Large Civil Aircraft Nonlinear Flight Dynamics Iteration Trim Method Based on the Downhill Simplex Optimization Algorithm

Aircraft flight dynamics trim is the basis for the large civil aircraft flight dynamics characteristics analysis. In this paper, the full nonlinear flight dynamics model of civil aircraft is systematically deduced, an iterative trim method for the six-degree-of-freedom flight dynamics model based on the Downhill Simplex optimization algorithm is designed, and the trim accuracy and computational efficiency of the Downhill Simplex optimization algorithm are analyzed and the variation of trim variables under different initial weights is studied. Results show that the Downhill Simplex optimization algorithm can effectively solve the six-degree-of-freedom full nonlinear aerodynamics trim problem of large civil aircraft under the condition of straight forward and level flight, and the trim deviation can be controlled within the range of ±0.05N/Nm within 500 steps. The flight dynamics iterative trim method based on the Downhill Simplex optimization algorithm designed in this paper can provide reference and technical support for civil aircraft flight simulation, flight dynamics characteristics and flight quality research.