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the wing in the direction of the intended turn and look.
36.6.3Low−wing Airplane.Momentarily lower
the wing in the direction of the intended turn and look.
36.6.4Appropriate clearing procedures should
precede the execution of all turns including
chandelles, lazy eights, stalls, slow flight, climbs,
straight and level, spins, and other combination
maneuvers.
37. Surveillance Systems
37.1 Radar
37.1.1Capabilities
37.1.1.1Radar is a method whereby radio waves are
transmitted into the air and are then received when
they have been reflected by an object in the path of the
beam. Range is determined by measuring the time it
takes (at the speed of light) for the radio wave to go
out to the object and then return to the receiving
antenna. The direction of a detected object from a
radar site is determined by the position of the rotating
antenna when the reflected portion of the radio wave
is received.
37.1.1.2More reliable maintenance and improved
equipment have reduced radar system failures to a
negligible factor. Most facilities actually have some
components duplicated − one operating and another
which immediately takes over when a malfunction
occurs to the primary component.
37.1.2Limitations
37.1.2.1It is very important for the aviation
community to recognize the fact that there are
limitations to radar service and that ATC controllers
may not always be able to issue traffic advisories
concerning aircraft which are not under ATC control
and cannot be seen on radar. (See FIG ENR 1.1−21).
FIG ENR 1.1−21
Limitations to Radar Service
Precipitation Attenuation
The nearby target absorbs and scatters so much of the out-going and returning
energy that the radar does not detect the distant target.
AREA BLACKED OUT
BY ATTENUATION
NOT OBSERVED
OBSERVED
ECHO
a)The characteristics of radio waves are such that
they normally travel in a continuous straight line
unless they are:
1)Bent" by abnormal atmospheric phenomena
such as temperature inversions.
2)Reflected or attenuated by dense objects such
as heavy clouds, precipitation, ground obstacles,
mountains, etc.
3)Screened by high terrain features.
b)The bending of radar pulses, often called
anomalous propagation or ducting, may cause many
extraneous blips to appear on the radar operator’s
display if the beam has been bent toward the ground,
or may decrease the detection range if the wave is
bent upward. It is difficult to solve the effects of
anomalous propagation, but using beacon radar and
electronically eliminating stationary and slow
moving targets by a method called moving target
indicator (MTI) usually negate the problem.
AIP ENR 1.1−33
United States of America 15 MAR 07
Federal Aviation Administration Nineteenth Edition
c)Radar energy that strikes dense objects will be
reflected and displayed on the operator’s scope,
thereby blocking out aircraft at the same range and
greatly weakening or completely eliminating the
display of targets at a greater range. Again, radar
beacon and MTI are effectively used to combat
ground clutter and weather phenomena, and a method
of circularly polarizing the radar beam will eliminate
some weather returns. A negative characteristic of
MTI is that an aircraft flying a speed that coincides
with the canceling signal of the MTI (tangential or
blind" speed) may not be displayed to the radar
controller.
d)Relatively low altitude aircraft will not be seen
if they are screened by mountains or are below the
radar beam due to earth curvature. The only solution
to screening is the installation of strategically placed
multiple radars, which has been done in some areas.
e)There are several other factors which affect
radar control. The amount of reflective surface of an
aircraft will determine the size of the radar return.
Therefore, a small light airplane or a sleek jet fighter
will be more difficult to see on radar than a large
commercial jet or military bomber. Here again, the
use of radar beacon is invaluable if the aircraft is
equipped with an airborne transponder. All ARTCC
radars in the conterminous U.S. and many airport
surveillance radars have the capability to interrogate
Mode C and display altitude information to the
controller from appropriately equipped aircraft.
However, there are a number of airport surveillance
radars that do not have Mode C display capability
and, therefore, altitude information must be obtained
　
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