Abstract:
A method and system for a required time of arrival (RTA) performance graphic display is provided. The system includes a processor programmed to receive a required time of arrival and a first visual display communicatively coupled to the processor. The first visual display includes an RTA graphic having a dial substantially symmetric about an axis, a first marker indicative of a current estimated time of arrival (ETA) at a predetermined waypoint, a second marker indicative of a value of the RTA relative to the current ETA value and a selected RTA time tolerance value, a first indication representing a first time the vehicle can attain the predetermined waypoint, a second indication representing a last time the vehicle can attain the predetermined waypoint, a third indication representing the uncertainty of the ETA in an early arrival direction, and a fourth indication representing the uncertainty of the ETA in a late arrival direction.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to vehicle navigation and guidance systems and, more particularly, to a method and systems for displaying a performance of a vehicle for meeting required times of arrival. 
     At least some known vehicles, most notably aircraft, are controlled to arrive a specific positions along a track at corresponding predetermined times. Such required time of arrival control permits increasing the air traffic using common airspace. In current operation, flight crews can monitor Required Time of Arrival (RTA) compliance by looking at numeric displays on the Control Display Unit that is mounted in the center pedestal area. However, numeric displays outside the pilot&#39;s forward field of view are difficult to read and interpret without increased effort by the pilot. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one embodiment, a system for a required time of arrival (RTA) performance graphic display includes a processor programmed to receive predetermined parameters associated with a required time of arrival and a first visual display communicatively coupled to the processor. The first visual display includes an RTA graphic having a dial substantially symmetric about an axis, a first marker indicative of a current estimated time of arrival (ETA) at a predetermined waypoint, a second marker indicative of a value of the RTA relative to the current ETA value and a selected RTA time tolerance value, a first indication representing a first time the vehicle can attain the predetermined waypoint, a second indication representing a last time the vehicle can attain the predetermined waypoint, a third indication representing the uncertainty of the ETA in an early arrival direction, and a fourth indication representing the uncertainty of the ETA in a late arrival direction. 
     In another embodiment, a method of displaying a required time of arrival (RTA) performance includes receiving waypoint information, including waypoint position information, a required time of arrival (RTA) of a vehicle at the waypoint, a tolerance about the RTA, and an estimated time of arrival (ETA) at the waypoint, and graphically displaying the RTA relative to the ETA. 
     In yet another embodiment, a forward field of view display system including a graphic display screen is provided. The graphic display screen includes a plurality of indicating areas, at least one indicating area includes a required time of arrival (RTA) display indicator configured to graphically display a current estimated time of arrival (ETA) at a predetermined waypoint, graphically display a value of the RTA relative to the current ETA value and a selected RTA time tolerance value, and graphically display a first time the vehicle can attain the predetermined waypoint using the fastest current speed limits of the vehicle. The RTA display indicator is further configured to graphically display a last time the vehicle can attain the predetermined waypoint using the slowest current speed limits of the vehicle, and graphically display an uncertainty of the vehicle being able to reach the waypoint within the selected RTA time tolerance value. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1-7  show exemplary embodiments of a method and systems described herein. 
         FIG. 1  is a graphic display in accordance with an exemplary embodiment of the present invention; 
         FIG. 2  is a display of the RTA graphic shown in  FIG. 1  in accordance with an exemplary embodiment of the present invention; 
         FIG. 3  is a display of the RTA graphic shown in  FIG. 1  illustrating the RTA time indicator shown in  FIG. 2  outside of an RTA tolerance; 
         FIG. 4  is a display of the RTA graphic shown in  FIG. 1  illustrating an increased estimated ETA uncertainty; 
         FIG. 5  is a view of a horizontal situation display shown in a map mode in accordance with an exemplary embodiment of the present invention; 
         FIG. 6  is an enlarged expanded view of a portion of the horizontal situation display shown in  FIG. 5  in accordance with an exemplary embodiment of the present invention; and 
         FIG. 7  is a view of the horizontal situation display shown in the map mode indicating an out-of-tolerance condition. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following detailed description illustrates embodiments of the invention by way of example and not by way of limitation. It is contemplated that the invention has general application to analytical and methodical embodiments of determining a performance of a vehicle with respect to an arrival at a predetermined waypoint and to display the performance ergonomically in a convenient field of view of the vehicle operator in industrial, commercial, and residential applications. 
     As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural elements or steps, unless such exclusion is explicitly recited. Furthermore, references to “one embodiment” of the present invention are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. 
     Generally, aircraft are controlled in three dimensions; latitude, longitude and altitude. There has been extensive operational experience in three dimensions as evidenced by advances made in Required Navigation Performance (RNP). Display of navigation performance for flight crews has been developed so that compliance with applicable RNP is readily visible and appropriate alerting is provided when operation is not in compliance with the applicable RNP. 
     Controlling aircraft in the fourth dimension, time, is recently becoming more prevalent. Advances in airspace management show increased capacity for more aircraft when a landing time for each aircraft is specified in advance and each aircraft can control its arrival at waypoints along its track to its assigned time. Economic benefits also result if each aircraft can determine its desired landing time using its most fuel optimum flight profile. By specifying the landing time close to the desired landing time each aircraft saves fuel as well as increasing the capacity to land more aircraft. This method of operation is called Required Time of Arrival (RTA). 
     A method for displaying the time control performance in the forward view uses a “clock” type display containing a graphical view of the important parameters for monitoring RTA compliance during flight. It is compact enough to be placed in the pilot&#39;s primary field of view as a separate instrument. In the modern flight deck, the display can be incorporated as a graphic image on the primary flight display. An along-track “RTA time box” is added to the horizontal situation display when in the map mode. 
       FIG. 1  is a graphic display  100  in accordance with an exemplary embodiment of the present invention. In the exemplary embodiment, display  100  is a primary flight display (PFD) that may be found in a cockpit (not shown) of an aircraft (not shown). Also in the exemplary embodiment, display  100  comprises a display field  102  presented on, for example, a cathode ray tube (CRT) screen, solid state display screen, or other display screen capable of functioning as described herein. Display field  102  is controlled by a display processor (not shown in  FIG. 1 ) to display for example, but not limited to text, graphics, animations, icons, and soft keys. In various embodiments, display  100  comprises a touch-enabled screen. 
     Display field  102  is divided into a plurality of indicators or indicating areas  104 ,  106 ,  108 ,  110  and  112 . A first area  104  comprises a centrally located electronic attitude indicator which is substantially rectangular in shape having a central boresight box  114  representing the airplane longitudinal axis at the center of boresight box  114 . On either side thereof are conventional, stationary aircraft symbols  116  and  118 . An artificial horizon is provided by line  120  between an upper more lightly shaded area  122  representing the sky and a lower darker area  124  for ground shading. In addition, area  124  includes a digital readout  126  of the radio or (radar) altitude, which displays the current height of the aircraft above the ground. 
     Adjacent and along a left hand side of attitude indicator  104  is an air speed indicator  106  comprising a vertically oriented movable scale  128  or “tape” having graduations representing air speed values along the right hand side thereof, i.e., on the side adjacent attitude indicator  104 . Air speed indicator  106  further includes a fixed pointer  130  which points inwardly toward air speed scale  128  as well as toward a center of attitude indicator  104 . Pointer  130  is provided with a window  132  digitally indicating the air speed in response to instrumentation of the aircraft. As the air speed changes, scale  128  moves vertically relative to pointer  130  which continues to point toward boresight box  114 . Scale  128  presents a range of speed values above and below the current. The current value of the selected air speed is numerically displayed at location  133  above the air speed presentation. 
     Heading indicator  108  comprises a raster-shaded area having the shape of a segment of a circle or compass rose which is easily comprehensible by the viewer. Heading indicator  108  is provided with a degree scale along an upper, arc-shaped portion thereof adjacent to the attitude indicator  104 , and like the previously described air speed indicator  106 , a scale  134  of heading indicator  108  moves with respect to a fixed pointer  136 . Below fixed pointer  136 , heading indicator  108  includes a track indicator  138  that moves as the track varies in relation to the heading. To the left of pointer  136  is a location  139  that digitally displays the present heading. 
     Altitude indicator  110  is located adjacent a right hand side of attitude indicator and is provided with an altitude scale  140  along a left hand side thereof adjacent attitude indicator  104 . Altitude indicator  110  is further provided with altitude numerics to the right of appropriate indicia on the scale. Altitude indicator  110  is of the moving scale type wherein scale  140  moves with respect to a fixed pointer  142  as the altitude of the aircraft changes, with the current value of the selected altitude being numerically displayed at location  144  above altitude indicator  110 . Fixed pointer  142  includes an adjacent window  146  within which the correct altitude is digitally displayed in rolling number fashion. Thus, as altitude information from aircraft instrumentation changes, both the numerical indicia in window  146  and the position of the underlying scale  140  change accordingly. A digital readout at position  150  at a lower end of altitude indicator  110  represents the barometric setting in inches of mercury. 
     Display field  102  also includes vertical speed indicator  112  calibrated in thousands of feet per minute along the left hand side thereof adjacent altitude indicator  110 . The shaded area comprising vertical speed indicator  112  is approximately trapezoidal in shape, widening toward altitude indicator  110 , and is provided with a movable pointer  152  adapted to indicate the current vertical speed of the aircraft by pointing to the indicia of the scale along the left hand side of vertical speed indicator  112 . 
     Display field  102  also includes flight mode annunciator readouts  154 ,  156  and  158  at the top center of the display. The three columns are reserved for autothrottle status, lateral mode status and vertical mode status. Flight director, autopilot, and autoland status annunciations are displayed at location  160  immediately above the attitude indicator center. In addition, location  162  includes characteristics of the approach, including station frequency and runway heading (in degrees), Distance Measuring Equipment (DME) readout in nautical miles and the current mode status. 
     Display field  102  further includes a Required Time of Arrival (RTA) graphic  164  positioned in a lower left hand corner of display field  102 . RTA graphic  164  is used for displaying the time control performance of the aircraft in the forward view and uses a “clock” type display as is illustrated in  FIG. 2 . Although a clock-type display is illustrated in this non-limiting example, other linear or arcuate display types are also envisioned. RTA graphic  164  includes a graphical view of the important parameters for monitoring RTA compliance during flight. RTA graphic  164  is only visible on display field  102  when an RTA mode is active and engaged. In the exemplary embodiment, RTA graphic  164  is compact enough to be positioned in the pilot&#39;s primary field of view as a separate instrument. 
       FIG. 2  is a display of RTA graphic  164  in accordance with an exemplary embodiment of the present invention. In the exemplary embodiment, RTA graphic  164  includes an RTA waypoint name display  202  that may be crew entered or uplinked from another system or location. The waypoint corresponds to a position when a required crossing time is specified. An RTA time indicator  204  may be crew entered or uplinked and displays the required crossing time expressed in for example, hours:minutes:seconds GMT on a circumferential scale  205  of graphic  164 . An RTA tolerance  206  at each end of scale  205  corresponds to an allowable plus and minus crossing time tolerance that is considered to be on-time expressed in minutes:seconds. A current ETA display  208  represents a computed estimated time of arrival at RTA waypoint  202 . A first time display  210  represents a computed earliest time of arrival using the fastest allowable speed within aircraft limits. First time display  210  is represented by a bar that extends from RTA tolerance  206  towards current ETA display  208  a distance that changes as aircraft speed limits change. A last time display  212  represents a computed latest time of arrival using the slowest allowable speed within aircraft limits. Last time display  212  is represented by a bar that extends from RTA tolerance  206  towards current ETA display  208  a distance that changes as aircraft speed limits change. An estimated ETA uncertainty  213  represents a computed value of two times the standard deviation of an ETA estimation error yielding a 95% confidence level. Estimated ETA uncertainty  213  is represented on graphic  164  as a bolded band extending circumferentially from approximately RTA tolerance  206  on each side of graphic  164  toward current ETA display  208  a distance equal to the value of estimated ETA uncertainty  213 . A distance to RTA waypoint  214  represents a computed along track distance to reach RTA waypoint  202 . 
     Current ETA display  208  is shown at the top center of the “clock” dial. The scale of the dial shown by a first scale line  216  at a minus 120 degrees from current ETA display  208  and a second scale line  218  at a plus 120 degree position and is determined by the time tolerance allowed for RTA operation. This is equal to RTA tolerance  206  which may be equal to a crew-entered or uplinked RTA tolerance value adjusted for distance to RTA waypoint display  214 . The scale has a maximum value of plus and minus 120 seconds when the distance to go is large and deceases to the plus and minus crew-entered or uplinked RTA tolerance value  206  when the distance becomes small. 
     RTA waypoint name display  202  is shown in the center of RTA graphic  164 . Just below the name, distance to RTA waypoint  214  is displayed. RTA time indicator  204  is shown as a colored “bug”, for example, a filled triangular symbol that rotates around the dial according to its value relative to current ETA display  208  and plus and minus RTA tolerance  206 . The position of RTA time indicator  204  is positioned at the along-track waypoint location in the time domain relative to the fixed dial which represents the aircraft&#39;s predicted time at the top center of the scale. Reading the dial from left to right, the time behind the aircraft is on the left and the time ahead of the aircraft is on the right. As shown in  FIG. 2 , current ETA display  208  is slightly ahead of RTA time indicator  204  indicating that the aircraft is slightly early but well within RTA tolerance  206  at the ends of the scale. 
     Bars  220  and  222  around the dial represent first time display  210  and last time display  212 , respectively that the aircraft can make at RTA waypoint display  202  as determined by the aircraft operating limits. Bars  220  and  222  are only displayed when such time falls within the current ETA display  208  plus or minus RTA tolerance  206 . When it is no longer possible to achieve current ETA display  208  plus or minus RTA tolerance  206  without exceeding the speed limits of the aircraft, bars  220  and  222  are not displayed. 
     During operation, upon entering a value for RTA waypoint  202 , the operator is prompted with RTA time indicator  204  equal to the predicted ETA using the default cost-optimal flight profile. This is the desired time of arrival using minimum cost profile for flight. The operator can change the prompted value by entering a new value that may be assigned by air traffic control. The resulting RTA speed target is provided as the active speed command to the autopilot and displayed on the primary flight display. The target speed may he overridden by any applicable speed restriction. The restricted speed is taken into account when computing the estimated time of arrival. By following the active speed command, the aircraft should achieve the RTA if it is within the aircraft speed limits to do so. 
       FIG. 3  is a display of RTA graphic  164  illustrating RTA time indicator  204  is outside of RTA tolerance  206 . In the exemplary embodiment, the triangular symbol RTA of time indicator  204  is parked just outside the full scale indication on the “late” side of RTA graphic  164 . To alert the operator of this condition, the triangular symbol changes from a filled color symbol to an unfilled symbol and flashes for 10 seconds. A text message area  302  displays LATE if the triangular symbol is parked on the right of the scale and EARLY if the triangular symbol is parked on the left side of the scale. The amount of noncompliance is also shown in text message area  302  in the format hours:minutes:seconds. 
       FIG. 4  is a display of RTA graphic  164  illustrating an increased estimated ETA uncertainty  213 . Current ETA is computed based on current aircraft conditions and the forecasted conditions along the remaining flight path. There are a number of possible errors in the prevailing conditions used to compute ETA that result in some uncertainty. For example the horizontal position uncertainty has an along track component that directly translates into time of arrival uncertainty. Another example is the uncertainty of the forecast wind data ahead of the aircraft. Given the error models for each of the factors that contribute to ETA computation error, it is possible to compute a composite ETA uncertainty. The ETA uncertainty is the total error within which the computed ETA is contained with 95% probability. Typically this is two times the standard deviation of the ETA uncertainty. 
     In the exemplary embodiment, estimated ETA uncertainty  213  is increased relative to RTA tolerance  206 , accordingly the bolded bands representing estimated ETA uncertainty  213  fill in the dial until the arcs bands in the middle, change to a predetermined color and flash for 10 seconds. As shown in  FIG. 4  the bolded bands extend in a substantially continuous arc from the start to the end of scale  205  indicating that it is no longer possible to meet the RTA time constraint within 95% probability due to high ETA uncertainty. 
       FIG. 5  is a view of a horizontal situation display  500  shown in a map mode in accordance with an exemplary embodiment of the present invention. In the exemplary embodiment, a map display  501  of the RTA performance scale is displayed proximate a center of horizontal situation display  500  along a lubber line  504  of an aircraft icon  508 . Map display  501  includes an along-track RTA time box  502  and a current ETA diamond  510  representing current ETA display  208 . The relative positions of RTA time box  502 , aircraft icon  508 , and current ETA diamond  510  and the size of RTA time box  502  represents a graphical indication of the RTA performance of the aircraft in real time. RTA time box  502  and current ETA diamond  510  are only visible when the RTA mode is engaged and active. 
       FIG. 6  is an enlarged expanded view of a portion of a horizontal situation display  500  in accordance with an exemplary embodiment of the present invention. Map display  501  of is shown on horizontal situation display  500  when horizontal situation display  500  is in the map mode. Because the scale of the map is based on the geographic distance selected by the operator, the location, and along-track size of RTA time box  502  is converted to distance by multiplying time by ground speed. A width  600  of RTA time box  502  is fixed on the display. The nose of the aircraft, noted by the upper vertex  602  of aircraft icon  508 , corresponds to current ETA display  208 . At the center of RTA time box  502  is a current ETA diamond  510  that corresponds to a value of RTA time indicator  204 . The center of RTA time box  502  is located at a distance of (current ETA display  208 −RTA time indicator  204 )*Ground Speed ahead of or behind the nose of the aircraft. The position of current ETA diamond  510  represents the desired along-track waypoint location in the time domain relative to the nose of the aircraft which represents the aircraft&#39;s ETA at that location. The difference, RTA−ETA is shown under the header RTA  608  adjacent to RTA time box  502  to indicate a time error  606  in hours:minutes:seconds. 
     RTA tolerance  206  is used to compute a length  610  of RTA time box  502  along the aircraft&#39;s track. Length  610  is determined by multiplying RTA tolerance  206  by ground speed. As long as the nose of the aircraft represented by upper vertex  602  of aircraft icon  508  is within the RTA time box, the aircraft is on time. 
     When RTA time indicator  204  is outside of RTA tolerance  206 , the nose of the aircraft represented by upper vertex  602  of aircraft icon  508  is outside RTA time box  502  and the RTA time error  606  turns an amber color for example, alerting the operator that RTA time indicator  204  is outside of RTA tolerance  206 . An example of a LATE condition would show RTA time box  502  ahead of the aircraft. 
       FIG. 7  is a view of horizontal situation display  500  shown in the map mode indicating an out-of-tolerance condition. In the exemplary embodiment, the nose of the aircraft, represented by vertex  602 , is outside RTA time box  502 , RTA time error  606  and header  608  turn amber alerting the operator that the RTA time is outside of the time tolerance. An example of the LATE condition is shown where RTA time box  502  is ahead of the aircraft represented by aircraft icon  508 . 
     The term processor, as used herein, refers to central processing units, microprocessors, microcontrollers, reduced instruction set circuits (RISC), application specific integrated circuits (ASIC), logic circuits, and any other circuit or processor capable of executing the functions described herein. 
     As used herein, the terms “software” and “firmware” are interchangeable, and include any computer program stored in memory for execution by a processor, including RAM memory, ROM memory, EPROM memory, EEPROM memory, and non-volatile RAM (NVRAM) memory. The above memory types are exemplary only, and are thus not limiting as to the types of memory usable for storage of a computer program. 
     As will be appreciated based on the foregoing specification, the above-described embodiments of the disclosure may be implemented using computer programming or engineering techniques including computer software, firmware, hardware or any combination or subset thereof, wherein the technical effect is providing a vehicle operator a graphic forward field of view display that indicates a performance of the vehicle with respect to an arrival of the vehicle at a predetermined waypoint at a predetermined time. Any such resulting program, having computer-readable code means, may be embodied or provided within one or more computer-readable media, thereby making a computer program product, i.e., an article of manufacture, according to the discussed embodiments of the disclosure. The computer readable media may be, for example, but is not limited to, a fixed (hard) drive, diskette, optical disk, magnetic tape, semiconductor memory such as read-only memory (ROM), and/or any transmitting/receiving medium such as the Internet or other communication network or link. The article of manufacture containing the computer code may be made and/or used by executing the code directly from one medium, by copying the code from one medium to another medium, or by transmitting the code over a network. 
     The above-described embodiments of a method and systems of displaying a required time of arrival (RTA) display for a vehicle provides a cost-effective and reliable means for implementing a software enhancement to existing equipments in modern aircraft such as but not limited to the Flight Management Computer System (FMCS) and Cockpit Display System (CDS). More specifically, the methods and systems described herein facilitate receiving information relating to a vehicle position in time and space with respect to a predetermined waypoint position and a required time of arrival at the waypoint. In addition, the above-described methods and systems facilitate displaying the RTA information to the vehicle operator ergonomically in a forward field of view. As a result, the methods and systems described herein facilitate operating vehicles in a cost-effective and reliable manner. 
     While the disclosure has been described in terms of various specific embodiments, it will be recognized that the disclosure can be practiced with modification within the spirit and scope of the claims.