The Piccolo's head is based on Dieter Schluter's simplified Hiller head used in his early R/C helicopters way back in the 70's (the full-size Hiller head was patented for full size choppers in the early 50's).
The main rotor is influenced by the flybar, i.e. not controlled directly by the servos. This results in good stability and relatively low loads on the servos.
Rotor blades are fixed pitch, this makes aerodynamic balancing less critical than with collective pitch as well as simplifying the mechanics.
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