Appendix F It should specifically address the simultaneous use of the HUD by both pilots during each phase of flight, as well as cross-flight-deck transfer of control.
F.6.2 Flightcrew Awareness of Other Instruments and Indications.
With single HUD installations, the PF likely uses the HUD as a primary flight reference and the PNF monitors the head-down instruments and alerting systems for failures of systems, modes, and functions that are not displayed on the primary flight displays or HUD. However, in the case where both flightcrew members simultaneously use HUDs, the flightcrew should be able to maintain an equivalent level of awareness of key information that is not displayed on the HUD (e.g., powerplant indications, alerting messages, and airplane configuration indications).
F.6.3 Roles and Responsibilities.
The applicant should define the operational concept to account for the expected roles and responsibilities of the PF and PNF. The concept should also take into account the following considerations:
F.6.3.1 Impact on Head-Down Vigilance. When both pilots of the flightcrew use a HUD as the primary flight display, the visual head-down indications may not receive the same level of vigilance (as compared to a pilot using the head-down primary flight display).
F.6.3.2 Assurance of Head-Down Scan. The applicant should explain how the scan of the head-down instruments is ensured during all phases of flight, and, if not, what compensating design features help the flightcrew maintain awareness of key information that is only displayed on HDDs
(e.g., powerplant indications, alerting messages, and airplane configuration indication). The applicant should describe which pilot scans the head-down instrument indications and how often. For any case in which at least one pilot is not scanning the head-down instruments fulltime, the design should have compensating design features that ensure an equivalent level of timeliness and awareness of the information provided by the head-down visual indications.
F.6.3.3 Alerts. The design should effectively compensate for any cautions and warnings that do not have visual indications in the HUD that are equivalent to the head-down primary flight display. The purpose of the compensating design features is to make the pilot using the HUD aware of the alerts so there are no additional delays in awareness and response time.
The flightcrew should be able to respond to alerts without any reduction in task performance or degraded safety.
F.6.3.4 Reassessment. The applicant should globally reassess the alerting functions to ensure that the flightcrew is aware of alerts and responds to them in a timely manner. The reassessment should review the design and techniques, the alerting attention-getting properties (e.g., visual master warning, master caution, and aural alerts), and other alerts in the flight F-17
Appendix F deck. The flightcrew’s awareness of alerts might differ between singleand dual-HUD installations. With a dual-HUD installation, there may be periods when neither pilot is scanning the instrument panel. With a single- HUD configuration, the PNF refers only to the head-down instrument panel and may have responsibility for monitoring indications on that panel. With dual-HUD configurations, both pilots’ attention may be turned to their HUDs, and they might miss an alert that would otherwise be plainly visible to a pilot not using a HUD.
F.7 Flight Data Recording.
Flight data recorders must record the minimum data parameters required by §§ 25.1459(e) and 121.344. Optionally, the flight data recorders may also record other information regarding unique operating characteristics of the HUDs. For example, they may include information such as the mode in which the HUD was operating, the status
(e.g., in use or inoperative), and if the display declutter mode was operating.
F.8 Continued Airworthiness.
Sections 25.1309 and 25.1529 and appendix H to part 25 require instructions for the continued airworthiness of a display system and its components. The content of the instructions depends on the type of operation and intended function of the HUD.
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Appendix G APPENDIX G. WEATHER DISPLAYS.
G.1 Introduction.
G.1.1 Purpose.
This appendix provides additional guidance for displaying weather information in the flight deck. Weather displays provide the flightcrew with additional tools to help make decisions based on weather information.
G.1.2 Examples.
Sources of weather information may include, but are not limited to, onboard weather sensors, data-linked weather information, and pilot/air traffic reports. The information from these sources can be displayed in a variety of graphical or text formats. Because many sources of weather information exist, it is important that the applicant identify the source of the information, assess its intended function, and apply the guidance contained within this AC.
G.2 Key Characteristics.
In addition to the general guidelines provided in the body of this AC, the following guidelines should be considered when establishing the intended functions of weather displays.
G.2.1 Unambiguous Meanings.
The meaning of the presentations (e.g., display format, colors, labels, data formats, and interaction with other display parameters) should be clear and unambiguous. The flightcrew should not misunderstand or misinterpret the weather information.
G.2.2 Color.
G.2.2.1 The use of color should be appropriate to its task and use.
G.2.2.2 The use of color must not adversely affect or degrade the attention-getting qualities of the information as required by Title 14, Code of Federal Regulations (14 CFR) 25.1322(f).
G.2.2.3 Color conventions should be followed (such as the conventions established in ARINC 708A-3, Airborne Weather Radar with Forward Looking Windshield Detection Capability; and AC 20-149A, Installation Guidance for Domestic Flight Information Services – Broadcast).
G.2.2.4 The use of red and yellow must be in compliance with § 25.1322(e).
Compliance can be shown using the guidance in AC 25.1322-1, Flightcrew Alerting, and this AC.
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Appendix G Note 1: AC 20-149A indicates an exclusion to the acceptability of RTCA DO-267A, Minimum Aviation System Performance Standards (MASPS) for Flight Information Services-Broadcast (FIS-B) Data Link, Sections 2.0 and 3.0, for part 25 airplanes.
Note 2: See paragraph 5.8 of this AC for information on guidelines on color progression.
G.2.3 Multiple Sources of Weather Information.
G.2.3.1 The weather display should enable the flightcrew to quickly, accurately, and consistently differentiate among sources of the displayed weather information. Time-critical information should be immediately distinguishable from dated, non-time-critical information.
G.2.3.2 If more than one source of weather information is available, the source of the weather information should be indicated on the selector and the resulting display.
G.2.3.3 When simultaneously displaying information from multiple weather sources (e.g., weather radar and data link weather), the display should clearly and unambiguously indicate the source of that information. In other words, the flightcrew should know the source of the symbol and whether it is coming from data-linked weather or real-time weather sources. These guidelines also apply to symbols (e.g., winds aloft and lightning) that have the same meaning but originate from different weather information sources.
G.2.3.4 If weather information is overlaid on an existing display, it should be easily distinguished from the existing display. It also should be consistent with the information it overlays in terms of position, orientation, range, and altitude.
G.2.3.5 When fusing or overlaying multiple weather sources, the resulting combined image should convey its intended meaning and meet its intended function, regardless of any differences in the sources in terms of image quality, projection, data update rates, data latency, or sensor alignment algorithms, for example.
G.2.3.6 If weather information is displayed on a head-up display, the guidance of this AC including appendix F of this AC should be followed.
G.2.3.7 When the source of the weather information source is not the onboard sensors, some means to identify its relevance (e.g., a time stamp or the age of the product) should be provided. Presenting the product age is particularly important when combining information from multiple weather products. In addition, the effective time of forecast weather should also be provided.
G-2
G.2.3.8 G.2.3.9 G.2.3.10 G.2.3.11 G.2.3.12 G.2.3.12.1 G.2.3.12.2 Appendix G If a weather-looping (animation) display feature is provided, the system should provide the means to readily identify the total elapsed time of the image compilation so the flightcrew does not misinterpret the movement of the weather cells.
For products that have the ability to present weather for varying altitudes
(e.g., potential or reported icing, radar, and lightning strikes), information should be presented that allows the flightcrew to distinguish or identify which altitude range applies to each feature.
Weather information may include a number of graphical and text information features or sets of information (e.g., text and graphical Aviation Routine Weather Reports and winds aloft). The display should provide a means to identify the meaning of each feature to ensure that the information is correctly used.
If the flightcrew or system has the ability to turn a weather information source on or off, the flightcrew should be able to easily determine if the source is on or off.
When weather information is presented in a vertical situation display, the lateral width of the weather swath (like that of the terrain swath) should be carefully considered to ensure that weather information that is relevant to the current phase of flight or flight path is displayed. An unsuitable lateral swath width could either mislead the flightcrew to abort an operation for weather that poses no hazard, or fail to abort an operation when the weather does pose a hazard. If swath dimensions are automatically controlled, then careful consideration should be given to include only the area that would be relevant to the operation. Means may be provided for the flightcrew to select the swath widths that they consider suitable for the phase of flight and prevailing weather conditions. The lateral width of the weather swath (like that of the terrain swath) should be made readily apparent to the flightcrew (e.g., use the same swath as is used for the terrain, or display its boundaries on the plan view weather display).
Generally, if the vertical situation displays terrain and weather at the same time, the choice of flight path-centered or track/heading-centered swath should be consistent. If the weather overlay is designed to show a smaller vertical swath than is represented by the altitude scale, then the boundaries of this swath should be clearly depicted on the display.
Weather information displayed on a vertical situation display should be accurately depicted with respect to the scale factors of the display
(i.e., vertical and horizontal).
Consideration should be given to making the width of the information on the weather display consistent with the width used by other systems, including the Terrain Awareness and Warning System, if displayed. This G-3
Appendix G should not be interpreted as a restriction precluding other means of presentation that can be demonstrated to be superior.
G.3 On-Board Weather Radar Information.
G.3.1 Background.
On-board weather radar provides forward-looking weather detection, including in some cases windshear and turbulence detection.
G.3.2 Minimum Performance Standards.
The display of on-board weather radar information should be in accordance with the applicable portions of RTCA DO-220, Minimum Operational Performance Standards (MOPS) for Airborne Weather Radar with Forward-Looking Windshear Detection Capability. TSO-C63d, Airborne Weather Radar Equipment, allows exceptions to the minimum performance standards of RTCA DO-220 for Radar Equipment Class A and B.
G.3.3 Hazard Detection.
The weather display echoes from precipitation and ground returns should be clear, automatic, timely, concise, and distinct so the flightcrew can easily interpret, analyze, and avoid hazards. The radar range, elevation, and azimuth indications should provide sufficient information for flightcrews to safely avoid the hazard.
G.4 Predictive Windshear Information.
G.4.1 General.
If provided, windshear information should be clear, automatic, timely, concise, and distinct so the flightcrew can easily interpret, detect, and minimize the threat of windshear activity.
G.4.2 Presentation Methods.
When a windshear threat is detected, the corresponding display may be automatically presented or selected by the flightcrew at an appropriate range to identify the windshear activity and minimize the windshear threat to the airplane.
G.4.3 Pilot Workload.
Pilot workload necessary for the presentation of windshear information should be minimized. When the flight deck is configured for normal operating procedures, it should not take more than one action to display the windshear information.
G.4.4 Windshear Threat Symbol.
The size and location of the windshear threat symbol should allow the flightcrew to recognize the dimension of the windshear and its position. The symbol should be presented in accordance with RTCA DO-220.
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Appendix G G.4.5 Relative Position to the Airplane.
The relative position and azimuth of the windshear threat with respect to the nose of the airplane should be displayed in an unambiguous manner.
G.4.6 Range.
The range selected by the flightcrew for the windshear display should allow the flightcrew to distinguish the windshear event from other information. Amber radial lines may be used to extend from the left and right radial boundaries of the icon extending to the upper edge of the display.
G.5 Safety Aspects.
G.5.1 Functional Hazard Assessment.
Both the loss of weather information and the display of misleading weather information should be addressed in the functional hazard assessment (FHA). In particular, the FHA should address failures of the display system that could result in the loss of the display and failures that could result in the presentation of misleading weather information.
G.5.2 Misleading Information.
The functional hazard assessment should address the effects of displaying misleading information. In accordance with chapter 4 of this AC, the display of misleading weather radar includes information that would lead the flightcrew to make a bad decision or introduce a potential hazard. Examples include—but are not limited to—storm cells displayed in the incorrect position, at the wrong intensity, or mis-registered in the case of a combined (e.g., fused) image.
G-5
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