"Best way to get supersonic in a rotorcraft is to go to 15,000 feet, pull both engines to idle, put the rotor brake on and wait..."
Hehehehe!! This was part of the test program on ABC then?
Just been reading the Fatigue Time Life proving requirements for helis:
http://avstop.com/Helicopters/20/
You TPs really earn your way!
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"...think about the Tiltrotor's drivetrain"
My point exactly. Operating costs will win friends with no one, and just wait until we get threads along the lines of OEI with driveline failure (even Chinook is not immune to sprocket tooth failure).
"I STILL don't understand your disk loading concern"
Draw your interleaver in plan, then see how big a single rotor would fit into the same "parking" space. Intermesher planform gets much closer to circle (optimum for hover). No need to use retreating blades, so why not just feather 'em?
Since v-RRPM is essential for high speed, blades need to be designed to run in plane anyway. Root/hub will need to take same bending moment as fixed wing, but that just lends itself to aircraft manouvreability. The trick is going to be careful rotor/blade design, to allow the right modes of stiffness and compliance - you're already thinking along these lines. The whole thing just strikes me a very good high performance rotorcraft package, with fewest technical risks.
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"...but Roton beat us to it."
Being able to deep cone the rotor was a good way to achieve supersonic auto. In theory you could use coning to produce a supersonic prop (king of a rotary swing-wing) - converts some disk flow velocity to axial flow. Trouble is during engine failure you have to allow for fast coning the other way. The original plan was rotor assist launch, but clearly they were eventually forced into the "keep it simple" philosophy...
Mart