Device, method and computer program product for altimetry system

• US 6,584,384 B2
• Filed: 02/02/2001
• Issued: 06/24/2003
• Est. Priority Date: 02/03/2000
• Status: Expired due to Term

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Burlingame, Glen, Johnson, Steven C., Gremmert, Scott
• Primary Examiner(s): Black, Thomas G.
• Assistant Examiner(s): To, Tuan C
• Application Number:
  US09/783,575
• Publication Number:
  US 20010047230A1
• Time in Patent Office: 872 Days
• Field of Search: 701/4, 701/300, 701/301, 701/200, 701/307, 701/317, 701/302, 340/945, 340/961, 340/963, 340/120, 340/63, 340/29, 340/970, 340/976, 340/972, 340/977, 340/462, 244/180
• US Class Current: 701/4
• CPC Class Codes: G01C 25/00 Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass testing, calibrating or compensating compasses G01C17/38
• CPC Class Codes: G01C 5/005 altimeters for aircraft G01C5/02, G01C5/06 take precedence

Abstract

An apparatus, system, method and computer program product to verify proper operation of an aircraft altimetry system. Aural and visual alerts may optionally be provided when a fault in the altimetry is detected.

Claims

1. An apparatus for detecting faults in aircraft altimetry comprising:

(a) a first logic having;

(i) an input coupled to receive a Gray-coded altitude; and

(ii) error logic to detect an error in said Gray-coded altitude;

(iii) an output for asserting a first error signal when said error is detected;

(b) a second logic having;

(i) an input coupled to receive a pressure altitude data and a secondary source of altitude data;

(ii) altitude rate logic to compare a first rate of change of said pressure altitude data and a second rate of change of said secondary source of altitude data; and

(iii) an output for asserting a second error signal when said first and second rate of change differ by more than a predetermined amount;

(c) a third logic having;

(i) an input coupled to receive said pressure altitude data and a tertiary source of altitude data;

(ii) a comparison logic to obtain a difference between said pressure altitude and said tertiary source of altitude data;

(iii) a error budget logic that obtains an error budget based on known characteristics of said pressure altitude data and said tertiary source of altitude data;

(iv) an output for asserting a third error signal when said difference exceeds said error budget; and

(d) an alerting logic having;

(i) an input coupled to receive said first error signal, said second error signal and said third error signal; and

(ii) an output for asserting an alert signal when at least one of said first error signal, said second error signal and said third error signal is asserted.

2. The apparatus of claim 1 wherein said tertiary source of altitude data and said secondary source of altitude data comprise data received from the same sensor.

3. The apparatus of claim 1 wherein said alert signal includes a signal to control an aural alert.

4. The apparatus of claim 1 wherein said alert signal includes a signal to control a visual alert.

5. The apparatus of claim 1 wherein said alerting device further comprises a second output for asserting an altimetry valid signal when each of said first error signal, said second error signal and said third error signal are deasserted.

6. The apparatus of claim 1 wherein said secondary source of altitude data comprises altitude data received from a satellite based navigation system.

7. The apparatus of claim 6 wherein said satellite based navigation system comprises a global positioning system.

8. The apparatus of claim 1 wherein said error budget accounts for errors due to nonstandard atmospheric conditions.

9. The apparatus of claim 1 wherein said error budget accounts for errors due to differences between pressure altitude data and geometric altitude data based on a predetermined model atmosphere.

10. The apparatus of claim 1 wherein said error budget accounts for errors due to operational inaccuracies in said tertiary source of altitude data.

11. The apparatus of claim 1 further including a means to enable said apparatus.

12. The apparatus of claim 1 wherein said alert signal is configurable.

13. The apparatus of claim 1 wherein said apparatus comprises an Enhanced Ground Proximity Warning System computer.

14. The apparatus of claim 1 wherein said tertiary source of altitude data comprises an altitude calibrated from a terrain data base.

72. The apparatus of claim 1, wherein the gray altitude code is Gillham-coded altitude.

15. An apparatus for detecting errors in Gray-coded altitude comprising:

a first logic for comparing a current Gray-coded altitude to a previously sampled Gray-coded altitude and for asserting a first signal when said current code and said previously sampled code are not identical and for obtaining a difference between said current code and said previously sampled code;

a second logic for comparing said difference to a first predefined error condition and asserting a first error signal when said difference matches said predefined error condition and when said first signal is asserted;

a third logic for comparing bits C1, C2, C4 of said current code to a predetermined set of invalid bit sequences and for asserting a second error signal when said current code matches at least one of said invalid bit sequences; and

an output for asserting a Gray-coded altitude error signal when at least one of said first error signal or said second error signal is asserted.

16. The apparatus of claim 15 wherein said output further includes a device for verifying a given state of said Gillham altitude error signal exists for a specified period before outputting said Gillham altitude error signal.

17. The apparatus of claim 15 wherein said apparatus is enabled when said aircraft is airborne.

18. The apparatus of claim 15 wherein said apparatus comprises a computer processor with executable code.

19. The apparatus of claim 15 wherein said apparatus comprises an aircraft transponder.

20. The apparatus of claim 15 wherein said apparatus comprises an Enhanced Ground Proximity Warning System computer.

21. The apparatus of claim 15 wherein said apparatus comprises a Traffic Collision and Avoidance System computer.

69. The apparatus of claim 15 wherein said apparatus comprises a flight management system computer.

73. The apparatus of claim 15, wherein the gray altitude code is Gillham-coded altitude.

22. An apparatus for detecting errors in aircraft altimetry comprising:

an input for receiving a first and second source of altitude data;

a first logic to obtain a difference in a rate of change of each of said first and second sources of altitude data; and

a second logic for comparing said difference to a predetermined value and for asserting an altimetry error signal when said difference exceeds said predetermined value.

23. The apparatus of claim 22 wherein said second logic further comprises a track hold logic for outputting said altimetry error signal only when said altimetry error signal has been asserted for a predefined period.

24. The apparatus of claim 22 wherein said apparatus comprises an Enhanced Ground Proximity Warning System computer.

25. The apparatus of claim 22 wherein said apparatus comprises a Traffic Collision and Avoidance System computer.

26. The apparatus of claim 22 wherein said apparatus comprises a transponder.

70. The apparatus of claim 22 wherein said apparatus comprises a flight management system computer.

74. The apparatus of claim 22, wherein the altitude data from at least one of the first and second sources is Gillham-coded.

27. An apparatus for detecting errors in aircraft pressure altitude measurements comprising:

an input for receiving a pressure altitude data and a geometric altitude data;

a first logic for obtaining a difference between said pressure altitude data and said geometric altitude data;

a second logic for defining a first probable error between said geometric altitude data and said pressure altitude data based on a standard atmosphere;

a third logic for defining a second probable error due to deviations from nonstandard atmospheric conditions; and

a fourth logic for comparing a sum of said first and second probable errors to said difference and asserting a pressure altitude error signal when said difference exceeds said sum.

28. The apparatus of claim 27 wherein said sum additionally includes a third error term defining a third probable error in measurement of said geometric altitude.

29. The apparatus of claim 27 wherein said geometric altitude data additionally includes geometric altitude data obtained from a terrain data base.

30. The apparatus of claim 27 wherein said fourth logic comprises a track hold logic for outputting said altimetry error signal only when said pressure altitude error signal has been asserted for a predefined period.

31. The apparatus of claim 27 wherein said apparatus comprises an Enhanced Ground Proximity Warning System computer.

32. The apparatus of claim 27 wherein said apparatus comprises a Traffic Collision and Avoidance System computer.

33. The apparatus of claim 27 wherein said apparatus comprises a transponder.

34. The apparatus of claim 27 further comprising a switch for using a first source of geometric altitude data when airborne and a second source of geometric altitude data when on the ground.

35. The apparatus of claim 34 wherein said first source of geometric altitude data comprises geometric altitude data from a satellite based navigation system.

36. The apparatus of claim 35 wherein said satellite based navigation system comprises a global positioning system.

37. The apparatus of claim 34 wherein said second source of geometric altitude data comprises data from a terrain data base.

71. The apparatus of claim 27 wherein said apparatus comprises a flight management system computer.

38. A method for detecting errors in Gray-coded altitude comprising the steps of:

comparing a current Gray-coded altitude to a previously sampled Gray-coded altitude and asserting a first signal when said current code and said previously sampled code are not identical;

obtaining a difference between said current code and said previously sampled code;

comparing said difference to a first predefined error condition and asserting a first error signal when said difference matches said predefined error condition and when said first signal is asserted;

comparing specified bit positions of said current code to a predetermined set of invalid bit sequences for said bit positions;

asserting a second error signal when said current code matches at least one of said invalid bit sequences; and

asserting an altitude error signal when at least one of said first error signal or said second error signal is asserted.

39. The method of claim 38 further comprising the step of providing an alert to a cockpit crew when said altitude error signal is asserted.

40. The method of claim 39 wherein said step of providing an alert comprises the step of providing a visual alert.

41. The method of claim 39 wherein said step of providing an alert comprises the step of providing an aural alert.

42. The method of claim 38 further comprising the step of providing an alert to an aircraft system utilizing the Gray-coded altitude when said Gray-coded altitude error signal is asserted.

43. The method of claim 42 wherein said step of providing an alert comprises the step of deasserting an altimetry valid signal.

75. The method of claim 42, wherein the gray altitude code is Gillham-coded altitude.

44. A method for detecting errors in altimetry comprising the steps of:

obtaining a difference in a rate of change of each of a first and a second sources of altitude data; and

comparing said difference to a predetermined value; and

asserting an altimetry error signal when said difference exceeds said predetermined value.

45. The method of claim 44 further comprising the step of providing an alert to a cockpit crew when said altimetry error signal is asserted.

46. The method of claim 45 wherein said step of providing an alert comprises the step of providing a visual alert.

47. The method of claim 45 wherein said step of providing an alert comprises the step of providing an aural alert.

48. The method of claim 44 further comprising the step of providing an alert to an aircraft system utilizing the altimetry when said altimetry error signal is asserted.

49. The method of claim 48 wherein said step of providing an alert comprises the step of deasserting an altimetry valid signal.

50. A method for detecting errors in altimetry comprising the steps of:

obtaining a difference between a pressure altitude data and a geometric altitude data;

defining a first probable error between said geometric altitude data and said pressure altitude data based on a standard atmosphere;

defining a second probable error due to deviations from nonstandard atmospheric conditions; and

comparing a sum of said first and said second probable errors to said difference and asserting a pressure altitude error signal when said difference exceeds said sum.

51. The method of claim 50 wherein said step of comparing a sum further comprises the step of adding to said sun, a third probable error resulting from measurement of said geometric altitude.

52. The method of claim 50 further comprising the step of obtaining said geometric altitude data from a terrain data base.

53. The method of claim 50 further comprising the step of providing an alert to a cockpit crew when said pressure altitude error signal is asserted.

54. The method of claim 53 wherein said step of providing an alert comprises the step of providing a visual alert.

55. The method of claim 53 wherein said step of providing an alert comprises the step of providing an aural alert.

56. The method of claim 50 further comprising the step of providing an alert to an aircraft system utilizing the altimetry when said altimetry error signal is asserted.

57. The method of claim 56 wherein said step of providing an alert comprises the step of deasserting an altimetry valid signal.

58. A computer program for detecting Gray-coded altitude errors comprising:

a computer readable storage medium having computer readable program code means embodied in said medium, said computer readable program code means having;

first computer instruction means for comparing a current Gray-coded altitude to a previously sampled Gray-coded altitude and asserting a signal when said current code and said previously sampled code are not identical;

second computer instruction means for comparing said current code to said previously sampled code to obtain a difference;

third computer instruction means for comparing said difference to a predefined error condition and asserting a first error signal when said difference matches said error condition and said first signal is asserted;

fourth computer instruction means for comparing specified bit positions of said current code to a predetermined set of invalid bit sequences for said bit positions;

fifth computer instruction means for asserting a second error signal when said specified bit positions match at least one of said predetermined set of invalid bit sequences; and

sixth computer instruction means for asserting an altitude error signal when at least one of said first error signal or said second error signal is asserted.

59. The computer program product of claim 58 further comprising a seventh computer instruction means for providing an alert to a cockpit crew when said altitude error signal is asserted.

60. The computer program product of claim 58 further comprising a seventh computer instruction means for providing an alert to an aircraft system utilizing the Gray-coded altitude when said altitude error signal is asserted.

76. The product of claim 60, wherein the gray altitude code is Gillham-coded altitude.

61. A computer program product for detecting errors in altimetry comprising:

a computer readable storage medium having computer readable program code means embodied in said medium, said computer readable program code means having;

first computer instruction means for accessing a first source of altitude data and a second source of altitude data;

second computer instruction means for obtaining a difference in a rate of change of said first source of altitude data and a rate of change in said second source of altitude data;

third computer instruction means for comparing said difference to a predetermined value; and

fourth computer instruction means for asserting an altimetry error signal when said difference exceeds said predetermined value.

62. The computer program product of claim 61 further comprising a fifth computer instruction means for providing an alert to a cockpit crew when said altimetry error signal is asserted.

63. The computer program product of claim 61 further comprising a fifth computer instruction means for providing an alert to an aircraft system utilizing the altimetry when said altimetry error signal is asserted.

64. A computer program product for detecting errors in altimetry comprising:

a computer readable storage medium having computer readable program code means embodied in said medium said computer readable program code means having;

first computer instruction means for accessing a pressure altitude data and a geometric altitude data;

second computer instruction means for obtaining a difference between said pressure altitude data and said geometric altitude data;

third computer instruction means for defining a first probable error between said geometric altitude data and said pressure altitude data;

fourth computer instruction means for defining a second probable error due to deviations from a standard atmosphere; and

fifth computer instruction means for comparing a sum of said first and second probable errors to said difference and asserting a pressure altitude error signal when said difference exceeds said sum.

65. The computer program product of claim 64 further comprising:

sixth computer instruction means for defining a third probable error resulting from measurement of geometric altitude; and

wherein said fifth computer instruction means includes said third probable error in said sum.

66. The computer program product of claim 64 further comprising a sixth computer instruction means for providing an alert to a cockpit crew when said pressure altitude error signal is asserted.

67. The computer program product of claim 64 further comprising a sixth computer instruction means for providing an alert to an aircraft system utilizing the altimetry when said pressure altitude error signal is asserted.

68. The computer program product of claim 64 wherein said first computer instruction means accesses said geometric altitude data from a terrain data base.