Currently the market is literally flooded with all kinds of helicopter models, from indoor “micro” and ending with gasoline and turbojet monsters. It’s easy to get confused in all this variety.

Classification by size
Basically, helicopters are commonly distinguished by size. Historically, the models are classified according to the volume of combustion engine, electric helicopters are attributed to a particular class on the similarity of geometric dimensions with models in an internal combustion engine, and, above all, the diameter of the main rotor.

Room and micro
Room and micro helicopters are designed to fly in the hall. Theoretically, a room helicopter can fly in the big room of your apartment. But in practice, such flights are very problematic, because you need to have extensive experience piloting to avoid collisions with furniture and walls. Only some models like hirobo “lama” are stable enough to fly around the room, but flying at home and learning to fly at home in a microcopter is a questionable activity. It is difficult and expensive to find a hall for flights, and flights in the street are strongly hampered by the wind, to which small models are mostly exposed.

Microcopter can be divided into three groups:

Toys include almost all micro-rotorcraft sold in the kit “readytofly”. As a rule, these models do not have a total pitch control system and can only perform horizontal figures. For example: Jabo, Hirobo “lama” and their numerous clones. On the Internet there are a lot of resources dedicated to “upgrade” these models aimed at improving the flight characteristics, but dramatically improve their performance without a complete redesign is impossible, but it will be a different model.
Electric micromodels for the gym. Usually they are sold as a kit of parts (KIT). The kit does not include hardware, batteries, gyroscope and other electronics – all must be purchased separately. These models have common pitch control. The collector motor that comes with the kit is usually replaced with a more powerful commutatorless motor. Lightweight lithium-polymer batteries are used. Such a set helicopter is capable of performing many figures of 3D piloting. The most striking representative of this type of models is the Czech company MSComposit – Hornet, as well as its subsequent modifications. Many will say – “yes I flew it at home! Well, I flew too, but it’s hard to call hanging in the middle of the room and spinning on the spot flying. In order to fly it you need at least the size of a school gym, and that’s already a problem. It is possible to fly this helicopter in the street, but in the wind of 2 or more meters per second it turns into an endless struggle with the wind. In any case, such flights can not be called comfortable.
Electric micromodels for the street and helicopters with internal combustion engines of .15 cubic inches.

Class 30
Helicopters in this class have a .3 cubic inch (5.5 cm^3) caliber engine. Often there are 0.32, 0.36 and 0.39 cubic inch engines – all of these engines are installed on the same model, without requiring any upgrades. The rotor diameter of such a model is about 1200 mm.

50 class
Helicopters in this class differ from Class 30 helicopters in engine displacement, gearbox with a different ratio, and rotor size. What does it give? Greater thrust-to-weight ratio and greater stability. The helicopter with the .50 cc engine has excessive power, it is more difficult to “overload” in flight in case of unskillful general pitch operation. Such model can perform some extreme 3D aerobatics figures, e.g. “tic-tac-toe” and some others, which require increased power to perform.

60 – 90 class.
Strictly speaking, these are two different classes. However, similar to the previous class, the 90 class models use the same chassis as the 60 class models, so we will consider them together.

Bigger Models
The 90 class models are not the biggest. There are much larger wind turbines. They are equipped with gasoline and even turbojet engines. Their flying characteristics are worse than the 90 class models. As a rule, the larger models are copies.

Models with an electric motor
Helicopters with electric motor appeared comparatively recently, promptly occupied the empty niche of indoor (hall) models and small models for the street. This is primarily due to the appearance on the market of relatively cheap, light and high-capacity lithium-polymer batteries capable of delivering sufficient current. Electrovertopters of medium (with rotor diameter from 1100mm to 1300mm) and large (with rotor diameter more than 1300mm) class exist, but they are very expensive to repair and because of this are rather uncommon and are still rather exotic.