First....
First, flight through the tops of thunderstorms should be avoided.
There are several reasons why....turbulence, icing, etc.
Second point, turbulence can be heavy even as high as 5000 feet
above the tops of thunderstorms. Therefore, in most cases (most
thunderstorms), attempting to top turbulence of thunderstorms in
an airliner is futile....and possibly dangerous (buffet margin?)
Third, having said the above, proper use of RADAR is critical. You
have to be able to detect and then circumnavigate (usually) the
storm.
Tilt is the most critical control on the RADAR control panel. Since
RADAR does not very well "paint" some forms of moisture, it
is important to adjust the RADAR tilt to point the signal to the
most reflective section of the storm. This is approximately the
freezing level....maybe slightly below.
Thus, in order to do this, the tilt angle is dependent on the aircraft's
altitude and the distance in front of the aircraft the storm is that you're
trying to paint.
Example...if you're at FL250 and climbing...and looking at a group of
storms, say, 100 miles in front of you, you're tilt will be relatively
high.
In contrast, if you're at FL390 and trying to paint a storm, say, 20
miles in front of you, your tilt will be pretty low.
Again, you want to point the signal at the most reflective part of the
storm.
Some use the technique of adjusting the gain....and running the tilt
to a relatively high angle. This is not recommended....please refer to
chapter six of Getting to Grips with Surveillance. There are several
important functions that you lose when you bring the gain out of
AUTO or CAL. Don't misunderstand....it is OK to move the gain out
of AUTO or CAL....for temporary analysis of the weather....but, as soon
as finished with that, go back to AUTO/CAL. The functions you lose
when out of AUTO/CAL vary with RADAR brand (i.e. Honeywell or
Collins) and RADAR type (i.e. Multi-Scan or non-Multi-Scan).
The previous-mentioned pubs have really good information.
Fly safe,
PantLoad