# US 9,753,052 B2 · Method and device for estimating the mach number of an aircraft

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- Number: US 9,753,052 B2
- Document ID: US9753052B2
- Status: Granted
- Kind: B2
- Application number: 14/805,131
- Filed: 2015-07-21
- Published: 2016-01-28
- Granted: 2017-09-05
- Earliest claimed: 2014-07-23
- Assignees: Airbus Operations GmbH
- Applicants: Airbus Operations (SAS)
- Inventors: Maxime Semat; Martin Delporte
- Web page: https://patentgrep.com/patent/US9753052B2

## CPC

- G01P 5/175: with the determination of Mach number (analogue computers therefor G06G7/57)
- G01P 5/14: by measuring differences of pressure in the fluid
- G01P 13/025: {indicating air data, i.e. flight variables of an aircraft, e.g. angle of attack, side slip, shear, yaw}
- G01P: MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT (measuring or recording blood flow A61B5/02, A61B8/06; monitoring speed or deceleration of electrically-propelled vehicles B60L3/00; vehicle lighting systems adapted to indicate speed B60Q1/54; determining position or course in navigation, measuring ground distance in geodesy or surveying G01C; combined measuring devices for measuring two or more variables of movement G01C23/00; measuring velocity of sound G01H; measuring velocity of light G01J7/00; measuring direction or velocity of solid objects by reception or emission of radiowaves or other waves and based on propagation effects, e.g. Doppler effect, propagation time, direction of propagation, G01S; measuring speed of nuclear radiation G01T; measuring acceleration of gravity G01V; {measuring or recording the speed of trains B61L23/00; speed indicators incorporated in motor vehicles B60K35/00; measuring frequency or phase G01R; traffic control G08G})

## Abstract

A measurement unit for measuring a first static pressure of the ambient air in a first measurement zone of the aircraft, a measurement unit for measuring a second pressure of the ambient air, at least one static pressure probe, in a second measurement zone of the aircraft, the second pressure having a value lower than the first static pressure, a computation unit for estimating a Mach number using these two measured pressures and a data transmission unit configured to transmit the estimated Mach number to a user system.

## Claims

### Claim 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.

### Claim 2 (depends on 1)

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.

### Claim 3 (depends on 1)

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.

### Claim 4 (depends on 1)

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.

### Claim 5 (depends on 4)

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.

### Claim 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.

### Claim 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.

### Claim 8 (depends on 7)

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″.

### Claim 9 (depends on 8)

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.

### Claim 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.