Controller
My understanding is this:
The TPP as a few people have written is just a contruct to "help" sort POF questions out. If the helicopter is sitting on the ground in nil wind at operational RRPM with no pitch applied the TTP and plane of rotation are one and the same thing.
If the blades are under load and begin to cone, no wind, cyclic neutral, same thing.
However, if there is any difference in the relative velocities of the blades and they begin to flap or teeter, or if a cyclic input is made, the path described by each blade will no longer be uniform : consider flapping to equality of angle of attack or rotor thrust for example. Also refer to Hooks Joint Effect. The TPP is then used as an "average" of the orbit described by the aerofoils.
TT