bear -
Per the diagram, the IPT DOES NOT have "dual thrust bearings". Look closer in the second bearing box area:
The aft ball bearing supports the HPC front end, and is the thrust bearing for the HP system.
The center ball bearing supports the IPT front end and the IPC aft end.
The forward ball bearing is "inside out"; the outer race spins with the fan shaft, and the inner race is rotating with the IP system. A typical differential bearing.
The LP axial load - be it fwd or aft - is thus added algebraically to the IP axial load, and this algebraic sum is reacted through the center bearing.
And remember - it's not only the gas path loads on the airfoils that are considered in the thrust balance equation. There are some large piston areas - fwd/aft faces of discs, air seal areas, etc. - that have LARGE static pressures on them creating large forces. (Remember F = P*A). One must work the summation of all these forces - perhaps dozens - to determine the bearing thrust loads. This is why one cannot glance at a sketch to determine the net loading.
