The invention relates to a method of preparing a fluorinated copolymer, comprising a step of copolymerization of a fluorinated monomer with an \u03b1-trifluoromethacrylic acid monomer or derivative of \u03b1-trifluoromethacrylic acid, in the presence of a xanthate or trithiocarbonate compound. Input information associated with the aircraft and operations associated therewith, are provided and detected. A signal selecting unit selects the output of the first low pass filter when the control process demands prompt detection of an abrupt changes in the behavior of the vehicle and the output of the second low pass filter when it is not the case and an enhanced stability of the control action has a priority.