The hub of a conventional teetering rotor is designed so that the axes of the two spindles (feathering bearings) have a pre-coning angle of 2-3 degrees. The teetering hinge is located an inch or two above these spindles. This undersling is so that the CG of the two blades and the teetering hinge are all inline, under mean disk loading. From their mean position, the blades' CGs will rise and fall (cone), in respect to the teetering hinge, as the disk loading changes.
The Question:
Why cannot a rotor be produced where;
1/ The teetering hinge has no undersling. It is located inline with the
feathering bearings.
2/ The spindles have a small 'downward' coning angle or the blades are manufactured with some anhedral along their full span,.
3/ The blades are constructed with a high amount of stiffness and strength.
Because of the deflection in the blades, under mean disk loading the CGs of the two blades and the teetering hinge are inline, just as they are above. The difference is that now there is no coning angle.
The Perceived Advantages:
1/ Reduction in cross-coupling.
Perceived Disadvantages: 1/ The rotor will be heavier
2/ The root of the blades will be thicker and will cause a slight increase in drag.
3/ The control loads will be very high.
