Two Helicopter suggested designs

[hesham]

Hi,


from L + K magazine,here is two helicopter suggested designs,but their drawings
are very familiar,one of them,they wrote NACA in its article,but I can't translate
Czech language.

 

[hesham]

Hi,


here is anther two suggested helicopters from 1930s.


https://books.google.com.au/books?id=nykDAAAAMBAJ&printsec=frontcover&dq=POPULAR+SCIENCE+1939&hl=en&sa=X&ved=0CDcQ6AEwB2oVChMIqb68mZeNyAIVhbNyCh1WwwKK#v=onepage&q&f=false