Visibility

·        For each instrument, each instrument marking must be clearly visible to the appropriate crewmember. [14 CFR 25.1543(b)] 

        See also: 14 CFR 23.1543(b), 27.1543(b), and 29.1543(b) which are worded slightly differently.

·        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 2.1 Visual Display Characteristics

·        The pilots should have a clear, unobstructed, and undistorted view of the displayed information. [AC 25-11A, 31.a(1)]

See also: AC 20-138C, 11-8.b(2) which is worded slightly differently.

·        All possible display configurations available to the flightcrew should be designed and evaluated for arrangement, visibility, and interference. [AC 25-11A, 36.d(1)]

Lighting Conditions

·        For all display configurations, all foreseeable conditions relative to lighting should be considered. Foreseeable lighting considerations should include failure modes such as lighting and power system failure, the full range of flight deck lighting and display system lighting options, and the operational environment (for example, day and night operations). [AC 25-11A, 31.a(1)]

·        Consider the effect of flight deck lighting on the appearance of the label, and the use of colors throughout the flight deck (i.e., color philosophy). [AC 20-175, 2-7.c]

See also: Chapter 3.7 Color; Chapter 6 Controls; Chapter 7 Design Philosophy

·        The flight guidance system functions, controls, indications, and alerts must be designed to minimize flightcrew errors and confusion concerning the behavior and operation of the flight guidance system… The indications must be visible to each pilot under all expected lighting conditions. [14 CFR 25.1329(i)]

Readability 

·        Readability must be maintained in sunlight viewing conditions per § 25.773(a) and under other adverse conditions such as vibration and turbulence. Figures and letters should not extend below the visual angles defined in SAE ARP 4102-7 at the design eye position of the flight crewmember who normally uses the information. [AC 25.1302-1, 5-5.b(2)]

See also: AMC 25.1302, 5.4.2.c which is worded slightly differently.

·        All displays, controls, and annunciators must be easily readable under all normal cockpit conditions and expected ambient light conditions (total darkness to bright, reflected sunlight). [AC 20-138C, 11-8.c]

·        The displayed information should be easily and clearly discernable, and have enough visual contrast for the pilot to see and interpret it. Overall, the display should allow the pilot to identify and discriminate the information without eyestrain. [AC 25-11A, 31.a(1)]

·        Readability should be maintained in adverse conditions, such as vibration. [AC 25-11A, 31.a(2)]

·        Text and symbology shall be readily discernible and should be legible and readable within the specified viewing envelope(s). [TSO-C113a/SAE AS8034B, 4.2.1]

        Note: It is the responsibility of the equipment installer to determine that the required aircraft viewing envelope is within the specified display viewing envelope(s). [TSO-C113a/SAE AS8034B, 4.2.1]

·        Information elements (text, symbol, etc.) should be large enough for the pilot to see and interpret in all foreseeable conditions relative to the operating environment and from the flightcrew station. If two or more pilots need to view the information, the information elements should also be discernable and interpretable over these viewing distances. [AC 25-11A, 31.a(1)]

·        Applicants should show, per § 25.1302(b), that display formats include the type of information the flightcrew needs for the task, specifically with regard to the speed and precision of reading required. The information can be in the form of a text message, numerical value, or a graphical representation of state or rate information. State information identifies the specific value of a parameter at a particular time. Rate information indicates the rate of change of that parameter. [AC 25.1302-1, 5-5.b(1)(a)]

        See also: AMC 25.1302, 5.4.2.a which is worded slightly differently.

·        If the flightcrew’s only way to determine non-normal values is by monitoring display values presented on the display, the equipment should offer qualitative display formats. Qualitative display formats convey rate and trend information better than quantitative (e.g. digital) presentations. If a qualitative display is not practical, the applicant should show the flightcrew can perform the tasks for which the information is used. Quantitative presentation of information is better for tasks requiring precise values. Refer to § 25.1322 and AC 25.1322 when a non-normal value is associated with a flightcrew alert. [AC 25.1302-1, 5-5.b(1)(b)]

        See also: AMC 25.1302, 5.4.2.a which is worded slightly differently.

·        Digital readouts or present value indices incorporated into qualitative displays should not make the scale markings or graduations unusable as they pass the present value index. [AC 25.1302-1, 5-5.b(1)(c); AMC 25.1302, 5.4.2.a]

·        Scale markings should be clear throughout all values presented in the readout. [AC 25.1302-1, 5-5.b(1)(c)]

Distinctiveness

·        Information elements should be distinct and permit the pilots to immediately recognize the source of the information elements when there are multiple sources of the same kind of information. [AC 25-11A, 31.a(1)]

Consistency on the Flight Deck

·        The following information should be placed in a consistent location under normal conditions [AC 25-11A, 36.b(1)]:

        •      Primary flight information.

        •      Powerplant information.

        •      Flightcrew alerts – each flightcrew alert should be displayed in a specific location or a central flightcrew alert area.

        •      Autopilot and flight director modes of operation.

        •      Lateral and vertical path deviation indicators.

        •      Radio altitude indications.

        •      Failure flags should be presented in the location of the information they reference or replace.

        •      Data labels for navigation, traffic, airplane system, and other information should be placed in a consistent position relative to the information they are labeling.

        •      Supporting data for other information, such as bugs and limit markings, should be consistently positioned relative to the information they support.

        •      Features on electronic moving map displays (for example, VORs, waypoints, etc.) relative to the current airplane position. In addition, the features should be placed on a constant scale for each range selected.

        •      Segment of flight information relative to similar information or other segments.

·        Other information should not be located where the primary flight information or required powerplant information is normally presented. [AC 25-11A, 36.b(5)(d)]

·        Data entry methods, color-coding philosophies, and symbology should be as consistent as possible across the various applications. [AC 120-76B, 12.m,(1)]

·        The applicant should consider consistency within a given system and across the flightdeck. Inconsistencies may result in vulnerabilities, such as increased workload and errors, especially during stressful situations. For example, in some FMS’s, the format for entering latitude and longitude differs across the display pages. This may induce flightcrew errors, or at least increase flightcrew workload. Additionally, errors may result if latitude and longitude are displayed in a format that differs from formats on the most commonly used paper charts. Because of this, it is desirable to use formats consistent with other media whenever possible. Although trade-offs exist, as discussed in the next paragraph, the following are design attributes to consider for consistency within and across systems: [AC 25.1302-1, 5-8.b(1)]

        (a)   Symbology, data entry conventions, formatting, color philosophy, terminology, and labeling.

        (b)   Function and logic. For example, when two or more systems are active and performing the same function, they should operate consistently and use the same style interface.

        (c)   Information presented with other information of the same type used in the flightdeck. As an example, navigation symbols used on other flightdeck systems or on commonly used paper charts could be used on electronic map displays.

        (d)   The operational environment. For example, it is important that an FMS should be consistent with the operational environment, so the order of the steps required to enter a clearance into the system is consistent with the order in which they are given by air traffic management.

        See also: AMC 25.1302, 5.7.2 which is worded slightly differently.

·        Display information representing the same thing on more than one display on the same flight deck should be consistent. Acronyms and labels should be used consistently, and messages/annunciations should contain text in a consistent way. Inconsistencies 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. [AC 25-11A, 31.b]

        See also: AMC 25.1302, 5.4.2(b) which is worded slightly differently; Wright and Barlow, 1995; Chapter 3.2 Labels; Chapter 8 Intended Function

·        Designs can base many elements of electronic display formats on established standards and conventional meanings. [AC 25.1302-1, 5-5.b(4)(a); AMC 25.1302, 5.4.2.e]

·        One way the applicant can achieve consistency within a given system, as well as within the overall flightdeck, is to adhere to a comprehensive flightdeck design philosophy. Another way is to standardize aspects of the design by using accepted, published industry standards such as the labels and abbreviations recommended in ICAO 8400/5. The applicant might standardize symbols used to depict navigation aids, such as Very High Frequency Omnidirectional Range (VOR) beacons, by following the conventions recommended in SAE document ARP 5289*. [AC 25.1302-1, 5-8.b(2)]

        See also: AMC 25.1302, 5.7.2 which is worded slightly differently.

·        The applicant should provide an analysis identifying each piece of information or data presented in multiple locations and show the data are presented in a consistent manner or, where that is not true, justify why that is not appropriate. [AC 25.1302-1, 5-8.c(1)(a)]

·        Where information is inconsistent, the inconsistency should be obvious or annunciated, and should not contribute to errors in information interpretation. [AC 25.1302-1, 5-8.c(1)(b)]

·        The applicant should provide a rationale for instances where a system’s design diverges from the flightdeck design philosophy. Consider any impact on workload and errors as a result of this divergence. [AC 25.1302-1, 5-8.c(1)(c)]

·        The applicant should describe what conclusion the flightcrew is expected to draw and what action should be taken when information on the display conflicts with other information on the flightdeck either with or without a failure. [AC 25.1302-1, 5-8.c(1)(d)]

        See also: Chapter 7 Design Philosophy; Chapter 9 Error Management, Prevention, Detection, and Recovery

Arrangement and Organization

·        Powerplant information must be closely grouped (in accordance with § 25.1321) in an easily identifiable and logical arrangement which allows the flightcrew to clearly and quickly identify the displayed information and associate it with the corresponding engine. Place parameter indications in order of importance with the most important one at the top. Typically, the top indication is the primary thrust setting parameter. [AC 25-11A, 36.b(4)(b)]

See also: Chapter 5.1 Basic “T” Arrangement

·        Analysis is not sufficient as the sole means of compliance for new or novel display management schemes. The applicant should use simulation or flight test of typical operational scenarios to validate the flightcrew’s ability to manage available information. [AC 25.1302-1, 5-5.c(1)(b)]

See also: AMC 25.1302, 5.4.3.a which is worded slightly differently.

Demonstrating Compliance

·        Applicants should use this AC as a guide to show that information displayed in the proposed design complies with § 25.1302(b). Refer to AC 25-11A for information presentations on electronic displays. The proposed means should be of sufficient detail to show the function, method of control operation, and results comply with the requirements in § 25.1301 and that the results of the presented information are: [AC 25.1302-1, 5-5.a(1)]

        (a) clear,

        (b) unambiguous,

        (c) appropriate in resolution and precision,

        (d) accessible,

        (e) usable, and

        (f) able to provide adequate feedback for flightcrew awareness.

        See also: AMC 25.1302, 5.4.1 which is worded slightly differently.

·        Information presented on the integrated flightdeck, regardless of the medium used, must meet all of the requirements in § 25.1302 as stated above. For visual displays, this AC addresses mainly display format issues and not display hardware characteristics. [AC 25.1302-1, 5-5.a(2)]

·        Section 25.1302 requires information intended for the flightcrew must be provided in a clear and unambiguous format in a resolution and precision appropriate to the task and that the information conveys the intended meaning. [AC 25.1302-1, 5-5.b(4)(e)]

General

·        The system shall clearly indicate functions that are available for use from those that are not available based on the current context of the system status. [RTCA DO-256, 3.2.1.2.3]

Readability

·        The simplest design should be used to convey the necessary information. (McAnulty, 1995; MIL-STD-1472G; Ahlstrom and Longo, 2003)

·        Displays should not contain extraneous information, text, or graphics. (Garner and Assenmacher, 1997; McAnulty, 1995)

·        For text displays, the display density should be less than 50%; a display density of 25% or less is preferable. (Garner and Assenmacher, 1997; Ahlstrom and Longo, 2003)

·        Information should be presented using the least precise display format. (McAnulty, 1995)

Consistency on the Flight Deck

·        The display format should be consistent with user conventions, data entry requirements, and other similar displays. (McAnulty, 1995)

Arrangement and Organization

·        Sets of data that are associated with specific questions or related to particular functions shall be grouped together to signify those functional relationships. [MIL-STD-1472G, 5.2.2.2.6.a(3)]

·        All information needed for one task should be located on the same display. (Garner and Assenmacher, 1997)

·        The user should not need to remember information across pages. (Garner and Assenmacher, 1997)