Abstract: The optimization of the climb trajectory is of great importance due to the high percentage of fuel consumption during the climb section of a combined-cycle aircraft, and the safety of the power mode switching and the choice of switching time require urgent attention. However, the challenges of model nonlinearity, non-convex constraints and strong aircraft-engine coupling make the problem difficult to solve. Firstly, we establish a combined-cycle aircraft model that embodies the characteristic of aircraft-engine coupling. Secondly, in order to solve the problem efficiently, the updating rules of the chicken swarm optimization(CSO) are improved. Then the CSO is fused with the Gauss pseudospectral method to form a hybrid optimization algorithm. Finally, the correlation analysis between the fuel consumption during the climb segment and the key parameters of the aircraft is performed. The simulation results show that the Improved CSO-Gauss Pseudospectral Method achieves lower fuel consumption than either the CSO or the Gauss pseudospectral method. In addition, under the model of this paper, the climb segment fuel consumption is negatively correlated with the lift-to-drag ratio of the aircraft, and the selection of the power mode switching point also has a significant effect on the fuel consumption but does not show monotonicity.

Key words: Turbine-based combined-cycle engine, hypersonic vehicles, climb trajectory optimization, aircraft-engine coupling, optimization algorithm