Lu,
The load on the blades is not a centrifugal force, it is centripetal. The blades don't try to stay at the rotor hub and get pulled away by a force, they want to fly tangentially from the head in a straight line. The loads at the hub are what are required to keep the blades from flying off. They pull in towards the center, thus are centripetal forces.
You're right that you can draw a picture with a force acting away from the hub balancing the other forces that demonstrates {how coning works}, but as I stated, that is only a way of explaining it...it doesn't prove that any such force exists.
The proper drawing is complete with a minimum of a vertical lift component, an equal and opposing weight, and a horizontal component of the lift that "supplies the required centripetal acceleration". The forces are out of balance because the system is not in equilibrium, the rotating blades are always being accelerated.
Don't think I fault anyone for using centrifugal force, I use it myself. That doesn't mean it's a real force...just a tool.
I agree with what you said about losing a blade. One of our aircraft ran into a crane about 10 miles offshore (fortunately), lost about 1m from each of the forward rotor blades. Even though they all lost about the same amount the imbalance was still enough to make the helicopter just barely flyable. They made it to the beach and shut down.
[ 28 November 2001: Message edited by: heedm ]