Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Aeronautical vehicle
Reexamination Certificate
2002-08-30
2004-11-30
Black, Thomas G. (Department: 3663)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Aeronautical vehicle
C701S301000, C342S357490, C340S963000
Reexamination Certificate
active
06826459
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to ground proximity warning systems and methods for use in aircraft and marine applications and, more particularly, to ground proximity warning systems, methods and computer program products for controllably altering the base width of an alert envelope to account for uncertainties associated with the position of the aircraft or ship.
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 of the aircraft with surrounding terrain or other obstacles.
Although these warning systems are quite useful in providing the flight crew with information concerning potential problems with the navigation of the aircraft, the usefulness of these systems must be balanced against problems associated with the generation of nuisance alarms. Specifically, although it is advantageous to provide the flight crew with as much information as possible concerning terrain and obstacles in the flight path of the aircraft, this information should be delivered to the flight crew in a timely manner, such that the flight crew will pay close attention to the information. If alarms are provided too far in advance to the flight crew concerning terrain that is still far away from the present position of the aircraft, the flight crew may become desensitized to the alarms and may potentially ignore alarms from the ground proximity warning system altogether. Further, the generation of alarms concerning terrain that is still far away from the present position of the aircraft may also add stress and confusion on the flight crew and may overshadow other more critical alarms in the cockpit.
For this reason, at least one ground proximity warning system defines an alert envelope and, more particularly, both a caution envelope and a warning envelope. The imaginary alert envelope moves with the aircraft and is constructed to extend generally forwardly of the aircraft and to define a region in which alerts will be generated if terrain or other obstacles enter by penetrating the alert envelope. In this regard, U.S. Pat. No. 5,839,080 to Hans R. Muller, et al. and assigned to AlliedSignal, Inc. describes an advantageous ground proximity warning system that generates an alert envelope. The contents of U.S. Pat. No. 5,839,080 are hereby incorporated by reference in their entirety.
As described by U.S. Pat. No. 5,839,080 and depicted in
FIGS. 1 and 2
, an alert envelope is defined by a number of parameters, including a look ahead distance (LAD), a base width (DOFF), and a terrain floor (&Dgr;H). In general terms, the look ahead distance defines the distance in advance of the aircraft that the alert envelope extends. Similarly, the terrain floor typically defines a vertical distance below the aircraft, which is utilized during the construction of the floor of the alert envelope. Further, the base width is the lateral width of the alert envelope at a location proximate the aircraft. In one example, the base width of an alert envelope extends laterally 0.125 nautical miles to each side of the aircrafl for a total base width of 0.25 nautical miles with the aircraft centered relative to the base width.
While the base width may be a constant value, at least one ground proximity warning system reduces the base width as the aircraft nears an intended runway on which the aircraft will land. By way of example, this ground proximity warning system reduces the base width in a linear manner from a maximum of 0.25 nautical miles to a minimum of 0.04 nautical miles as the aircraft goes from 4 nautical miles from the intended runway to 2 nautical miles from the intended runway. By reducing the base width of the alert envelope, the ground proximity warning system reduces the overall size of the alert envelope and therefore requires the terrain or other obstacles to be closer to the aircraft, at least in a lateral direction, prior to generating an alert. Since an aircraft that is approaching a runway for a landing may be positioned more closely to terrain or other obstacles as the aircraft follows the desired glideslope than while enroute, the reduction in the base width of the alert envelope reduces the generation of disconcerting nuisance alerts during the landing phase, while still providing alerts for terrain or other obstacles that are actually in the flight path of the aircraft.
As shown in
FIG. 2
, an alert envelope is therefore at least partially defined by a center tine
10
and a pair of outer tines
12
. During relatively level flight in which the absolute value of the roll angle of the aircraft is a relatively small value, such as less than 5°, the center tine points along the ground track of the aircraft. In instances in which the aircraft has a larger roll angle, such as greater than 5°, the center tine is angularly displaced from the ground track by an angle approximating the roll angle to thereby incorporate a lead angle during turning of the aircraft. In either situation, the outer tines generally diverge from the center tine by a predetermined angle. Thus, the alert envelope is somewhat broader for locations in advance of the aircraft than at the current position of the aircraft. As shown in
FIG. 2
, the spacing between the outer tines at a location proximate the current position of the aircraft is defined by the base width, such as 0.25 nautical miles in one example, and the outer tines diverge from the center tine at a predetermined angle, such as 3°, in advance of the aircraft.
As described by U.S. Pat. No. 5,839,080, the ground proximity warning system can construct a pair of alert envelopes, namely, a caution envelope and a warning envelope. While each envelope has a similar shape as described above and depicted in
FIGS. 1 and 2
, the caution envelope typically extends further ahead of the aircraft than the warning envelope and is therefore larger than the warning envelope. Accordingly, the ground proximity warning system will generate cautionary alerts in instances in which the upcoming terrain or other obstacles penetrate the caution envelope, but not the warning envelope. Once the upcoming terrain or other obstacles penetrate the warning envelope, however, the ground proximity warning system will generate a more severe warning alert. As such, a pilot can discern the severity of the alert and the rapidity with which evasive maneuvers must be taken in order to avoid the upcoming terrain or other obstacles based upon the type of alert that is provided, i.e., a cautionary alert or a more severe warning alert.
As will be apparent from FIG.
2
and from the foregoing description of the alert envelope generated by a ground proximity warning system, the alert envelope is at least partially dependent upon the current location of the aircraft. In this regard, the base width of the alert envelope is centered laterally relative to the current position of the aircraft and the base width, in turn, defines the origin of the outer tines of the alert envelope. Unfortunately, the current position of the aircraft cannot be determined with absolute certainty. Instead, the current position of the aircraft is always subject to at least some uncertainty.
The uncertainty associated with the determination of the current position of the aircraft depends upon a number of factors, including the type of navigation system utilized by the aircraft and, in some instances, the phase of the flight, i.e., final approach, terminal area, or enroute. For example, a global positioning satellite (GPS) system can determine the current position of the aircraft with very little uncertainty, irrespective of the phase of the flight. For example, one GPS system can determine the current position of the aircraft to within an uncertainty of 0.054 nautical miles irrespective of the phase of t
Conner Kevin J.
Johnson Steven C.
Black Thomas G.
Honeywell International , Inc.
Mancho Ronnie
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