>another analogous musing -- why did we start with main+tail rotor helicopters? In fact we started with autogyros. Also the Fw 61 ("the first successful, prac

>another analogous musing -- why did we start with main+tail rotor helicopters? In fact we started with autogyros. Also the Fw 61 ("the first successful, practical, and fully controllable helicopter" though I don't know the history in detail) has two equal-size counter-rotating rotors similar to a quadcopter.