Rotary-wing aircraft fall into which two categories?

Rotary-wing aircraft are primarily characterized by their ability to generate lift through rotating blades or rotors. The two main categories of rotary-wing aircraft are helicopters and multi-rotors.

Helicopters are traditional rotary-wing aircraft with a single main rotor and often a tail rotor for stability and control. They are versatile and can operate in a variety of environments, performing tasks such as transport, medical evacuation, and aerial firefighting.

Multi-rotor craft, on the other hand, typically have multiple rotors that provide lift; they are often used in applications like aerial photography, surveillance, and recreational flying. Multi-rotors can be configured with varying numbers of rotors (such as quadcopters, hexacopters, etc.) and are known for their ease of control and stability.

The other provided categories, such as bi-planes, gliders, hovercraft, do not fit the definition of rotary-wing aircraft. Bi-planes are fixed-wing aircraft and do not have rotating blades, while gliders rely on aerodynamic lift rather than rotary motion. Hovercraft operate by creating a cushion of air for lift but are not classified as rotary-wing aircraft. Therefore, the distinction between helicopters and multi-rotors encompasses the primary types of rotary-wing