Landing assistance device and method for aircraft

1. A landing assistance method for an aircraft in approach phase located at a current height h and descending toward a runway following, with a current approach speed V, a current approach trajectory forming with said runway a current approach angle γ, said current approach speed V and said current approach angle γ ideally needing to be close, respectively, to a constant reference approach speed Vr and a constant reference approach angle γ associated with said runway,

wherein:

a range of approach speed values is predetermined, either side of said reference approach speed Vr, that will allow for a complete stoppage of said aircraft on said runway in the case where the current approach angle γ is at least approximately equal to said reference approach angle γr, said range of approach angles being delimited by

a lower limit value Vinf and by an upper limit value Vsup;

a range of approach angle values is predetermined, either side of said reference approach angle γr, that will allow for a complete stoppage of said aircraft on said runway in the case where the current approach speed V is at least approximately equal to the reference approach speed Vr, said range of approach angle values being delimited by a lower limit value γinf and by an upper limit value γsup;

there are calculated:

a lower total energy threshold Einf, corresponding to the situation for which the current approach speed V and the current approach angle γ are respectively equal to said lower limit value Vinf and said lower limit value γinf,

an upper total energy threshold Esup, corresponding to the situation for which the current approach speed V and the current approach angle γ are respectively equal to said upper limit value Vsup and said upper limit value γsup, and

the current total energy E of said aircraft; and

said current total energy E is compared with said lower Einf and upper Esup total energy thresholds to obtain an indication as to the theoretical possibility for said aircraft to stop on said runway.

2. The method as claimed in claim 1 , wherein, to carry out said comparison, an index I1 is calculated, by the expression:

I 1=( E−E inf)/( E sup− E inf).

3. The method as claimed in claim 1 , wherein:

a reference total energy Er is calculated that corresponds to the situation for which the approach speed and the approach angle are respectively equal to the reference approach speed Vr and the reference approach angle γr; and

said current total energy E and said reference total energy Er are compared, the result of this comparison being itself compared to at least one of said lower Einf and upper Esup total energy thresholds.

4. The method as claimed in claim 3 , wherein:

if E is greater than Er, E−Er can be compared to Esup−Er; and

if E is less than Er, Er−E can be compared to Er−Einf.

5. The method as claimed in claim 1 , wherein said lower Vinf and upper Vsup approach speed limit values are, preferably, at least approximately equal to said reference approach speed Vr, respectively minus and plus a few kts.

6. The method as claimed in claim 1 , wherein said lower γinf and upper γsup approach angle limit values are at least approximately equal to said reference approach angle γr, respectively minus and plus a few tenths of a degree.

7. The method as claimed in claim 1 , wherein the result of said comparison is displayed near to the pilot of the aircraft.

8. The method as claimed in claim 1 , wherein a prediction indication as to the complete stoppage of the aircraft on said runway is associated with said result of said comparison.

9. A device for implementing the method specified under claim 1 , wherein it comprises:

computation means:

receiving at least the information concerning the current mass m, the current height h, the current approach speed V and the current approach angle γ of the aircraft, and the lower speed limit value Vinf, the upper speed limit value Vsup, the lower approach angle limit value γinf and the upper approach angle limit value γsup and, where appropriate, the reference approach speed Vr and the reference approach angle γr; and

calculating at least one index, the value of which is representative of the fact that the level of said current total energy E of the aircraft is correct, excessive or deficient; and

comparison means comparing said index to at least one threshold value corresponding to a transition between a correct total energy level and an excessive or deficient total energy level, said comparison means being able to actuate at least one warning or alarm device, at least in the case where said current total energy level E of the aircraft is excessive or deficient.

10. The device as claimed in claim 9 , wherein at least one warning or alarm device comprises a standard piloting screen on which a warning or alarm message can be written concerning said current total energy level under the action of said comparison means.