(19) TZZ ¥¥_ _T (11) EP 2 833 152 B1 (12) EUROPEAN PATENT SPECIFICATION (45) Date of publication and mention (51) Int Cl.: of the grant of the patent: G01P 5/16 (2006.01) G01P 13/02 (2006.01) 19.07.2017 Bulletin 2017/29 G01P 21/02 (2006.01) (21) Application number: 14178085.8 (22) Date of filing: 22.07.2014 (54) System and method for computing mach number and true airspeed System und Verfahren zur Berechnung der Mach-Zahl und wahren Luftgeschwindigkeit Système et procédé de calcul de nombre de mach et de la vitesse réelle de l’air (84) Designated Contracting States: • Hillier, John AL AT BE BG CH CY CZ DE DK EE ES FI FR GB Morristown, NJ 07962-2245 (US) GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR (74) Representative: Houghton, Mark Phillip Patent Outsourcing Limited (30) Priority: 02.08.2013 US 201313958307 1 King Street Bakewell, Derbyshire DE45 1DZ (GB) (43) Date of publication of application: 04.02.2015 Bulletin 2015/06 (56) References cited: EP-A2- 2 348 285 EP-A2- 2 434 296 (73) Proprietor: Honeywell International Inc. US-A1- 2010 100 260 Morris Plains, NJ 07950 (US) • DENKER J S: "See how it flies, LIFT, THRUST, (72) Inventors: WEIGHT, AND DRAG", INTERNET CITATION, 3 • Nathan, Visvanathan Thanigai June 2004 (2004-06-03), XP002330050, Retrieved Morristown, NJ 07962-2245 (US) from the Internet: • Anandappan, Thanga URL:http://www.av8n.com/how/htm/4forces.ht Morristown, NJ 07962-2245 (US) ml [retrieved on 2005-05-31] Note: Within nine months of the publication of the mention of the grant of the European patent in the European Patent Bulletin, any person may give notice to the European Patent Office of opposition to that patent, in accordance with the Implementing Regulations. Notice of opposition shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). EP 2 833 152 B1 Printed by Jouve, 75001 PARIS (FR) EP 2 833 152 B1 Description TECHNICAL FIELD 5 [0001] The exemplary embodiments described herein generally relates to computing MACH number and true airspeed and more particularly to computing MACH number and true airspeed when a pitot tube is unavailable or malfunctioning. BACKGROUND 10 [0002] Measurement, computation, and display of true airspeed (TAS), MACH number (MN), and/or calibrated airspeed (CAS), as well as altitude, enables a pilot to maintain a recommended safe airspeed. Typically, these airspeeds (TAS, MN, CAS) and altitude are provided by an air data computer (ADC) that receives pertinent information from pitot static sensors. The ADC and pitot sensors typically include redundancies for high reliability; however, failures still occur resulting in improper aircraft operation. 15 [0003] Despite these multiple redundancies, maintenance safety, damage avoidance either on ground or in flight, and numerous pre-flight checks, a chance of malfunctioning of the pitot static sensor remains. In addition, the typically highly reliable ADC also may become undependable, providing incorrect information. It is therefore essential to have an alternate method of MN and TAS computation adapted for general aviation, business, regional and helicopters, and air transport aircraft either with or without a flight management system. 20 [0004] Accordingly, it is desirable to provide a system and method for calculating Mach number and true airspeed for comparison with, or in lieu of, a pitot static sensor. Furthermore, other desirable features and characteristics of the exemplary embodiments will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background. [0005] EP2348285A2 discloses an avionics system comprising a primary airspeed data source and a flight manage- 25 ment computer. The primary airspeed data source is configured to calculate a primary airspeed. The flight management computer is configured to use airspeed as an aid to control an aircraft, wherein the flight management computer is further configured to determine an alternative airspeed for use by the flight management computer as an aid to control an aircraft when the primary airspeed is unavailable. [0006] EP2434296A2 discloses an apparatus and method for identifying an airspeed for an aircraft. The apparatus 30 consists of a plurality of pitot-static probes generating firs t data, a plurality of angle of attack sensor systems generating second data and a plurality of light detection and ranging sensors generating third data. A signal consolidation system is configured to detect errors in the first data generated by the plurality of pitot-static probes, the second data generated by the plurality of angle of attack sensor systems, and the third data generated by the plurality of light detection and ranging sensors. 35 BRIEF SUMMARY [0007] The present invention provides a method for validating at least one of a first true airspeed or a first Mach number of an aircraft in flight, according to claim 1 of the appended claims. 40 [0008] The invention further provides a system for validating at least one of a first true airspeed or a first Mach number of an aircraft in flight, according to claim 6 of the appended claims. [0009] A system and method are provided for computing MACH number and true airspeed when a pitot tube is unavailable or malfunctioning. [0010] In an exemplary embodiment, a method for determining at least one of a first true airspeed or a first Mach 45 number of an aircraft in flight comprises 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 50 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. 55 [0011] In another exemplary embodiment, a method of determining at least one of a true airspeed or a Mach number of an aircraft in flight comprises 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; 2 EP 2 833 152 B1 sensing a temperature of the air adjacent the aircraft; and determining, from the group consisting of the standard atmos- pheric 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. 5 [0012] In yet another exemplary embodiment, a system for determining at least one of a first true airspeed or a first Mach number of an aircraft in flight comprises 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, 10 DETAILED DESCRIPTION [0013] The following detailed description is merely illustrative in nature and is not intended to limit the embodiments of thesubject matter or theapplication and uses of suchembodiments. Any implementationdescribed hereinas exemplary is not necessarily to be construed as preferred or advantageous over other implementations. Furthermore, there is no 15 intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary, or the following detailed description. [0014] Techniques and technologies may be described herein in terms of functional and/or logical block components, and with reference to symbolic representations of operations, processing tasks, and functions that may be performed by various computing components or devices. Such operations, tasks, and functions are sometimes referred to as being 20 computer-executed, computerized, software-implemented, or computer-implemented. In practice, one or more processor devices can carry out the described operations, tasks, and functions by manipulating electrical signals representing data bits at memory locations in the system memory, as well as other processing of signals. The memory locations where data bits are maintained are physical locations that have particular electrical, magnetic, optical, or organic properties corresponding to the data bits. It should be appreciated that the various block components shown in the figures may be 25 realized by any number of hardware, software, and/or firmware components configured to perform the specified functions. For example, an embodiment of a system or a component may employ various integrated circuit components, e.g., memory elements, digital signal processing elements, logic elements, look-up tables, or the like, which may carry out a variety of functions under the control of one or more microprocessors or other control devices.