Abstract: A mathematical model of the coupling disturbance for mechanical control system and servo-mechanism is established by the linear theory.This paper concludes that the origin of pro-ducing the coupling disturbance is made by the mass ofrear stick line mostly.Then a structure fil-ter of reducing the coupling disturbance level is proposed,and digital simulation is made for some aircraft system with the filter. The digital results show that it agrees well with the experi-ment and the proposed theory analysis is correct.

Key words: coupling, airfoil oscillations, structural vibration