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The Cessna Citation Mustang uses a 12-inch phased array antenna that is fully stabilized to accommodate 30º of pitch and roll.
To focus radar scanning on specific areas, Sector Scanning offers pilot-adjustable horizontal scan angles of 20º, 40º, 60º, or 90º. A vertical scanning function helps to analyze storm tops, gradients, and cell buildup activity at various altitudes.
Radar features include:
• Extended Sensitivity Time Constant (STC) logic that automatically correlates distance of the return echo with intensity, so cells do not suddenly appear to get larger as they get closer.
• WATCH® (Weather ATtenuated Color Highlight) helps identify possible shadowing effects of short-range cell activity, identifying areas where radar return signals are weakened or attenuated by intense precipitation (or large areas of lesser precipitation) and may not fully reflect the weather behind a storm.
• Weather Alert that looks ahead for intense cell activity in the 80-320 nm range, even if these ranges are not being monitored.
Principles of Pulsed Airborne Weathereather Radaradar
The term RADAR is an acronym for RAdio Detecting And Ranging. Pulsed radar locates targets by transmitting a microwave pulse beam that, upon encountering a target, is reflected back to the radar receiver as a return echo. The microwave pulses are focused and radiated by the antenna, with the most intense energy in the center of the beam and decreasing intensity near the edge. The same antenna is used for both transmitting and receiving. The returned signal is then processed and displayed on the G1000 MFD.
Radar detection is a two-way process that requires 12.36 μs for the transmitted microwave pulses to travel out and back for each nautical mile of target range. It takes 123.6 μs for a transmitted pulse to make the round trip if a target is ten nautical miles away.
Airborne weather radar should be used to avoid severe weather, not for penetrating severe weather. The decision to fly into an area of radar targets depends on target intensity, spacing between the targets, aircraft capabilities, and pilot experience. Pulse type weather radar detects only precipitation, not clouds or turbulence. The display may indicate clear areas between intense returns, but this does not necessarily mean it is safe to fly between them. Only Doppler radar can detect turbulence.
Airborne weather radar has other capabilities beyond weather detection. It also has the ability to detect and provide distance to cities, mountains, coastlines, rivers, lakes, and oceans.
312 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
NEXRAD and Airborne Weathereather Radaradar
Both Airborne Weather Radar and NEXRAD measure weather reflectivity in decibels (dB). A decibel is a logarithmic expression of the ratio of two quantities. Airborne Weather Radar measures the ratio of power against the gain of the antenna, while NEXRAD measures the energy reflected back to the radar, or the radar reflectivity ratio.
Both systems use colors to identify the different echo intensities, but the colors are not interchangeable. Airborne color radar values used by Garmin Airborne Color Weather Radar should not be confused with NEXRAD radar values.
Antenna Beam Illuminationllumination
The radar beam is much like the beam of a spotlight. The further the beam travels, the wider it becomes. The radar is only capable of seeing what is inside the boundaries of the beam. The figure below depicts a radar beam’s characteristics. The figure illustrates vertical dimensions of the radar beam, although the same holds true for the horizontal dimensions. In other words, the beam is as wide as it is tall. Note that it is possible to miss areas of precipitation on the radar display because of the antenna tilt setting. With the antenna tilt set to zero in this illustration, the beam overshoots the precipitation at 15 nautical miles.
Figure 6-36 Radar Beam from a 12 inch Antenna080Altitude (x1000 ft.)30045607590Range (nautical miles)Half Power at Beam SidelobesAntenna at Zero Tilt18,000 ft.18,000 ft.Max Power at Beam Center158°
The curvature of the earth can also be a factor in missing areas of precipitation, especially at range settings of 150 nautical miles or more. Here the beam overshoots the precipitation at less than 320 nautical miles.
320 nm
Figure 6-37 Radar Beam in Relation to the Curvature of the Earth
190-00494-02 Rev. B Garmin G1000 Pilot’s Guide for the Cessna Citation Mustang 313
Hazard Avoidance voidance voidance
SYSTEM
OVERVIEW
FLIGHT
INSTRUMENTS EICAS AUDIO PANEL
& CNS
FLIGHT
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Cessna Citation Mustang G1000 Integrated Flight Dec(110)
