Automatic flight control method for a rotorcraft enabling the rotorcraft to maintain a path by tracking manual flight controls

A method of using an automatic flight control system for arotorcraft having an autopilot that generates commands in predefined operating modes, the commands causing a modification to the behavior of the rotorcraft relative to at least one progression axis (P, R, V, Y), the rotorcraft having manual control members to cause a modification to the behavior of the rotorcraft relative to at least one progression axis (P, R, V, Y), the method comprising:

• performing by the autopilot a path-maintaining function including at least one guide mode (G) of the autopilot for guiding the rotorcraft relative to at least one of the progression axes (P, R, V, Y) of the rotorcraft, in which the path-maintaining function includes receiving an acquisition request for a person to acquire at least one path setpoint defined by at least one flight parameter, each path setpoint relating to said at least one guide mode (G);
• as a result of the person driving at least one manual control member to cause a modification to the behavior of the rotorcraft relative to at least one progression axis(P, R, V, Y), generating by the autopilot:
• an inhibit command whereby the autopilot inhibits said at least one guide mode (G) of the rotorcraft for which the acquisition request has been issued and relating to said at least one progression axis relative to which the behavior of the rotorcraft is being modified by the person;
• and
• an acquisition command whereby the autopilot acquires an acquired value of at least one flight parameter relating to each path setpoint to be acquired and applicable to at least one progression axis from which the behavior of the rotorcraft is being modified by the person, the acquired value being acquired when said movement applied for driving the manual control member is interrupted, and the acquired value replacing the value of the at least one flight parameter acquired by the autopilot prior to the acquisition command;
• the path setpoints relating to the other guide modes (G) that have continued to be engaged and that relate to other progression axes (P, R, V, Y) being maintained in their states prior to said at least one manual control member being driven, and the commands generated by the autopilot relating to all of the progression axes that continue to be engaged being adapted by the autopilot depending on the current state of progression of the rotorcraft on the basis of said maintained path setpoints and on the basis of the acquired value of the at least one flight parameter for which said acquisition command was issued.

An automatic flight control system for a rotorcraft, the rotorcraft having manual control members to be driven by a person to cause a modification to the behavior of the rotorcraft relative to at least one progression axe (P, R, V, Y) including pitching (P), roll (R), verticality (V), and yaw (Y), the automatic flight control system comprising:

• a memory for storing flight setpoints relative to each of the progression axes;
• onboard instrumentation for evaluating an actual state of progression of the rotorcraft;
• and
• an autopilot that generates commands in predefined operating modes, the commands causing a modification to the behavior of the rotorcraft relative to at least one progression axis (P, R, V, Y);
• wherein the autopilot incorporates a multiple choice control member to select at least one path-maintaining function including at least one guide mode (G) for guiding the rotorcraft relative to at least one of the progression axes (P, R, V, Y);
• wherein the autopilot includes for the path-maintaining function a detector for acquiring at least one path setpoint defined by at least one flight parameter and to detect driving movements of a manual control member for acquiring the path setpoint when the manual control member is being driven by a person, the path setpoint relating to the guide mode (G) so that as a result of the person driving the manual control member to cause a modification to the behavior of the rotorcraft relative to one of the progression axes (P, R, V, Y), the autopilot generates:
• an inhibit command whereby the autopilot inhibits the guide mode (G) of the rotorcraft for which the acquisition has been issued and relating to the progression axis relative to which the behavior of the rotorcraft is being modified by the person;
• and
• an acquisition command whereby the autopilot acquires a value of the flight parameter relating to the path setpoint to be acquired and applicable to the progression axis from which the behavior of the rotorcraft is being modified by the person, the value of the flight parameter being acquired from the onboard instrumentation evaluating the actual state of progression of the rotorcraft, and upon the driving of the manual control member being interrupted, an other value of the flight parameter takes the place of the value of the flight parameter that was acquired, the other value being derived from the flight setpoints stored in the memory prior to the inhibit command;
• wherein the autopilot maintains the values of the path setpoints relating to the other guide modes (G) that have continued to be engaged and that relate to other progression axes (P, R, V, Y) prior to said person moving said manual control member, the commands generated by the autopilot relating to all of the progression axes that continue to be engaged being adapted by the autopilot depending on the current state of progression of the rotorcraft on the basis of said maintained path setpoints and on the basis of the value of the flight parameter for which said acquisition request was issued.