IMPLEMENTATION OF ROTARY-WING AEROMECHANICAL PROBLEMS USING DIFFERENTIAL-ALGEBRAIC EQUATION SOLVERS

This paper presents some new techniques and tools for the formulation and implementation of transient response and trim problems. Acceleration terms in fuselage and rotor equations of motion can cause implementation problems, especially when blade flexibility and maneuvering flight are modeled. A technique based on the use of differential-algebraic equation solvers that eliminates this problem is presented. The general purpose DAE solver used in the study has algorithmic features that can make it superior and more efficient than existing techniques such as the Newmark-Beta method. Results illustrating the numerical properties of the algorithm are also presented. The paper shows how to reuse the subroutine that computes the “right-hand-side” of the system of equations to provide a free flight trim procedure. Two new trim procedures are presented that take advantage directly of the DAE solver. Advantages and disadvantages of these procedures are discussed.