Sikorsky X2 coaxial heli developments.

[Dave_Jackson]

Mart,

Your first two paragraphs are valid.

I should have been clearer about the use of the disks. They were presented to show the aerodynamic interaction of two main rotor disks, and specifically the regions of high and low induced velocities.

As you know, high induced velocities are less efficient than low induced velocities. The fixed wing is far more efficient then the rotor blade simply because the fixed wing generates a fairly constant induced velocity over its surface.


As an aside;

Momentum Theory is a reasonable method of performing an initial assessment of rotor performance. This is because all single rotors are basically the same except for the nuances such as; twist, taper, etc., plus blade count.

However, IMHO, Momentum Theory totally breaks down when it come to the consideration of multiple, aerodynamically interactive main rotors.

This is why I express my disappointment that Igor led rotorcraft away from the aerodynamically superior twin rotors. It should be noted that virtually all of the research and development followed along behind the single rotor.

Rotorcraft have always been inefficient. However, when electric drives start permeating the fields of transportation the rotorcraft industry must look back to the past for it to move forward into the future.


Dave