When choosing
your first helicopter you first have to decide which type of chopper you wish to
purchase, a collective pitch machine, or a non-collective pitch machine. If you
are starting the R/C hobby from scratch and must buy everything, I would
strongly suggest the collective pitch machine. Although it is a bit more
expensive initially, it is by far the more versatile of the two and will help
you enjoy more advanced stages of the hobby after you have learned to fly. You
will also find the learning process easier with a collective pitch machine.
On the other hand, if you are already into radio controlled aircraft and have an aircraft radio, and an aircraft engine in the range that would fit a non-collective machine, this route may be desired to drastically reduce the start-up cost and to get you involved in the sport with less money. Once hooked however, you are bound to want to move up to a collective pitch machine. I am going to assume you are starting from scratch and will continue with the idea of starting with a collective pitch helicopter.
Unlike aircraft where there are specific trainer models geared solely for the first time kit, the differences between helicopters is more suttle with the major difference being size and precision. The larger and more precision a machine is, the better it will fly. These machines would make great training helicopters but they are usually alot more expensive, with high precision parts, and would be very costly to repair in the case of a crash. They are better suited toward competition and the experienced modeler where accidents are usually minimal.
Keep in mind, when learning to fly a helicopter you are bound to have a crash or two and parts are going to have to be replaced. Replacing parts on a precision machine could really run you a bill! A good place to start would be a machine designed for a .30 size engine, a stable flyer with collective pitch, and one with a good avialability of parts.
The Engine
The
helicopter engine is similar to a 2-cycle aircraft glow engine except that it
has a larger heat sink head for better cooling, and a carburettor with improved
mid-range adjustment. When purchasing the helicopter engine, the muffler is not
included. Usually the muffler comes with the helicopter kit.
Different motors facilitate different starting methods. Some come with a pull
start system for very simple starting. Others use a cone start where an electric
starter is used in a manner similar to starting an aircraft. Still others use an
electric starter and a belt for starting.
The Radio
As mentioned earlier in this introduction, a proper
helicopter radio differs from a standard aircraft radio. There are certain
functions that must be mixed electronically and these are found only in radios
designed for this purpose. More and more often, one is able to find radio
systems that have functions suitable to both aircraft and helicopters. If you
think you may be involved in both aspects of the hobby, you may wish to choose
one of these for your system.
Other things to think about when purchasing a helicopter system are the servos and the battery pack. It is desirable to choose servos that have output shafts that are ball bearing supported. Since the pressure and vibration on the servos in a helicopter is usually greater than in a plane, bushing servos tend to wear out very quickly and lose their precision which is extremely important in the controlling of a helicopter. Because you are using a minimum of five servos and a gyro (to be discussed later) in a helicopter, and the higher frequency of control input, it is very desirable to have a larger battery pack than the standard 600 maH pack that comes with most aircraft radios. A pack in the range of 1000 to 1200 maH is a better pack to consider. Many helicopter radios take both of these concerns into consideration and come packaged with five BB servos and a large batter pack.
Also, it is recommended to get a computerized radio so that it will be easier to setup your helicopter for the correct pitch and throttle settings. Non-computerized radios can also be used, but they tend to be limited in its function and you will very quickly outgrow them once you get into flying aerobatics.
Receiver
You will also need a receiver to receive the transmitter
signal and then transmit it over to the servos. There are basically two types of
receiver. But getting whichever depends greatly on your type of radio and what
it can support. 
PPM receivers are
the "standard" type of receiver for most radios. Glitches in signal are
immediately noticed by erratic movements of the servos.
Some people prefer PPM to PCM due to the above reason, but in general, PCM receivers (and transmitters) are a lot more expensive than PPM.
Servos
Servos are machanical motors which are linked to the receiver
and to the helicopter's control surfaces via machanical linkages. Again, there
are many different kinds of servos ranging from 3kg torque to as high as 9kg
torque. Generally, the higher torque servos are used for advanced flying like
aerobatics and 3D, and the normal or standard servos for general flying.
For a helicopter, you require a minimum of 5 servos.
A gyro, is an
electro-mechanical device used in a helicopter to help semi-automate the
response of the tail rotor. In the case of an R/C chopper, the device fits
electrically between the receiver and the servo that controls the pitch of the
tail rotor blades. A sensor measures any unwanted change in yaw of the aircraft
and will correct the situation by increasing or decreasing the tail rotor pitch
to stabilize the movement.
It is strongly recommended that a gyro be used in every helicopter. Without a gyro, the tail can spin around uncontrollably, making it spin and crash. Controlling an overly sensitive tail of a helicopter is most frustrating and the gyro can help make the flying much easier and more pleasurable. Gyros are made by most radio manufacturers for operation compatable with their systems.
A new type of piezio gyro have recently hit the stores. Known as the
heading lock gyro, this gyro is capable of maintaining the heading of the
heli even in strong wind conditions and thus allowing you to fly in any
direction without the head or tail swinging about.
Field Equipment
The field equipment you require will depend largely
on the type of starting mechanism for your helicopter. If you have a glow motor
with a recoil pull-starter, you will only require the basics of a fuel
can & pump for carrying and pumping fuel to your heli, and a glow
plug igniter to supply current to the glow plug during starting.
If you do not have a pull start, in addition you will undoubtedly need an electric starter powered by a 12 volt battery to turn the engine over. Making a flight box which contains all your necessary field equipment might be a good idea!
Other Accessories
Since the helicopter is purely a mechanical
device, tools for assembly usually include items such as screw drivers, ball
drivers, nut drivers, wrenches, pliers, fuel-filters, addition glow plugs
etc. In addition to these there are a couple of specialty tools that come in
handy when assembling and setting up the mechanics of your helicopter.
One tool you may want to consider to assist in assembly is a set of ball link pliers. The ball link is the most popular linkage piece on a helicopter and virtually all choppers use them. The ball link pliers greatly assist in the removing and adjusting of these links.
A second tool that is extremely valuable during set-up is the rotor blade pitch guage. This device can help you line up your rotor blades so that your pitch is correct. A blade pitch guage can go along way to helping avoid costly crashes and frustration down the road as so much of your chopper's well being depends on how well it is set up initially and maintained throughout its lifetime.
Of course, last but not least, glow engine fuel, which is normally a mixture of nitromethane, and lubricants like caster oil or synthetic oil. Helicopter fuel are normally 15% nitro, although you might like to use 20% for more power for aerobatic flight.
WebStats
System.