I know that in helicopters the N2 and Nr are coupled. I would appreciate a physical explanation leading to the cause of how the rotor blades could overspeed if collective (power) is lowered suddenly
I have heard that the rotor head needs to have a torque load in order not to overspeed. but I am not sure how that works.
The only thought I have in mind is if I am spinning something and suddenly I stop doing so, it is going to spin at the speed it had when I stopped the motion and/or less and decrease from there. But I dont see how can something could "overspeed" if the motion (energy) is stopped. The kinetic energy will be dissipated by lowering its speed but it cant increase, if so how and why? thank you