Development of a Mathematical Model of a Coaxial Compound Helicopter for Trimming and Stability Analysis

Abstract

The coaxial compound helicopter has been offered as an idea for a high-performance rotorcraft that possesses high-speed qualities that conventional helicopters do not. This work seeks to create a flight dynamics model of a coaxial compound helicopter and investigate its trim, stability, and controllability. Regarding this, this study builds aerodynamic models for each component of a coaxial compound helicopter (coaxial rotor, fuselage, horizontal stabilizer, vertical stabilizer, and propeller). For coaxial rotor configuration, an equivalent flapping model, a reflected model, an inflow model taking the upper and lower rotor’s impact into account, and a phased cyclic pitch model are done. A nonlinear coaxial compound helicopter mathematical model is constructed, and the trim across the entire flight envelope is carried out. The nonlinear model is linearized in order to evaluate stability and control derivatives. The trim results exhibit a high degree of concordance with the reference, thereby validating the flight dynamics model.