Communications: directive radio wave systems and devices (e.g. – Return signal controls external device – Aircraft guidance
Reexamination Certificate
2001-10-11
2002-12-03
Sotomayor, John B. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Return signal controls external device
Aircraft guidance
C342S179000, C342S181000, C701S004000, C340S945000
Reexamination Certificate
active
06489916
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to avionics, and more particularly to altitude displays and terrain awareness warning systems.
BACKGROUND OF THE INVENTION
A conventional altitude display for a terrain awareness warning system (TAWS) for a given aircraft provides a pilot with a visual display of the terrain having an altitude higher than the aircraft, as well as the terrain within some distance, usually 2000′, below an aircraft.
Referring to prior art
FIG. 1
, an environment is shown in which a conventional altitude display could be important. In situation I, an aircraft
12
is flying at an altitude X along a direction vector
16
. In situation II, an aircraft
12
′ is flying at an altitude X′ along a direction vector
16
′. In situation III, an aircraft
12
″ is flying at an altitude X″ along a direction vector
16
″. Finally, in situation IV, an aircraft
12
′″ is flying at an altitude X′″ along a direction vector
16
′″. The aircrafts
12
,
12
′,
12
″, and
12
′″are flying with direction vectors
16
,
16
′,
16
″,
16
′″, respectively, such that an obstruction
14
having height Y is within a forward arc, centered on the respective direction vector, as monitored by the conventional altitude display aboard each respective aircraft.
Starting by considering situation IV, a conventional altitude display would typically give a visual signal as the height Y of the obstruction
14
is greater than the altitude X′″ of the aircraft
12
′″. In other words, X′″ ≦Y. An audible alert may be given as well if suitable criteria regarding time-to-impact of the terrain feature are also met. In all cases, the height Y and altitude X′″ may be measured by radio height, altitude above sea level, or other means, and preferably the same type of measurement, is employed for both distances. The visual signal in this situation would typically be a red area, such as a spot or square, on a cockpit display. The term ‘RED’ is shown in the figure to denote the range of operation which would result in a red area being displayed. The red area would be indicated to be at a range Z and at a bearing corresponding to the direction of the obstruction
14
relative to the centerline of the aircraft
12
′″.
In situation III, a conventional altitude display would also typically give a red visual signal as the height Y of the obstruction
14
is within a predetermined elevation buffer “D” and within a predetermined time-to-impact from the altitude X′″ of the aircraft
12
″. This elevation buffer D is typically 700′ or 1000′ during enroute navigation, and the alert would be given if X″−Y≦D. As before, the red area would be indicated to be at a range Z and at a bearing corresponding to the direction of the obstruction
14
relative to the centerline of the aircraft
12
″. Also as before, an audible signal may also be given if certain criteria are met.
In situation II, a conventional altitude display would typically just display a visual signal as the altitude X′ of the aircraft
12
′ is greater, than the predetermined elevation buffer D from the height Y of the obstruction
14
, by a first distance d
1
. In other words, X′−Y≧D+d
1
. d
1
is also typically 1000′. The aircraft
12
′ would not be considered to be completely free of the obstruction
14
, however, and for this reason the visual signal would be of a cautionary nature. The visual signal would typically be a yellow area, such as a spot or square, on the cockpit display. As such, ‘YELLOW’ indicates this range. As with the red areas, the yellow area would be indicated to be at a range Z and at a bearing corresponding to the direction of the obstruction
14
relative to the centerline of the aircraft
12
′.
Finally, in situation I, a conventional altitude display would typically just display a visual signal as the altitude X′ of the aircraft
12
′ is greater than the height Y of the obstruction
14
by not only the elevation buffer D and the first distance d
1
, but also by a second distance d
2
. In other words, X′−Y≧D+d
1
+d
2
. d
2
is again typically 1000′. The aircraft
12
would be considered to be mostly free of the obstruction
14
, however, and for this reason the visual signal would typically be a green area, such as a spot or square, on the cockpit display. Again, ‘GREEN’ indicates this range. As with the red and yellow areas, the green area would be indicated to be at a range Z and at a bearing corresponding to the direction of the obstruction
14
relative to the centerline of the aircraft
12
.
At higher aircraft altitudes, no colored area, or a black area, would be indicated. Here, ‘NONE’ is shown in the figure to denote this range.
Such altitude displays are clearly useful for warning pilots of impending dangerous terrain. However, such systems fail to account for important factors such as the actual flight path of the aircraft. As a result, their accuracy may be less than desired. For example, if an aircraft is climbing, the above described prior art altitude display may report a red area where one is not warranted. In the same way, if an aircraft is high but descending, the above-described prior art altitude display may display a green area where a red area is warranted.
SUMMARY OF THE INVENTION
The present invention overcomes the disadvantages of the prior art noted above.
In one aspect, the invention is directed towards a method for providing an indication of aircraft height relative to an obstruction in a terrain awareness warning system. The method includes steps of receiving a first datum indicative of a geographic feature of an obstruction, receiving a second datum indicative of a lateral distance of the geographic feature from an aircraft, receiving a third datum indicative of a height of the aircraft, receiving a fourth datum indicative of a flight path of the aircraft, calculating a projected height of the aircraft at the location of the obstruction using the first through fourth data, generating a result signal based on the projected height and the first datum, and displaying a colored indication on a display screen based on the generated result signal.
Implementations of the method may include one or more of the following. The first datum may be a height of the obstruction. The colored indication may be a colored area on a display screen having a color such as red, yellow, green, or black. The elevation buffer may be zero. The receiving a fourth datum may further include resolving the flight path of the aircraft into components including a lateral flight path and a vertical flight path. The method may further include: calculating a flight path angle of the aircraft from the received fourth datum, calculating an effective altitude of the aircraft by adding to the third datum a value equal to the second datum multiplied by the tangent of the flight path angle, generating a first alert signal if the effective altitude is less than the sum of the first datum and a elevation buffer, sounding an audible alarm with the first alert signal, displaying a first colored indication at a display location corresponding to the second datum as the first alert signal, generating a second alert signal if the effective altitude is greater than the sum of the first datum and a elevation buffer but less than a sum of the first datum, the elevation buffer, and a first distance, or displaying a second colored indication at a display location corresponding to the second datum as the second alert signal.
In another aspect, the invention is directed towards a computer program, stored in a machine-readable format, for a terrain awareness warning system. The program causes a computer to: receive a first datum indicative of a geographic feature of an obstruction; receive a second datum indicative of a lateral d
Sandel Avionics, Inc.
Sotomayor John B.
Wieczorek Mark D.
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