12-32
Garmin GTN 725/750 Pilot’s Guide
190-01007-03 Rev. D
Foreword
Getting
Started
Audio &
Xpdr Ctrl
Com/Nav
FPL
Direct-To
Proc
Charts
Wpt Info
Map
Traffic
Terrain
Weather
Nearest
Services/
Music
Utilities
System
Messages
Symbols
Appendix
Index
12.3
Weather Radar
The GTN 7XX can display weather radar from a Garmin GWX system or from
selected 3rd party radars. Only one weather radar system may be interfaced to
the system. For detailed information on the operation of 3rd party radars, refer
to their specific documentation.
12.3.1 Garmin GWX Radar Description
The Garmin GWX 68 and GWX 70 Airborne Color Weather Radars combine
excellent range and adjustable scanning profiles with a high-definition target
display.
To focus radar scanning on specific areas, Sector Scanning offers pilot-
adjustable horizontal scan angles of 20º, 40º, 60º, or 90º (up to 120º with the
GWX 70). A vertical scanning function helps to analyze storm tops, gradients,
and cell buildup activity at various altitudes.
See the documentation of each radar for specific features.
12.3.1.1 Principles of Pulsed Airborne Weather Radar
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 then 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 GTN 7XX.
Radar detection is a two-way process that requires 12.36 micro-seconds for
the transmitted microwave pulses to travel out and back for each nautical mile
of target range. It takes 123.6 micro-seconds for a transmitted pulse to make the
round trip if a target is 10 NM away.
The GWX 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.
Summary of Contents for GTN 725
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