Off-path descent guidance by a flight management system

Claim 1

A method for providing off-path descent vertical guidance of an aircraft by a Flight Management System (FMS), comprising the steps of: a) determining a current altitude (H) and a corresponding current horizontal distance (X) of the aircraft from a predetermined bottom of descent point (B/D); b) determining if X is less than a predetermined distance X s ; c) if X is less than X s performing a flight simulation of basic descent to produce a Basic Descent Path (BDP) starting at X, otherwise performing a descent simulation starting at a point where X is at or near X s and using aircraft state data obtained from a previous flight plan prediction cycle; d) storing a plurality of points, each of which corresponds to an altitude (H i ) and horizontal distance (X i ) in a basic descent path array of the BDP obtained from the flight simulation; e) determining a horizontal distance (X B ) from the B/D point to a bottom point of the BDP array; f) determining a horizontal distance (X A ) in the BDP array that corresponds to the current aircraft altitude; g) subtracting X B from X A , thereby obtaining a radius around the B/D point of a BDP Circle and displaying this circle on the ND (Navigation Display) unit; and h) displaying an aircraft symbol on the ND unit at a distance proportional to X A from the B/D point, thereby indicating the distance remaining until to start of descent of the aircraft.

Claim 2

A method for providing off-path descent vertical guidance of an aircraft by a Flight Management System (FMS), comprising the steps of: a) determining a current altitude (H) and a corresponding current horizontal distance (X) of the aircraft from a predetermined bottom of descent point (B/D); b) determining if X is less than a predetermined distance X s ; c) if X is less than X s performing a flight simulation of basic descent to produce a Basic Descent Path (BDP) starting at X, otherwise performing a descent simulation starting at a point where X is at or near X s and using aircraft state data obtained from a previous flight plan prediction cycle; d) storing a plurality of points, each of which corresponds to an altitude (H i ) and horizontal distance (X i ) in a basic descent path array of the BDP obtained from the flight simulation; e) determining a horizontal distance (X B ) from the B/D point to a bottom point of the BDP array; f) determining a horizontal distance (X A ) in the BDP array that corresponds to the current aircraft altitude; g) subtracting X B from X A , thereby obtaining a radius around the B/D point of a BDP Circle and displaying this circle on the ND (Navigation Display) unit; and h) displaying an aircraft symbol on the ND unit at a distance proportional to X A from the B/D point, thereby indicating the distance remaining until to start of descent of the aircraft.