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294 Garmin G1000 Pilot’s Guide for the Cessna Citation Mustang 190-00494-02 Rev. B
Hazard Avoidance voidance voidance
SYSTEM
OVERVIEW
FLIGHT
AUDIO PANEL EICAS INSTRUMENTS
& CNS
FLIGHT
MANAGEMENT
HAZARD
ADDITIONAL AFCS AVOIDANCE
INDEX APPENDICES FEATURES
eflectivity
Reflectivity is the amount of transmitted power returned to the radar receiver. Colors on the NEXRAD display directly correlate to the level of detected reflectivity. Reflectivity as it relates to hazardous weather can be very complex.
The role of radar is essentially to detect moisture in the atmosphere. Simply put, certain types of weather reflect radar better than others. The intensity of a radar reflection is not necessarily an indication of the weather hazard level. For instance, wet hail returns a strong radar reflection, while dry hail does not. Both wet and dry hail can be extremely hazardous.
The different NEXRAD echo intensities are measured in decibels (dB) relative to reflectivity (Z). NEXRAD measures the radar reflectivity ratio, or the energy reflected back to the radar receiver (designated by the letter Z). The value of Z increases as the returned signal strength increases.
NE
XRAD Limitations
NEXRAD radar images may have certain limitations:
• NEXRAD base reflectivity does not provide sufficient information to determine cloud layers or precipitation characteristics. For example, it is not possible to distinguish between wet snow, wet hail, and rain.
• NEXRAD base reflectivity is sampled at the minimum antenna elevation angle. An individual NEXRAD site cannot depict high altitude storms at close ranges. It has no information about storms directly over the site.
• When zoomed in to a range of 30 nm, each square block on the display represents an area of four square kilometers. The intensity level reflected by each square represents the highest level of NEXRAD data sampled within the area.
Figure 6-11 NEXRAD Data - ZoomedEach block covers an Area of 4 sq. km
190-00494-02 Rev. B Garmin G1000 Pilot’s Guide for the Cessna Citation Mustang 295
Hazard Avoidance voidance voidance
SYSTEM
OVERVIEW
FLIGHT
INSTRUMENTS EICAS AUDIO PANEL
& CNS
FLIGHT
MANAGEMENT
HAZARD
AVOIDANCE AFCS ADDITIONAL
FEATURES APPENDICES INDEX
The following may cause abnormalities in displayed NEXRAD radar images:
• Ground clutter
• Strobes and spurious radar data
• Sun strobes (when the radar antenna points directly at the sun)
• Interference from buildings or mountains, which may cause shadows
• Metallic dust from military aircraft, which can cause alterations in radar scans
NE
XRAD Limitations (Canada)
• Radar coverage extends to 55ºN.
• Any precipitation displayed between 52ºN and 55ºN is displayed as mixed because it is unknown.
Figure 6-12 NEXRAD Data - Canada Precipitation Above 52ºNNo Coverage Above 55ºN
296 Garmin G1000 Pilot’s Guide for the Cessna Citation Mustang 190-00494-02 Rev. B
Hazard Avoidance voidance voidance
SYSTEM
OVERVIEW
FLIGHT
AUDIO PANEL EICAS INSTRUMENTS
& CNS
FLIGHT
MANAGEMENT
HAZARD
ADDITIONAL AFCS AVOIDANCE
INDEX APPENDICES FEATURES
ECHO TOPs Noteote: Display of Echo Tops is mutually exclusive with Cloud Tops and NEXRAD.
Echo Tops data shows the location, elevation, and direction of the highest radar echo. The highest radar echo does not indicate the top of a storm or clouds; rather it indicates the highest altitude at which precipitation is detected. Information is derived from NEXRAD data.
Figure 6-13 Echo Tops Data
190-00494-02 Rev. B Garmin G1000 Pilot’s Guide for the Cessna Citation Mustang 297
Hazard Avoidance voidance voidance
SYSTEM
OVERVIEW
FLIGHT
INSTRUMENTS EICAS AUDIO PANEL
& CNS
FLIGHT
MANAGEMENT
HAZARD
AVOIDANCE AFCS ADDITIONAL
FEATURES APPENDICES INDEX
Displaying Echo Tops information:
1) Select the Weather Data Link Page with the FMS Knob.
2) Select the ECHO TOPS Softkey.
To display the Echo Tops legend, select the LEGEND Softkey when Echo Tops is selected for display. Since Echo Tops and Cloud Tops use the same color scaling to represent altitude, display of these weather products is mutually exclusive. When Echo Tops is activated, NEXRAD and Cloud Tops data are removed.
Figure 6-14 ECHO TOPS LegendNo Radar Coverage
The display of radar coverage is always active when either NEXRAD or ECHO TOPS is selected. Areas where NEXRAD radar coverage and Echo Tops information is not currently available or is not being collected are indicated in grayish-purple. Radar capability exists in these areas, but it is not active or is off-line.
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Cessna Citation Mustang G1000 Integrated Flight Dec(106)
