Blades
on a helicopter are pitched, or angled, in different ways to control
the direction of movement of the craft. The three types of pitch
are cyclic pitch, collective pitch, and differential collective
pitch.
Cyclic
pitch is the individual angling of the blades on each revolution
of the rotor. This affects the roll of the craft, moving the nose
upward or downward or rolling the craft from side to side.
Collective
pitch is the angling of all blades by an equal amount in unison.
The pilot uses collective pitch control to rise vertically.
Differential
collective pitch affects the yaw of the helicopter—the
turning movement of the aircraft to the right or left. Differential
collective pitch control allows the collective pitch of one rotor
to be increased over the 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.
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