Method and device for assisting the flying of an aircraft during an autonomous approach

1. A method for assisting with flying an aircraft, the method comprising:

a) determining a line of approach; and

b) guiding the aircraft along said line of approach at least as far as a decision height using only components on board the aircraft,

wherein:

in step a):

a1) a main line of approach which is representative of a category 1 precision approach is determined; and

a2) a vertical correction is determined and, from this vertical correction and from said main line of approach, a corrected line of approach is determined which vertically exhibits a greater margin relative to the terrain being overflown than said main line of approach; and

in step b), said aircraft is guided along said corrected line of approach.

2. The method as claimed in claim 1 , wherein, in step a):

the gradient of said corrected line of approach is compared against an auxiliary gradient representing the maximum gradient that the aircraft can fly; and

if the gradient of said corrected line of approach is steeper than said auxiliary gradient, a message is emitted informing a pilot of the aircraft that the performance of said aircraft will not allow it to fly along said corrected line of approach.

3. The method as claimed in claim 1 , wherein a pilot of the aircraft is presented, on at least one display screen, with first and second indicators that show said main line of approach and said corrected line of approach, respectively.

4. The method as claimed in claim 1 , wherein in step a2) said vertical correction and said corrected line of approach are determined taking current aircraft performance into consideration.

5. The method as claimed in claim 4 , wherein in step a2) said corrected line of approach is determined using a gradient correction, the gradient P 2 of said corrected line of approach satisfying the following relationship:

P 2=arctan [( H ·tan P 0)/( H ·(tan P 0/tan P 1)−Δ H )]

in which:

tan denotes the tangent;

arctan denotes the inverse of the tangent;

P 0 denotes a gradient that defines a safety cone relative to a category 1 precision approach;

P 1 denotes the gradient of said main line of approach;

H denotes said decision height; and

ΔH denotes a vertical margin dependent on the current aircraft performance.

6. The method as claimed in claim 4 , wherein in step a2) said corrected line of approach is determined as being a line direction in which the aircraft is flying; and the horizontal translation ΔL of which satisfies the following relationship:

Δ L=ΔH /tan P 0

in which:

tan denotes the tangent;

ΔH denotes a vertical margin dependent on the current aircraft performance; and

P 0 denotes a gradient that defines a safety cone relative to a category 1 precision approach.

7. The method as claimed in claim 1 , wherein in step a2) said corrected line of approach is determined using a gradient correction, the gradient of said corrected line of approach corresponding to the gradient of said main line of approach increased by a predetermined gradient magnitude.

8. The method as claimed in claim 1 , wherein in step a2) said corrected line of approach is determined using a gradient correction, the gradient of said corrected line of approach corresponding to the gradient of said main line of approach multiplied by a predetermined value.

9. The method as claimed in claim 1 , wherein in step a2) said corrected line of approach is determined using a height correction of constant magnitude.

10. A device for assisting with flying an aircraft, said device comprising:

a flight control system for determining a line of approach; and

a guidance system for assisting with guiding the aircraft along said line of approach at least as far as a decision height, assisted solely by information available on board the aircraft,

wherein said flight control system comprises:

a first approach determining section that determines main line of approach which is representative of a category 1 precision approach; and

a second approach determining section that determines on the one hand, a vertical correction and, on the other hand, from this vertical correction and from said main line of approach, a corrected line of approach which vertically exhibits a greater margin relative to the terrain being overflown than said main line of approach, said corrected line of approach being transmitted to said guidance system so that it can assist with guiding the aircraft along this corrected line of approach.

11. The device as claimed in claim 10 , wherein it additionally comprises:

a monitoring section that compares the gradient of said corrected line of approach against an auxiliary gradient representing the maximum gradient that the aircraft can fly, wherein

if the gradient of said corrected line of approach is steeper than said auxiliary gradient, a message is emitted informing a pilot of the aircraft that the performance of said aircraft will not allow it to fly along said corrected line of approach.

12. The device as claimed in claim 10 , wherein it additionally comprises a display that presents a pilot of the aircraft, on at least one display screen, with first and second indicators that show said main line of approach and said corrected line of approach, respectively.

13. The device as claimed in claim 10 , wherein it additionally comprises an interface that allows a pilot to input at least one decision height value.

14. An aircraft comprising the device specified in claim 10 .