The helicopter main gearbox was taken as the research object

the finite-element/lumped-parameter hybrid method was used to establish a hybrid dynamic model of a helicopter main gearbox

by considering the flexibility of the shaft and housing. The specific influence of the flexible housing structure on the vibration characteristics of the main gearbox was studied. Results demonstrated that

after considering the structure of the flexible housing

the natural frequency of each order was significantly decreased

the mode shape of the system was changed obviously

and the amplitude of the resonance peak of the system was decreased and the number of resonance speed was reduced. The flexible housing structure had little influence on the dynamic meshing force

but had a greater impact on the bearing reaction force. It can be divided into three categories: the fluctuation amplitude decreases

basically remains unchanged and increases

and the judgment criteria were given. The results lay a foundation for the vibration reduction

noise reduction and dynamic performance optimization of the helicopter main gearbox.