A rotorcraft is a flying vehicle that achieves heavier than air flight by using rotating blades to generate

lift.

A helicopter is a type of rotor craft, but there are quite a few other variations on this

theme defined primarily by the number of blades they utilize on their rotors, which are

the spinning bits, but also the number of rotors they have.

A typical helicopter has one primary rotor with four blades, though they often require a complementary tail rotor or some other type of mechanism

that allows the craft to apply force along a different axis than the main rotor,

so it can maneuver in three-dimensional space, rather than just being able to go up and down.

Other variations on the helicopter theme exist, however, including dual main rotor models

that grant the craft additional carrying capacity,

compound helicopters that pair a primary rotor with some other kind of propulsion source,

like a jet engine, so they can take off and land vertically, but then fly a bit more like a jet,

and quad rotor craft, today often called quadcopters, which use four primary rotors, spaced

out equally around the center of mass of the craft.

This latter setup has become especially common in the drone space, as although many long-range

and extended duration military-grade drones use plane-like

propulsion systems, those meant for shorter distance use, and those sold on the consumer market,

are more likely to be rotorcraft, and the dominant design for those purchasable by everyday people

is the quadcopter setup,

with four rotors wielding somewhere between two and six blades a piece,

which provides relatively stable and versatile flight for remote-controllable drones of a variety of sizes.

From those that will fit in the palm of your hand, to those that are about the size of a large of sizes, from those that will fit in the palm of your hand to those that are about

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