Main rotor diameter
Helicopter rotor(s) diameter. In fact, this parameter primarily determines the dimensions of the machine in the working position; this is especially true for three- and four-bladed models, where the propeller cannot be deployed along the fuselage, reducing the width of the space occupied (although the blades can be folded, which eliminates this drawback). Otherwise, the diameter of the rotor is of secondary importance: it is selected by the manufacturer in such a way as to provide features corresponding to the class of the machine, and it is worth focus primarily on the general purpose and price category of the helicopter, and not the size of the propeller.
Tail rotor diameter
The diameter of the tail rotor in machines of the classical scheme (see below). This parameter is of practical importance only in professional aircraft modeling sports, and even then quite rarely; relevant moments are described in special sources.
Battery capacity
The capacity of the battery supplied with the electric motor model (see "Motor"). Indicated only for variants using branded batteries (see "Battery type"), measured in ampere-hours: 1 Ah corresponds to the capacity at which the battery is capable of delivering a current of 1 A for 1 hour.
The higher the battery capacity, the more time the helicopter can spend in the air, usually. However, the practical time of operation on a charge is largely determined by other characteristics of the machine — dimensions and weight, engine model and power, etc. Therefore, in most cases, this parameter plays a purely reference role, and only helicopters that do not have any significant differences in other characteristics (and even then very approximately) can only be compared in terms of battery capacity.
Battery model
Model of the original battery (see “Battery type”) for which the helicopter is designed. Most often, such a battery is supplied with the device. Data on the battery model may be needed if it is out of order and needs to be replaced, when looking for a spare battery or when selecting a charger (usually, charging capabilities are already provided in the standard package, but it is possible that a separate device will be required).
Range
The greatest distance between the remote control and the helicopter at which the remote control transmitter is still able to guarantee normal controllability of the model. Note that official specifications usually provide data for perfect conditions: full battery charge, no obstacles in the signal path, extraneous interference, etc .; in fact, the range may be somewhat less. However, by this parameter it is quite possible to compare different models with each other.
The higher this indicator, the further you can let go of the helicopter from the remote control, the less often you have to move to keep control. However, a large range means not only a long range as such — it also speaks of a good signal penetration, its ability to pass through various obstacles. At the same time, powerful transmitters require appropriate power and large antennas, which affects the weight and dimensions of the console.
Dimensions (LxWxH)
General dimensions of the model. Note that the length and width are indicated only for the fuselage, excluding the main rotor. However, for ease of transportation, the blades are often made removable or folding.
