I thought it was well known that a helicopter cannot hover
or land in a courtyard, the walls cause the airflow to form a
doughnut shaped torus of air, instead of being accellerated
downward and outward.

         This made the news 20 or 30 years a go when a woman
pilot was asked to hover in a church or school courtyard while
a man tossed out prizes of some sort.    
         People were decapitated when the hekicopter lost
lift and fell.


         As far as low radar cross section helicopters go, the
patent office included a 1977 study on the uh-60 in the
office response to the application I mailed on Dec. 22, 1978.
         It was stamped "Level 12", whatever that meant,
I had no clearance at any time, and that application was
never under secrecy order.