Abstract:
A performance advisory system which includes a display, a control unit and an onboard computer, the computer receiving inputs from aircraft instruments and gauges and from the control unit and providing advisory output information on the display.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to aircraft control in general and more particularly to an improved system to help pilots of commercial airlines operate their aircraft to obtain maximum performance, particularly in terms of fuel economy. 
     Presently, flight crew must utilize a plurality of charts and tables carrying out complex interpolations in order to get an idea of proper power settings, altitude, rate of climb, etc., in order to determine how to obtain best performance from their aircraft. These tables, of course, require the flight crew gathering data such as aircraft gross weight, altitude, air temperature, true air speed, mach number, etc., all of which is time consuming. As a result, quite often commercial aircraft are not operated at maximum efficiency resulting in the consumption of large amount of fuel which could otherwise be saved. At the present time with the shortage of fuel and its high cost, it is particularly important that all possible steps be taken to economize on fuel consumption. Not only does this contribute to overall energy conservation, but from the standpoint of the operator of the aircraft it can produce substantial savings. 
     Thus, it becomes apparent that there is a need for an improved system for informing the pilot as to the optimum operating conditions. 
     SUMMARY OF THE INVENTION 
     The present invention provides such a system. The basic elements of the system are a dedicated computer, a display unit for displaying information to the pilot and a control unit containing both display and input devices. 
     The control unit permits the pilot to insert information with respect to various aircraft parameters and also to select a mode of operation. This information is provided to the computer system. Additional inputs to the computer are inputs obtained from the aircraft instrument system, such as mach number, air speed, altitude, etc. Based on the mode selected by the pilot and this data the display unit then displays to the pilot information such as optimum altitude, optimum airspeed, maximum altitude, etc. Although directed primarily to economy, the system also permits determining optimum settings for other purposes. For example, in a climb mode information regarding the best rate of climb, best climb angle and settings for intercepting a target altitude at a selected distance can be provided in addition to providing settings for a best fuel economy. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1a illustrates the display of the present invention in the &#34;Upper&#34; mode. 
     FIG. 1b illustrates the display of FIG. 1 in the &#34;Lower&#34; mode. 
     FIG. 2 illustrates the control unit of the present invention. 
     FIGS. 3A-C are tables summarizing various modes of operation. 
     FIG. 4 is a basic block diagram of the system of the present invention. 
     FIG. 5 is a more detailed block diagram of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Prior to explaining in detail the manner in which data is processed to obtain the advisory information, the various functions which the system can perform along with the types of inputs and outputs provided from the system will be discussed. FIGS. 1a and 1b illustrate the display unit 10 in its two modes of operation. The display unit permits the output of eight numerical parameters, four at a time on two scales, an upper and a lower scale. A switch 11 associated with the display panel 10 is used to select between &#34;UPPER&#34; and &#34;LOWER&#34;. FIG. 1a shows the parameters displayed when &#34;UPPER&#34; is selected. On a first display section 13 the Pod Engine Pressure Ratio required is provided. On the adjacent display section 15 the quantity CTR, Center Engine Pressure Ratio Required is displayed. At the display section 17, PAT or Command Pitch Attitude is displayed and finally on the display 19, IAS the Command Indicated Airspeed is displayed. The parameters displayed on the upper scale are commands which, if followed will result in the attainment of the objective for the mode selected. The various modes which can be selected will be described in more detail below in connection with Table 1. 
     On the lower scale is illustrated by FIG. 1b, the display section 13 displays a quantity designated POD LIM which is the POD Engine Pressure Ratio Limit. Similarily the display section 15 displays a quantity designated CTR LIM which is the Center Engine Pressure Ratio Limit. The display section 17 displays OPT ALT or Optimum Altitude, and the Section 19 MAX ALT or Maximum Altitude. The parameters displayed on the lower scale provide information for use in planning and comparison of various alternatives. The display also provides an alphanumeric annuciation of the system mode on a display section 21. This mode is selected by means of the Control Panel to be described below and assures the operator that the computer has actually acquired the selected mode. There is also provided an amber caution indicator designated PLNG (planning). When lighted, this reminds the operator that the numeric values displayed do not represent command settings to be followed at that time. Rather, with the system in PLNG mode, the displays provide information that is used to plan alternate profiles for future phases of the flight. In other words, as will be seen in more detail below not only can the system be used for determining optimum operating conditions for the portion of the flight in progress, but, through insertion of appropriate data can be used for planning future phases of the flight. Also provided on the display 10 is a dimmer control 25 to control the intensity of the display. 
     FIG. 2 illustrates the control unit of the system of the present invention. Included is a mode selector 27. This is an eight position rotary selection switch and is the primary mode selection control. The switch positions are: 
     
         ______________________________________PF             Pre-FlightTO             TakeoffCLB            ClimbCRZ            CruiseTBC PEN        Turbulent Air PenetrationDSNT           DescentHLD            HoldingAPP            Approach______________________________________ 
    
     Some of the primary modes have one or more variations or sub-modes. To select such a PAGE switch 29 is used to select the desired variation. Each variation is identified by name of a Control Unit readout device or display 31. When a primary mode is first selected on the rotary switch, the paging sequence automatically advances to the first sub-mode which is the most frequently used variation, or, the variation the crew is encouraged to use in the interest of saving fuel. In that case the system performs its advisory functions with no further pilot action. The paging action is cyclic. Each time the PAGE button is pressed the system advances to the next sub-mode, and after the last sub-mode is reached the sequence circles back to the first sub-mode. Table I below tabulates all of the various modes and available sub-modes. An important thing to note is that because of the implementation of the present system with a dedicated computing apparatus rather than by means discrete logic or the like the pages can be added, deleted or rearranged without modifying any of the hardware. All that is required is proper reprogramming of the computer. 
     
                       TABLE I______________________________________PAS MODES, SUB-MODESNAME          DESCRIPTION______________________________________PRE-FLIGHT    Used to load data into systemTAKEOFF       Provides takeoff EPR settings for         indicated runway temperatureCLIMB         Provides climb profile data to         target flight level, tfl, for:ECON (tfl)    best fuel economySTD (tfl)     standard, fixed speed scheduleRATE (tfl)    best rate of climbANGL (tfl)    best climb angleICPT (tfl)    intercepting the target alti-         tude at a selected distanceCRUISE        Provides cruise advisory data and         mach number, M, for:ECON (M)      best specific ground rangeCNST (M)      selected constant mach numberMAX (M)       maximum available speedICPT (M)      intercepting a selected distance         in a selected time using minimum         fuel (not constant speed)TURBULENCE    Provides proper advisory data for         penetration of air turbulenceDESCENT       Provides descent profile data to tar-         get flight level, tfl, for:ECON (tfl)    best fuel economySTD (tfl)     standard fixed speed scheduleRATE (tfl)    best rate of descentANGL (tfl)    best descent angleICPT (tfl)    intercepting the target altitude         at a selected distanceHOLDING       Provides advisory data with display         of holding time available to reserve         fuel for:LINR (time)   linear holdingRCTK (time)   racetrack holdingAPPROACH      Provides advisory data for selected         flight path angle at:1530 (fpa)    approach flaps 15°, landing         flaps 30°2540 (fpa)    approach flaps 25°, landing         flaps 40°L30 (fpa)     landing flaps 30°L40 (fpa)     landing flaps 40°______________________________________ 
    
     Below PAGE is a button 33 labeled T/D; this is the TIME FOR DISTANCE button and used to cause time for distance data to be presented on the Control Unit readout 31 in lieu of the sub-mode annunciation data. The use of this type of data will be described in detail below. This is an illuminated button and lights when in the T/D mode. Below this button is a button 35 labeled DERATE. This button is used to select reduced thrust operation for takeoff and climb modes. When this button is on, the Engine Pressure Ratio commands are reduced in accordance with the airline&#39;s EPR reduction strategy, and the climb profiles are adjusted accordingly. As is the case in current airline practice, the crew must decide whether the takeoff conditions allow the use of reduced thrust. That is to say a decision must be based on a runway length, pavement conditions, ice, slush, etc. The DERATE lamp is not operative in any mode except takeoff or climb. 
     Below this button is a button labeled ENG OUT. This button 37 is used to tell the system that an engine is inoperative and the button is illuminated by an amber light when there is an ENGINE OUT status. This button must be used in conjunction with other input devices to inform the computer which engine is out. As shown on FIG. 2, there are a group of twelve buttons 38-49 on the left hand portion of the control unit. The buttons 38-47 are for entering the numerals 1 through 0 in the computer memory. A location in the memory is assigned to ENGINE OUT and upon initialization this location has stored therein a word indicating that all engines are operating. Pressing the ENGINE OUT button 37 will first cause the word ENG to be displayed on the display 31. This permits the pilot to use one of the numeric buttons to enter into the computer which of the engines is out. For example, if engine number 2 is out, he would press button 2. This number would then appear in the numeric portion of the display 31 and at the time be loaded into the computer. This can also be used in a PLANNING mode. Thus, the pilot may wish to get information regarding an ENGINE OUT condition and then return to his normal condition of all engines operating. In that case, he again presses ENGINE OUT and, assuming he had previously indicated that engine 2 was out, the display would show ENG 2. This word is now available for modification and he need only press the clear button 51 to clear this data whereupon the data will be taken out of the memory and the ENGINE OUT lamp will be extinguished. At any time there is an engine out condition, the ENGINE OUT light remains lighted. It is possible to set up any combination of engines as being out, the only condition being that there must be one engine operating. Although, it would be possible to provide an automatic input of an ENGINE OUT status, an engine is usually shutdown by the pilot. Thus, the system allows him to determine what would occur if the engine was shutdown and can aid him in his decision as to whether or not to shutdown using information based on the results of the performance advisory along with the other indications he has that may cause him to consider shutdown. Next to the PAGE button 29 is a button labeled DATA REQ&#39;D. This button 54 is used whenever the selected sub-mode requires the manual entry of data. Most modes do not require such entry. If a sub-mode does require the entry of data, this button illuminates and the display unit 10 remains blank until data is entered. The pilot acknowledges the request for data by pressing button 54 whereupon readout 31 tells him what information is required. For example, it might indicate DIST indicating the need for distance information. Thereupon using the numeric keyboard, the pilot enters the required distance information which, as he enters it will appear on the display 31. After entry he presses an INSERT button 50 to load this data into the computer. Once this data is accepted by the computer it advances to ask for the next piece of data required, if such is required. When all necessary data has been inserted, the DATA REQUIRED lamp 54 is extinguished and the readout reverts to its normal function of displaying the sub-mode. 
     Although the INSERT button 50 and CLEAR button have been explained above in connection with entry with different types of data their general modes of operation will now be explained. Pressing the INSERT button will cause the numeric data appearing on the readout 31 to be entered into the computer. However this occurs only if the INSERT lamp is illuminated prior to pressing it. The system is designed to light the INSERT button only when information is displayed which can be changed by the pilot. This is necessary since some displayed information is not subject to change. The CLEAR button serves two purposes. In conventional fashion, it may be used to recover from a keystroke error. In other words, if on entering data the pilot makes a mistake, he can clear that data and start over before entering it into the computer. The other purpose of the CLEAR button is to clear data already in the computer. If computer data is being displayed and if that data is capable of being changed, pressing CLEAR will clear the data then stored, cause the insert lamp to light and then permit entry of new data. The manner in which all of this occurs will become more evident in the explanation below. The remaining button 55 on the panel is the one labeled PLNG. This is the planning mode button which permits the pilot to place the system in a planning rather than an operational mode. As explained above this permits the pilot to plan ahead for future phases of the flight. Pressing the button once will place the system in the planning mode and illuminate this button along with amber planning light 23 on the display 10. Pressing it again will take the system out of the PLANNING mode and put it back into the operation mode, causing the associated lamps to be extinguished. 
     As is evident from their labeling the keyboard buttons 38-49 perform a dual function. In addition to being a conventional keyboard each button is also assigned an additional function. Each key is imprinted with name of a performance-related parameter and may be used to call up that parameter for display on the Control Unit display 31. As general rule, when the INSERT button is illuminated the keyboard is in the numeric mode and pressing one of the keys 38-49 will cause the corresponding number to appear in the display register 31. When the INSERT light is not illuminated the keyboard is in the &#34;parameter&#34; mode and pressing a key will cause the value of the corresponding parameter to appear on the readout 31. Generally, the parameter will be displayed only as long as the button is depressed, and when the button is released the readout will revert back to its normal function. However, in some instances the system interprets the action as a cue that the pilot wishes to insert a new value for the parameter. When such is the case, pressing the key causes the present value of the corresponding parameter to be displayed and the INSERT button 50 to illuminate. The pilot may then clear the display and key in a new number and then press the INSERT button 50. If he does not wish to revise the number, he can simply press INSERT button and the display 31 returns to its normal function. The twelve parameters available for the illustrated system which is specifically designed for a Boeing 727 aircraft are as follows: 
     
         ______________________________________Key #   Parameter  Name______________________________________1       MACH       Mach2       GS         Ground Speed3       NGM        Nautical Ground Miles/1,000 lbs.              (Specific ground range)4       FF         Fuel Flow - per engine5       DIST       Distance Capability to reserve              fuel6       BUF        Buffet Margin7       GW         Gross Weight8       IAS        Indicated Airspeed9       TAT        Total Air Temperature.       FUEL       Total Fuel Quantity0       ALT        Altitude--      WIND       Wind Component______________________________________ 
    
     As will be shown in more detail below, the computer continually obtains inputs relating to fuel quantity, flap angle, altitude, true airspeed, mach number, static temperature, and valve positions. The pilot enters other information necessary for the computations. The information which is entered by the pilot is listed in Table II. This is done with the selector switch 27 in the PF-i.e. Pre-Flight Mode. The code words of the table are presented to the pilot on the readout 31 and the pilot enters the necessary data in the manner described above. When the system is in the planning mode, the parameters which normally are obtained from sensors in the aircraft can also be inserted by the pilot for planning purposes. 
     
                       TABLE II______________________________________DATA ENTRY ORDERCODE   PARAMETER          UNITS      NOTE______________________________________ZFW    Zero fuel weight   lbs. × 1,000RSAL   Reserve and alternate fuel                     lbs. × 1,000DELV   Elevation at destination                     ft. × 1,000  airportDIST   Trip distance      NMCRZW   Averge cruise wind component                     ±KTSCLBW   Average climb wind component                     ±KTS    *TROP   Tropopause altitude at top                     ft. × 1,000  of climbCZFL   Planned initial cruise                     FL  altitudeCZ °C.  Outside air temperature at                     ± °C.                                **  planned cruise FLRW °C.  Outside air temperature at                     ± °C.  takeoff runway______________________________________ NOTES *A numeric value equal to 60% of the cruise wind component will appear in the display when the CLBW parameter is requested. If the pilot has no better estimate of average climb wind it is suggested he use this value. **A numeric value corresponding to the standard day temperature for the planned cruise flight level is displayed when the CZ °C. parameter is requested. This facilitates entry in those cases where the pilot is given a temperature deviation rather than a temperature. (He can mentally add the deviation to the standard temperature and insert the result.) 
    
     Any time when power is first applied or after a power interruption of sufficient duration results in loss of stored data, the system generates a message to the pilot that instructs him to go into the pre-flight mode, an indication being given on the readout 31 &#34;GO TO PF&#34;. 
     Table III of FIGS. 3A-C is a summary of the operation in various modes mentioned above. The left section of the table indicates the mode selection parameters and necessary input data. The middle section illustrates the data displayed on the control unit readout 31 and the right hand section indicates what is displayed on the display unit 10. The middle section also illustrates the possibility of a &#34;time for distance&#34; display. As indicated, in the climb, cruise, turbulence penetration, distance modes, this function is operable. The computer continuously computes time for distance data whether or not the time for distance button 33 of the control unit of FIG. 2 is pressed or not. Pressing the buttom simply controls the display mode. On the display, the first alphanumeric display character displays the first letter of the sub-mode identification. The next three characters give time in hour and minutes and the last four numeric displays the distance in nautical miles. 
     In the climb and descent modes the distance displayed is the ground distance that remains to be travelled in reaching the target altitude using the selected profile. When in cruising or turbulence penetration mode the distance may be set or revised at any time by the pilot using clear/insert sequence. The distance counts down automatically as a function of the ground speed &#34;advisory&#34; i.e., the ground speed that should occur if the pilot follows the IAS Advisory with the wind manually inserted. This distance is called the cruise distance. The displayed value of time is the time it will take to cover the distance using the selected sub-mode profile. It should be noted that the best fuel economy can be achieved by flying a varying speed profile wherein the speed is reduced as the aircraft weight decreases with fuel burnoff. However, it is difficult to estimate the time to go in a varying speed profile. The time to distance function provides time to go information that takes into account the fact that the speed will continue to vary. With altitude changes, best fuel economy sometimes requires relatively low rates of climb or descent. The time and distance to target altitude data assist the pilot in complying with ATC requirements while at the same time saving fuel. 
     The system also has some advisory alert functions which are used in the cruise mode after the aircraft has settled at a flight level and has tracked the IAS advisory for a reasonable time. One of these is a step climb alert which is given when the weight has decreased to the point where the aircraft has altitude capability for a 4 thousand foot step climb. A flashing ALT message on the display 31 is given. This message is cancelled by pressing the ALT key and is re-issued at 10 minute intervals if the condition does not change. Also given is a speed alert. This occurs when the aircraft speed differs from the IAS advisory by more than three knots, with sporadic pertubations due to wind variations filtered out. The system displays a flashing IAS message on the display 31. This message can also be cancelled by pressing the IAS key and is also re-issued at 10 minute intervals if the speed is not brought within range. 
     Returning to FIG. 2, there is also shown a test button 60. This is used to perform a lamp test and will cause all segments of all displays to be lighted. In addition, the six pushbuttons on the control panel will illuminate along with the planning light on the display unit. The page and clear buttons as well as the keyboard buttons are not lighted by the computer. In addition, there is automatic monitoring equipment to detect the burn out of one of the segments in the alpha-numeric displays to prevent displaying erroneous data. Circuitry causes the entire digit to be blanked whenever the system tries unsuccessfully to light a critical segment. Furthermore, the computer has built into it self-testing functions and upon detecting a failure blanks the display unit and places a warning message on the display 31 of the control unit with a code number indicating the basic nature of the malfunction. 
     FIG. 4 is a basic functional block diagram of the system of the present invention which permits carrying out the types of functions described above. Shown is the display unit 10 described above along with the control unit 24. These are coupled over appropriate busses 63 and 64, on which data and addresses can be fed, to a micro-processor 65 having associated therewith a memory 67. An example of a computer which may be used is the SECS-11 micro-processor manufactured by Electronic Memories and Magnetics Severe Environmental Products Division. As is conventional in such systems, the memory will include read only memory in which the fixed program is stored along with random access memory for storing data which changes. The micro-processor provides appropriate outputs to the display unit 10 and control unit 24. It receives inputs from the control unit relating to the parameters described above. The micro-processor also receives inputs from fuel quantity sensors 69, calibration controls 70 flap position sensors 82, dimming controls 73, the engine pressure-ratios 74, static air temperature, altitude and mach number indicator 75, bleed air switches 77, distance measuring equipment 78, thermal anti ice switches 79 and airdata computers validity 81. The inputs from sensors 69, 70 and 73 are provided to a multiplexer 83. The multiplexed analog data is converted to digital data in an analog to digital converter 85. Outputs of sensors 74, 75 and 78 are inputs to a multiplexer 84. This synchro data is converted to digital data in a synchro to digital converter 86. The remaining data is digital in nature and is supplied through an isolation and bus interface 88. 
     The system is shown in more detail in FIG. 5. An output from a fuel quantity sensor from each tank, which is in analog form, is coupled over a line 91 to a signal conditioner 93 the output of which is an input to the analog multiplexer 83. The analog multiplexer receives an input from a cyclic address generator 97. The cyclic address generator also provides signals into OR gate 99 the outputs of which are provided to a random access memory 101. The output of the analog multiplexer 83 is coupled through the analog digital converter 85 as a data input to the random access memory. The cyclic address generator, in sequence, addresses each of the analog multiplexer inputs causing them to be supplied at the output through the analog digital converter 85 to the random access memory 101. At the same time as it is addressing the multiplexer it is also addressing the random access memory. Thus, the data associated with a particular memory location is accessed both in the multiplexer 83 and the memory 101 so that the proper data is stored in each location. 
     Digital inputs on lines 105 are provided into the data bus interface element 88 which is addressed by an address decoder 107. A similar address decoder 109 is associated with the random access memory 101. Since these inputs are digital in nature, there is no need for conversion and storage. 
     Angular input information such as the mach input on line 109, the altitude inputs on lines 110 and 111, the DME inputs on lines 112, 113 and 114, the EPRs on lines 115, 116 and 118 and the static temperature on line 117 are coupled into the analog multiplexer 88 the output of which is provided to the synchro to digital converter 86. The output of this device is provided to another random access memory 123. An additional cyclic address generator 125 addresses the analog multiplexer 88 and the random access memory 123 together causing the input information to be stored in the proper memory locations. Once again, an OR gate 127, actually a plurality of OR gates 127, one for each bit of the address and an address decoder 129 are provided. 
     The information available on the various input lines such as 91 and 109, 111, 113, 115, 117 along with the information on lines 105 will all be available either in the random access memories 101 and 123 or at the data bus interface 88. Shown in the middle of the figure is a central processing unit 131 which is coupled to a fixed program memory 133. In conventional fashion, the central processing unit will have a combined address data bus 137. Bus 137 may be a 16 bit parallel time multiplexed bi-directional data bus that carries both data and addresses. During the address part of a cycle, the address decoders function in parallel, however, only the addressed module may respond and place data on the lines. 
     The central processing unit will operate in accordance with programs stored in the fixed program memory 133 which programs are attached hereto. In general the central processing unit 131 in accordance with the stored program, when obtaining input data can address, over the bus 137, any of the input modules. The respective address decoders 107-109 and 129 determine which of the three input sections are being addressed. The remainder of the address is used through the OR gates 99 or 127 or directly into the interfacing equipment 88 to select the byte of memory therein which is desired. Thus, the central processing unit 131 can address the random access memory in the same manner as can the cyclic address generators 97 and 125 to retrieve data. During access by the central processing unit 131 the cyclic address generators are disabled. 
     The right hand side of FIG. 5 illustrates the manner in which the outputs are provided to the display unit 10 and the manner in which inputs are taken from and outputs provided to the control unit 26. The outputs from the central processing unit on the bus 137 are provided through word to byte interface modules 139 and 141 respectively. The data output on bus 143 from the data multiplexer 139 is coupled to a random access memory 145 associated with the display unit 10, to a random access memory 147 associated with the control unit 12 and to data bus interface element 149 also associated with the control unit 12. The address information out of the address control 141 on bus 151 is coupled to an address latch 153 associated with the display unit 10 and an input address latch 155 associated with control unit 12 and also an output address latch 157 associated with control unit 12. The bus 143 to the control and display units is an eight bit bi-directional time multiplexed data bus. The interface module 140 simply converts the 16 bit bus to an eight bit bus. For both busses, control signals now shown on the diagram control the direction and function of the busses. As data for the various displays is computed it is transferred to the random access memories 146 and 147 in accordance with the selected address placed in the address latches 153 and 155, the outputs of which are coupled through OR gates 159 and 161 to the random access memories 146 and 147. This is the display information. To get the information from the random access memory out to the actual displays cyclic address generators 163 in the display unit 10 and 165 in the control unit 12 are used. The addresses are coupled through the OR gates 159 and 161 to access the proper data location for the desired display. The digital outputs from the memories 146 and 147 are coupled through display decoder drivers 167 and 169 respectively to segmented digit display matrices 171 and 173 respectively. The display matrices 171 and 173 also receive as inputs, through a block 175 and 177 respectively, the selected address generated in a cyclic address generator 163 and 165. 
     The keyboard pushbuttons 179 provide their outputs to an encoder 181 which includes latching in conventional fashion the output of which, now in suitable format for the micro-processor, is coupled into data bus interface element 149. As noted above, this is addressed by the address latch 157 permitting the micro-processor to scan the input data entered at the control and provide this data as outputs on the data bus 143 and use this information as required in the program. As with the cyclic address generators for other memories, means are provided to detect an associate memory being accessed by the central processing unit 131 and to interrupt cycling until the desired data is removed from or stored in the memory. 
     Attached hereto is program for carrying out the present invention. As will be recognized by those skilled in the art, the program contains therein the well known flight equations i.e., the same types of equations which were used to draw the charts contained in the performance book formerly used for calculating by hand the type of information provided by the system of the present invention. ##SPC1## ##SPC2## ##SPC3## ##SPC4## ##SPC5## ##SPC6##