Aircraft flight instrument display system

We claim:

1. Display apparatus for aircraft for indicating to the pilot the pitch and roll attitude of the aircraft comprising:

(a) means defining a display field of view including a reference index generally in the center of said field and having the general shape of an aircraft and comprising a fuselage portion and wing portions laterally extending therefrom, (b) means for providing a horizon defining line in said field and including means responsive to the pitch and roll attitude of said craft for correspondingly positioning said horizon line relative to said reference index,

(c) means for providing a roll attitude reference scale comprising a zero roll attitude pointer and plurality of roll attitude graduation marks extending in predetermined spaced relation vertically above and below said zero roll attitude pointer for representing predetermined angles of roll attitude of said craft by the position of said horizon defining line relative to said roll graduation marks, said scale being located generally adjacent a wing tip of said reference index, and

(d) means responsive to a predetermined function of the pitch and roll attitude of said craft for moving said zero roll attitude pointer vertically relative to said index wing tip and simultaneously varying the relative spacing between said roll attitude graduation marks, whereby said horizon defining line will be aligned with said roll graduation marks at corresponding pitch and roll attitudes of said aircraft.

2. The display apparatus as set forth in claim 1 wherein said roll attitude graduation marks are short straight lines and wherein said predetermined function of the pitch and roll attitude of said craft maintains said linear roll attitude graduation marks aligned with said horizon line at said corresponding pitch and roll attitudes of said aircraft.

3. The display apparatus as set forth in claim 1 further comprising a pitch attitude reference scale having a zero pitch attitude graduation adjacent said reference index wing tip and a plurality of pitch attitude graduations extending vertically above and below said zero pitch attitude graduation, said zero roll attitude pointer indicating the pitch attitude of the aircraft on said scale.

4. The display apparatus as set forth in claim 1 wherein the fuselage portion of said aircraft reference index has a finite area and further including means for providing a numeric indication of a craft parameter related to pitch attitude within said reference index fuselage area.

5. The display apparatus as set forth in claim 3 further comprising

(a) means for limiting the pitch motion of said horizon defining line for aircraft pitch attitudes greater than a predetermined value to thereby maintain said horizon line within said field of view and for correspondingly limiting the motion of said roll pointer and roll graduations, and

(b) means responsive to pitch attitudes greater than said predetermined value for moving said pitch attitude graduations relative to said reference index wing tip in a direction such that said zero roll attitude pointer indicates the actual pitch attitude of the craft greater than said predetermined value.

6. Display apparatus for aircraft for indicating to the pilot the pitch and roll attitude of the aircraft comprising

(a) means defining a display field of view including a reference index generally in the center of said field and having the general shape of an aircraft comprising a fuselage portion and wing portions laterally extending therefrom,

(b) means for providing a horizon defining line in said field and including means responsive to the pitch and roll attitude of the craft for correspondingly positioning said horizon line relative to said reference index,

(c) means for providing a roll attitude reference scale comprising a plurality of roll attitude graduations extending in predetermined spaced relation vertically in said display field and representing predetermined angles of roll attitude of said craft,

(d) means responsive to a predetermined function of the pitch and roll attitude of the aircraft for moving said roll attitude reference scale vertically relative to said aircraft reference index and simultaneously varying the relative spacing between said graduations,

(e) means providing a pitch attitude reference pointer generally aligned with said aircraft reference index wing tip and a scale of numeric aircraft pitch attitude generally vertically parallel to said roll reference scale, and

(f) means responsive to the pitch attitude of the aircraft for moving said pitch scale relative to said pitch pointer in a direction opposite to the movement of said horizon line.

7. The display apparatus as set forth in claim 6 further includng

(a) means for limiting the pitch motion of said horizon line and correspondingly limiting the pitch motion of said roll scale for aircraft pitch attitudes greater than a predetermined value less than the maximum actual pitch attitude capable of being displayed in said field of view to thereby maintain the position of said horizon line and the position of said roll scale within said field of view for pitch attitudes greater than said predetermined value, and

(b) means responsive to pitch attitudes greater than ninety degrees for reversing the limited horizon line position in said field of view and for maintaining said roll scale at said limited position thereof in said field of view.

8. The display apparatus as set forth in claim 7 wherein the fuselage portion of said aircraft reference index has a finite area and further providing a numeric indication of a flight parameter related to aircraft pitch attitude within said reference index fuselage area.

9. Flight director display apparatus for aircraft for indicating to the pilot the pitch and roll commands required to cause said aircraft to approach and thereafter maintain a desired flight path comprising

(a) means defining a display field and including a reference index generally in the center of said field, said reference index having the general shape of an aircraft including a fuselage portion of finite substantially symmetrical area and a pair of wings extending laterally from said fuselage portion and spaced therefrom,

(b) a flight director symbol comprising right-left pointing triangularly shaped arrowheads and up-down pointing triangularly shaped arrowheads respectively connected by arrow shaft lines, the spacing between the bases of said arrowheads defining a finite area corresponding to the area of said reference index fuselage portion, whereby when said commands are satisfied, said arrowheads project symmetrically beyond said index fuselage portion.

10. Display apparatus for aircraft for indicating to the pilot the progress of aircraft airspeed during take-off and climb comprising

(a) means defining a display field of view including a reference index generally in the center thereof,

(b) a vertically elongated, narrow area within and at one side of said field of view for indicating aircraft airspeed related parameters to the pilot, and having a line defining an edge of said narrow area,

(c) means responsive to craft airspeed for providing a numeric scale movable along one side of said line in accordance with changes in craft airspeed and including a numeric indication of instantaneous airspeed in substantial horizontally fixed alignment with said reference index,

(d) reference airspeed index means corresponding to desired operating airspeeds located on the opposite side of said line, and

(e) means for moving said reference airspeed index means with said numeric scale when the values of said numeric scale correspond to said reference airspeeds.

11. The display apparatus as set forth in claim 10 wherein said reference airspeed index means comprises reference takeoff airspeeds corresponding to decision speed V.sub.1, rotation speed V.sub.R and safety speed V.sub.2.

12. The display apparatus as set forth in claim 11 further comprising

(a) means for obscuring said airspeed scale for airspeeds below said safety speed and for displaying said scale at airspeeds above said safety speed.

13. The display apparatus as set forth in claim 10 further including

(a) means for obscuring said movable airspeed scale in the area occupied by said numeric indication of instantaneous airspeed.

14. Display apparatus for aircraft for providing the pilot with an indication of the rate of climb and dive of the aircraft comprising

(a) means defining a display field of view including a reference index generally at the center thereof,

(b) a vertically elongated narrow area within and at one side of said field of view for indicating to the pilot the rate of climb and dive of the aircraft and having a line defining an edge of said narrow area,

(c) a fixed numeric scale on one side of said line including a zero rate of climb and dive index in substantially horizontal alignment with said reference index and extending thereabove and therebelow a finite distance corresponding to predetermined values of rates of climb and dive respectively,

(d) a movable pointer located on the opposite side of said line and means responsive to craft rate of climb and dive for moving said pointer above and below said zero index respectively and for limiting said motion for rates of climb and dive greater than said predetermined rates, and

(e) a plurality of horizontally short graduation marks vertically disposed adjacent said narrow area and means responsive to said craft rate of climb and dive for moving said marks at a rate corresponding thereto and in directions opposite to the movement of said movable pointer.

15. The display apparatus as set forth in claim 14 further including areas at each end of said rate of climb and dive scale, and means for providing a numeric indication of actual rate of climb and dive of the aircraft for values thereof greater than said predetermined values.

16. The display apparatus as set forth in claim 10 further including means for obscuring said airspeed scale values corresponding to airspeeds greater than maximum operating speed.

17. The display apparatus as set forth in claim 10 further including means for at least partially obscuring said airspeed scale values corresponding to airspeeds less than stall margin speed and greater than flap placard speed.

18. Display apparatus for aircraft for providing the pilot with an indication of altitude and vertical speed of the aircraft comprising

(a) means defining a display field of view including an aircraft reference index generally at the center thereof,

(b) a pair of vertically elongated narrow areas within and at one side of said field of view, one of said areas for indicating to the pilot the altitude progress of the aircraft and the other the vertical speed progress of the aircraft, each narrow area having a line defining an edge thereof,

(c) a movable altitude scale including altitude numerics increasing in value from the bottom of said scale to the top thereof on one side of one of said lines and a fixed index on the opposite side thereof in substantial horizontal alignment with said aircraft reference index and means responsive to the altitude of the aircraft for moving said scale downward for increasing altitudes and vice versa,

(d) a fixed vertical speed scale on one side of the other of said lines including vertical speed numerics increasing in value from a zero index, said zero index being in substantial horizontal alignment with said aircraft reference index and including a vertical speed pointer on the opposite side of said other line and means responsive to the vertical speed of the aircraft for moving said pointer upwardly and downwardly in accordance with upward and downward aircraft vertical speeds, and

(e) a plurality of horizontally short graduation marks vertically disposed adjacent said movable altitude scale and means responsive to said craft vertical speed for moving said graduation marks at a rate corresponding thereto and in a direction opposite to the movement of said altitude scale.

19. Display apparatus for aircraft for providing the pilot with an indication of the wind shear being experienced by the aircraft during an approach to a landing runway comprising,

(a) means defining a display field of view,

(b) a vertically elongated narrow area within said field of view including a vertical line defining an edge thereof,

(c) a fixed numeric scale on one side of said line and representing values of wind speed as a function of aircraft altitude,

(d) a pointer on the opposite side of said line cooperating with said scale, and

(e) means for positioning said pointer relative to said scale in accordance with the difference between the wind speed at the aircraft and the wind speed at the landing runway said difference divided by the instantaneous altitude of the craft above the landing runway.

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 U.S. Pat. No. 4,070,662, entitled "Digital Raster Display Generator for Moving Displays", 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 clutter 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 scale 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;

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

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

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

FIG. 7 comprising 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 symbology 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 or 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 .gamma. which is the well known aircraft flight parameter defined by the difference between the aricraft's pitch attitude .theta. and its angle of attack .alpha.. 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 of 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 interpreted by the relative position of the solid triangle 105 of the array of vertical indices against the pitch scale. The triangle 105 also serves as a zero roll attitude pointer for the roll scale extending above and below it.

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 altitude 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. FIG. 4 illustrates 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 altitude 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 maneuver. 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 position