Since all rotors run at same speed using the single engine, use servos to tilt the rotors instead.  So all 4 rotors are more like the tail on a tricopter !

Sir i think these are not like tail of tricopter because tricopter will tail will tilt. Here in this the pitch of blades is controlled using servos which is similar to that of helicopter tail rotor pitch control mechanism.

it is more like a tail rotor of a heli, servo controls the pitch of the blades, guess it will be more efficient than variable speed prop with a fixed pitch, i reckon

probably very responsive and possible autorotation? 

Efficiency comparison to traditionälé quad