Patent Document ID: 10126756
Application ID: 14861610
Patent Flag: 1

Claim One:
1. A method for adapting an aircraft descent segment with constant ground gradient for optimizing said aircraft descent segment with respect to at least two performance criteria, executed by a flight management system, comprising: acquiring state variables characterizing the aircraft, environment variables characterizing the environment thereof and path variables characterizing a predicted path thereof at one of an initial and a final point of the aircraft descent segment; calculating at least two limit ground gradients for said at least two performance criteria from the said state variables, the said environment variables and the said path variables; validating the path initially predicted against a most restrictive limit ground gradient among said at least two limit ground gradients for at least two performance criteria; and when the path initially predicted is not valid: checking a feasibility of a command to modify at least one state variable; if feasibility is verified, predicting an execution of the said command; otherwise, predicting a modification of one of the initial and final points of the segment with respect to constraints of the flight plan; and at least one of the following further steps of: sending said aircraft descent segment to an automatic pilot or displaying said aircraft descent segment to a pilot, wherein the step of calculating at least two limit ground gradients for at least two performance criteria comprises calculating a limit air gradient for each of said at least two performance criteria, said step of calculating the limit air gradient comprising: calculating an engine thrust resultant; setting the limit air gradient to a default value; calculating an aerodynamic drag resultant as a function of the limit air gradient and the state variables of the aircraft; and calculating the limit air gradient as a function of the aerodynamic drag resultant, the aircraft state variables and the engine thrust resultant, said step of calculating the aerodynamic drag resultant and the step of calculating the limit air gradient being performed iteratively until a stop criterion is satisfied, said stop criterion being satisfied when an angular difference between the limit air gradient and a limit air gradient obtained in an immediately preceding iteration is, in absolute value, below a predefined threshold.