Abstract:
A computer generated pilot instruction system for providing spatial information to a pilot corresponding to the difference between the actual landing fight path and optimal landing flight path.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Not Applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     Not Applicable. 
     FIELD OF THE INVENTION 
     The present invention relates generally to radar systems, and more particularly, to radar systems for aircraft. 
     BACKGROUND OF THE INVENTION 
     The use of radar for guiding aircraft to land and take off is well known in the art. A radar transmits signals and processes the signal returns to ascertain the heading and altitude of an aircraft approaching an airport. The radar information is used to maintain the aircraft at or near an optimal flight path for landing the aircraft. The level of reliance on radar can vary based upon the weather conditions. In cases where visibility is severely limited, a pilot can rely very heavily on radar information to land the aircraft. 
     In one type of landing system, known as Precision Approach Radar (PAR), a radar operator verbally guides the pilot along a landing course line and a landing glide slope, collectively called the landing flight path, based upon radar data. The PAR system presents the radar operator with a pair of two-dimensional displays. One display provides an aircraft course line in an azimuth display, and the other display provides an aircraft glide slope in an elevation display. The aircraft azimuth and elevation are plotted against range from the airport. On the two display formats, radar returns corresponding to the actual landing flight path of the aircraft are overlaid with lines depicting the optimal landing flight path of an aircraft at a particular runway. The optimal landing flight path may be different at different airports, or at the various runways at a particular airport, or from time to time depending upon weather conditions, or for different types of aircraft. 
     The PAR system operator evaluates the aircraft&#39;s position versus the optimal landing flight path using the azimuth and elevation radar displays and verbally informs the pilot via radio about the current position and trend of the aircraft relative to the optimal landing flight path. The verbal instructions typically include predefined terms, e.g., well above glide slope, slightly right of course line, on course, etc., to indicate the relative position of the aircraft. The pilot then adjusts engine speed and control surfaces, e.g., rudders, to conform to the optimal landing flight path based upon the radar operator&#39;s instructions. 
     While standardized terminology can be used, the meaning of the terms of the verbal flight instructions are imprecise and can vary from operator to operator. In addition, a given operator may subjectively vary the instructions over the landing process. For example, a PAR operator generally pays closer attention as the aircraft moves closer to the airport so as to provide finer control as the aircraft nears touchdown. 
     In addition, an operator&#39;s choice of radar display scale can also affect operator judgment. For example, a zoomed out display is typically used to provide initial guidance of an aircraft while far from the airport. In contrast, a zoomed in display, often used for aircraft close to the airport, is needed to provide fine resolution and fine flight path correction. It is relatively difficult for an operator to use the PAR terminology consistently for multiple zoom levels. 
     Another disadvantage associated with known PAR systems results from unprocessed radar measurements relative to the position of the radar. For safety reasons, the radar antenna is located at a predetermined distance from the touchdown point of the runway, often nearly a mile back from the touchdown point. For such an offset radar, the angular change indicated by the unprocessed radar data for an airplane exactly on a straight landing flight path is relatively large as the aircraft approaches touchdown. Where the optimal landing flight path is straight, unprocessed raw radar data indicates the optimal landing flight path as curved downward. Thus, to provide a more intuitive straight landing flight path display, the raw radar data is processed through coordinate transformations that have the effect of converting to Cartesian coordinates and re-positioning the coordinate origin at the touchdown point, thus making the optimal landing flight path appear straight on the radar displays. 
     Several factors degrade the radar accuracy for displayed points near the touchdown point. As described, the radar transmitter is physically offset from the touchdown point for safety reasons. The offset is both in the x direction, along the runway axis, and along the y direction, along an axis perpendicular to the runway. Because the radar transmitter is physically offset from the touchdown point, as the aircraft approaches the touchdown point the elevation angular accuracy, due to x axis offset, and the scan angle accuracy, due to y axis offset, both become increasingly dominant in the determination of the actual flight path of the aircraft. One of ordinary skill in the art will recognize that the elevation angular accuracy of a typical PAR radar system is about a tenth of a degree. A tenth of a degree elevation error results in a substantial percentage error in the reporting of the detected elevation of the aircraft as it approaches the touchdown point. One of ordinary skill in the art will also recognize that the radar scan angle width increases as the aircraft altitude decreases causing a reduction in the resolution of the radar near the touchdown point. Deviations from the flight path near the displayed touchdown point are scaled to less than a pixel on the display. Deviations of only a few pixels on a moving target can be difficult to detect by the radar operator. 
     Operator provided instructions have an inherent latency due to the time that is required for the operator to interpret the displayed radar information and make a decision as to what information should be given to the pilot. Such latency can cause the pilot to overcompensate or oscillate about the optimal flight path. Additionally, even with standard informational phrases, the transformation from the radar display to the verbal phrase is subjective, and thus, variable operator to operator. 
     Further, the radar operator is in a high stress environment. The operator must attempt to issue verbal information to the aircraft pilot at intervals of approximately 5 seconds as the aircraft approached landing. Under this stressful environment, inaccurate information may be issued by the operator. 
     It would, therefore, be desirable to provide a PAR landing system that presents standardized and consistent spatial information to a pilot during a landing approach. 
     SUMMARY OF THE INVENTION 
     The present invention provides computer generated pilot instructions during the landing process. With this particular arrangement, pilots receive objective landing instructions that eliminate operator inconsistencies and human limitations. While the invention is primarily shown and described in conjunction with landing aircraft, it is understood that the invention is generally applicable to systems in which it is desirable to provide computer generated information based upon the path of a moving object in relation to a desired path. 
     In one aspect of the invention, a method for automatically providing instructions to a pilot for landing an aircraft includes determining spatial information at a radar station that corresponds to a spatial difference between an actual landing flight path of the aircraft and an optimal landing flight path. The method further includes converting the spatial information to flight instructions and conveying the flight instructions to the pilot for enabling the pilot to correct the actual landing flight path to the optimal landing flight path. 
     The flight instructions to the pilot can be generated as synthesized voice flight instructions that correspond to the spatial information. The synthesized voice flight instructions are conveyed to the pilot to facilitate landing of the aircraft. The use of synthesized voice flight instructions provides spatial information to the pilot that is more consistent and more accurate than conventional voice information from a PAR radar operator. 
     In a further aspect of the invention, an apparatus for automatically generating pilot landing instructions includes means for computing a spatial difference between an actual landing flight path of the aircraft and an optimal landing flight path. The apparatus also includes means for converting the spatial information to flight instructions and conveying the flight instructions to the pilot for enabling the pilot to correct the actual landing flight path to the optimal landing flight path. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
     FIG. 1A is a schematic depiction of an exemplary computer generated pilot instruction (CGPI) system in accordance with the invention showing an aircraft landing approach from a side or elevation view; 
     FIG. 1B is a schematic depiction of an CGPI system in accordance with the invention showing a landing approach from a top or azimuth view; 
     FIG. 2A is a block diagram showing further details of an exemplary CGPI system in accordance with the invention; 
     FIG. 2B is a block diagram of an exemplary CGPI instruction generator in accordance with this invention; 
     FIG. 3 is a schematic depiction of the CGPI system showing an exemplary location of a radar of the CGPI system in accordance with this invention; 
     FIG. 4A depicts an exemplary radar display of an aircraft relative to an optimal landing glide slope in accordance with this invention; 
     FIG. 4B depicts an exemplary radar display of an aircraft relative to an optimal landing course heading in accordance with this invention; 
     FIG. 5A is a graphical depiction of elevation ranges in relation to the landing glide slope in accordance with this invention; 
     FIG. 5B is a graphical depiction of azimuth ranges in relation to the landing course line in accordance with this invention; 
     FIG. 6 is a flow diagram showing an exemplary sequence of steps for elevation classification sub-type message generation in accordance with this invention; 
     FIG. 7 is a flow diagram showing an exemplary sequence of steps for elevation rate classification sub-type message generation in accordance with this invention; 
     FIG. 8 is a flow diagram showing an exemplary sequence of steps for azimuth classification sub-type message generation in accordance with this invention; and 
     FIG. 9 is a flow diagram showing an exemplary sequence of steps for azimuth rate classification sub-type message generation in accordance with this invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As used herein, the term instruction refers to information provided to a pilot indicating the position of an aircraft in relation to an optimal flight path. Also as used herein, the optimal landing glide slope refers to the optimal elevation for an approaching aircraft, and the optimal landing course heading refers to the optimal azimuth. The term optimal landing flight path refers collectively to both optimal landing glide slope and optimal landing course heading. 
     FIG. 1A shows an exemplary computer generated pilot instruction (CGPI) system  5  in accordance with the invention illustrating an aircraft  34  landing approach from a side or elevation view. The aircraft  34  pilot is guided by the CGPI system  5  toward the optimal landing glide slope  24  via automatically generated synthesized voice flight instructions so that the aircraft will touchdown on a runway  32  at an optimal landing point  30 . It should be noted that the several aircraft  34  are the same aircraft shown at different times in the landing approach. The outer landing glide path boundaries  26 ,  28  define the outer acceptable limits of a safe landing approach in elevation. 
     A CGPI radar  10  with a radar antenna  12  tracks the aircraft  34  position and sends raw radar data  13  to the control tower  14 . The control tower  14  receives the raw data  13  and processes the raw data  13  with a PAR flight processor  20  for communication to a display system  18 . A CGPI module  16  receives processed data via a data bus  15  connected to the PAR flight processor  20  and produces synthesized voice flight instructions for communication to the aircraft  34  with a radio antenna  22 . The display systems  18  also receive processed data from the data bus  15  from the PAR flight processor  20  and can provide both PAR landing displays and text messages related to the synthesized voice flight instructions of the CGPI module  16 . 
     FIG. 1B shows a CGPI system  5  in accordance with this invention, showing a landing approach from a top or azimuth view. Aircraft  34  is guided by the CGPI system  5  toward the optimal landing course heading  36  so that it will touchdown on the runway  32  at the optimal landing point  30 . Again, it should be noted that the several aircraft  34  are the same aircraft at different times in the landing approach. The outer landing azimuth boundaries  38 ,  40  define the outer acceptable limits of a safe landing approach in azimuth. 
     FIG. 2A is a block diagram of an exemplary CGPI system  5  in accordance with the invention. The CGPI system  5  includes a radar  10  with a radar antenna  12  that provides raw aircraft azimuth and elevation information  13  to a PAR flight processor  20 . The radar  10  scans a coverage volume and produces raw measurements  13  of aircraft position in a manner well known to one of ordinary skill in the art. In an exemplary embodiment, the PAR flight processor  20  includes a track processor  100  for comparing the latest aircraft position data to data from previous scans to estimate the aircraft  34  position and velocity. The track processor  100  processes raw data  13  and provides data  110  to a display processor  112  that converts the aircraft position to Cartesian coordinates, for example, for display in elevation and azimuth. 
     Because the radar transmitter  10  and radar antenna  12  are offset from the aircraft touchdown point, the display processor  112  also performs transformations that place the displayed coordinate system origin at the optimal touchdown point  30 , corresponding to the optimal point at which the aircraft would touch the runway upon landing. The transformed origin provides a graphical display that is more easily interpreted than that which would be provided by the raw radar positional data. Transforming a radar origin for display is well known to one of ordinary skill in the art. 
     The output of the display processor  112  provides data  113 , via a data bus  15 , to one or more graphical displays  118   a -N. The graphical displays  118   a -N present both azimuth and elevation displays to the radar operator as described below. Displays  118   a -N can also provide automatically generated pilot instructions, which are described in detail below, on a display screen. The radar operator can modify the display range and resolution through an exemplary I/O device  120   a -N, such as a keyboard. The I/O devices  120   a -N can communicate back to the control panel processor  114  to alter the processing of the display processor  112  and thus make changes to the graphical display  118   a -N. 
     The CGPI generator  122 , within the CGPI module  16 , receives transformed data  119  from data bus  15 , interprets the data, and generates synthesized voice flight instructions  123  based upon an aircraft&#39;s position in relation to the optimal flight path. The synthesized voice flight instructions  123  are provided to a switch  124 , which is under the control of the radar system operator via I/O devices  120   a -N. In operation, the switch  124  is closed to connect the synthesized voice flight instructions  123  to a radio transmitter  126 . 
     In one embodiment, upon radar operator command selection from the I/O device  120   a -N, the radio transmitter  126  can instead be provided voice instructions  131  from microphone  130  to allow the radar system operator to suspend the transmission of synthesized voice flight instructions  123  and replace it with operator voice instructions  131 . 
     The selected transmissions, either synthesized voice flight instruction  123 , or voice instructions  131 , are sent via radio transmitter  126  and radio antenna  22  to the aircraft  34  that contains an aircraft equipment module  132 . The aircraft equipment module  132  includes a receiving antenna  134 , a radio receiver  136  and an audio communication device  138  for audio communication to the pilot. 
     The synthesized voice flight instructions  1 . 23  can include a predetermined set of standardized phrases. In one embodiment, the synthesized voice flight instructions  123  include four classification groups or tags, each with seven sub-classifications, or classification sub-types. The sub-classifications correspond to the flight instructions issued to the aircraft. With this invention, synthesized voice flight instruction sub-classifications can be issued automatically by the CGPI instruction generator  122 . The exemplary classifications and sub-classifications of synthesized voice instructions, each corresponding to an aircraft positional error or rate range, are given in Tables 1 though 4 below. 
     
       
         
               
             
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Elevation Classification 
               
             
          
           
               
                   
                   
                 Elevation Sub- 
               
               
                   
                 Elevation Error 
                 Classifications 
               
               
                   
                 Lower Range 
                 (synthesized voice 
               
               
                   
                 Limit 
                 instructions) 
               
               
                   
                   
               
               
                   
                 WA 
                 well above glide slope 
               
               
                   
                 A 
                 above glide slope 
               
               
                   
                 SA 
                 slightly above glide slope 
               
               
                   
                 OS 
                 on glide slope 
               
               
                   
                 SB 
                 slightly below glide slope 
               
               
                   
                 B 
                 below glide slope 
               
               
                   
                 WB 
                 well below glide slope 
               
               
                   
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Elevation Rate Classification 
               
             
          
           
               
                 Elevation 
                   
                   
                 Elevation Rate Sub- 
               
               
                 Correction Rate 
                   
                   
                 Classifications 
               
               
                 Lower Range 
                 Elevation 
                   
                 (synthesized voice 
               
               
                 Limit 
                 Position 
                 Elevation Correction 
                 instructions) 
               
               
                   
               
               
                 CQ 
                 above (below) 
                 quickly descending (ascending) 
                 correcting quickly 
               
               
                 C 
                 above (below) 
                 descending (ascending) 
                 correcting 
               
               
                 CS 
                 above (below) 
                 slowly descending (ascending) 
                 correcting slowly 
               
               
                 H 
                 on 
                 near zero 
                 holding 
               
               
                 DS 
                 above (below) 
                 slowly ascending (descending) 
                 diverging slowly 
               
               
                 D 
                 above (below) 
                 ascending (descending) 
                 diverging 
               
               
                 DQ 
                 above (below) 
                 quickly ascending (descending) 
                 diverging quickly 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Azimuth Classification 
               
             
          
           
               
                   
                   
                 Azimuth Sub- 
               
               
                   
                 Azimuth Error 
                 Classifications 
               
               
                   
                 Lower Range 
                 (synthesized voice 
               
               
                   
                 Limit 
                 instructions) 
               
               
                   
                   
               
               
                   
                 WL 
                 well left of course line 
               
               
                   
                 L 
                 left of course line 
               
               
                   
                 SL 
                 slightly left of course line 
               
               
                   
                 OC 
                 on course line 
               
               
                   
                 SR 
                 slightly right of course line 
               
               
                   
                 R 
                 right of course line 
               
               
                   
                 WR 
                 well right of course line 
               
               
                   
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 Azimuth Rate Classification 
               
             
          
           
               
                 Azimuth 
                   
                   
                   
               
               
                 Correction Rate 
                   
                   
                   
               
               
                 Lower Range 
                 Azimuth 
                 Azimuth Correction 
                 Azimuth Rate Sub- 
               
               
                 Limit 
                 Position 
                 Rate 
                 Classifications 
               
               
                   
               
               
                 CQ 
                 left (right) 
                 quickly to right (left) 
                 correcting quickly 
               
               
                 C 
                 left (right) 
                 to right (left) 
                 correcting 
               
               
                 CS 
                 left (right) 
                 slowly to right (left) 
                 correcting slowly 
               
               
                 H 
                 on 
                 near zero 
                 holding 
               
               
                 DS 
                 left (right) 
                 slowly to left (right) 
                 diverging slowly 
               
               
                 D 
                 left (right) 
                 to left (right) 
                 diverging 
               
               
                 DQ 
                 left (right) 
                 quickly to left (right) 
                 diverging quickly 
               
               
                   
               
             
          
         
       
     
     It will be recognized by one skilled in that the art that the flight instructions are not limited to those sub-classifications given in Tables 1 though 4. Any synthesized voice flight instructions contained in any number of messages are within the scope of this invention. In addition, in an exemplary embodiment, the language of the instructions can be selected by the user via the I/O devices  120   a -N. 
     The range categories associated with sub-classifications in the above tables correspond to an amount of error from the optimal flight path. As will be described below, the particular synthesized voice flight instructions chosen to be sent to the aircraft are based upon the amount of flight path error. Let it suffice to say here that the CGPI instruction generator  122  automatically selects a grouping of the above sub-classifications to communicate to the aircraft by synthesized voice. The instructions are generated based upon the positional error of an approaching aircraft in relation to the optimum flight path, as are more fully described below. 
     The exemplary CGPI system uses groupings of flight instructions, each with two sub-classifications. For example, an exemplary synthesized voice flight instruction grouping is “well left of course line, diverging slowly.” Typically two such groupings can be transmitted sequentially where one grouping corresponds to the sub-classifications of Tables 1 and 2 and the other corresponds to Tables 3 and 4. One of ordinary skill in the art will recognize that other groupings are within the scope of this invention. 
     In conventional PAR systems, the radar operator communicates voice messages to the aircraft at a rate that can vary over time and by operator. The radar operator subjectively determines and modifies the flight instructions based upon aircraft type. 
     In contrast, the CGPI system of the present invention generates synthesized voice flight instructions that can be communicated to the pilot at a consistent rate, e.g., five seconds. However, one skilled in the art will recognize that other instruction rates, fixed and variable, are within the scope of this invention. The CGPI system can provide messages at a consistent rate and/or a rate that consistently varies by aircraft position along the landing flight path. In addition, the CGPI system can automatically provide landing flight instructions appropriate for the type of aircraft, upon identification of the aircraft type by the radar system operator to the CGPI system using I/O devices  120   a -N. 
     It will be recognized by one skilled in the art that the synthesized voice flight instructions  123  may be in any encoded form for transmission via the radio transmitter  126  and the radio antenna  22 . If the synthesized voice flight instructions  123  are encoded, then the aircraft radio receiver  136  can provide a decoding function such that the synthesized voice flight instructions are presented to the pilot in decoded voice form by the audio device  138  in the aircraft. 
     FIG. 2B is a block diagram of an exemplary CGPI instruction generator  122  in accordance with this invention. The exemplary CGPI instruction generator  122  includes a classification processor  143  that contains an elevation processor  143   a , an elevation rate processor  143   b , an azimuth processor  143   c , and an azimuth rate processor  143   d  for arranging the aircraft positional or rate ranges into four classifications each with seven sub-classifications as indicated in Tables 1-4 above. It will be recognized by one skilled in the art that other arrangements of classifications and sub-classifications of aircraft positional and rate ranges are possible with this invention. 
     A range processor  145  establishes positional and rate ranges  145   a-d  associated with each of the sub-classifications. The ranges correspond to ranges of positional error and ranges of rates of closure relative to an optimal landing flight path that can be associated with an actual aircraft position. The positional ranges and rate ranges  145  can be different for different airports, weather conditions, and aircraft. 
     A comparison processor  147  compares that actual position of the aircraft, corresponding to input data  119  from the PAR flight processor ( 20  of FIG.  2 A), to the ranges  145   a-d  established by the range processor  145 . The comparison decisions will be further described in association with FIGS. 6-9. The comparison processor  147  provides four individual outputs  149   a-d , one for each of the classification types  143   a-d . An elevation range  149   a , an elevation rate range  149   b , an azimuth range  149   c , and an azimuth rate range  149   d  indicate the sub-classification ranges within each of the four classifications  143   a-d  that best describe the actual position of the aircraft relative to an optimal landing flight path. Each of the four sub-classification ranges  149   a-d  are provided to the instruction generator  151  that provides synthesized voice flight instructions  123  corresponding to the four sub-classification ranges  149   a-d.    
     FIG. 3 is a schematic depiction of the CGPI system  5  showing an exemplary location of a radar  10  and radar antenna  12 . The radar  10  and radar antenna  12  are located at a position offset in two dimensions from the optimal touchdown point  30  on the runway  32 . Offset in the y direction  150  and offset in the x direction  148  are corrected with data transformation by the PAR flight processor  20  located in the control tower  14 . As described above, coordinate transformations allow the CGPI system radar display as shown in subsequent figures to use display axes on which the optimal touchdown point  30  is the origin of the axes. Using the touchdown point as the origin, rather than the position of the radar  10  and radar antenna  12 , provides a display that is easier to interpret by the radar system operator. 
     FIG. 4A depicts an elevation (EL) radar display of an aircraft track symbol  50   a  relative to an optimal landing glide slope  24 . The track symbol  50   a  can correspond to the aircraft  34  of FIGS. 1A-B. In one embodiment, the displayed optimal glide slope  24  can be adjusted manually by the operator or automatically adjusted based upon weather conditions, hazards, type of aircraft, or airport. Note that the optimal landing glide slope  24  is indicated as a straight line for user friendly viewing by the operator. The outer landing glide path boundaries  26 ,  28  define the outer acceptable limits of a safe landing approach in elevation. An aircraft landing flight path elevation error angle  156  is also shown. 
     Flight instruction label  152  corresponding to the elevation and elevation rate sub-classifications of Tables 1 and 2 and to the synthesized voice flight instructions  123  of FIG. 2A can be provided on the radar displays  118   a -N as text attached to the conventional aircraft track symbol  50   a . Alternatively, arrows or other ornaments can be added to the track symbol, and/or the track symbol can be color coded in correspondence to the synthesized voice flight instructions  123 . It will be recognized by one skilled in the art that there are many forms by which the elevation and elevation rate synthesized voice flight instructions can be presented on the radar display. 
     FIG. 4B depicts an azimuth (AZ) display of an aircraft with track symbol  50   b  relative to an optimal landing course heading  36 . The optimal landing course heading  36  may be different at the various airports or it may be different from time to time based upon weather conditions. The outer landing azimuth boundaries  38 ,  40  define the outer acceptable limits of a safe landing approach in azimuth. An aircraft landing flight path azimuth error angle  158  is also shown. 
     Flight instruction label  154  corresponding to the azimuth and azimuth rate sub-classifications of Tables 3 and 4 and to the synthesized voice flight instructions  123  of FIG. 2A can be provided on the radar displays  118   a -N as text attached to the aircraft track symbol  50   b . As above, it will be recognized by one skilled in the art that there are many forms by which the azimuth and azimuth rate synthesized voice flight instructions can be presented on the radar display. 
     FIG. 5A depicts exemplary elevation ranges  191  and elevation rate ranges  167  in relation to the optimal landing glide slope  24  of aircraft track symbol  50   a . Ranges  184 - 190  correspond to ranges of Table 1 and ranges  160 - 166  correspond to those of Table 2. In an exemplary system, the elevation “above” ranges  184 - 186  are symmetrical with the “below” ranges  188 - 190  about the “on slope” (OS) range  187 . Also in the exemplary system, the elevation rate “converging” ranges  164 - 166  are symmetrical with the “diverging” ranges  160 - 162  about the “holding” (H) range  163 . In should be recognized by one of ordinary skill in the art that any elevation and elevation rate ranges, whether symmetrical or not, are possible with the present invention. It should further be recognized by one of ordinary skill in the art that these elevation ranges can be presented on the radar display. 
     For example, the aircraft track symbol  50   a  is depicted at an elevation above range A  185 . If it is on a heading corresponding to direction (rate) H  163 , the synthesized voice flight instruction for elevation and elevation rate will be “above, holding.” 
     FIG. 5B depicts exemplary azimuth ranges  199  and azimuth rate ranges  183  in relation to the optimal landing course line  36  of aircraft track symbol  50   b . Azimuth ranges  199  correspond to ranges of Table 3 and azimuth rate ranges  183  correspond to those of Table 4. In an exemplary system, the azimuth “right” ranges  192 - 194  are symmetrical with the “left” ranges  196 - 198  about the “on course” (OC) range  195 . Also in the exemplary system, the azimuth rate “converging” ranges  172 - 174  are symmetrical with the “diverging” ranges  168 - 170  about the “holding” (H) range  171 . In should be recognized that any azimuth and azimuth rate ranges, whether symmetrical or not, are possible with the present invention. It should further be recognized that these azimuth ranges can be presented on the radar display. 
     For example, the aircraft track symbol  50   b  is depicted at an azimuth position beyond range SR  194 . If it is on a heading corresponding to direction (rate) DS  170 , the synthesized voice flight instruction for azimuth and azimuth rate will be “slightly right, diverging slowly.” 
     FIG. 6, in combination with FIG. 5A shows an exemplary sequence of steps for providing elevation computer generated pilot instructions in accordance with the present invention. In step  200 , the elevation angular error is computed from the radar returns as the aircraft elevation minus the optimal landing path elevation  24 . A positive elevation error corresponds to an aircraft elevation that is above the optimal landing glide slope  24 . In step  202  it is determined whether the aircraft&#39;s elevation error is greater than WA degrees above the optimal glide slope  24 . In the case where the WA relative elevation is exceeded, the flight instruction generator  122  generates a “well above glide slope” message in step  220  that is transmitted to the pilot. The flight instruction generator  122  makes a series of similar range decisions in steps  202 - 212 . Where the aircraft elevation error  200  crosses a range  202 - 212 , the flight instruction generator synthesizes a corresponding voice phrase in steps  220 - 232 . The voice phrases correspond to the conventional sub-classifications of Table 1. Exemplary elevation lower range limits are shown in Tables 5. 
     
       
         
               
             
               
               
               
             
           
               
                 TABLE 5 
               
             
             
               
                   
               
               
                 Exemplary Elevation Classification Limits 
               
             
          
           
               
                   
                 Elevation Sub- 
                 Elevation Error 
               
               
                   
                 Classification 
                 Lower Range Limit 
               
               
                   
                   
               
               
                   
                 Well Above Glide Slope 
                 WA = 0.25 degrees 
               
               
                   
                 Above Glide Slope 
                 A = 0.15 degrees 
               
               
                   
                 Slightly Above Glide Slope 
                 SA = 0.05 degrees 
               
               
                   
                 On Glide Slope 
                 OS = −0.05 degrees 
               
               
                   
                 Slightly Below Glide Slope 
                 SB = −0.15 degrees 
               
               
                   
                 Below Glide Slope 
                 B = −0.25 degrees 
               
               
                   
                 Well Below Glide Slope 
                 WB = No lower limit 
               
               
                   
                   
               
             
          
         
       
     
     FIG. 7, in combination with FIG. 5A shows an exemplary sequence of steps for providing elevation rate computer generated pilot instructions in accordance with the present invention. In step  300 , the elevation angular rate is computed with the optimal touchdown point  30  as the origin. In step  301 , the current elevation error is examined. As mentioned above, a positive elevation error corresponds to an aircraft elevation that is above the optimal landing glide slope  24 . A positive elevation rate corresponds to increasing elevation. If the aircraft is above the optimal landing glide slope  24 , a negative elevation rate indicates a positive elevation correction rate  302   b , and the aircraft is converging on the optimal landing glide slope. If the aircraft is below the optimal landing glide slope  24 , a positive elevation rate indicates a positive elevation correction rate  302   a , and again the aircraft is converging. In step  303  it is determined whether the aircraft&#39;s elevation correction rate is converging at greater than CQ to the optimal landing glide slope  24 . In the case where the CQ rate is exceeded, the flight instruction generator  122  generates a “correcting quickly” message in step  320  that is transmitted to the pilot. The flight instruction generator  122  makes a series of range decisions in steps  303 - 312 . Where the determined aircraft elevation correction rate  300  crosses a range  303 - 312 , the flight instruction generator synthesizes a corresponding voice phrase in steps  320 - 332 . The voice phrases correspond to the conventional sub-classifications of Table 2. Exemplary elevation correction rate lower range limits are shown in Tables 6. 
     
       
         
               
             
               
               
               
             
           
               
                 TABLE 6 
               
             
             
               
                   
               
               
                 Exemplary Elevation Rate Classification Limits 
               
             
          
           
               
                   
                 Elevation Rate Sub- 
                 Elevation Correction 
               
               
                   
                 Classification 
                 Rate Lower Range Limit 
               
               
                   
                   
               
               
                   
                 Correcting Quickly 
                 CQ = 0.05 degrees/sec 
               
               
                   
                 Correcting 
                 C = 0.025 degrees/sec 
               
               
                   
                 Correcting Slowly 
                 CS = 0.01 degrees/sec 
               
               
                   
                 Holding 
                 H = −0.01 degrees/sec 
               
               
                   
                 Diverging Slowly 
                 DS = −0.025 degrees/sec 
               
               
                   
                 Diverging 
                 D = −0.05 degrees/sec 
               
               
                   
                 Diverging Quickly 
                 DQ = No lower limit 
               
               
                   
                   
               
             
          
         
       
     
     Note that the elevation correction rate ranges of Tables 6 indicate angular elevation correction rate ranges with the touchdown point  30  as the origin. However, FIG. 5A indicates angular elevation correction rate ranges  167  with the aircraft  50   a  as the origin for conceptual clarity. 
     FIG. 8, in combination with FIG. 5B shows an exemplary sequence of steps for providing azimuth position computer generated pilot instructions in accordance with the present invention. In step  400 , the azimuth error is computed from the radar returns as the aircraft azimuth position minus the optimal landing path  36 . A positive azimuth error corresponds to the aircraft being to the left of the optimal landing course heading  36 . In step  402  it is determined whether the aircraft&#39;s azimuth error is greater than WL degrees to the left of the optimal glide course heading  36 . In the case where WL degrees is exceeded, the flight instruction generator  122  generates a “well left of course line” message  420  that is transmitted to the pilot. The flight instruction generator  122  makes a series of range decisions in steps  402 - 412 . Where the determined aircraft azimuth error  400  crosses a range  402 - 412 , the flight instruction generator synthesizes a corresponding voice phrase in steps  420 - 432 . The voice phrases correspond to the conventional sub-classifications of Table 3. Exemplary azimuth error lower range limits are shown in Table 7. 
     
       
         
               
             
               
               
               
             
           
               
                 TABLE 7 
               
             
             
               
                   
               
               
                 Exemplary Azimuth Classification Limits 
               
             
          
           
               
                   
                   
                 Azimuth Error 
               
               
                   
                 Azimuth Sub-Classification 
                 Lower Range Limit 
               
               
                   
                   
               
               
                   
                 Well Left of Course Line 
                 WL = 0.25 degrees 
               
               
                   
                 Left of Course Line 
                 L = 0.15 degrees 
               
               
                   
                 Slightly Left of Course Line 
                 SL = 0.05 degrees 
               
               
                   
                 On Course Line 
                 OC = −0.05 degrees 
               
               
                   
                 Slightly Right of Course Line 
                 SR = −0.15 degrees 
               
               
                   
                 Right of Course Line 
                 R = −0.25 degrees 
               
               
                   
                 Well Right of Course Line 
                 WR = No lower limit 
               
               
                   
                   
               
             
          
         
       
     
     FIG. 9, in combination with FIG. 5B shows an exemplary sequence of steps for providing azimuth rate computer generated pilot instructions in accordance with the present invention. In step  500 , the azimuth rate is computed. In step  501 , the current azimuth error is examined. As mentioned above, a positive azimuth error corresponds to the aircraft being to the left of the optimal landing course heading  36 . If the azimuth error is positive, a negative azimuth rate indicates a positive azimuth correction rate  502   b , and the aircraft is converging upon the optimal landing course heading. If the error is negative, a positive azimuth rate indicates a positive azimuth rate of correction  502   a , and again the aircraft is converging. In step  503  it is determined whether the aircraft&#39;s azimuth correction rate is converging at greater than CQ to the optimal landing course line  36 . In the case where the CQ rate is exceeded, the flight instruction generator  122  generates a “correcting quickly” message in step  520  that is transmitted to the pilot. The flight instruction generator  122  makes a series of range decisions in steps  503 - 512 . Where the determined aircraft azimuth correction rate  500  crosses a range  503 - 512 , the flight instruction generator synthesizes a corresponding voice phrase in steps  520 - 532 . The voice phrases correspond to the conventional sub-classifications of Table 4. Exemplary azimuth correction rate lower range limits are shown in Table 8. 
     
       
         
               
             
               
               
               
             
           
               
                 TABLE 8 
               
             
             
               
                   
               
               
                 Exemplary Azimuth Rate Classification Limits 
               
             
          
           
               
                   
                 Azimuth Rate Sub- 
                 Azimuth Correction 
               
               
                   
                 Classification 
                 Rate Lower Range Limit 
               
               
                   
                   
               
               
                   
                 Correcting Quickly 
                 CQ = 0.05 degrees/sec 
               
               
                   
                 Correcting 
                 C = 0.025 degrees/sec 
               
               
                   
                 Correcting Slowly 
                 CS = 0.01 degrees/sec 
               
               
                   
                 Holding 
                 H = −0.01 degrees/sec 
               
               
                   
                 Diverging Slowly 
                 DS = −0.025 degrees/sec 
               
               
                   
                 Diverging 
                 D = −0.05 degrees/sec 
               
               
                   
                 Diverging Quickly 
                 DQ = No lower limit 
               
               
                   
                   
               
             
          
         
       
     
     Note that the azimuth correction rate ranges of Tables 8 indicate azimuth correction rate angular ranges with the touchdown point  30  as the origin. However, FIG. 5B indicates azimuth correction rate angular ranges  183  with the aircraft  50   b  as the origin for conceptual clarity. 
     It will be understood by one of ordinary skill in the art that the instructions provided to the pilot can take a variety of formats including voice, visual and sound signals. For example, the automatically generated instructions can be provided as signals that light various cockpit indicators corresponding to the tags and classifications described above. 
     One skilled in the art will appreciate further features and advantages of the invention based on the above-described embodiments. Accordingly, the invention is not to be limited by what has been particularly shown and described, except as indicated by the appended claims. All publications and references cited herein are expressly incorporated herein by reference in their entirety.