Abstract: A process of applying the response surface method to get the ultimate state function (Which takes the characteris- tics of response surface function) is briefly depicted. A new method to analyze the reliability sensitivity through the ultimate state function is presented and the correlative formulas are de- duced. The advantages of this method are as follows: ① It is available even the ultimate state function is unknown. ② The ultimate state function, a simple quadric polynomial, is con- venient for calculating the variance, partial derivative and reli- ability sensitivity. ③ The function includes the information of linear, quadratic and crossing quadratic terms, which makes the accuracy of reliability sensitivity greatly improved. ④ Owning to its regularity, programming is achievable. Finally, the reli- ability of heat-emission of the accessory gearbox of aero-engine and reliability sensitivity of various influencing factors are cal- culated, which provides theoretical warranties for the designing of heat-emission system of accessory gearbox. The example shows these theories and formulas are rational and efficient.

Key words: Accessory gearbox, alysis, Box-Behnken sampling, Monte Carlo methods, Response surface method