Method and device for preventing useless alarms generated by an anti-collision system on board an airplane

1. A method for limiting alerts emitted by an anticollision system on board an airplane which performs a change-of-altitude maneuver, wherein the change-of-altitude maneuver of the airplane is carried out during a flight trajectory of the airplane in which the flight trajectory comprises an approach phase followed by a capture phase, with the flight trajectory having a setpoint altitude (Zc) and the capture phase having a predetermined setpoint execution deadline, the method comprising the steps of:

detecting, by said anticollision system, an intruder aircraft situated in an aerial environment of said airplane;

calculating a theoretical time for collision between said airplane and said intruder aircraft; and

emitting at least one alert when the calculated theoretical collision time is less than a predetermined threshold,

wherein the following steps are additionally carried out by an alert limiting device:

A) determining a minimum execution deadline (dmin) and a maximum execution deadline (dmax) of said capture phase, said minimum execution deadline (dmin) being greater than said predetermined setpoint execution deadline;

B) calculating at least one modified vertical speed profile of said altitude capture phase, wherein the at least one modified speed profile provides for a flight duration (dcap) in the altitude capture phase of the flight trajectory that is between said minimum (dmin) and maximum (dmax) execution deadlines;

C) triggering, when said airplane is in the approach phase, said capture phase; and

D) controlling, after said capture phase is triggered, vertical speed of said airplane according to said calculated modified vertical speed profile.

2. The method as claimed in claim 1 ,

further comprising the steps of:

calculating an engagement altitude level (Ze) for said capture phase; and

triggering the capture phase when the current altitude level of said airplane is between said engagement altitude level (Ze) and said setpoint altitude (Zc).

3. The method as claimed in claim 2 , wherein said engagement altitude level (Ze) is determined according to the following formula:

Ze=a− ( S i +T )* Vzo

in which:

Vzo is a substantially constant vertical speed of said airplane in the course of said approach phase;

a is an adjustment parameter dependent on said minimum (dmin) and maximum (dmax) execution deadlines;

S i is said predetermined threshold; and

T is a positive temporal margin with respect to said predetermined threshold S i .

4. The method as claimed in claim 1 ,

wherein, during the capture phase, said control of the vertical speed of said airplane is performed by controlling a load factor of said airplane defined according to the following formula:

nz=k *( Vz−f ( Z ))

in which:

nz is the load factor of said airplane in capture phase;

k is a negative constant dependent on physical characteristics of said airplane;

Vz is the vertical speed of said airplane; and

f represents said modified vertical speed profile as a function of a current altitude level Z of said airplane with respect to said setpoint altitude (Zc).

5. The method as claimed in claim 1 ,

wherein,

said control of the vertical speed of said airplane is controlled by controlling, prior to reaching said set point altitude (Zc) and after exiry of said maximum execution deadline (dmax), a load factor of said airplane according to the following formula:

nz=k 1 *Z+k 2 *Vz

in which:

nz is the load factor of said airplane in the course of said capture phase;

k 1 and k 2 are negative constants dependent on the physical characteristics of said airplane;

Vz is the vertical speed of said airplane; and

Z is the current altitude level of said airplane with respect to said setpoint altitude (Zc).

6. The method as claimed in claim 1 ,

wherein said modified vertical speed profile comprises a first part comprised of an exponential trajectory of said airplane, followed by a second part comprised of a parabolic trajectory of said airplane.

7. The method as claimed in claim 6 ,

wherein said first part of said modified vertical speed profile is carried out according to the following function:

f 1( Z )=( a−Z )/( S i +T )

in which:

a is an adjustment parameter dependent on said minimum (dmin) and maximum (dmax) execution deadlines;

Z is a current altitude level of said airplane (AC) with respect to said setpoint altitude (Zc);

S i is said predetermined threshold; and

T is a positive temporal margin with respect to said predetermined threshold S i .

8. The method as claimed in claim 7 ,

wherein said second part of said modified vertical speed profile is carried out according to the following function:

f 2( Z )=√{square root over (()}α*0.1 g*Z )

in which:

α is a constant equal to −1 when said airplane is in a climb phase and equal to 1 when said airplane is in a descent phase;

g is a terrestrial gravitational constant; and

Z is the current altitude level of said airplane with respect to said setpoint altitude (Zc).

9. An alert limiting device for limiting alerts emitted by an anticollision system on board an airplane which performs a change-of-altitude maneuver, wherein the change-of-altitude maneuver of the airplane is carried out during a flight trajectory of the airplane in which the flight trajectory comprises an approach phase followed by a capture phase, with the flight trajectory having a setpoint altitude (Zc) and a predetermined setpoint execution deadline for the capture phase,

wherein said anticollision system is configured:

to detect an intruder aircraft situated in an aerial environment of said airplane,

to calculate a theoretical time for collision between said airplane and said intruder aircraft and

to emit at least one alert when the calculated theoretical collision time is less than a predetermined threshold,

which device comprises:

determination unit configured to determine at least one modified vertical speed profile of said altitude capture phase, wherein the at least one modified vertical speed profile provides for a flight duration (dcap) in the altitude capture phase of the flight trajectory that is between a predetermined minimum execution deadline (dmin) and a predetermined maximum execution deadline (dmax);

activatable control unit configured to engage said altitude capture phase and to control vertical speed of said airplane according to said modified vertical speed profile; and

activation unit configured to activate said activatable control unit when said airplane is in the approach phase.

10. An airplane,

which comprises the device of claim 9 .