Single Rotor: Majority of helicopters are designed this way. Relatively simple way to accomplish everything you need to do. Limited weight capacity.<br />Dual Rotor: Chinooks. Counter-rotating. Controls are more complicated. Rear rotor is yaw and pitch control, and together they are roll control.<br />Tilt Rotor: Helicopter vertical capability combined with high speed flight. (eliminates dissymmetry of lift)<br />Main rotating wings create lift.<br />Feathering action: <br /><ul><li>Changing the rotor pitch (angle of incidence).
Rolling the rotor blade side to side. Greater pitch = greater lift.
Will generally have a positive pitch angle, to create positive lift.</li></ul>Flap or Teeter: Blades going up and down. Some have each blade moving independently, others the entire rotor system teeters on center point. Used to counteract DISSYMMETRY OF LIFT.<br />Lead/Lag or Hunt: Blades can move in/out<br />T/T Strap: Tension torsion strap<br />Common blade is 3, 4 (very common), and 6 (common on larger helicopters)<br />Types of Rotors<br /><ul><li>Semi-Rigid:
Lead/Lag</li></ul>Forces on the Rotor<br /><ul><li>Static (blade droop)
When slowing blades down, they tend to droop due to less centrifugal force.
Static (droop) stop is what limits droop. Prevent blade from dropping and chopping tail boom off.
Hinged weight with spring. At high rpm, weight is pulled down by centrifugal force, and stop is out of the way. At low rpm, weight is up, stop is in place, and spring keeps blades from drooping too far.