a type of two-seat helicopter designed by a man that won the highest award at the 1912 moscow aviation exhibition for the s-6-a airplane. this helicopter was in competition with the pitcairn xo-61.
a type of two-seat helicopter designed by a man that won the highest award at the 1912 moscow aviation exhibition for the s-6-a airplane. this helicopter was in competition with the pitcairn xo-61.
sikorsky r-4
igor sikorsky