sufficient accuracy for the intended function. When numeric readouts are used in conjunction with scales, they should be located close enough to the scale to ensure proper association, yet not detract from the interpretation of the graphic or the readout.
5.7.3.3 Delimiters, such as tick marks, should allow rapid interpretation without adding unnecessary clutter. Markings and labels should be positioned such that their meaning is clear yet they do not hinder interpretation. Pointers and indexes should not obscure the scales or delimiters such that they can no longer be interpreted. Pointers and indexes should be positioned with sufficient accuracy for their intended function. Accuracy includes effects due to data resolution, latency, graphical positioning, etc.
5.7.4 Other Graphical Depictions.
Depictions include schematics, synoptics, and other graphics such as attitude indications, moving maps, and vertical situation displays.
5.7.4.1 To avoid visual clutter, graphic elements should be included only if they add useful information content, reduce flightcrew access or interpretation time, or decrease the probability of interpretation error.
5.7.4.2 To the extent it is practical and necessary, the graphic orientation and the flightcrew’s frame of reference should be correlated. For example, left indications should be on the left side of the graphic, and higher altitudes should be shown above lower altitudes.
5.7.4.3 If there are multiple depictions, such as “thumbnail” or overlayed depictions, the orientation (for example, heading up, track up, North up, etc.) should be the same for each depiction. This does not apply to other systems where the captain and first officer may select different presentations of the same information and are used exclusively by that flightcrew member.
5.7.4.4 Graphics that include three-dimensional effects, such as raised buttons or the airplane flight path in a perspective view, should ensure that the symbol elements used to achieve these effects will not be incorrectly interpreted.
5.8 Color Coding.
5.8.1 If color is used for coding, at least one other distinctive coding parameter should be used (for example, size, shape, location, etc.). Normal aging of the eye can reduce the ability to sharply focus on red objects, or discriminate blue from green. For pilots with such a deficiency, display interpretation workload may be unacceptably increased unless symbology is coded in more dimensions than color alone. However, the use of 5-7
color alone for coding information has been shown to be acceptable in some cases, such as weather radar and terrain depiction on the lateral view of the navigation display.
5.8.2 To ensure correct information transfer, the consistent use and standardization of color is highly desirable. In order to avoid confusion or an interpretation error, there should not be a change in how the color is perceived over all foreseeable conditions. Colors used for one purpose in one information set should not be used for an incompatible purpose that could create a misunderstanding within another information set. In particular, consistent use and standardization for red and amber or yellow, in accordance with § 25.1322, is required to retain the effectiveness of flightcrew alerts. A common application is the progression from green to amber to red, representing increasing degrees of threat, potential hazard, safety criticality, or need for flightcrew awareness or response. Inconsistencies in the use of color should be evaluated to ensure that they are not susceptible to confusion or errors, and do not adversely impact the intended function of the system(s) involved.
5.8.3 If color is used for coding, it is considered good practice to use six colors or less for coding parameters. Each coded color should have sufficient chrominance separation so it is identifiable and distinguishable in all foreseeable lighting and operating conditions and when used with other colors. Colors should be identifiable and distinguishable across the range of information element size, shape, and movement. The colors available for coding from an electronic display system should be carefully selected to maximize their chrominance separation. Color combinations that are similar in luminance should be avoided (for example, navy blue on black or yellow on white).
5.8.4 Other graphic depictions such as terrain maps and synthetic vision presentations may use more than six colors and use color blending techniques to represent colors in the outside world or to emphasize terrain features. These displays are often presented as background imagery and the colors used in the displays should not interfere with the flightcrew interpretation of overlaid information parameters as addressed in paragraph 5.8.5 of this chapter.
5.8.5 Table 5-1 depicts previously accepted color coding and the functional meaning associated with each color. The use of these colors is recommended for electronic display systems with color displays.
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Table 5-1. Recommended Colors for Certain Functions Feature Color Warnings Red Flight envelope and system limits, Red or Yellow/Amber as appropriate exceedances (see above) Cautions, non-normal sources Yellow/Amber Scales, dials, tapes, and associated White1 information elements Earth Tan/Brown Sky Blue/Cyan Engaged modes/normal conditions Green Instrument landing system deviation pointer Magenta Divisor lines, units, and labels for inactive Light gray soft buttons 1 Use of the color green for tape elements (for example, airspeed and altitude) has also been found acceptable if the color green does not adversely affect flightcrew alerting.
5.8.6 Table 5-2 depicts display features that should be allocated a color from either Color Set 1 or Color Set 2.
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Table 5-2. Specified Colors for Certain Display Features Display Feature Color Set 1 Color Set 2 Fixed reference symbols White Yellow1 Current data, values White Green Armed modes White Cyan Selected data, values Green Cyan Selected heading Magenta2 Cyan Active route/flight plan Magenta White 1 Use of the color yellow for functions other than flightcrew alerting should be limited and should not adversely affect flightcrew alerting.
2 In Color Set 1, magenta is intended to be associated with those analog parameters that constitute “fly to” or “keep centered” type information.
5.8.7 The following color pairs should be avoided:
• Saturated red and blue.
• Saturated red and green.
• Saturated blue and green.
• Saturated yellow and green.
• Yellow on purple.
• Yellow on green.
• Yellow on white.
• Magenta on green.
• Magenta on black (although this may be acceptable for lower criticality items).
• Green on white.
• Blue on black.
• Red on black.
Note: For further information on this subject, see FAA Report No. DOT/FAA/CT 03/05 HF-STD-001, Human Factors Design Standard (HFDS): For Acquisition of Commercial Off-the-Shelf Subsystems, Non-Developmental Items, and Developmental Systems.
5.8.8 When background color is used (for example, gray), it should not impair the use of the overlaid information elements. Labels, display-based controls, menus, symbols, and graphics should all remain identifiable and distinguishable. The use of background color 5-10
should conform to the overall flight deck philosophies for color usage and information management. If texturing is used to create a background, it should not result in loss of readability of the symbols overlaid on it, nor should it increase visual clutter or pilot information access time. Transparency is a means of seeing a background information element through a foreground one; the use of transparency should be minimized because it may increase pilot interpretation time or errors.
5.8.9 Requiring the flightcrew to discriminate between shades of the same color for distinct meaning is not recommended. The use of pure blue should not be used for important information because it has low luminance on many display technologies (for example, CRT and LCD).
5.8.10 Any foreseeable change in symbol size should ensure correct color interpretation. For example, the symbol needs to be sufficiently large so the pilot can interpret the correct color.
5.9 Dynamic (Graphic) Information Elements on a Display.
The following paragraphs cover the motion of graphic information elements on a display, such as the indices on a tape display. Graphic objects that translate or rotate should do so smoothly without distracting or objectionable jitter, jerkiness, or ratcheting effects. Data update rates for information elements used in direct airplane or powerplant manual control tasks (such as attitude, engine parameters, etc.) equal to or greater than 15 Hertz have been found to be acceptable. Any lag introduced by the display system should be consistent with the airplane control task associated with that parameter. In particular, display system lag (including the sensor) for attitude that does not exceed a first order equivalent time constant of 100 milliseconds for airplanes with conventional control system response is generally acceptable.
5.9.1 Movement of display information elements should not blur, shimmer, or produce unintended dynamic effects such that the image becomes distracting or difficult to interpret. Filtering or coasting of data intended to smooth the motion of display elements should not introduce significant positioning errors or create system lag that makes it difficult to perform the intended task.
5.9.2 When a symbol reaches the limit of its allowed range of motion, the symbol should either slide from view, change visual characteristics, or be self-evident that further deflection is impossible.
5.9.3 Dynamic information should not appreciably change shape or color as it moves. Objects that change sizes (for example, as the map range changes) should not cause confusion as to their meaning and should remain consistent throughout their size range. At all sizes the objects should meet the guidance of this chapter as applicable (that is, the objects should be discernible, legible, identifiable, placed accurately, not distracting, etc.).
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5.10 Sharing Information on a Display.
There are three primary methods of sharing information on a given display. First, the information may be overlayed or combined, such as when traffic alert and collision avoidance system (TCAS) information is overlayed on a map display. Second, the information can be time shared so that the pilot toggles between functions, one at a time. Third, the information may be displayed in separate physical areas or windows that are concurrently displayed. Regardless of the method of information sharing, care should be taken to ensure that information that is out prioritized, but is needed, can be recovered, and that it will not be needed more quickly than it can be recovered.
5.10.1 Overlays and Combined Information Elements.
5.10.1.1 When information is graphically overlaid over other information (for example, an airplane symbol over a waypoint symbol) in the same location on a display, the loss of information availability, information access times, and potential for confusion should be minimized.
5.10.1.2 When information obscures other information it should be shown that the obscured information is either not needed when it is obscured or can be rapidly recovered. Needed information should not be obscured. This may be accomplished by protecting certain areas of the display.
5.10.1.3 If information is integrated with other information on a display, the projection, placement accuracy, directional orientation, and display data ranges should all be consistent (for example, when traffic or weather is integrated with navigation information). When information elements temporarily obscure other information (for example, pop-up menus or windows), the resultant loss of information should not cause a hazard in accordance with the obscured information’s intended function.
5.10.1.4 Time Sharing.
5.10.1.4.1 For guidance on full-time vs. part-time displays, see paragraph 6.3.3 of this AC.
5.10.1.4.2 Any information that should or must be continuously monitored by the flightcrew should be displayed at all times (for example, attitude).
5.10.1.4.3 Whether or not information may be time shared depends on how easily it can be retrieved in normal, non-normal, and emergency operations.
Information for a given performance monitoring task may be time shared if the method of switching back and forth does not jeopardize the performance monitoring task.
5.10.1.4.4 Generally, system information, planning, and other information not necessary for the pilot tasks can be time shared.
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5.10.2 Separating Information Visually.
When different information elements are adjacent to each other on a display, the elements should be separated visually so the pilots can easily distinguish between them.
Visual separation can be achieved with, for example, spacing, delimiters, or shading in accordance with the overall flight deck information management philosophy. Required information presented in reversionary or compacted display modes following a display failure should still be uncluttered and still allow acceptable information access time.
5.10.3 Clutter and De-Clutter.
5.10.3.1 A cluttered display presents an excessive number or variety of symbols, colors, and/or other unnecessary information and, depending on the situation, may interfere with the flight task or operation. A cluttered display causes increased flightcrew processing time for display interpretation, and may detract from the interpretation of information necessary to navigate and fly the airplane. Information should be displayed so that clutter is minimized.
5.10.3.2 To enhance pilot performance, a means should be considered to de-clutter the display. For example, an attitude indicator may automatically de clutter when the airplane is at an unusual attitude to aid the pilot in recovery from the unusual attitude by removing unnecessary information and retaining information required for the flightcrew to recover the airplane.
5.11 Annunciations and Indications.
5.11.1 General.
Annunciations and indications include annunciator switches, messages, prompts, flags, and status or mode indications that either are on the flight deck display itself, or control a flight deck display. See § 25.1322 and AC 25.1302-1 for information regarding specific annunciations and indications such as warning, caution, and advisory level alerts.
5.11.1.1 Annunciations and indications should be operationally relevant and limited to minimize the adverse effects on flightcrew workload.
5.11.1.2 Annunciations and indications should be clear, unambiguous, timely, and consistent with the flight deck design philosophy. When an annunciation is provided for the status or mode of a system, it is recommended that the annunciation indicate the actual state of the system and not just the position or selection of a switch. Annunciations should only be indicated while the condition exists.
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5.11.2 Location.
Annunciations and indications should be consistently located in a specific area of the electronic display. Annunciations that may require immediate flightcrew awareness should be located in the flightcrew's forward/primary field of view.
5.11.3 Managing Messages and Prompts.
The following general guidance applies to all messages and prompts:
5.11.3.1 When messages are currently being displayed and there are additional messages in the queue that are not currently displayed, there should be an indication that the additional messages exist.
5.11.3.2 Within levels of urgency, messages should be displayed in logical order.
In many cases, the order of occurrence of events has been found to be the most logical way to place the messages in order.
5.11.3.3 See § 25.1322 and AC 25.1302-1 for information on warning, caution, and advisory alerts.
5.11.3.4 A text change by itself should not be used as an attention-getting cue (for example, to annunciate mode changes).
5.11.4 Blinking.
Blinking information elements such as readouts or pointers are effective methods of annunciation. However, the use of blinking should be limited because it can be distracting and excessive use reduces the attention getting effectiveness. Blinking rates between 0.8 and 4.0 Hertz should be used, depending on the display technology and the compromise between urgency and distraction. If blinking of an information element can occur for more than approximately 10 seconds, a means to cancel the blinking should be provided.
5.11.5 Use of Imaging.
This paragraph provides guidance on the use of images that depict a specific portion of the airplane environment. These images may be static or continuously updated. Imaging includes weather radar returns, terrain depictions, forecast weather maps, video, enhanced vision displays, and synthetic vision displays. Images may be generated from databases or by sensors.
5.11.5.1 Images should be of sufficient size and include sufficient detail to meet the intended function. The pilots should be able to readily distinguish the features depicted. Images should be oriented in such a way that their presentation is easily interpreted. All images, but especially dynamic images, should be located or controllable so they do not distract the pilots from required tasks. The source and intended function of the image and the level of operational approval for using the image should be provided to the pilots. This can be accomplished using the airplane flight manual 5-14
(AFM), image location, adequate labeling, distinct texturing, or other means.
5.11.5.2 Image distortion should not compromise image interpretation. Images meant to provide information about depth (for example, three-dimensional type perspective displays) should provide adequate depth information to meet the intended function.
5.11.5.3 Dynamic images should meet the guidance in paragraph 5.9 of this chapter. The overall system lag time of a dynamic image relative to real time should not cause flightcrew misinterpretation or lead to a potentially hazardous condition. Image failure, freezing, coasting, or color changes should not be misleading and should be considered during the safety analysis.
5.11.5.4 When overlaying coded information elements over images, the information elements should be readily identifiable and distinguishable for all foreseeable conditions of the underlying image and range of motion.
The information elements should not obscure necessary information contained in the image. The information should be depicted with the appropriate size, shape, and placement accuracy to avoid being misleading. They should retain and maintain their shape, size, and color for all foreseeable conditions of the underlying image and range of motion.
5.11.5.5 When fusing or overlaying multiple images, the resultant combined image should meet its intended function despite any differences in image quality, projection, data update rates, sensitivity to sunlight, data latency, or sensor alignment algorithms. When conforming an image to the outside world, such as on a HUD, the image should not obscure or significantly hinder the flightcrew’s ability to detect real world objects. An independent brightness control of the image may help satisfy this guideline. Image elements that correlate or highlight real world objects should be sufficiently coincident to avoid interpretation error or significantly increase interpretation time.
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CHAPTER 6. ORGANIZING ELECTRONIC DISPLAY INFORMATION ELEMENTS
6.1 Organizing Information Elements.
This chapter provides guidance for integrating information into the flight deck related to managing the location of information, arranging the display, windowing, configuring and reconfiguring the display, and selecting the sensors across the flight deck displays.
The following paragraphs include guidance for various flight deck configurations from dedicated electronic displays for the attitude director indicator and the horizontal situation indicator to larger display sizes that use windowing techniques to display various functionalities on one display area. In some flight decks the primary flight information and the navigation display are examples of information that is displayed using windowing techniques. Chapter 5 of this AC provides guidance for information elements including text, labels, symbols, graphics, and other depictions (such as video) in isolation and combination.
6.2 Types and Arrangement of Display Information.
This paragraph provides guidance for the arrangement and location of categories of information. The categories of information include the following:
• Primary flight information including attitude, airspeed, altitude, and heading.
• Powerplant information that covers functions relating to propulsion.
• Other information.
6.2.1 Placement—General Information.
The position of a message or symbol within a display conveys meaning to the pilot.
Without the consistent or repeatable location of a symbol in a specific area of the electronic display, interpretation error and response times may increase. The following information should be placed in a consistent location under normal conditions:
6.2.1.1 Primary flight information. (See paragraph 6.2.3 in this chapter and appendix A of this AC.)
6.2.1.2 Powerplant information. (See paragraph 6.2.4 in this chapter and appendix B of this AC.)
6.2.1.3 Flightcrew alerts. Each flightcrew alert should be displayed in a specific location or in a central flightcrew alert area.
6.2.1.4 Autopilot and flight director modes of operation.
6.2.1.5 Lateral and vertical path deviation indicators.
6.2.1.6 Radio altitude indications.
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6.2.1.7 Failure flags should be presented in the location of the information they reference or replace.
6.2.1.8 Data labels for navigation, traffic, airplane system, and other information should be placed in a consistent position relative to the information they are labeling.
6.2.1.9 Supporting data for other information, such as bugs and limit markings, should be consistently positioned relative to the information they support.
6.2.1.10 Features on electronic moving map displays (for example, very high frequency omnirange stations (VORs), waypoints, etc.) relative to the current airplane position. In addition, the features should be placed on a constant scale for each range selected.
6.2.1.11 Segment of flight information relative to similar information or other segments.
6.2.2 Placement—Controls and Indications.
When a control or indication occurs in multiple places (for example a “Return” control on multiple pages of a flight management function), the control or indication should be located consistently for all occurrences.
6.2.3 Arrangement—Basic T Information.
6.2.3.1 Section 25.1321(b) includes requirements for the “Basic T” arrangement of certain information required by § 25.1303(b).
6.2.3.2 The following paragraphs provide guidance for the Basic T arrangement.
This guidance applies to single and multiple display surfaces.
6.2.3.2.1 The Basic T information should be displayed continuously, directly in front of each flightcrew member under normal (that is, no display system failure) conditions. Section 25.1321(b) requires that flight instruments required by § 25.1303 must be grouped on the instrument panel and centered as nearly as practicable about the vertical plane of the pilot’s forward vision.
6.2.3.2.2 The Basic T arrangement applies to the primary display of attitude, airspeed, altitude, and direction of flight. Depending on the flight deck design, there may be more than one indication of the Basic T information elements in front of a pilot. For example, heading information may appear on backup displays, HUDs, and moving map displays. The primary airspeed, altitude, and direction indications are the respective display indications closest to the primary attitude indication.
6.2.3.2.3 The primary attitude indication should be centered about the plane of the flightcrew’s forward vision. This should be measured from the DEP at the 6-2
flightcrew station (see related regulation). If located on the main instrument panel, the primary attitude indication must be in the top center position (§ 25.1321(b)). The attitude indication should be placed so that the display is unobstructed under all flight conditions. See SAE ARP4102/7 for additional information.
6.2.3.2.4 The primary airspeed, altitude, and direction of flight indications should be located adjacent to the primary attitude indication. Information elements placed within, overlaid, or between these indications, such as lateral and vertical deviation, are acceptable when they are relevant to respective airspeed, altitude, or directional indications used for accomplishing the basic flying task, and are shown to not disrupt the normal crosscheck or decrease manual flying performance.
6.2.3.2.5 The instrument that most effectively indicates airspeed must be adjacent to and directly to the left of the primary attitude indication (§ 25.1321(b)).
The center of the airspeed indication should be aligned with the center of the attitude indication. For airspeed indications, vertical deviations have been found acceptable up to 15° below and to 10° above when measured from the direct horizontal position of the airplane waterline reference symbol. For tape type airspeed indications, the center of the indication is defined as the center of the current airspeed status reference.
6.2.3.2.6 Parameters related to the primary airspeed indication, such as reference speeds or Mach indication, should be displayed to the left of the primary attitude indication.
6.2.3.2.7 The instrument that most effectively indicates altitude must be located adjacent and directly to the right of the primary attitude indication (§ 25.1321(b)). The center of the altitude indication should be aligned with the center of the attitude indication. For altitude indications, vertical deviations have been found acceptable up to 15° below to 10° above when measured from the direct horizontal position of the airplane waterline reference symbol. For tape type altitude indications, the center of the indication is defined as the center of the current altitude status reference.
6.2.3.2.8 Parameters related to the primary altitude indication, such as the barometric setting or the primary vertical speed indication, should be displayed to the right of the primary altitude indication.
6.2.3.2.9 The instrument that most effectively indicates direction of flight must be located adjacent to and directly below the primary attitude indication (§ 25.1321(b)). The center of the direction of flight indication should be aligned with the center of the attitude indication. The center of the direction of flight indication is defined as the center of the current direction of flight status reference.
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