Method and device for activating an automatic piloting mode of an aircraft

1. A method for automatically engaging, upon a landing, an automatic pilot mode of an aircraft (AC) comprising an automatic pilot, able to control the trajectory (T) of said aircraft (AC), and at least an altimeter ( 1 ), able to determine the current height (H c ) of said aircraft (AC), said method comprising:

A/ estimating the current distance (d) separating said aircraft (AC) from a reference position on the ground (O);

B/ determining from a reference height (H réf ) associated to said automatic pilot mode and the current slope (γ) of said trajectory (T), a range of distances (I) with respect to said reference position (O), for automatically engaging said mode;

C/ checking whether said current distance (d) belongs to said determined engagement range (I);

D/ checking whether said current height (H c ) is at the most equal to said reference height (H réf ); and

E/ when said current distance (d) belongs to said determined engagement range (I) and said current height (H c ) is at the most equal to said reference height (H réf ), automatically engaging said automatic pilot mode,

wherein a minimum slope (γ min ) and a maximum slope (γ max ) are defined, surrounding said current slope (γ); and

a minimum border (d min ) and a maximum border (d max ) of said engagement range (I) are determined respectively from formulae

H

réf

tan

⁢

⁢

γ

max

⁢

⁢

and

⁢

⁢

H

réf

tan

⁢

⁢

γ

min

,

wherein:

H réf represents said reference height; and

γ min and γ max respectively correspond to said minimum slope and to said maximum slope.

2. A method according to claim 1 , wherein said current distance (d) separating said aircraft (AC) from said reference position (O) corresponds to the distance between an orthogonal projection (M) of said aircraft (AC) on a horizontal plane (P) crossed by said reference position (O) and the latter.

3. A method according to claim 1 , wherein, in step A, estimating said current distance (d) is made from geographical data, of a GPS type.

4. A method according to claim 1 , said aircraft (AC) comprising inertial units ( 2 ), wherein, when said aircraft (AC) is stabilized, said current slope (γ) is determined from said inertial units ( 2 ).

5. A method according to claim 1 , wherein said current slope (γ) is determined from:

either a data base on board said aircraft (AC);

or data from ground facilities, received by said aircraft (AC).

6. A method according to claim 1 , wherein a warning is emitted to the crew of said aircraft (AC) when at least one of the following flight situations is checked:

said current distance (d) does not belong to said determined engagement range (I), whereas said current height (H c ) is at the most equal to said reference height (H réf );

said current distance (d) belongs to said determined engagement range whereas said current height (H c ) is strictly higher than said reference height (H réf ).

7. A method for automatically engaging, upon a landing, an automatic pilot mode of an aircraft (AC) comprising an automatic pilot, able to control the trajectory (T) of said aircraft (AC), and at least an altimeter ( 1 ), able to determine the current height (H c ) of said aircraft (AC) said method comprising:

A/ estimating the current distance (d) separating said aircraft (AC) from a reference position on the ground (O);

B/ determining from a reference height (H réf ) associated to said automatic pilot mode and the current slope (γ) of said trajectory (T), a range of distances (I) with respect to said reference position (O), for automatically engaging said mode;

C/ checking whether said current distance (d) belongs to said determined engagement range (I);

D/ checking whether said current height (H c ) is at the most equal to said reference height (H réf ); and

E/ when said current distance (d) belongs to said determined engagement range (I) and said current height (H c ) is at the most equal to said reference height (H réf ), automatically engaging said automatic pilot mode,

wherein a margin (M(H réf , γ)) is defined as a function of said reference height (H réf ) and of said current slope (γ); and

a minimum border (d min ) and a maximum border (d max ) of said engagement range (I) are determined respectively from formulae

H

r

⁢

e

¸

⁢

f

tan

⁢

⁢

γ

-

M

⁡

(

H

r

⁢

e

¸

⁢

f

,

⁢

γ

)

⁢

⁢

and

⁢

⁢

H

r

⁢

e

¸

⁢

f

tan

⁢

⁢

γ

+

M

⁡

(

H

r

⁢

e

¸

⁢

f

,

⁢

γ

)

,

wherein:

H réf represents said reference height;

γ corresponds to said current slope; and

M(H réf , γ) represents said margin.

8. A device for automatically engaging, upon a landing, an automatic pilot mode of an aircraft (AC) comprising: an automatic pilot, able to control the trajectory (T) of said aircraft (AC), and at least one altimeter ( 1 ), able to determine the current height (H c ) of said aircraft (AC), said device comprising:

means ( 8 ) for estimating the current distance (d) separating said aircraft (AC) from a reference position on the ground (O);

means ( 9 ) for determining, from a reference height (H réf ) associated to said automatic pilot mode and a current slope (γ) of said trajectory (T), a range of distances (I), with respect to said reference position (O), for automatically engaging said mode;

means ( 11 ) for checking that said current distance (d) belongs to said determined engagement range (I);

means ( 12 ) for checking that said current height (H c ) is at the most equal to said reference height (H réf ); and

means ( 13 ) for automatically initiating said automatic pilot mode, able to be activated when said current distance (d) belongs to said determined engagement range (I) and that said current height (H c ) is at the most equal to said reference height (H réf )

wherein a minimum slope (γ min ) maximum slope (γ max ) are defined, surrounding said current slope (γ); and

a minimum border (d min ) and a maximum border (d max ) of said engagement range (I) are determined respectively from formulae

H

réf

tan

⁢

⁢

γ

max

⁢

⁢

and

⁢

⁢

H

réf

tan

⁢

⁢

γ

min

,

wherein:

H réf represents said reference height; and

γ min and γ max respectively correspond to said minimum sloe and to said maximum slope.

9. An aircraft (AC), comprising an automatic pilot, able to control the trajectory (T) of said aircraft (AC), and at least one altimeter ( 1 ), able to determine the current height (H) of said aircraft (AC), including the device for automatically engaging, upon a landing, an automatic pilot mode of the aircraft as specified in claim 8 .