Originally Posted by
Cyclic Hotline
4. If the basic minimum pitch angle set in the blades is such that lift occurs as the main rotor reaches operating rpm, the main rotor lifts. The leading edge pitch links are fixed and as the rotor lifts, the pitch links decrease the blade pitch angle and the rotor loses lift and moves back down the amount of the axial play.
When the rotor moves down, the pitch links now increase the blade pitch and the rotor lifts back up and then the whole process keeps repeating. The process repeats at a frequency of the rotor rpm times the number of blades. This vibration or bounce in the aircraft can be quite severe and show a high lateral vibration or a high vertical vibration on test equipment on the ground.
SWEET!
That is a very amazing revelation! That description sounds like the condition of "bouncing rotorshaft" should be avoided at all cost, because it stresses everything, from MR bearings to pitch links and blade bearings.
But wouldn't that rotorhead + mast banging up and down create a clearly noticeable and rather frightening noise?