Premature descent into terrain visual awareness enhancement to EGPWS

• US 6,292,721 B1
• Filed: 06/23/1998
• Issued: 09/18/2001
• Est. Priority Date: 07/31/1995
• Status: Expired due to Term

• Current Assignee: Alliedsignal Inc. (Honeywell International Inc.)
• Original Assignee: Alliedsignal Inc. (Honeywell International Inc.)
• Inventors: Muller, Hans Rudolf, Conner, Kevin J
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): PIPALA, EDWARD J
• Application Number:
  US09/103,349
• Time in Patent Office: 1,183 Days
• Field of Search: 701/3, 701/4, 701/8, 701/9, 701/120, 701/207, 701/208, 701/209, 701/213, 701/300-302, 340/945, 340/963, 340/964, 340/970, 340/971, 340/977, 731/78.R, 731/78.T, 244/180, 244/181
• US Class Current: 701/9
• 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: G01C 5/005 altimeters for aircraft G01C5/02, G01C5/06 take precedence
• CPC Class Codes: G05D 1/0676 specially adapted for landing

Abstract

In order to provide the pilots with a display or a map of the terrain below the aircraft, a display is generated on a cockpit display, such as a weather radar, of the contours of the terrain below the aircraft. The terrain contour display is generated from aircraft position information, a terrain data base, and a terrain awareness envelope defined by awareness boundaries. Terrain contours are depicted with the highest terrain within the envelope colored red, high intermediate terrain contours in yellow with varying dot densities, low intermediate terrain contours in green with varying dot densities, and the lowest terrain in black. The green contours can be overwritten with a low density yellow based on a pre-caution envelope which extends certain of the awareness boundaries to provide notice to a pilot of upcoming cautions.

Claims

1. An aircraft terrain awareness system comprising:

a processor configured to evaluate terrain over which an aircraft can fly and generate cautions for terrain features which will come within a first predetermined range of the aircraft, based on a current position and ground-track of the aircraft; and

wherein the processor is further configured to generate pre-cautions a predetermined precaution distance beyond the first predetermined range, the pre-cautions for a given terrain feature being generated at an earlier point in time than cautions for the given terrain feature.

2. The aircraft terrain awareness system of claim 1 wherein the processor is further configured to generate warnings for terrain features which will come within a second predetermined range of the aircraft based on a current position and course of the aircraft, said second predetermined range being less than the first predetermined range.

3. The aircraft terrain awareness system of claim 2 wherein the cautions and warnings are displayed on a visual display representative of a plan view of the terrain over which the aircraft can fly, wherein:

the cautions are displayed in a first color having a first color density;

the warnings are displayed in a second color; and

the pre-cautions are displayed in the first color having a second color density, the second color density being less than the first color density.

4. The aircraft terrain awareness system of claim 1 wherein at least a portion of the predetermined precaution distance is generated based on a descent rate of the aircraft.

5. The aircraft terrain awareness system of claim 4 wherein the first predetermined range comprises a forward-looking component and a downward-looking component, and wherein the predetermined precaution distance for the downward looking component is generated based on a descent rate of the aircraft, and the predetermined precaution distance for the forward-looking component is generated based on a preselected percentage of the forward-looking component.

6. The aircraft terrain awareness system of claim 5 wherein the first predetermined range further comprises a sideways-looking component a preselected lateral distance either side of the aircraft, and wherein the predetermined precaution distance for the sideways-looking component is generated based on a pre-selected offset and angle.

7. An aircraft terrain awareness system comprising:

a navigational system configured to determine latitude, longitude, altitude, groundtrack, and ground speed of an aircraft employing the system and to generate signals in response thereto;

a terrain database comprising altitude data for terrain over which the aircraft can fly;

a processor configured to identify from the terrain database altitude data within a range of the aircraft;

a look-ahead warning generator configured to receive the altitude identified by the processor and generate an altitude data subset of terrain altitudes within a first determined zone around the aircraft, the warning generator further configured to receive the signals generated by the navigational system, wherein the warning generator processes the altitude data subset, as well as the signals generated by the navigational system, to identify terrain which can intrude the first predetermined zone, and generate a warning signal in response to thereto;

a warning device configured to receive the warning signal and generate a primary warning in response thereto;

wherein the warning generator is further configured to generate an incremental data subset of terrain altitudes a determined incremental range beyond the first determined zone, and to process the incremental data subset to identify terrain which will intrude the incremental range, and generate a caution signal in response to thereto; and

wherein the warning device is configured to receive the caution signal and generate a secondary warning in response thereto.

8. The aircraft terrain awareness system of claim 7 wherein the first determined zone around the aircraft comprises a look-ahead distance in front of the aircraft and a look-down distance below the aircraft, and wherein the determined incremental range comprises an incremental look-ahead distance beyond the look-ahead distance, and an offset distance beyond the look-down distance.

9. The aircraft terrain awareness system of claim 8 wherein the offset distance is a function of the descent rate of the aircraft and a preselected lead time.

10. The aircraft terrain awareness system of claim 8 wherein the incremental look-ahead distance is a preselected percent of the look-ahead distance.

11. The aircraft terrain awareness system of claim 8 wherein the look-down distance comprises a terrain floor distance, the terrain floor distance being proportional to a distance from the aircraft to a preselected runway, and wherein the terrain floor distance is limited to a preselected terrain floor maximum.

12. The aircraft terrain awareness system of claim 11 wherein the look-down distance further comprises a cut-off boundary configured to limit the terrain floor distance within a cut-off zone proximate the aircraft, the cut-off boundary beginning at a predetermined cut-off offset distance immediately below the aircraft and extending at a cut-off angle therefrom to the terrain floor distance, the cut- off angle being a function of an instantaneous climb angle of the aircraft.

13. The aircraft terrain awareness system of claim 12 wherein the look-down distance further comprises a beta sink rate enhancement boundary configured to extend the terrain floor distance beyond the cut-off boundary, the beta sink rate enhancement boundary beginning the terrain floor distance immediately below the aircraft and extending therefrom at a sink-rate enhancement angle to a preselected fraction of the look ahead distance, and thence horizontally forward to the look-ahead distance.

14. The aircraft terrain awareness system of claim 13 wherein:

the sink rate enhancement angle is a function of the climb rate of the aircraft, wherein a negative climb rate indicates descent of the aircraft; and

the preselected fraction of the look-ahead distance is approximately one-half.

15. The aircraft terrain awareness system of claim 14 wherein the offset extends the look-down distance by a distance

16. The aircraft terrain awareness system of claim 8 wherein the look-ahead distance is a function of a speed of the aircraft times a look-ahead time, the look-ahead time being determined as a function of aircraft maneuvering time required to avoid terrain contact with the aircraft.

17. The aircraft terrain awareness system of claim 16 wherein the look ahead time comprises a time to turn the aircraft plus a time to prevent inadvertent terrain contact as a result of the turn plus a reaction time.

18. The aircraft terrain awareness system of claim 8 wherein the incremental look-ahead distance is a preselected percent of the look-ahead distance.

19. The aircraft terrain awareness system of claim 7 wherein the warning generator is further configured to generate a caution signal when the aircraft is descending.

20. The aircraft terrain awareness system of claim 8 wherein the first determined zone around the aircraft further comprises a look-up terrain advisory envelope, the look-up terrain advisory envelope extending a second predetermined distance beyond the look-ahead distance, the upper limit of the look-up terrain advisory limit being defined by a line extending at an angle from a third predetermined distance immediately below the aircraft upward at a look-up angle, the look-up angle being a function of the absolute value of a flight angle of the aircraft.

21. The aircraft terrain awareness system of claim 20 wherein the determined incremental range further comprises a look-up offset, the look-up offset being a function of a rate of descent of the aircraft.

22. A method for generating terrain feature caution notifications for an aircraft which can fly over a terrain, comprising:

defining a terrain advisory envelope in a region proximate the aircraft, such that when terrain features intrude within the terrain advisory envelope a caution signal detectable by a pilot of the aircraft is generated;

defining a pre-caution envelope extending beyond at least a portion of the terrain advisory envelope, such that when terrain features intrude within the terrain advisory envelope a pre-caution signal detectable by the pilot is generated; and

wherein the caution signal is configured to be more easily detectable by the pilot than the pre-caution signal.

23. The method of claim 22 further comprising:

providing altitude data for terrain over which the aircraft can fly;

comparing the altitude data immediately below the terrain advisory envelope and the pre-caution envelope against an altitude of the aircraft;

identifying terrain features which intrude the terrain advisory envelope and the pre-caution envelope;

generating the caution signals when terrain features intrude the terrain advisory envelope; and

generating the pre-caution signals when terrain features intrude the pre-caution envelope.