Aircraft flight instrument display system

We claim:

1. Display apparatus having a display face comprising

raster generating means for generating a raster on said display face including digital timing circuit means for providing digital signals synchronous with respect to said raster,

first memory means responsive to said digital signals and having a plurality of storage locations corresponding to a respective plurality of display cells comprising said display face,

said digital signals addressing said storage location corresponding to said display cell associated with the point of said raster being generated,

said storage locations containing symbol defining words each comprising a symbol address field and a symbol shifting field,

said first memory means providing a symbol address signal and a symbol shifting signal corresponding to said symbol address and symbol shifting fields respectively of said symbol defining word stored at said storage location addressed by said digital signals,

symbol shifting and storage means responsive to said symbol address signal and said symbol shifting signal including second memory means responsive to said symbol address signal and having a plurality of symbol storage means for storing a respective plurality of symbols and patterns to be displayed with respect to said display cells, said plurality of symbol storage means being addressed by said symbol address signal for providing symbol display signals in accordance with said symbol or pattern stored in said addressed symbol storage means and shifted in response to and in accordance with said symbol shifting signal, and

display means responsive to said symbol display signals for displaying said symbol or pattern stored in said addressed symbol storage means shifted with respect to said display cell associated with said point of said rester being generated in accordance with said symbol shifting signal.

2. The apparatus of claim 1 in which

said raster generating means comprises raster sweep generating means for providing the horizontal and vertical sweep wave forms for generating said raster, and

said digital timing circuit means comprises means for providing a first digital signal representative of a raster line being generated.

3. The apparatus of claim 2 in which said symbol shifting and storage means includes first symbol shifting means responsive to said first digital signal and said symbol shifting signal for combining said signals and providing a combined signal in accordance therewith.

4. The system of claim 3 in which said symbol storage means of said second memory means comprises a matrix of bit locations for storing bits arranged in accordance with said symbol stored therein, said matrix of bit locations corresponding to a matrix of respective resolution elements comprising each said display cell,

the rows of said matrix of bit locations being addressed by said combined signal for providing said symbol display signals in accordance with the row of bits stored in said addressed row of said addressed symbol storage means,

thereby displaying said stored symbol shifted in accordance with said symbol shifting signal.

5. The apparatus of claim 4 in which said first symbol shifting means comprises algebraic addition means for algebraically adding said symbol shifting signal to said first digital signal thereby providing said combined signal as the algebraic sum thereof.

6. The apparatus of claim 4 in which said symbol shifting and storage means includes second symbol shifting means responsive to said addressed row of bits and said symbol shifting signal for providing said symbol display signals in accordance with said row of bits provided in serial fashion in a sequence in accordance with said symbol shifting signal, thereby displaying said stored symbol shifted in accordance with said symbol shifting signal.

7. The apparatus of claim 6 in which said second symbol shifting means comprises

shift register means coupled to receive said row of bits from said addressed row of said addressed symbol storage means for serially shifting said row of bits therethrough, and

sequence selection means coupled to the stages of said shift register means and responsive to said symbol shifting signal for selective coupling to the stages of said shift register means in accordance with said symbol shifting signal to selectively provide said sequence of said row of bits, thereby displaying said stored symbol shifted in accordance with said symbol shifting signal.

8. The system of claim 7 in which said digital timing circuit means includes

a clock pulse source of providing a clock pulse signal,

first digital counting means responsive to said clock pulse signal for providing an X-digital count signal in accordance therewith and a horizontal sync pulse at a predetermined count of said first counting means,

second counting means responsive to said horizontal sync pulses for providing a Y-digital count signal in accordance therewith and a vertical sync pulse at a predetermined count of said second counting means,

said second counting means providing said first digital signal representative of a raster line being generated,

said X and Y digital count signals comprising said digital signals,

said raster sweep generating means being responsive to said horizontal and vertical sync pulses for synchronizing said horizontal and vertical sweep wave forms,

said shift register means being responsive to said clock pulse signal for serially shifting said row of bits therethrough in response to said clock pulse signal.

9. The system of claim 8 in which each said symbol defining word further includes a video field and a priority field, said first memory means providing a video and a priority signal corresponding to said video and priority fields, respectively, of said symbol defining word stored at said location addressed by said digital signals.

10. The apparatus of claim 9 in which said first memory means, said symbol shifting and storage means, said second memory means and said first and second symbol shifting means comprise a channel of said apparatus, said apparatus comprising a plurality of said channels.

11. The apparatus of claim 10 further including priority and video selector means responsive to said serially provided row of bits from said sequence selection means, said video signal and said priority signal from each said channel for transmitting the video signal of said channel having the priority signal of largest value and having the serially applied bit in an enabling state, thereby providing a transmitted digital video signal whereby the symbols provided by said respective channels are superimposed on said display face.

12. The apparatus of claim 11 in which said priority and video selector means further includes means for providing the video signal of said channel having the video signal of largest value of those channels having priority signals of the same value.

13. The apparatus of claim 12 in which said priority and video selector means comprises

a plurality of decoder means responsive to the serially provided row of bits, said priority signal and said video signal from said channels, respectively for decoding said priority and video signals and transmitting said decoded signals when said serially applied bit is in said enabling state, and

priority encoder means responsive to said transmitted decoded signals for encoding said signals thereby providing said transmitted digital video signal.

14. The apparatus of claim 11 in which said display means includes cathode ray tube means, the screen thereof providing said display face, said horizontal and vertical sweep wave forms being applied to said cathode ray tube means to generate said raster on said screen.

15. The apparatus of claim 14 in which said display means further includes digital-to-analog converter means responsive to said transmitted digital video signal for providing a corresponding analog video signal to said cathode ray tube means, thereby displaying said symbols or patterns stored in said addressed symbol storage means in said channels with respect to said display cell associated with said point of said raster being generated.

16. Display apparatus having a display face for displaying sky-ground shading thereon comprising

raster generating means for generating a raster on said display face including digital timing circuit means for providing a digital signal synchronous with respect to the lines of said raster,

raster line memory means responsive to said digital signal and having a plurality of storage locations corresponding to a respective plurality of raster lines comprising said raster,

said digital signal addressing said storage location corresponding to said raster line being generated,

said storage locations containing sky-ground shading defining words each comprising a cross-over field and a video field, said cross-over field representative of the point at which said raster line crosses the horizon boundary between said sky and said ground shading and said video field representative of one of said sky or ground shadings,

said raster line memory means providing a cross-over signal and a video signal corresponding to said cross-over and video fields respectively of said sky-ground shading defining word stored at said storage location addressed by said digital signal, and

shading selector means responsive to said cross-over signal and said video signal for providing a video shading signal representative of either of said sky and ground shadings when said raster line prior to said cross-over point is being generated and the other of said shadings when said raster line subsequent to said cross-over point is being generated.

17. The apparatus of claim 16 in which said video selector means comprises

cross-over point detector means responsive to said cross-over signal fpr providing a cross-over detection signal when said raster line being generated crosses said horizon boundary, and

code changer means responsive to said video signal and said cross-over detection signal for changing the video code from one said shading to the other said shading when said cross-over detection means provides said cross-over detection signal.

18. The apparatus of claim 17 in which said cross-over detection means comprises counter means for providing a count signal in accordance with said cross-over signal thereby providing said cross-over detection signal.

19. The apparatus of claim 11 including said digital timing circuit means for providing a raster line digital signal synchronous with respect to the lines of said raster, said apparatus including a channel for displaying sky-ground shading on said display face comprising

raster line memory means responsive to said raster line digital signal and having a plurality of storage locations corresponding to a respective plurality of raster lines comprising said raster,

said raster line digital signal addressing said storage location corresponding to said raster line being generated,

said storage locations containing sky-ground shading defining words each comprising a cross-over field and a video field, said cross-over field representative of the point at which said raster line crosses the horizon boundary between said sky and said ground shading and said video field representative of one of said sky or ground shadings,

said raster line memory means providing a cross-over signal and a video signal corresponding to said cross-over and video fields respectively of said sky-ground shading defining word stored at said storage location addressed by said digital signal, and

shading selector means responsive to said cross-over signal and said video signal for providing a video shading signal representative of either of said sky and ground shadings when said raster line prior to said cross-over point is being generated and the other of said shadings when said raster line subsequent to said cross-over point is being generated.

20. The apparatus of claim 19 in which said video selector means comprises

cross-over point detector means responsive to said cross-over signal for providing a cross-over detection signal when said raster line being generated crosses said horizon boundary, and

code changer means responsive to said video signal and said cross-over detection signal for changing the video code from one said shading to the other said shading when said cross-over detection means provides said cross-over detection signal.

21. The apparatus of claim 20 in which said cross-over detection means comprises counter means for providing a count signal in accordance with said cross-over signal thereby providing said cross-over detection signal.

22. The apparatus of claim 19 in which each said sky-ground shading defining word includes a priority field with said raster line memory means providing a priority signal corresponding thereto.

Description Submit all comments and votes

BACKGROUND OF THE INVENTION

This invention relates, in general, to aircraft flight instrumentation and, more particularly, to apparatus for providing a display of a cluster of instruments that is positioned directly in front of the pilot and which provide him with the primary flight guidance information necessary to control an aircraft through its entire flight regime from takeoff to landing.

The prior art equipment used for primary flight data comprises ten dedicated instruments which are typically spread over a panel area that is approximately 16 inches wide by 13 inches high and requires the pilot to cover a visual scan radius of 10 inches from the center of the attitude-director indicator to cover the multitude of information which is competing for his attention. This wide scan area and excess of extraneous information is particularly distracting during a landing maneuver under low visibility conditions when only a limited number of key parameters are necessary and should be very readily apparent to be effective during this critical maneuver.

The present invention utilizes the digital raster cellular CRT technique disclosed in the patent application Ser. No. 630,833, filed Nov. 11, 1975, titled "Digital Raster Display Generator", invented by P. L. Narveson and assigned to the Sperry Rand Corporation who is also the assignee of the present invention. Said Ser. No. 630,833 issued on Jan. 24, 1978 as U.S. Pat. No. 4,070,662 which is considered incorporated herein by reference. The cell technique disclosed therein enables all the information on the entire cluster of ten electromechanical instruments to be presented in a clear and concise format on a usable CRT screen size that is typically 6.4 inches wide and 4.8 inches high, achieving a scan radius reduction from 10 inches to four inches and a panel area reduction from 130 square inches to 48 square inches. Only that data necessary for a particular phase of the flight mission need be presented with all other information suppressed until required.

The use of the digital raster CRT writing technique is ideally suited to interface with serial digital bus transmission of data which typically requires only a few wires to convey a multitude of information and therefore lends itself to very efficient switching of information from one source to an alternate source should one source of data become invalid.

Another key capability of the digital raster CRT technique is the assignment of priority of symbology to specific areas of the screen. This minimizes any conflict of data presentation and is particularly effective, for instance, in reducing cutter and eliminating parallax of the flight director command cue presentation that is typical of conventional electromechanical attitude director indicators.

Unique circuits that are disclosed herein relate to overlay of sky-ground shading to display an artificial horizon and apparatus to move symbology smoothly from one cell to an adjacent cell in any direction. Additionally the apparatus is configured to provide unique aircraft displays in a manner to be described.

SUMMARY OF THE INVENTION

A CRT display is provided having a display face arranged in an array of major cells, each major cell comprising an array of resolution elements. A map memory containing a map word for each major cell is addressed by digital raster generation circuitry in accordance with the cell upon which the beam is impinging. The map word includes, inter alia, a symbol field and a shift field. A symbol memory storing the symbols to be displayed is addressed by the symbol field of the map word for providing video signals for displaying the addressed symbol in the major cell through which the beam is scanning. Circuitry is included for combining the shift field with the symbol memory addressing signal so as to effect a symbol shift in the Y direction. The shift field is also utilized to effect a shift of the bits from the symbol memory output thereby providing a shift of the symbol in the X direction.

Sky-ground shading is provided by a display channel including a raster line memory having storage locations corresponding to each of the raster lines, each location including a sky-ground shading control field representative of the X dimension at which the corresponding raster line crosses the displayed horizon line. Circuits are included for changing the shading from sky to ground or vice versa in accordance with the information stored in the sky-ground shading control field.

The apparatus of the present invention provides a plurality of unique display formats including a horizon line cooperative with a central reference index and a bank attitude scale having a zero bank angle index laterally displaced from the central reference index and movable vertically as a function of pitch attitude, the spacing of the bank scale markings being varied as a function of craft pitch and roll attitude. The vertical movement of the horizon line and the bank angle scale is further limited for pitch angle greater than a predetermined value and a pitch attitude scale including a zero pitch angle index which is fixed for pitch attitude less than said predetermined value is correspondingly moved for pitch attitude greater than said predetermined value. A unique flight director symbol is also provided and comprises right-left and up-down spaced triangularly shaped arrow heads respectively connected by straight line arrow shaft lines, the spacing between the bases of the arrow heads defining a finite area corresponding to the area of a rectangularly shaped aircraft reference index whereby when the flight director commands are satisfied, the arrow heads project symmetrically beyond said reference index. A further unique display symbology is provided for indicating air speed parameters and comprises a vertical numeric scale movable in accordance with changes in air speed and an air speed reference index representing a predetermined desired air speed which is moved with said air speed scale when the value of the numeric air speed scale corresponds with the reference index. Typically reference air speed indices are provided for desired critical air speeds such as, during take-off, air speed corresponding to decision speed V.sub.1, rotation speed V.sub.R and safety speed V.sub.2. The movable air speed scale may be obscured until the V.sub.2 index corresponds with the V.sub.2 speed and scale air speeds above V.sub.2 will be thereafter displayed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of the functional areas of the integrated CRT flight instrument display of the present invention;

FIG. 2 is a pictorial representation of a typical integrated flight instrument display format;

FIG. 3 is a pictorial representation of roll, pitch and flight director symbology of the display of the present invention;

FIGS. 4A-4D are pictorial representations of air speed display formats utilized during take-off and climb of the aircraft;

FIGS. 5A and 5B are pictorial representations of navigation display formats utilized in the display of the present invention;

FIGS. 6A-6C are pictorial representations illustrating alternate pitch scale formats utilized in the display of the present invention;

FIGS. 7A and 7B are pictorial representations illustrating further alternate pitch scale formats;

FIG. 8 is a schematic block diagram embodying the aircraft flight instrument display system of the present invention;

FIG. 9 is a schematic block diagram illustrating details of the display processor of FIG. 8. FIG. 9 also includes a format diagram of the address and data words utilized in the apparatus;

FIG. 10 is a pictorial representation of typical digital raster alphanumeric fonts;

FIG. 11 is a pictorial representation of typical dynamic symbology utilized in the display of the present invention;

FIG. 12 is a diagram illustrating geometrical parameters utilized in generating the horizon shading;

FIG. 13 is a schematic block diagram illustrating details of the symbol channel of FIG. 8;

FIG. 14 is a schematic block diagram illustrating details of the horizon shading channel of FIG. 8; and

FIG. 15 is a schematic block diagram illustrating details of the video encoder of FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates how the usable CRT face is divided into functional display areas that contain equivalent information to that provided by typical electromechanical instruments that the single CRT display will replace. The screen is composed of 1024 major cells arranged in an array of 32 cells wide by 32 cells high. Each cell is rectangular in shape with typical dimensions of 0.20 inch wide by 0.15 inch high. The entire usable screen is scanned by a cathode ray which impinges on the light emitting phosphor in a repetitive interlaced manner to form 512 horizontal lines spaced approximately 0.0094 inches apart. The refresh rate of each interlaced frame is typically 100 hertz. The format of the smybology within each cell is generated in four contrasting gradations of light output. For convenience these are designated as black, ground shade, sky shade and bright in this disclosure. The light output within each cell is controlled with a resolution consistent with a 16 .times. 16 matrix of picture elements, designated PELS. Each PEL is typically 0.0125 inch wide by 0.0094 inch high and is controlled sequentially by a digital processor to have any of the four available gradations of light output during each sweep of the cathode ray across the screen.

FIG. 2 is a typical CRT display format that illustrates the capability of the invention. The format shown is particularly applicable to the approach and landing phase. The four gradations of light output are black where there is no shading on the diagram; ground shade where the shading on the diagram is composed of vertical lines; sky shade where the shading on the diagram is composed of horizontal lines. All other symbology is generated in bright shade and is shown as solid black lines on the diagram and thus FIG. 2 may be considered as a photographic negative.

The aircraft reference index at the center of the display field of view has the general shape of an aircraft and comprises a rectangular symbol representing the aircraft nose of fuselage and a pair of laterally extending bars representing its wings. The rectangular symbol is two cells wide by two cells high and has a black interior background with a bright outline. The numeric readout within the rectangle represents the flight path angle of the aircraft. The granularity of the flight path angle readout is 0.1 degree for angles between plus and minus 10 degrees and one degree beyond this range. When the granularity is one degree, that is, when flight path angle is .+-. 10.degree. or greater, both numerics are the large size. The large numeric is contained in an area that is 12 PELS wide and 26 PELS high. The small numeric is exactly half the size of the large numeric, contained in an area that is 6 PELS wide and 13 PELS high (for example the numerics of FIG. 10). It will be understood that in some applications it may be desirable to display a numeric readout of pitch attitude rather than flight path angle. The area of the nose symbol has priority over the sky-ground shading and the flight director symbol which will be described in the following paragraph. Thus, the flight director symbol will disappear behind the nose symbol as it moves toward the center of the screen.

As shown in FIG. 3, the flight director symbol 100 is four cells wide by four cells high. It consists of two crossed lines or arrow shafts which connect four triangles or arrow head. The length of the crossed lines are exactly two cells. The position of the flight director cue 100 relative to the aircraft nose symbol 101 in FIG. 2 is a command to fly up and fly right. The movement of the center of the cue 100 relative to the nose 101 is limited to .+-.3 cells laterally and .+-.6 cells vertically. When the commands are satisfied, the crossed lines will be completely obscured by the nose symbol 101 and only the arrows will be in view as indicated at 102. Small deviations in cue movement are very apparent as is indicated in FIG. 2 where one or more of the arrows are partially or completely obscured. Those arrows which are completely in view indicate the direction of the corrective action to be taken to satisfy the commands. It is thus appreciated that the format of the flight director symbol and the priority of the nose symbol result in exceedingly clear and uncluttered presentations of both major and minor control commands or adjustments when they are required.

Referring to FIG. 2, the horizon presentation is shown in an area that is centered about the nose symbol and is 12 cells wide and 22 cells high. The horizon is the boundary between the sky shade (horizontal lines) and the ground shade (vertical lines). The presentation shown in FIG. 2 is 4.2 degrees nose up and 10 degrees right wing down relative to the horizon. A digital readout or roll angle with a one degree granularity is presented at the top center of the horizon display area. A qualitative display of the combined pitch and roll attitude is represented by the relative position of the stationary aircraft symbol (101, 103, 104 -- FIG. 3) to that of the moving boundary between sky shade and ground shade. A combined analog presentation of pitch and roll attitude is given by the moving array of vertical indices just to the left of the left wing tip 104. When the pitch attitude changes the indices move relative to the adjacent fixed pitch scale which has a range of .+-.22.5 degrees in the typical format shown in FIG. 2. It should, of course, be understood that the scale factor of the pitch movement is not restricted to that shown in FIG. 2 which is three vertical cells per 5 degrees. The magnitude of the pitch angle can be interpolated by the relative position of the solid triangle 105 of the array of vertical indices against the pitch scale.

The horizon shading is limited to a pitch range of plus and minus 17 degrees to ensure that the horizon presentation area is not shown in a single shade. This allows the pilot to always evaluate his relative position with respect to the sky and ground. While the horizon shading is limited, the triangle 105 will always indicate the correct value of pitch through a range of plus or minus 22.5 degrees. Such limiting is accomplished by freezing the pitch digital data from the processor for pitch altitudes greater than .+-.17.degree..

The magnitude of the roll angle can be interpolated by the position of the horizon line relative to the four inclined indices above and below the triangle 105. The indices or roll graduation marks represent 10, 20, 30 and 45 degree bank angle references, respectively, and are inclined to the top of the fixed airplane symbol accordingly. The inclination of each graduation is constant while the array moves vertically as a function of pitch attitude. The spacing between the indices, however, varies as a function of pitch attitude in accordance with the relationship as indicated on FIG. 3. The value of B or lateral displacement between the reference airplane and roll scale in FIG. 3 is typically 6 cells. The unique array of the indices allows the pitch and roll angle of the aircraft to be determined by the pilot in a very natural manner within a very small scan area.

A digital readout of radio attitude is presented at the bottom center of the horizon area. It has a range of 3000 feet above the terrain and will disappear for values greater than 3000 feet. The granularity of the readout is one foot between zero and 100 feet, ten feet between 100 and 400 feet and 100 feet above 400 feet. An analog presentation of radio altitude is available when the value is less than 200 feet. It appears as two segmented horizontal bars which rise to meet the bottom of the fixed airplane symbols 103 and 104 as the altitude above the terrain decreases to zero with the zero value indicated when the bars contact the bottom of the airplane symbol. The internal area of the bars will flash when radio altitude is less than 100 feet, thus acting as an alert signal to the pilot. A third bar is positioned between the radio altimeter bars with its position with respect to the bottom of the nose symbol 101 representing the rate of change of radio altitude. The scale factor of the radio rate display is such that a continuous alignment of the radio displacement bars with that of the radio rate symbol after an initial alignment will result in an exponential flare maneuver which will have a typical touchdown rate of descent of between two to four feet per second.

The scale to the lower left of the pitch scale is used to display wind shear in knots per 100 feet. It is derived by using the wind data generated by the automatic navigation system, subtracting the tower-reported wind at the runway and dividing by the altitude derived from the radio altimeter.

As indicated in FIG. 1, the area at the extreme left of the screen is dedicated to the airspeed-Mach indicator functions. The top portion of the area is used for a digital readout of Mach number. It occupies an area that is four cells wide by three cells high. The format of the remainder of the airspeed display varies with the mode of operation. The modes are takeoff, climb and cruise, approach and landing. The format shown in FIG. 2 is typical of the approach and landing mode. FIGS. 4A-4D illustrate the progress of the airspeed formats during take-off and climb. FIG. 4A shows a typical situation during the ground roll prior to attainment of decision speed V.sub.1. In the specific case shown a total of seven reference speeds are displayed. These correspond to decision speed V.sub.1 (135 knots), V.sub.R (rotation speed -- 140 knots), V.sub.2 (take-off safety speed -- 150 knots), flap retraction speed (V.sub.3 -- 195 knots), climb speed below 10,000 feet (V.sub.4 -- 250 knots), optimum climb speed above 10,000 feet (V.sub.5 -- 310 knots) and a Mach reference speed (V.sub.M corresponding to M = 0.820).

The large numerics at the left center of the screen represent the existing airspeed of the aircraft in knots.

The numerics occupy a space that is three cells wide and two cells high and have the highest priority; that is, no other symbology can intrude into the space. In FIG. 4A, the space with the diagonal lines normally is used to display a moving airspeed scale at a typical gradient of four vertical cells per 10 knots. The diagonal lines serve to effectively obscure the airspeed scale and are used to indicate that the aircraft has not attained take-off safety speed, V.sub.2. As the aircraft gathers speed, the V.sub.1, V.sub.R and V.sub.2 symbols will start to move upward from the positions shown in FIG. 4A when the scale is aligned with the respective symbol values. The condition shown in FIG. 4A is one where the V.sub.1 symbol is exactly aligned with a scale value of 135 knots and will begin to move upward as the aircraft increases its speed above 115 knots.

The situation shown in FIG. 4B illustrates the condition where the aircraft's speed is ten knots above take-off safety speed. The scale obscuration is removed and the scale is accordingly revealed for values greater than 150 knots. The scale symbology is suppressed in the area of the large numeric readout. In a dynamic situation the illusion is one where the airspeed scale appears to go behind the large numerics as it moves past the high priority area.

The reference airspeed values shown at the bottom of FIG. 4B will remain fixed until the bottom of the airspeed scale coincides with the specific value of the reference that is closest to the scale, at which time the reference values will index upward in the manner shown in FIG. 4C where the 250 knot reference (V4) is adjacent to the actual airspeed value. The reference airspeed identified with the letter M represents the airspeed that corresponds to the reference Mach number (0.820 in the typical case shown) at the existing attitude of the aircraft. The typical data shown in FIG. 4C is consistent with an existing pressure altitude of 5000 feet. The typical data shown in FIG. 4D is consistent with a pressure altitude of 22,400 feet. The airspeed reference values shown at the top of the airspeed scale in FIGS. 4C and 4D are beyond the range of the display and remain fixed in a manner similar to the references shown at the bottom of FIGS. 4A and 4B. The area with the diagonal lines in FIG. 4D represents airspeed values that are greater than the maximum operating airspeed V.sub.mo (375 knots in the typical case shown). It is thus seen that the take-off-climb airspeed display with its diagonal lines portrays the safe airspeed range which is between V.sub.2 and V.sub.mo. In general V.sub.mo is a function of altitude for a specific aircraft. The take-off safety airspeed V.sub.2 is typically a function of aircraft gross weight, flap/slat position, runway altitude and outside air temperature. The areas in FIG. 2 with the partial diagonal lines represent less than stall margin speed at the upper portion of the airspeed scale and greater than flap placard speed at the lower portion of the airspeed scale. The stall margin speed of the aircraft is typically a function of gross weight and flap/slat position. As indicated in typical FIG. 2, the actual speed of the aircraft is shown to be approximately midway between the flap placard speed and the stall margin speed.

The altitude display on the extreme right of FIG. 2 is arranged similar to that for airspeed. The space at the right center of the screen has maximum priority and is used for a digital readout of pressure altitude with a granularity of ten feet when vertical speed is less than 2000 feet per minute and 100 feet when vertical speed is greater than 2000 feet per minute. The space for the large numerics is three cells wide and two cells high. The large numerics represent flight level; that is, pressure altitude in 100 feet increments. The small numerics represent altitude increments of ten feet. The space above and below the numeric readout area is used to portray a moving altitude scale at a typical gradient of five vertical cells per 1000 feet. The altitude scale increases from bottom to top while the airspeed scale increases from top to bottom. This arrangement results in both scales moving in the same direction for a nose up manueuver. That is, a nose up maneuver generally will result in a decrease in airspeed and an increase in altitude. The series of short horizontal lines at the extreme right are spaced one cell apart in a vertical direction and represent altitude increments of 32 feet. Changes in altitude will result in a movement of the lines in a direction consistent with the change in altitude. That is, an increase in altitude will result in an upward movement of the short lines and vice versa. This will result in a sensitive and dynamic indication of vertical speed. It should be noted that movement of the altitude scale will be much slower and also will be in a direction opposite to that of the short lines. The readout at the top right of FIG. 2 represents the barometric correction required to align the pressure altitude scale and readout to be consistent with the local elevation with respect to mean sea level. The symbol just below the baro-set readout represents a selected altitude value which operates similar to the airspeed references previously described.

The sky shade area just to the left of the altitude scale and below the center represents a coarse analog presentation of altitude above the terrain as sensed by a radio altimeter. It is a bar thermometer type display which has the same gradient as the pressure altitude scale; that is, five vertical cells per 1000 feet. The gap between the center line and the bar represents altitude above the terrain and is consistent with the digital readout at the bottom center of the horizon display area. A unique feature of the radio altitude bar presentation adjacent to the pressure altitude scale is that relative motion between the top of the bar and the scale reflects either a rising or descending terrain. If the top of the bar moves down slower than the altitude scale, the terrain is rising; if the top of the bar remains aligned with the scale, the terrain is level; if the top of the bar moves down faster than the scale, the terrain is descending. The bar display will disappear when altitude above the terrain exceeds 3000 feet.

The vertical display format just to the left of the altitude presentation is used to portray vertical speed at a gradient of five vertical cells per 1000 feet per minute. The solid triangle moves along the fixed scale when vertical speeds are less than .+-.2000 feet per minute. The typical format shown in FIG. 2 represents a rate of descent of 700 feet per minute. A vertical rate of climb greater than 2000 feet per minute results in the solid triangle being positioned adjacent to the top box under the legend "KFPM". The value of rate of climb is displayed as a digital readout with a granularity of 100 feet per minute between 2000 and 10,000 feet per minute and 1000 feet per minute for vertical speeds greater than 10,000 feet per minute. A similar display is used for rates of descent with the solid triangle adjacent to the box at the bottom of the scale. The digital readout consists of a large numeric to represent 1000 feet per minute increments and a small numeric to represent 100 feet per minute increments. In order to provide the pilot with a sensory indication of craft vertical movement, especially when the vertical speed pointer is at one of its maximum positions, a series of space graduations is provided adjacent the vertical speed scale; and these graduations are moved in directions corresponding to the movement of the vertical speed pointer. This is especially useful in distinguishing vertical speed information from the motion of the altitude scale.

The vertical display format just to the right of horizon display area represents glide slope deviation. The sky shade area to the left of the legend "GS" represents the acceptable glide slope deviation at 100 feet above the runway. The solid bright triangle moves relative to the fixed scale. The pair of open triangles on either side of the null of the fixed scale represent deviations of 75 millivolts and 150 millivolts respectively. When the solid triangle is above the null, it represents a condition where the aircraft is below the center of the glide slope beam. The horizontal display at the bottom center of the screen represents localizer deviation in a manner similar to the glide slope display except that the sky shade area is expanded to have three times the sensitivity of the scale outside the sky shade area. The numeric readout above the localizer display represents the course of the particular localizer beam that the aircraft is following.

The heading display at the top of the screen comprises a large three digit numeric readout of aircraft heading with a granularity of one degree. The area of the numeric readout and adjacent legend "MAG HDG" has the highest priority similar to the airspeed and altitude readouts. The areas on either side of the numeric readout are used to display a moving scale of heading. When applicable an open triangle will move with the heading scale to represent selected heading references. The references will park themselves to the right or left of the moving scale if the selected value is beyond the range of the scale that is in view. This is similar to the formats used for airspeed and altitude references previously discussed. The area directly under the heading display is used to portray rate of turn as indicated in FIG. 2.

The autopilot-flight director mode annunciator is shown in FIG. 2 in the area designated in FIG. 1. Separate areas are used to annunciate pitch, roll and throttle modes. Each area has capability to display three line legends with each line having up to seven characters.

FIGS. 5A and 5B illustrate two additional formats that are used to display navigation data. FIG. 5A represents status of aircraft position with respect to two VOR stations. The deviation from the VOR beam that has been selected for tracking is shown by the position of the bright triangle with respect to the horizontal line at the bottom of the screen. The open triangles represent 75 and 150 millivolt deviations from the selected course which is typically shown as 281 degrees in FIG. 5A. The data in the three boxes at the left represent bearings and distances to each of two VOR stations and also the true airspeed of the aircraft.

FIG. 5B represents status of aircraft position with respect to a second type of navigation system such as inertial or area. The presentation is similar except that cross track deviation is shown in nautical miles rather than millivolts of beam deviation. The data at the left is consistent with the characteristics of the particular navigation system. The typical example shown reflects area navigation between two way points (identified as EASTA and WILDY). The distance to the next way point is 5.8 nautical miles with an elapsed time to go of 0.7 minutes, based on a ground speed of 478 knots.

Referring back to FIG. 2, the large numerics at the bottom right of the display represents a digital readout of the normal acceleration of the aircraft expressed in units of earth gravity.

An alternate pitch scale presentation is shown in FIGS. 6A-60. In this format the horizon area is expanded to be 26 cells high and the pitch scale is reduced to 8 degrees per three vertical cells. The pitch index is stationary and is located to the left of the pitch scale which moves relative to the index when pitch attitude of the aircraft changes. The indicia of the scale moves downward for pitch attitude changes in a nose up direction and vice versa. The roll indices are similar to those shown in FIG. 3 except that the zero roll index is a straight line rather than the triangle 105. The movement of the horizon line is limited to .+-.20 degrees in order to obtain a presentation of contrasting sky-ground for all combinations of pitch and roll attitudes. This is shown in FIG. 6B. The movement of the pitch scale is continuous and its reading is made with respect to the fixed pitch index. The scale is limited to .+-.90 degrees. If the aircraft maneuvers through 90 degrees, the sky-ground shading will revert to that shown in FIG. 6C where the aircraft has maneuvered past 90 degrees and is starting to fly on its back. The movement of the pitch scale will reverse when the aircraft has maneuvered past .+-.90 degrees of pich attitude.

A second alternate pitch scale presentation is shown in FIGS. 7A and 7B. In this format the horizon area is also expanded to be 26 cells high and the pitch scale is reduced to 8 degrees per three vertical cells. The array of vertical indices previously discussed with reference to FIG. 3 moves for a pitch range of .+-.20 degrees against a fixed pitch scale. When the pitch angle is greater than 20 degrees, the indices will remain stationary at the 20 degree pitch position and the pitch scale will move to correspond. This is illustrated by comparing FIG. 7A with FIG. 7B. In FIG. 7A, the pitch attitude is 15 degrees nose down while in FIG. 7B the pitch att