Communications: electrical – Aircraft alarm or indicating systems – Flight alarm
Reexamination Certificate
2000-02-01
2002-09-03
Hofsass, Jeffery (Department: 2632)
Communications: electrical
Aircraft alarm or indicating systems
Flight alarm
C340S945000, C340S951000, C340S963000, C701S301000
Reexamination Certificate
active
06445310
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 runway field 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.
FIG. 1
illustrates a typical terrain clearance floor envelope
10
generated by at least one ground proximity warning system. The terrain clearance floor envelope is typically generated with reference to a selected runway
12
. For different distances from the selected runway, the terrain clearance floor envelope prescribes different minimum altitudes that the aircraft should maintain above terrain currently underlying the aircraft. Beyond some maximum distance
14
from the selected runway, the aircraft must maintain at least some minimum altitude
16
above underlying terrain.
For example, if an aircraft is approximately 5 nm from a selected runway, the terrain clearance floor may prescribe that the aircraft should maintain at least an altitude of 400 ft above terrain underlying the aircraft. As such, if the aircraft is flying over terrain that has an elevation of 5,000 ft, the aircraft should maintain an altitude of at least 5,400 ft. In this example, if the aircraft dips below 5,400 ft altitude, the ground proximity warning system will provide appropriate alerts.
Importantly, with reference to
FIG. 1
, for distances closer to the selected runway, the terrain clearance floor envelope requires smaller minimum clearance altitudes that the aircraft should maintain above current terrain. This portion of the terrain clearance floor envelope reflects a landing pattern of the aircraft. The altitudes at various distances from the selected runway are selected to provide ground proximity warning protection, while also reducing generation of nuisance alarms that may disrupt the flight crew during landing. For example, when the aircraft is 2 nm from the selected runway, the flight crew will not receive an alert unless the aircraft dips to an altitude that is less than 200 ft above the underlying terrain.
For most instances, the terrain clearance floor envelopes generated by the ground proximity warning system, such as the terrain clearance floor envelope illustrated in
FIG. 1
, are generally advantageous as they provide ground proximity warning protection, while at the same time reducing nuisance alarms. However, there may be specific instances where additional ground proximity warning protection may be desired.
Specifically, as described above, the terrain clearance floor envelope requires minimum altitudes that the aircraft should maintain above current terrain depending upon the distance between the aircraft and selected runway. While the terrain clearance floor envelope is typically more than adequate for ground proximity warning protection, problems may occur where terrain near the selected runway, (e.g., within 2 to 15nm of the selected runway), is at a significant lower elevation than the elevation of the selected runway or terrain or obstacles in close proximity to the selected runway. In this instance, the current terrain clearance floor envelopes generated by the ground proximity warning system may not provide desired warning time for reacting to these changes in elevation.
Specifically,
FIG. 2
illustrates a situation where providing added reaction time to the flight crew of the aircraft may be desired.
FIG. 2
illustrates a situation where the elevation of the selected runway
12
or terrain or obstacles proximate to the selected runway are at a significantly higher elevation, (e.g., elevation 800 ft), than terrain
18
less proximate to the selected runway, (e.g., elevation 300 ft). In this situation, it may be desired to provide an increased reaction time to the flight crew of the abrupt change in elevation that occurs near the selected runway.
In particular, with reference to
FIG. 2
, if an aircraft
8
is more than 15 nm from the selected runway, (see position
20
), the aircraft will maintain an altitude above the terrain underlying the aircraft of at least 700 ft to avoid ground proximity alarms. The 700 ft altitude buffer between the aircraft and underlying terrain typically provides desired reaction time for reacting to changes in the elevation of the terrain. However, as the aircraft approaches the selected runway, the minimum altitude that the aircraft must maintain above underlying terrain decreases. As such, when the aircraft is in close proximity to the selected runway, the flight crew will not receive an alert until the aircraft is much closer to the underlying terrain. This reduction of the required altitude above underlying terrain, in turn, reduces the reaction time for the flight crew to react to abrupt changes in elevation.
For example, at 5 nm, (i.e, 4+K), from the selected runway, (see point
22
), the aircraft need only maintain an altitude of 400 ft above underlying terrain to avoid generation of alarms. Further, at positions, (see point
24
), closer to the selected runway, the terrain clearance floor envelope decreases to even lower altitude requirements for the aircraft to maintain above underlying terrain. These reduced altitude requirements further reduce the reaction time for the flight crew to react to abrupt changes in elevation near the selected runway.
While reduction of the minimum altitude between the aircraft and underlying terrain as the aircraft approaches the selected runway is typically not problematic for most landing procedures, it may be problematic in the above example shown in FIG.
2
. Specifically, due to the terrain clearance floor envelope, as long as the aircraft remains at an altitude above underlying terrain that is greater than the altitude defined by the terrain clearance floor envelope, the aircraft can continue to descend as it approaches the selected runway without generating alarms concerning the altitude of the aircraft. As such, if there is an abrupt upward change in the elevation of terrain in close proximity to the selected runway, (see point
25
), the flight crew may not receive an alert from the terrain clearance floor envelope until the aircraft is within the range of 10 to 100 ft above the terrain, depending on distance to the selected runway. In this instance, the alert provided by the ground proximity warning system may not provide the flight crew with a desired time to react to the change in elevation. Specifically, the flight crew may have to maneuver the aircraft in an abrupt fashion to avoid the terrain, which may be unsettl
Bateman C. Don
Gremmert Scott
Ishihara Yasuo
Johnson Steven C.
Hofsass Jeffery
Honeywell International , Inc.
Pham Toan
LandOfFree
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