System and method for computing mach number and true airspeed

• US 8,914,164 B1
• Filed: 08/02/2013
• Issued: 12/16/2014
• Est. Priority Date: 08/02/2013
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Nathan, Visvanathan Thanigai, Anandappan, Thanga
• Primary Examiner(s): FREJD, RUSSELL WARREN
• Application Number:
  US13/958,307
• Time in Patent Office: 501 Days
• Field of Search: 701/3, 701/4, 701/7, 701/14, 702/144, 734/88, 324/161
• US Class Current: 701/7
• CPC Class Codes: B64D 43/02 for indicating aircraft speed or stalling conditions
• CPC Class Codes: G01C 23/00 Combined instruments indicating more than one navigational value, e.g. for aircraft; Combined measuring devices for measuring two or more variables of movement, e.g. distance, speed or acceleration
• CPC Class Codes: G01P 13/025 indicating air data, i.e. flight variables of an aircraft, e.g. angle of attack, side slip, shear, yaw
• CPC Class Codes: G01P 21/00 Testing or calibrating of apparatus or devices covered by the preceding groups
• CPC Class Codes: G01P 21/025 for measuring speed of fluids; for measuring speed of bodies relative to fluids for measuring volume flow G01F25/10
• CPC Class Codes: G01P 3/50 for measuring linear speed G01P3/56 takes precedence
• CPC Class Codes: G01P 3/62 Devices characterised by the determination or the variation of atmospheric pressure with height to measure the vertical components of speed measuring pressure in general G01L
• CPC Class Codes: G01P 5/16 using Pitot tubes , e.g. Machmeter
• CPC Class Codes: G01P 5/175 with the determination of Mach number analogue computers therefor G06G7/57

Abstract

A system and method are provided for calculating Mach number and true airspeed without reference to data from a pitot static sensor. The true airspeed and Mach number are calculated using the altitude information from GPS, IRS, Radio Altimeter and other onboard sensors other than the air data computer (ADC). The computed true airspeed or Mach number could be used to confirm the ADC information or in lieu of the ADC information when the ADC information is unreliable or unavailable.

Claims

1. A method for determining at least one of a first true airspeed or a first Mach number of an aircraft in flight, comprising:

sensing an air velocity and a first altitude by a pitot static sensor;

providing at least one of a second true airspeed and a second Mach number by an air data computer coupled to the pitot static sensor and in response to the air velocity and the first altitude;

storing within a storage medium standard atmospheric data, thrust data, wing surface area, and a coefficient of lift for the aircraft;

determining by a flight management system a load factor and a weight of the aircraft;

determining a second altitude by an altitude sensor;

determining an angle of attack by a sensor on the aircraft;

sensing a temperature of the air adjacent the aircraft; and

determining, from the group consisting of the standard atmospheric data, the thrust data, the wing surface area, the coefficient of lift, the load factor, the weight, the second altitude, the temperature, and the angle of attack, at least one of the first true airspeed or first Mach number, by a processor coupled to the storage medium, the flight management system, the altitude sensor, and the temperature sensor.

2. The method of claim 1 further comprising determining an air density from the standard atmospheric data, temperature, and the second altitude, and wherein determining the first true airspeed comprises determining by the equation V²=(n*mg−

T sin α

)/(½

ρ

SCza), where V² is the first true airspeed squared, n is the load factor, mg is the weight, ρ

is the air density, S is the wing surface area, Cza is the coefficient of lift, and T is the thrust, and α

is the angle of attack.

3. The method of claim 1 further comprising determining an ambient pressure from the standard atmospheric data, and wherein determining the first Mach number comprises determining by the equation M²=(n*mg−

T sin α

)/(0.7SPaCza), where M² is the first Mach number squared, n is the load factor, mg is the weight, S is the wing surface area, Pa is the ambient air pressure, Cza is the coefficient of lift, T is the thrust, and α

is the angle of attack.

4. The method of claim 1 wherein determining a second altitude consists of determining the second altitude by one of a global positioning system, an inertial reference system, or a radio altimeter.

5. The method of claim 1 wherein determining the load factor and the weight is determined by the flight management system.

6. A method of determining at least one of a true airspeed or a Mach number of an aircraft in flight, comprising:

storing within a storage medium standard atmospheric data, thrust data, wing surface area, and a coefficient of lift for the aircraft;

determining by a flight management system a load factor and a weight of the aircraft;

determining an altitude by an altitude sensor;

determining an angle of attack by a sensor on the aircraft;

sensing a temperature of the air adjacent the aircraft; and

determining, from the group consisting of the standard atmospheric data, the thrust data, the wing surface area, the coefficient of lift, the load factor, the weight, the altitude, the temperature, and the angle of attack, the true airspeed or the Mach number, by a processor coupled to the storage medium, the flight management system, the altitude sensor, and the temperature sensor.

7. The method of claim 6 further comprising determining an air density from the standard atmospheric data, temperature, and the second altitude, and wherein determining the first true airspeed comprises determining by the equation V²=(n*mg−

T sin α

)/(½

ρ

SCza), where V² is the first true airspeed squared, n is the load factor, mg is the weight, ρ

is the air density, S is the wing surface area, Cza is the coefficient of lift, and T is the thrust, and α

is the angle of attack.

8. The method of claim 6 further comprising determining an ambient pressure from the standard atmospheric data, and wherein determining the first Mach number comprises determining by the equation M²=(n*mg−

T sin α

)/(0.7SPaCza), where M² is the first Mach number squared, n is the load factor, mg is the weight, S is the wing surface area, Pa is the ambient air pressure, Cza is the coefficient of lift, T is the thrust, and α

is the angle of attack.

9. The method of claim 6 wherein determining a second altitude consists of determining the second altitude by one of a global positioning system, an inertial reference system, or a radio altimeter.

10. The method of claim 6 wherein determining the load factor and the weight is determined by the flight management system.

11. A system for determining at least one of a first true airspeed or a first Mach number of an aircraft in flight, the system comprising:

a pitot static sensor configured to sense an air velocity and a first altitude;

an air data computer coupled to the pitot static sensor and configured to provide at least one of a second true airspeed and a second Mach number;

a storage medium configured to store standard atmospheric data, thrust data, wing surface area, and a coefficient of lift for the aircraft;

a flight management system configured to determine a load factor and a weight of the aircraft;

an altitude sensor configured to determine a second altitude;

a temperature sensor configured to determine a temperature;

a sensor configured to determine an angle of attack; and

a processor coupled to the storage medium, the flight management system, the altitude sensor, and the temperature sensor, and configured to determine, from the group consisting of the standard atmospheric data, the thrust data, the wing surface area, the coefficient of lift, the load factor, the weight, the second altitude, the temperature, and an angle of attack, at least one of the first true airspeed or first Mach number.

12. The system of claim 11 wherein the flight management system is coupled to the air data computer and is further configured to:

determine a difference between one of the first true airspeed or the first Mach number and one of the second true airspeed or the second Mach number, respectively;

determine at least one of the second true airspeed and the second Mach number as valid when the difference does not exceed a threshold; and

determine at least one of the first true airspeed and the first Mach number as valid when the difference exceeds the threshold.

13. The system of claim 11 further comprising determining an air density from the standard atmospheric data, temperature, and the second altitude, and wherein determining the first true airspeed comprises determining by the equation V²=(n*mg−

T sin α

)/(½

ρ

SCza), where V² is the first true airspeed squared, n is the load factor, mg is the weight, ρ

is the air density, S is the wing surface area, Cza is the coefficient of lift, and T is the thrust, and α

is the angle of attack.

14. The system of claim 11 wherein the processor is further configured to:

determine an ambient pressure from the standard atmospheric data, and wherein determining the first Mach number comprises determining by the equation M²=(n*mg−

T sin α

)/(0.7SPaCza), where M² is the first Mach number squared, n is the load factor, mg is the weight, S is the wing surface area, Pa is the ambient air pressure, Cza is the coefficient of lift, T is the thrust, and α

is the angle of attack.

15. The system of claim 11 further comprising:

one of a global positioning system, an inertial reference system, or a radio altimeter configured to determine a second altitude.

16. The system of claim 11 wherein the flight management system is further configured to:

determine the load factor and the weight.