What type of wheels do some helicopters have?

Certain helicopter models are equipped with retractable wheels, which serve to optimize the aircraft's aerodynamics during flight. These wheels can be extended for landing or taxiing, providing a stable base, and then retracted into the fuselage once airborne to minimize drag. This design choice enhances overall flight performance by reducing air resistance, making it a valuable feature in more advanced helicopter systems.

The presence of retractable wheels is not universal across all helicopter types, which is why the other options may imply features not shared by all models. Some helicopters utilize supplementary skids rather than wheels, and while retractable wheels improve aerodynamics, they are not featured on every rotorcraft, which further delineates the uniqueness of aircraft designs in the helicopter category.