The main rotor design features a 6.5 meter blade with a 1 meter chord, so that each rotor disc has a footprint that is 70% higher than the previous quad-rotor HPH design (Yuri-1994).
Both aerodynamic and structural calculations were carried out to predict the best conditions and the best blades designs to deliver the most thrust for the least power.
Each rotor has two blades, with a total of 10 full scale rotor blades were built. The blades’ weight and shapes slightly varies due to manufacturing differences (and various repairs) so a balancing process was employed to make sure each pair of blades produces the same amount of thrust.
The blade is made of a foam leading edge, a
main spar designed to take most of the load,
and an aft-section made of foam and balsa
strips, covered with lightweight material.
The longer blade is designed to better exploit
aerodynamic ground effect for power reduction.
It is important to note that without ground effect, the HPH cannot fly since the required power to
rotate the blades grows rapidly as the helicopter gets further away from the ground.