Method and device for estimating the mach number of an aircraft

1. A method for estimating the Mach number of an aircraft, comprising the following steps carried out in an automatic manner:

measuring a first static pressure Ps of the ambient air in a first measurement zone that is located on a fuselage of the aircraft;

measuring a second pressure P of the ambient air, via at least one static pressure probe, in a second measurement zone situated on the aircraft, said second pressure P having a value lower than the first static pressure Ps;

estimating a Mach number of the aircraft, using the following expression:

M

=

k

4

+

4

⁢

k

2

-

k

2

2

the parameter k bearing out the expression

k

=

Z

⁡

(

1

-

P

Ps

)

in which Z is a parameter dependent on the position of the second measurement zone on the aircraft; and

transmitting the estimated Mach number to a user system.

2. The method as claimed in claim 1 , wherein the second measurement zone is located on the fuselage of the aircraft, the parameter Z bearing out the following relationship

Z

=

2

Cpo

*

γ

in which Cpo is a constant pressure coefficient and γ is the adiabatic index of the air.

3. The method as claimed in claim 1 , wherein the second measurement zone is located in a nacelle of an engine of the aircraft, the parameter Z bearing out the following relationship Z=(aN1+b) in which a and b are constants determined empirically and N1 represents the speed of rotation of the fan of the engine.

4. The method as claimed in claim 1 , wherein the step of measuring a first status pressure comprises the following substeps:

measuring a first intermediate static pressure Ps′ and a second intermediate static pressure Ps″ in said first measurement zone, respectively, at a first intermediate measurement point and a second intermediate measurement point; and

estimating the first static pressure Ps by averaging the first and the second intermediate static pressures Ps′ and Ps″ measured in the preceding substep.

5. The method as claimed in claim 4 , wherein the first intermediate measurement point and the second intermediate measurement point are situated on the fuselage of the aircraft, respectively on either side of a longitudinal axis of the aircraft.

6. A device for estimating the Mach number of an aircraft, comprising:

a first measurement unit configured to measure a first static pressure Ps of ambient air in a first measurement zone of the aircraft that is located on a fuselage of the aircraft;

a second measurement unit configured to measure a second pressure P of the ambient air, by means of at least one static pressure probe, in a second measurement zone of the aircraft, the second pressure P having a value lower than the first static pressure Ps;

a computation unit configured to estimate a Mach number of the aircraft, using the following expression:

M

=

k

4

+

4

⁢

k

2

-

k

2

2

the parameter k bearing out the expression

k

=

Z

⁡

(

1

-

P

Ps

)

in which Z is a parameter dependent on the position of the second measurement zone on the aircraft; and

a data transmission unit configured to transmit the estimated Mach number to an user system.

7. An aircraft comprising a device for estimating the Mach number of an aircraft, the device comprising:

a first measurement unit configured to measure a first static pressure Ps of ambient air in a first measurement zone of the aircraft that is located on a fuselage of the aircraft;

a second measurement unit configured to measure a second pressure P of the ambient air, by means of at least one static pressure probe, in a second measurement zone of the aircraft, the second pressure P having a value lower than the first static pressure Ps;

a computation unit configured to estimate a Mach number of the aircraft, using the following expression:

M

=

k

4

+

4

⁢

k

2

-

k

2

2

the parameter k bearing out the expression

k

=

Z

⁡

(

1

-

P

Ps

)

in which L is a parameter dependent on the position of the second measurement zone on the aircraft; and

a data transmission unit configured to transmit the estimated Mach number to an user system.

8. The aircraft as claimed in claim 7 , wherein the first measurement unit comprises a first and a second measurement probe configured to measure a first intermediate static pressure Ps′ and a second intermediate static pressure Ps″, said first measurement unit further comprising a computer configured to determine the first static pressure Ps by averaging the first and the second intermediate static pressures Ps′ and Ps″.

9. The aircraft as claimed in claim 8 , wherein the first and the second measurement probes are positioned on the fuselage of the aircraft, on either side of a longitudinal axis of the aircraft.

10. A device for estimating the Mach number of an aircraft, the device comprising:

a first measurement unit configured to measure a first static pressure Ps of ambient air in a first measurement zone of the aircraft;

a second measurement unit configured to measure a second pressure P of the ambient air, by means of at least one static pressure probe, in a second measurement zone of the aircraft, the second pressure P having a value lower than the first static pressure Ps;

a computation unit configured to estimate a Mach number of the aircraft, using the following expression:

M

=

k

4

+

4

⁢

k

2

-

k

2

2

the parameter k bearing out the expression

k

=

Z

⁡

(

1

-

P

Ps

)

in which Z is a parameter dependent on the position of the second measurement zone on the aircraft; and

a data transmission unit configured to transmit the estimated Mach number to an user system;

wherein the first measurement unit comprises a first and a second measurement probe configured to measure a first intermediate static pressure Ps′ and a second intermediate static pressure Ps″, said first measurement unit further comprising a computer configured to determine the first static pressure Ps by averaging the first and the second intermediate static pressures Ps′ and Ps″; and

wherein the first and the second intermediate static pressures Ps′, Ps″ are measured on two respective faces of a vertical tail unit of the aircraft.