Why has a human powered helicopter attempt proved to be so much more difficult than its fixed wing counterpart?
A helicopter rotor is notoriously inefficient in producing lift compared to a fixed wing aircraft. Consider the large portion of the rotor (the inner portion) that sees a low free stream velocity. Lift depends on how fast a local wing section is moving. Airfoil sections on a fixed wing aircraft see a constant free stream velocity (the speed of the aircraft).