Section 5: Principles Of Weather Radar Use; Weather Radar Principles - Honeywell IntuVue RDR-4000 Pilot's Manual

IntuVue RDR-4000 Weather Radar Pilot's Guide

SECTION 5: PRINCIPLES OF WEATHER RADAR USE

WEATHER RADAR PRINCIPLES

Airborne weather avoidance radar, as its name implies, is for avoiding
severe weather - not for penetrating it. Whether to fly into an area of
radar echoes depends on echo intensity, spacing between the echoes,
and the capabilities of both pilot and aircraft. Remember that weather
radar detects only precipitation; it does not detect minute cloud droplets.
Therefore, the radar display provides no assurance of avoiding
inclement weather in clouds and fog. Your display may be clear
between intense echoes; this clear area does not necessarily mean you
can fly between the storms and maintain visual separation from them.
Weather radar detects droplets of precipitation size. The strength of the
radar return (echo) depends on drop size, composition, and amount of
water. Water particles return almost five times as much signal as ice
particles of the same size. This means that rain is more easily detected
than snow, although at times large, wet snowflakes may give a strong
return.
Hail usually has a film of water on its surface; consequently, a hailstone
is often reflected as a very large water particle. Because of this film and
because hailstones usually are larger than raindrops, thunderstorms
with large amounts of wet hail return stronger signals than those with
rain. Although wet hail is an excellent reflector of radar energy, some
hail shafts are extremely
small (100 yards or less) and
make poor radar targets. If
hailstones are cold and dry,
they give poor returns and
might not appear on the
display.
060-4492-000 Principles of Weather Radar Use
Rev 7, February 2015 39