737 Flight Crew Operations Manual
Flight Management, Navigation -
Navigation Systems Description
Boeing Proprietary. Copyright © Boeing. May be subject to export restrictions under EAR. See title page for details.
D6-27370-866-EGP 11.20.11
WXR-2100 Multiscan Radar
A MultiScan weather radar emulates an ideal radar beam by taking information
from different radar scans and merging the information into a total weather
picture. Ground clutter suppression algorithms are then used to eliminate ground
clutter. The result is the ability for flight crews to view all significant weather from
0 to 320 NM on a single display that is essentially clutter free. With the multiscan
process two scans are taken, each optimized for a particular region in front of the
aircraft. In general, the upper beam detects intermediate range weather while the
lower beam detects short and long range weather by automatically adjusting the
beams tilt and gain settings. The information is then stored in a temporary
database. When the captain or first officer selects a range, the computer extracts
the appropriate portions of the desired information, merges the data, then
eliminates the ground clutter. The result is an optimized weather display for
whichever range scale the flight crew selects. During automatic operation,
multiscan uses variable gain that is based on atmospheric temperature profiles to
compensate for variations in geographic location, time of day, and altitude in order
to optimize weather returns in all phases of flight. Gain is thus adjusted to suit the
environment in which the aircraft is flying and provide the optimum weather
picture in the prevailing conditions.
The Multiscan Radar includes the following features:
Path Attenuation Compensation (PAC) Alert places a yellow arc on the outer most
range scale to warn the pilot if intervening rain fall has created an attenuated area.
PAC Alert is operative whenever the radar is being operated in CAL gain and the
aircraft is within 80 NM of a thunderstorm. PAC Alert is activated during both
automatic and manual radar operation.
Oceanic Weather Reflectivity Compensation uses aircraft navigation inputs to
identify oceanic regions and adjusts gain and tilt to account for the decreased
reflectivity of oceanic thunderstorms. Thunderstorm thresholds are adjusted to
more accurately represent the true thunderstorm threat to the aircraft.
March 27, 2014
To Next Page
Loading...
