NASA/CP-2003-2 12 164 

Avionic Pictorial Tunnel-/Pathway-/HighwayIn-The- Sky Workshops 

Russell V. Parrish, Compiler 

Langley Research Center, Hampton. Virginia 

Proceedings of four interactive workshops sponsored by the 

National Aeronautics and Space Administration, Washington, 

D.C., and held at Langley Research Center, Hampton, Virginia 

April 25-27,1994, September 20-22,1994, 

March 21-22,1995, and September 4-5,1996 

National Aeronautics and 

Space Administration 

Langley Research Center 

Hampton, Virginia 2368 1-2 199 

March 2003 
The use of trademarks or names of manufacturers in the report is for accurate reporting and does not 

constitute an official endorsement, either expressed or implied, of such products or manufacturers by the 

National Aeronautics and Space Administration. 

Available from: 

NASA Center for Aerospace Information (CASI) 

7 12 1 Standard Drive 

Hanover, MD 2 1076- 1320 

(301) 621-0390 

National Technical Information Service (NTIS) 

5285 Port Royal Road 

Springfield, VA 22 16 1-2 17 1 

(703) 605-6000 
Avionic Pictorial Tunnel/Pathway/Highway Workshops 

Compiled by Russell V. Parrish 

Foreword 

Beginning in April, 1994, Langley Research Center held a series of interactive workshops 

that met off and on again at about six month intervals through September, 1996, to 

investigate tunnel-, pathway- or highway-in-the-sky concepts. These workshops brought 

together government and industry display designers, test pilots, and airline pilots to 

discuss and fly various pathway-in-the-sky concepts in an iterative manner. 

The first two workshops were focused on the subject of advanced pictorial displays, 

regardless of the specific application. Rapid advances in computer graphics capabilities 

were enabling the consideration of possible new large-screen, integrated pictorial formats 

to provide gains in pilots' situational awareness, pilothehicle performance, and aircraft 

safety, with potential for significant operational benefits. The application of these "realworld", three-dimensional, pictorial displays in the form of "highway-in-the-sky" formats 

had been successful in providing complex-path guidance information to pilots in 

simulated commercial transport operations. These highway formats were being evaluated 

at various flight display research laboratories, including NASA Langley Research Center 

(LaRC). The most prominent feature of these advanced flight displays was the "pathway" 

element (a variation on the Naval Air Development Center "tile" pathway). This type of 

symbology had been shown, in both DoD and NASA research, to enable highly-precise 

flightpath control, especially for vehicles required to execute complex curved flightpaths, 

such as those that may be utilized for landing approaches to closely-spaced parallel 

runways. 

The primary emphasis of these first two workshops was the utility and usability of 

pathways and the pros and cons of the various features available. While the specific 

application was unstated, the prevailing assumption was the pathway would be utilized 

within a Synthetic Vision-like system. Synthetic Vision Systems (SVS) are characterized 

by their ability to represent, in an intuitive manner, the visual information and cues that a 

flight crew would have in daylight -- Visual Meteorological Conditions (VMC). The view 

of the outside world is provided by melding computer generated airport scenes from onboard databases and flight display symbologies, with either information derived from a 

weather penetrating sensor (e.g., information from runway edge detection or object 

detection algorithms) or with actual imagery from such a sensor. The visual information 

and cues are depicted based on precise positioning information relative to the onboard 

terrain database, and includes traffic information from surveillance sources (such as 

TCAS, ASDE, etc.) and other hazard information (such as wind shear). 

In contrast to synthetic vision systems, Enhanced Vision Systems (EVS) attempt to 

improve visual acquisition by enhancing significant components of the real world scene. 

Enhanced vision systems typically use imaging sensors to penetrate weather phenomena 

such as darkness, fog, haze, rain, and/or snow, and the resulting enhanced scene is 

... 

111 
presented on a Head-Up Display (HUD), through which the outside real world may be 

visible. One of the principal problems with EVS applications is the requirement to 

extensively train the pilot to deal with the visual artifacts present in sensor images. 

The second two workshops were focused on the specific application of those pathway 

formats to the external Visibility System (XVS) of the NASA High-speed Research 

(HSR) Flight Deck Systems Program, which was concerned with replacement of the 

forward windows in a High-speed Civil Transport (HSCT) with electronic display media 

and a suite of imaging sensors (Le., an external visibility system). The purpose of the 

XVS was to enable a “No-Droop” configuration of the HSCT. The “No-Droop” mission 

of the XVS was defined as that system which, in a HSCT, would support routine airline 

operations in environmental conditions and at facilities equivalent to current subsonic 

transport capabilities, without the requirement to articulate the forebody geometry for 

ground operations, takeoff, approach and landing. The XVS primary flight display relied 

on a high resolution video camera image of the outside scene, with overlaid symbology. 

The display was somewhat analogous to that of an EVS, except for the lack of a 

collimated HUD. Also, the real world was not visible through the HUD imagery, and the 

sensor image was not from a weather-penetrating sensor, but rather from a visual 

spectrum camera. The purpose of the pathway formats within the XVS display was to 

enable highly-precise flightpath control. 

The primary symbology concerns in the XVS application were the prevention of display 

clutter and the potential for obscuration of hazards, as the camera image in VMC and 

marginal VMC was the primary means of traffic separation. These concerns were not so 

prominent in the first two workshops, which assumed hazard locations would be known 

within the constraints of an SVS (from surveillance sources), and therefore obscuration 

would be handled easily. 

The resulting consensus pathway concept that resulted from the September, 1996 

workshop has been used since in simulation and flight test activities of NASA’s High 

Speed Research (HSR) external Visibility System (XVS), Advanced General Aviation 

Transportation Experiment (AGATE), and the Aviation Safety Synthetic Vision Systems 

programs, and other pathway concepts have been influenced by the workshop discussions. 

Among the direct users of the Langley workshop software are Boeing - Seattle, Boeing 

Helicopter - Philadelphia, the FAA-CAMI, the Research Triangle Institute, WrightPatterson Air Force Base, and Rockwell-Collins. 

iv 
Contents 

1. Foreword ... 

111 

2. Workshop #1 4125-271 1994 

(1) Invitation #1 

(2) Attendees 

(3) Introductory Slides 

(4) Minutes #1 

(5) Steve Williams’ List 

(6) Workshop #2 Suggestions from Dave Hooper 

3. Workshop #2 9120-2211 994 

(1) Invitation #2 

(2) Attendees 

(3) Introductory Slides 

(4) Minutes #2 

(5) Other Notes 

(6) Technical Highlight 

4. Workshop #3 312 1-2211 995 

(1) Summary 

(2) Attendees 

(3) Introductory Slides 

(4) Minutes #3 

(5) 

(6) PFD by Terry Abbott 

Attitude Control Wheel Steering (ACWS) Tuning Investigation 

5. Workshop #4 914-511 996 

(1) Invitation #4 

(2) Invitees 

(3) Attendees 

(4) Slides 

(5) Minutes #4 

(6) Minimum XVS Symbology Set by Steve Williams 

(7) Surface Operations Symbology Issues 

(8) Pathway Issues 

(9) Guidancemight Path Vector Discussion 

( 1O)Declutter Discussion 

(1 1)Minimum Symbology Set Modifications by Randy Bailey 

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6. Concluding Remarks 

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Workshop ## 1 

April 2527,1994 

Invitation to Workshop # 1 

The Cockpit Technology Branch, Flight Dynamics and Control Division at NASA 

Langley Research Center is sponsoring a Pathway-Based Flight Displays Interactive 

Workshop on April 25-27, 1994 in Hampton, VA. The purpose of the workshop is to 

gain a better understanding of synthetic vision pathway displays & symbologies by having 

the subjects participate in an interactive workshop environment. The subjects will fly 

several pathway concepts for a generic approach task and make suggestions that may be 

iteratively implemented. During the iterative programming efforts, other display issues 

will be discussed, such as High Speed Civil Transport (HSCT) display real-estate usage 

and other flight phase displays (cruise, surface operations, etc.). Several pathway concepts 

will be available as a starting point, including various goalpost, roadway, and tunnel 

concepts. 

Attendees 

Terry Abbott 

Tony Busquets 

Gordon Hardy 

Randy Harris 

Dave Hooper 

Patricia Hunt 

Walt Johnson 

Simon Lawrence 

Paul Leckman 

Dean Nold 

Mike Norman 

Russ Parrish 

Dave Regal 

NASA LaRC 

NASA LaRC 

NASA ARC 

NASA LaRC 

American Airlines 

NASA LaRC 

NASA ARC 

US Air 

Boeing 

NASA LaRC 

McDonnel Douglas 

NASA LaRC 

Boeing 

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7 
Pathway Workshop ## 1 Minutes & Discussion Items 

R. Michael Norman 

McDonnell Douglas Aerospace 

April 25-27, 1994 

1. One topic of focus for the discussions was the need for pathway information, and the 

definition of a pathway. A pathway gives status information concerning the present, 

planned, or expected flight path. 

2. Navigation Display (ND), and Primary Flight Display (PFD) information will probably 

be integrated in the primary Forward Visibility System display (FVSD). ND and PFD 

display elements should be reviewed to ensure that no loss of data sources occurs in 

integrating the data. 

3. The methodology for integration of imagery in the display must also be considered, 

and may alter other display elements. 

4. Several methods of declutter have been used previously, including physical separation 

selectable declutter, color, contrast, brightness, and depth separation in 3- 

dimensional displays. 

5. There are two primary reasons to declutter displays - to reduce information saturation, 

and to reduce crowded areas of display to permit faster identification of critical 

display information. Declutter requirements may change with display scaling, 

physical size and field of view, and the presence of sensor imagery. 

6. There may be a need, in presenting pathways, of distinguishing cleared flight paths 

from expected flight paths. 

7. Several initial types of flight path “tunnels” were reviewed. The Dorighi Tunnel is 

defined by four dotted lines at the edge of an acceptable error box, with square 

guidance symbols inside the dotted lines, and a reference solid box at a fixed time 

reference ahead of the aircraft. The “Noodle Tunnel” is defined by a series of boxes, 

leading from the present aircraft position to a reference position on the cleared path, 

or final approach fix. The NASA Langley Goal Post Tunnel is defined by partial 

boxes consisting of side and bottom segments, center pillars extending from the 

bottom of the boxes to the terrain floor, and rectangular tiles inside the boxes 

defining the path to be flown. 

8. Two primary types of guidance were discussed - standard flight director, and pursuit 

guidance. The standard flight director, as it is generally implemented, has a limited 

field of motion within the display, and provides some amount of lead steering in 

returning to a desired flight path following errors. Pursuit guidance, as implemented 

by NASA Ames, is represented by a “ghost aircraft,” flying a fixed time interval 

ahead of own aircraft, on the desired flight path. Superimposing a velocity vector on 

8 
a reference mark on the ghost aircraft, then, provides pursuit guidance to the desired 

flight path, resulting in an exponential decrease in flight path error with time. The 

ghost aircraft is allowed to move throughout the display, with consideration for 

display element priority and pegging of guidance cues. 

9. The need for color standardization was discussed, keeping in mind that both PFD and 

ND information would likely be combined on the FVSD. 

10. The need for conformality was addressed. Conformality is defined as the property of a 

display wherein display element movement has a one-to-one correlation with the 

outside world, both in scale and position. Lines drawn from the pilot’s eye to display 

features, if extended outside the aircraft, would then intersect the corresponding real 

world features. Conformality has been shown to be useful in direct view displays 

(Head-Up Displays, for example), but is generally not a feature of standard 

instrument displays. Concerns were expressed for the interaction between the FVSD 

and the side windows if the FVSD was not conformal, particularly during the flare. 

This item needs further simulation and study to resolve. 

1 1. Error gains (the amount of display scaled displacement for a given error) will likely 

have to be tuned for a specific set of handling qualities for an aircraft. Since 

significant changes in flying qualities will occur with changes in altitude, speed, 

aircraft configuration, and flight control mode, error gains will have to be tuned for 

all of these considerations in the HSCT. 

12. After initial evaluation by all of the pilots present, the consensus was that the “Noodle 

Tunnel” had little to no merit for the HSCT application, and was evaluated further. 

Since the beginning of the tunnel was always tied, laterally and vertically, to own 

aircraft position, this tunnel provided no cues to path error, merely showing a route 

back to the desired path. 

13. Several of the pilots objected to the amount of clutter in the Langley Goal Post 

Tunnel, particularly early in the approach, where numerous goal posts could be seen. 

14. It was generally agreed that the edges of the tunnel should correspond to the allowable 

error tolerance in flight path control. Some method for discerning desired error 

tolerance should also be provided. 

15. One problem with pursuit guidance was discussed, in that during turns, this guidance 

will lead to flying to the inside of the turn, or cutting the comers. Two solutions to 

this problem were addressed deliberately positioning the ghost aircraft to the 

outside of the turn by a programmed amount, or providing a second order correction 

to the position of the velocity vector on the display during turns. The latter method 

has the advantage of also providing a more accurate prediction of aircraft future 

position in turns, at the expense of a somewhat more active display cue, unless 

damping is included. 

9 
16. Critical guidance symbology, such as the velocity vector or the pursuit aircraft cue, 

should never be allowed to disappear off the edge of the display. Some method 

should be provided to indicate the extrapolated position of the cue, as well as the fact 

that the cue has pegged on the display. Methods which could be used include 

freezing the cue at the proper position on the display ( in a line to the actual 

position), flashing the cue, changing colors, hiding half or a part of the cue, or 

dotting the display lines constituting the cue. The method used for this study was to 

change the cue color to red. 

17. Initially, the flight director cue changed from the pursuit aircraft to circular flight 

director cue at 200 ft AGL. This change in symbology near to touchdown proved 

distracting, and the cue appearance was changed so that it remained as a “ghost 

aircraft” throughout the flare and touchdown. NASA Ames reported successful use 

of a shadow cue oriented around the ghost aircraft in the flare. We were not 

successful in this workshop, however, in implementing the shadow cue in any 

acceptable manner, as attempts resulted in a distracting, cluttered flare cue. 

18. The speed and acceleration cues implemented earlier by NASA Langley were well 

liked, and have been used successfully in other displays. NASA Ames reported that 

these types of cues provide an excellent early indication of impending windshear 

events, in instances where the acceleration and speed error cues move in opposite 

directions. 

19. Discussions occurred on how to differentiate the runway cleared to on the pathway, in 

airports where multiple runways must be presented. One method mentioned was to 

outline the runway graphics with a highlight cue (purple, in the case of the workshop 

software). This highlight cue could also be used to indicate to the pilot that sensor 

position correlation had occurred, providing an added degree of confidence in 

displayed runway position. 

20. Discussions occurred on the philosophy of manual or automatic landing modes as the 

primary method used. Difficulties may arise in pilot proficiency if automatic modes 

are considered primary, with manual pilot backup. In a reliable system, pilots could 

go for years, never having made a manual landing, and then suddenly being required 

to take control in an anomalous situation. It was suggested that a baseline assumption 

should be that the aircraft systems should be certified in all conditions for either 

manual or automatic landing modes, leaving the policy of when to use either mode to 

the customer. Even in manual modes, of course, it is likely that a significant amount 

of flight control augmentation will be provided. 

2 1. During automatic ILS-guided landings in VMC conditions, concern was expressed 

regarding beam protection. During VMC conditions, ATC is not required to provide 

the same level of ILS beam protection (through aircraft separation) normally 

provided in instrument conditions. In present transport aircraft, crews can see other 

aircraft on or above the airport, which might contaminate the beam during 

10 
approaches in these conditions, and anticipate the need to take over manually, should 

beam deviations become severe. Some corollary to this information source, normally 

gained through forward facing cockpit windows, should be provided. 

22. It was reiterated that, with the absence of direct forward views of the runway or 

airport, navigation and display systems accuracy and integrity are critical to flight 

safety, and must be assured and protected. 

23. It was suggested that the presence of pathway display elements should be selectable 

by the pilot, so that information saturated displays could be decluttered when 

workload becomes high. Path error information should, of course, always be 

available in some form. 

24. Concern was expressed that, since a pictorial forward display would replace the 

traditional PFD, it must be an all-attitude (spherically unconstrained) display. 

Provisions should exist to aid the pilot in unusual attitude recovery. 

25. Two types of information should be provided on the forward display - pathway or 

position error (three or four dimensional), and flight guidance cues. The guidance 

cues should be simple enough that in high workload situations, the pilot is guided 

quickly on where to position the aircraft attitude and thrust (as applicable). Pathway 

or position error cues should be easily interpretable, and ideally should provide 

desired, as well as allowable, tolerances in the display element. Initially, traditional 

crosshairs were provided around the velocity vector to indicate desired path error 

limits. Later, these were replaced by a dotted box that was positioned in relation to 

the velocity vector so as to indicate lateral and vertical path error. The dotted box 

was preferred over the crosshairs, in that it decluttered the critical area immediately 

around the velocity vector, and was more easily interpreted than the crosshairs. Some 

pilots, however, still wanted analog error scales (similar to ILS raw data indicators) 

at the edge and bottom of the display. An additional digital display, indicating path 

error in equivalent “dots”, was provided adjacent to the analog scales, which some of 

the pilots felt was a valuable addition to the display element. Concern was expressed, 

however, that these scales would interfere with altitude and/or velocity tapes on the 

display, particularly in high crosswinds. Further study is warranted to reduce the size 

of the analog scales, and move them to a location where they will not interfere with 

other display elements. It was also suggested that the scales and error box should be 

individually selectable by the pilot, as desired. 

26. The question of whether or not cross training to and from other aircraft should be 

considered was discussed. The advantage of emphasizing cross training issues in the 

design is ease in pilot transition to and from other types of aircraft. The disadvantage 

is possible compromise of an unconventional but effective design strategy, in favor 

of a more conventional but less effective one, to reduce training impact. Of note, this 

issue was not a driving one, apparently, on the Concorde aircraft, and pilots 

transitioning to that aircraft typically remain there for the remainder of their careers. 

11 
27. 

28. 

The issue of velocity centered, vs. attitude centered, displays was discussed. In a 

conventional (attitude centered) aircraft display, the aircraft waterline, or reference 

mark is fixed on the display, and the velocity vector moves on the display in response 

to inertial velocity vector changes. In a velocity centered display, the aircraft velocity 

vector is fixed on the display, and the attitude reference allowed to move in response 

to velocity vector changes. Research has been conducted which suggests some 

benefits to the velocity centered display, particularly in high or gusting crosswinds. 

Some concern was expressed about pilot disorientation in the velocity centered 

display, since it is necessarily not a conformal display in crosswinds. Further study, 

both in simulation and in flight tests, is warranted to investigate the suitability in 

each strategy, velocity and attitude centered, for the HSCT mission. 

A discussion occurred on whether or not to provide a pathway display element during 

constant heading flight modes, or during cruise modes in general. This evolved into a 

discussion, again, on what constitutes a pathway. The consensus among the group 

was that a pathway is defined three dimensional line in space, consisting of curved 

and/or straight segments, over fixed earth-referenced coordinates. Pathways could 

also have a time critical dimension associated with them, during 4-D clearances. This 

definition is consistent with what is presented on FMS map displays in current 

aircraft. Constant heading modes may not fit this definition, (excepting vectors away 

from or toward a defined path). It was suggested that pathways not routinely be 

displayed in constant heading modes, then, due to difficulties in display or 

interpretation of lateral flight path errors. It was also suggested that pathways, in 

general, be a pilot selectable display element, so that they could be removed in 

situations where they would be confusing, or clutter the display. 

29. The issue of how to display a two dimensionally constrained pathway was discussed. 

This situation would occur, for example, during climb or cruise/climb. Here a cleared 

route over the ground would exist, along with an expected altitude at the end of the 

segment, but no specifically cleared vertical path would exist to get there (though a 

planned profile would be continuously computed). It would not be appropriate to 

display a three dimensional pathway here, since following minor vertical path errors, 

the pilot would not be expected to return to the previously computed optimum 

performance path, and a new optimum performance path would continuously be 

computed. The distinction between path and guidance information should be stressed 

here - the pathway does not indicate how the pilot should reduce path errors 

(guidance cues do that), it merely displays those errors. It was suggested that when 

pathways are laterally, but not vertically constrained, the displayed vertical error 

should be zeroed at all times. The pilot, then, could fly laterally off the path, but 

never above or below it. The practicality or useability of this display philosophy 

remains to be demonstrated. 

30. Additional note was made of the facts that the HSCT will probably not be in level 

cruise as much as subsonic aircraft (HSCT expected benefits of cruise/climb modes 

12 
are more significant), and that cruise clearances will likely involve tight lateral 

tolerances, due to sonic boom constrai,nts. Two dimensionally constrained paths, 

then, must be considered when developing display modes and formats. 

3 1. Concern was expressed that these 2-D constrained paths may have to be altered 

quickly during unplanned configuration or performance changes, as in an engine 

failure following takeoff, or early flap extension or retraction. The effects of these 

rapid display changes should be investigated in conjunction with display 

development . 

32. The idea was suggested that navigational waypoints could be displayed as three 

dimensional objects on the display. This idea was implemented on the LaRC Visual 

Imaging Simulator for Transport Aircraft Systems (VISTAS). 

33. A discussion occurred concerning the difference between guidance and pathway 

information. It is entirely conceivable that guidance cues may lead the pilot away 

from the pathway, as in a brief vector off course, for instance. One suggested 

philosophy was that a pathway be displayed when a route segment has been entered 

or computed in navigational planning systems (as in an FMS route in today’s 

systems). 

34. The display of four dimensional pathways (those which include time constraints) will 

probably require both status and guidance display elements relating temporal errors. 

Two predominate philosophies exist relating to time constraint guidance - speed 

control, and volume clearance. In the speed control philosophy, speed commands are 

issued to conventional display elements (command airspeed or airspeed error) to 

keep the aircraft in the center of an allowable time error band. This philosophy 

suffers the disadvantage of demanding too tight a control in some occasions, at the 

expense of reduced performance. Another method suggested was the space volume 

clearance method. In this philosophy, there is a volume of space which moves with 

the aircraft that represents the edges of allowable error tolerance (how far the aircraft 

can deviate from optimum and still make required time constraints at a reference 

waypoint with acceptable speed adjustments). The volume clearance philosophy, it 

was reported, allows more flexibility in speed control, and may result in greater fuel 

efficiency. Guidance cues could consist of changes in perspective distance with 

respect to a pursuit aircraft, or color changes on a pathway. Further study is 

warranted to develop appropriate cues for four dimensional status and guidance 

display elements. Of note, these may be difficult when the desired clearance volume 

is behind the aircraft. 

35. The idea was expressed that pathway information displayed on a pictorial forward 

display should be redundant with respect to information displayed on other 

navigational displays (the ND, for example). Pilots should use ND’s it was 

suggested, primarily for flight planning, path verification, and vertical path 

perspectives. The pilot should not have to refer to an ND for guidance to a path, or a 

13 
path error status. Discussions suggested that in addition to route or navigational data, 

terrain clearance, terrain presence, and weather information are other information 

categories that should be redundant. 

36. A discussion occurred concerning the requirement for three dimensional weather 

depiction on a pictorial forward display. Questions arose on weather or not the pilot 

needs vertical cell location on this type of display. The consensus appeared to be that 

the pilot does need this information, both in JMC and VMC conditions, to aid in 

guidance over storm cells or systems. 

37. It was suggested that, in addition to a perspective oriented pictorial display, and a 

horizontally oriented navigational display, the need exists for a vertically oriented 

profile display. This display would present a side view of the aircraft and flight path, 

and would show vertical position and deviation from a reference. 

38. The need to show missed approach information on the forward pictorial display was 

discussed. During approaches, the pilot will need this information, both to help plan 

for flight path requirements, and to visualize the projected flight path with respect to 

terrain, other waypoints, airport references, etc., in the event of a missed approach. 

39. The possibility of embedded flight training was discussed. Embedded flight training is 

training which can occur during a flight, ostensibly during extended cruise segments, 

where a portion of the aircraft systems acts as part task flight simulator, to train pilots 

on systems, procedures, or maneuvers. This idea is popular in advanced military 

aircraft. Further analysis and trade studies are warranted. 

40. Clutter was emphasized as an important issue in forward pictorial displays. It was also 

emphasized that clutter may have a different meaning in a display wherein elements 

are intended to replace outside world cues. Clutter, for example, may lead to 

information saturation in portions of a display, if not properly considered. Clutter 

should never, however, lead to deliberate obscuration of critical information 

components of a display, as contrast, brightness, or occultation are legitimate tools 

available to prevent this. Pixelation and display resolution are parameters mentioned 

which may affect pilot perception of clutter. 

41. It was mentioned that the VISTAS display resolution is 1.5 arc minutes - essentially 

equivalent to human 20/20 vision. Questions were raised whether or not this 

resolution is reasonable in displays of the type and vintage under consideration, 

including the time required to convert prototypes to flight ready systems. 

42. It was noted that requirement for forward visibility systems might be considerably 

different in VMC than in IMC. VMC is probably the more technologically 

demanding of the two, and should probably be addressed first, it was suggested. 

14 
43. Problems with displays during taxi were discussed. It was mentioned that present 

technology would allow detection and tracking of surface vehicles and people 

through the use of Airport Surface Detection Equipment. Relatively inexpensive (75 

cents was quoted) tags would allow objects to be tracked, and data linked, to aircraft 

operating on or near the airport. Significant objects could then be displayed 

appropriately in the cockpit. Problems of animals on taxiways, or snow banks in the 

Winter, were additional items mentioned which will have to be addressed. 

44. The need was discussed to ensure that space is left on the forward pictorial display to 

present engine, and other systems information. It was mentioned that perhaps an 

auxiliary display could be provided to indicate this information, adjacent to the main 

display, and shared between the crew. A list of information requirements, to be 

presented on each type of cockpit display, is needed. 

45. The need for color standardization in display elements was discussed. Cleared flight 

paths, for example, are traditionally displayed in magneta on FMS map displays, and 

should probably be displayed in that color on pictorial displays. Proposed, or 

alternate flight paths could be displayed in white, using lack of brightness, dotted 

lines, or suppressed resolution to distinguish them as planned paths, on pictorial 

displays. 

46. The problem of indicating cleared, vs. planned, altitudes, was mentioned. For 

example, a descent route segment may begin at Flight Level 350, end at 5000 feet 

MSL, but the aircraft is only presently cleared 15,000 feet MSL. One method 

suggested of indicating this in path data was to present a pseudo cloud deck, or 

translucent tiles, at the cleared altitude on the display. Further study is warranted to 

arrive at an acceptable method of display. 

47. The issue of what types of altitude and airspeed situational awareness information to 

display was mentioned. Classic types of display elements include tapes, digits, 

rolling digits, and analog dials. Keeping in mind that the primary purpose of these 

display elements is situational awareness only, studies are warranted to arrive at an 

acceptable means of presenting these display elements. 

48. Additional capabilities or features were requesting in the VISTAS display which were 

not incorporated yet. They included a full takeoff, climb, cruise, descent, approach, 

and landing profile, the ability to alter landing gear and flap/slat configuration, 

functioning rudder pedals, and an HSCT representative aero model (see Steve's List 

below). 

49. It was suggested by NASA representatives that the uniqueness in capability of the 

group, and the value of the issues raised to high speed research significant enough, 

that the FVS workshop should not be limited to just one session. It was suggested 

that the group meet again in September, 1994, for further refinement of issues and 

candidate solutions to problems raised. 

15 
Steve Williams' List 

Steve. 

Even though I know how you use/don't use lists, here is mine on what remains to be done 

for the Sept. workshop: 

1. Rudder software fix 

2. Retiming the taxi -- hold-short aircraft 

3. Retiming the traffic to the other runway 

4. Reworking the xdothhrottle equation & autopilot closure loop 

5. Calculating airspeed/altitude relation 

6. Flare command localizer transition 

7. Flare command gamma tuning 

8. Missed Approach Path * 

9. 4-D concepts (wing span, tunnel color shading, etc.) 

10. Soft Path concepts 

1 1. Multiple paths (cleared vs. expected - example is "expect direct from waypoint 

alpha to waypoint bravo") 

12. Turning wind off after weight on wheels signal 

Russ Parrish 

* Mike Norman says that the FMS guidance for most airports has a missed approach fix 

about .5 Nmi from the runway end on the centerline at a certain altitude (say 1100 ft 

AGL) from which you are to begin a standard rate turn to the reentry waypoint track. 

How about a STAR for the workshop similar to the attached figure ? 

16 
Dave Hooper’s Suggestions for the Sept. workshop Sept9,1994 

Symbolic colors 

Although we have, thus far, succeeded in decluttering the display area I still feel a need to 

assign various color attributes to specific symbols. The following is my initial list of 

suggested color assignments: 

Approach Window Yellow 

Flight Path Vector Ind Magenta 

Pursuit Aircraft White 

Indicated Airspeed Tape White 

Radio Altimeter White 

Roll Scale White 

Aircraft Reference White 

Pathway Tunnel Green 

Goal Posts Green 

Pitch Scale White 

Horizon & Heading Scale White 

Actual Heading White 

Selected Heading Green 

Fast / Slow Indicator White until +\- 10 kts then flashing 

yellow 

Wind Vector 

I would like to see the wind vector and speed indicator moved from the ND to the PFD in 

the top right corner as it is displayed in the original Flight Dynamics HUD. VS / GS / IAS 

Some of my photos of the past workshop show indications of IAS over GS on the left and 

MSL over RA with VS below , on the lower right side of the PFD. Other photos show 

this data removed. I think this data is needed and a discussion concerning the position and 

amount of information would prove beneficial. 

Glide Path Angle 

I would like to see a printout of my current glide path angle ie. 3 degree to match a 

3degree glide slope. 

Touchdown Point 

I might like to see either a graphic profile or digital readout of where I will touchdown on 

the runway with reference to my flight path vector. This would be in relation to the 

desired touchdown point. 

Pursuit Aircraft 

This summer Walt Johnson was able to provide me with an opportunity to fly the Vertical 

Motion Simulator with the HSCT mockup. Every time I performed a go- around, the 

17 
Pursuit Aircraft would disappear and I would be left flying raw data. This is workable, 

however the transition to raw data was abrupt and not desirable. This transition was 

probably due to the computer program. I suspect that the go-around routines had not been 

written yet. I would simply like to be assured that the pursuit aircraft will eventually be a 

full time display. This should also include a readout of the mode which the pursuit 

aircraft is currently operating. ie. Approach, go-around, cruise, climb, descent, vertical 

nav climb/descent, VS, windshear escape, engine out go- around, etc. The pilot needs to 

know where the pursuit is taking him, and why. 

Approach 

I think that we need to discuss when the approach mode will begin and end. Once this is 

done we can decide what symbols need to be displayed on the PFD. ie. goal posts, 

approach window, CDI information, radio altimeter, etc. 

Visual Cues 

In the real world I receive visual cues which alert me to the actual flying conditions. For 

example, I might see black clouds, lighting, virga, and heavy rain. These cues would alert 

me to the possibility of microburst activity and thus I would be mentally alert for this type 

of flying. On another day I might see blue sky, sun, and have a visibility of 60 miles. With 

these cues I would be more relaxed and more concerned with VFX traffic than microburst 

activity or thunderstorms. During one of my approaches in the VMS I was presented with 

microburst activity on short final. I was told that this would occur, so I was ready for it, 

yet something bothered me about this scenario. It wasn't until I returned home and began 

to ponder this question that I discovered that I was missing the visual cues of microburst 

activity. The synthetic vision was that of a great day with blue skys and no weather. My 

visual cues told me that there was not much to worry about. They said, "take it easy and 

concentrate on making a good landing." The only cue I was provided with was when they 

told me that I was going to encounter a microburst. That won't always be the case. Sure 1 

will have the side windows, weather radar, and hopefully some type of terminal doppler 

weather radar, but will that make up for the loss of real time visual cues that we 

unconsciously rely upon today? I don't mean to insinuate that I must be provided with an 

advanced warning of a pending situation in order to be able to fly safely. Pilots have a 

long history of adapting to rapidly changing conditions. This is one of our specialties. 

However, by providing us with visual cues of one situation while we are actually 

encountering totally different actual conditions is very misleading and unnatural. I would 

like to have an open conversation concerning this loss of visual cues. 

Track vs. Heading 

I once was a believer in the "heading up" concept. Then I flew the B-767. Now I am a true 

believer of the "track up" concept. Yes, I need to know what my heading is, but as far as 

navigation is concerned, I need to know my track. We need to discuss this concept and 

begin to evolve a direction. 

18 
CDI 

I like the Approach Window, or ILS Box, concept. However, when we strayed off course 

far enough, and it will happen, the window slid completely off the screen leaving us with 

no direction back to the final course. Then we added course deviation indicators which 

included a great idea from Steve Williams ( I think ). He added a display of the number of 

degrees you are away from the localizer or glide slope. This addition was great because 

you could easily determine if your current heading was bringing you back to your desired 

course/path, or not. The CDI's do, unfortunately, create clutter. So I would like to propose 

that the CDI information only be displayed when you are so far away from the desired 

path that the approach window is no longer in view. 

Roll Scale 

If the Roll Scale only displays bank information up to a max of 30 degrees, then how will 

we practice 45 degree bank turns? Why not present a digital readout of all banks in excess 

of 30 degrees? 

HDTV 

As you know there are going to be many problems created with no forward looking 

windows. Could we have additional discussions concerning a full time HDTV display. If 

we are going to discuss cockpit real estate, we will need to save room for this display. 

Nav Display 

The ND must have some type of taxi display similar to the TEEM (Taxi Evaluation 

Electronic Map) display. The ND will also have to display radar information 

superimposed over our route. I would also like to see the ND used in the "track up" mode 

with a heading line from the aircraft symbol to the selected heading, like the B- 767. 

Vertical Navigation 

This area of display and programming needs to be discussed. 

19 
Workshop # 2 

September 20 - 22,1994 

Invitation to Workshop # 2 

We are planning our second interactive workshop on pathway displays for Sept. 20 - 22, 

1994. We again anticipate beginning at SAM on the Tuesday and winding up about midday on the Thursday. 

concepts and to have all participants make suggestions, which we will try to implement 

"then and there" so they could iteratively help us arrive at a better understanding of 

synthetic vision pathway displays & symbologies. While Steve Williams is programming 

away, we would be discussing other display issues, such as HSCT display real estate 

usage, other flight phase displays (cruise, surface ops), etc. We intend to have the 

following available as starting points: velocity-centered vs. attitude-centered displays, 

multiple-displayed pathways (approach & missed approach, cleared & expected), soft 

pathway concepts (unspecified in at least one spatial dimension), 4-D pathway concepts, 

flight phase transitions (cruise to descent, etc.), other flight phases (takeoff, cruise, etc.). 

We have invited the following participants: 

The idea is to have the participating pilots fly several pathway 

PATHWAY WORKSHOP INVITEES 

PILOTS 

BOEING 

Paul Leckman 

AMERICAN AIRLINES 

David Hooper 

HUGHES & DELTA AIRLINES 

Bob Blanchard 

NASA AMES 

Gordon Hardy 

RESEARCHERS 

BOEING 

David Regal 

HSR FVS Representative 

HONEYWELL 

HSR FVS Representative 

DOUGLAS 

Mike Norman 

U. S. AIR 

Simon Lawrence 

FAA 

TBD 

NASA LANGLEY 

Lee Person 

NASA AMES 

Walt Johnson 

20 
HUGHES 

Sam Holl i ngsw orth 

NASA LANGLEY 

Terry Abbott 

Anthony Busquets 

Dale Dunford 

Patricia Hunt 

Randy Harris 

Dean Nold 

Russ Parrish 

Steve Williams 

As you see, we are inviting more HSR FVS representatives this time, as our fears that too 

many participants meant too many cooks in the kitchen proved unfounded last time. We 

invited only known pathway researchers, rather than any folks with those interests. 

Anyway, I hope you can come. Let me know if there are any problems. 

Regards, 

Russ 

PATHWAY WORKSHOP ATTENDEES 

PILOTS 

BOEING 

Paul Leckman 

AMERICAN AIRLINES 

David Hooper 

HUGHES & DELTA AIRLINES 

Bob Blanchard 

NASA AMES 

Gordon Hardy 

RESEARCHERS 

BOEING 

David Regal 

Brian DeLuca 

DOUGLAS 

Mike Norman 

U. S. AIR 

Simon Lawrence 

FAA 

Berk Greene 

George Lyddane 

NASA LANGLEY 

Lee Person 

NASA AMES 

Mary Kaiser 

Charlie Hynes 

Dick Bray 

21 
HONEYWELL 

Mike Johnson 

HUGHES 

Sam Hollingsworth 

NASA LANGLEY 

Terry Abbott 

Anthony Busquets 

Dale Dunford 

Patricia Hunt 

Randy Harris 

Dean Nold 

Russ Parrish 

Steve Williams 

22 

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Tom Sharp 

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31 
Minutes from Workshop #2 

Russ, 

The following is a set of observations and comments regarding the workshop. But first, 

let me add that, at the risk of adding to the number of future workshop participants, I 

gave the workshop very favorable reports here at Honeywell. 

Thanks again for the opportunity and the privilege of allowing us to participate. You and 

your staff put together an excellent forum for technical interchange, useful in general and 

especially useful for the upcoming HSR flight deck effort. 

Sincerely, 

Mike Johnson 

Side windows 

Many at the workshop seemed to feel that there would be no substantial operational 

difficulty incurred, if the side windows were eliminated from the HSCT cockpit. If the 

side windows were eliminated, many more candidate display technologies would 

become available. Only a few merit serious attention now. The maximum levels 

expected in ambient light and the sunlight shafting constrain us to just two or three high 

brightness technology paths. No side windows imply relief on high brightness 

requirements and on tough conformality requirements. Clearly, the presence or absence 

of side windows is of primary importance. 

At the HSR quarterly meeting in Seattle this year (94), there was considerable sentiment 

evident that side windows should be retained as part of the baseline configuration. The 

rationale appeared to rest on two facts: 1) Some believe the side windows offer a 

significant if not high degree of utility and function not yet fully understood or 

characterized; and 2) Side windows present no major cost impediment to building a cost 

effective HSCT structure. 

If the side windows were to be ultimately retained, it may be possible to limit the levels of 

ambient light and the sunlight shafting that come through. Overlaying the windows with 

a light valve or micro-louver or equivalent technology might suffice. Efforts in these 

areas have been recorded and indicate such approaches are feasible, depending on more 

detailed requirements specific to each application. 

Risk assessment of the Pathway and Ghost Aircraft Format 

This entry is to note that, from the standpoint of a display systems designer, pathway 

formats are low risk. Computational and storage requirements are modest. And, as noted 

by several at the workshop, precedents by similarity exist. 

32 
The HGS made by FDI does provide support for probable certifiability of pathway 

formats. The HGS portrays a simple 4 point perspective runway rendering that uses the 

same raw data the pathway uses. The principal difference is that the trend information is 

not calculated and shown in an HGS, although the raw data to do so is present. Similarity 

of pathway formats we observed in the workshop to existing PFD formats (a point that 

Dave Regal made) provides additional support. 

The distinction between terrain database rendering and pathway rendering made by Dave 

Regal, Mary Kaiser, Brian DeLuca and others, is re-iterated here as being technically 

correct, at least as seen from the standpoint of a display systems designer. After the trend 

data are calculated from the raw aircraft state variable data, the fundamental problem is 

one of transforming world referenced coordinates to screen referenced coordinates. The 

PFD, the HGS and the NAV display formats are rendered from this type of calculation. I 

estimated there were about one thousand 3D vectors displayed on the pathway formats. 

The HGS shows two vectors. Although about three orders of magnitude more processing 

are needed, the types of calculations required are within the realms of current single 

processor capability. The amount of database storage needed is the same as is required 

for the HGS, which is negligible. A table showing changes in database and processor 

throughput requirements could be constructed to show detailed and objective 

comparisons. 

Object detection and display resolution 

If object detection by machine is equal to or better than object detection done by the 

human , then it may be possible to reduce resolution requirements on the HSCT forward 

display system. It may be acceptable to instate a lower than ideal display system that 

compromises 20120 visual acuity (among other visual attributes). The machine may be 

used to annunciate the region(s) of interest. Then, the human operator might acknowledge 

the alert by directing the forward vision system to zoom in and magnify the area of 

interest so the human can identify the object and the level of threat. One TV (or HDTV 

or UHDTV) sensor may be gimbaled with respect to a matrix of panoramic and stationary 

sensors to acquire the area of interest and magnify it. 

What is missing is the definition the "object" in the physical and operational HSCT 

context. For example, is an object always made of metal or at least highly reflective and 

of sufficient contrast in the radar spectrum? Or is it a contrast divot in the visual 

spectrum and, if so, is it in need of comparison with known objects in the geographic area 

and catalogued in a detailed database? Definition of the term object must be made in 

terms of the physics (wavelength of the sensor, dynamics, reflectivity, transmissibility, 

signal to noise ratio, range of viewing conditions, ... ) and in terms of human 

psychophysics (current level of object detection) and in terms of probability of success 

and false alarm and ease of control. Much of this is the subject of basic research in the 

physical and the psychophysical domains. 

My own feeling is that object detection by machine will aid human vision substantially 

but may not reach the level of performance necessary within the timeframe of the ''no 

33 
droop" decision to warrant reduction of display resolution requirements. Early 

assessments of probability of success in this area are imperative. 

Competition between symbology and background video 

Haloing, a thin black border encircling all the high priority symbology, is designed to 

allow primary symbols to be easily discerned, regardless of the intensity of the surround. 

Easy discrimination of symbology will become especially important when the pathway is 

overlaid on a field of video. Video presents a wide range of intensity and color patterns 

making a priori color and intensity selections of the pathway symbols difficult to do 

unless an occlusion method is used. Steve Williams implemented haloing on formats 

shown the last day of the workshop. Video or a reasonable facsimile of it (perhaps 

photographically texture mapped terrain) is needed in future pathways workshops to 

adequately assess how the pathway will interact with the primary VMC sensor. 

Mary Kaiser suggested in a side discussion that we identify ways of eliminating or 

reducing the risk of obscuring objects that might otherwise lie hidden beneath the 

overlaying symbology. That this is an area of legitimate concern is underscored by a 

story Mike Norman told at the HSR quarterly meeting last April. He stated that, on an 

approach during SVS flight tests, a truck parked on the runway lay unseen, hidden by a 

single vector displayed on the HUD, for an appreciable portion of the approach. Under 

actual VFRNMC situations, flying in this mode could be a real problem. 

We might rely on machine vision object detection to annunciate areas of risk, enabling 

the pilotlcopilot to determine how they want the symbology to be displayed. This concept 

may, however, mandate the presence of a detailed database that includes an inventory of 

known objects. Hidden object display options might appear in a selection menu the 

viewer uses to choose how he/she wants the symbology and the object to be displayed. 

Mary proposed that an additive or translucent method of annunciating the symbology be 

explored so as to test for ways of minimizing the obscuration of objects residing beneath 

symbols. Experiments that I did in this area some time ago showed that the underlying 

video and the symbol interfered with each other and both became difficult to "read". 

These experiments were informally executed using the "golden eyeball" approach. It may 

be fruitful to investigate ways of overlaying symbols on sample fields of video using a 

more controlled and formal procedure. 

One bottom line question is, "How do HUDs in use today circumvent the problem?" The 

answer to that question may provide guidance here. 

Database considerations 

The database storage requirements for storing key runway locations is very modest to 

negligible, when compared with the storage requirements needed for storing elevation 

data. A few floating point numbers (lat and long of the runway centroid) and a few 

attribute codes (runway size class, azimuth, material class, ...) are likely to be sufficient 

34 
for rendering runway areas at the level of detail shown at the workshop. It is feasible 

using this or a similar method to encode all the nation's runways in a few EPROM chips. 

In contrast, elevation data like that stored in a DTED Level I format requires something 

on the order of a 16 bit number every 93 (3 arc seconds) meters. At this sample 

spacing, five optical discs at about 680 Mbytes of storage each can store the elevation 

profile for the entire United States. By the time the HSCT go-ahead is given, chips with 

a gigabit of storage are projected to be widely available. This means that a few chips may 

be relied on to store even fine grained elevation profiles. 

It is likely that the database structure will have a hierarchical arrangement, coarse to fine 

as the runway or terminal areas are approached. 

sampling resolution that is widely thought to be insufficient for rendering scenes at or 

near the runway. Ten times finer spacing may be required along each of the major axes 

over the earth's surface. This implies about 100 times more samples total are needed but 

only in the terminal area. The impact on the total database may be minor.] 

[ DTED Level I carries a coarse 

The real problem is the database infrastructure. Who will bear the cost of setting up a 

database with a flight critical level of integrity? And who will decide what goes into it 

and what gets omitted? And how will it be maintained? 

Pathway goalpost extent and video 

When the pathway is shown overlaid on a background of video, the goalpost may project 

to the nominal geometric plane of a flat earth despite the presence of rough and perhaps 

mountainous terrain. Adjusting the height of the goalposts so that they intersect the real 

earth volumes present in the video image may be difficult to do and certainly implies an 

elevation database or dynamic means of estimating elevation in real time. 

To circumvent these difficulties, it is suggested that the goalpost extent remain 

unmodified and referenced to the geometric plane of the runway threshold. This should 

remain easy for the machine to render and for the pilot to interpret. 

Later, when an elevation database is in place, the goalposts may be used to highlight 

CFIT hazards; color codes andor flashing attributes may be applied to the post to 

annunciate the different levels of urgency. 

Pathway versus entrenched flight director 

Perhaps the wholehearted endorsement that the pathway format received at the 

workshop** makes this note unnecessary but I thought it incumbent on me to point out 

that existing graphics techniques might be invoked to eliminate all or an appreciable part 

of the concern. A memo by Dave Regal preparatory to the workshop highlighted the 

long-standing concerns about introducing pathway formats into the PFD arena. 

35 
I can go into more detail but the graphics concept is along the following line of thought: It 

is technically feasible to "grow" the pathway out of the traditional flight director using a 

control knob, or rocker switch or selection switch. The growth can be a gradual 

metamorphoses that happens under pilot control or it can be switched in by the pilot as a 

format option and enhancement. More detail will be provided if there is interest in this 

area. Whether this kind of approach is needed remains to be seen. 

d'd: I heard statements (paraphrased here) like: "The pathway is so much easier to use." 

and; "The pathway uses elements already certified." and; "The pathway is almost 

identical to the entrenched PFD along a number of important dimensions. It's not much 

different than a PFD." 

Opportunity for pathway to convey hazard and constraint situation awareness 

Mary Kaiser pointed out that the pathway format may provide opportunities for boosting 

situational awareness beyond the statistical centerline guidance walls. A subcommittee 

of the FAA, studying cockpit safety, recommended that cockpit display formats must 

communicate situational awareness more effectively than they do today. The 

subcommittee stated that the display format must indicate the location of hazards. It 

stated that the communication is increasingly important as the airspace grows more 

congested and flight path tolerances narrow. The objectives are to enable more effective 

and safer navigation while negotiating difficult terrain, parallel runways, tighter aircraft 

spacing, etc. Perhaps there is a way to augment the pathway, with its compelling pictorial 

display, to do just that. 

Other Notes from Workshop #2 

From: "Tom G Sharpe" CREMS.TGSHARPE@CREMS.ROCKWELL.COM 

Comment re ghost aircraft guidance: 

One observation, I think made by Terry Abbott, was that the "guidance" should be 

consistent for all flight modes. For modes like heading holdcapture, altitude 

holdcapture, using a ghost aircraft displaced from own aircraft flight path vector (FPV) 

to indicate guidance commands will appear to the pilot much like "chasing" the ghost 

aircraft down the tunnel even though the underlying "guidance algorithms may be quite 

different. The area where there may be an inconsistency at present in your setup is when 

the aircraft is outside the tunnel and on an intercept course. With your current algorithm, 

the ghost aircraft position is based on a perpendicular dropped from current aircraft 

position to the tunnel. In some ways this seems quite natural since one watches the ghost 

fly down the tunnel and simply "falls in behind him". However, if one is in a heading 

hold mode flying an intercept path with respect to the tunnel, the ghost should underlie 

the FPV if I am on the right heading and then should start demanding a maneuver in one 

direction or the other when I hit the capture trip point for acquiring the tunnel (i.e. it will 

not cross my path from one side to the other as it does now.) Another case is that one is 

in "tunnel track mode" and flies out of the tunnel. This case is a little less straight 

forward because it depends on the strategy adopted by the guidance algorithm for 

36 
returning one to the tunnel. As an extreme case consider flying away from the tunnel at 

90 degrees - by the projection algorithm, the chase airplane would disappear from view 

since it would be behind you. It would seem that in this case either some kind of mode 

change should occur and be annunciated or the chase airplane should be in view and 

cueing me for a return to the tunnel. I don't have any final answers here -just the 

suggestion that this is an area that needs more work. 

Notes on Pathwav Displays Workshop #2 

T.G. Sharpe 

9/20/94; Revised 10/14; 10/19;11/3 

GUIDANCE CUES 

3D Trend Vector: 

* 

* 

* 

* 

3 and 6 second (2,4,6 second ?) projected aircraft position 

Used gull wing (nose of aircraft) symbol 

Parrish claims can fly tunnel with this in lieu of guidance cue 

Dropped after first workshop because was thought to add 

clutter 

Ghost Aircraft Guidance: 

Ghost aircraft leads "own" aircraft by 8- 10 seconds in pathway 

If ghost aircraft flies down center of pathway, own aircraft 

tends to "cut" the comers 

Algorithm has ghost aircraft fly outside tunnel in turns so that own aircraft stays in 

the tunnel 

An alternate approach would be to have the ghost aircraft stay in the tunnel (i.e. not 

be compensated) and to track it with a "quickened" or acceleration compensated 

flight path symbol. This approach was not liked as well in a cursory evaluation 

("too active"), but the implementation may not have been optimized. This 

approach may also pose problems when not flying chase or when trying to take 

crab out on landing. 

Coming toward the tunnel from the outside at an angle, say 45 degrees to the 

tunnel, the ghost aircraft appears to be to the left side of the flight path vector at 

first then moves to the right crossing the flight path vector. Falling into trail 

37 
behind it to capture seems a very natural maneuver. Note that the ghost is drawn 

8 seconds ahead of the perpendicular to the tunnel dropped from own aircraft. 

Ghost Aircraft Appearance: 

* Concern was expressed that perspective ghost aircraft was overkill (and cluttering) 

when flying the tunnel, but useful when acquiring the tunnel; compromise was to 

show perspective aircraft when outside the tunnel, and simple circle guidance cue 

when inside the tunnel. not sure where this wound up?? 

* 

* 

Need hidden line removal to improve appearance 

Original flashing "aim point" on tail of ghost was changed to a non flashing circle 

and flashed briefly as an alert just prior to flare. 

* 

4D NAVIGATION 

Time Rails: 

Lots of "white things" add up in the middle, make the ghost aircraft magenta. 

Angle irons on front portion of tunnel to show status of time requirement 

Symbol represents 4 second interval; small right angle pointer in middle indicates 

exactly on time 

Symbol is normally amber with right angle in green; symbol turns yellow if right 

angle pointer leaves symbol but is between 4 and 6 seconds off and turns red if 

pointer is more than 6 seconds off 

Right angle pointer symbol pegs for fast but dropped behind angle irons for slow 

Suggested modification was to peg pointer symbol in both directions and to display 

time error digitally while pegged 

Originally autothrottle did not include time control; so speed trend vector and time 

rails were at times in conflict; this was later corrected 

Note that is very possible to get too far off in time to be able to recover 

(particularly in the fast direction) without deviating from the path (Le. time eating 

diversion or cutting corners to save time); would be nice to have some way of 

indicating this condition 

38 
* Should remove pointer from rails on final since at this late stage are not going to 

worry about managing time - "..from outer marker, you are not going to screw 

around with time keeping! (D. Hooper)" 

PATHWAY SYMBOLOGY/PRESENTATION 

Dorighi Tunnel: 

* Actually Dorighi, Ellis, Grunwald (of Ames) 

* Considered very low clutter; comers of square tunnel simply marked with four 

dashed lines 

* When off to the side; only 2 dashed lines are drawn to avoid distracting optical 

anomalies with 4 lines - sounds strange but seemed to work okay in practice 

* Several comments that "time rails" (see 4D Navigation above), although not 

intended for that purpose, dramatized the front end of the tunnel in a dramatic 

way 

* This tunnel avoids the difficulty incurred by many symbologies of having an 

accumulation of far off symbols adding up to a very bright center in the tunnel 

Soft Pathways 

* Idea here is how to handle pathway displays when constraints are soft or there are 

constraints in one axis but not the other 

* Lots of discussion, no consensus 

* Pathway is not appropriate for all cases; pathway is "attached to earth" in normal 

viewpoint so doesn't work for heading hold, performance climb or descent, etc. 

which are not tied specifically to earth although they may have to be 

accomplished in some volume constraints 

Meaning of Tunnel/Tunnel Characteristics: 

* Meaning of tunnel walls - this came in for a lot of discussion. e.g. what is 

consequence of going outside the tunnel - sometimes trivial, but if tunnel is to 

avoid terrain, going outside could be catastrophic. On final approach tying the 

tunnel to the emerging "tunnel" certification criteria seems logical but further out 

and enroute things are much muddier. Flight corridors, e.g. across Atlantic are 

set wide to account for navigation errors. {The tunnel width should reflect what 

the pilot should stay within so that the sum of his path following errors and the 

navigation imprecision keeps the aircraft in the required corridor (my input)) 

39 
a: A/C should move through tunnel rather than push tunnel ahead of it 

* Need to be careful in mixing perspective and non- perspective symbology; okay to 

do just need to be careful 

* Lots of discussion concerning whether tunnel should show that "busting the tunnel 

'I in one direction may be more hazardous than in the other - consensus was that 

tunnel shouldn't try to show this - current industry philosophy does not 

distinguish cost of violating a constraint (e.g. really dangerous versus sort of 

dangerous)- continuing concern about how to define the tunnel boundaries. 

* When should tunnel disappear - at 50 ft, 100 ft, ?? consensus was question should 

be determined in simulation; similar question on angle irons or rails 

* Another reason for close tolerance on approach tunnel is that it improves the 

touchdown footprint 

Noodle Tunnel 

* Front end of tunnel remains fixed to aircraft as one maneuvers while far end 

remains anchored 

* Pilots did not like; "tunnel kept whipping all over" 

* Might have applicability to soft pathways 

Field of View 

* Parrish has compared FOV for pathway displays; 70 deg FOV is much preferred 

over 40 deg but performance differences were very minor 

* All of this pathway stuff was shown on a 70 deg FOV HDD (VISTAS) or on a 40 

degree projected outside scene; almost everyone used the projected scene because 

it was more attractive in appearance due to simulation artifacts on head down 

presentation. 

OTHER SYMBOLOGY 

Velocity Centered Display 

* Normal presentation is "attitude centered", i.e. the gull wing, or nose of the aircraft 

is fixed on the display and the other objects move, importantly in this case one 

can never lose the pitch indication since the gull wing and pitch tape are always 

on the screen. 

40 
* Velocity centered(VC) is based on idea that "everything is happening around the 

flight path vector" so it should be fixed on the display; also with the attitude 

centered display a lot of the display is occupied by sky which isn't of much 

interest 

* With VC the gull wing still indicates pitch but the problem is that it is very possible 

for it to go off screen so lose pitch indication - some didn't seem concerned about 

pitch indication, but others did. 

* The even more significant observation about VC is that it is not conformal with the 

outside world, so could not be used on a HUD. To see this, note that the velocity 

vector or flight path symbol appears in the center of the screen (which is fixed to 

the body of the aircraft) even when there is a crab angle due to a cross wind; thus 

if landing, the runway symbol would appear under the velocity vector (Le. in the 

center) but the out the window real world runway will be off to one side. Another 

way to look at this is that the pilots body in a crosswind is not facing in the 

direction that the aircraft is going, so the real world runway appears to one side or 

the other if the pilot is looking straight ahead out the nose of the aircraft (Note 

that because the HUD is body-fixed the nose of the aircraft aligns laterally with 

the center of the HUD. Interesting side thought is what about helmet mounted 

display (HMD). Is the HMD drawn centered on the pilot line of sight (?) since 

neither velocity vector or nose of aircraft lie in a constant position on a 

"conformal display" HMD as the pilot turns his head) 

Raw Deviation Pointers 

* Standard needle and pointer at bottom and right - these are identical to standard 

EFIS symbology for raw localizer and glideslope deviation; except numeric 

deviation is displayed at appropriate end when deviation is pegged 

* Dotted square around flight path symbol (which banks with aircraft). This was 

criticized as redundant with needle and pointer and cluttering up middle. 

Alternate view was that peripheral needle and pointer were too far out to attract 

pilots notice and that center type indication was good. 

* It was decided to delete the "ILS box" to cut down clutter since it duplicated the 

raw deviation pointer information - later this was put back when the aircraft was 

outside the tunnel?? 

41 
CERTIFICATION 

FAAKertification Comments: 

Mike Norman - some concern about technology readiness/risk of tunnel/pathway 

concept 

(ref the flashing circle on the ghost aircraft tail) "..you never have continuously 

flashing things on a display. This is FAA party line. (Berk Greene (B.G.);FAA)" 

B.G.: - don't see risk in certifying tunnel concept; need to consider avionics and 

aircraft malfunctions; not entirely sold on benefit of tunnel on straight in final 

(George Lyddane (G.L.)agreed), clearly useful for complex SIDS and STARS - 

maybe useful for go-around though. Skepticism about whether data link of 

pathdchanges will be reality by 2005(G.L. agreed)- FANS committee working 

standardized data link messages(?) has thrown up their hands and quit, pilots like 

long finals and readily abandon FMS when changes occur. 

G.L. - waypoint integrity will not be entirely in the data base; critical waypoints 

will be data linked up with cyclic redundancy codes, etc. and compared with 

what is stored in data base - called this the "golden double - key" approach 

(coming out of Special CATegory, SCAT, committee stuff). Strong lesson from 

HUD work is that flight path vector (FTV) is very helpful/good, safety increases 

but A/C is already "safe enough" so must show economic benefit. 

FAA personnel in general seemed to want to see more aspects of the Flight 

Dynamics symbology - in particular numeric radio altitude just under the flight 

path symbol; also radio altitude as soon as valid (up to 1500 ft), not just from 

500-300 feet down; also if gull wing lies in same location as flight path vector, 

flight path vector will mask it behind the circular portion; FAA also wanted a 

solid, white horizon line which NASA had removed in their simulation. 

Radio altitude on latest HUD comes in as soon as it is valid and is displayed 

underneath the FPV. The FAA likes this "real sensor" (real altitude above 

terrain??) 

MISCELLANEOUS 

ATC/FMS: 

* Dave Hooper (American Airlines pilot) - takeoff out of Orange County is very 

steep for noise abatement reasons - pathway with speed management would help. 

* Charlie Hynes (Ames) - decelerating approach is another way to cut noise and 

automatics can handle this okay. 

42 
Display Appearance/Symbology Ideas: 

* 

#: 

* 

* 

* 

* 

* 

* 

* 

* 

* 

* 

Navigation display inset on NASA's HDD was very effective in showing a plan 

view of the entire flight path or tunnel; whereas the perspective presentation only 

shows the portion in front of you. The perspective cone (or wedge in 2D) was 

shown on the plan view to tie the two together. 

There was a desire to have some way of handling recovery from unusual attitudes; 

e.g. the chevrons on an AD1 at very high pitch angles 

Wind arrow and DME were desired - a "billboard" approach to DME indication 

was tried. 

Need consistent symbology over entire flight regime ( T. Abbott, LaRC) 

At high altitudes (e.g. 65K feet) the true horizon and zero pitch do not line up 

physically. NASA's simulation biases the top of the terrain to be zero pitch in all 

cases. 

Some examples of display of alternate paths, i.e. active and proposed alternative, 

were shown - the examples were fairly rough 

Concern about proper choice of color/hue/saturation/coding, etc. 

Concern about occlusiodinterference of symbols, may need priority/"no draw" 

zones around say FPV 

Runway outline a la HUD - I asked about this. B.G. said history of this was to give 

some sense of ground awareness, i.e. impending earth { - suggested by Gordon 

Hardy(Ames)}, they go away at 50 ft because it is important to break fixation; 

they may also obscure runway edge lights (this was more of a simulator issue, 

because in the real world they never line up); many reasons why they don't quite 

line up with real world runway - heading errors are one. 

TV image on HSCT will be color high definition TV because many of real world 

facility cues are color coded (Mike Norman, Douglas) 

Keep worrying about clutter, particularly when include video or sensor underlays. 

Gull wing (or waterline symbol) is a clutter issue on aircraft that fly near zero angle 

of attack ( with zero AOA, the gull wing overlays the flight path vector) - 

discussion of this was inconclusive. 

43 
TakeoffRollout : 

* Concern about takeoff and needing some monitor/status maybe along the lines of 

LaRC Takeoff Performance Monitor System (TOPMS); - human factors of 

TOPMS symbology was criticized. There were also liability concerns. 

Miscellaneous Notes: 

* Berk Greene (FAA) wanted aircraft model to account for potential of tail strike - he 

seemed particularly concerned about this. 

* Some concern was expressed that none of the cases flown involved turbulence and 

lead terms can generate very active control in turbulence 

* B.G. did not think panel space in HSR drawing shown was large enough; he 

thought it was smaller than today's 737 when cutouts for side visibility were 

taken into account - He was impressed with VISTAS panoramic display 

* Control column versus sidestick controller: Boeing position is that the control 

column is a display device as well as a control element 

* There was a request to put up more TCAS targets in simulation - don't know what 

conclusiodresults of this were. 

Notes on Pathway Displays Workshop #2 

High - Speed Research Program 

NASA - Ames Research Center 

Hi Russ, 

This is a lame attempt to respond to your request for comments on the workshop. Most 

of my concerns were raised in Mike Johnson's comments and the memo Dave Regal sent 

out prior to the workshop. I think the workshop itself is a useful forum for rapid 

prototyping development. Whereas rapid prototyping has its place in design 

development, it does suffer from a syndrome of too many cooks throwing whatever looks 

good into the pot. As I mentioned at the meeting, it's my hope that someone will go back 

and do a "reality check" on the ideas generated at the workshop, and perform systematic 

evaluation on the best candidates generated. 

Some particular issues that stuck with me were: 

1) Providing a systematic and consistent use of color coding. 

2) Making a meaningful distinction of pathway objects "in the world" and "tied to the 

aircraft." Objects "in the world" should have canonical geometric properties (e.g., 

expansion). 

44 
3) Dealing with the clutter that results as everyone attempts to place "critical information" 

near the flight path vector. Some ideas to aid in decluttering were discussed (color 

coding, no draw" zones, transparency), but each technique has advantages and 

drawbacks that need to be considered (e.g., see M. Johnson's comments on 

transparency). It might also help if pathway objects in this area were "in the world" to 

ameliorate "HUD fixation." You might want to talk with Dave Foyle about this issue. 

I think the overall response to pathway concepts was quite favorable (although some 

of the enthusiasm may reflect a "something is better than nothing bias"). The desire 

to extend pathways to non-CGI displays demonstrates this, but also raises new issues 

concerning visibility of non-pathway objects (e.g., runway incursions) via 

sensor/video imagery. Thus, the issue of clutter remains crucial. I'll be interesting in 

seeing Mike's notes. Thanks again for an interesting workshop. 

Mary Kaiser 10/3/94 5: 12 PM 

Notes on Pathway Displays Workshop #2 

I think that you are on a very good track now with the Pathway display and I am quite 

pleased with the symbology that is formulating. 

I still have some concerns about the loss of real time meteorological visual cues. 

I also feel that the present TCAS symbology will lead to excessive clutter in its present 

form when we display 15 or 20 targets. We will display this many targets in terminal 

areas like ORD or JFK. 

Also, while others talk about removing the pathway while at altitude, I would like to 

suggest that the pathway be a full time display. This would be the FIRST visual 

indication that the aircraft were deviating from one or more of it's 4 dimensional values. 

Talking about and flying simulations is probably the best way to resolve these and many 

other issues concerning the development of the HSCT. I do hope that NASA will 

continue to provide additional workshops. I remain willing and able to participate in any 

additional workshops. Thanks for your time and dedication to this project. 

Sincerely, Dave Hooper 

Notes on Pathway Displays Workshop #2 

Dear Russ, 

I just had an opportunity to visit with Paul Leckman during one of my trips with 

American. Paul showed me a video that was very impressive. It was a tape of an 

approach to Aspen. In the foreground was some type of HUD symbology, which could be 

45 
replaced by the Langley HSCT symbology set. The background was a color rendition of 

the actual topography. This was the best thing I have seen yet. You could actually fly 

into any canyon you desired. This depiction was displayed on the PFD. The ND also had 

an overhead view of the land that was also color coordinated to elevation. You could use 

this display to see if a particular canyon was or was not a boxed canyon. The flight path 

vector indicator becomes very important with this type of display. Just place the flight 

path vector on or above the ridge line and you are clear of the terrain. Tthe forward 

visibility on the HSCT is going to be reduced. I would like to have this loss of foreword 

visibility replaced with a visual display of what I would normally see in the real world. 

Even if it is synthetic. I know that you said that Terry would be hosting any additional 

workshops, but I just wanted to let you know what Paul has shown me. I think that 

combining the Langley HSCT symbology set, with this colored display of the topography 

would be what I would expect to see on an aircraft which is scheduled to fly in 2004. 

Thanks for listening to me again. 

Sincerely, 

Dave Hooper - Captain 

Technical Highlight: 

The second Interactive Workshop on Pathway Displays was held at Langley on Sept. 20 - 

22. Ten pilots and fifteen display design researchers participated, with representatives 

from the FAA, American Airlines, Boeing, Honeywell, Hughes, McDonnell Douglas, 

Rockwell, USAir, and the NASA. The workshop employed a rapidly reprogrammable 

pilot workstation that allowed participating pilots to fly pathway concepts and to have all 

participants make suggestions which were implemented iteratively to arrive at a better 

understanding of pathway displays. Pathway concepts were enthusiastically and 

unanimously endorsed by the workshop participants as being extremely valuable for 

complex approach path "look-ahead" functions and for other situation awareness 

enhancements, even on "straight-in" approach paths. 

46 
Workshop #3 

March 21-22,1995 

The Flight Test Symbology Workshop #3 

Summary: 

The High Speed Research (HSR) Flight Deck Integrated Display Symbology Team, with 

representatives from D&I, G&C, and XVS, held a Flight Test Symbology Workshop on 

March 21 and 22, 1995. The workshop objectives were to examine and resolve the 

symbology issues associated with the pilot-in-the-loop flight operations portion of the FY 

‘95 flight test. The surface operations portion of the flight test will be extremely limited 

because of the lack of full aft deck steering and braking control. The team determined the 

symbology set to be used and selected the factors to be examined in the flight test. Of 

particular significance was the development of a possible controVdisplay mode change 

procedure for the flare portion of a landing approach intended to provide improved 

control from the Aft Flight Deck of the 737 during touchdown. Further refinement of the 

algorithms involved and the procedure itself are necessary. Some other issues remain to 

be addressed outside of a workshop environment, including symbol color selection 

against FLWcolor TV background images, fine tuning of a guidance symbology 

parameter (follow-me aircraft lead-time ), determination of a symbol positioning 

algorithm (follow-me aircraft positioning within a sensor image FOV), and blocking of 

the experimental conditions across the subject pilots. 

Team Attendees: 

Terry Abbott 

Andy Durbin 

Gordon Hardy (Jeff Schroeder) 

Walt Johnson (Mary Kaiser) 

Russ Parrish 

Other Attendees: 

Dale Dunford 

Linda Foernsler 

Randy Harris 

Jim Robertson 

Steve Williams 

Lee Person 

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51 
Detailed Mi n Utes: 

The workshop utilized the simulation capability assembled by an XVS team lead 

by Randy Harris and Steve Williams. Their efforts merged the image generation 

facilities of the VISTAS/Silicon Graphics Computers with the LaRC central 

simulation facility's high fidelity 737 aircraft simulation. The resulting capability 

gave a fairly realistic representation of the aircraft environment that will be used 

in the FY '95 flight test. 

18.77 

37.32 

37.32 

37.32 

41.46 

-41.61 

SGI Reality 2 computers were used to provide head-down EFlS displays (PFD 

and Nav) to VISTAS and to produce simulations of the available imaging sensors 

at the aircraft locations shown in the table below: 

2.53 

-0.23 

0.23 

-0.23 

0.00 

0.00 

feet 

tPlLOT EYE 

Nose Camera 

Y 

+ in front c.g. 

- behind c.g. I - pilot's left 

+ pilot's right 

15.94 I 2.53 I 

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- below c.q. 

4.27 I 

I 

-4.00 

-4.00 

-4.27 

-1.91 -5" 

27.71 -30" 

FOV 

I 

81 "H x 64.2"V 

Sensor image output was fed via NTSC video to an SGI VGX computer (two 

generations older than Reality 2) with identical capabilities to the on-board 

ATOPS Skywriter. The VGX digitized the sensor image and combined the 

image with the appropriate symbology set. The VGX computer also produced 

the symbology set, the pathway, the follow-me aircraft, a wireframe terrain 

database, and a filled polygon CGI terrain database, as selected. 

The symbology issues and options addressed were limited to the approach and 

landing task with the firmware restrictions imposed by the flight test sensors and 

equipment. As such, integration issues relating to other flight deck displays (e.g., 

the PFD) were not discussed. 

There will be a single scenario used of the symbology evaluation part of the flight 

test. This will consist of an initial flight segment 90-degrees to the approach path 

with a single turn to a short final approach segment for landing. A key 

quantitative factor for the display evaluation will be touchdown dispersion. This 

is significant in that Lee Person does not believe that the current ATOPS controldisplay implementation will support this requirement. A possible solution for this 

was discussed and is provided below. 

The initial symbology set that was used as a starting point for this work was 

based on the display format selected at the last Pathway Workshop at LaRC. 

Major modifications to that baseline for the sensor flight test are as follows: 

52 
1. A flare cue was added and will be used with all symbology combinations. A 

magenta line will appear at the bottom of the FOV at 100 feet(?) and rise 

proportional to altitude changes to meet the -3” pitch/flight-path reference at 50 

feet (?), where it will continue to rise and present the flare cue via an hdot/h flare 

law. 

2. A pitch/flight-path reference symbol for a 3-degree approach angle will be 

provided whenever a precision approach path is not provided. 

3. It was found that (for most of the flight conditions) driving the velocity-vector 

with actual gamma introduced high pilot workload for the guidance tracking task. 

In general, commanded gamma will be used to drive the velocity-vector symbol. 

This is the same approach used in the ATOPS. 

3. In an attempt to augment the touchdown performance with the current 

ATOPS control-display implementation, a transition from commanded gamma / 

to actual gamma will be used during flare and touchdown, with the velocity-vector 

being fully driven by actual gamma at touchdown. 

4. In addition to item 3, we are considering using attitude-control-stick-steering 

(ACSS), as opposed to velocity-control-stick-steering (VCSS), during the final 

part of the landing task. This concept will require further evaluation. In addition, 

to support this control mode switching, the ATOPS simulation and flight software 

will need to be modified to provide a gamma command value when in ACSS. 

5. The color for the FLlR sensor image does not provide sufficient visual 

contrast with the majority of the symbology. This needs to be resolved. 

SYMBOLOGY 

attitude “waterline” 

roll scale & Dointer 

attitude scale (pitch grid) 

Two major symbology sets were developed. The first set (set 1) would 

conceptually be used for a visual approach task where there is no pre-defined 

flight path. The second set would be used with a pre-defined path. For this 

latter situation, two symbology sets were defined. Set 2b would provide all path 

guidance and path symbology. Set 2a is a subset of set 2b, but the 3-D pathway 

will not be shown (this is a ‘decluttered’ mode). The symbology sets are 

provided in the following table. ’ 

SET1 SET2a SET2b 

X X X 

X X X 

X X X 

Set definitions: 

Set 1 is no pre-defined path, similar to visual approach requirements. 

Sets 2a & 2b are for a pre-defined path, similar to a precision approach. 

Set 2b is a “decluttered” subset of 2a. No 3-D pathway is displayed. 

airspeed & altitude tapes(see note) 

velocity-vector 

vertical meed 

X X X 

X X X 

X X X 

control panel speed target on speed tape 

absolute altitude lxlxlxl 

X X X 

control Panel altitude taraet on altitude taDe lxlxlxl 

53 
I meed trend on weed taDe IXlXlX 

potential gamma relative to v-v symbol 

track angle & heading 

flare cue 

I speed error on v-v svmbol lxlxlx 

X X X 

X X X 

X X X 

reference marker for flight-path (pitch) angle 

lateral & vertical path error scales and pointers 

path altitude target on altitude tape 

path speed target on speed tape 

guidance “follow-me” symbol 

Dathwav 

~ 

X 

X X 

X X 

X X 

X X 

X 

note: Only tapes will be used for the flight test. The issue of tapes or 

digital-only are not a primary factor for this study and therefore were not 

included. 

Background Image 

FLI R w/o wireframe 

with wi ref rame 

TV w/o wiref rame 

with wiref rame 

The test matrix defining the combinations of background images and symbology 

sets is given below. Note that all combinations may not be flown by all pilots. 

Also note that the wireframe subset is the DMA database ground environment 

outline used for navigation source/sensor alignment evaluation. 

Symbology set 

Set 1 Set 2a Set 2b 

X X X 

X X X 

X X X 

X X X 

CG I X X X 

Continuing development, problems noted, and action items: 

1. The guidance symbology (follow-me aircraft) should track the flare cue once 

the flare cue becomes the valid command. 

2. Contrast between symbology and the FLlR image needs to be resolved. It 

may also be an issue with actual color TV video. 

3. The algorithm for the velocity-vector symbol during final approach, flare, and 

touchdown needs further refinement and evaluation. 

4. ACSS needs further evaluation and possible modification. 

5. Gamma command information needs to be computed for ACSS conditions. 

6. The flare cue did not function correctly for all of the proposed sensor lookangles. 

7. The attitude ‘waterline’ symbol was embedded in the roll scale for some of the 

proposed sensor look-angles. 

8. The rudder pedals need to be operational. 

9. The lipstick cameras (tail fin and nose) need to be minified. 

54 
10. The follow-me aircraft lead time needs to be tuned. It is presently set at 8 

seconds (tuned for a generic transport model), and it may be desirable to vary 

the time parameter as a function of range. 

11. The algorithm for the positioning of the follow-me aircraft needs to be 

determined for each sensor image FOV. 

ACWS Tuning Investigation 

Of particular significance during the Flight Test Symbology Workshop on March 2 1 and 

22, 1995 was the development of a possible control/display mode change procedure for 

the flare portion of a landing approach intended to provide improved control from the Aft 

Flight Deck of the 737 during touchdown. The following was extracted from the minutes 

of the workshop. 

It was found that (for most of the flight conditions) driving the velocity-vector with actual 

gamma introduced high pilot workload for the guidance tracking task. It was decided that 

in general, commanded gamma will be used to drive the velocity-vector symbol. This is 

the same approach used in the current velocity-centered ATOPS displays. In an attempt 

to augment the touchdown performance with the current ATOPS control-display 

implementation, a transition from commanded gamma / to actual gamma was proposed to 

be used during flare and touchdown, with the velocity-vector being fully driven by actual 

gamma at touchdown. In addition, we are considering using attitude-control-sticksteering (ACSS), as opposed to velocity-control-stick-steering (VCSS), during the final 

part of the landing task. This concept will require further evaluation. In addition, to 

support this control mode switching, the ATOPS simulation and flight software will need 

to be modified to provide a gamma command value when in ACSS. 

On April 27, 1995, I invited the following to VISTAS Lab: 

Rob Rivers, LaRC test pilot 

Lee Person, retired LaRC test pilot 

Dave Raney, GCB control systems engineer 

Bill Lynn, ATOPS control systems engineer 

Steve Williams, CVIJ3 graphics programmer 

Patricia Hunt, Lockheed graphics programmer 

The purpose of the meeting was to look at the flare and touchdown characteristics of the 

ATOPS aircraft control system that will be used for the sensor flight tests conducted in 

September, 1995. Consensus was arrived at in the following areas: 

(1) It would be impractical and unnecessary to tune the aircraft attitude control 

wheel steering mode before the flight tests, as there would not be enough 

time available in the airplane to do it. 

(2) For the landing tests the control system should be left in velocity control 

wheel steering mode; that mode, with the new flare symbology 

immplementation on the Skywriter displays, should provide acceptable 

touchdown performance from the aft deck. 

55 
The display symbology should be modified so that if there is an error between 

commanded gamma and actual gamma of more than 0.5 degrees for more 

than 1 second, a dotted flight path symbol would be drawn representing the 

actual flight path. 

VISTAS sidearm controller characteristics in the roll axis make piloted 

studies of precise lateral control very questionable. The deadbands in the 

lateral axis of the sidearm controller are too large. A new sidearm controller 

is needed. 

Use quickened flight path angle when flying in attitude control wheel steering 

mode. and 

The sensor display with symbology is much easier to fly than VFR flight, 

even at 12 hertz update rate. There should be no problem flaring the airplane 

with that display and the flare symbology. 

The following improvements could be make to the simulation: 

(1) Display commanded track angle and actual track angle. 

(2) Use the two buttons on the top of the VISTAS sidearm controller to slew the 

commanded track angle (this capability is present in the aft deck with the 

coolie hat trim button). This implementation would overcome the VISTAS 

sidearm controller problems in the roll axis 

(3) The range to the ghost aircraft seems to be too small. 

(4) Three degree reference line should be separately selectable 

Therefore, no additional tests are needed to tune the ATOPS attitude control wheel 

steering for the sensor flight tests. 

Randall L. Harris, Sr. 

4664 1 

Date: 4/28/95 157 PM 

To: Randy Harris 

From: Terence Abbott 

Randy, 

I thought that the most significant thing that came out of the previous workshop 

regarding landing the 737 from the AFD was the blending from commanded to actual 

gamma to drive the flight path symbol during the landing flare. THIS IS 

INDEPENDENT OF CONTROL MODES. I also believe that the 112 of degree over a 1 

second period will continue to mask commandedactual gamma differences, primarily 

because the landing flare maneuver is a short-term, highly-dynamic (for a transport) 

maneuver. The biggest problem in the longitudinal axis in landing the 737 is that the 

control & display system in the AFD is open-loop in the short-term. You cannot really 

see what the aircraft is doing. I have very great reservations reverting to this approach. 

56 
Terry, 

Both pilots felt this was the better way to go. They did say that if we decided to go the 

other way we should use quickened gamma and not raw gamma. The problem with raw 

gamma is that it moves the wrong direction first before going the correct way (quote from 

Lee). 

Terry : (I thought that from the previous workshop that a blend from commanded 

to actual gamma would be used to drive the flight path symbol during the landing flare. 

Your consensus item #3 uses a different approach that except for your recent meeting, has 

not been able to produce consistent landing results. Why was this changed from the 

previous implementation?) 

You had to be there (I felt Lee made a reversal of the things he said previously. Both 

Rivers and Person felt that it would be impractical to switch from VCWS to ACWS. 

Therefore, it made more sense to display only the commanded gamma if you would 

display actual gamma when there was a difference of more than 1/2 degree. 

Terry : (- From your consensus item #5, if we will not transition to ACSS during the 

landing, why should we even consider ACSS? It looks to me like we'll be using VCSS 

throughout the test (based on your items #1 & #2).) 

That is correct. For these tests we will not be using ACWS. 

Terry : (- I question your consensus item #6 result. How were you able to obtain a VMC 

landing touchdown comparison?) 

These statements in #6 were the opinion of both pilots, Rivers and Person. Lee made the 

comment comparing it to VFR because of the symbology (more precise information) 

present in the display and because of the larger magnification factor of the display over 

the EADI (velocity-centered) in the ATOPS. Both pilots were able to make touchdowns 

in the VISTAS simulator that were below 3 fps when the throttles were not retarded 

before TD. 

I am sorry you could not have been there. We will readdress the problem when Mike 

Norman is here with Rob Rivers on May 25. 

Randy 

Primary Flight Display (PFD) Symbology Description 

57 
Flight Deck Integrated Display Symbology Team 

Primary Flight Display 

Symbology Description 

PFD) 

edited by Terence Abbott 

7 July 1996 

58 
The intent of this informal report is to document the preliminary XVS/PFD symbology 

set developed primarily by the XVS flight test team for the XVS sensor flight test 

experiments. The development of this symbology took place over a two year period and 

included several symbology workshops that provided for interactive symbology 

development during the workshop sessions. This report will attempt to describe the 

symbology, the symbology 'drivers' or algorithms, and any significant or unique issues that 

were identified. As a caveat, the symbology set described in this report was developed to 

support the XVS sensor flight test and other similar XVS studies. As such, this symbology 

has not been rigorously evaluated in either full-mission or full-workload scenarios. 

Figure 1 has been provided by XVS. The subsequent figures are modifications of the 

original and include numbering of the symbology elements that will be used later in the text 

to describe the symbology. 

Abbreviations and Definitions 

FPG: 

FPM: Feet per minute. 

FPV: 

RA: TCAS resolution advisory. 

Crosshairs: Two cue flight director. 

Ownship: Your aircraft. 

Flight path guidance, ghost aircraft, phantom aircraft. 

Flight path vector, velocity vector. 

Symbology Elements 

The general references for this section are SAE ARP4102R and numerous, informal 

notes provided by the XVS team. The numbers of the numbered paragraphs related to the 

numbered items on the figures. Footnotes are provided on the last page that identify the 

source of the various comments. 

1. Flight Mode Annunciator (FMA): Flight guidance and flight control modes should be 

clearly annunciated. It is also recommended that all guidance and control mode 

annunciation symbology be grouped together. (For further information, contact Michael 

T. Palmer, NASA-LaRC.) 

2. Roll scale: As a minimum, tic marks should be provided at O", lo", 20", 30", 45", and 

60". The 45" and 60" may be programmed to appear at angles greater that 30". Digits 

are not required. The 30" mark should be distinct. 

3. Roll pointer: The roll pointer should have priority over all other symbology. A slip (lateral 

acceleration) indicator symbol should augment the roll pointer symbol. 

59 
60 
Figure 2a. 

4. 3-D pathway symbol: 

- Several initial types of flight path “tunnels” were reviewed. The Dorighi 

Tunnel is defined by four dotted lines at the edge of an acceptable error box, 

with square guidance symbols inside the dotted lines, and a reference solid 

box at a fixed time reference ahead of the aircraft. The “Noodle Tunnel’’ is 

defined by a series of boxes, leading from the present aircraft position to a 

reference position on the cleared path, or final approach fix. The NASA 

Langley Goal Post Tunnel is defined by partial boxes consisting of side and 

bottom segments, center pillars extending from the bottom of the boxes to the 

terrain floor, and rectangular tiles inside the boxes defining the path to be 

flown. 

- After an initial evaluation by all of the pilots present, the consensus was that 

the “Noodle Tunnel” had little for the HSCT application and was not 

evaluated further. The rationale for this decision was that because the 

beginning of the tunnel was always tied, laterally and vertically, to ownship 

1 

61 
position, this tunnel provided no cues to path error, merely showing a route 

back to the desired path. ’ 

- A discussion occurred on whether to provide a pathway display element 

during constant heading flight modes or during cruise modes in general. This 

evolved into a discussion, again, on what constitutes a pathway. The 

consensus among the group was that a pathway is a defined three 

dimensional line in space, consisting of curved and/or straight segments, over 

fixed earth-referenced coordinates. Pathways could also have a time critical 

dimension associated with them, during 4-D clearances. This definition is 

consistent with what is presented on FMS map displays in current aircraft. 

Constant heading modes may not fit this definition. It was suggested that 

pathways not routinely be displayed in constant heading modes due to 

difficulties in display or interpretation of lateral flight path errors. It was also 

suggested that pathways, in general, be a pilot selectable display element, so 

that they could be removed in situations where they would be confusing or 

clutter the display. ’ 

Figure 2b. 

62 
- A pathway is not appropriate for all cases; a pathway is "attached to the 

earth" in normal viewpoint so doesn't work for heading hold, performance 

climb or descent, etc., which are not tied specifically to the earth although 

they may have to be accomplished in some volume constraints. 

- The issue of how to display a two dimensionally constrained pathway was 

discussed. This situation could occur, for example, during climb or 

cruise/climb. In this situation, a cleared route over the ground would exist (a 

2-D path), along with an expected altitude at the end of the segment, but no 

specifically cleared vertical path would exist to get there. It would not be 

appropriate to display a three dimensional pathway here, since following 

minor vertical path errors, the pilot would not be expected to return to the 

previously computed optimum performance path, and a new optimum 

performance path should continuously be computed. The distinction between 

path and guidance information should be stressed here - the pathway does 

not indicate how the pilot should reduce path errors (guidance cues do that), 

it merely displays those errors. It was suggested that when pathways are 

laterally, but not vertically constrained, the displayed vertical error should be 

zeroed at all times. The pilot, then, could fly laterally off the path, but never 

above or below it. The practicality or usability of this display philosophy 

remains to be demonstrated. ' 

paths from expected flight paths. 

approaches, the pilot will need this information both to help plan for flight path 

requirements and to visualize the projected flight path with respect to terrain, 

other waypoints, airport references, etc., in the event of a missed approach. ' 

Cleared flight paths, for example, are traditionally displayed in magenta on 

FMS map displays, and should probably be displayed in that color on pictorial 

displays. Proposed or alternate flight paths could be displayed in white, color 

intensity, dotted lines, or suppressed resolution to distinguish them as 

planned paths, on pictorial displays. 

- The problem of indicating cleared versus planned altitudes was mentioned. 

For example, a descent route segment may begin at Flight Level 350 and end 

at 5000 feet MSL, but the aircraft is only presently cleared 15,000 feet MSL. 

One method suggested of indicating this in path data was to present a 

pseudo cloud deck, or translucent tiles, at the cleared altitude on the dis la . Further study is warranted to arrive at an acceptable method of display. 

- It was generally agreed that the edges of the tunnel should correspond to the 

required error tolerance in flight path control. Some method for discerning 

desired error tolerance should also be provided. ' 

- There may be a need, in presenting pathways, of distinguishing cleared flight 

- The need to show missed approach information was discussed. During 

1 

- The need for color standardization in display elements was discussed. 

1 

PY 

63 
4a. Precision 4-D ‘time rail’ symbol: Only needed for 4-D path control. 

- The display of four dimensional pathways (those which include time 

constraints) will probably require both status and guidance display elements 

relating temporal errors. Two predominate philosophies exist relating to time 

constraint guidance - speed control and volume clearance. Further study is 

warranted to develop appropriate cues for four dimensional status and 

guidance display elements. Of note, these may be difficult when the desired 

clearance volume is behind the aircraft. ’ 

- Angle irons on the front portion of the tunnel are used to show the status of 

the time requirement. The symbol represents a 4 second interval; the small 

right-angle pointer in middle indicates exactly on time. The symbol is 

normally amber with the right-angle in green; the symbol turns yellow if the 

right-angle pointer leaves the symbol but is between 4 and 6 seconds off and 

turns red if pointer is more than 6 seconds off. 

behind the angle irons for being behind-time. A suggested modification was 

to limit the pointer symbol in both directions and to display time error digitally 

while limited. 

- The right-angle pointer symbol limits for being ahead-of-time, but drops 

4b. Along-path, distance-to-go marker: The number displayed in the ‘box’ is the 

distance from the ‘goal post’ to the runway, in nautical miles. The number 

above the ‘box’ is the distance from ownship to the ‘goal post.’ In this 

example, ownship is 25.1 n.mi. (along the planned flight path) to the runway. 

4c. Ground reference ‘goal post’ symbol: The ‘goal post’ is an augmentation to 

the 3-D pathway symbology. The ‘goal post’ is anchored to the ground plane 

and the horizontal line forming the ‘T’ is at the bottom of the 3-D path. The 

length of the vertical portion of the ‘goal post’ enhances situation awareness 

regarding the pathway height above the ground plane. 

- Several of the pilots objected to the amount of clutter, articularly early in the 

approach, where numerous goal posts could be seen. 

- When the pathway is shown overlaid on a video background, the goal post 

may project to the nominal geometric plane of a flat earth despite the 

presence of rough and perhaps mountainous terrain. Adjusting the height of 

the goal posts so that they intersect the real earth volumes present in the 

video image may be difficult to do and certainly implies an elevation database 

or dynamic means of estimating elevation in real time. 

P 

3 

5. Pitch scale including horizon line: See SAE ARP4102/7 for a general 

arrangement. Recent research suggests that the pitch scale should become 

nonconformal at extreme pitch attitudes such that the horizon line always 

remains within view. 

- There was a desire to have some way of handling recovery from unusual 

attitudes; e.g. the chevrons on an AD1 at very high pitch angles. 

64 
- FAA recommended a solid, white horizon line which NASA had removed in 

4 their simulation. 

6. Instantaneous vertical speed: A 100 FPM resolution is required from 0-1 000 

FPM. A vertical speed target is desired if vertical speed guidance is provided. 

TCAS II resolution advisory (RA) symbology should be included. 

7. Precision vertical path deviation indicator and scale: The navigation source 

for this scale must be displayed. The recommended placement is between 

the attitude symbology and the altitude symbology. 

8. Radio height: This symbol (presented in a numeric format) may not be 

required for invalid radio heights. 

- FAA personnel in general seemed to want to see more aspects of the Flight 

Dynamics symbology - in particular numeric radio altitude just under the flight 

path symbol; also radio altitude as soon as it is valid (up to 1500 ft), not just 

from 500-300 feet down. 

9. Baroset readout: “STD may be used above the transition altitude. The 

altitude reference (QFE, QNH) and the units (IN, HP) should be annunciated 

with the baroset readout. 

10. Magnetic heading: May not be required for all flight modes. Leading ‘0’ 

digits are required such that 3 digits are always displayed. 

11. Precision lateral path deviation indicator and scale: May not be required for 

all flight modes. 

pathway or position error (three or four dimensional), and flight guidance 

cues. Pathway or position error cues should be easily interpretable, and 

ideally should provide desired, as well as allowable, tolerances in the display 

element. Initially, traditional crosshairs were provided around the velocity 

vector to indicate desired path error limits. Later, these were replaced by a 

dotted box that was positioned in relation to the velocity vector so as to 

indicate lateral and vertical path error. The dotted box was preferred over the 

crosshairs, in that it decluttered the critical area immediately around the FPV, 

and was more easily interpreted than the crosshairs. Some pilots, however, 

still wanted analog error scales (similar to ILS raw data indicators) at the 

edge and bottom of the display. An additional digital display, indicating path 

error in equivalent “dots”, was provided adjacent to the analog scales, which 

some of the pilots felt was a valuable addition to the display element. 

Concern was expressed, however, that these scales would interfere with 

altitude and/or velocity tapes on the display, particularly in high crosswinds. 

Further study is warranted to reduce the size of the analog scales, and move 

them to a location where they will not interfere with other display elements. It 

- Two types of information should be provided on the forward display - 

65 
was also suggested that the scales and error box should be individually 

selectable by the pilot. ’ 

12. Augmented airspeed tape: 

- In addition to the airspeed information, provided by the moving-tape, precision 

speed information is provided by the ‘rotating-drum’ (odometer-type) 

symbology centered vertically on the airspeed tape. Additional speed 

related information is provided (similar to MD-11 or B-777) including: 

airspeed trend (acceleration), stick-shaker speed, Vmin, V1, V2, Vref, 

maximum configuration (flap retract) speed, minimum configuration (flap 

extend) speed, ground speed, Vmo, Mmo, and speed reference. The entire 

set of additional information may not presented (or required) at one time. 

digital-readout continues to be raised throughout all of the workshops. The 

intent of this replacement is to reduce display clutter on the XVS. Further 

analysis is required in this regard since a significant amount of information is 

removed in this replacement. 

- The recommendation to replace the analog airspeed symbology with a 

13. Heading markers on horizon line: This symbology may not be required for all 

flight modes. This symbology may add to the central “area-of-interest” clutter 

problem. 

14. Aircraft (pitch) symbol reference: 

flight path vector will mask it. 

some of the proposed sensor look-angles. 

- If the aircraft attitude symbol lies in same location as flight path vector, the 

- The attitude ‘waterline’ symbol may become “embedded” in the roll scale for 

15. Flight path vector (FPV) symbol: 

- It was found that (for most of the flight conditions) driving the velocity-vector 

with actual gamma introduced high pilot workload for the guidance tracking 

task. 

commanded gamma and actual gamma of more than 0.5 degrees for more 

than 1 second, a dotted flight path symbol would be drawn representing the 

actual flight path. 

- The display symbology should be such that if there is an error between 

16. Flight path guidance (FPG) (phantom aircraft, pursuit aircraft, ghost aircraft) 

symbol: 

pathway or position error (three or four dimensional), and flight guidance 

cues. The guidance cues should be simple enough that in high workload 

situations, the pilot is guided quickly on where to position the aircraft attitude 

and thrust (as applicable). ’ 

- Two types of information should be provided on the forward display - 

66 
- Consideration must be given in the design of the guidance cue such that 

- A discussion occurred concerning the difference between guidance and 

8 satisfying the cue will not result in any extreme or hazardous flight condition. 

pathway information. It is entirely conceivable that guidance cues may lead 

the pilot away from the pathway, as in a brief ATC vector off course. One 

suggested philosophy was that a pathway be displayed when a route 

segment has been entered or computed in navigational planning systems (as 

in an FMS route in today’s systems). 

- One problem with pursuit guidance was discussed, in that during turns, this 

guidance will lead to flying to the inside of the turn, or cutting the corners. 

Two solutions to this problem were addressed: deliberately positioning the 

ghost aircraft to the outside of the turn by a programmed amount, or 

providing a second order correction to the position of the FPV on the display 

during turns. The latter method has the advantage of also providing a more 

accurate prediction of aircraft future position in turns, at the expense of a 

somewhat more active display cue, unless damping is included. 

- Critical guidance symbology, such as the velocity vector or the pursuit aircraft 

cue, should never be allowed to disappear off the edge of the display. Some 

method should be provided to indicate the extrapolated position of the cue, 

as well as the fact that the cue has pegged on the display. Methods which 

could be used include freezing the cue at the proper position on the display ( 

in a line to the actual position), flashing the cue, changing colors, hiding half 

or a part of the cue, or dotting the display lines constituting the cue. The 

method used for this study was to change the cue color to red. 

- Initially, the guidance cue changed from the pursuit aircraft to circular flight 

director cue at 200 ft agl. This change in symbology near to touchdown 

proved distracting, and the cue appearance was changed so that it remained 

as a “ghost aircraft” throughout the flare and touchdown. NASA Ames 

reported successful use of a shadow cue oriented around the ghost aircraft in 

the flare. We were not successful in this workshop, however, in 

implementing the shadow cue in any acceptable manner, as attempts 

resulted in a distracting, cluttered flare cue. 

- In a go-around, the “ghost aircraft” would disappear and only raw data would 

be available. The transition to raw data was abrupt and not desirable. The 

aircraft guidance logic should be expanded for full-mission. This should also 

include a readout of the guidance mode which the ghost aircraft is currently 

operating. Mode examples include approach, go-around, cruise, climb, 

descent, vertical nav climb/descent, VS, windshear escape, and engine out 

go-around. The pilot needs to know where the guidance is taking him and 

why. 

- The “guidance” should be consistent for all flight modes. For modes like 

heading hold/capture, altitude hold/capture, using a ghost aircraft displaced 

from the FPV to indicate guidance commands will appear to the pilot much 

like “chasing” the ghost aircraft down the pathway, even though the 

underlying “guidance algorithms” may be quite different. The area where 

1 

67 
there may be an inconsistency at present is when the aircraft is outside the 

pathway and on an intercept course. With the current algorithm, the ghost 

aircraft position is based on a perpendicular dropped from the ownship 

position to the pathway. In some ways this seems quite natural since you 

watch the ghost fly down the pathway and simply "fall in behind him". 

However, if you are in a heading hold mode flying an intercept path with 

respect to the pathway, the ghost should underlie the FPV if you are on the 

correct heading and it should then rovide transition guidance (onto the 

pathway) at the appropriate point. 

- If the ghost aircraft flies down the center of pathway, ownship tends to "cut" 

the corners. The algorithm has ghost aircraft fly outside of the pathway in 

turns so that ownship stays in the pathway. An alternate approach would be 

to have the ghost aircraft stay in the pathway (Le. not be compensated) and 

to track it with a "quickened" or acceleration compensated flight path symbol. 

This approach was not liked as well in a cursory evaluation ("too active"), but 

the implementation may not have been optimized. This approach may also 

pose problems when not flying chase or when trying to take crab out on 

landing. 

- Concern was expressed that the ghost aircraft was contributing too much 

visual clutter when flying the pathway, but was useful when acquiring the 

pathway. A compromise may be to show the ghost aircraft when outside the 

pathway and simple circle guidance cue when inside the pathway. 

- Lots of "white things" add up in the middle, make the ghost aircraft magenta. 

B 

4 

- The guidance symbology should track the flare cue once the flare cue 

- The algorithm for the positioning of the ghost aircraft needs to be determined 

becomes the valid command. 

for each sensor image FOV. 

17. Flight path acceleration symbol: No comments were noted. 

18. Augmented altitude tape: 

- In addition to the altitude information, provided by the moving-tape, precision 

altitude information is provided by the 'rotating-drum' (odometer-type) 

symbology centered vertically on the altitude tape. Additional altitude related 

information is provided (similar to MD-11 or B-777) including: radio altitude 

(analog) symbology, decision height, and altitude references. The entire set 

of additional information may not presented (or required) at one time. 

- The recommendation to replace the analog altitude symbology with a digitalreadout continues to be raised throughout all of the workshops. The intent of 

this replacement is to reduce display clutter on the XVS. Further analysis is 

required in this re ard since a significant amount of information is removed in 

this replacement. B 

68 
Symbology and XVS clutterhnterference: 

- Competition between symbology and background video: Haloing, using a 

thin black border encircling all the high priority symbology, is designed to 

allow for the primary symbols to be easily discerned, regardless of the 

intensity of the surround. Easy discrimination of symbology will become 

especially important when the pathway is overlaid on a field of video. Video 

presents a wide range of intensity and color patterns making a priori color 

and intensity selections of the pathway symbols difficult to do unless an 

occlusion method is used. Video, or a reasonable facsimile of it (perhaps 

photographically texture mapped terrain), is needed in future pathways 

experiments to adequately assess how the pathway will interact with the 

primary VMC sensor. There is also a major concern for eliminating or 

reducing the risk of obscuring objects that might otherwise lie hidden beneath 

the overlaying symbology. 

- The possibility for an additive or translucent method of annunciating the 

symbology should be explored so as to test for ways of minimizing the 

obscuration of objects residing beneath symbols. (Experiments that Russ 

Parrish did in this area some time ago showed that the underlying video and 

the symbol interfered with each other and both became difficult to "read".) 

These experiments were informally executed using the "golden eyeball" 

approach. It may be fruitful to investigate ways of overlaying symbols on 

sample fields of video using a more controlled and formal procedure. 

- One approach raised at this workshop regarding clutter/interference was, 

"How do HUDs in use today circumvent the problem?" The answer to that 

question may provide guidance here. 

- Note that in using an actual HUD, small head movements largely overcome 

this blocking issue through the effective use of parallax. * 

- Concern about occlusion/interference of symbols may require priority "no 

draw" zones around primary symbology. 

- Runway outline a la HUD: History of this was to give some sense of ground 

awareness, i.e. impending earth. This symbology should be removed at 50 ft 

altitude because it is important to break fixation. This symbology may also 

obscure runway edge lights (this was more of a simulator issue, because in 

the real world they never line up); many reasons why they don't quite line up 

with real world runway-heading errors are one. 

- Aircraft pitch symbol reference is a clutter issue when the aircraft is flying 

near zero an le of attack ( with zero AOA, the gull wing overlays the flight 

path vector). 

- The major issue is dealing with the clutter that results as everyone attempts 

to place "critical information" near the flight path vector. Some ideas to aid in 

decluttering were discussed (color coding, "no draw" zones, transparency), 

but each technique has advantages and drawbacks that need to be 

considered (e.g., see M. Johnson's comments on transparency). It might also 

help if pathway objects in this area were "in the world" to ameliorate "HUD 

3 

3 

4 

7 

69 
fixation." (Dave Foyle at Ames can provide some insight on this issue.) The 

overall response to pathway concepts was quite favorable (although some of 

the enthusiasm may reflect a "something is better than nothing bias"). The 

desire to extend pathways to non-CGI displays demonstrates this, but also 

raises new issues concerning visibility of non-pathway objects (e.g., runway 

incursions) via sensor/video imagery. Thus, the issue of clutter remains 

crucial. 

Other symbology options: 

- Speed error on the flight-path vector symbol: This is a vertical line 

(implemented but not shown in the example) on the left "wing" of the flightpath vector symbol. The length of the line is proportional to the speed error. 

- Roll limit indicator: Shows the current roll limit (g-load maneuver limit). See 

the MD-11 documentation for an example of this symbol. 

- Flare cue: A magenta line that appears at the bottom of the FOV at 100 feet 

(during landing) and rises proportional to altitude changes to meet the -3" 

pitch/flight-path reference at 50 feet. It will continue to rise and present the 

flare cue via an hdot/h flare law. 

- Pitch/flight-path reference symbol: A pitch/flight-path reference symbol for a 

3-degree approach angle is provided whenever a precision approach path is 

not provided. 

General symbology notes: 

- Meaning of pathway walls: What is the consequence of going outside the 

pathway - sometimes the meaning is trivial, but if the pathway is to avoid 

terrain, going outside could be catastrophic. On final approach, tying the 

pathway to the emerging "tunnel" certification criteria seems logical but 

further-out (from the airport) and enroute things are less clear. Flight 

corridors, e.g. across Atlantic, are set wide to account for navigation errors. 

- The pathway width should reflect what the pilot should stay within so that the 

sum of the path following errors and the navigation imprecision keeps the 

aircraft in the required corridor. 

- A meaningful distinction of pathway objects "in the world" and "tied to the 

aircraft" must be made. Objects "in the world" should have canonical 

geometric properties (e.g., expansion). 

From: Pathway Workshop Discussion Items, April 25-27, 1994. 

From: 2nd Interactive Workshop on Pathway Displays, September 1994. 

From: T.G. Sharpe, Notes on Pathway Displays September 1994 Workshop. 

From: Mary Kaiser, Notes on Pathway Displays September 1994 Workshop. 

1 

* From: Dave Hooper's Suggestions, September 9,1994. 

70 
From: Flight Test Symbology Workshop, March 21-22, 1995. 

From: ACWS Tuning Investigation, April 27, 1995. 

Editor’s comments. 

7 

71 
Workshop # 4 

September 4 - 5,1996 

Invitation to Workshop ## 4 

We are planning our fourth interactive workshop on synthetic displays for Sept. 4 - 5, 

1996. We anticipate beginning at 8 AM on Wednesday and winding up about 4 PM on 

Thursday. The idea is to have the participating pilots fly several symbology concepts and 

to have all participants make suggestions, which we will try to implement "then and 

there" so they could iteratively help us arrive at a better understanding of synthetic vision 

displays & symbologies. While Steve Williams is programming away, we would be 

discussing other display issues, such as HSCT display real estate usage, other flight phase 

displays (cruise, surface ops), etc. We intend to address the following issues: guidance 

concepts/guidance modes related to pathway displays; symbology concerns from the '95 

flight test (clutter, content, etc.); symbology requirements for the '96 flight test; 

autoflap/pitch changes during final approach; symbology concepts in general. 

We have invited the following participants: 

PATHWAY WORKSHOP INVITEES 

PILOTS 

BOEING 

Paul Leckman 

AMERICAN AIRLINES 

David Hooper 

NASA AMES 

Gordon Hardy 

DOUGLAS 

Mike Norman 

U. S. AIR 

Simon Lawrence 

NASA LANGLEY 

Rob Rivers 

FAA 

Rod Lalley 

RESEARCHERS 

Representatives from XVS, D&I, and GFC from Boeing, McDonnell Douglas, 

Honeywell, NASA Ames, and NASA Langley. 

Attendees 

NASA Ames: Gordon Hardy, Mary Kaiser, Chima Njaka 

NASA Langley: Steve Williams, Russ Parrish, Jeff Lavell, Bruce Jackson, Rob Rivers, 

Dave Raney, Mike Wusk, Ray Comstock 

72 
Boeing: Elfie Hofer, George Boucek, Paul Leckman 

Douglas: Mike Norman 

Honeywell: Andy Durbin, Tom Quinn, Thea Feyereisen 

Lockheed: Lou Glaab, Patricia Hunt 

Calspan: Paul Deppe 

Dynacs: Chuck Anderson 

American Airlines: David Hooper 

U. S. Air: Simon Lawrence 

Private Consultant, Purdue University (retired): Dean Nold 

USAF: Barry Bryant 

CSC: Trey Arthur 

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85 
Minutes from the Fourth XVS Symbology Workshop 

September 44,1996 

Summary: 

XVS and the Flight Deck Integrated Display Symbology Team, with representatives from 

D&I, GFC, and XVS, held the Fourth Symbology Workshop on September 4th and 5th. 

The workshop objectives were to examine and resolve the common use XVS symbology 

issues associated with the pilot-in-the-loop flight, ground, and simulation experiments for 

the flight deck program, to further explore critical XVS symbology issues (with emphasis 

on declutter techniques) and initiate within the group an exploration of surface operations 

symbology issues. The method of exploration and resolution was based solely on 

subjective evaluation and group discussion, with a recognized need for more formal 

determinations to proceed in a quantitative data gathering setting. 

In addition to a valuable exchange of freely-flowing information, with the main theme 

being that “less is best, least we obscure the rest (the visual scene and possible hazards)”, 

the team determined the minimum XVS symbology set to be used throughout the flight 

deck program, assuming the associated use of a head-down PFD. The team also selected 

additional symbologies that might be augmented to the XVS display in research 

explorations within the flight deck program, assuming that such research would pay a 

proper concern for clutter. 

Detailed Minutes: 

The workshop utilized the simulation capability assembled by Steve Williams. SGI 

Reality 2 computers were used to provide the XVS visual scene, the XVS symbology 

sets, and the head-down EFIS displays (PFD and Nav) to VISTAS. A generic transport 

model with HSCT-like properties was also implemented on the SGI equipment, with a 

make-shift autopilot interface necessitated by the failure of the AGCU. Heavy traffic 

around the airport approach area was provided to explore clutter concerns. 

The Minimum XVS Symbology Set 

(assuming the associated use of a head-down PFD) 

The team determined the minimum XVS symbology set to be used throughout the flight 

deck program, assuming the associated use of a head-down PFD. The minimum 

symbology set is documented in the following paper: 

86 
Fall 1996 XVS Workshop: 

Minimal HUD Symbology Set Definition 

Steve Williams 

Crew Vehicle Integration Branch 

NASA Langley Research Center 

September 11,1996 

87 
Symbology Elements 

The XVS Workshop Minimal HUD is a combination of 12 symbology elements as 

seen in Figure 1. In this depiction, all elements except element numbers 2, 3, 

and 4 are displayed with a contrast enhancement technique called 'haloing.' 

Haloing involves first drawing the element in black with a thick pen (3 or 4 pixels 

wide), and then in white (or the elements chosen color) in a thinner pen (1 or 2 

pixels wide). It is recommended that some contrast enhancing technique is used 

on all HUD elements. 

Figure 1. XVS Workshop Minimal HUD 

88 
1. Aircraft (pitch) symbol reference. 

This symbol represents the waterline of the aircraft, and in combination with the 

pitch ladder (element 2), indicates the current pitch angle of the aircraft. The 

symbol is a single V with wings and has a total width of 2.4 degrees and a height 

of 0.4 degrees. Each wing is 0.8 degrees in length. This symbol is fixed to the 

display surface (does not move) as the XVS system is attitude centered. 

2. Pitch Ladder. 

The Pitch Ladder consists of large (1.5 degrees wide) tick marks at 10 degree 

intervals and short (0.7 degrees wide) tick marks at 5 degree intervals. The 

outside edges of the ticks are aligned and the left side of the ladder is labeled. 

The outer sides of the ticks are 17 degrees apart. The pitch ladder slides left 

and right along the horizon so that the flight path vector symbol (element 10) is 

always in the center of the ladder. 

3. Horizon Line. 

The horizon line extends across the display at the 0 degree point of the pitch 

ladder. The horizon line has a 4 degree gap centered around the flight path 

vector symbol (element 10). 

4. Compass Heading Numbers and Ticks. 

Along the horizon line (element 3), there are compass ticks every 5 degrees. 

Every ten degree tick is labeled. The 5 degree ticks are 0.3 degrees tall and the 

10 degree ticks are 0.4 degrees tall. The heading numbers are centered above 

the ticks and are 0.5 degrees in height. Heading numbers and ticks are clipped 

out of (not drawn) in a region that is +- 1 .O degree on either side of the center of 

the horizon line gap (element 3). NOTE: The 80 degree heading indication and 

tick mark in Figure 1 are incorrectly displayed. 

5. Barometric Altitude. 

The center of the barometric altitude numeric readout is located 4.5 degrees to 

the right and 2.0 degrees down from the center of the flight path vector symbol 

(element 10). This symbol moves with the flight path vector symbol and pegs on 

the edges of the display. The barometric altitude numerical readout is 0.75 

degrees in height and the value is truncated to 20 foot increments. The digits roll 

as they change, rather than discretely incrementing. 

6. Radar Altitude. 

The center of the radar altitude numeric readout is located 4.5 degrees to the 

right and 3.2 degrees down from the center of the flight path vector symbol 

89 
(element 10). This symbol moves with the flight patch vector symbol and pegs 

on the edges of the display. Four dashed lines ('I- - - -'I) are displayed when the 

radar altitude is invalid (above 2500 feet AGL). The radar altitude is truncated to 

10 foot increments above 50 feet, 5 foot increments above 10 feet and below 50 

feet, and 1 foot increments below 10 feet. The radar altitude is adjusted to read 

'0' at main gear touch down at a nominal flare attitude. The radar altitude 

numeric readout is 0.7 degrees in height. The letters 'RA' are displayed next to 

the radar altitude numeric readout at all times (even when dashed). The digits 

roll as they change, rather than discretely incrementing. 

7. Landing Phase Radar Altitude. 

At 500 feet AGL, the LAnding PHasE Radar ALTitude (LAPHER ALT) numeric 

readout appears. Once the LAPHER ALT is displayed, the radar altitude must 

ascend above 550 feet AGL before it is removed. The readout is located 3.0 

degrees down from the flight path vector symbol (element 10) and is 0.85 

degrees in height. The LAPHER ALT moves with the flight path vector symbol 

and pegs on the edges of the display. The digits roll as they change, rather than 

discretely incrementing. 

8. Indicated Airspeed. 

The indicated airspeed is located 4.5 degrees to the left and 2.0 degrees down 

from the center of the flight path vector symbol (element 10). This symbol 

moves with the flight path vector symbol and pegs on the edges of the display. 

The indicated airspeed numerical readout is 0.75 degrees in height and the 

value is truncated to 1 knot increments. The digits roll as they change, rather 

than discretely incrementing. 

9. Flight Guidance. 

One of three types of flight guidance will be provide. 

1) Traditional Flight Director guidance where a single circle is displayed (0.4 

degrees diameter) in magenta indicating directly the amount of pitch and roll 

suggested. The pilots task is to position the flight path vector symbol (element 

10) so that the flight director guidance circle is center in the flight path vector 

circle. 

2) Ghost Aircraft Pursuit guidance where a ghost aircraft symbol is displayed 

according to the principles and guidelines suggested in NASA TM-104027 

"Some VTOL Head-Up Display Drive-Law Problems and Solutions" (1 993) by 

Merrick. The ghost lead time used for HSR approaches varies from 15 seconds 

to 5 seconds based on the following equation: 

ghost lead time = (Rad Alt)/50.0 

if (ghost lead time > 15.0) ghost lead time = 15.0 

if (ghost lead time c 5.0) ghost lead time = 5.0 

90 
The geometric description of the ghost aircraft is described in NASA TM-102216 

"A Head Up Display for Application to V/STOL Aircraft Approach and Landing" 

(1 990) by Merrick, Farris, and Vanags. The ghost is displayed in magenta and 

the 'XI symbol for the beacon has been replaced by a circle 0.4 degrees in 

diameter. 

3) 3 Degree Flight Path Reference Line which is displayed at a constant 3 

degrees down from the horizon line (element 3). This symbol is a white dashed 

line that is 15 degrees wide and has a 3.0 degree gap in the center. The 3 

degree flight path reference line slides left and right with the flight path vector 

symbol (element 10) so that the flight path vector symbol is always center in the 

gap. The 3 degree flight path reference line is always parallel to the horizon line. 

10. Flight Path Vector. 

The Flight Path Vector symbol is made up of four sub elements as seen in figure 

2. The first element (1) is the flight path vector symbol itself. This element 

consists of a circle 1 .O degree in diameter, two horizontal wings 1 degree in 

length on each side, and one vertical tail 0.6 degrees tall. The center of the 

circle indicates the inertial flight path of the aircraft (track angle and gamma). 

The second element (2) is a side slip/skid indicator. The slip/skid flag grows in 

the direction of the rudder correction required. The third element (3) is a speed 

error tape. This tape indicates relative error to the commanded airspeed. If the 

tape is above the wing, the aircraft is faster than the commanded airspeed. The 

tape grows below the wing to indicate that the aircraft is to slow. The tape is 

scaled such that 1 degree of tape indicates a 20 knot speed error. The fourth 

element (4) is an x-body axis acceleration indication. If the carrot is above the 

wing, the aircraft is accelerating. If the carrot is below the wing, the aircraft is 

decelerating. The acceleration carrot is scaled such that a 1 degree deviation 

from the wing indicates 2 feet/second/second acceleration. 

Figure 2. Flight Path Vector Symbol 

o/ 0 +\ 

1 I 

I 

\ I '. 0 

Figure 2. Flight Path Vector Symbol 

91 
11. Roll Scale. 

The roll scale is a collection of tick marks nominally indicating 0, +- 10, +- 20, 

and +- 30 degrees of bank angle. The 0 and +- 30 degree indications are long 

tick marks (0.5 degrees in length), and the +- 10 and the +- 20 degree indications 

are short tick marks (0.25 degrees in length). If the aircraft bank angle exceeds 

35 degrees, +- 45 degree ticks (short) and +- 60 degree ticks (long) are drawn. 

The bottom of the 0 degree roll tick mark is 11.75 degrees from the center of the 

display. 

12. Roll Indicator. 

The roll indicator symbol is a triangle that moves along the bottom of the roll 

scale (element 11) to indicate current bank angle. The indicator is triangle that 

has a base length of 0.5 degrees and a height of 0.75 degrees. Side Slip/Skid is 

indicated by a rectangle attached to the bottom of the roll indicator. The 

rectangle is 0.15 degrees tall and moves in the direction of rudder correction 

required. 

92 
Selected Additional Symbologies 

(possible exploratory augmentations to the XVS display) 

The team selected additional symbologies that might be augmented to the XVS 

display in research explorations within the flight deck program, assuming that 

such research would pay a proper concern for clutter. The symbology elements 

are intended to be pilot selectable and, in some cases, to utilize intelligent 

automatic declutter techniques. The elements are merely listed here without any 

discussion or description, although a few are accompanied with parenthetical 

notes. 

1. Raw Data 

2. Pathways 

3. Wireframe of Active Runway with Extended Centerline 

4. Airport Wireframes (runways, taxiways) 

5. Terrain Lines (possibly for low visibility operations) 

6. Perspective Waypoints 

7. Marker Beacons 

8. Touchdown Zone/Aim Point 

9. Distance To Go/ Runway Remaining 

10. Decision Height 

1 1. Vertical Speed IndicatorNertical Accleration 

12. Pitch Limiting/Roll Limits 

13. Flight Mode Annuciation 

14. Digital Heading 

15. Wind Direction (only below 500 ft ?) 

16. Windshear 

17. Ground Prox 

18. System Messages/Allerts 

19. Center Heading # (because of gap in Minimum set heading tape) 

20. Commanded Heading, Course, Altitude, Speed 

21. Crab lnidicator ( tried line connecting pitch reference symbol [symbol # 1 in 

22. Surveillance Symbols (TCAS, radar, object detection, ADS, ASDE, etc.) 

minimum set figure] and flight path vector symbol [#IO]) 

93 
Surface Operations Symbology Issues 

Mary Kaiser described the initial efforts within XVS to identify surface operations 

symbology issues and the initial sets assembled to date. The material can be 

found in detail in the XVS product G4. “Initial Surface Operations Symbology Set 

Definition Document”. M. K. Kaiser and Walter W. Johnson, NASA Ames 

Research Center, September 25, 1996. 

The two symbology sets described included removal of the horizon line, a 

vertically displaced heading tape, digital readouts of ground speed with an 

acceleration/deacceleration carrot, a digital readout of thrust, alpha numeric 

routing information, and a ground track path for the airplane nose that would lead 

the gear-pivot-point down the taxiway centerline. Discussions covered means of 

removal of the horizone line after touchdown for rollout and taxi, and 

replacement of the horizon line for takeoff; the desirability/availablity of taximaps, 

airport databases; tail camera views; multiview displays; spot cameras; and other 

less-specific symbology issues. 

Pathway Issues 

What is a pathway? 

- prospective or actual cleared ground path (lateral, and/or vertical) 

Purpose of a pathway? 

- Provide Think Ahead Information 

- Provide Corridor Representation 

- Provide Situation Awareness Enhancement 

When should a pathway be displayed? 

- always 

- never 

- selectable 

- only when a defined ground path clearance exists (i.e., cleared direct, 

cleared on route, cleared for approach, FMS has 2-D path info, FMS has 

3-D path info, etc) 

problems with heading clearances, lateral only clearances, above 

or below clearances 

When should a pathway not be displayed? 

- no ground-based constraints 

- pathway would conflict with guidance information 

- pilot decision 

94 
How should a pathway be displayed? 

- color 

- dimensions (RNP?) 

Pathway Considerations 

- Path discontinuities 

- ATC Radar vectors/Heading Courses 

- Climb/cruise/descend phases 

- Emergency path revisions 

- Levels of Constrains (2-D, 3-D) 

- TOGAPath 

- Multi-Paths (non-active paths) 

Guidance/Flight Path Vector Discussion 

Guidance Discussion 

What type of guidance? 

- flight director (circle, cross hairs, etc) 

- pursuit “follow-me aircraft” 

- always (what happens when pegged?) 

- when near desired path (tolerance?) 

- when selected 

How to display 

- color 

- changes with flight phase (transition) 

- display control laws 

When to display? 

Flight Path Vector Discussion 

0 Commanded gamma versus actual gamma 

Actual gamma 

0 lags somewhat in HSCT class aircraft 

0 accurate in all phases 

0 follows control inputs more closely 

0 better with large inputs up and away (i.e., go-around, 

maneuvering) 

0 problems in flare 

Commanded gamma 

0 Problem: what to display when actual and commanded gamma 

differ? 

0 “ghost” gamma 

0 actual gamma 

commanded gamma 

95 
Decl utter Techniques Discussion 

Potential decluttering methodologies: 

- color coding 

- “no draw” zones (occlusion) 

- transparency 

- stereo symbology, non-stereo scene behind 

- crossed disparity stereo 

- head tracked symbology 

- move symbols away from flight path 

- auto switching logic 

functional need 

phase of flight 

manual switching 

Declutter Techniques Demonstrated: 

- color coding 

- transparency 

- non-head tracked stereo symbology 

- move symbols away from flight path 

- auto switching logic 

functional need 

phase of flight 

manual switching 

- auto declutter implemented 

display airspeed tape if: 

knots or more. 

1) If there is a commanded airspeed and current airspeed is off by 5 

- or - 

2) If there is a commanded acceleration and current acceleration is 

- or - 

3) If there isn’t a commanded acceleration and the absolute value of 

- or - 

4) A new commanded airspeed is entered. (by FMC or pilot) 

- or - 

5) If there is a new auto pilot pre-select airspeed entered (the 

- or - 

6) The airspeed is less than or equal to Vmin. 

- or - 

7) It has been less than 5 seconds since any of the above has 

off by 1 knot per second or more. 

the current acceleration if greater than 2.5 knots per second. 

airspeed select dial was turned on the AGCU). 

occured. 

96 
display altitude tape if: 

50 feet or more. 

1) If there is a commanded altitude and the current altitude is off by 

- or - 

2) If there is a commanded vertical airspeed and the current vertical 

- or - 

3) If there isn't a commanded vertical airspeed and the absolute 

airspeed is off by 150 feet per minute or more. 

value of the current vertical airspeed is greater than 2000 feet per 

minute. 

- or - 

4) A new commanded altitude is entered. (by FMC or pilot) 

- or - 

5) If there is a new auto pilot pre-select altitude entered (the altitude 

select dial was turned on the AGCU). 

- or - 

6) The radar altitude is lees than 250 feet. 

- or - 

7) It has been less than 5 seconds since any of the above has 

occu red. 

Other Notes 

1. Consider replacing current pathway billboards with DTG readout 

2. To drive the slideslip indicator (symbol # 2 on velocity vector symbol #lo in 

minimum set description document), use p (beta), not ay (lateral acceleration) 

for HSCT. 

97 
Post Workshop 

Following the four Pathway Workshops, the consensus pathway symbology was utilized 

in an XVS/GFC TIFS flight test as defined in Randy Bailey's version of the Steve 

Williams document, which follows: 

Fall 1996 XVS Workshop 

Minimal HUD Symbology Set Definition 

Modifications for TIFS.3IFU Flight Test 

Steve Williams 

Crew Vehicle Integration Branch 

NASA Langley Research Center 

with modifications proposed by Randy Bailey 

September 11,1996 

Modifications: 19 Sept 1998 

98 
I 

Introduction 

A flight test will be conducted in the Fall of 1998 using the USAF Total In-Flight 

Simulator (TIFS) aircraft for the NASA High Speed Research (HSR) program. This 

flight test will be a synergistic evaluation of both Guidance and Flight Control (GFC) and 

external Visibility System (XVS) program elements. A common symbology set is 

proposed to simplify the TIFS set-up, minimize pilot training, and prevent XVS and GFC 

program element requirements from diverging. The basis for this common symbology set 

is the "XVS Minimal Symbology Set Definition" developed in a Fall 1996 XVS 

workshop. Modifications to this minimum set are proposed herein for the TIFS.3FI-4 

flight test. 

A ShibaSoku High Definition Television (HDTV) monitor will be used as the Primary 

XVS Display (PXD) for the TIFS.3FI-4 flight test. The anticipated field-of-view (FOV) 

is sketched in Figure 1. The HDTV monitor will be located in the cockpit such that an 

approximate 2 degree asymmetry in field-of-regard will be achieved. The total vertical 

FOV will be approximately 26' with 15.1' of that FOV in the nose down direction. At 

the nominal 1 1.4' approach angle-of-attack and on a 3' glideslope, approximately 4.7' 

will be viewable in the HDTV monitor below the TIFS flight path. 

4: -44 deg H FOV 

-26 deg V FOV 

Vertical Field-of- View 

7.4 deg 15.1 deg 

'I 

V 

BIB 

Figure 1. TIFS.3m4 PXD Field-of-View 

Symbology Elements 

The XVS Workshop Minimal HUD is a combination of 12 symbology elements as seen 

in Figure 2. In this depiction, all elements except element numbers 2,3, and 4 are 

displayed with a contrast enhancement technique called 'haloing.' Haloing involves first 

drawing the element in black with a thick pen (3 or 4 pixels wide), and then in white (or 

the elements chosen color) in a thinner pen (1 or 2 pixels wide). It is recommended that 

some contrast enhancing technique is used on all HUD elements. In addition, it may be 

necessary to increase the pen size, enhance the haloing, or change the coloration on the 
symbology elements to ensure readabilityflegibility of the symbology for the TIFS.3FL4 I flight test. 

Modifications to this minimal symbology set for the TIFS.3FL4 flight test are presented 

in the following. In addition, elements 13 through 17 have been added to the minimal 

symbology set but are not shown on Figure 1. 

I 

Figure 2. XVS Workshop Minimal HUD 

1. Aircraft (pitch) symbol reference. 

This symbol represents the waterline of the aircraft, and in combination with the pitch 

tape (element 2), indicates the current pitch angle of the aircraft. The symbol is a single 

V with wings and has a total width of 2.4 degrees and a height of 0.4 degrees. Each wing 

100 
is 0.8 degrees in length. This symbol is fixed to the display surface (does not move) as 

the XVS system is attitude centered. 

2. Pitch Tape. 

The Pitch Tape consists of large (1.5 degrees wide) tick marks at 10 degree intervals and 

short (0.7 degrees wide) tick marks at 5 degree intervals. The outside edges of the ticks 

are aligned and the left side of the tape is labeled. The outer sides of the ticks are 17 

degrees apart. The pitch tape slides left and right along the horizon so that the flight path 

vector symbol (element 10) is always in the center of the tape. 

3. Horizon Line. 

The horizon line extends across the display at the 0 degree point of the pitch tape. The 

horizon line has a 4 degree gap centered around the flight path vector symbol (element 

10). 

4. Compass Heading Numbers and Ticks. 

Along the horizon line (element 3), there are compass ticks every 5 degrees. Every ten 

degree tick is labeled. The 5 degree ticks are 0.3 degrees tall and the 10 degree ticks are 

0.4 degrees tall. The heading numbers are centered above the ticks and are 0.5 degrees in 

height. Heading numbers and ticks are clipped out of (not drawn) in a region that is +- 

1 .O degree on either side of the center of the horizon line gap (element 3). NOTE: The 

80 degree heading indication and tick mark in Figure 1 are incorrectly displayed. 

5. Barometric Altitude. 

The center of the barometric altitude numeric readout is located 4.5 degrees to the right 

and 2.0 degrees down from the center of the flight path vector symbol (element 10). This 

symbol moves with the flight path vector symbol and pegs on the edges of the display. 

The barometric altitude numerical readout is 0.75 degrees in height and the value is 

truncated to 20 foot increments. 

6. Radar Altitude. 

The center of the radar altitude numeric readout is located 4.5 degrees to the right and 3.2 

degrees down from the center of the flight path vector symbol (element IO). This symbol 

moves with the flight patch vector symbol and pegs on the edges of the display. It is 

displayed only when radar altitude is less than 2500 ft and more than 1000 ft. Four I 

101 
dashed lines ('I- - - -'I) are displayed when the radar altitude is invalid below 2500 feet 

AGL. The radar altitude is truncated to 10 foot increments. The radar altitude numeric 

readout is 0.7 degrees in height. The letter 'R' are displayed next to the radar altitude 

numeric readout at all times (even when dashed). 

7. Landing Phase Radar Altitude. 

At 1000 feet AGL, the LAnding PHasE Radar ALTitude (LAPHER ALT) numeric 

readout appears. Once the LAPHER ALT is displayed, the radar altitude must ascend 

above 1050 feet AGL before it is removed. The readout is located 3.0 degrees down from 

the flight path vector symbol (element 10) and is 0.75 degrees in height. The LAPHER 

ALT moves with the flight path vector symbol and pegs on the edges of the display. The 

radar altitude is in 10 ft increments above 500 ft. 1 ft increments are used below 500 ft. 

8. Indicated Airspeed. 

The indicated airspeed is located 4.5 degrees to the left and 2.0 degrees down from the 

center of the flight path vector symbol (element 10). This symbol moves with the flight 

path vector symbol and pegs on the edges of the display. The indicated airspeed 

numerical readout is 0.75 degrees in height and the value is truncated to 1 knot 

increments. 

9. Flight Guidance. 

1 ' Guidance will not be provided in the TIFS.3IFLA flight test with the exception that a 

Glidepath Reference Line will be displayed when the the "landing mode" configuration 

has been selected. The Glidepath Reference Line will be drawn to a constant value 

(appropriate for the landing runway) down from the horizon line (element 3). This 

symbol is a white dashed line has a 3.0 degree gap in the center. 3 dashes, each 1 degree 

in length separated by 1 degree gaps, are displayed left and right of the flight path vector 

symbol. The Glidepath Reference Line slides left and right with the flight path vector 

symbol (element 10) so that the flight path vector symbol is always center in the gap. The 

Glidepath Reference Line is always parallel to the horizon line. 

~ 

~ 

10. Flight Path Vector. 

I The Flight Path Vector symbol is made up of five sub elements as seen in Figure 3. The 

first element (1) is the flight path vector symbol itself. This element consists of a circle 

1 .O degree in diameter, two horizontal wings 1 degree in length on each side, and one 

vertical tail 0.6 degrees tall. The center of the circle is driven in elevation from the 

gamma-dot/v control law. Above 500 ft radar altitude, the symbol represents the 

I 

1 02 
commanded vertical flight path angle (yc). Below 500 ft, the symbol is a quickened or 

blended combination of actual flight path (y) and commanded flight path (yJ. In azimuth, 

the symbol always represents the aircraft's ground track. The second element (2) is a side 

slip/skid indicator. The slip/skid flag grows in the direction of the rudder correction 

required. The third element (3) is a speed error tape. This tape indicates relative error to 

the commanded airspeed. If the tape is above the wing, the aircraft is faster than the 

commanded airspeed. The tape grows below the wing to indicate that the aircraft is too 

slow. The tape is scaled such that 1 degree of tape indicates a 20 knot speed error. The 

fourth element (4) is an indication of the acceleration along the flight path. This symbol 

is driven from the gamma-dotlv control law. If the carrot is above the wing, the aircraft is 

accelerating. If the carrot is below the wing, the aircraft is decelerating. The acceleration 

carrot is scaled such that a 1 degree deviation from the wing indicates 1 ktdsecond 

acceleration. The fifth element (5) is the actual flight path reference symbol. This 

"ghosted" flight path marker is displayed if the actual and commanded flight path deviate 

by greater than a preset value and duration. These magnitude and persistence values are 

contained in the gamma-dotlv control law. The symbol will be a dashed circle, I degree 

in diameter, of a magenta color. 

2 1 

Figure 3. Flight Path Vector Symbol 

11. Roll Scale. 

The roll scale is a collection of tick marks nominally indicating 0, +- 10, +- 20, and +- 30 

degrees of bank angle. The 0 and +- 30 degree indications are long tick marks (0.5 

degrees in length), and the +- 10 and the +- 20 degree indications are short tick marks 

(0.25 degrees in length). If the aircraft bank angle exceeds 35 degrees, +- 45 degree ticks 

(short) and +- 60 degree ticks (long) are drawn. The bottom of the 0 degree roll tick mark 

is 10.0 degrees from the center of the display. 

I 

103 
12. Roll Indicator. 

The roll indicator symbol is a triangle that moves along the bottom of the roll scale 

(element 1 I) to indicate current bank angle. The indicator is triangle that has a base 

length of 0.5 degrees and a height of 0.75 degrees. Side Slip/Skid is not indicated. , 

The aircraft magnetic heading will be digitally displayed 1.5 degrees below and centered 

in azimuth about the 0 degree roll scale indication. The numerics will be 0.5 degrees in 

height. Leading zeros will be used to provide three digit read-out at all times. 

14. Flare Cue. 

1 The flare cue (Figure 4) consists of four line segments each 1 degree in length. The 

vertical position of the symbol is driven from a gamma-dot/v control law command 

output. The azimuth position of the symbol is the same as the flight path vector azimuth 

position. A nominal separation of 10 pixels is planned between vertical line pairs. 

~ 1 deg ~: 1 deg =t: 1 deg >I 

- ,I, 10 pixels 

f 

Figure 4. Flare Cue Symbol 

15. Glideslope and Localizer. 

Raw glideslope and localizer data will be provided when the "landing mode" 

configuration has been selected. Deviation will be shown in dots with a rectangle 

denoting zero deviation and two dots displayed at all times on either side of the zero 

deviation rectangle. A diamond symbol will indicate the deviation as a "fly-to" reference. 

The glideslope indicator is a scale consisting of four circles (0.2 degrees in diameter) 

vertically separated by 1 .O degree increments about a center rectangle (0.2 degrees in 

width, 0.1 degrees in height). The indicator elements are laterally centered. The 

glideslope indicator is a diamond (outline) that is 0.4 degrees tall and 0.4 degrees wide. 

The center point definition of the glideslope indicator element is given as the middle of 

the center rectangle. 
The localizer indicator is a scale consisting of four circles (0.2 degrees in diameter) 

horizontally spaced in 1 .O degree increments about a center rectangle (0.2 degrees in 

height, 0.1 degrees in width). The indicator elements are vertically centered The localizer 

indicator is a diamond (outline) that is 0.4 degrees tall and 0.4 degrees wide. The center 

point definition of the glideslope indicator element is given as the middle of the center 

rectangle. 

The glideslope and localizer indicators will be positioned as a group. The nominal 

position for the glideslope indicator will be 10.0 degrees to the right and 7.5 degrees 

below the pitch reference symbol. The nominal position for the localizer indicator will be 

15.0 degrees below the pitch reference symbol. The positions of these indicators may 

change depending upon the flight path vector symbol location. Unless the glideslope 

indicator is at the right field-of-view limit of the display, the glideslope indicator will 

never be positioned less than 7 degrees nor greater than 14 degrees from the flight path 

vector symbol. When the position of the glideslope indicator is changed, the localizer 

indicator will move proportionally to maintain its spatial relation to the glideslope 

indicator. Similarly, unless the localizer is at the bottom field-of-view limit of the 

display, the localizer indicator will never be less than 5 degrees nor greater than 7.5 

degrees from the flight path vector symbol. When the position of the localizer indicator 

is changed, the glideslope indicator will move proportionally to maintain its spatial 

relation to the localizer indicator. 

16. Wind Indicator. 

The wind indicator symbol consists of an arrow pointed in the direction of the wind 

vector and a digital readout showing the wind speed (or total magnitude of the wind 

vector). The center of the wind indicator (arrow and digital readout) is located 1 1.5 

degrees to the right and 9.75 degrees above the center of the display and is fixed to the 

display. The arrow is 1.1 degrees long. The shaft is 1.5 degrees long and the head is 0.3 

degrees wide and 0.6 degrees tall. The numeric readout is 0-.5 degrees tall. 

17. Time Code and Event Marker. 

A digital numeric display will show the current time broadcast over the data bus to the 

PXD and associated XVS processing elements. This display will include: 1) date and, 2) 

time resolved to the tenth of seconds. Further, a rectangular box will be drawn around the 

time code when an event mark has been triggered. The numeric readout will be 0.5 

degrees in height. 

1 05 
Concluding Remarks 

The series of interactive workshops held at Langley to investigate tunnel-, pathway- or 

highway-in-the-sky concepts produced valuable discussion material, several promising 

techniques for effective pathway symbology manipulation, a consensus pathway concept 

for XVS application, and freely available graphics software that rendered the several 

different pathway concepts. Both the ideas and the actual distributed graphics software 

have been acknowledged by many as having been a major influence in renewed interest in 

this area of advanced symbology for enhanced situation awareness and precise flight 

guidance. The success of these workshops can only be attributed to the contributions of 

the government and industry display designers, test pilots, and airline pilots who 

participated, and to the Langley staff (particularly the graphics software virtuoso Steve 

Williams) that enabled the fly-and-discuss (in an iterative manner) environment. Special 

acknowledgements are made to Terry Abbott, Steve Williams, Mike Norman, Dave 

Hooper, Mike Johnson, Tom Sharpe, Mary Kaiser, Randy Harris, and Randy Bailey for 

some of the written material used above. 

106 
1 I Form Approved REPORT DOCUMENTATION PAGE OMB NO 0704-0188 

1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED 

March 2003 Conference Publication 

6. AUTHOR(S) 

Russell V. Parrish. Compiler 

I 

11. SUPPLEMENTARY NOTES 

12a. DlSTRlBUTlONlAVAlLABlLlTY STATEMENT 12b. DISTRIBUTION CODE 

Unclassified-Unlimited 

Subject Category OS Distribution: Nonstandard 

Availability: NASA CAS1 (30 1 ) 62 1-0390 

In 1994-96. Langley Research Center held a series of interactive workshops investigating highway-in-the-sky 

concepts, which enable precise flight path control. These workshops brought together government and industry 

display designers and pilots to discuss and fly various concepts in an iterative manner. The primary emphasis of 

the first workshops was the utility and usability of pathways and the pros and cons of various features available. 

The final workshops were focused on the specific applications to the external Visibility System (XVS) of the 

NASA High-speed Research Program, which was concerned with replacement of the forward windows in a 

High-speed Civil Transport with electronic displays and high resolution video cameras to enable a “No-Droop” 

configuration. The primary concerns in the XVS application were the prevention of display clutter and 

obscuration of hazards, as the camera image was the primary means of traffic separation in clear visibility 

conditions. These concerns were not so prominent in the first workshops, which assumed a Synthetic Vision 

System application in which hazard locations are known and obscuration is handled easily. The resulting 

consensus concept has been used since in simulation and flight test activities of many Government programs. 

and other concepts have been influenced by the workshop discussions. 

13. ABSTRACT (Maximum 200 words) 

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 

NASA Langley Research Center 

Hiimpton. VA 2368 1-2 199 

9. SPONSORlNGMONITORlNG AGENCY NAME(S) AND ADDRESS(ES) 

National Aeronautics and Spacc Administration 

Washington, DC 20546-000 I 

14. SUBJECT TERMS 

Tunnel-in-the-sky; Pathway-in-the-sky; Highway-in-the-sky; Pictorial displays; 

Synthetic Vision System 

17. SECURITY CLASSIFICATION 18. SECURITY CLASSlFlCATlON 19. SECURITY CLASSIFICATION 

OF REPORT OF THIS PAGE OF ABSTRACT 

Unclassified Unclassified Unclassified 

5. FUNDING NUMBERS 

728-60- 10-0 1 

15. NUMBER OF PAGES 

114 

16. PRICE CODE 

20. LIMITATION 

OF ABSTRACT 

UL 

8. PERFORMING ORGANIZATION 

REPORT NUMBER 

L- I8270 

10. SPONSORING/MONITORING 

AGENCY REPORT NUMBER 

NASA/CP-2003-212 164