There are three main types of helicopter rotors: single rotor, dual rotor, and tilt rotor. Single rotor helicopters are the most common but have limited weight capacity. Dual rotor helicopters like the Chinook have counter-rotating rotors for control and lift. Tilt rotor helicopters can hover like a helicopter and fly fast like an airplane. Rotor blades use different mechanisms for control including feathering, flapping, and lead/lag movement. Forces on the rotor like torque and dissymmetry of lift are counteracted through techniques such as tail rotors and adjusting rotor pitch.
14. When slowing blades down, they tend to droop due to less centrifugal force.
15. Static (droop) stop is what limits droop. Prevent blade from dropping and chopping tail boom off.
16. 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.