pääroottori

Pääroottori (Finnish for "main rotor") is the principal rotating wing assembly on a helicopter or other rotary-wing aircraft that produces lift and controls attitude. It consists of multiple rotor blades attached to a hub and mast; by altering the pitch angle of the blades, the main rotor generates variable lift and thrust to enable vertical takeoff, hover, forward flight and maneuvering.

Key components include the rotor blades, hub, mast, swashplate and associated pitch-change linkages. The swashplate transmits pilot inputs for collective pitch (changing overall blade pitch to climb or descend) and cyclic pitch (varying pitch through rotation to tilt the rotor disc and control direction). Rotor systems are categorized by articulation: rigid, semi-rigid and fully articulated, each with different mechanical joints and dynamic characteristics.

Aerodynamic phenomena associated with the main rotor include dissymmetry of lift, retreating blade stall, and rotor-induced vibrations. Torque produced by the main rotor requires an anti-torque system—commonly a tail rotor, NOTAR or coaxial rotors—to maintain directional control. Rotorcraft safety procedures also rely on the ability to autorotate, using the main rotor to descend safely during engine failure.

Materials have evolved from metal and wood to advanced composites for improved strength, fatigue life and damage tolerance. Maintenance focuses on blade inspection, track-and-balance, bearing and hub checks, and monitoring for ground resonance in certain rotor types. The main rotor remains the defining and most mechanically complex element of helicopter design.