U.S. patent application number 10/442147 was filed with the patent office on 2004-08-26 for runway overrun monitor and method for monitoring runway overruns.
Invention is credited to Brodegard, William C., Ryan, Dean E..
Application Number | 20040167685 10/442147 |
Document ID | / |
Family ID | 32871904 |
Filed Date | 2004-08-26 |
United States Patent
Application |
20040167685 |
Kind Code |
A1 |
Ryan, Dean E. ; et
al. |
August 26, 2004 |
Runway overrun monitor and method for monitoring runway
overruns
Abstract
A critical point on a runway indicates a point at which an
aircraft may experience a runway overrun if landing beyond the
critical point. A path projection is extended from the aircraft at
a descent slope angle to determine whether the aircraft will land
beyond the critical point at the current descent slope. Timely
alerts may be provided by accounting for the time required to
announce a distance value, and the distance traveled during the
announcement.
Inventors: |
Ryan, Dean E.; (Delaware,
OH) ; Brodegard, William C.; (Delaware, OH) |
Correspondence
Address: |
CONNOLLY BOVE LODGE & HUTZ LLP
SUITE 800
1990 M STREET NW
WASHINGTON
DC
20036-3425
US
|
Family ID: |
32871904 |
Appl. No.: |
10/442147 |
Filed: |
May 21, 2003 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60448906 |
Feb 24, 2003 |
|
|
|
Current U.S.
Class: |
701/16 ; 340/951;
340/972 |
Current CPC
Class: |
G08G 5/0086 20130101;
B64C 25/426 20130101; G08G 5/025 20130101; G01C 23/005
20130101 |
Class at
Publication: |
701/016 ;
340/951; 340/972 |
International
Class: |
G06F 019/00 |
Claims
What is claimed is:
1. A method of providing situational awareness during landing of an
aircraft, comprising: determining a critical point on a runway, the
critical point indicating a point at which if the aircraft lands
beyond the critical point, there is a likelihood of the aircraft
overrunning the runway; determining whether a path projection of
the aircraft intersects the runway in front of or beyond the
critical point; and providing an alert if the path projection
intersects the runway beyond the critical point.
2. The method of claim 1, wherein determining whether a path
projection of the aircraft intersects the runway in front of or
beyond the critical point comprises: periodically making said
determination during the aircraft's approach to the runway.
3. The method of claim 1, wherein determining a critical point on a
runway comprises: determining a required landing distance for the
aircraft.
4. The method of claim 3, wherein determining a required landing
distance for the aircraft comprises: adjusting a landing distance
value according to one or more of the following factors: tailwind
component, runway gradient, runway altitude, and temperature.
5. The method of claim 3, wherein determining whether a path
projection of the aircraft intersects the runway in front of or
beyond the critical point comprises; extending the path projection
from the aircraft at a descent slope angle.
6. The method of claim 5, wherein the descent slope angle is
constant during approach.
7. The method of claim 1, wherein providing an alert comprises:
announcing a runway distance remaining.
8. The method of claim 1, comprising: determining whether the
aircraft exceeds a maximum groundspeed; and providing an alert if
the aircraft exceeds the maximum groundspeed.
9. The method of claim 1, comprising: determining whether a maximum
tailwind component is exceeded; and providing an alert if the
maximum tailwind component is exceeded.
10. The method of claim 1, comprising: determining whether a
maximum crosswind component is exceeded; and providing an alert if
the maximum crosswind component is exceeded.
11. A method of providing timely alert messages in an aircraft
during landing, the method comprising: determining message data
regarding the aircraft's status during a landing phase; determining
aircraft speed; adjusting a message based on the message data
according to the aircraft speed; and announcing the adjusted
message.
12. The method of claim 11, wherein adjusting a message comprises:
determining a time required to announce a message; determining a
distance to be traveled during the required announcement time; and
adjusting the message to reflect the distance traveled.
13. The method of claim 12, wherein determining a distance to be
traveled during the required announcement time comprises:
multiplying aircraft speed by the time required to announce a
message.
14. The method of claim 12, wherein determining aircraft speed
comprises: determining aircraft groundspeed.
15. The method of claim 11, wherein determining aircraft speed
comprises: determining aircraft groundspeed.
16. A method for monitoring for runway overrun when an aircraft is
landing on a runway, comprising: determining an aircraft's position
on the runway after the aircraft has touched down; determining the
aircraft's groundspeed; calculating a runway distance remaining
before the aircraft on the runway; calculating a distance required
to reach a desired speed; and generating an alert if the required
distance is greater than the remaining runway distance.
17. The method of claim 16, comprising: determining the aircraft's
deceleration.
18. The method of claim 17, wherein calculating a distance required
to reach a desired speed comprises: calculating a distance required
to reach a desired speed at said deceleration
19. The method of claim 18, wherein determining an aircraft's
deceleration comprises: calculating the aircraft deceleration
function as a rate of change of said aircraft groundspeed.
20. The method of claim 16, wherein calculating a runway distance
remaining comprises: comparing the aircraft position to a runway
end position; and calculating the distance along a length of the
runway between the aircraft position and the runway end
position.
21. The method of claim 17, comprising: determining a required
deceleration to reach the desired speed; and generating an alert if
the absolute value of the current deceleration is less than the
absolute value of the required deceleration.
22. A method of providing timely alert messages in an aircraft, the
method comprising: determining a range between an aircraft and
traffic; determining a closure rate between the aircraft and the
traffic; adjusting the range according to the closure rate; and
announcing the adjusted range.
23. The method of claim 22, wherein adjusting the range according
to the closure rate comprises: decreasing the range by an expected
decrease in range occurring during announcement of the range.
Description
RELATED APPLICATION
[0001] This application claims priority to the provisional
application assigned attorney docket number 21035-00026, U.S.
application Ser. No. 60/448,906, filed in the United States Patent
and Trademark Office on Feb. 24, 2003, and entitled "RUNWAY OVERRUN
MONITOR AND METHOD FOR MONITORING RUNWAY OVERRUNS."
BACKGROUND
[0002] 1. Technical Field
[0003] The invention relates to aircraft safety equipment and more
particularly to an apparatus and method for increasing flight crew
situational awareness during landing.
[0004] 2. Related Art
[0005] Landing is one of the most demanding tasks in flying. During
the landing process, the aircraft must be brought to a safe and
complete stop. To perform the landing properly, the aircraft must
approach the runway within certain attitude, track, speed, and rate
of descent limits. An approach outside of these limits can result
in a "hard" landing, overrunning the runway end, or otherwise
contacting the runway surface in an uncontrolled manner. Any one of
these events has the potential to cause severe damage to the
aircraft and may additionally result in passenger injuries or
fatalities.
[0006] Landing too fast and landing too far down a runway may
contribute to runway overrun accidents. Pilots are trained to
monitor these conditions during the approach, and to initiate a
go-around maneuver if a safe landing is not assured. The
effectiveness of pilot training depends, however, on the skill and
judgment of the pilot in recognizing a possible runway overrun
condition, and in executing the appropriate response. Pilots with
varying levels of skill are therefore likely to respond differently
to the same scenario.
[0007] In most landing and departure situations, the pilot's vision
is the sole data source for estimating runway position information.
Even with existing high standards for pilot eyesight, some
variation in acuity will occur as the pilot's physical condition,
alertness, and state of rest vary. If the pilot's vision is the
sole source of data used to determine whether a go-around or
aborted takeoff is necessary, then variations in visual acuity,
distractions or poor visibility may reduce the quality of the data
used in the pilot's decision. In addition, a pilot may fly for
years without experiencing a runway overrun, and the pilot may be
slow to recognize a problem during landing.
[0008] Aircraft safety can be improved by mitigating the effects of
differing pilot skill levels and situational awareness during the
landing phase of flight.
SUMMARY
[0009] According to a first aspect, a method of providing
situational awareness during landing of an aircraft comprises
determining a critical point on a runway, the critical point
indicating a point at which if the aircraft lands beyond the
critical point, there is a likelihood of the aircraft overrunning
the runway. If a path projection from the aircraft intersects the
runway beyond the critical point, an alert is provided.
[0010] According to a second aspect, a method of providing timely
alert messages in an aircraft during landing comprises determining
message data regarding the aircraft's status during a landing
phase, determining aircraft speed, adjusting a message based on the
message data according to aircraft speed, and announcing the
adjusted message.
[0011] According to a third aspect, a method for monitoring for
runway overrun when an aircraft is landing on a runway comprises
determining an aircraft's position on the runway after the aircraft
has touched down, determining the aircraft's groundspeed,
determining the aircraft's deceleration, calculating a runway
distance remaining before the aircraft on the runway, calculating a
distance required to reach a desired speed at said deceleration,
and generating an alert if the required distance is greater than
the remaining runway distance.
[0012] Those skilled in the art will appreciate the above stated
advantages and other advantages and benefits of various embodiments
of the invention upon reading the following detailed description of
the embodiments with reference to the below-listed drawings.
[0013] According to common practice, the various features of the
drawings are not necessarily drawn to scale. Dimensions of various
features may be expanded or reduced to more clearly illustrate the
embodiments of the invention.
BRIEF DESCRIPTION OF THE FIGURES
[0014] The present invention is described with reference to the
accompanying drawings. In the drawings, like reference numbers
indicate identical or functionally similar elements.
[0015] FIG. 1 is a schematic side elevational view of a runway
landing environment.
[0016] FIG. 2 is a block diagram of a first embodiment of a runway
overrun monitor.
[0017] FIG. 3 is a top plan view of a portion of the runway landing
environment illustrated in FIG. 1.
[0018] FIG. 4 is a schematic side elevational view of a portion of
the runway landing environment illustrated in FIG. 1, including
several descent slopes.
[0019] FIG. 5 illustrates a method of providing accurately timed
alert messages.
[0020] FIG. 6 illustrates a method of providing situational
awareness after touchdown.
DETAILED DESCRIPTION
[0021] A runway overrun monitor provides an aircraft crew with a
source of reliable and accurate data during the landing phase.
Available information includes, for example, messages notifying the
crew that under current conditions, the aircraft will not have
enough runway to land safely. Information can also include alerts
that the aircraft will exceed a maximum touchdown speed, or that
maximum tailwind or crosswind limits will be exceeded. The above
alerts can be provided automatically by the runway overrun
monitor.
[0022] To minimize cockpit confusion during landing, the runway
overrun monitor may be configured to omit unsolicited, routine
information. The pilot or crew may, however, solicit information
such as, for example, tailwind and crosswind component values,
runway identification, runway remaining for landing, and speed over
the ground.
[0023] FIG. 1 illustrates a runway environment 100. The runway
environment 100 is illustrated as including a runway 110, a runway
start 114, a touchdown zone (TDZ) 115, a critical point 116, an
aircraft path projection 125, a touchdown aim point 130, and a
first checkpoint 150. The touchdown zone 115 is the length of the
runway 110 where aircraft customarily touch down on landing. A
common TDZ length is 75 feet, beginning at 500 feet past the runway
start 114. TDZ lengths and locations on runways vary, however.
[0024] During the landing phase, an aircraft 121 descends along the
path projection 125 to touch down at the touchdown aim point 130.
The touchdown aim point 130 is the location of the intersection of
the path projection 125 with the runway 110. The pilot then uses
the aircraft brakes and reverse engine thrust, if available, to
slow the aircraft 121 to a safe speed. As the aircraft approaches
touchdown, the touchdown aim point may vary along the runway 110.
Thus, the touchdown aim point 130 is a predictor of the position
along the runway 110 at which the aircraft 121 will actually touch
down. Once the aircraft 121 touches down, the distance between the
actual touchdown point and the runway end 120 is the available
runway for slowing the aircraft 121 before it overruns the runway
110. This distance between the predictor touchdown point 130 and
the runway 120 may be referred to as "runway remaining" as the
aircraft 121 approaches touchdown. As discussed below, calculations
for runway distance remaining may be adjusted according to landing
flare. A runway overrun can be generally defined as a situation in
which the aircraft 121 proceeds past the runway end 120 at a
groundspeed too high for safely attempting to turn the aircraft 121
onto a taxiway.
[0025] According to one aspect of the invention, the path
projection 125 of the aircraft 121 is monitored to determine
whether the touchdown aim point 130 is either in front of or beyond
the critical point 116. The critical point 116 may be defined as
indicating a point at which if the aircraft lands beyond the
critical point 116, there is a likelihood of the aircraft
overrunning the runway 110. Alerts are provided if the touchdown
aim point 130 is beyond the critical point 116.
[0026] FIG. 2 illustrates a runway overrun monitor 200 capable of
performing the alert functions described above. The runway overrun
monitor 200 functions to apprise the pilot or crew members of the
status of the aircraft carrying the monitor 200. The runway overrun
monitor 200 comprises a data processor 201 coupled to a source 202
of company or manufacturer supplied runway data, a source 204 of
aircraft performance data, a source 206 of aircraft position data,
and a source 208 of avionics data. The data processor 201 may also
be coupled to alert devices such as an audio indicator 220 and a
visual indicator 222. The audio indicator 220 can be, for example,
a speaker, or a source of audio input coupled to headphones worn by
a pilot. The visual indicator 222 can be, for example, one or more
colored lights on a panel, or a display screen such as an LCD or
CRT monitor. A weight on wheels (WOW) sensor 210 may be coupled to
the processor 201 to provide an indication as to when the aircraft
is airborne.
[0027] The data processor 201 may be coupled to an input device
224. The input device 224 may be used to solicit information from
the monitor 200. The input device 224 may also be used at any time
to request a data update from the runway overrun monitor 200. The
input device 224 may include, for example, a "request update"
button, or one or more keys designated for this purpose. Allowing
the pilot or other operator to request specific updates reduces
unnecessary background noise in the cockpit, while ensuring that
the pilot receives alert information without looking inside the
cockpit and away from the runway. In a preferred embodiment, the
monitor 200 can include a single button that can be used to request
information, and to mute further alerts. The input device 224 can
therefore be used to acknowledge an alert. In a preferred
embodiment, alerts are given only once, however, and
acknowledgement of alerts is not necessary.
[0028] The runway data from the source 202 describes the state of
the runway that the aircraft carrying the runway overrun monitor
200 is preparing to land on or take off from. The runway data may
include, for example, the length, and gradient of the intended
landing runway. The runway data may also include a map of the
airport, which includes data defining the runways at the airport,
including the runway identifications. The runway data can be used
to compare aircraft position with the distance to any of the runway
boundaries, including the aircraft's height above ground in
relation to a runway environment. Runway data can be taken from,
for example, an airport mapping database (AMDB) including a digital
description of the airport geography, such as the location of
runways and a description of the altitude of the runways.
[0029] The aircraft performance data from the source 204 may
include, for example, company policy limits with respect to landing
and stopping distance characteristics of an aircraft as a function
of, for example, aircraft weight, with corrections based on, for
example, wind direction, runway slope, runway surface condition,
atmospheric altitude and outside temperature. The aircraft
performance data may also include a list of manufacturer or company
regulations defining various aspects of flight. For example, a
company regulation may define maximum permissible airspeeds,
groundspeeds, descent angles, minimum runway, required gear and
flap configurations, etc., for different stages of landing.
[0030] In a preferred embodiment, the aircraft operator (the chief
pilot, for example) can input a general required landing distance
for the aircraft. The general required landing distance may be
altered by the processor 201 according to factors such as, for
example, the presence of a tailwind component, altitude, runway
gradient, and air temperature. Additional aircraft performance data
is therefore not required.
[0031] The aircraft position data from the source 206 may include,
for example, aircraft altitude, latitude, longitude, track over the
ground, descent slope and groundspeed. The position data can be
used to calculate the aircraft's vertical and horizontal
acceleration. The monitor 200 may be coupled to one or more of an
inertial navigation system, an altimeter, a global positioning
system receiver, and an accelerometer to obtain aircraft position
data. Position data can be differentiated with respect to time to
obtain velocity, including groundspeed, and acceleration data. The
position data can be in the form of, for example, longitude,
latitude and altitude. Velocity may also be provided directly from
the global positioning system, or from the inertial navigation
system.
[0032] The avionics (more specifically, air data and heading) data
from the source 208 can include, for example, data such as
pressure, airspeed, true airspeed and wind vector (wind vector may
be estimated using the true airspeed, groundspeed, track and
heading) and direction, which may be provided as tailwind/headwind
components, may also be supplied to the monitor 200. The monitor
200 may use this data to determine, for example, tailwind and
crosswind components.
[0033] FIGS. 1, 3 and 4 illustrate an embodiment of a method for
providing situational awareness during landing.
[0034] Referring to FIG. 1, the aircraft 121 is illustrated as
approaching the runway 110. The point 150 illustrates a first
checkpoint, and can serve as a starting point at which the runway
overrun monitor 200 begins monitoring the aircraft's situation
during landing. As an alternative, monitoring may begin when the
visual path point 125 intersects with the touch down zone 115. FIG.
3 is a top plan view of the runway 110.
[0035] According to conventional landing procedures, an aircraft
follows a descent slope during landing. The descent slope is
typically defined as some optimal angle of descent for the
aircraft. For example, descent slopes may be inclined at an angle
in the range of about 3-4.degree.. Maximum (i.e., steepest) descent
slope values for the aircraft 121 may be provided by, for example,
the aircraft operator, such as the owning corporation of the
aircraft 121. Preferably, an aircraft maintains a constant angle of
descent as it approaches the runway.
[0036] The path projection 125 illustrated in FIGS. 1, 3 and 4 is
preferably inclined at the same angle as a preferred descent slope
angle of descent for the aircraft 121. In FIG. 1, the path
projection 125 is at an angle .theta. to horizontal. The path
projection 125 extends from the aircraft 121 and intersects level
(i.e., zero gradient) ground at the angle .theta.. In an ideal
landing, the touchdown aim point 130 would stay at the same
location on the runway 110 throughout the landing procedure. The
path projection 125 is preferably extended at a constant angle
.theta. during the landing operation.
[0037] According to one aspect of the invention, the path
projection 125 is monitored in order to determine whether the
intersection of the path projection 125 with the runway 110 is
before or beyond the critical point 116. The intersection point is
labeled as the touchdown aim point 130. It is significant when the
touchdown aim point 130 is beyond the critical point 116 because if
the aircraft 121 continues on that path projection 125 without
adjustment, the aircraft 121 may not be able to stop safely before
the runway end 120.
[0038] Monitoring may begin, for example, at the point 150. The
point 150 can correspond to the location of the outer marker for a
runway. Such a point can be at a distance of, for example, about 5
miles away from the runway 110. Monitoring may also begin once the
path projection 125 intersects with the TDZ 115, and alerts may be
provided to the pilot or crew of the aircraft 121 when certain
conditions are met.
[0039] FIG. 4 is an isolated view of a portion of the runway 110.
Several descent slopes 125.sub.1, 125.sub.2, 125.sub.3and
corresponding touchdown aim points 130.sub.1, 130.sub.2,
130.sub.3are illustrated, corresponding to times t.sub.1, t.sub.2,
t.sub.3, respectively. As shown FIG. 4, at time t.sub.1, if the
current path projection 125.sub.1, is maintained, the aircraft 121
will land in front of the critical point 116. At time t.sub.2, as a
result of changing conditions, the path projection 125.sub.2has
moved towards the critical point 116, but remains in front of the
critical point 116. At time t.sub.3, the path projection
125.sub.3intersects the runway at a touchdown aim point
130.sub.3beyond the critical point 116. At this time, if the
aircraft 121 continues on its current path projection 125.sub.3,
there is a chance that the aircraft 121 may not have enough runway
to land safely.
[0040] If the monitor 200 detects that the current path projection
125.sub.i indicates that the aircraft 121 is likely to land beyond
the critical point 116, the monitor 200 may issue an unsolicited
alert. The alert may have the form of an audible message, such as a
message stating the amount of runway the aircraft 121 will have
available, after touchdown, to stop the aircraft 121. For example,
the alert message can have the form "RUNWAY REMAINING 4000 FEET."
The alert message should be short and should contain minimal
information so that the pilot is not unnecessarily distracted.
[0041] As the aircraft 121 approaches the runway 110, the monitor
200 may periodically determine whether the touchdown aim point 130
passes over the critical point 116. In general, the monitor 200
issues an alert the first time the touchdown aim point 130 passes
over the critical point 116. It is preferable that further alerts
are not provided for each updating period, because the pilot is
already made aware of the potentially dangerous situation. However,
if after an alert is issued, and the touchdown aim point 130 again
moves in front of the critical point 116 (i.e., runway overrun no
longer likely), further alerts may be provided if the touchdown aim
point 130 once again moves beyond the critical point 116. The
monitor 200 may continue to monitor for runway distance remaining
until touchdown.
[0042] The monitor 200 may monitor other aircraft conditions. For
example, referring to FIG. 1, when the aircraft reaches point 150,
the monitor 200 can determine whether the aircraft 121 is in a
desired configuration for landing. The required configuration can
be defined according to, for example, company regulations, such as
would govern a commercial carrier. The required configuration may
also be defined by standards recommended by the aircraft
manufacturer, or by input by the pilot.
[0043] A configuration check can evaluate the following: whether
aircraft landing gear is down; whether a required flap position is
detected; whether a maximum tailwind component is exceeded; whether
a maximum crosswind component is exceeded; whether the aircraft is
above a maximum altitude; whether the aircraft is exceeding a
maximum airspeed; and whether the aircraft is exceeding a maximum
groundspeed. As discussed above, the monitor 200 may monitor for a
touchdown aim point 130 that passes over the critical point 116.
Each of the above factors or conditions can be selectively
monitored and reported, depending on the usefulness of the
information to the pilot. In general, the monitor 200 will not
provide unsolicited alerts if there are no potential problems
detected for the landing. Exemplary reporting options are discussed
below.
[0044] The configuration check can be termed as a check of whether
the aircraft is "in the slot." "In the slot" is a term indicating
that an aircraft is operating within prescribed airspeed, gear
position, flap position, power setting, and altitude parameters. A
check of whether an aircraft is in the slot is usually made between
the runway outer marker and some distance from the runway.
Referring to FIG. 3, an aircraft in the slot can also indicate that
the aircraft is within an angular range .beta. about the runway 110
centerline 140. In general, when an aircraft is outside of the
angular range .beta., the pilot is not warned. A pilot in this
situation will likely be aware of the aircraft's location outside
of the angular range .beta.. The final approach course is an
imaginary line extending back along a runway centerline from the
approach end of the runway 110. The aircraft 121 can be considered
to "track" the final approach course when the aircraft 121 is
within a certain azimuth range .beta. of the runway centerline 140
(see FIG. 3). The azimuth range .beta. may be, for example, +/-
five degrees. The final approach course may extend, for example,
five miles before the runway 110 out to point 150. A specified
lateral offset l.sub.1from the runway centerline 140 may also be
used to define the final approach course. The offset l.sub.1can be,
for example, about 250 feet.
[0045] At point 150, the aircraft 121 altitude may be too high to
obtain tailwind and crosswind component values that are useful to
evaluate the feasibility of a landing. Tailwind and crosswind
component checks may therefore be delayed until the aircraft 121 is
at a lower altitude.
[0046] Alert messages should be as brief and informative as
possible. For example, if landing gear is not down in the
configuration check, a message "NOT IN LANDING CONFIGURATION, GEAR"
may be provided. Similarly, "NOT IN LANDING CONFIGURATION, FLAPS"
can indicate flaps in the wrong position, or "NOT IN LANDING
CONFIGURATION, AIRSPEED," may indicate an airspeed outside of
recommended parameters, and "NOT IN LANDING CONDITION, ALTITUDE,"
can indicate an altitude outside of recommended parameters.
[0047] Referring to FIG. 1, at a point 160, the monitor 200 may
enable monitoring of additional factors affecting the landing. For
example, point 160 may correspond to a point where the aircraft 121
altitude is lower, in the range of, for example, 500 feet or less.
At this time, tailwind and crosswind values may be more accurately
determined as they affect landing on the runway 110. If a maximum
tailwind or crosswind component value is exceeded, the monitor 200
may issue an alert informing the pilot of the condition. Monitoring
for excessive tailwind or crosswind values may continue until the
aircraft 121 is at a height of about 100 feet. At 100 feet, alerts
may be addressed solely to whether sufficient runway remains for
landing. In general, a tailwind or crosswind alert is given only
once, as repetition may distract the pilot.
[0048] Crosswind alerts can indicate the crosswind component and
direction. For example, a crosswind alert can have the form "RIGHT
CROSSWIND 20 KNOTS." Similarly, a tailwind announcement can have
the form "TAILWIND 10 KNOTS." As stated above, crosswind and
tailwind announcements may be delayed until the aircraft 121 is at
a lower altitude. In one preferred embodiment, tailwind and
crosswind alerts are issued after the aircraft 121 descends below
300 feet, and cease when the aircraft descends below 100 feet.
[0049] The monitor 200 may monitor to determine whether the
aircraft 121 will exceed a maximum touchdown speed or is currently
exceeding a maximum airspeed. Monitoring for exceedance of maximum
touchdown speed can begin at point 150, for example. In one
embodiment, alerting for exceedance of maximum touchdown speed
begins when the aircraft 121 descends to an altitude of about 300
feet. Other altitudes are also appropriate.
[0050] When the aircraft 121 reaches a threshold altitude, all
alerts except for insufficient runway alerts may cease. The
threshold altitude value may be, for example, 100 feet. At this
time, alerts relating to crosswind, tailwind, and groundspeed,
etc., may be extraneous and may distract the pilot.
[0051] The critical point 116 may be determined according to, for
example, operator-recommended landing distances. The critical point
116 is determined as a function of runway length and runway
distance required for the aircraft to land and stop safely.
Required landing distance for an aircraft is dependent upon
aircraft type, runway gradient, airport elevation, density
altitude, established company parameters, and other factors
determining the length of runway required for an aircraft to land
safely. This information can be stored on computer-readable media,
for example, and may be accessible by the monitor 200. The monitor
200 can also adjust the critical point 116 according to prevailing
conditions. For example, the presence of a tailwind increases the
distance required for an aircraft to land, thereby moving the
critical point to the left in FIG. 1. The required landing distance
may also be adjusted according to runway altitude, runway gradient,
and air temperature.
[0052] In determining the critical point 116, the monitor 200 may
account for aircraft flare occurring just before touchdown. The
monitor 200 can account for flare in at least two ways. A first way
to account for flare is to add an expected flare distance to the
landing distance, and increase landing distance accordingly. This
method results in the critical point 116 being moved to the left in
FIG. 1. Alternatively, flare can be accounted for by virtually
shifting the path projection 125 to the right in FIG. 1 by the
expected flare distance.
[0053] The information provided to the pilot should be simple and
as easily understood as possible. Therefore, distances are
preferably rounded off to hundreds, or thousands of feet. For
example, during the time when the aircraft is about to touch down,
measurements of runway remaining are preferably rounded off to the
nearest thousand foot increment. There are at least two ways of
implementing this feature. A first way is to round the runway
remaining figure down, so the pilot has a conservative estimate of
runway remaining. Another is to round up or down, this method being
less preferred. Another method is to time the sounding of an alert
message so the threshold hundred or thousand foot increment message
is accurate when received by the pilot. A method of timing messages
is discussed in detail below with reference to FIG. 5.
[0054] Safety margins can also be programmed into the runway
overrun monitor 200. For example, the pilot or other operator can
program the monitor 200 to consistently underestimate runway
remaining figures by a selected percentage or by a selected
distance.
[0055] The pilot can end alerts from the monitor at any time.
Alerts can be ended at the input 224. The input 224 can act as a
"mute" button by a single press of a button. The pilot may take
this action if he no longer plans on landing. The monitor 200 can
be reactivated when, for example, the aircraft 121 arrives at its
next visual path point.
[0056] The pilot or crew can also solicit information from the
monitor 200 at any time. Solicited information can include any of
the announcements discussed above. Solicited alerts can be
requested, for example, at the input 224. For simplicity of the
monitor 200, a single button can be used as a mute button as
discussed above, and as a means for requesting unsolicited updates.
For example, at a relatively far distance out (e.g., about 10
miles) from the TDZ 115, the pilot can double-press a button on the
input 224 to request a runway identification, the distance to the
TDZ 115, and ground speed. Such an announcement may have the form
"RUNWAY TWO FOUR LEFT, NINE MILES TO TOUCHDOWN, 120 KNOTS OVER THE
GROUND."
[0057] After reaching point 150, which may correspond to a location
of the airport outer marker, the pilot may again solicit
information by a double-press of a button on the input 224. This
further information can include another runway identification, and
groundspeed announcement.
[0058] The relatively high speeds at which the aircraft 121 travels
renders the timeliness of alert messages of high importance. For
example, an aircraft traveling at 150 knots traverses 250 feet per
second. Therefore, any time-offset between a time when the message
is accurate and when the message is actually received by the pilot
can result in the pilot receiving erroneous information.
[0059] FIG. 5 illustrates a method of ensuring that accurate alert
messages are provided to a pilot or other operator. According to
one aspect, the timing of alert messages is calculated so that the
information is accurate when received by the pilot. For example, in
one embodiment, an audible message is presented so that at the end
of the message, the data conveyed in the message is accurate. The
runway overrun monitor 200 disclosed in FIG. 2 can be programmed to
announce messages in accordance with the method discussed
below.
[0060] Referring to FIG. 5, message data is determined in step
S300. The message data may correspond to any of the alert messages
discussed above, and the message data determined in step S300 may
be determined accordingly. For example, the message data can
include a statement regarding runway remaining dRR.
[0061] In step S302, a speed of the aircraft 121 is determined. The
speed can be, for example, the groundspeed or airspeed of the
aircraft 121. In a preferred embodiment, the groundspeed is
determined. The message data and the aircraft speed can be
determined concurrently, as shown in FIG. 5, or serially (not
shown).
[0062] In step S304, the message is adjusted in order to compensate
for factor such as the time required to announce the message, and
for other factors. Step S304 can be determined according to steps
S306-S314 below:
[0063] In step S306, the time at which the message data is accurate
is indexed as to for the piece of information in the message. The
time to can be indexed to account for time involved in calculating
or processing information. For example, a time to for a runway
remaining message can be adjusted to account for the time required
to read, for example, GPS instruments, and to calculate the runway
remaining in the processor 201.
[0064] In step S308, a time t.sub.M required to announce an alert
message is determined. For example, the message "RUNWAY REMAINING
4000 FEET" requires about 2.1 seconds to announce. If the pilot
wants to hear the end of the message--i.e, the word "FEET"--when
the aircraft has 4000 feet remaining, t.sub.M is equal to about 2.1
seconds. The time necessary to understand the massage and to react
could also be considered when determining t.sub.M. If the pilot
wants to hear the word "4000" when the aircraft has 4000 feet
remaining, t.sub.M is equal to about 1.8 seconds. The time required
t.sub.M can therefore be calculated according to operator
preferences. A default setting can be included in the monitor 200
so that t.sub.M is calculated according to the time required to
announce the entire message.
[0065] In step S310, a distance value d.sub.x is determined. The
distance value d.sub.x represents the distance the aircraft 121
travels during the time t.sub.M required to announce an alert
message. Time t.sub.M is calculated according to the aircraft
speed, and aircraft motion may be governed by the following
equation:
d.sub.x=v.sub.xx t.sub.M Equation 1
[0066] In Equation 1, d.sub.x indicates a distance traveled in a
direction aligned the runway 110 length while traveling with an
x-component of velocity v.sub.x.
[0067] In step 312, a distance value d contained in the message is
adjusted by subtracting d.sub.x. If the relevant distance is runway
remaining, the message data can include a statement regarding
runway remaining d.sub.RR. The adjusted runway remaining value
d.sub.RRA is:
d.sub.RRA=d.sub.RRd.sub.x Equation 2
[0068] In step 314, the message data is revised according to the
adjusted runway remaining value d.sub.RRA.
[0069] In step 316, the alert is announced, including the adjusted
runway remaining value d.sub.RRA.
[0070] The method discussed above includes a feedback loop to
address the situation in which the new distance d.sub.RR results in
a new message length t.sub.M. Activation of the feedback loop may
be subject to a threshold change message length .DELTA.t.sub.M in
message length t.sub.M.
[0071] As an alternative to calculating a time t.sub.M for each
distance message having a different distance value d.sub.RR, a
standard time t.sub.M can be assigned for all messages of this
type. This approximation may be made because an announcement of
"RUNWAY REMAINING 4000 FEET" has approximately the same t.sub.M as
"RUNWAY REMAINING 500 FEET."
[0072] The method for providing timely message data described above
can be applied during both solicited and unsolicited
announcements.
[0073] The monitor 200 may also continue to provide situational
awareness after the aircraft 121 has touched down. A method for
providing situational awareness after touchdown is discussed below
with reference to FIG. 6.
[0074] Closure rates between aircraft can be extremely fast. For
example, at a closure rate of 1200 knots, an aircraft travels about
one mile every ten seconds. In a collision alerting system (not
shown), traffic alert announcements may be generated, for example,
when traffic is within about 30 seconds of a point of closest
approach between an aircraft and the traffic. Therefore, the length
of time required to make a position announcement is a significant
part of the time available to avoid the oncoming traffic. Further,
the last item announced in an announcement may be the range between
an aircraft and the traffic, which changes very quickly.
[0075] The closure rate is especially high when the traffic is an
aircraft and the two aircraft are on a collision course. It is
therefore critical in collision alerting systems that closure
ranges are as accurate as possible when presented to the pilot.
Accuracy of range announcements is particularly important because
the pilot's perception of threat is based on the range between the
aircraft and the traffic. Therefore, the closer oncoming traffic
is, the more relevant it is to the pilot.
[0076] In accordance with a present embodiment of a traffic
alerting system, traffic alert announcements are announced based on
a predictive algorithm, similar to the runway remaining
announcements discussed above. In other words, the range
announcements from the traffic alerting system should be made so
that the announced range is accurate at the end of the
announcement, or, concurrently with the announcement of the
range.
[0077] In one embodiment of a collision alerting system, a
collision alerting system adjusts a calculated range between an
aircraft and traffic using a predictive algorithm. The range is
predicted in the following manner:
[0078] First, a detected traffic alerting range R.sub.d between the
aircraft and traffic is determined. Next, a time t.sub.a required
to announce the range R.sub.d is determined. The closing rate CR
between the aircraft and the traffic is then determined. Then, the
detected traffic alerting range R.sub.d is adjusted so that it will
be accurate when the range is actually announced. The actual or
adjusted range R.sub.a can be calculated according to the
formula:
R.sub.a=R.sub.d-CRxt.sub.a Equation 3
[0079] The adjusted range R.sub.a is then announced.
[0080] As discussed above, a standard time t.sub.a may be used,
rather than calculating the actual time required to make an
announcement.
[0081] FIG. 6 illustrates a method for monitoring landing overrun
after touchdown. In step 610 it is determined if the aircraft 121
is landing. This step can be performed by the processor 201
recognizing, for example, a landing gear position, or, by
recognizing a decrease in altitude. The pilot can also manually
input an indication that the aircraft 121 is landing. If the
aircraft 121 is not landing, the method returns to step 610.
[0082] If the aircraft 121 is landing, in step 620 the runway
overrun device 200 monitors to determine whether the aircraft 121
has touched down. This determination is made according to the
sensor inputs available to the processor 201. For example,
referring to FIG. 2, the WOW sensor 210 output can be used to
determine whether the aircraft 121 is airborne. Other devices and
methods useful to determine whether the aircraft 121 is airborne
include a comparison of the aircraft altitude with the altitude of
the terrain at the aircraft's position. If the aircraft 121 has not
yet touched down, the method returns to step 610.
[0083] If the aircraft 121 has reached the ground, the processor
201 calculates a required deceleration distance D.sub.REQ in step
630. The required deceleration distance D.sub.REQ is the distance
that will be traveled by the aircraft 121 in decelerating from the
current groundspeed to a desired groundspeed.
[0084] The desired groundspeed can be, for example, zero, or some
speed that allows the aircraft 121 to turn at the runway end, such
as a maximum taxi speed. The required deceleration distance is
based on runway remaining, and is calculated using the values of
groundspeed upon landing. The time to decelerate to the desired
groundspeed may be determined using the deceleration rate. The
deceleration rate can be measured directly, using, for example, an
accelerometer, or calculated by determining the time derivative of
the measured groundspeed. Aircraft deceleration can be determined
as a deceleration function by extrapolating a curve from three or
more position data points.
[0085] In step 635, the runway distance remaining DRW is
determined. The remaining runway distance D.sub.RW is calculated by
comparing the aircraft position with the data from the source 202
of runway data.
[0086] In step 640, it is determined whether the groundspeed of the
aircraft is less than a maximum taxi speed. If the aircraft 121 is
traveling at a speed below the maximum value, such as, for example,
10 knots, it is likely that the aircraft 121 is taxiing. If so, the
method ends and the runway overrun monitor 200 ceases to monitor
for a runway overrun.
[0087] In step 650, it is determined whether the required
deceleration distance D.sub.REQ is greater than the remaining
runway distance D.sub.RW. If not, the method returns to step 610.
If the required deceleration distance D.sub.REQ is greater than the
remaining runway distance D.sub.RW, an alert is generated in step
660. The warning can comprise, for example, an audio message
broadcast by the audio indicator 220, a visual message displayed by
the visual indicator 222, or a combination audio and visual
message. For example, the audio message can contain an indication
of the calculated runway distance remaining D.sub.RW soon after
touchdown and aircraft groundspeed. The visual indicator 222 can
display similar information, including a running display of the
remaining runway distance D.sub.RW, and, for example, a flashing
warning indicator. Broadcasts of the remaining runway distance
D.sub.RW and the aircraft's groundspeed can be updated
periodically.
[0088] According to the above method, the pilot receives a warning
when the remaining runway distance D.sub.RW is insufficient to
safely decelerate the aircraft 121 at the current deceleration
function. The information from the runway overrun monitor allows
the pilot to increase the rate of deceleration, such as by
increasing the braking force, or by increasing reverse engine
thrust, if available.
[0089] As an alternative to step 650, the processor 201 can
determine whether the aircraft 121 has exceeded a predetermined
groundspeed in conjunction with having less than a specified
remaining runway distance D.sub.RW. For example, if the aircraft
121 is traveling at a rate of 75 knots over ground, and 2,000 feet
of runway remain, a warning can be generated stating the
groundspeed and remaining runway.
[0090] The trigger for generating an alert can be reference to a
table specifying, for example, that at a remaining runway distance
of 2,000 feet, a warning will be generated when aircraft
groundspeed exceeds 70 knots. A table of remaining runway distance
D.sub.RW versus groundspeed can be manually entered by an operator,
or preprogrammed in the processor 201. The above threshold values
for remaining runway distance D.sub.RW and groundspeed can be
adjusted according to airport and runway conditions and aircraft
performance data.
[0091] As an alternative to or in addition to the above embodiment,
the required deceleration for a safe stop can be compared to the
aircraft's actual deceleration. An alert may be provided if the
aircraft's deceleration is not sufficient.
[0092] The foregoing description of the specific embodiments will
so fully reveal the general nature of the invention that others
can, by applying knowledge within the skill of the art (including
the contents of the references cited herein), readily modify and/or
adapt for various applications such specific embodiments, without
undue experimentation, without departing from the general concept
of the present invention. Therefore, such adaptations and
modifications are intended to be within the meaning and range of
equivalents of the disclosed embodiments, based on the teaching and
guidance presented herein.
[0093] It is to be understood that the phraseology or terminology
herein is for the purpose of description and not of limitation,
such that the terminology or phraseology of the present
specification is to be interpreted by the skilled artisan in light
of the teachings and guidance presented herein, in combination with
the knowledge of one of ordinary skill in the art.
* * * * *