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Collective pitch RETURN

The collective pitch lever (often referred to simply as "the collective") controls the pitch of the blades uniformly ("collectively") through the entire 360-degree cycle of rotation. As collective pitch is increased, the main rotor develops more lift, and so the helicopter can be made to rise or descend vertically, or by inclining the rotor disk develop thrust to move over the ground. As the collective pitch changes, the amount of power required to keep the main rotor spinning at the same RPM changes, and must be compensated for by changing the throttle. In model helicopters, the collective pitch and throttle are controlled by the same control via the pitch curve and throttle curve, which specify how much pitch or throttle to use at each position of the collective control. Different pitch and throttle curves can be selected for different types of flight using the flight mode switch. The pitch of the blades can be measured and so adjusted using a pitch gauge. Most model collective pitch helicopters can be configured so that in addition to 'positive' collective pitch for climbing and normal flying, they also have equal 'negative' collective pitch, allowing very rapid descents, autorotation and inverted flight. Nowadays it is normal to set up a helicopter to have equal amounts of positive and negative pitch, and limit the available collective pitch via the pitch curve. Most model helicopters hover at about 4-5 degrees collective pitch.