Method and device of terrain avoidance for an aircraft

1. A terrain avoidance method for an aircraft equipped with a collision alert device which monitors the flight of said aircraft with respect to the surrounding terrain and which is able to emit at least one alert, when said aircraft is at risk of colliding with the terrain while maintaining its current flight characteristics, according to which method a terrain avoidance maneuver is engaged when said collision alert device emits such an alert, the method comprising:

(a) establishing an altitude profile representative of said terrain overflown by said aircraft on the basis of at least one database characteristic of said terrain;

(b) measuring a plurality of parameters of said aircraft;

(c) on the basis of at least some of said measured parameters, determining at least one altitude limit curve which belongs to a vertical plane passing through the longitudinal axis of said aircraft and which lies, at least partially, in front of said aircraft, wherein said limit curve comprises at least one intersection with said terrain altitude profile at least upon the engagement of said terrain avoidance maneuver, and

wherein said at least one altitude limit curve consists of a series of segments comprising at least one horizontal segment, and said series of segments comprises an upward inclined segment, whose bottom end is connected to one of the ends of said horizontal segment and whose top end is oriented toward the sky;

(d) determining the inclination of said upward inclined segment, during step (c), as a function of the current climb capability of said aircraft;

(e) determining the length of said horizontal segment, during step (c), as a function of a terrain detection criterion which makes it possible to ensure that, when said avoidance maneuver is interrupted, said aircraft is at a minimum altitude allowing it to cross over the terrain situated in front of said aircraft;

(f) monitoring said intersection of the limit curve with the altitude profile;

(g) interrupting said terrain avoidance maneuver in the case where there is no intersection of said limit curve with said altitude profile; and

carrying out steps (b), (c), (d), (e), (f) and (g) in a successive and repetitive manner until said avoidance maneuver is interrupted.

2. The method as claimed in claim 1 ,

wherein said series of segments constituting said limit curve further comprises a downward inclined segment, the top end of said downward inclined segment is connected to said aircraft and the bottom end of said downward inclined segment is oriented toward the ground and connected to one of the ends of said horizontal segment, said downward inclined segment ensuring that, even if the aircraft is put into descent by the crew on an exiting maneuver, there is no reengagement of an automatic facility before a certain interlude.

3. The method as claimed in claim 1 ,

wherein said aircraft parameters measured during step (b) are selected from the group consisting of

the longitudinal speed of said aircraft;

the vertical speed of said aircraft;

the attitude of said aircraft;

the angle of attack of said aircraft; and

the altitude of said aircraft.

4. The method as claimed in claim 1 , further comprising:

emitting, during step (g), an information cue regarding absence of terrain prior to the interruption of said avoidance maneuver.

5. A terrain avoidance system for an aircraft, said system comprising:

a collision alert device which monitors the flight of said aircraft with respect to the surrounding terrain and emits at least one alert, when said aircraft is at risk of colliding with the terrain while maintaining its current flight characteristics;

an automatic piloting device that applies a terrain avoidance maneuver to said aircraft automatically when the at least one alert is emitted by said collision alert device;

an altitude profile establishment unit that establishes an altitude profile, representative of said terrain overflown by said aircraft, on the basis of at least one database characteristic of said terrain;

a parameter measurement unit that measures a plurality of parameters of said aircraft;

an altitude limit curve determination unit that determines, on the basis of at least one of said parameters measured by said measurement means, at least one altitude limit curve which belongs to a vertical plane passing through the longitudinal axis of said aircraft and which lies, at least partially, in front of said aircraft, said limit curve comprising at least one intersection with said altitude profile at least upon the engagement of said terrain avoidance maneuver;

a monitoring unit that monitors said intersection of the determined limit curve with the altitude profile; and

an interruption unit that interrupts said terrain avoidance maneuver, wherein the interruption unit is activated when there is no intersection of said limit curve with said altitude profile.

6. An aircraft,

comprising a terrain avoidance system of claim 5 .