Collective pitch
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Refers to the pitch (or angle of attack) of blades of a helicopter. There are two types of collective pitch:
- Collective pitch changes the angle of attack of all blades by an equal amount in unison. The pilot uses the collective pitch control to adjust the main rotor and make the craft rise or descend. In helicopters with anti-torque tail rotors, tail rotor collective pitch is controlled by the rudder pedals to make the craft yaw left or right.
- Differential collective pitch affects the yaw of the helicopter — the turning movement of the aircraft to the right or left. In a coaxial rotor helicopter, differential collective pitch control allows the collective pitch of one rotor to be increased while simultaneously decreasing collective pitch of the other. This produces an increase in resistance, and more torque in one rotor than the other, turning the craft on its vertical axis.
[edit] Related concepts
Cyclic pitch differs from collective pitch in that it changes the tilt of the rotor disc and determines the direction in which the helicopter will fly. In tandem rotor helicopters, adjusting cyclic pitch of the two rotors in opposite lateral directions will cause the craft to yaw, while adjusting it in unison will cause the craft to translate (move sideways).
