Patent ID: 7907066

Claim:
A method of detecting and signaling the approach of a vortex domain by a rotorcraft of a particular type of rotorcraft, wherein the following steps are performed in succession: a) making a series of prior measurements on a reference rotorcraft of the particular type of rotorcraft during preliminary flights by measuring a plurality of pairs of values relating to the tangential and normal components of the speed of the flow of air relative to the plane of the rotor, these pairs of values determining at least one instantaneous vortex representative of a vortex state by means of at least one diagram in which the abscissa axis and the ordinate axis correspond respectively to said tangential and normal components; b) during flight of a rotorcraft of said particular type of rotorcraft, determining in real time a predictive proper airspeed V PP of said rotorcraft and an associated predictive vertical speed v AP ; c) defining a first detection condition specifying when said associated predictive proper airspeed V PP and predictive vertical speed v AP are included in the instantaneous vortex domain; and d) triggering a signaling alarm when said first detection condition is satisfied; and wherein the predictive proper airspeed V PP is determined by means of the following relationship in which t and □t designate respectively time and a time interval: V PP = V P + ⅆ V P ⅆ t ⁢ • ⁢ ⁢ t the predictive vertical speed v AP being calculated by performing the following additional steps: b1) measuring the instantaneous vertical speed V of the rotorcraft; b2) determining a corrective vertical speed v CORR depending on a predictive term; and b3) adding the corrective vertical speed to the instantaneous vertical speed to obtain said predictive vertical speed v AP ; said predictive term applicable to the instantaneous vertical speed v being determined during a step b21) from the following equation: C P ⁢ ⁢ 1 = ( v + k ) ⁢ V PP - V P 2 ⁢ V Y - V PP with: V P =the instantaneous proper airspeed of the rotorcraft of a given type of rotorcraft; V Y =the predetermined minimum-power speed of the rotorcraft of a given type of rotorcraft; and k=a characteristic coefficient predetermined for the rotorcraft of a given type of rotorcraft; providing the following two conditions are satisfied: the calibrated airspeed VC in level flight is less than the minimum-power speed V Y ; and the calibrated airspeed VC is decreasing.