopter much easier, if looking for a 3CH RC helicopter, I recommend you look for one that is 3.5CH or 3CH and states with gyro as it allows significantly helps with controlling the RC helicopter.
4CH or 4 Channel (With or without gyro): 4CH RC helicopters are stepping into the more advanced form of RC helicopter piloting. I'd recommend 4CH helicopters only to experienced RC pilots as they can be somewhat more difficult to learn to fly unless you have already had some experience with 3CH helicopters. 4CH RC helicopters give the pilot control on the throttle/collective (up and down), elevator (forward and back), rudder (turn left and turn right) and ailerons (bank (roll) left and bank (roll) right). This type of helicopter give the pilot much more control and allows them to even perform basic manoeuvres and with Gyro they are much easier to handle.
5CH or 5 Channel and beyond (With or without gyro, 6CH, 8CH, 14CH, etc): 5CH+ helicopters are advanced RC helicopters which give the pilot near or complete control over the helicopters movements. Only experienced pilots should fly 5CH+ RC helicopters as they are usually expensive and difficult to learn with no experience. 5CH+ helicopters usually give the pilot control over the throttle (power and speed), collective (up and down), rudder (turn left and turn right), full-control elevator/cyclic pitch (forward and back + altitude (diving)) and ailerons (roll left and roll right) but some RC helicopters can give the pilot control over gyro gain and advanced remotes include adjustable mixing functions (throttle/rudder). These helicopters can allow for full 3D flight and acrobatic manoeuvres such as loops, complete-rolls, figure of 8's and upside down flight.
Power Source: Another major thing about RC helicopters is selecting a helicopter's power source. Commonly available RC helicopters can be powered by either nitro (nitromethane-methanol), batteries (electricity), gas turbine or petrol. Personally i use only electric powered RC helicopters as of the moment as it is easy to recharge or keep spare batteries and the flight time is not too different from nitro (typically 4-15mins vs. 7-20mins respectively).
Electric RC helicopters are my recommendation for first-time and beginner flyers and even advanced flyers as its not messy and recharging the device is easy. Petrol and nitro can be a little bit messy and are more advanced than simple electrics with the addition of using liquid fuels, however they can provide longer flight-times (even longer is a jerry can is nearby) than electric and can provide more power for larger helicopters. Turbine helicopters are professional level helicopters, mainly due to the cost of purchasing one.
Signal connection: The last topic I will cover in this guide is what you should look for when determine what medium is been used to transfer data between your remote control to your RC helicopter. There are 2 main types of electromagnetic waves used to transfer information to and from your RC helicopter and that’s radio and infrared. As a beginner, signal connection isn't very important but as an advanced RC hobbyist it can be very important to prevent loss of sync between a remote and a helicopter. Infrared has one main problem and that’s daytime. An infrared RC helicopter will suffer shortages radio control during daytime and this is because the sun produces infrared radiation which interferes with your RC helicopter. The safest bet is to go with radio, most preferably 2.4 GHz. Using such, other radio equipment, such as other RC hobbyists or radio stations nearby have a very insignificant change of causing interference between your receiver and transmitter, this way you don't need to fret about suddenly losing control of your helicopter mid-flight.
I hope anyone interested in purchasing RC helicopter via eBay or even locally has found this guide somewhat useful and I thank you for taking the time to read through this guide. Remember, when choosing to purchase a RC helicopter, keep in mind the level you wish to fly the helicopter at, be it full control or little control? Knowing more about what you want from the RC helicopter will ensure you purchase the correct one.
As eBay Guide Policy asks contributors to avoid linking outside of eBay I wont provide any links of sites I used to obtain specification or clarification on topics discussed. Note however nothing has been copy/pasted from any other sites and/or sources, this entire guide is a result of my own work and knowledge on this topic.