Method, apparatus and computer program product for helicopter tail strike warning

• US 6,737,987 B2
• Filed: 05/25/2001
• Issued: 05/18/2004
• Est. Priority Date: 09/14/2000
• Status: Expired due to Term

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Conner, Kevin, Paterson, Noel
• Primary Examiner(s): TWEEL JR, JOHN ALEXANDER
• Application Number:
  US09/865,365
• Publication Number:
  US 20020030607A1
• Time in Patent Office: 1,089 Days
• Field of Search: 340/946, 340/963, 340/967, 340/970, 731/78.H, 244/17.11
• US Class Current: 340/946
• CPC Class Codes: B64C 27/82 characterised by the provision of an auxiliary rotor or fluid-jet device for counter-balancing lifting rotor torque or changing direction of rotorcraft
• CPC Class Codes: B64D 45/04 Landing aids; Safety measures to prevent collision with earth's surface
• CPC Class Codes: G01C 5/005 altimeters for aircraft G01C5/02, G01C5/06 take precedence

Abstract

A method, apparatus and computer program product for alerting the pilot of a helicopter of a possible tail strike hazard.

Claims

1. A method for alerting the pilot of a rotary wing aircraft of a tail strike hazard comprising the steps of:

defining a tail strike alert envelope as a function of a height above terrain and a pitch attitude;

receiving a signal indicative of an aircraft height above terrain;

receiving a signal indicative of a pitch attitude of the aircraft;

biasing the signal indicative of the pitch attitude; and

outputting an alert signal when said signal indicative of said aircraft height above terrain and said biased signal indicative of said pitch attitude of the aircraft define a condition contained within said envelope.

2. The method of claim 1 wherein said step of receiving a signal indicative of height above terrain comprises the step of receiving a radar altitude signal.

3. The method of claim 1 wherein said step of receiving a signal indicative of said pitch attitude of the aircraft further comprises the step of receiving a signal indicative of a pitch angle of the aircraft.

4. The method of claim 1 wherein biasing the signal indicative of the pitch attitude includes:

receiving a signal indicative of a pitch rate of the aircraft; and

using said signal indicative of said pitch rate to bias said signal indicative of said pitch attitude.

5. The method of claim 1 wherein biasing the signal ndicative of the pitch attitude includes:

receiving a signal indicative of an altitude rate of the aircraft; and

using said signal indicative of said altitude rate to bias said signal indicative of said pitch altitude.

6. The method of claim 1 wherein the aircraft is a tilt-rotor.

7. The method of claim 1 further comprising the step of modulating said envelope as a function of a descent rate of the aircraft.

8. The method of claim 1 further comprising the step of modulating said envelope as a function of a pitch rate of the aircraft.

24. The method of claim 1 wherein said step of outputting an alert further comprises the step of outputting an aural alert.

9. A computer program product for alerting a pilot of a rotary wing aircraft of a tail strike hazard comprising:

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

a first computer instruction means for defining a tail strike alert envelope as a function of a height above terrain and a pitch attitude;

a second computer instruction means for reading a signal indicative of an aircraft height above terrain;

a third computer instruction means for reading a signal indicative of a pitch attitude of the aircraft; and

a fourth computer instruction means for biasing the signal indicative of the pitch attitude;

a fifth computer instruction means for outputting an alert signal when said signal indicative of said aircraft height above terrain and said biased signal indicative of said pitch attitude of the aircraft define a condition contained within said envelope.

10. The computer program product of claim 9 wherein said signal indicative of height above terrain comprises a radar altitude signal.

11. The computer program of claim 9 wherein said third computer instruction means further comprises a computer instruction means for reading a signal indicative of a pitch angle of the aircraft.

12. The computer program product of claim 9 wherein the fourth computer instruction means includes:

a computer instruction means for reading a signal indicative of a pitch rate of the aircraft; and

a computer instruction means for using said signal indicative of said pitch rate to bias said signal indicative of said pitch attitude.

13. The computer program product of claim 9 wherein the fourth computer instruction means includes:

a computer instruction means for reading a signal indicative of an altitude rate of the aircraft;

a computer instruction means for using said signal indicative of said altitude rate to bias said signal indicative of said pitch attitude;

a computer instruction means for summing said second signal, said modulated third signal and said modulated fourth signal to obtain a pitch attitude estimate; and

an computer instruction means for outputting an alert signal when said signal indicative of said aircraft height above terrain and said pitch attitude estimate define a condition contained within said envelope.

14. The computer program product of claim 9 further comprising a fifth computer instruction means for modulating said envelope as a function of a descent rate of the aircraft.

15. The computer program product of claim 9 further comprising a fifth computer instruction means for modulating said envelope as a function of a pitch rate of the aircraft.

16. A method for alerting a pilot of a rotary wing aircraft of a tail strike hazard comprising the steps of:

defining a tail strike alert envelope as a function of a height above terrain and a pitch attitude;

receiving a first signal indicative of an aircraft height above terrain;

receiving a second signal indicative of a pitch angle of the aircraft;

receiving a third signal indicative of a pitch rate of the aircraft;

multiplying said third signal by a first gain to obtain a modulated third signal;

receiving a fourth signal indicative of an altitude rate of the aircraft;

multiplying said fourth signal by a second gain to obtain a modulated fourth signal;

summing said second signal, said modulated third signal and said modulated fourth signal to obtain a pitch attitude estimate; and

outputting an alert signal when said signal indicative of said aircraft height above terrain and said pitch attitude estimate define a condition contained within said envelope.

17. The method of claim 16 wherein the aircraft is a tilt rotor.

18. The method of claim 16 wherein said signal indicative of a height above terrain comprises a radar altitude signal.

19. The method of claim 16 further comprising the step of limiting said third signal to a predetermined range.

20. The method of claim 19 wherein said predetermined range is approximately +/−

10 degrees per second.

21. The method of claim 16 further comprising the step of summing said modulated fourth signal with said modulated third signal and said second signal only when said fourth signal is indicative of an aircraft descent.

22. The method of claim 16 further comprising the step of inhibiting said step of outputting an alert when the aircraft is carrying a sling load.

23. The method of claim 16 wherein said step of outputting an alert further comprises the step of outputting an aural alert.

25. A computer program product for alerting a pilot of a rotary wing aircraft of a tail strike hazard comprising:

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

a first computer instruction means for reading a first signal indicative of an aircraft height above terrain;

a second computer instruction means for reading a second signal indicative of a pitch angle of the aircraft;

a third computer instruction means for reading a third signal indicative of a pitch rate of the aircraft;

a fourth computer instruction means for multiplying said third signal by a first gain to obtain a modulated third signal;

a fifth computer instruction means for reading a fourth signal indicative of an altitude rate of the aircraft;

a sixth computer instruction means for multiplying said fourth signal by a second gain to obtain a modulated fourth signal;

a seventh computer instruction means for summing said second signal, said modulated third signal and said modulated fourth signal to obtain a pitch attitude estimate; and

an eighth computer instruction means for outputting an alert signal when said signal indicative of said aircraft height above terrain and said pitch attitude estimate define a condition contained within said envelope.

26. The computer program product of claim 25 wherein said signal indicative of a height above terrain comprises a radar altitude signal.

27. The computer program product of claim 25 wherein said third computer instruction means further includes a ninth computer instruction means to limit said third signal to a predetermined range.

28. The computer program product of claim 27 wherein said predetermined range is approximately +/−

10 degrees per second.

29. The computer program product of claim 25 wherein said seventh computer instruction means sums said modulated fourth signal with said modulated third signal and said second signal only when said fourth signal is indicative of an aircraft descent.

30. The computer program product of claim 25 further comprising a ninth computer instruction means for inhibiting said eighth computer instruction means when the aircraft is carrying a sling load.

31. The computer program product of claim 25 wherein said eighth computer instruction means further comprises a ninth computer instruction means for outputting an aural alert.

32. An apparatus for alerting a pilot of a rotary wing aircraft of a tail strike hazard, the apparatus comprising:

an input coupled to receive a signal indicative of an aircraft height above terrain and a signal indicative of a pitch attitude of the aircraft;

an output; and

a signal processor, coupled to said input and to said output, for;

biasing the signal indicative of the pitch attitude;

defining a tail strike alert envelope as a function of a height above terrain and a pitch attitude; and

outputting an alert signal when said signal indicative of said aircraft height above terrain and said biased signal indicative of said pitch attitude of the aircraft define a condition contained within said envelope.

33. The apparatus of claim 32 wherein said signal indicative of height above terrain comprises a radar altitude signal.

34. The apparatus of claim 32 wherein said signal indicative of said pitch attitude of the aircraft comprises a signal indicative of a pitch angle of the aircraft.

35. The apparatus of claim 32 wherein said input is further coupled to receive a signal indicative of a pitch rate of the aircraft and wherein said signal processor further uses said signal indicative of said pitch rate to bias said signal indicative of said pitch attitude.

36. The apparatus of claim 32 wherein said input is further coupled to receive a signal indicative of an altitude rate of the aircraft and wherein said signal processor further uses said signal indicative of said altitude rate to bias said signal indicative of said pitch attitude.

37. The apparatus of claim 32 wherein the aircraft is a tilt-rotor.

38. The apparatus of claim 32 wherein said signal processor further modulates said envelope as a function of a descent rate of the aircraft.

39. The apparatus of claim 32 wherein said signal processor further modulates said envelope as a function of a pitch rate of the aircraft.

40. The apparatus of claim 32 wherein said signal processor further outputs said alert signal as an aural alert.

41. The apparatus of claim 32 wherein said signal processor comprises a general purpose processor.

42. An apparatus for alerting a pilot of a rotary wing aircraft of a tail strike hazard the apparatus comprising:

an input coupled to receive a first signal indicative of an aircraft height above terrain, a second signal indicative of a pitch angle of the aircraft, a third signal indicative of a pitch rate of the aircraft and a fourth signal indicative of an altitude rate of the aircraft;

an output; and

a signal processor coupled to said input and to said output for;

defining a tail strike alert envelope as a function of a height above terrain and a pitch attitude;

multiplying said third signal by a first gain to obtain a modulated third signal;

multiplying said fourth signal by a second gain to obtain a modulated fourth signal;

summing said second signal, said modulated third signal and said modulated fourth signal to obtain a pitch attitude estimate; and

outputting an alert signal when said signal indicative of said aircraft height above terrain and said pitch attitude estimate define a condition contained within said envelope.

43. The apparatus of claim 42 wherein the aircraft is a tilt rotor.

44. The apparatus of claim 42 wherein said signal indicative of a height above terrain comprises a radar altitude signal.

45. The apparatus of claim 42 wherein said signal processor further limits said third signal to a predetermined range.

46. The apparatus of claim 45 wherein said predetermined range is approximately +/−

10 degrees per second.

47. The apparatus of claim 42 wherein said signal processor sums said modulated fourth signal with said modulated third signal and said second signal only when said fourth signal is indicative of an aircraft descent.

48. The apparatus of claim 42 wherein said signal processor inhibits outputting an alert when the aircraft is carrying a sling load.

49. The apparatus of claim 42 wherein said alert signal comprises an aural alert.

50. The apparatus of claim 42 wherein said signal processor comprises a general purpose processor.

51. In a GPWS device, an improvement to alert a pilot of a rotary wing aircraft of a tail strike hazard, the improvement comprising:

an input coupled to receive a signal indiactive of an aircraft height above terrain and a signal indicative of a pitch attitude of the aircraft;

an output; and

a signal processor coupled to said input and to said output, for;

biasing the signal indicative of a pitch attitude;

defining a tail strike alert envelope as a function of a height above terrain and a pitch attitude; and

outputting an alert signal when said signal indicative of said pitch attitude above terrain and said biased signal indicative of said pitch attitude of the aircraft define a condition contained within said envelope.

52. The improvement of claim 51 wherein the GPWS device comprises an EGPWS device.

53. The improvement of claim 51 wherein said signal processor further modulates said envelope as a function of a descent rate of the aircraft.

54. The improvement of claim 51 wherein said signal processor further modulates said envelope as a function of a pitch rate of the aircraft.

55. The improvement of claim 51 wherein said signal processor comprises a general purpose processor contained within the GPWS device.

56. The improvement of claim 51 wherein said signal processor outputs said alert signal as an aural alert.

57. In a GPWS device, an improvement to alert a pilot of a rotary wing aircraft of a tail strike hazard, the improvement comprising:

an input coupled to receive a first signal indicative of an aircraft height above terrain, a second signal indicative of a pitch angle of the aircraft, a third signal indicative of a pitch rate of the aircraft and a fourth signal indicative of an altitude rate of the aircraft;

an output; and

a signal processor coupled to said input and to said output for;

defining a tail strike alert envelope as a function of a height above terrain and a pitch attitude;

multiplying said third signal by a first gain to obtain a modulated third signal;

multiplying said fourth signal by a second gain to obtain a modulated fourth signal;

summing said second signal, said modulated third signal and said modulated fourth signal to obtain a pitch attitude estimate; and

outputting an alert signal when said signal indicative of said aircraft height above terrain and said pitch attitude estimate define a condition contained within said envelope.

58. The improvement of claim 57 wherein the GPWS device comprises an EGPWS device.

59. The improvement of claim 57 wherein said signal processor comprises a general purpose processor contained within the GPWS device.

60. The improvement of claim 57 wherein said signal processor outputs said alert signal as an aural alert.

61. The improvement of claim 57 wherein said signal processor inhibits output of said alert signal when the aircraft is carrying a sling load.