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.
G-4
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
Advisory Circular Feedback If you find an error in this advisory circular (AC), have recommendations for improving it, or have suggestions for new items/subjects to be added, you may let us know by (1) emailing this form to 9-AWA-AVS-AIR500-Coord@faa.gov or (2) faxing it to the attention of the Aircraft Certification Service Directives Management Officer at (202) 267-3983.
Subject: Date:
Please check all appropriate line items:
☐ An error (procedural or typographical) has been noted in paragraph on page .
☐ Recommend paragraph on page be changed as follows:
☐ In a future change to this AC, please cover the following subject:
(Briefly describe what you want added.)
☐ Other comments:
☐ I would like to discuss the above. Please contact me.
Submitted by: Date: