A method for obtaining the inertial properties of a movable rotating around a hinge line in an aircraft control surface. The method includes the steps of removing the mechanical connections of the actuators from the movable, leaving the movable free to rotate around its hinge line, further balancing the movable and calculating in a first approach its coarse static moment. The method includes refining the coarse static moment and obtaining simultaneously a frictional moment of the movable; incorporating an elastic element on the control surface and configuring a second order mechanical system; inducing forced oscillations on the movable at a certain frequency, this frequency being increased until it is sensibly close to the resonance frequency of the movable to produce a wave response; calculating, from the wave response, the moment of inertia of the movable.