Main Rotor

The main rotor provides the lift force which moves the helicopter vertically, forwards, backwards, and sideways. It provides the mechanical means to attach the main rotor to the rest of the helicopter mechanical structure at the top of the mast. When viewed from below and aft of the helicopter and looking forward, the rotor blades turn clockwise.

It consists of the following systems:

• Rotor blades

• Rotor hub

• Rotating controls

• Main rotor indicating

The rotor hub and rotor blades are an assembly mounted at the top of the mast of the transmission assembly. For a system discussion and/or description, refer to Main Rotor Hub and Blade Assembly.

Rotor Blades

The rotor blades are lifting surfaces and structure attached to the main rotor hub assembly in such a way that they turn with the main rotor hub. When the main rotor hub turns, the interaction of the rotor blades with the air causes a lifting force which is transferred from the rotor blades to the main rotor hub. Each of the two rotor blades are underslung with respect to the rotor hub and are mounted on opposite sides of the rotor hub. Refer to Rotor Blades.

Rotor Hub

The rotor hub provides attachments for the main rotor blades, a means to change the pitch of each blade continuously and independently and a flapping axis mechanism for the main rotor. It is driven by the output shaft of the main transmission which gives the main rotor blades the necessary rotational power to provide lift for the helicopter. The rotor hub includes the main rotor hub assembly and the flap restraint assembly. Refer to Rotor Hub.

Rotating Controls

The rotating controls convert non-rotating flight control inputs from the rotor flight control system into rotating control inputs to the rotor hub. These controls cause the resultant lifting force vector to tilt away from the main rotor shaft axis which moves the helicopter in the direction of the resulting force. For a system discussion and/or description, refer to Rotating Controls.

Main Rotor Indicating

The main rotor indicating provides an electrical signal which indicates the angular speed of the main rotor shaft. This signal is used by other systems to determine NR and RPM warnings which are presented to the pilot. For a system discussion and/or description, refer to Main Rotor Indicating.