Well - OK, Dave. I'm just a little concerned since the discussion is moving away from the thread title
Sikorsky X2 coaxial heli development (which is now actually accumulating flight time) towards various unspecified concepts (which are not). As i've commented before, i find it very difficult to provide constructive feedback, since i am never sure which concept i am meant to be considering. This is part of the engineer mentality: figure out the best solution using available data, then make it work - it is a well proven method of getting things done. That does not disallow future improvements, but often does mean that the solution is a compromise of keeping all of the designers the least unhappy. That's just the way of things...
One of my favourite quotes comes from Aaron Cohen, the program manager who kept Space Shuttle development within budget:
"Better is the enemy of good."
Let us agree that in principle the tractor does offer
some aerodynamic advantages in certain parts of the flight envelope. However, a tractor would not suit a machine which is after all still a helicopter. Powertrain packaging would be my main reason. But, putting engineering issues asside, visibility of touchdown point will also never be as good with a tractor.
Let X2 prove that 250kts is possible in a helicopter - that is already a challenge. Once this is done the we can discuss improvements until the cows come home...
