At present

in respect of propellers of chinese commercial airplanes

stall flutter deserves extra attention.In our designing subsystem both empirical method and numerical simulation are employed for predicting the onset of stall flutter.In the empirical method

three nondimensional parameters at characteristic section of the propeller are used

i.e.reduced frequancy、inlet relative Mach number and incidence parameter.The numerical simulation is based on strip assumption.At the strip sections of a propeller

the transonic unsteady flow is considered to be induced by its oscillating blades.In calculation of aerodynamic damping

a simple engineering model is applied to considering the large scale region of flow separation at the blade suction surface.The results of numerical simulation for a new designed propeller are given.The variations of incidence and inlet relative Mach number at the characteristic section with aircraft flight velocity are shown in Fig.1 and 2.The dependence of the aerodynamic damping of the propeller on the incidence at the characteristic section in Fig.3 corresponds to the take off regime of the airplane.It is shown that there is no danger of the stall flutter onset in this case.The spanwise distribution of the incidence under the take off regime is also given in Fig.4.According to the whole flight envelope of the airplane

the greatest possibility of aeroelastic instability of the propeller corresponds to the ground static state of the airplane.At the ground static regime the incidence of the characteristic section is 9.96°.But the results of the numerical simulation show that there is no onset of the stall flutter in this case.This conclusion has been testified by the long term tests of the new designed propeller.