Patent ID: 8340841

Claim:
A method for estimating an angle of attack and an angle of sideslip of an aircraft having a plurality of control surfaces, each control surface being adjustable with respect to an associated reference surface, the method comprising the steps of: measuring quantities representative of an angle formed by each control surface with respect to the associated reference surface; measuring an effective rolling speed, effective pitching speed and effective yawing speed of the aircraft; defining a linearized model of a state observer according to the following equation system: { x . = Ax + Bu + L ⁢ ⁢ δ ⁢ ⁢ y y = Cx + Du ⁢ wherein u is a vector containing the values of said quantities of each control surface, x is a vector comprising an estimated angle of attack, an estimated angle of sideslip, an estimated rolling speed, an estimated pitching speed and an estimated yawing speed, δy is an error vector comprising errors between the measured speeds and the respective estimated speeds, y is a measure vector comprising values of the measured speeds, A, B, C, D are matrices representative of a behavior of the aircraft in unperturbed motion and L is a feedback matrix comprising gains of a predetermined numeric control filter; and obtaining from the model the estimated angle of attack and the estimated angle of sideslip to use respectively as an actual angle of attack and an actual angle of sideslip of the aircraft.