The swashplate is the device that translates the pilot's (or autopilot's) commands via the helicopter flight controls into motion of the main rotor blades. Flight regimes Helicopters can operate in several flight regimes. ...

The two axis control of the cyclic and the single axis collective control of the helicopter need to be transmitted from the non-rotating fuselage to the rotating rotor hub and the mainblades, which necessitates a special joint called the swashplate. It consists of an outer non-rotating portion with push rods or hydraulic actuators that respond to the pilot controls and an inner rotating portion that is connected via pushrods to the rotor blade grips (or Bell / Hiller bars, if equipped).

The swashplate must be able to pitch forwards and backwards and roll left and right for the cyclic, as well as translate up and down for the collective. This requires the inner swash to slide on the mainshaft while being able to tilt freely. The inner swash also needs an anti-rotation link to prevent it from rotating independent of the blades, which would apply torque to the pushrods. The outer swash typically has an anti-rotation slider as well to prevent it from rotating.

If the aircraft does not have Bell / Hiller controls, the inputs from the swashplate will be out of phase with the blades and necessitate a phase angle correction via an offset arm. The specific phase angle depends on the rotational rate of the rotor, design of the rotorblades and other factors, and is typically fixed at time of manufacture. With Bell / Hiller controls the inputs to the rotor will always be 90 degress out of phase due to gyroscopic forces.

On most modern aircraft the swashplate is above the transmission and the pushrods are visible outside the fuselage, but a few early designs placed it underneath the transmission and enclosed the rotating pushrods inside the mainshaft. This reduces rotor hub drag since there are no exposed linkages.