BendixKing IN-862A System RDR-2100 - Manual (Page 22)

RADOMES
A radome is a covering that shields the radar antenna from hostile envi-
ronments, such as fast moving air, rain, bugs, and ice. It allows the
microwave energy to pass through relatively undisturbed. This means
that very little of the microwave energy passing through it will be
absorbed, reflected, or redirected as a result of it’s presence. Some
radomes closely approximate this definition, while others do not.
Here are some faults which can occur in radomes:
1. A pitted honeycomb radome can result from being struck by high
velocity projectiles, such as rain, ice, sand, bugs, etc. Once the
surface integrity has been broken, water intrusion can occur and
cause significant radar signal loss.
2. A poorly sealed plastic radome nose boot which has allowed
moisture to be trapped behind it.
3. Paint containing metallic particles mistakenly applied to all or part
of the radome.
4. An improperly fabricated fiberglass radome.
5. A poorly repaired “ding” on the radome.
6. An object, usually metallic, located inside the radome and in the
path of part of the transmitted microwave energy.
As a result of items 5 and 6 above, a “phantom ring” may appear on the
radar display. Normally the cause is an obstruction in the bottom of the
radome. This obstruction can cause some of the radiated energy to be
directed down to the ground instead of in the forward direction.
Reflective material in the top of the radome can result in the same situa-
tion. In either case, energy returns from the same direction that it was
transmitted causing an “altitude ring” to be presented on the radar dis-
play. It is called an altitude ring because it moves in and out as the air-
craft changes altitude.
Items 1, 2, 3, and 4 can result in radar performance problems while
checking out as “no trouble found” at the repair center. The radome is
blocking too much energy.
Care must be exercised to be sure that only qualified personnel perform
repairs on the radome. Also, it is time well spent during preflight to
include checking the radome to be sure it remains in good repair. When
examining the radome, be certain the radar is not transmitting
microwave energy. See MPEL (Maximum Permissible Exposure Levels)
in the Appendix.
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Effective Date: 9/98 RDR 2100 Pilot's Guide: Rev 1
Theory of Operation
RDR 2100 PG 3/12/07 3:45 PM Page 18