Concept for New (maybe) VTOL Craft

[Dave_Jackson]

Mart,

The following are a bunch of obvious points, but they are being presented as logically comprehensible steps toward the essence of this concept.

The concept being; An Aerodynamically Variable-diameter PropRotor.

1. Helicopter rotors are efficient for lift because they have a large disk area and a low induced velocity per sq-ft.
2. Airplane propeller are efficient for propulsion because they have a small disk area and a high induced velocity per sq-ft.
3. The V-22 and the proposed V-44 have fixed diameter PropRotors. They are a compromise between a rotor and a propeller.
4. Sikorsky has considered a variable diameter rotor, however the mechanisms to vary the length of the blade's span are problematic.
5. The intention of the idea on this thread is that of using four proprotors that have physically fixed diameters. However, the pairing them allows for two different aerodynamically 'effective disk areas'. The larger area to satisfy the above #1 and the smaller area to satisfy #2.

For an elaboration on #5 consider;

• Two rotors with given characteristics and arraigned in a side-by-side configuration will provide 'a large disk area and a low induced velocity per sq-ft.'. As wanted for #1.
• Two rotors with the same characteristics and arraigned in a coaxial configuration will provide 'a smaller disk area and a higher induced velocity per sq-ft.'. As wanted for #2
• In other words, if these two rotors are arraigned as side-by-side for hover, and then rotated 90-degrees and arraigned coaxially for propulsion, they will give a better figure of merit in hover AND a faster forward velocity in cruise, than current tilt-rotors do.

This is a large view of the initial workup of the craft. It shows the PropRotors in their Hover configuration and in their Cruise configuration.

Dave