What are the issues that exist for the 97 but did not seem to limit the 53,64. and 67 or the Cheyenne?
What is unique to the ABC concept that other Rotor Systems do not share when it comes to size increases?
Did the Russians not have some success with Co-axial Rotor systems?
Then there is the Piasecki X-49 pusher that uses a Blackhawk airframe and Rotor System....how does that compare to the 97?
https://tacairnet.com/2015/08/05/pia...-in-existence/
https://ntrs.nasa.gov/archive/nasa/c...9970015550.pdf