"David E. Powell" wrote:

Makes me think back to some of the studies looked at
in the 1980s, ...

People have been tilting at this windmill a lot longer than that.
There's a cute summary (circa 1997) at:
http://www.vstol.org/wheel/wheel.htm

In any event, I'm sure any patents that Lockheed had on
the AH-64 have expired by now :-)

If X2 can approach the safety standards of conventional
helos (e.g. has credible auto-rotation that is safe to routinely
demonstrate), it may eclipse tilt-rotor on that measure alone.
I still doubt that tilt-rotor will gain civil certification, something
now in the promised state for over a decade.
X2 might.

--
Regards, Bob Niland
http://www.access-one.com/rjn email4rjn AT yahoo DOT com
NOT speaking for any employer, client or Internet Service Provider.