Originally Posted by
Dave_Jackson
Reverse Velocity Utilization should be extremely compatible with ABC. A report by Sikorsky in 1980 summarizes the features and future improvements to the ABC rotor. It discusses reverse velocity utilization. It even shows the profiles of proposed airfoils.
In fact, virtually, all of the X2's currently known features were mentioned in the above, and other, 25 to 40 year old reports.
Also consider that; ~
Dave, i agree with your comments about ABC and reverse velocity. I suspect the actual lift achieved with RVU is very low, so it is more a question of minimising drag and avoiding blade reverse flow divergence.
Since the X2 has fly-by-wire, the fact that the lower rotor lift distribibution does not exactly match the upper rotor is not an issue. As long as the blades local AOA is optimised for airflow the machine will slip through the air, whether or not it is symmetrical. The pilot still has a nice roll rate stick proportionality in all directions.
The poor autorotation "glide" performance would by greatly addressed by active blade twist over the advancing portion of the rotor. For this reason alone it does warrant investigation.
Mart