Abstract: Two real time、large deviation mathematical models of an aeroengine are investigated to develop an airborne simulator,Full Authority Digital Electronic Control (FADEC) system.This study includes three parts:(a)to derive two mathematical models based on aerothermodynamics;(b)to estimate the engine performance by the method of digital simulation;(c)to dis cuss theoretical range of the calculated interval of the dynamic cycle and the model influenced by the fuel control regulation law.Two models are non linear、non iteration and full range.Simulation results show that the accuracy of models is quite good,and most relative errors are less than 3 percent,the biggest is about 5 percent.The calculated interval was reduced to 16ms(on the PC/AT with an Intel 80287 floating point coprocessor and C langu age programming).