Patent Publication Number: US-7714744-B1

Title: Systems and methods for generating alert signals in an airspace awareness and warning system

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention pertains to the field of alert signals being provided to the pilot of an aircraft, where such signals are generated by an airspace awareness and warning system. 
   2. Description of Related Art 
   Generally, an aviation regulatory authority or organization possesses the authority of designating and defining airspace. In the United States, the Federal Aviation Administration (“FAA”) establishes and provides the defined dimensions of airspace. Such airspace could be designated as regulatory and non-regulatory special use airspace, where regulatory special use airspace could include prohibited areas and restricted areas and non-regulatory special use airspace data could include military operations areas, alert areas, warning areas, and national security areas. Prohibited areas contain airspace of defined dimensions identified by an area within which the flight of aircraft is prohibited. Such areas are established for security or other reasons associated with the national welfare. Restricted areas contain airspace within which the flight of aircraft, while not wholly prohibited, is subject to restrictions. Activities within these areas must be confined because of their nature or limitations imposed upon aircraft operations that are not a part of those activities or both. Restricted areas denote the existence of unusual, often invisible, hazards to aircraft such as artillery firing, aerial gunnery, or guided missiles. Penetration of restricted areas without authorization from a using or controlling agency may be extremely hazardous to the aircraft and its occupants. 
   An airspace is invisible to the pilot but may be identified by a depiction on aeronautical charts or discussed in other publications which provide aeronautical information. The boundaries of an airspace may be delineated by vertical and horizontal limits. The vertical limits of airspace may be designated by altitude floors and ceilings expressed as flight levels or other appropriate measures such as feet or meters above mean sea level (MSL). The horizontal limits of an airspace may be measured and defined by geographic coordinates or other appropriate references that clearly define their perimeter. An airspace may be in effect for one or more designated time periods or run continuously. 
   The complexity with which an airspace is defined ranges considerably. On one side of the spectrum, the definition of the prohibited airspace of Washington, D.C. is highly complex, irregularly shaped, and defined, in part, by numerous physical landmarks and latitude/longitude points. On the other side of the spectrum, a restricted airspace of Flagstaff, Ariz. is relatively simple, cylindrically-shaped, and defined, in part, by a constant radius extending outward from the center of the airspace which is defined by a latitude/longitude point. In between, the restricted airspaces of Fort Sill, Okla. and Huntsville, Ala. are defined, in part, using four sets of latitude/longitude points. The definitions of each of these exemplary airspaces are presented and discussed below in detail. 
   Airspaces may present safety of flight issues to the pilot of an aircraft. A safety of flight issue could arise in the instance where a pilot&#39;s attention is diverted from flying the aircraft to looking down from the aircraft in an attempt to identify the physical landmarks that demarcate the boundaries of the complex Washington, D.C. airspace. Not only are the boundaries complex but the pilot could lose his or her focus on flying the aircraft and accidentally place the aircraft in an unsafe flight condition. Also, if the aircraft is flying in meteorological conditions that obscure the pilot&#39;s ability to see outside of the aircraft, a pilot may unknowingly and unintentionally penetrate such airspace; the same could occur during nighttime flight operations. Invisible hazards to aircraft such as artillery firing, aerial gunnery, or guided missiles may be present, making the penetration of such airspace extremely hazardous to the aircraft and its occupants. Moreover, if a missile defense system is employed to protect the airspace from unauthorized intrusion, a pilot penetrating the airspace could experience tragic consequences should such system be activated and the missiles engage the aircraft. 
   The embodiments disclosed herein present novel and non-trivial systems and methods which address safety of flight issues related to accidental or inadvertent penetration of defined airspace. 
   BRIEF SUMMARY OF THE INVENTION 
   The embodiments disclosed herein present novel and non-trivial systems and methods for generating and providing alerts in an airspace awareness and warning system (“AAWS”). As disclosed herein, an AAWS provides safety and awareness to the pilot of an aircraft by generating one or more alert signals associated with an aircraft operating near defined airspace. As embodied herein, an airspace alert (“AA”) processor may define two surfaces based upon criteria selected by a manufacturer or end-user: an aircraft airspace alert surface and airspace clearance surface. Both surfaces could be defined as a function of at least one criterion selectable by the manufacturer or end-user, wherein at least one criterion is programmed to include real-time and/or static input factor data provided by at least one system or sensor input from an aircraft. As embodied herein, an aircraft airspace alert surface and an airspace clearance surface may be determined. If one surface penetrates the other, an AA processor may generate an alert signal commensurate or associated with the severity of the alert and provide such signal to a crew alerting system. 
   In one embodiment, a system for generating an alert signal in an AAWS is disclosed. The system could be comprised of data sources for providing input factor data comprising at least one real-time and/or static input factor, navigation data, and airspace data, an AA processor, and crew alerting system. The AA processor could receive input factor data, navigation data, and airspace data, define an airspace clearance surface and at least one aircraft airspace alert surface, generate an airspace alert signal if the airspace clearance surface penetrates an aircraft airspace alert surface, and provide an airspace alert signal to a crew alerting system for visual presentation to the pilot by a display unit, aural presentation by an aural unit, and/or tactile presentation by a tactile unit, including any combination thereof. 
   In another embodiment, a second system for generating an alert signal in an AAWS is disclosed. The system could be comprised of a data source for providing input factor data comprising at least one input factor, a data source of airspace data, an AA processor, and a crew alerting system. The AA processor could receive input factor data, airspace data that is representative of an airspace clearance surface, define at least one aircraft airspace alert surface, generate an airspace alert signal if the airspace clearance surface penetrates an aircraft airspace alert surface, and provide an airspace alert signal to a crew alerting system for visual presentation to the pilot by a display unit, aural presentation by an aural unit, and/or tactile presentation by a tactile unit, including any combination thereof. 
   In another embodiment, a method for generating an alert signal in an AAWS is disclosed. The method could be comprised of an AA processor receiving input factor data comprising at least one input factor, navigation data, and airspace data, defining an airspace clearance surface and at least one airspace alert surface, generating an airspace alert signal if the airspace clearance surface penetrates an aircraft airspace alert surface, and providing an airspace alert signal to a crew alerting system for visual presentation to the pilot by a display unit, aural presentation by an aural unit, and/or tactile presentation by a tactile unit, including any combination thereof. 
   In another embodiment, a second method for generating an alert signal in an AAWS is disclosed. The method could be comprised of an AA processor receiving input factor data comprising at least one input factor, navigation data, and airspace data that is representative of an airspace clearance surface, defining at least one airspace alert surface, generating an airspace alert signal if the airspace clearance surface penetrates an aircraft airspace alert surface, and providing an airspace alert signal to a crew alerting system for visual presentation to the pilot by a display unit, aural presentation by an aural unit, and/or tactile presentation by a tactile unit, including any combination thereof. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  depicts a block diagram of a system for generating an alert signal in an airspace awareness and warning system. 
       FIG. 2  provides exemplary depictions of a first airspace to illustrate vertical or perimeter surface(s) and ceiling of an airspace as described by delineated horizontal limits and designated altitudes. 
       FIG. 3  provides an exemplary depiction of a second airspace to illustrate vertical or perimeter surface(s) and ceiling of an airspace as described by delineated horizontal limits and designated altitudes. 
       FIG. 4  provides exemplary depictions of vertical airspace maneuver profiles and alert surfaces of an aircraft in level flight. 
       FIG. 5  provides top-down exemplary depictions of search volumes along projected flight paths. 
       FIG. 6  provides exemplary depictions of vertical airspace maneuver profiles and alert surfaces of an aircraft in level flight where the airspace and airspace clearance surfaces coincide. 
       FIG. 7  provides exemplary depictions of vertical airspace maneuver profiles and alert surfaces of an aircraft in descending flight. 
       FIG. 8  provides exemplary depictions of horizontal airspace alert surfaces of an aircraft in flight. 
       FIG. 9  provides exemplary depictions of vertical terrain alert surfaces of an aircraft in level flight. 
       FIG. 10  provides exemplary depictions of vertical terrain alert surfaces of an aircraft in level flight where the terrain and terrain clearance surfaces coincide. 
       FIG. 11  provides exemplary depictions of vertical terrain alert surfaces of an aircraft in descending flight. 
       FIG. 12  provides exemplary depictions of horizontal terrain maneuver alert surfaces of an aircraft in flight. 
       FIG. 13  provides a flowchart illustrating a method for generating an alert signal in an airspace awareness and warning system 
       FIG. 14  provides a flowchart illustrating a second method for generating an alert signal in an airspace awareness and warning system 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In the following description, several specific details are presented to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or in combination with other components, etc. In other instances, well-known implementations or operations are not shown or described in detail to avoid obscuring aspects of various embodiments of the invention. 
     FIG. 1  depicts an airspace awareness and warning system (“AAWS”)  100  suitable for implementation of the techniques described herein. The system may be comprised of a navigation system  110 , an airport database  130 , an airspace database  135 , a terrain data source  140 , maneuver profile input factors  150 , an airspace alert (“AA”) processor  190 , and a crew alerting system  195 . 
   A navigation system  110  comprises those systems that provide navigation data information in an aircraft. A navigation system  110  may include, but is not limited to an air/data system, an attitude heading reference system, an inertial guidance system (or inertial reference system), a global navigation satellite system (or satellite navigation system), and a flight management computing system, of all which are known to those skilled in the art. For the purposes of the embodiments herein, a radio altimeter system may be included in the navigation system  110 ; a radio altimeter system is known to those skilled in the art for determining the altitude above the surface over which the aircraft is currently operating. As embodied herein, a navigation system  110  could provide navigation data including, but not limited to, geographic position  112 , attitude  114 , speed  118 , vertical speed  120 , heading  122 , radio altitude  124 , day/date/time  126 , and navigation data quality  128  to an AA processor  190  for subsequent processing as discussed herein. Day/date/time  126  could be data representative of the day, date, or time, or any combination of them, and may be used, for example, for determining whether a defined airspace is in effect. Navigation data quality  128  may include, but are not limited to, accuracy, uncertainty, integrity, and validity for data provided by a navigation system  110 . As embodied herein, aircraft position comprises geographic position (e.g., latitude and longitude coordinates) and altitude. Navigation data may be used, in part, to identify a phase of flight of an aircraft and flight attitude, two parameters which may be used to define minimum airspace clearance distance in an airspace awareness and warning system. 
   An airport database  130  may be used to store airport-related data including, but not limited to, airport and runway information. It should be noted that data contained in any database discussed herein including an airport database  130 , an airspace database  135 , and a terrain database  142  may be stored in a digital memory storage device or computer-readable media including, but not limited to, RAM, ROM, CD, DVD, hard disk drive, diskette, solid-state memory, PCMCIA or PC Card, secure digital cards, and compact flash cards. 
   Data contained in such databases could be loaded while an aircraft is on the ground or in flight. Data contained in such databases could be provided manually or automatically through an aircraft system capable of receiving and/or providing such manual or automated data. Data contained in such databases could be temporary in nature; for example, data representative of a temporary runway closure could be stored in an airport database  130 , a temporary flight restriction in airspace database  135 , and a temporary obstacle in terrain database  142 . Any database used in the embodiments disclosed herein may be a stand-alone database or a combination of databases. For example, data stored in an airspace database  135  could be stored in or combined with an airport database  130 , a terrain database  142 , or with a database used by any other system of the aircraft including, but not limited to, a database associated with a flight management computing system or a terrain awareness and warning system (“TAWS”), including any combination thereof. Examples of TAWS that employ an airport database  130  are provided in U.S. patent application Ser. Nos. 11/904,483; 11/904,491; and 11/904,492. 
   Airport information could include surveyed location and elevation data, and runway information could include surveyed location and elevation data of the runway and runway threshold. Airport-related data may be used, in part, to identify a phase of flight of an aircraft, a parameter which may be used to define airspace clearances in an airspace awareness and warning system. An example of a database which may provide a source of airport-related data as embodied herein may be a navigation database included as part of a flight management computing system. As embodied herein, an airport database  130  could provide airport-related data to an AA processor  190  for subsequent processing as discussed herein. 
   An airspace database  135  may be used to store airspace related data including, but not limited to, information related to regulatory special use airspace area and non-regulatory special use airspace area data. Data contained in an airspace database  135  could be provided to an AA processor  190  for determination of a surface representative of airspace and/or for determination of an airspace clearance surface. In one embodiment, data contained in an airspace database  135  could be representative of an airspace surface. In another embodiment, an airspace database  135  may be comprised of one or more databases, where each database could include data representative of one or more airspace clearance surfaces, where each airspace clearance surface could correspond to a specific phase of flight and flight attitude. 
   Regulatory special use airspace data may be comprised of, in part, prohibited areas and restricted areas. Non-regulatory special use airspace data may be comprised of, in part, military operations areas, alert areas, warning areas, and national security areas. Prohibited areas contain airspace of defined dimensions identified by an area within which the flight of aircraft is prohibited. Such areas may be established for, safety, security, national defense, national welfare, or other reasons. Restricted areas contain airspace within which the flight of aircraft, while not wholly prohibited, is subject to restrictions. Restricted areas may denote the existence of unusual, often invisible, hazards to aircraft such as artillery firing, aerial gunnery, or guided missiles. Penetration of restricted areas without authorization from a using or controlling agency may be extremely hazardous to the aircraft and its occupants. 
   Airspaces are depicted on aeronautical charts or discussed in other operational publications which provide aeronautical information. An airspace may be delineated by vertical and/or horizontal dimensions. The vertical of airspace may be designated by altitude floors and ceilings expressed as flight levels or other appropriate measures such as feet or meters above mean sea level (MSL) or other reference including the surface of the earth. The horizontal dimensions of an airspace may be defined by geographic coordinates (e.g., latitude (“lat.”) and longitude (“long.”)) or other appropriate references that clearly define their perimeter. An airspace may be in effect for one or more designated time periods or run continuously. 
   Generally, an aviation regulatory authority or organization possesses the authority of designating and defining airspace. In the United States, the Federal Aviation Administration (“FAA”) establishes and provides the defined dimensions of airspace. For example, FAA Order 7400.8 entitled “Special Use Airspace” provides a listing of regulatory and non-regulatory Special Use Airspace areas, as well as issued but not yet implemented amendments to those areas. FAA Order 7400.9 entitled “Airspace Designations and Reporting Points” provides a listing of terminal and enroute area designations and reporting points, as well as issued but not yet implemented amendments to those areas. At the time of this writing, both Orders may be obtained on the Internet at http://www.faa.gov/airports_airtraffic/air_traffic/publications. As embodied herein, airspace includes, but is not limited to, any airspace and category of airspace established by an aviation regulatory authority or organization including the airspace and categories of airspace described in FAA Orders 7400.8 and 7400.9. As further embodied herein, an airspace database  135  includes, but is not limited to, data representative of the defined vertical and horizontal limits of any airspace; the time and day or days in which such airspace is in effect could also be included in an airspace database  135 . 
   An airspace database  135  that may be used in AAWS  100  may be an airspace database that is used in conjunction with a terrain awareness and warning system. For example, a TAWS that includes an airspace database is described in a U.S. patent application Ser. No. 12/069,234 filed concurrently with the instant application, entitled “System and Method for Generating Alert Signals in a Terrain Awareness and Warning System,” which is incorporated by reference in its entirety. 
   To demonstrate how an airspace may be defined and the varying levels of complexity of between definitions of airspaces, the prohibited airspace of Washington, D.C. (identified as “P-56”) and the restricted airspace of Fort Sill, Okla. (identified as “R-5601E”) will be presented as defined in FAA Order 7400.8N. The delineated horizontal limits of P-56 begin at the southwest corner of the Lincoln Memorial (lat. 38° 53′20″North (N.), long. 77° 03′02″West (W.)); thence via a 327° bearing, 0.6 mile, to the intersection of New Hampshire Avenue and Rock Creek and Potomac Parkway, NW (lat. 38° 53′45″N., long. 77° 03′23″W.); thence northeast along New Hampshire Avenue, 0.6 mile, to Washington Circle, at the intersection of New Hampshire Avenue and K Street, NW (lat. 38° 54′08″N., long. 77° 03′01″W.); thence east along K Street, 2.5 miles, to the railroad overpass between First and Second Streets, NE (lat. 38° 54′08″N., long. 77° 00′13″W.); thence southeast via a 158° bearing, 0.7 mile, to the southeast corner of Stanton Square, at the intersection of Massachusetts Avenue and Sixth Street, NE (lat. 38° 53′35″N., long. 76° 59′56″W.); thence southwest via a 211° bearing, 0.8 mile, to the Capitol Power Plant at the intersection of New Jersey Avenue and E Street, SE (lat. 38° 52′59″N., long. 77° 00′24″W.); thence west via a 265° bearing, 0.7 mile, to the intersection of the Southwest Freeway (Interstate Route 95) and Sixth Street, SW extended (lat. 38° 52′56″N., long. 77° 01′12″W.); thence north along Sixth Street, 0.4 mile, to the intersection of Sixth Street and Independence Avenue, SW (lat. 38° 53′15″N., long. 77° 01′12″W.); thence west along the north side of Independence Avenue, 0.8 mile, to the intersection of Independence Avenue and 15th Street, SW (lat. 38° 53′16″N., long. 77° 02′01″W.); thence west along the southern lane of Independence Avenue, 0.4 mile to the west end of the Kutz Memorial Bridge over the Tidal Basin (lat. 38° 53′12″N., long. 77° 02′27″W.); thence west via a 285° bearing, 0.6 mile, to the southwest corner of the Lincoln Memorial, to the point of beginning. P-56 also includes the delineated horizontal limits of that area within a ½-mile-radius from the center of the U.S. Naval Observatory located between Wisconsin and Massachusetts Avenues at 34th Street, NW (lat. 38° 55′17″N., long. 77° 04′01″W.). The designated altitudes of the vertical limits of P-56 range from the surface of the Earth to 18,000 feet MSL (i.e., mean sea level), and the airspace of P-56 is in effect continuously. It should be noted that the upper vertical limit may be referred to as a ceiling altitude, the altitude at which the ceiling of the airspace exists over the perimeter delineated by the horizontal limits. 
   An advantage of the embodiments herein and the need for an AAWS  100  is demonstrated quite clearly by showing the complexity of which P-56 is defined. Safety of flight issues could arise in the instance where a pilot&#39;s attention is diverted from flying the aircraft to looking down from the aircraft in an attempt to identify the physical landmarks that demarcate the boundaries of the complex P-56 airspace. Not only are the boundaries complex but the pilot could lose his or her focus on flying the aircraft and accidentally place the aircraft in an unsafe flight condition. Also, if the aircraft is flying in meteorological conditions that obscure the pilot&#39;s ability to see outside of the aircraft, a pilot may unknowingly and unintentionally penetrate such airspace. Moreover, if a missile defense system is employed to protect the airspace of P-56 (or any other designated airspace), a pilot penetrating the airspace could experience tragic consequences should such system be activated and the missiles engage the aircraft. 
   In comparison to the complex definition of P-56, R-5601E is relatively simple. The delineated horizontal limits of R-5601E are described as follows: Beginning at lat. 34° 38′15″N., long. 98° 37′58″W.; to lat. 34° 36′00″N., long. 98° 46′46″W.; to lat. 34° 38′15″N., long. 98° 48′01″W.; to lat. 34° 38′15″N., long. 98° 45′21″W.; to the point of beginning. The designated altitudes of the vertical limits of R-5601E range from 500 feet AGL (i.e., above ground level) to 6,000 feet MSL, and the airspace of R-5601E is in effect from sunrise to 2200, Monday through Friday; other times by NOTAM, an acronym known to those skilled in the art that means “Notice to Airman”—a system employed by the FAA to disseminate time-critical aeronautical information which is of either a temporary nature or not sufficiently known in advance to permit publication on aeronautical charts or in other operational publications. 
   Although the definition of the R-5601E airspace is relatively simple, the same safety of flight issues may nonetheless exist. Although not defined by both physical landmarks and longitude/latitude points such as the P-56 airspace, standard navigation maps or charts may depict physical landmarks that could help the pilot identify the boundaries of the R-5601E airspace or other airspace. For example, in an attempt to locate physical landmarks associated with the airspace boundary, the pilot could lose his or her focus on flying the aircraft and accidentally place the aircraft in an unsafe flight condition. Also, if the aircraft is flying in meteorological conditions that obscure the pilot&#39;s ability to see outside of the aircraft, a pilot may unknowingly and unintentionally penetrate such airspace. Moreover, invisible hazards to aircraft such as artillery firing, aerial gunnery, or guided missiles may be present, making the penetration of such airspace extremely hazardous to the aircraft and its occupants. 
   Continuing with  FIG. 1 , an AAWS  100  could include a terrain data source  140 . Examples of terrain data sources are provided in U.S. patent application Ser. No. 12/069,234 filed concurrently with the instant application, entitled “System and Method for Generating Alert Signals in a Terrain Awareness and Warning System,” which is incorporated by reference in its entirety. A terrain data source may include, but is not limited to, a terrain database  142 , a radar system  144 , or both. Terrain data from the terrain data source  140  may include data representative of terrain, obstacles, or both. Obstacles may include, but are not limited to, towers, buildings, poles, wires, other manmade structures, foliage, and aircraft. 
   A terrain database  142  may be used to store terrain data contained in digital elevation models (“DEM”). Generally, the terrain data of a DEM is stored as grids, and each grid represents an area of terrain. A grid is commonly referred to as a terrain cell. A grid may be of various shapes. For example, a grid may be a cell defined in arc-seconds of latitude and longitude, or a grid may be rectangular, square, hexagonal, or circular. A grid may also be of differing resolutions. For instance, the U.S. Geological Society developed GTOPO30, a global. DEM which may provide 30 arc-seconds (approximately 900 meters) resolution. On the other hand, the Space Shuttle Endeavour in February 2000 acquired elevation data known as Shuttle Radar Topography Mission (“SRTM”) terrain elevation data which may provide generally one arc-second (or approximately 30 meters) resolution, providing much greater detail than that provided with GTOPO30 data set. At the present time, resolutions of one-arc second for SRTM terrain data are available for areas over the United States; for all other locations, resolutions of three arc-seconds (approx. 90 meters) are available. In addition to these public sources of terrain data, there are military and private sources of terrain data. Various vendors and designers of avionics equipment have developed databases that have been, for all intents and purposes, proprietary in nature. 
   Data contained in a terrain data cell may include the value of the highest elevation found within the cell. In an embodiment herein, a terrain database  142  could contain a plurality of terrain cells, each having a value of the highest elevation found within the cell. Data contained in a terrain database  142  could be provided to an AA processor  190  for determination of a surface representative of terrain elevation and/or for the determination of a terrain clearance surface. In one embodiment, data contained in a terrain database  142  could be representative of a terrain surface. In another embodiment, a terrain database  142  may be comprised of one or more databases, where each database could include data representative of one or more terrain clearance surfaces, where each terrain clearance surface could correspond to a specific phase of flight and flight attitude. 
   A radar system  144  may be employed to develop data representative of the terrain. An example of a radar system  144  used as a basis for a TAWS (or a terrain avoidance system) is described in U.S. patent application Ser. No. 11/904,491 which is incorporated by reference to the extent that it teaches the acquisition of terrain data by a radar system. In a radar system, a transceiver could transmit radio waves into the atmosphere via an antenna which, in turn, produces a focused beam. The transceiver may control the direction of the beam by steering the antenna horizontally and vertically. When the signal strikes or reflects off an object such as terrain or an obstacle, part of the radio wave energy is reflected back and received by the antenna. The range of the object may be determined by the transceiver by measuring the elapsed time between the transmission and reception of the signal. The azimuth of the terrain or obstacle may be determined as the angle to which the antenna was steered in the horizontal direction relative to the longitudinal axis of the aircraft during the transmission/reception of the signal. The elevation or elevation angle of the terrain or obstacle may be determined as the angle to which the antenna was steered in the vertical direction relative to the longitudinal axis of the aircraft during the transmission/reception of the signal. As embodied herein, terrain data and obstacle data acquired by a radar system and data representative of altitude  114  or height could be provided to an AA processor  190  for determination of a surface representative of terrain elevation. In another embodiment, the terrain data provided by a radar system  144  could be used in conjunction with a terrain database  142 , an example of which is described in U.S. patent application Ser. No. 11/904,491 which is incorporated by reference to the extent that it teaches such use. In another embodiment; the acquisition of such terrain data could be limited or bounded in the lateral direction (i.e., the direction of the horizontal scan). 
   Input factors  150  are determining factors which may be used to define, in part, an alert surface, a clearance surface, or both as disclosed below in detail. Input factors  150  are determining factors which may be used as input for at least one criterion used in the definition of an alert surface, a clearance surface, of both. Input factors  150  may be provided by a plurality of aircraft system or component thereof. Input factors  150  may include real-time system or sensor data, signal input from a plurality of aircraft systems or sensors, and information from any data base or source. As embodied herein, an input factor  150  could provide data or a signal of any form containing information that may be provided to and received by an AA processor  190 . 
   As embodied herein, input factors  150  include those inputs defined above as being part of the navigation system  110  (e.g., geographic position  112 , attitude  114 , speed  118 , vertical speed  120 , heading  122 , radio altitude  124 , day/date/time  126 , and navigation data quality  128 ). Moreover, any input provided by a navigation system  110  could be considered an input factor for the purposes of the embodiments herein. In other words, a navigation system  110  may be considered as providing a subset of input factors  150 . The presentation of the specific inputs from navigation system  110  should not be construed as an exclusion or limitation to input factors  150 . As embodied herein, input factors  150  may include information from any data or information source available to the AA processor  190  including, but not limited to, an airport database  130 , an airspace database  135 , and a terrain data source  140 . In other words, an airport database  130 , an airspace database  135 , and a terrain data source  140  may be considered as sources providing a subset of input factors  150 . The presentation of specific databases should not be construed as an exclusion or limitation to input factors  150 . 
   In an embodiment herein, inputs factors  150  may be selected a manufacturer or end-user as a determining factor for one or more criteria used in an equation which could be employed in the definition of an alert surface. As embodied herein, a maneuver profile could provide the basis of an alert surface including, but not limited to, an aircraft airspace alert surface and an aircraft terrain alert surface. A maneuver profile may be defined by an equation containing one or more selected criteria, each of which may comprise one or more input factors  150 . 
   In another embodiment herein, inputs factors  150  may be selected a manufacturer or end-user as a determining factor for one or more criteria used in an equation which could be employed in the definition of a clearance surface. As embodied herein, a clearance distance could provide the basis of a clearance surface including, but not limited to, an airspace clearance surface and a terrain clearance surface. Additionally, a clearance distance could be applied to an aircraft airspace alert surface and an aircraft terrain alert surface. A clearance distance may be defined by an equation containing one or more selected criteria, each of which may comprise one or more input factors  150 . 
   When included in an equation, data representative of input factors  150  may be acquired by or through aircraft systems and sensors as discussed above and be provided as input to an AA processor  190 . When received, the AA processor  190  may process the data in accordance with an avoidance maneuver algorithm that contains the equation or equations defining a maneuver profile and an airspace clearance distance. As a result, the AA processor  190  may determine a unique alert surface, clearance surface, or both based upon the application of the real-time dynamic or static input factors  150 . 
   One or more maneuver profiles may be defined using one or more selected criteria, each of which may be dependent on one or more input factors  150 . The application of such criteria and input factors  150  by an AA processor  190  may determine an alert surface that represents real-time predictable and achievable aircraft performance using input factors  150 . Although a manufacturer or end-user may define a maneuver profile using one criterion such as a constant climb gradient (as will be discussed below in detail) that may be independent of input factors  150 , the advantages and benefits of the embodiments herein exploit the ability of an AA processor  190  to receive a plurality of available input factors  150 , apply them to a maneuver profile defined and contained in an algorithm, and determine an alert surface unique to actual conditions of flight operations as measured by the values of the input factors  150 . The advantages and embodiments disclosed herein apply equally to the formation of a clearance surface. 
   To provide a simple example of how input factors  150  may be used in the embodiments herein, suppose a maneuver profile is defined with criteria comprising an aircraft&#39;s maximum rate of climb or angle of climb over a given horizontal distance. Those skilled in the art understand that this climb performance may be affected by a plurality of factors including, but not limited to, altitude, attitude, temperature, aircraft speed, and winds aloft. Here, determining factors representing altitude  114 , attitude  116 , speed  118 , temperature  152 , and winds aloft  154  may be provided as input factors  150  to AA processor  190  for subsequent processing in accordance with the criteria that defines the maneuver profile. Because altitude  114  and temperature  152  could affect climb performance, speed  118  could affect any maneuver designed for transition to best rate of climb or angle of climb speed, and winds aloft  154  and speed  118  could affect the horizontal distance over which the climb performance may be achieved, an AA processor  190  is able to define and project a unique alert surface in front of the aircraft that is real-time because it is based upon input factors  150 . As will be discussed below in detail, if an alert surface is penetrated by an airspace clearance surface (which the AA processor  190  has defined based upon, in part or in whole, data provided by an airspace database  135 ), then the processor may generate an alert signal and provide such signal to a crew alerting system  195 . 
   In the following paragraphs, other examples of criteria and performance factors are provided to illustrate the ability with which a manufacturer or end-user may define a maneuver profile as embodied herein. These illustrations are intended to provide exemplary criteria and performance factors that may be used in an AAWS  100 , and are not intended to provide a limitation to the embodiments discussed herein in any way, shape, or form. 
   In one example, a maneuver profile could include meteorological or environmental criteria including, but not limited to, air density  184  and winds aloft  154  factors, where air density  184  may determined by such factors as altitude  114 , temperature  152 , barometric pressure  156 , and dew point  158 , and winds aloft  154  may determined by such factors as wind direction  160  and wind speed  162 . As noted above, input factors  150  may include some of those inputs provided to an AA processor  190  by a navigation system  110 , even though they are not enumerated under item  150  of  FIG. 1 ; input factors that could affect the performance of the aircraft may include some inputs that are provided by any aircraft system other than a navigation system  110 . As embodied herein, one or more input factors  150  could be included in the computation of another input factor. For instance, winds aloft  154  could have been considered in a computation of speed  118 , and barometric pressure  156  could have been considered in a computation of altitude  114 . In such instances, an AA processor  190  may be programmed to accept only one of these factors. 
   In another example, a maneuver profile could include criteria related to determination of day and night. If so, input factors could include, but are not limited to, geographic position  112  and day/date/time  126 . In another example, a maneuver profile could include weight and balance criteria. If so, input factors  150  could include, but are not limited to, data representative of aircraft empty weight  164 , center of gravity (“CG”)  166 , weight of fuel  168 , and weight of cargo  170 . In another example, a maneuver profile could include aircraft configuration and system criteria. If so, input factors  150  could include, but are not limited to, data representative of an aircraft&#39;s flap and slat  174 , speed brake  176 , and landing gear  178  configurations. In another example, a maneuver profile could include engine performance criteria. If so, input factors  150  could include, but are not limited to, data representative of engine performance or status  180  or available thrust. In another example, a maneuver profile could include traffic information criteria associated with systems such as, but not limited to, Automatic Dependent Surveillance-Broadcast (ADS-B), Automatic Dependent Surveillance-Rebroadcast (ADS-R), Traffic Information Services-Broadcast (TIS-B), Aircraft Collision Avoidance System (ACAS), or other sensors such as radar, forward looking infrared (FLIR), and camera. If so, input factors  150  could include, but are not limited to, data representative of traffic location, direction of flight, and speed  182 . 
   In another example, a maneuver profile could include criteria related to phase of flight and flight attitude which are discussed below in detail. In another example, a maneuver profile could include criteria related to a specific maneuver or flight profile. If so, input factors could include, but are not limited to, data representative of a standardized arrival and departure procedure, an instrument approach procedure, a missed approach procedure, and a special operational approach procedure such as an RNP approach, each of which could be provided to an AA processor  190  from data provided by a navigation system  110 . In another example, a maneuver profile could include criteria related to the type of threat which could be encountered by the aircraft. If so, input factors could include, but are not limited to, data representative of airspace, terrain, and obstacles, each of which could be provided to an AA processor  190  from data provided by an airspace database  135  and/or a terrain data source  140 . 
   In another example, a maneuver profile could include criteria related to limiting the vertical or the horizontal distances of the profile. If so, input factors  150  could include, but are not limited to, data representative of the absolute ceiling of the aircraft (which may be provided as a constant which could be a constant offset by other criteria discussed above which could affect aircraft climb performance), distance to an airport of intended landing, or speed  118  which could be derived by an AA processor  190  from data provided by a navigation system  110  and airport database  130 . 
   An AA processor  190  may be any electronic data processing unit which executes software or source code stored, permanently or temporarily, in a digital memory storage device or computer-readable media (not depicted herein) including, but not limited to, RAM, ROM, CD, DVD, hard disk drive, diskette, solid-state memory, PCMCIA or PC Card, secure digital cards, and compact flash cards. An AA processor  190  may be driven by the execution of software or source code containing algorithms developed for the specific functions embodied herein. Common examples of electronic data processing units are microprocessors, Digital Signal Processors (DSPs), Programmable Logic Devices (PLDs), Programmable Gate Arrays (PGAs), and signal generators; however, for the embodiments herein, the term processor is not limited to such processing units and its meaning is not intended to be construed narrowly. For instance, a processor could also consist of more than one electronic data processing units. As embodied herein, an AA processor  190  could be a processor(s) used by or in conjunction with any other system of the aircraft including, but not limited to, a processor(s) associated with a flight management computing system, an aircraft collision avoidance system, a TAWS, or any combination thereof. 
   An AA processor  190  may receive input data from various systems including, but not limited to, navigation system  110 , an airport database  130 , an airspace database  135 , a terrain data source  140 , and maneuver profile input factors  150 . An AA processor  190  may be electronically coupled to a navigation system  110 , an airport database  130 , an airspace database  135 , a terrain data source  140 , and maneuver profile input factors  150  to facilitate the receipt of input data. It is not necessary that a direct connection be made; instead, such receipt of input data could be provided through a data bus or through a wireless network. 
   A crew alerting system  195  includes those systems that provide, in part, aural, visual, and/or tactile stimulus presented to attract attention and convey information regarding system status or condition. A crew alerting system  195  may include, but is not limited to, an aural alert unit for producing aural alerts, a display unit for producing visual alerts, and a tactile unit for producing tactile alerts. Aural alerts may be discrete sounds, tones, or verbal statements used to annunciate a condition, situation, or event. Visual alerts may be information that is projected or displayed on a cockpit display unit to present a condition, situation, or event to the pilot. Tactile alerts may be any tactile stimulus to present a condition, situation, or event to the pilot. In addition, alerts may be based on conditions requiring immediate crew awareness or attention. Caution alerts may be alerts requiring immediate crew awareness in which subsequent corrective action will normally be necessary. Warning alerts may be alerts for detecting terrain threat that requires immediate crew action. Both caution and warning alerts may be presented as aural alerts, visual alerts, tactile alerts, or in any combination thereof. When presented visually, one or more colors may be presented on a display unit indicating one or more levels of alerts. For instance, amber or yellow may indicate a caution alert and red may indicate a warning alert. 
   In one embodiment, an aural alert could call out “caution, airspace” when the conditions for a caution alert have been met or “warning, airspace” when the conditions for a warning alert have been met. In another embodiment, a visual message could display “caution, airspace” text when the conditions for a caution alert have been met or “warning, airspace” text when the conditions for a warning alert have been met. In another embodiment, a text message could be displayed in color, e.g., the “caution, airspace” text could be displayed in amber and the “warning, airspace” could be displayed in red. In another embodiment, the terrain that is causing the alert could be indicated visually, aurally, and/or tactilely, in any combination. In another embodiment, the aural and visual alerts could be presented simultaneously. In another embodiment, the alert could be issued along with one or more recommendations and/or guidance information for responding to the alert condition including, for example, the audio and/or visual indication of “Warning, airspace. Pull-up and turn left.” 
   The advantages and benefits of the embodiments discussed herein may be illustrated by showing examples of using maneuver profiles and alert surfaces in an airspace awareness and warning system. The drawings of  FIGS. 2 and 3  provide two exemplary airspaces to illustrate vertical or perimeter surface(s) and ceiling of an airspace as described by delineated horizontal limits and designated altitudes. For the purpose of illustration only, the surface of the Earth is shown as flat in the drawings of  FIGS. 2 and 3 . 
     FIG. 2A  provides an exemplary three-dimensional depiction of restricted airspace in the vicinity of Huntsville, Ala. (identified as “R-2104C”). The designated altitudes of the vertical limits of R-2104C range from the surface of the Earth to 12,000 feet MSL. The vertical faces of the airspace represent perimeter surfaces of the airspace, and the horizontal face (shown as the shaded surface) represents the ceiling. Although the “floor” of the airspace is not depicted, it is represented by the surface of the Earth bounded by the horizontal delineations. 
     FIG. 2B  provides an exemplary depiction of the perimeter or horizontal boundary of R-2104C as viewed from the top. The delineated horizontal limits of R-2104C are described with the following latitude and longitude coordinates: Beginning at lat. 34° 41′25″N., long. 86° 42′57″W.; to lat. 34° 42′00″N., long. 86° 41′35″W.; to lat. 34° 38′40″N., long. 86° 41′00″W.; to lat. 34° 38′40″N., long. 86° 43′00″W.; to the point of beginning. The airspace of R-2104C is in effect from 0600 to 2000 local time, Monday through Saturday; other times by NOTAM 6 hours in advance; NOTAM is an acronym known to those skilled in the art that means “Notice to Airman”—a system employed by the FAA to disseminate time-critical aeronautical information which is of either a temporary nature or not sufficiently known in advance to permit publication on aeronautical charts or in other operational publications. 
     FIG. 3  provides an exemplary three-dimensional depiction of restricted airspace in the vicinity of Flagstaff, Ariz. (identified as “R-2302”). The delineated horizontal limits of R-2302 consist of a circular area with a 6,600 foot radius centered at lat. 35° 10′20″N, long. 111° 51′19′W. The designated altitudes of the vertical limits of R-2302 range from the surface of the Earth to 10,000 feet MSL, and the boundary is in effect from 0800 to 2400 Mountain Standard Time (MST), Monday through Saturday. The cylindrical vertical face of the airspace represents perimeter surface of the airspace, and the horizontal face (shown as the shaded surface) represents the ceiling. Although the floor or the airspace is not depicted, it is represented by the surface of the Earth bounded by the horizontal delineations. 
   Although the surface of the Earth provides the floor of the illustrative airspaces depicted in the drawings of  FIGS. 2 and 3 , the floor of an airspace may not be defined down to the surface of the Earth. For example, the floor of the R-5601E airspace discussed above is 500 feet above ground level (AGL). 
   The drawings of  FIGS. 4A through 4C  provide exemplary maneuver profiles which may serve as the basis for establishing alert surfaces. The drawings provide an example of a maneuver profile in a vertical direction that may used for airspace avoidance. 
     FIG. 4A  provides an illustration of a simple maneuver profile. Item  202  illustrates a maneuver profile defined as a constant climb gradient such as 6 degrees. When viewed in isolation, maneuver profile  202  is a simple profile comprising a single criterion independent of any input factor including altitude  114 . Without an input factor, a maneuver profile  202  could be the same as alerting surface. 
   In  FIGS. 4B and 4C , maneuver profile  202  has been redefined by incorporating two criteria into each profile: pilot reaction time and a G-Force pull-up maneuver. As shown in  FIGS. 4B and 4C , the maneuver profiles will shift to the right to accommodate a horizontal distance contributed by the addition of the two criteria. Because the magnitude of the distance of each criterion may be dependent on at least one input factor  150  such as speed  118 , such factor could be provided as an input to the AA processor  190  for the computation and definition of an alert surface. 
   In  FIG. 4B , maneuver profile  204  includes a pilot reaction time  206  of 3 seconds and a G-force pull-up maneuver  208  of 0.25 g, where g is the value of the acceleration of gravity which is nominally approximately 32.2 feet per second squared (ft/s 2 ) on earth. In  FIG. 4C , maneuver profile  210  includes a pilot reaction time  212  of 13 seconds and a G-force pull-up maneuver  214  of 0.25 g. As embodied herein, the inclusion of criteria such as pilot reaction time and G-force pull-up maneuver in maneuver profiles  204  and  210  could be selected by a manufacturer or an end-user. It should be noted that the values 3 and 13 seconds, 0.25 g, and  10  nautical miles (NM) have been selected for the sole purpose of illustration and do not establish a limit to the embodiments herein. 
     FIGS. 4D through 4F  provide exemplary projections of two alerting surfaces of an aircraft operating at 4,000 feet in level flight and 500 knots which could be represented by such input factors as altitude  114 , attitude  116 , and speed  118 . As shown, the aircraft is approaching an airspace  216  (shown with diagonal hash marks) of higher altitude along its projected flight path. As embodied herein, only one alerting surface may be sufficient for a generation of an alert signal by an AA processor  190  and for the receiving of such signal by a crew alerting system  195 . A first alert surface  218  is based upon maneuver profile  210 , and a second alert surface  220  is based upon maneuver profile  204 . As shown in  FIG. 4D , a first alert surface  218  could be associated with a caution-type alert, and as discussed above, a caution alert may require immediate crew awareness and subsequent corrective action. Likewise, a second alert surface  220  could be associated with a warning-type alert, and as discussed above, a warning alert may require immediate crew awareness and immediate crew action. 
   Airspace  216  of  FIGS. 4D through 4F  comprises of a surface representative of the vertical or perimeter surface(s) and ceiling corresponding to the surface(s) and ceiling data that could be provided by an airspace database  135 .  FIGS. 4D through 4F  provide an exemplary depiction of an airspace clearance surface  222  that may be projected vertically above airspace  216  at an airspace clearance distance  224  to provide vertical separation. Although not depicted, an airspace clearance surface could also be projected horizontally at a clearance distance to provide horizontal separation. Additionally, an airspace clearance surface could be projected vertically below an airspace where the floor of such airspace is sufficiently above the surface of the Earth to permit aircraft operations below it. 
   As embodied herein, an airspace clearance distance  224  is optional and does not have to be employed. If not employed, an airspace clearance surface  222  could be considered the same as the airspace surface  216  or coinciding with the airspace surface  216 , and receipt of airspace data could constitute the receipt of data representative of an airspace clearance surface  222 . For example, a manufacturer or end-user could rely only on a maneuver profile(s) profiles that define an alert surface(s) to provide clearance. In another example, an airspace database  135  may include data representative of one or more airspace clearance surfaces, and the data provided could be based upon at least one input factor data  150 . In such an example, data representative of airspace clearance surface(s) could be stored in an airspace database  135  corresponding to specific phases of flight, flight attitudes, or both as discussed below. 
   If employed, however, the value of an airspace clearance distance  224  may not remain constant between take-off and landing. Instead, the value of an airspace clearance distance  224  could depend on a plurality of operational criteria or other criteria. For example, an airspace clearance distance may be determined by input factors  150  used to determine the following criteria: phase of flight (e.g., terminal, approach, departure, and enroute), flight attitudes (e.g., level, descending, or climbing flight), or both. Input factors provided for these criteria could include geographic position  112 , altitude  114 , attitude  116 , speed  118 , vertical speed  120 , and input from an airport database  130 . Examples of differing clearance distances and a possible dependency based upon different phases of flight and flight attitudes for terrain avoidance are illustrated with the minimum performance standards of a TAWS published by the FAA in TSO-C151b. 
   A terminal phase of flight could exist when the aircraft position is a pre-defined distance (e.g., 15 nautical miles) or less from the nearest runway while the range to the nearest runway threshold is decreasing and the aircraft is operating at or below (lower than) an upper terminal phase boundary altitude, where the value of the upper terminal phase boundary altitude varies as a function of height above runway and distance to the runway, which could be determined by the AA processor  190  based upon navigation system  110  data and airport database  130 . Generally, the terminal phase of flight ends where the approach phase begins. 
   An approach phase of flight could exist when the aircraft is a pre-defined distance (e.g., 5 nautical miles) or less to the nearest runway threshold, the height above the nearest runway threshold location and elevation is equal to or less than a pre-defined altitude (e.g., 1,900 feet), and distance to the nearest runway threshold is decreasing. 
   A departure phase of flight could exist if an aircraft is on the ground upon initial power-up. A reliable parameter or a combination of parameters may be used to determine whether or not the aircraft is on the ground. For example, one parameter which could initially determine the aircraft to be on the ground could be a signal generated by a weight-on-wheels switch  186  (“squat switch”) to indicate whether or not the aircraft is on the ground. Another parameter could be the radio altitude  124 . Other parameters such as speed  118 , altitude  116 , geometric position  112 , and information contained in an airport database  130 , airspace database  135 , and/or a terrain data source  140  could be used to determine if the aircraft is on the ground or airborne. For example, an aircraft could be “on the ground” if it is operating at a speed less than 35 knots and altitude within +/−75 feet of field elevation or nearest runway elevation. Similarly, an aircraft could be “airborne” if it is operating at a speed greater than 50 knots and altitude 100 feet greater than field elevation; in this example, it can be reliably determine that the aircraft is operating in the departure phase of flight. Other parameters which may be considered are climb state, and distance from departure runway. Once the aircraft reaches a pre-defined altitude (e.g., 1,500 feet above the departure runway), the departure phase could end. 
   An enroute phase of flight may exist anytime the aircraft is more than a pre-defined distance (e.g., 15 nautical miles) from the nearest airport or whenever the conditions for terminal, approach and departure phases of flight are not met. 
   As embodied herein, the value of an airspace clearance distance  224  may depend on a phase of flight and flight attitude. For example, if an aircraft is operating in the enroute phase of flight, a vertical airspace clearance distance  224  could be 700 feet when operating in a level flight attitude and 500 feet when operating in a descending flight attitude. In another example, if an aircraft is operating in the terminal phase of flight, a vertical airspace clearance distance  224  could be 350 feet when operating in a level flight attitude and 300 feet when operating in a descending flight attitude. In another example, if an aircraft is operating in the approach phase of flight, a vertical airspace clearance distance  224  could be 150 feet when operating in a level flight attitude and 100 feet when operating in a descending flight attitude. The value of an airspace clearance distance  224  may depend on the phase of flight and not flight attitude. For example, if an aircraft is operating in the departure phase of flight, an airspace clearance distance  224  could be set to one value (e.g., 100 feet) irrespective of flight attitude. It should also be noted that level flight attitude may or may not include aircraft operating at relatively low vertical speeds and the values may differ across the phases of flight. For example, an aircraft climbing or descending at a rate of 500 per minute or less may be considered as operating in level flight in one phase of flight but not in another. 
   The above embodiments and discussion with respect to phases of flight and values of airspace clearance distances  224  are illustrations intended solely to provide examples and are in no way intended to be limited to those discussed and presented herein. As embodied herein, an AA processor  190  may determine phase of flight, flight attitude, and airspace clearance distance data using algorithms programmed in executable software code. Those skilled in the art will appreciate the ability and ease with which executable software code may be reprogrammed or modified to facilitate subsequent or concurrent performance standards without affecting or expanding the scope of the embodiments discussed herein. 
   A manufacturer or end-user may select one or more alternative criteria. For example, an aircraft with poor climb performance may use different criteria in defining an airspace clearance surface, and input factors  150  associated with climb performance could be provided such as weight and balance criteria as discussed above. In another example, a reduced airspace clearance may be needed to accommodate user-specific operations. For instance, a specific maneuver or flight profile such as a precision approach that is coupled to an autoflight system (and not hand flown) may allow an aircraft to fly closer to an airspace rather than a hand-flown, step-down approach; as such, criteria including inputs factors  150  of data representative of the precision approach or status of the autoflight system could be determining factors of an airspace clearance distance. In another example, helicopter operations could provide special operations that necessitate one or more criteria in determining an airspace clearance distance. As embodied herein, aircraft includes any vehicle capable of controlled-flight. 
   In another example, a maneuver profile could include criteria related to determination of day and night as discussed above. In another example, an airspace clearance distance  224  could include meteorological or environmental criteria and associated input factors  150  as discussed above. In another example, an airspace clearance distance could include aircraft configuration and system criteria and associated input factors  150  as discussed above. In another example, an airspace clearance distance  224  could include aircraft configuration and system criteria and associated input factors  150  as discussed above. In another example, an airspace clearance distance  224  could include engine performance criteria and associated input factors  150  as discussed above. In another example, an airspace clearance distance  224  could include engine performance criteria and associated input factors  150  as discussed above. In another example, an airspace clearance distance  224  could include traffic information criteria associated with systems and associated input factors  150  as discussed above. In another example, an airspace clearance distance  224  could include airspace criteria and associated input factors  150  as discussed above. As an operational example of AAWS  100 , when taking off from runway number 1 at Ronald Reagan Washington National Airport, an aircraft is required under one departure procedure (at the time of this writing) to make a left turn as soon as possible after taking off from Runway 1 so as to avoid P-56 (previously described), which is located approximately 1.5 nautical miles north of the airport. Should the left turn not be executed because, for example, the flight crew was distracted by an engine failure on take off, the AAWS  100  may provide an alert signal to the crew alerting system  195  such that the crew or auto-flight system could maneuver the aircraft within the achievable performance capabilities of the aircraft to avoid entering airspace P-56. The AA processor  190  could determine the achievable performance capabilities of the aircraft taking into account input factors  150  that may include, but are not limited to, aircraft geometric position  112 , altitude  114 , attitude  116 , speed  118 , temperature  152 , barometric pressure  156 , wind direction  160 , wind speed  162 , aircraft empty weight  164 , CG  166 , weight of fuel  170 , weight of cargo  172 , flap/slat  174 , and engine performance  180 . 
   In the preceding paragraphs, the examples of criteria and performance factors are provided to illustrate the ability with which a manufacturer or end-user may define an airspace clearance distance  224  as embodied herein. These illustrations are intended to provide exemplary criteria and performance factors that may be used in an airspace awareness warning system  100 , and are not intended to provide a limitation to the embodiments discussed herein in any way, shape, or form. 
     FIGS. 4E and 4F  provide exemplary depictions of events in which an airspace clearance surface  222  penetrates two alert surfaces as the aircraft approaches airspace  216 , where each event triggers an alert that may be provided to the pilot by a crew alerting system  195 . In an embodiment of  FIG. 4E , a first surface penetration  226  has occurred where the airspace clearance surface  222  has penetrated a first alert surface  218  as the aircraft approaches airspace  216 . Because the first alert surface  218  is associated with a caution alert in this example as discussed above, an AA processor  190  could generate a caution alert signal and provide such signal to a crew alerting system  195  as a result of the penetration. As the aircraft continues to approach airspace  216  as shown in  FIG. 4F , a second surface penetration  228  has occurred where the airspace clearance surface  222  has penetrated a second alert surface  220 . Because the second alert surface  220  is associated with a warning signal as discussed above, an AA processor  190  could generate a warning signal and provide such signal to the crew alerting system  195  as a result of the penetration. 
   As discussed above, a first alert surface  218  and a second alert surface  220  have been based upon maneuver profiles  210  and  204 , respectively, where each has been based on maneuver profile  202  of a constant angle climb (e.g., six degrees) having a distance of 10 NM. As embodied herein and discussed above, however, the advantages of the embodiments herein may incorporate any profile which may be used or defined as a maneuver profile. A manufacturer or end-user of an AAWS  100  could establish or configure a plurality of maneuver profiles; on the other hand, a manufacturer or end-user of the aircraft may wish to provide a single maneuver profile under all conditions to simplify pilot training. As embodied herein, a maneuver profile may comprise of one or more vertical maneuvers, one or more horizontal maneuvers as discussed below in detail, or it may be a combination of one or more vertical and horizontal maneuvers. 
   The drawings of  FIG. 5  provide top-down exemplary depictions of search volumes within which potentially hazardous airspace such as, for example, that airspace shown in  FIGS. 4E through 4F  that penetrated the alert surfaces  226  and  228 , the triggering events that cause an AA processor  190  to generate and provide an alert signal to a crew alerting system  195  to alert the pilot. A search volume could be defined by a manufacturer or end-user and may include horizontal limits, vertical limits, or both, and may be applied in terrain avoidance applications as discussed below in detail. A few examples of such volumes include, but are not limited to, those depicted in  FIGS. 5A through 5K . A search volume could comprise lateral limits (identified as “LL 1 ” and “LL 2 ”) along a projected flight path (identified as “P”), a back limit (identified as “BL”), and a forward limit (identified as “FL”) as shown in  FIGS. 5A through 5K . These illustrations are intended to provide limits that may be used in an AAWS  100 , and are not intended to provide a limitation to the embodiments discussed herein in any way, shape, or form. Moreover, these illustrations could apply equally for terrain avoidance as discussed below in detail. 
   Lateral, forward, and back limits could be made a function of one or more of the same criteria and one or more input factors of a maneuver profile as discussed above. Forward and back limits may vary between lateral limits as shown in  FIGS. 5A through 5C . In another example, a forward limit may remain constant by forming an arc between the lateral limits as shown in  FIGS. 5D and 5E . In another example, the back limit may be established behind the aircraft position received from a navigation system  110  to accommodate uncertainty in the aircraft position as indicated by navigation data quality  128 , and/or uncertainty in the airspace database  135  or terrain data source information  140  as shown in  FIG. 5F . In another example, the back limit may be established in front of the aircraft current position. In another example, the lateral limits may be altered to accommodate a change in direction of a projected flight path as shown in  FIGS. 5G and 5H . In another example, the lateral limits may be dynamic to accommodate turning flight; for instance,  FIG. 5A  could take the shape of  FIG. 51 ,  FIG. 5C  could take the form of  FIG. 5J , and  FIG. 5E  could take the form of  FIG. 5K  during turning flight. Vertical limits of a search volume may include that airspace which is at or above an airspace clearing surface such as the airspace clearance surface  222  depicted in  FIGS. 5D through 5F . 
     FIGS. 6A through 6C  provide exemplary projections of two alert surfaces based upon the two maneuver profiles  204  and  210  of  FIGS. 4B and 4C . In the embodiments of  FIGS. 6A through 6C , airspace  230  and airspace clearance surface  232  coincide as depicted in  FIG. 6A , which is an advantage of this embodiment because an airspace clearance distance  224  (e.g.,  FIG. 4D ) may be omitted from the computation of an airspace clearance surface. In those embodiments where airspace and airspace clearance surface coincide, these terms may be used interchangeably. One exemplary manner to take advantage of this embodiment is to project each alert surface to an equivalent altitude that is offset by the value of the vertical airspace clearance distance  224  while the alert surface remains based upon an input factor altitude  114 . As previously stated, an aircraft operating in level flight in the enroute phase of flight may have an airspace clearance distance  224  of 700 feet. Because an airspace vertical clearance distance  224  is also the value of the offset, the alert surfaces may be projected from the aircraft altitude of 4,000 feet down to an equivalent altitude of 3,300 feet for this exemplary 700 feet vertical airspace clearance distance  224  as shown in  FIGS. 6A through 6C . 
     FIGS. 6B and 6C  provide exemplary depictions of events in which an airspace clearance surface  232  penetrates two alert surfaces as the aircraft approaches airspace  230 , where each event triggers an alert that may be provided to the pilot by a crew alerting system  195 . In an embodiment of  FIG. 6B , a first surface penetration  238  has occurred where the airspace clearance surface  232  has penetrated a first alert surface  234  as the aircraft approaches airspace  230 . Because the first alert surface  234  is associated with a caution alert in this example as discussed above, an AA processor  190  could generate a caution alert signal and provide such signal to a crew alerting system  195  as a result of the penetration. As the aircraft continues to approach airspace  230  as shown in  FIG. 6C , a second surface penetration  240  has occurred where the airspace clearance surface  232  has penetrated a second alert surface  236 . Because the second alert surface  236  is associated with a warning signal as discussed above, an AA processor  190  could generate a warning signal and provide such signal to the crew alerting system  195  as a result of the penetration. It should be noted that the embodiments of  FIGS. 6A through 6C  may be applied for any alert surface and is not limited to the alert surfaces, phase of flight, or flight attitude depicted therein. 
     FIGS. 7A and 7B  provide exemplary maneuver profiles which may serve as the basis for establishing alert surfaces. In  FIGS. 7A and 7B , maneuver profiles  242  and  248  have been defined by incorporating two criteria into each profile: pilot reaction time and a G-Force pull-up maneuver. Additional criteria could include attitude  116  and vertical speed  120 , or a phase of flight and flight attitude parameter based upon aircraft-related data provided by an airport database  130  and attitude  116 . As these additional criteria demonstrate and as embodied herein, input factors  150  could comprise of alternative sources or a combination of other input factors for any profile of which a manufacturer or end-user may define. As shown in  FIGS. 7A and 7B , the maneuver profiles have shifted to the right to accommodate a horizontal distance contributed by the addition of the two criteria. Because the magnitude of the distance of each criterion may be dependent on at least one input factor such as speed  118 , such factor could be provided as an input to the AA processor  190  for the computation and definition of an alert surface. 
   Maneuver profile  242  of  FIG. 7A  includes a pilot reaction time  244  of 3 seconds and a G-force pull-up maneuver  246  of 0.25 g. Maneuver profile  248  of  FIG. 7B  includes a pilot reaction time  250  of 13 seconds and a G-force pull-up maneuver  252  of 0.25 g. It should be noted that the values of 3 and 13 seconds for the pilot reaction times  244  and  250 , 0.25 g for the G-force pull-up maneuvers  246  and  252 , and 10 NM for horizontal distance have been selected for the sole purpose of illustration and do not establish a limit to the embodiments herein. 
     FIGS. 7C through 7E  provide exemplary projections of two alerting surfaces of an aircraft descending through 6,000 feet which could be represented by input factors such as attitude  116  and altitude  114 . As shown, the aircraft is approaching an airspace  254  along its projected flight path. A first alert surface  256  is based upon maneuver profile  248 , and a second alert surface  258  is based upon maneuver profile  242 . As shown in  FIG. 7C , a first alert surface  256  could be associated with a caution-type alert, and a second alert surface  258  could be associated with a warning-type alert. 
     FIGS. 7C through 7E  depict of an airspace clearance surface  260  that may be projected above airspace  254  at an airspace clearance distance  262 .  FIGS. 7D and 7E  provide exemplary depictions of events in which an airspace clearance surface  260  penetrates two alert surfaces as the aircraft approaches airspace  254 , where each event triggers an alert being that may be provided to the pilot by a crew alerting system  195 . In an embodiment of  FIG. 7D , a first surface penetration  264  has occurred where the airspace clearance surface  260  has penetrated a first alert surface  256  as the aircraft approaches airspace  254 . Because the first alert surface  256  is associated with a caution alert in this example as discussed above, an AA processor  190  could generate a caution alert signal and provide such signal to a crew alerting system  195  as a result of the penetration. As the aircraft continues to approach airspace  254  as shown in  FIG. 7E , a second surface penetration  266  has occurred where the airspace clearance surface  260  has penetrated a second alert surface  258 . Because the second alert surface  258  is associated with a warning signal as discussed above, the processor  190  could generate a warning signal and provide such signal to the crew alerting system  195  as a result of the penetration. Although not shown, an airspace clearance surface  260  could have been projected horizontally at the same or a different clearance distance to provide horizontal separation as discussed above. 
     FIG. 8A  provides exemplary maneuver profiles which may serve as the basis for establishing alert surfaces. In  FIG. 8A , maneuver profiles  268  and  272  have been defined by incorporating two criteria into each profile: a constant radius turn and pilot reaction time. As shown in  FIG. 8A , the maneuver profiles have shifted forward to accommodate a horizontal distance contributed by the addition of the two criteria. Because the magnitude of the distance of the criteria may be dependent on at least two input factors such as attitude  116  and speed  118 , such factors could be provided as input factors to the AA processor  190  for the computation and definition of an alert surface. 
   Maneuver profile  268  includes a pilot reaction time  270  of 3 seconds, and maneuver profile  272  includes a pilot reaction time  274  of 13 seconds. In an embodiment, the inclusion of a pilot reaction time and the exclusion of a G-force pull-up maneuver, for instance, could be selected by a manufacturer or an end-user of an airspace awareness and avoidance system  100 . It should be noted that the values of 3 and 13 seconds for the pilot reaction times  270  and  274  have been selected for the sole purpose of illustration and do not establish a limit to the embodiments herein. 
     FIGS. 8B through 8D  provide an exemplary depiction of an aircraft having two alerting surfaces based upon maneuver profiles  268  and  272  and approaching airspace  276  (which is the same airspace that is as shown in  FIG. 2B ) along its projected flight path. A first alert surface  278  is based upon maneuver profile  272 , and a second alert surface  280  is based upon maneuver profile  268 . As shown in  FIG. 8B , a first alert surface  278  could be associated with a caution-type alert, and a second alert surface  280  could be associated with a warning-type alert. 
     FIGS. 8B through 8D  depict an airspace clearance surface  282  that may be projected above airspace  276  at an airspace clearance distance (e.g., items  224  and  262 ). When viewed from above, the airspace clearance surface  282  coincides with airspace  276 . Although not shown, an airspace clearance surface  282  could have been projected horizontally at the same or a different clearance distance to provide horizontal separation as discussed above.  FIGS. 8C and 8D  provide exemplary depictions of events in which an airspace clearance surface  282  penetrates two alert surfaces as the aircraft approaches airspace  276 , where each event triggers an alert that may be provided to the pilot by a crew alerting system  195 . In an embodiment of  FIG. 8C , a first surface penetration  284  has occurred where the airspace clearance surface  282  has penetrated a first alert surface  278  as the aircraft approaches airspace  276 . Because the first alert surface  278  is associated with a caution alert in this example as discussed above, an AA processor  190  could generate a caution alert signal and provide such signal to a crew alerting system  195  as a result of the penetration. As the aircraft continues to approach airspace  276  as shown in  FIG. 8D , a second surface penetration  286  has occurred where the airspace clearance surface  282  has penetrated a second alert surface  280 . Because the second alert surface  280  is associated with a warning signal as discussed above, the processor  190  could generate a warning signal and provide such signal to the crew alerting system  195  as a result of the penetration. 
   It should be noted that the penetration of the first alert surface  278  occurred on the left side of the aircraft before it occurred on the right side. Such an occasion—penetration to one side and not the other—could provide a basis used in an AAWS for providing lateral guidance. 
   It should be noted that the discussion thus far has focused on separate vertical and horizontal profiles. Although the discussion has focused separately on maneuver profiles projected vertically and horizontally, an additional embodiment herein could provide a three-dimensional maneuver profile that may combine or incorporate both horizontal and vertical profiles, either in part or in whole. Because an alerting surface may be based upon a maneuver profile, a three-dimensional alerting surface may be based upon a three-dimensional maneuver profile. 
     FIGS. 9A through 9C  provide exemplary projections of two alerting surfaces of an aircraft operating at 4,000 feet in level flight and 500 knots which could be represented by such input factors as altitude  114 , attitude  116 , and speed  118 . For the sake of comparison and brevity only, the exemplary projections of the airspace alert surfaces previously discussed in  FIGS. 4D through 4F ,  FIGS. 6A through 6C ,  7 C through  7 E, and  FIGS. 8B through 8D , will be used as terrain alert surfaces in  FIGS. 9A through 9C ,  FIGS. 10A through 10C ,  FIGS. 11A through 11C , and  FIGS. 12A through 12C , respectively. As embodied herein, a manufacturer or end-user has the ability to define each and every airspace and terrain alert surface, and may or may not decide to use the same surface for both airspace and terrain applications. It should be noted that the use of the same alert surfaces for the sole purpose of illustrating both airspace and terrain avoidance applications in no way, shape, or form constitutes any limitation to the embodiments herein. 
   As shown in  FIGS. 9A through 9C , the aircraft is approaching a hilly or mountainous terrain  302  of higher altitude along its projected flight path. As embodied herein, only one alerting surface may be sufficient for a generation of an alert signal by an AA processor  190  and for the receiving of such signal by a crew alerting system  195 . A first alert surface  304  is based upon maneuver profile  210  (as was first alert surface  218 ), and a second alert surface  306  is based upon maneuver profile  204  (as was second alert surface  220 ). As shown in  FIG. 9A , a first alert surface  304  could be associated with a caution-type alert, and as discussed above, a caution alert may require immediate crew awareness and subsequent corrective action. Likewise, a second alert surface  306  could be associated with a warning-type alert, and as discussed above, a warning alert may require immediate crew awareness and immediate crew action. 
   Terrain  302  of  FIGS. 9A through 9C  (which may include terrain, obstacles, or both as discussed herein) comprises of a surface representative of the elevation corresponding to the Earth&#39;s surface that could be provided by a terrain data source  140 . In an embodiment herein, terrain data could be provided by a terrain database  142 . In another embodiment, terrain data could be provided by a radar system  144 . In another embodiment, terrain data could be provided by both terrain database  142  and radar system  144 . 
     FIGS. 9A through 9C  provide an exemplary depiction of a terrain clearance surface  308  that may be projected vertically above terrain  302  at a terrain clearance distance  310 . Although not depicted, a terrain clearance surface could also be projected horizontally at a clearance distance to provide horizontal separation. As embodied herein, a terrain clearance distance  310  is optional and does not have to be employed. If not employed, a terrain clearance surface  308  could be considered the same as the terrain surface  302  or coinciding with the terrain surface  302 , and receipt of terrain data could constitute the receipt of data representative of a terrain clearance surface  308 . For example, a manufacturer or end-user could rely only on a maneuver profile(s) profiles that define an alert surface(s) to provide clearance. In another example, a terrain database  142  may include data representative of one or more terrain clearance surfaces, and the data provided could be based upon at least one input factor data  150 . In such an example, a manufacturer or end-user could have terrain clearance surfaces corresponding to specific phases of flight, flight attitudes, or both as discussed below. 
   If employed, however, the value of a terrain clearance distance  310  may not remain constant between take-off and landing. As discussed above in detail in the context of airspace avoidance, the value of terrain clearance distance  310  could depend on the different phases of flight, flight attitudes, or both for terrain avoidance. As discussed herein, terrain clearance distances are illustrations intended solely to provide examples and are in no way intended to be limited to those discussed and presented herein. As embodied herein, an AA processor  190  may determine phase of flight, flight attitude, and terrain clearance distances data using algorithms programmed in executable software code. Those skilled in the art will appreciate the ability and ease with which executable software code may be reprogrammed or modified by a manufacturer or end-user to facilitate specific performance standards without affecting or expanding the scope of the embodiments discussed herein. 
     FIGS. 9B and 9C  provide exemplary depictions of events in which a terrain clearance surface  308  penetrates two alert surfaces as the aircraft approaches terrain  302 , where each event triggers an alert being that may be provided to the pilot by a crew alerting system  195 . In an embodiment of  FIG. 9B , a first surface penetration  312  has occurred where the terrain clearance surface  308  has penetrated a first alert surface  304  as the aircraft approaches terrain  302 . Because the first alert surface  304  is associated with a caution alert in this example as discussed above, an AA processor  190  could generate a caution alert signal and provide such signal to a crew alerting system  195  as a result of the penetration. As the aircraft continues to approach terrain  302  as shown in  FIG. 9C , a second surface penetration  314  has occurred where the terrain clearance surface  308  has penetrated a second alert surface  306 . Because the second alert surface  306  is associated with a warning signal as discussed above, an AA processor  190  could generate a warning signal and provide such signal to the crew alerting system  195  as a result of the penetration. 
   As discussed above, a first alert surface  304  and a second alert surface  306  have been based upon maneuver profiles  210  and  204 , respectively, where each has been based on maneuver profile  202  of a constant angle climb (e.g., six degrees) having a distance of 10 NM. As embodied herein and discussed above, however, the advantages of the embodiments herein may incorporate any profile which may be used or defined as a maneuver profile. A manufacturer or end-user of a TAWS  100  could establish or configure a plurality of maneuver profiles; on the other hand, a manufacturer or end-user of the aircraft may wish to provide a single maneuver profile under all conditions to simplify pilot training. As embodied herein, a maneuver profile may comprise of one or more vertical maneuvers, one or more horizontal maneuvers as discussed below in detail, or it may be a combination of one or more vertical and horizontal maneuvers. 
     FIGS. 10A through 10C  provide exemplary projections of two alert surfaces based upon the two maneuver profiles  204  and  210  of  FIGS. 4B and 4C . In the embodiments of  FIGS. 10A through 10C , terrain  316  and terrain clearance surface  318  coincide as depicted in  FIG. 10A , which is an advantage of this embodiment because a terrain clearance distance  310  (e.g.,  FIG. 9A ) may be omitted from the computation of an airspace clearance surface. In those embodiments where terrain and terrain clearance surface coincide, these terms may be used interchangeably. One exemplary manner to take advantage of this embodiment is to project each alert surface from an equivalent altitude that is offset by the value of a vertical terrain clearance distance  310  while the alert surface remains based upon an input factor of an altitude  114 . As previously stated, an aircraft operating in level flight in the enroute phase of flight may have a vertical terrain clearance distance of 700 feet. Because a vertical terrain clearance distance is also the value of the offset, alert surfaces may be projected from the aircraft altitude of 4,000 feet to an equivalent altitude of 3,300 feet for this exemplary 700 feet vertical terrain clearance distance as shown in  FIGS. 10A through 10C . 
     FIGS. 10B and 10C  provide exemplary depictions of events in which a terrain clearance surface  318  penetrates two alert surfaces as the aircraft approaches terrain  316 , where each event triggers an alert that may be provided to the pilot by a crew alerting system  195 . In an embodiment of  FIG. 10B , a first surface penetration  324  has occurred where the terrain clearance surface  318  has penetrated a first alert surface  320  as the aircraft approaches terrain  316 . Because the first alert surface  320  is associated with a caution alert in this example as discussed above, an AA processor  190  could generate a caution alert signal and provide such signal to a crew alerting system  195  as a result of the penetration. As the aircraft continues to approach terrain  316  as shown in  FIG. 10C , a second surface penetration  326  has occurred where the terrain clearance surface  318  has penetrated a second alert surface  322 . Because the second alert surface  322  is associated with a warning signal as discussed above, an AA processor  190  could generate a warning signal and provide such signal to the crew alerting system  195  as a result of the penetration. It should be noted that the embodiments of  FIGS. 10A through 10C  may be applied for any alert surface and is not limited to the alert surfaces, phase of flight, or flight attitude depicted therein. 
     FIGS. 11A through 11C  provide exemplary projections of two alerting surfaces of an aircraft descending through 6,000 feet which could be represented by input factors such as attitude  116  and altitude  114 . As shown, the aircraft is approaching terrain  328  along its projected flight path. A first alert surface  330  is based upon maneuver profile  248 , and a second alert surface  332  is based upon maneuver profile  242 . As shown in  FIG. 11A , a first alert surface  330  could be associated with a caution-type alert, and a second alert surface  332  could be associated with a warning-type alert. 
     FIGS. 11A through 11C  depict of a terrain clearance surface  334  that may be projected above terrain  328  at a terrain clearance distance  336 .  FIGS. 11B and 11C  provide exemplary depictions of events in which a terrain clearance surface  334  penetrates two alert surfaces as the aircraft approaches terrain  328 , where each event triggers an alert being that may be provided to the pilot by a crew alerting system  195 . In an embodiment of  FIG. 11B , a first surface penetration  338  has occurred where the terrain clearance surface  334  has penetrated a first alert surface  330  as the aircraft approaches terrain  328 . Because the first alert surface  330  is associated with a caution alert in this example as discussed above, an AA processor  190  could generate a caution alert signal and provide such signal to a crew alerting system  195  as a result of the penetration. As the aircraft continues to approach terrain  328  as shown in  FIG. 11C , a second surface penetration  340  has occurred where the terrain clearance surface  334  has penetrated a second alert surface  332 . Because the second alert surface  332  is associated with a warning signal as discussed above, an AA processor  190  could generate a warning signal and provide such signal to the crew alerting system  195  as a result of the penetration. 
     FIGS. 12A through 12C  provide an exemplary depiction of an aircraft having two alerting surfaces based upon maneuver profiles  268  and  272  and approaching terrain  340  along its projected flight path. A first alert surface  342  is based upon maneuver profile  272 , and a second alert surface  344  is based upon maneuver profile  268 . As shown in  FIG. 12A , a first alert surface  342  could be associated with a caution-type alert, and a second alert surface  344  could be associated with a warning-type alert. 
     FIGS. 12A through 12C  depict a terrain clearance surface  346  that may be projected above terrain  340  at a terrain clearance distance (e.g., items  310  and  336 ). When viewed from above, the terrain clearance surface  346  coincides with terrain  340 .  FIGS. 12B and 12C  provide exemplary depictions of events in which a terrain clearance surface  346  penetrates two alert surfaces as the aircraft approaches terrain  340 , where each event triggers an alert that may be provided to the pilot by a crew alerting system  195 . In an embodiment of  FIG. 12B , a first surface penetration  348  has occurred where the terrain clearance surface  346  has penetrated a first alert surface  342  as the aircraft approaches terrain  340 . Because the first alert surface  342  is associated with a caution alert in this example as discussed above, an AA processor  190  could generate a caution alert signal and provide such signal to a crew alerting system  195  as a result of the penetration. As the aircraft continues to approach terrain  340  as shown in  FIG. 12C , a second surface penetration  350  has occurred where the terrain clearance surface  346  has penetrated a second alert surface  344 . Because the second alert surface  344  is associated with a warning signal as discussed above, an AA processor  190  could generate a warning signal and provide such signal to the crew alerting system  195  as a result of the penetration. 
   It should be noted that the discussion thus far for both airspace and terrain avoidance has focused on separate vertical and horizontal profiles. Although the discussion has focused separately on maneuver profiles projected vertically and horizontally, an additional embodiment herein could provide a three-dimensional maneuver profile that may combine or incorporate both horizontal and vertical profiles, either in part or in whole. Because an alerting surface may be based upon a maneuver profile, a three-dimensional alerting surface may be based upon a three-dimensional maneuver profile. 
     FIG. 13  depicts a flowchart  400  of an example of a method for generating an alert signal in an AAWS  100 . The flowchart begins with module  402  with receiving of input factor data. Input factor data could comprise of data representative of at least one input factor. Examples of input factors  150  include, but are not limited to, input from a navigation system  110 , an airport database  130 , an airspace database  135 , and a terrain database  142 . The flowchart continues with module  404  with receiving of aircraft position from a navigation system  110 . The flowchart continues with module  406  with retrieving or receiving airspace data corresponding to the aircraft position from an airspace data source such as an airspace database  135 . 
   The flowchart continues with module  408  with defining an airspace clearance surface. In one embodiment, an airspace clearance surface may be defined by an AA processor  190  as a function of the airspace data and at least one airspace clearance distance criterion. In an embodiment, at least one airspace clearance distance criterion could be programmed to include input factor data. For example, airspace clearance distance criteria could include data representative of phase of flight and flight attitude, and these criteria could be programmed to include input factors  150  of, but not limited to, geographic position  112 , altitude  114 , attitude  116 , speed  118 , vertical speed  120 , and input from an airport database  130 . As a result, an airspace clearance surface could be projected vertically above an airspace surface terrain at a distance of an airspace clearance distance after the application of at least one real-time or static input factor  150  to provide vertical separation. In another embodiment, an airspace clearance surface could also be projected horizontally at a clearance distance to provide horizontal separation. 
   The flowchart continues with module  410  with defining of at least one aircraft airspace alert surface. At least one aircraft airspace alert surface could be defined by an AA processor  190  as a function of at least one criterion that has been programmed to include input factor data. Each aircraft airspace alert surface could be based upon at least one criterion programmed to include input factor data. For example, the aircraft airspace alert surface may include pilot reaction time and G-force maneuver as criteria, and these criteria could be programmed to include an input factor  150  of speed  118  as input factor data. As a result, an aircraft airspace alert surface could be projected in front of the aircraft after the application of at least one real-time input factor  150 . As embodied herein, an aircraft airspace maneuver profile—and associated airspace alert surface—may be a vertical profile, horizontal profile, or a combination of both. 
   The flowchart continues with module  412  with generating an airspace alert signal if the airspace clearance service penetrates the aircraft airspace alert surface. The flowchart continues with module  414  with providing the airspace alert signal to a crew alerting system  160 . In one embodiment, the alert signal could cause a presentation of a caution or warning alert on a display, an aural alert by the aural alert unit, or both. Then, the flowchart proceeds to the end. 
     FIG. 14  depicts a flowchart  500  of an example of a second method for generating an alert signal in an AAWS. The flowchart begins with module  502  with receiving of input factor data. Input factor data could comprise of data representative of at least one input factor. As embodied herein, input factors  150  could be provided by any aircraft system, sensor, or database including, but not limited to, a navigation system  110 , and airport-related database  130 , and airspace database  135 . The flowchart continues with module  504  with receiving of aircraft position from a navigation system  110 . The flowchart continues with module  506  with retrieving or receiving airspace data corresponding to the aircraft position from an airspace data source such as an airspace database  135 . The airspace data could be representative of an airspace clearance surface. 
   The flowchart continues with module  508  with defining of at least one aircraft airspace alert surface. At least one aircraft airspace alert surface could be defined by an AA processor  190  as a function of at least one criterion that has been programmed to include input factor data and at least one airspace clearance distance criteria. Each aircraft airspace alert surface could be based upon at least one criterion programmed to include input factor data. For example, the aircraft airspace alert surface may include pilot reaction time and G-force maneuver as criteria, and these criteria could be programmed to include an input factor  150  of speed  118  as input factor data. As a result, an aircraft airspace alert surface could be projected in front of the aircraft after the application of at least one input, factor  150 . As embodied herein, an aircraft airspace maneuver profile—and associated airspace alert surface—may be a vertical profile, horizontal profile, or a combination of both. 
   At least one airspace clearance distance criterion, for example, could include data representative of phase of flight and flight attitude, and these criteria could be programmed to include input factors  150  of, but not limited to, geographic position  112 , altitude  114 , attitude  116 , speed  118 , vertical speed  120 , and input from an airport database  130 . Such criterion could be included in the function or by adding it as a second function. As a result, an airspace alert surface could be projected below the altitude of the aircraft at a distance of the airspace clearance distance after the application of the input factors  150 . 
   The flowchart continues with module  510  with generating an airspace alert signal if the airspace clearance service penetrates the aircraft airspace alert surface. The flowchart continues with module  512  with providing the airspace alert signal to a crew alerting system  160 . In one embodiment, the alert signal could cause a presentation of a caution or warning alert on a display, an aural alert by the aural alert unit, or both. Then, the flowchart proceeds to the end. 
   It should be noted that the method steps described above are embodied in computer-readable media as computer instruction code. It shall be appreciated to those skilled in the art that not all method steps must be performed, nor must they be performed in the order stated. As embodied herein, the actions that could be performed by an AA processor  190  are includes as method steps. 
   As used herein, the term “embodiment” means an embodiment that serves to illustrate by way of example but not limitation. 
   It will be appreciated to those skilled in the art that the preceding examples and embodiments are exemplary and not limiting to the scope of the present invention. It is intended that all permutations, enhancements, equivalents, and improvements thereto that are apparent to those skilled in the art upon a reading of the specification and a study of the drawings are included within the true spirit and scope of the present invention. It is therefore intended that the following appended claims include all such modifications, permutations and equivalents as fall within the true spirit and scope of the present invention.