AC 23.1311-1B UP Мажіти Optimum 40° Horiz „Horiz 15°
• NOM 20°
• NOM DN Vertical Field Optimum Maximum C/L C/L 35°
• RT Horizontal Field RT Figure 1. Primary Field-of-View
15.4 Recommended Location for Displaying Information Table 1 contains the recommended location for displaying information intended for new panel layout with integrated electronic displays; however, these guidelines should be followed for other installations as practicable. Deviations beyond these limits may be approved for individual flight instruments depending on the combination of factors listed in section 15.1. These deviations need a display installation evaluation. It may not be practicable for retrofit installations with new electronic displays, such as with ATC, STC, and field approvals, to comply with the values in the table. This is due to limitations in the systems and incompatible technologies between the aircraft and the system being added. In such cases, for any given item, the angular deviations should not increase from what was originally found to be acceptable, and the display characteristics should be at least as good as the original display. For retrofit installations, it may be acceptable for installations to fall outside the recommended data in Table 1. These deviations may need an evaluation by the certification authority. Factors to consider during this evaluation include the distinguish ability, attention-getting quality, readability, etc. The field-of-view angles should be applied for installation approvals where a design eye reference point exists. For installation approvals where no design eye reference point is defined, the linear panel distances from center in Table 1 should be used.
Table 1 - Field-of-View Data Recommended Field-of-View Pilot View FOV, Deg from (inches) From Approx. Distance Reference Center Centerline Line (NOTE 1) (NOTE 1) PFI - Basic T - Electronic or 4 (NOTE 2) 2 (NOTE 2) Mechanical Navigation Course Error Data (HSI, 15
CDI, FD) Autopilot and /Flight Director Modes 15 8 Navigation Source Annunciation 15 (NOTE 3) 8 (NOTE 3) System Warnings and Cautions- 15 (NOTE 4) 8 (NOTE 4) Including failure annunciation Required Powerplant 21 Advisories Annunciations 35 21 Standby Instruments 35 (NOTE 5) 21 (NOTE 5) Reversionary Display for PFI 35 21 Electronic Map Display that is not used 35 (NOTE 6) 21 (NOTE 6) to replace the CDIHSI/FD NOTE 1. The FOV angles and Approximate Distance from Center Reference Line, based on a viewing distance of 30 inches from the panel, are defined as acceptable angles and distance to each data source from the center of basic T, or pilot view centerline. Distances are measured center-to-center of the display in question, measured horizontally. Vertical placement in the panel can be from just below the basic T to the glare shield.
NOTE 2. Display PFI as close to the center of reference as possible.
NOTE 3. The navigation source annunciation should be on or near the affected display and should appear on the same side of the basic T as the affected display. The guidelines for the proximity to the affected display depend on the size, color, and distinguishing characteristics of the source annunciation.
NOTE 4. Warnings and cautions can be presented within 35 degrees if they are associated with a unique aural tone or a master warning/caution light that is within 15 degrees. The warnings and cautions should be in a consistent location, such as on an annunciator panel. If an aural tone is used, it should be readily distinguishable from all other cockpit sounds and provide unambiguous information to direct the pilot's attention to a visual indication of the condition. Consider the number of aural alerts.
NOTE 5. Install the standby instruments as close as practicable to the PFI.
NOTE 6. If a map display is used for primary navigation, such as for the CDI, HSI, or flight director, then it should meet the 15-degree FOV requirement identified for the steering command.
16.0 LUMINANCE
16.1 Visual Performance All displayed information such as symbols, graphics, and alphanumeric characters should be clearly differentiated from one another and legible under all ambient illumination conditions. SAE documents Aerospace Standard (AS) 8034, and ARPs 1668B, 4067, and 4256 may be used as guidelines for evaluating the visual performance parameters of the electronic displays relative to viewing, photo colorimetric, luminance characteristics, etc. These conditions range from the night environment to direct sunlight through any window with the operational brightness at the luminance expected at the display's useful end-of-life state. The end-of-life luminance level represents the expected value of the display brightness or minimum acceptable output that is established by the manufacturer. The display luminance should sufficiently provide a comfortable level of viewing with rapid adaptation when transitioning from looking outside the cockpit.
16.2 Luminance Level The luminance level of some displays will gradually diminish over the life of the unit. As part of the continued airworthiness requirements of § 23.1529, consider establishing an operational in-flight evaluation or maintenance evaluation to determine the minimum luminance level appropriate for the type of display, flight deck location, method of format, symbology, color used, etc. Although automatic luminance control compensation is not required, incorporating such a system may decrease pilot workload. Regardless of whether an automatic luminance control is incorporated, provide a manual luminance control that is not adversely affected by failure of any automatic luminance control. Luminance control should not result in some information disappearing while other information remains visible.
17.0 SYMBOLOGY AND FORMAT
17.1 Symbol Attributes To minimize confusion or misinterpretation, symbols should be casy to discern, consistent within the cockpit, and learned with minimal training. Symbols should not have shapes, colors, or other attributes that are ambiguous or could be confused with the meaning of similar symbols. Electronic displays in the cockpit should use symbology consistent with their intended function. Clearly define and appropriately classify the function of symbology for the pilot. Symbols representing the same functions on more than one display should be the same. Different symbols among different displays for the same functions may be acceptable only if it can be clearly shown that the pilot can quickly and consistently recognize, interpret, and respond correctly without incurring excessive pilot workload. For example, to indicate bank angle on the attitude displays in the cockpit, the type of 33
pointer, ground (fix) or sky (moveable), should be similar for ease of interpretation and to minimize confusion.
17.2 Symbol Standards Symbols should be based on established industry standards (for example, SAE ARP 4102/7 and ARP 5289 for electronic displays). For example, the use of flashing letters, such as an "X," should be consistent. Flashing, when used, should not be a caution for one parameter, and a warning for another. One benefit of symbol standards versus other information formats is the compact encoding of information, which minimizes clutter. However, the symbolic encoding of information should remain simple enough for pilots to learn and recall.
17.3 Clutter Powerful formats are possible with an electronic display system, but excessive information on a limited display size can result in clutter and reduce the efficiency of the pilot cues. The density of information on the display should be compatible with the pilot's ability to recognize essential information and to minimize misinterpretation. Symbols and markings that are displayed during specific phases of flight may be removed at other times to reduce clutter. Establish an information prioritization scheme to ensure the clear presentation of essential information. Clutter should be a major consideration during the reversionary or compacted modes. When combining essential information on a display after another display or unit fails, the display format should not be confusing and the information should still be usable, including unusual attitude. If clutter is anticipated, provide a means to manually remove the clutter (decluttering). Automatic decluttering, such as during specific phases of flight, or during certain alerts, may also be appropriate.
17.4 Unusual Attitude and Automatic De-clutter of the PFD
a. All primary attitude displays should provide an immediately discernable attitude recognition capability that fosters a safe and effective unusual attitude recovery capability. The display should provide sufficient cues to enable the pilot to maintain full-time attitude awareness and to minimize potential for spatial disorientation. The display should support the initiation of recovery from unusual attitudes within 1 second with a minimum correct response rate of 95 percent. Additional information included on primary flight reference display(s) should not interfere with maintaining attitude awareness, recovering from an unusual attitude, or the interpretation of any primary flight information.
b. The PFD may require an automatic de-clutter function during unusual attitudes. Unusual attitudes generally exceed 70 degrees of bank or +/-30 degrees of pitch, but may vary with airplane performance. (NOTE: Not applicable to aerobatic category airplanes). The approved configuration (whether basic-T configuration or a new configuration) should be preserved. Basic navigation information on the primary navigation display does not need to be decluttered.
17.5 Direct-Reading Alphanumeric-Only Display of Airspeed and Altitude Direct-Reading presentation of airspeed and altitude should convey to the pilot a quick-glance sense of rate and trend information. For airspeed and altitude, direct-reading alphanumeric displays may not be adequate on the primary display or on the standby instruments, but it is acceptable on a display used as supplementary information. If the applicant proposes a direct-reading alphanumeric display, they should show that the pilot response is equal to or better than the response with analog data (symbology) using a human factors evaluation.
17.6 Round Dial and Moving Scale Display The display of a round dial, moving pointer with a digital readout is acceptable. To accommodate a larger operating range on a linear tape, adopt a moving scale display with the present value on a digital readout. Since the moving scale display typically does not provide any inherent visual cue of the relationship of present value to low or high airspeed limits, quick-glance awareness cues may be needed.
17.7 Low-Speed And High-Speed Awareness Cues
a. Airspeed displays with fixed pointers and moving scales should provide appropriate lowspeed and high-speed awareness cues. Conventional mechanical airspeed indicators for part 23 airplanes include simple green and white speed arcs that, when combined with a moving pointer, provides pilots with adequate low-speed awareness. Airspeed displays incorporating fixed pointers and moving scales require more cues than conventional indicators to compensate for their deficiencies. For part 23 airplanes, prominent green and white arcs provide the pilot with speed cues but not enough to be considered equivalent. Therefore, low-speed awareness cues are necessary for part 23 airplanes.
b. The low-speed awareness cues should include a red arc starting at Vso and extending
• down toward zero airspeed. During takeoff, the red arc indication of low speed should not be displayed. The applicant may choose an optional yellow band from Vsi down to Vso. The applicant may choose a single conservative stall speed value to account for various weight and flap configurations (reference § 23.1545(a)(4)). For most part 23 airplanes, a fixed value at gross weight and full flaps is acceptable since this has been an adequate safety standard for mechanical gauges.
Incorporate a red arc or red barber pole extending from VNE or Vo upward to the end of the airspeed tape.
NOTE: The red arc below the stall speed is intended for low speed awareness only and is not intended to limit flight operation.
17.7.1 VNE Airplanes The applicant must show compliance with §§ 23.1311(a)(6) and 23.1545 (paragraphs (a) through
(d)), and incorporate the following speed awareness cues for VNE airplanes, as shown in Figure 2.
a. Incorporate red band from Vso to 0 (or minimum number).
b. Incorporate red band from VNE to the top of the airspeed tape.
c. Yellow band is optional in the low speed range from Vso to VsI. We discourage use of the yellow band (due to clutter) for twin-engine airplanes that incorporate a red and blue line, in accordance with § 23.1545, for one-engine-inoperative speeds.
Red
• VNE Yellow * VNO Green VEE Blank or optional yellow arc * Vso Red Figure 2. Low-Speed and High Speed Awareness for VNE Airplanes 36
17.7.2 VO Airplanes The applicant must show compliance with §§ 23.1311(a)(6) and 23.1545 (paragraphs (a) through
(d)), and incorporate the following speed awareness cues for Vo airplanes, as shown in Figure 3.
Incorporate red band from Vso to 0 (or minimum number).
Incorporate red band from Vo to the top of the airspeed tape.
• The green arc for normal operations is not required, but it may be used if previously approved.
The yellow band is optional in the low speed range from Vso to Vs1.
Red VMO Note: On commuter category Airplanes, bugs should be This is a blank provided for Setting V1 and area Black V2- represented by a black arc.
VFE Vs1 Blank or optional yellow arc Vso Red Figure 3. Low-Speed and High Speed Awareness for Vo Airplanes 37
17.7.3 Primary Flight Display
a. Low-speed awareness is an important PFD display function. Stalls remain in the top five causes of fatal accidents for all types of part 23 airplanes, so it makes sense to use the expanded display capability of new part 23 electronic PFDs to address low-speed awareness more effectively.
b. Historically, with traditional round dial instruments there was no ability to put color arcs on the airspeed indicator. Newer part 23 airplanes are required to also have a stall warning that sounds at 5-10 percent above stall. This was the best that could be afforded with existing technology. Unfortunately, most stalls occur in Vc and the pilot probably is not looking at the airspeed indicator when the airplane is slowing to a stall.
c. With electronic displays, designers are not constrained to simply reproducing the old round-dial type displays. The displays can have features that were not possible on conventional instruments. Applicants should consider using the display capabilities to catch the pilot's attention away from looking out the window or fixating on flight or navigation displays such as the flight director or HSI. One example the applicants might consider is flashing a large red "STALL" in the center of the PFD and MFD. These should be large enough to catch the pilot's attention using peripheral vision. Another example is to display an angle-of-attack (AOA), or AOA-like display, above the airplane symbol (or equivalent) essentially showing the stall margin. Pilots prefer an AOA scheme so they can see their stall margin diminishing and take corrective action based on a trend.
17.8 Linear Tape Altimeter Displays
a. Linear tape altimeter displays should include enhancements denoting standard 500- and 1,000-foot increments. These displays should convey unambiguously, at a glance, the present altitude. Combining altimeter scale length and markings, therefore, should be enough to allow sufficient resolution for precise manual altitude tracking in level flight. They should also have enough scale length and markings to reinforce the pilot's sense of altitude. The scale length should also allow sufficient look-ahead room to adequately predict and accomplish level off. Pilot evaluations have shown that, in addition to the appropriate altitude markings commensurate with aircraft performance, an altitude reference bug is recommended to provide acceptable cues.
b. Display a trend indicator unless a Vsi is located adjacent and to the right of the altimeter.
A six-second altitude-trend indicator is typical, but other trend values may be more appropriate depending on the airplane performance and altitude tape scaling.
17.9 Standardization Guide for Integrated Cockpits in Part 23 Airplanes This AC is to acknowledge the General Aviation Manufacturers Association (GAMA) Publication No. 12, "Recommended Practices and Guidelines for an Integrated Flightdeck/Cockpit in a 14 CFR Part 23 (or equivalent) Certificated Airplane," as an acceptable means for showing compliance with applicable requirements for electronic displays in part 23 airplanes. AC 23-23, or GAMA 38
Publication No. 12, and this AC should not conflict with each other. GAMA Publication No. 12 provides more specifics in certain areas for standardization for pilot transitions from various cockpits. These specifics are acceptable, but they do not cover all the issues for the installation of electronic displays. One significant benefit of AC 23-23 to standardization between cockpit designs is that it should improve pilot performance (that is, reduce pilot errors, tasks performance times, etc.) when transitioning between different aircraft systems.
17.10 Alternative Formats Alternative formats or arrangements to those described above should have an adequate human factors evaluation completed to show that pilot response is timely and accurate to at least the level of the existing conventional displays. Human factors criteria should be defined as part of the design process. Because displays are a function of the specific cockpit layout and configuration, human factors evidence needs to be provided during certification. Specific human factors evaluations and .
studies that have been performed may support the configuration of displays and their location in the cockpit. Validating these evaluations/studies on each airplane during the installation process of the certification is an alternative.
17.11 Integration of Display Parameters Integration of several display parameters into one common display provides distinct benefits, but it raises some certification issues. New approaches presenting data and commands to the pilot are encouraged. To overcome the issues that may occur as a result of this integration, present the data and commands in a simple format to alleviate any increase in pilot workload. The overall goal is to meet or exceed the existing cockpit performance levels currently in operational use while maintaining pilot workload at acceptable levels.
17.12 Overlays
a. If overlays are provided, the display format should allow the pilot to overlay weather or other graphics relevant to the flight path on one display without ambiguity. Each new graphic should be evaluated both individually and with allowed combinations of other weather, terrain, and navigation symbology to guard against confusing the pilot or cluttering the screen. When overlaying two or more functions, using the same or similar color to convey different information is not recommended. If the same or similar colors are required, then retain the meaning of the different information. Patterning, bordering, or blanking may be used to clearly depict the different sets of data.
b. If overlays are presented, the data should be presented in an airplane heading orientation. The orientation of any secondary navigation display is optional (for example, Track-up, North-up, Heads-Up). All overlay data shall be the same map orientation and scale as the display it is placed on. For more information, see RTCA/DO-257A. The orientation on any navigation display should not change when an overlay is added, unless required by TSO guidance. A thumbnail display is not considered an overlay.
c. The ability to perform overlays is one of the greatest strengths of an electronic display, but it also creates the potential to produce cluttered or misleading information. Therefore, the number of overlays shall not cause the information displayed to become unusable through cluttering or obscuration. Combinations of multiple data presentations shall not cause conflicting interpretation of the symbology or icons.
17.13 Scaling Symbol attributes that use scaling and dynamics should be appropriate for the performance level of the airplane. Conflicting range scaling shall not occur. Provide map range. Always display the range scale for the primary navigation display in the same location on that manufacturer's product.
18.0 ANNUNCIATION
18.1 General The electronic display system should provide the pilot with visibly discernible annunciators that will indicate the system operating modes. The visual annunciators should be distinctive under all normal lighting conditions and consistent with cockpit warnings. Under night lighting with the display average brightness at the lowest usable level for prolonged flight, visual annunciators should be usable. Consistently locate annunciations in a specific area of the electronic display to ensure proper interpretation by the pilot. Except for a flight director display, using the display selection control position as annunciation is acceptable only under certain conditions. Those conditions include when the control position is in direct view of the pilot, without head movement, and when the control position is obvious under all lighting conditions. When a failure occurs or when using reversionary modes, an annunciation of abnormal system status shall be provided, in accordance with § 23.1311(a)(7). The display should not provide hazardously misleading information.
Evaluate annunciations that require flight crew action to determine if the required actions could be accomplished in a timely manner without exceptional pilot skill. A failure of any PFI sensor input to the PFD should be appropriately annunciated on the PFD.
18.2 Multiple System Configurations Where multiple system configurations and more than one sensor input are available for source selection, the switching configuration by annunciation or by selector switch position should be readily visible, readable, and should not be hazardously misleading to the pilot using the system.
Labels for mode and source selection annunciators should be compatible throughout the cockpit. To ensure the flight crew can properly interpret the system status, cautionary annunciation methods should be consistent when numerous interface-switching configurations are possible.
18.3 Alerting Messages Alerting messages should differentiate between normal and abnormal indications. Abnormal indications should be clear and unmistakable, using techniques such as different shapes, sizes, 40
colors, flashing, boxing, outlining, etc. Provide individual alerts for each function essential for safe operation.
18.4 Visual Crew Alerting and Display Prioritization Due to the ability to display information from several sources on an integrated display, a prioritization scheme ensures the continuous availability of essential information to the flight crew.
Prioritization of time critical alerts such as TAWS, Predictive Windshear System (PWS), Traffic Alert and Collision Avoidance (TCAS), and Reactive Windshear System (RWS) have been established for small airplane applications and are shown in AC 23-18. Crew alerting information systems require appropriate prioritization of warning, caution, or advisory information. This prioritization includes both visual and aural alerts. Layering the new information over an existing moving map display or an existing weather display, as a result of an automatic pop-up capability, is a common technique. Annunciation of any system level warning, caution, and advisory alert should be compatible with the time critical alert schematic. Prioritize systems information displayed on the MFD to allow ready access to critical information. Less critical information may be less accessible. Provide a means for the flight crew to select higher priority information as needed with a single entry on the MFD control panel or keypad.
18.5 Visual Alerts for Time Critical Warnings Visual alerts for time critical warnings that require immediate pilot action should be annunciated with an aural warning. Terrain, traffic, and weather are typically displayed in a layered format on the Navigational Display (ND), although weather and terrain cannot be displayed at the same time in many current designs. A time critical threat should trigger an automatic pop-up and the appropriate display on the ND, as well as the appropriate aural alert. Subsequent time critical alerts of a higher priority may override the visual display, but they should override the previous aural alert. Other MFD functions, such as checklists, synoptic and expanded systems information, should only be shown when selected by the crew or displayed by phase of flight.
18.6 Supplementary Monitoring of System Status through Independent Sensors Electronic displays may present system parameters, such as engine instruments, that can serve as supplementary information to the certified aircraft systems. This information may use sensors that are completely independent from the originally approved sensors. When supplementary information is presented using independent sensors, the presentation cannot interfere or conflict with the primary information. Clearly annunciate and/or display any exceedance to the pilot in the appropriate color, in accordance with §§ 23.1322 and 23.1549. The Airplane Flight Manual Supplement (AFMS) and/or the Pilot Operating Handbook must clearly identify the relationship and procedures associated with those annunciations.
19.0 LAG TIME AND DATA UPDATE
a. 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 41
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.
Update rates of data on displays should be fast enough so that required symbol motion is free from objectionable lag or stepping.
b. SAE ARPs provide recommended lag times for display of the format and primary flight data, and minimum rates for data updates, to meet symbol motion. A 50-60 Hz refresh rate is typically enough to remove traces of visible flicker on the display. Frequencies above 55 Hz for stroke symbology or non-interlaced raster and 30/60 Hz for interlace raster are generally satisfactory. Some map information may be judged as adequate for enroute navigation displays with update rates of at least 1 Hz, depending on the specific aircraft. Update other critical data, such as attitude, heading, or air data symbology, at a rate of at least 15 Hz, depending on the airplane.
20.0 CONTROLS Display controls should be clearly visible, labeled, and usable by the pilot, with the least practicable deviation from the normal position and from the line of vision when the pilot is looking forward along the flight path. Controls should have an appropriate amount of tactile feel (for example, detents, friction, stops, or damping, etc.) so they can be changed without undue concentration, which minimizes the potential for inadvertent changes. Design controls for the pilot to use intuitively. The controls should be identified easily and located in all lighting conditions, allow differentiation of one control from another, and have feedback through the system appropriate for the function being controlled.
21.0 TEST FUNCTIONS The electronic display should incorporate a pilot selectable or automatic test mode, such as built in testers, that exercises the system to a depth appropriate to the system design. Include this function even if the system failure analysis is not dependent on such a mode, or if display test is also a maintenance function. The test mode (or a sub mode) should display warning flags in their proper locations. Exercise alerting and annunciation functions that are necessary to alert the pilot of unsafe conditions. It is acceptable to incorporate the display test with a centralized cockpit light test switch to have the display test function disabled when airborne. The test mode may provide a convenient means to display the software configuration.
22.0 COLOR STANDARDIZATION
22.1 General Color is considered an enhancement for understanding the display information that leads to performance improvement. Select color to minimize display interpretation errors. A proliferation of color sets can ultimately reduce safety rather than increase it. Using contrast between basic colors provides a better differentiation of display elements than arbitrarily using colors near to cach other in the color table. Before defining the color standard for a specific display, establish a 42