I have learned a few things about the roadable rotorcraft mentioned in
an earlier post. One of our chapter members is building a Butterfly,
same company, and has seen the motorcycle/rotorcraft perform.
The prop does not propel it on the ground. It has a chain drive to the
wheels. Also he has developed a new prerotator which permits him to
take off in about 20 feet. see
http://www.cartercopters.com/images/ctd-t_2006-01-16/ctd-t_2006-01-16_short_takeoff_2.html