Identification of Higher-Order Rotor Flapping Dynamics Model Structures using Explicit Soft Inplane Hingeless Rotor Hub State Measurements of the NRC Bell 412 Advanced System Research Aircraft

NRC developed a higher-order mathematical model structure of coupled rotor-body flapping dynamics for inflight control applications. The hybrid (rigid body fuselage state and rotating hub rotor state) 8DOF model was developed utilizing explicit measurements from a novel rotor hub state measurement system enabling estimation rotor blade dynamics. The method identified second-order rotor flap dynamics, attitude-rate and rotor flap dynamics response correlation, and response lead of rotor flap dynamics over rigid body dynamics. Reducing implementation resource burdens of past approaches, this novel rotor state measurement and modelling methodology may prove useful in applied development cycles across a spectrum of needs for articulated (helicopter) and non-articulated rotor (tiltrotor, eVTOL) aeromechanics, modelling, monitoring, and operations.