Display Size

·        A display should be large enough to present information in a form that is usable (for example, readable or identifiable) to the flightcrew from the flightcrew station in all foreseeable conditions, relative to the operational and lighting environment and in accordance with its intended function(s). [AC 25-11A, 16.a(1)]

        See also: Chapter 8 Intended Function

Display Resolution

·        The resolution and minimum line width should be sufficient to support all the displayed images such that the displayed information is visible and understandable without misinterpretation from the flightcrew station in all foreseeable conditions, relative to the operational and lighting environment. [AC 25-11A, 16.a(2)]

Luminance and Lighting

·        The instrument lights must make each instrument and control easily readable and discernible. [14 CFR 23.1381(a)]

        See also: 14 CFR 25.1381 (a)(1), 27.1381(a), and 29.1381(a) which are worded slightly differently.

·        The display symbology shall be readable and/or discernible throughout the viewing envelope under all ambient illumination levels ranging from 1.1 lx (0.1 ft-c) to sun-shafting illumination of 86 100 lx (8000 ft-c) incidence on the face of the display and provide rapids eye adaptation for transitions from forward field of view luminance levels of up to 34 300 cd/m2 (10 000 fL)). [TSO-C113a/SAE AS8034B, 4.3.1]

·        The display luminance shall be sufficient to provide a usable display under the maximum ambient illumination. [TSO-C113a/SAE AS8034B, 4.3.2]

·        The display system shall have capability for manual luminance control. [TSO-C113a/SAE AS8034B, 4.3.2.1]

·        If the display system has automatic luminance compensation, the operation of this compensation shall function so that the system meets the requirements of 4.3.1 under changing flight deck ambient light levels. Manual luminance control shall not be adversely affected by failure of the automatic luminance control. [TSO-C113a/SAE AS8034B, 4.3.2.2]

·        When the luminance of the display is varied between maximum and minimum, the relative luminance of all displayed information shall remain visually consistent. In no case shall any critical symbols or characters become invisible at the minimum luminance setting while other characters or symbols are visible. [TSO-C113a/SAE AS8034B, 4.3.2.3]

·        The luminance uniformity of the display shall be sufficient to prevent hazardously distracting conditions or erroneous interpretation of information. [TSO-C113a/SAE AS8034B, 4.3.2.4]

·        Displayed information shall have sufficient luminance contrast and/or color difference to discriminate between the following as applicable: [TSO-C113a/SAE AS8034B, 4.3.3]

        a.     Between symbols (including characters and/or lines) and the background (ambient or generated) on which they are overlayed.

        b.     Between various symbols, characters and lines. This shall also include when they overlay ambient or generated backgrounds.

        c.     Between the generated backgrounds and ambient backgrounds.

        d.     Between the generated backgrounds of various specified colors.

·        In all cases the luminance contrast and/or color differences between all symbols, characters, lines, or all backgrounds shall be sufficient to preclude confusion or ambiguity as to information content of any displayed information. When operationally relevant, the color of the information shall be identifiable (e.g., if colors are used for alerting). The manufacturers shall specify the ambient illumination level and illuminate characteristic for which this requirement is met. [TSO-C113a/SAE AS8034B, 4.3.3]

        Note:  It is not recommended to place a symbol on a background of equal luminance regardless of color differences. Saturated colors are not recommended to be used for background; saturated colors should be saved for smaller items such as symbols, icons, targets, etc. [TSO-C113a/SAE AS8034B, 4.3.3]

·        All illuminated information must be easily identifiable, readable and controllable by the pilot under all ambient lighting environments (direct sunlight to total darkness). Cockpit lighting evaluations should ensure that: [PS-ACE100-2001-004, Appendix A]

        (a) Enough lighting is provided to make the performance of all related tasks easy to accomplish with a high level of speed and accuracy.

        (b) Allow the pilot to be able to recognize and see any hazardous condition or potential hazards quickly, and

        (c) Provide visual comfort.

·        Each lighted component should be individually evaluated for uniform lighting and balance. Each component should also be evaluated for uniformity and balance with all other illuminated instruments. This includes other displays, controls, alerting systems and secondary lighting, all of which should be compatible with each other. [PS-ACE100-2001-004, Appendix A]

·        All control markings should be evaluated to ensure they are visible and evenly illuminated during both night and day operations. It should also be noted that font size (variations, e.g., character stroke size, width and height) of the illuminated displays can affect readability and perceived brightness. Variations in font size may create perceived lighting imbalances. (Reference ARP4103 for recommendations.) Lighting of one control should not interfere with viewing and identification of adjacent controls. Alerting lights must also be evaluated for adequate attention getting value for both day and night operations. [PS-ACE100-2001-004, Appendix A]

See also: Chapter 3.2 Labels; Chapter 6 Controls

·        Electronic display indicators, including those with features that make isolation and independence between powerplant instrument systems impractical, must be easily legible under all lighting conditions encountered in the cockpit, including direct sunlight, considering the expected electronic display brightness level at the end of an electronic display indictor's useful life. Specific limitations on

        display system useful life must be contained in the Instructions for Continued Airworthiness required by § 23.1529. [14 CFR 23.1311(a)(2)]

See also: Chapter 3.1 Electronic Display Information Elements and Features: General

·        Electronic displays are required to have adequate contrast and brightness to be legible in all ambient lighting environments from bright sunlight to total darkness. The lighting controls must also have an adequate range of adjustment to accommodate these conditions. This requirement is intended to provide readable displays without increasing pilot workload (for example, trying to shield the display to read it). [PS-ACE100-2001-004, Appendix A]

·        Information should be readable over a wide range of ambient illumination under all foreseeable conditions relative to the operating environment, including but not limited to: [AC 25-11A, 16.a(3)]

        •      Direct sunlight on the display,

        •      Sunlight through a front window illuminating white shirts (reflections),

        •      Sun above the forward horizon and above a cloud deck in a flightcrew member’s eyes, and

        •      Night and/or dark environment.

·        For low ambient conditions, the display should be dimmable to levels allowing for the flightcrew’s adaptation to the dark, such that outside vision and an acceptable presentation are maintained. [AC 25-11A, 16.a(3)(a)]

·        Automatic luminance adjustment systems can be employed to decrease pilot workload and increase display life. Operation of these systems should be satisfactory over a wide range of ambient light conditions, including the extreme cases of a forward low sun and a quartering rearward sun shining directly on the display. [AC 25-11A, 16.a(3)(b)]

·        Some manual adjustment should be retained to provide for normal and non-normal operating differences so that the luminance variation is not distracting and does not interfere with the flightcrew’s ability to perform their tasks. [AC 25-11A, 16.a(3)(b).1]

·        Displays or layers of displays with uniformly filled areas conveying information such as weather radar imagery should be independently adjustable in luminance from overlaid symbology. The range of luminance control should allow detection of color differences between adjacent small filled areas no larger than 5 milliradians in principal dimension; while at this setting, overlying map symbology, if present, should be discernible. [AC 25-11A, 16.a(3)(b).2]

See also: Chapter 3.8 Integrated Display Issues

·        Display luminance variation within the entire flight deck should be minimized so that displayed symbols, lines, or characters of equal luminance remain uniform under any luminance setting and under all foreseeable operating conditions. [AC 25-11A, 16.a(3)(c)]

·        The operating range of display luminance and contrast shall be sufficient to ensure display readability through the full range of normally expected flight deck illumination conditions (Reference SAE ARP4256*). [TSO-C165/RTCA DO-257A, 2.2.3]

        Note:  The full range of normally expected flight deck illumination span from complete darkness to direct and unfiltered sunlight. [TSO-C165/RTCA DO-257A, 2.2.3]

·        Display luminance shall not interfere with the usability of other flight deck displays nor produce unacceptable glare against the windscreen or other reflective surface. [TSO-C165/RTCA DO-257A, 3.1.3]

Glare and Reflections

·        Each pilot compartment must be free of glare and reflection that could interfere with the normal duties of the minimum flight crew. This must be shown in day and night flight tests under nonprecipitation conditions. [14 CFR 25.773(a)(2)]

        See also: 14 CFR 23.773(a)(2), 27.773(a)(1), 29.773(a)(2) which are worded slightly differently.

·        Evaluations should be conducted under all potential lighting conditions to include dawn or dusk conditions with the sun near the horizon, higher sun angles (both in front, behind, and directly overhead the airplane), and during night conditions (both dark night and moonlit conditions). Also evaluate the affect various internal lighting selections and levels have on readability and usability of airplane equipment and systems and the ability to see outside the cockpit. [PS-ACE100-2001-004, Appendix A]

See also: PS-ANM100-01-03A, Appendix A which is worded slightly differently.

·        This must be shown in day and night flight tests under non-precipitation conditions (§ 25.773(a)(2)). The criteria and the basic workload functions and factors for a minimum flightcrew are described in Appendix D to part 25, § 25.1523. [AC 25-11A, 16.a(11)]

        See Chapter 10 Workload

·        Reflectance of the display should be minimal to ensure display readability. [TSO-C165/RTCA DO-257A, 2.2.3]

·        Inspection of the cockpit for glare and reflections should always be considered as part of the evaluation procedure. Evaluations should ensure that glare and reflections do not cause visual discomfort or impair out the window viewing or interfere with other visual tasks. Lighting tests may be conducted in a mockup if available. Aircraft ground and flight tests should also be conducted for both day and night operations. [PS-ACE100-2001-004, Appendix A]

·        Evaluations should be conducted under all potential lighting conditions to include dawn or dusk with the sun near the horizon, higher sun angles both in front, behind and directly overhead the airplane, and at night (both dark night and moonlit). One should also evaluate the affect various internal lighting selections and levels have on readability and usability of electronic displays. [PS-ACE100-2001-004, Appendix A]

Dimming

·        Manual dimming should not be provided unless the minimum setting retains adequate attention-getting qualities when flying under all ambient light conditions. [AC 25.1322-1, Appendix 1, 1.d(2)]

See also: Chapter 4.3.1 Warnings, Cautions, and Advisories

·        Dimming controls should be examined for uniform operation from full bright to off. The dimming ranges should be sufficient to obtain adequate readability throughout the entire operational lighting environment. Consideration should be given to the number of dimming controls. The more dimming controls the pilot must operate the greater the workload and the increased likelihood of confusion and operator error; therefore, dimming controls should be kept to the minimum required. [PS-ACE100-2001-004, Appendix A]

Contrast

·        The display’s contrast ratio should be sufficient to ensure that the information is discernable under the whole ambient illumination range from the flightcrew station under all foreseeable conditions relative to the operating environment. [AC 25-11A, 16.a(4)(a)]

·        The contrast between all symbols, characters, lines, and their associated backgrounds should be sufficient to preclude confusion or ambiguity of any necessary information. [AC 25-11A, 16.a(4)(b)]

Chromaticity

·        The display chromaticity differences, in conjunction with luminance differences, should be sufficient to allow graphic symbols to be discriminated from each other, from their backgrounds (for example, external scene or image background) and background shaded areas, from the flightcrew station, in all foreseeable conditions relative to the lighting environment. Raster or video fields (for example, non-vector graphics such as weather radar) should allow the image to be discriminated from overlaid symbols, and should allow the desired graphic symbols to be displayed. [AC 25-11A, 16.a(5)(a)]

·        The display should provide chromaticity stability over the foreseeable conditions relative to the range of operating temperatures, viewing envelope, image dynamics, and dimming range, such that the symbology is understandable and is not misleading, distracting, or confusing. [AC 25-11A, 16.a(5)(b)]

Grayscale

·        The number of shades of gray and the difference between shades of gray that the display can provide should be adequate for all image content and its use, and should accommodate all viewing conditions. [AC 25-11A, 16.a(6)(a)]

·        The display should provide sufficient gray scale stability over the foreseeable range of operating temperatures, viewing envelope, and dimming range, such that the symbology is understandable and is not misleading, distracting, or confusing. [AC 25-11A, 16.a(6)(b)]

Display Response

·        Under standard ambient conditions, a display shall present statically correct and non-misleading information within 1 minute of receiving valid data. Full dynamic and other detailed performance requirements should be met within 10 minutes. Segmented displays shall have a test, which may be done during start-up or when the test is initialized, to verify that the segments are properly displayed. [TSO-C113a/SAE AS8034B, 4.6.1]

·        For power interruptions up to 200 ms in duration, recovery time should not exceed 1 second. In no case shall power transients cause any steady erroneous display or output (see also section 16 of DO-160G). [TSO-C113a/SAE AS8034B, 4.6.2]

·        The dynamic response of the display should be sufficient to provide discernibility and readability of the displayed information without presenting misleading, distracting, or confusing information. The response time should be sufficient to ensure dynamic stability of colors, line widths, gray scale, and relative positioning of symbols. Undesirable display artifacts and characteristics, such as smearing of moving images and loss of luminance, should be minimized so that information is still readable and identifiable under all foreseeable conditions, not distracting, and does not lead to misinterpretation of data. [AC 25-11A, 16.a(7)]

·        The display of information essential to the safety of flight should be thoroughly responsive and accurate to the operational requirements. Electronic display system delay effects of essential information, including attitude, airspeed, altitude, heading, and specific propulsion parameters, should not degrade the pilot's ability to control the airplane. Any lag introduced by the display system should be consistent with the airplane control task associated with that parameter. [AC 23.1311-1C, 19.0.a]

·        Display data shall be updated at sufficient frequency to meet symbol motion requirements. In particular for pitch and roll the update rate should be a minimum of 15 Hz. [TSO-C113a/SAE AS8034B, 4.6.3]

See also: Chapter 3.5 Graphical Depictions and Images

·        The display shall respond to operator control inputs within 500 msec. [TSO-C165/RTCA DO-257A, 2.2.4]

        Note: It is desirable to provide a temporary visual cue to indicate that the control operation has been accepted by the system (e.g., hour glass or message). It is recommended that the system respond within 250 msec. [TSO-C165/RTCA DO-257A, 2.2.4]

Refresh Rate

See also: Chapter 3.5 Graphical Depictions and Images for information on update rates.

·        The display refresh rate should be sufficient to prevent flicker effects that result in misleading information or difficulty in reading or interpreting information. The display refresh rate should be sufficient to preclude the appearance of unacceptable flicker. [AC 25-11A, 16.a(8)]

·        There should be no discernible display jitter when viewed within the viewing envelope. In no case shall the display jitter be objectionable. Display jitter shall be no greater than 0.6 milliradians peak-to-peak when viewed within the design eye position viewing envelope as specified by the instrument manufacturer. Jitter of 0.3 milliradians peak-to-peak from any point within the viewing envelope is a suggested upper limit, but that may not be acceptable in some instances. [TSO-C113a/SAE AS8034B, 4.2.6]

·        The display shall not exhibit an unacceptable level of flicker under the full range of ambient environment up to the maximum ambient illumination level specified by 4.3.1 when viewed from any viewing angle defined in 4.2 and 4.2.1, with both foveal and full peripheral vision. [TSO-C113a/SAE AS8034B, 4.2.7]

Display Defects

·        Display defects, such as element defects and stroke tails, resulting from hardware and graphical imaging causes should not impair readability of the displays or induce or cause erroneous interpretation. [AC 25-11A, 16.a(10)]

·        Visible defects on the display surface (such as failed-ON or failed-OFF elements, rows, or columns, etc.) should not be distracting and shall not cause an erroneous interpretation of the display. [TSO-C113a/SAE AS8034B, 4.2.11]

·        No failed-ON row/columns shall be allowed on the display. [TSO-C113a/SAE AS8034B, 4.2.11.1]

·        Depending on resolution, mode, color, and format, there may be failed-OFF row/column defects which are neither distracting nor cause erroneous interpretation. In no case shall a failed-OFF row/column cause any loss of expected information or erroneous interpretation. If a failed-OFF row/column is in an unused area (format dependent) or is orthogonal to other depicted lines, it may never be detected by the flightcrew. [TSO-C113a/SAE AS8034B, 4.2.11.2]

·        The number of acceptable defects is dependent on the format. Any segment failure on a segmented display shall constitute an unacceptable display (unless there are redundant segments). [TSO-C113a/SAE AS8034B, 4.2.11.3]

General

·        Optics shall be designed to prevent contamination of surfaces by dust or moisture under all operating and test conditions that causes an unsafe condition. [SAE AS8034B, 3.12]

See also: Chandra et al., 2003

Luminance and Lighting

·        The minimum recommended character brightness is 1 cd/m2 (0.3 fL). (McAnulty, 1995)

·        The display luminance should be uniform across the display. The luminance variability at the edge of the display should be less than or equal to 50% of the luminance in the center of the display. The variability in the central 80% of the display should be less than or equal to 20%. (McAnulty, 1995)

·        If the brightness is adjustable, the minimum contrast ratio should be 1.4:1 under low and moderate ambient light conditions. A contrast ratio of 30:1 may be needed in bright sunlight conditions. (McAnulty, 1995)

·        If the brightness cannot be adjusted, the minimum contrast ratio should be 3:1. (McAnulty, 1995)

Refresh Rate

·        The presence of flicker should be barely discernible day or night considering foveal and full peripheral vision and a format most susceptible to producing flicker. [SAE ARP1874, 5.1.11]

·        To prevent flicker, the minimum refresh rate should be 50 – 60 Hz for CRTs, and the minimum frame rate should be 30 Hz for LCDs. To avoid jitter, variations in the location of a display element should be less than or equal to 0.0002 in per inch of viewing distance or 0.0002 mm per millimeter of viewing distance. (McAnulty, 1995)

Update Rate

·        If information is integrated with other information on a display, the update rate should be consistent.

See also: Chapter 3.8 Integrated Display Issues

Display Response

·        The delay between the movement of a control and the response to that movement on the display shall be minimized (DOT/FAA/CT-96-1).[RTCA DO-256, 3.2.1.2.2]