Method and apparatus for reducing false taws warnings and navigating landing approaches

A terrain awareness and warning system for an aircraft comprising:

• a display apparatus which displays terrain within a forward region based on the aircraft's projected flight path and generates alerts and/or warnings for terrain in or proximate to the aircraft's current projected flight path;
• and
• an inhibition module which inhibits at least one of said alerts, warnings and terrain display under at least the following condition:
• the aircraft is within a predetermined geometric volume surrounding an airport, and
• the aircraft's projected flight path is such that the aircraft is or is expected to be within an approach volume that extends from a runway at the airport towards an outer boundary of the geometric volume and to stay within the approach volume to the runway.

A method of navigating an aircraft to land on a runway, comprising:

• determining if the aircraft is within a predetermined geometric volume surrounding an airport;
• if the aircraft is within the geometric volume, then determining the aircraft's projected flight path for a selected time;
• comparing the aircraft's projected flight path with an approach volume extending from a runway at the airport towards an outer boundary of the geometric volume;
• if the aircraft's current projected flight path is such that the aircraft is or is expected to be within the approach volume and stay within the approach volume to the runway, then indicating that the aircraft is on proper course for landing;
• and
• if the aircraft's current projected flight path is such that the aircraft is not and is not expected to be within the approach volume or to stay within the approach volume to the runway, indicating that the aircraft is not on a proper course for landing.

A computer method of calculating an approach volume for a runway for use with a terrain awareness and warning system or navigation system in an aircraft, comprising:

• (a) loading a predetermined geometric volume surrounding the runway into a computer memory;
• (b) selecting a location along said runway as a ground point intercept (GPI);
• (c) selecting a most preferred approach path glide slope angle;
• (d) selecting lateral boundaries for the approach volume;
• (e) postulating a tentative lower approach path plane that intersects the GPI and extends to an outer boundary of the geometric volume at an angle that is a predetermined amount more acute than said approach path glide slope angle;
• (f) determining whether the tentative lower approach path plane clears all terrain from the GPI to the outer boundary of the geometric volume by a predetermined safety margin, and if so, selecting the tentative lower approach path plane as an actual lower approach path plane, and if not, increasing the approach path glide slope angle and repeating steps (e) and (f) until the actual lower approach path plane is selected.

A terrain awareness and warning system for an aircraft comprising:

• means for displaying terrain within a predetermined look-ahead region based on the aircraft's projected flight path and generating alerts and warnings for terrain in or proximate to the aircraft's current projected flight path;
• and
• means for inhibiting at least one of said alerts, warnings and terrain display under at least the following conditions:
• the aircraft is within a predetermined geometric volume surrounding an airport, and
• the aircraft's projected flight path is such that the aircraft is or is expected to be within an approach volume that extends from a runway at the airport towards an outer boundary of the geometric volume and to stay within the approach volume to the runway.

A method of reducing at least one of nuisance alerts and warnings in a terrain awareness and warning system for an aircraft, comprising:

• (a) determining if the aircraft is within a predetermined geometric volume surrounding an airport;
• (b) if the aircraft is within the geometric volume, then determining a projected flight path for a selected time for the aircraft;
• (c) comparing the aircraft's current projected flight path with at least one approach volume extending from a runway at the airport towards an outer boundary of the geometric volume;
• (d) if the aircraft's current projected flight path is such that the aircraft is or is expected to intersect the approach volume, then determining whether the aircraft is capable of maneuvering within said approach volume so as to stay within the approach volume to the runway;
• (e) if the determination of step (d) is positive, then inhibiting at least one of selected alerts and warnings associated with terrain and repeating step (d);
• (f) if the determination of step (d) is negative, then reactivating any previously inhibited alerts and warnings of step (e).