Communications: electrical – Aircraft alarm or indicating systems – Flight alarm
Reexamination Certificate
2000-02-01
2004-03-16
Swarthout, Brent A. (Department: 2632)
Communications: electrical
Aircraft alarm or indicating systems
Flight alarm
C701S009000
Reexamination Certificate
active
06707394
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to ground proximity warning systems for use in aircraft. More particularly, the apparatus, methods, and computer program products of the present invention relate to generating a terrain clearance floor envelope about a selected runway for use by a ground proximity warning system to provide appropriate ground proximity warning alerts.
BACKGROUND OF THE INVENTION
An important advancement in aircraft flight safety has been the development of ground proximity warning systems. These warning systems analyze the flight parameters of the aircraft and the terrain surrounding the aircraft. Based on this analysis, these warning systems provide alerts to the flight crew concerning possible inadvertent collisions with terrain or other obstacles. Further, these ground proximity warning systems ensure that the aircraft maintains a minimum altitude with regard to terrain underlying the aircraft.
For example, one ground proximity warning system has been developed that generates terrain caution and warning envelopes that extend forward of the aircraft based on the position and flight parameters of the aircraft. Terrain and obstacles that pierce the terrain caution and warning envelopes are displayed to the flight crew as potential ground proximity problems by appropriate alarms or warnings. Further, and importantly, the ground proximity warning system also generates terrain clearance floor envelopes that provide minimum altitudes that the aircraft should maintain above terrain underlying the aircraft. If the altitude of the aircraft with respect to the underlying terrain, is less than the minimum altitude required by the terrain clearance floor envelope, the ground proximity warning system will provide appropriate alerts.
These ground proximity warning systems are quite useful in providing the flight crew with information concerning potential problems with the navigation of the aircraft. However, the usefulness of these systems must be balanced against problems associated with providing false alerts to the flight crew that may cause the flight crew to ignore alarms from the ground proximity warning system altogether. For example, during the landing operation of the aircraft, the aircraft will follow a flight path that will eventually intersect the earth at the intended runway on which the aircraft is scheduled to land. In the landing operation, ground proximity warning systems, if not adequately controlled, may generate constant alarms. The constant generation of alarms during landing may be a nuisance due to the added stress and confusion the alarms may impose on the flight crew. Additionally, the nuisance alarms may overshadow other critical alarms in the cockpit.
For this reason, at least one ground proximity warning system has been designed to alter the terrain clearance floor envelopes as the aircraft approaches a selected runway. The terrain clearance floor envelope is altered to reflect a landing pattern of the aircraft. As the aircraft descends toward the runway during landing, the ground proximity warning system provides ground proximity alerts based on the modified terrain clearance floor envelope. As such, the ground proximity warning system provides ground proximity warning protection, while at the same time reducing the number of nuisance alarms.
An example of such a ground proximity warning system is described in the following patents: 1) U.S. Pat. No. 5,839,080 to Muller et al. entitled “Terrain Awareness System,” 2) U.S. Pat. No. 4,914,436 to Bateman et al. entitled “Ground Proximity Approach Warning System Without Landing Flap, and 3) U.S. Pat. No. 3,922,637 to Bateman, entitled “Aircraft Landing Approach Ground Proximity Warning System.” These patents are incorporated herein by reference.
With reference to
FIG. 1
, the ground proximity warning system described in the above references generates a terrain clearance floor envelope
10
about a selected runway
12
. The envelope is typically centered about the selected runway and is typically conical or bowl shaped. The terrain clearance floor envelope has an inner
14
and an outer
22
boundary. As the envelope converges from the outer to the inner boundary, the terrain clearance floor envelope typically decreases in altitude. Further, the terrain clearance floor envelope may include differing slope portions that provide different slopes at different distances from the selected runway. The different sloped portions and their respective distances from the selected runway are chosen to provide desired ground proximity protection, while at the same time reducing the number of nuisance alerts. Beyond the outer boundary, the ground proximity warning system generates a terrain clearance floor envelope
24
that has a constant minimum altitude that the aircraft should maintain above underlying terrain.
An important aspect of the terrain clearance floor envelope is the inner boundary that is proximate to the selected runway. The inner boundary
14
defines a boundary at which the ground proximity warning system ceases to generate ground proximity warning alerts. Cessation in the generation of ground proximity alerts at the inner boundary is important to eliminate the number of nuisance alarms provided to the flight crew during the final approach of the aircraft to the selected runway. The distance between the selected runway and the inner boundary is used to define the distances of the differing slope portions from the selected runway and the location of the outer boundary from the selected runway.
Ideally, the inner boundary would be located as close as possible to the perimeter of the selected runway to thereby provide ground proximity warning protection until the aircraft lands on the selected runway. However, the inner boundary should not overlap with the perimeter of the selected runway, as it may cause the ground proximity warning system to provide nuisance alarms during the final approach of the aircraft. In reality, however, precise determination of the location of the inner boundary may be difficult.
Specifically, the determination of the location of the inner boundary is typically based on the coordinate position of the selected runway and the coordinate position and altitude of the aircraft. However, there are typically data uncertainties associated with the indications of the present position of the aircraft and the coordinate position of the selected runway. These uncertainties make it difficult to locate the inner boundary of the terrain clearance floor envelope in close proximity to the outer perimeter of the selected runway while not overlapping the perimeter of the selected runway.
For this reason, the conventional ground proximity warning system described above typically determines an aircraft position uncertainty factor representing an uncertainty in the coordinate position of the aircraft. The conventional ground proximity warning system typically adds to the aircraft position uncertainty of the aircraft a predetermined buffer distance that is the same for all runways. This added buffer distance is typically 1 nm and is selected to provide a more conservative estimate of the location of the inner boundary, such that the inner boundary does not overlap the perimeter of the selected runway. Additionally, the conventional ground proximity warning system typically locates the inner boundary at a preselected altitude representing a minimum altitude that the aircraft should maintain above underlying terrain at the inner boundary. In light of this selected buffer distance, the distance
16
between the inner boundary and the selected runway defines a region in which the ground proximity warning system does not provide ground proximity alarms. It would be desirable to provide a ground proximity warning system that more precisely defines the location of the inner boundary to thereby not unnecessarily enlarge this region between the inner boundary and the selected runway.
The approach used by the conventional ground proximity warning system to accommodate for err
Gremmert Scott
Ishihara Yasuo
Johnson Steven C.
Black Lowe & Graham PLLC
Honeywell Inc.
Swarthout Brent A.
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