Question

Why is the flap hinge offset in articulated rotor?

(a) Design constraints

(b) Mechanical constraints

(c) Aerodynamics constraints

(d) Vibrational constraints

The question was asked during an interview for a job.

My question is from Blades and Propellers in section Helicopter Dynamics of Aerodynamics

Answer 1

Right answer is (b) Mechanical constraints

The explanation is: In an articulated rotor, the blades are attached to the hub along with lag hinges and flaps. They are usually offset because of mechanical constraints. For the shaft to transmit torque to the rotor blades, the flap hinge has to be offset by some amount.