Garmin International Inc 0126000 Manuel D’Utilisation

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The Garmin GWX 70 Airborne Color Weather Radar is a solid-state doppler radar with forty watts of output 

power.  It combines excellent range and adjustable scanning profiles with high-definition target displays.  The 
effective pulse length is 27.31 microseconds (µs), and the system optimizes the pulse length to maximize 
resolution at each range setting.  This reduces the targets smearing together on the displays for better target 
definition at close range.

The aircraft uses a 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.

• Turbulence Detection presents areas of turbulence associated with precipitation using the color magenta.

• 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.

• Altitude-Compensated Tilt (ACT) management which automatically adjusts the antenna tilt as the aircraft

altitude changes.

• Ground Clutter Suppression (GCS) removes ground clutter from the displays.

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.

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.

The GWX 70, has the capability to detect the velocity of precipitation moving toward or away from the radar 

antenna.  As the radar pulse beam strikes a moving object, the frequency of the returned echo shifts in relation 
to the speed at which the object is moving.  This effect is analogous to the audibile pitch change observed when 
an emergency vehicle’s siren gets closer and then moves further away. Doppler radar employs this effect to
detect areas of precipitation moving at a high rate of speed (indicative of turbulence), and to determine when 
an object, such as the ground, is stationary.  This information can be used to suppress ground clutter.

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 

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7/25/2012   3:14:44 PM