Figure: Fully articulated main rotor @~copters


Figure: Semirigid main rotor @~copters

1) Chord
2) Span
~ the length of the line measured from the point of rotation to the tip of the blade
3) Vertical_Hinge_Pin (drag hinge)
~ in fully articulated main rotor
~ the axis which permits fore and aft blade movement independent of the other blades in the system
4) Horizontal_Hinge_Pin
~ the axis which permits up and down movement of the blade independent of the other blades in the system
5) Trunnion
~ is splined to the mast and has two bearings through which it is secured to the yoke
~ blades are mounted to the yoke and are free to teeter (flap) around the trunnion bearings
6) Yoke
~ the structural member to which the blades are attached
~ fastens the rotor blades to the mast through the trunnion and trunnion bearings
7) Blade_Grip_Retainer_Bearing
~ the bearing which permits rotation of the blade about its spanwise axis so blade pitch can be changed (blade feathering)
8) Blade_Twist
~ a characteristic built into the rotor blade so angle of incidence is less near the tip than at the root
~ helps distribute the lift evenly along the blade by an increased angle of incidence near the root where blade speed is slower
~ outboard portions of the blade that travel faster normally have lower angles of incidence,
~ so less lift is concentrated near the blade tip

Diameter_Main_Rotor = Span × 2

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