Method and device for piloting a pitching aircraft

1. A method of controlling of an aircraft in terms of pitch, according to which method the following series of successive steps is carried out, in an automatic and repetitive manner:

a) a controlled load factor NZc is taken into account;

b) a load factor NZcg applied to the aircraft is estimated;

c) a control command is calculated by taking into account at least the following main expression:

K1·NZc+K2·NZcg

K1 and K2 being two predetermined gain values; and

d) this control command is transmitted to a deflection means ( 5 ) of at least one rudder ( 7 ) of the aircraft, said deflection means ( 5 ) generating a deflection command representative of said control command and transmitting it to at least one actuator ( 9 ) of said rudder ( 7 ), wherein the following series of successive steps is carried out in addition, in an automatic and repetitive manner, before said step c):

the actual Mach number of the aircraft is determined;

the actual angle of incidence of the aircraft is determined;

said actual angle of incidence is compared to an angle-of-incidence reference value; and

if said actual angle of incidence is greater than said reference value, a modified gain value ΔK2 is determined with the aid of said actual Mach number and of said actual angle of incidence, said modified gain value ΔK2 replacing said gain value K2 in the calculation of said control command in said step c).

2. The method as claimed in claim 1 , wherein said reference value of the angle of incidence is determined with the aid of said actual Mach number.

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

a pitch rate q applied to the aircraft is estimated;

an integral INZ of the load factor applied to the aircraft is estimated; and

in step c), said control command is calculated by taking account, in said main expression, of the following auxiliary expression:

K3·q+K4·INZ

K3 and K4 being two predetermined gain values.

4. The method as claimed in claim 3 , wherein said modified gain value ΔK2 satisfies the following expression:

ΔK2[m·g·K5·(α−αO)/[S·Pdyn·Czα]

in which:

m is the mass of the aircraft;

g is the acceleration due to gravity;

K5 and Czα are two variable parameters, dependent on the actual Mach number;

α is said actual angle of incidence;

αO is said angle-of-incidence reference value;

S is a reference area of the aircraft wing; and

Pdyn is the dynamic pressure.

5. A device for controlling an aircraft in terms of pitch, said device ( 1 ) comprising:

means ( 4 ) for receiving a controlled load factor NZc;

means ( 11 ) for estimating a load factor NZcg applied to the aircraft; and

a calculation means ( 12 ) for calculating a control command by taking into account at least the following main expression:

K1·NZc+K2·NZcg

K1 and K2 being two predetermined gain values,

this control command being transmitted to a deflection means ( 5 ) of at least one rudder ( 7 ) of the aircraft, said deflection means ( 5 ) generating a deflection command representative of said control command and transmitting it to at least one actuator ( 9 ) of said rudder ( 7 ),

wherein said device ( 1 ) comprises in addition:

means ( 13 ) for determining the actual Mach number of the aircraft;

means ( 14 ) for determining the actual angle of incidence of the aircraft;

means ( 15 ) for comparing said actual angle of incidence to an angle-of-incidence reference value; and

means ( 16 ) for determining a modified gain value AK2 with the aid of said actual Mach number and of said actual angle of incidence if said actual angle of incidence is greater than said reference value, said modified gain value AK2 replacing said gain value K2 in

the calculation of said control command carried out by said calculation means ( 12 ).

6. The device as claimed in claim 5 , wherein:

said device ( 1 ) comprises in addition:

means ( 28 ) for estimating a pitch rate applied to the aircraft; and

means ( 29 ) for estimating an integral INZ of the load factor applied to the aircraft; and

said calculation means ( 12 ) is formed so as to calculate said control command by taking account, in said main expression, of the following auxiliary expression:

K3·q+K4·INZ

K3 and K4 being two predetermined gain values.

7. A system for controlling an aircraft, wherein it comprises:

a means ( 3 ) for generating a controlled load factor;

a control device ( 1 ) as specified in claim 5 , for determining a control command with the aid of said controlled load factor; and

a deflection means ( 5 ) which determines a deflection command for at least one rudder ( 7 ) of the aircraft with the aid of said control command and which transmits this deflection command at least one actuator( 9 ) of said rudder ( 7 ).

8. The system as claimed in claim 7 ,wherein said means ( 3 ) for generating a controlled load factor comprises an automatic pilot ( 18 ).

9. The system as claimed in claim 7 , wherein said means ( 3 ) for generating a controlled load factor comprises a control stick device ( 19 ).

10. The system as claimed in claim 7 , wherein said control device ( 1 ) is integrated within an automatic pilot.

11. An aircraft, comprising a device ( 1 ) capable of implementing the method specified in claim 1 .

12. An aircraft, comprising a device ( 1 ) such as that specified in claim 5 .

13. An aircraft, comprising a system such as that specified in claim 7 .