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At the top this of a thunder cloud hardly no reflections are generated because
it consists only of dry hail up there. As thunderstorm can reach high altitudes
they may grow up into your flightlevel. But there you will only cross the top
third of the cloud which will not be displayed on the radar when flying with
neutral tilt.
But tops of thunderstorm should be avoided because of the turbulent air above
them, and the hail particles within them. Therefore Collins has included the
thunderstorm OverFly Protection (OFP).
This function continuously changes the tilt and looks for high reflective
thunderstorm bodies (“bottom third’s”)
Independed of where your set tilt crosses the thunderstorm now, it always
draws the saved bottom image instead. So you always see great red areas
where storms are present, even if they would not create reflections with your
current settings.
This function is only available with in the PAC range, that is fixed to 80NM.
Other clouds than thunderstorms may also create reflections. Towering
cumulus clouds have the same characteristics as thunderstorms (also consists
of the three precip. parts) but reflections are only in the green and yellow
range.
Lower cumulus clouds also can create reflections because they consist of
water drops anyway. But density and turbulence is much lower than in thunder
clouds.
Additional low sized clouds (nimbostratus and similar) that consist of raindrops
also generate reflections. In most cases there is also downpour below them.
Thunder cloud sensed through the thunder cloud sensed through
bottom third the mid ( far reflections not
seen because of the tilt angle)
AOG AOG SA_WXR Users Manual Revision 1.6
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Thunderstorm sensed through the top, OFP is on, bottom image is
only weak green reflections drawn, although beam goes
through the top of the cloud.
Image is limited to 80NM since
PAC.
4.6 Turbulence Detection
The intensity of turbulence within clouds can also be displayed. The turbulence
is calculated out of the velocity changes for the reflections. This turbulence can
only be measured within clouds that generate normal reflections. So only
precipitation based turbulence can be displayed, gusty winds and other air
turbulence can not be displayed. Following color code is used: dark magenta
means moderate turbulence, intense magenta means serve turbulence. The
turbulence image is an overlay to the normal weather radar image so if no
turbulence is measured, the normal RGB WX image is drawn. The turbulence
detection is limited to a Range of 40NM.
5 Limitations and simplifications
A few simplifications were necessary for weather radar display in FS9. First of
all is the cloud position. In reality red drawn holes are at same position as the
cloud of course. As I have found no reasonable solution for finding out the
randomly positioned clouds, I can only render a exact area where a certain
cloud type and other meteorological data is present. More than 12000 areas
cover the whole world. Out of many parameters, the exact weather area is
drawn with typical reflections for the weather situation. As you use the radar
you will see that it is far enough for save flight operation. But keep in mind that
flying through exact red holes does not avoid flying through a thunder cloud.
The other limitation is the ground elevation model that is used. I covers only
elevations of stations and calculates ground reflections out of that. Mountains
etc. are not modeled.
AOG AOG SA_WXR Users Manual Revision 1.6
http://members.chello.at/addongauges Page - 14 -
So flying over LSZH (Zurich Swiss) when heading direction LIPB (Bolzano
Italy) the LSZS (Samedan Swiss) will bring you ground reflections, because it
crosses the beam path. As GCS is switched off, a possible thunderstorm in
Bolzano is hidden or better embedded between the LSZS Ground reflection
and the LIBP ground reflection. Increasing the tilt and/or enabling the GCS
function would eliminate this effect.
ground clutter at LOWI when looking eastern heading, some stations are
higher. Tilt 1.75° so it will only hit that ground that is higher as LOWI.
6 Using the radar
After this introduction lets go to the practical part now. Your are on the ground
now and want to start your flight.
Let the radar switched off at the gate. check the FMC Display/Radar Display
toggle when used.
The weather information is refreshed every 1 minute at least, depending on
range and CPU speed. But image is recalculated after every beam refresh
cycle. So if you manually change the weather completely then wait at little to
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