Patent ID: 8447442

Claim:
A method for assisting in rejoining a vertical descent trajectory that an aircraft is assumed to have to follow, said method using a flight management system FMS embedded onboard the aircraft, comprising the following steps: calculation of a vertical deviation VDEV, in a vertical plane, between the aircraft and the vertical descent trajectory, comparison between the vertical deviation VDEV and a predetermined deviation threshold SVDEV, when the vertical deviation VDEV reaches the deviation threshold SVDEV, a step during which the activation of an optimized mode for catching up on the vertical descent trajectory is made possible, and if the optimized mode for catching up on the vertical descent trajectory is activated, piloting of the aircraft by the flight management system FMS in optimized catch-up mode, that is to say at minimum thrust with a target rejoining speed in level VCRP and a target rejoining speed in downward trajectory VCRD, the target rejoining speed in level VCRP being equal to the maximum L/D ratio speed of the aircraft uprated by a first value V 1 of between 5 and 15 knots, and the target rejoining speed in downward trajectory VCRD being equal to the maximum operating speed VMO with which the aircraft is allowed to fly downrated by a second value V 2 of between 3 and 10 knots, a knot being equal to 0.514 ms −1 .