The reliability of the main reducer drive system was acquired by dealing with the original load date of a typical mission profile of the helicopter

the load spectrum was changed into the stress spectrum of all gears using three-dimensional finite element analysis;the fatigue life of all gears at each load stage was calculated with Goodman formula and materials P-S-N curves

the life date was analyzed using Minitab.It's concluded that the contact fatigue life of gears is subject to Weibull distribution with two parameters

thus working out the reliability of each transmission part according to the reliability function of Weibull distribution and based on series-to-parallel reliability model of the system.Then

this thesis can provide a method for determining life and reliability of complex drive systems.