Abstract: A non-linear mathematical model for coaxial helicopter flight dynamics is established based on the development of a simplified and practical coaxial contra-rotating twin rotor loads model. The mathematical model is used tocalculate trims in steady straight level flight and dynamic responses to different control inputs for the sample coaxialhelicopter made in BUAA. The results of trim computation are well in agreement with the data provided from Russia. Numerical simulations show that the non-linear mathematical model captures the motion trend of the sample coaxial helicopter correctly. The correctness of models is preliminarily validated.

Key words: helicopter, coaxial helicopter, flight dynamics, rotor aerodynamics