Home' RTCA Documents for Review : DO-213A Change 1 Contents Appendix B
DO-213A Change 1
© 2018 RTCA, Inc.
This appendix provides general guidelines for proper radome maintenance and repair.
Much of this material is found in AC 43-14, Maintenance of Weather Radar Radomes 
A radome’s performance is dependent on its ability to provide physical protection to the
weather radar antenna, and on its electrical ability to provide two-way transmission of radar
signals with minimum distortion or absorption. Radar efficiency, resolution, and accuracy
of display depend upon a clear, non-distorted, reflection-free antenna view through the
radome. For forward-looking windshear/avoidance radar systems, radome performance is
even more critical. The goal of any repair and maintenance procedure is to preserve the
performance of the original radome design.
When repairing a damaged radome, take special care to maintain the radome's electrical
thickness. This critical parameter depends on the radome's physical thickness, the operating
frequency of the radar, and the types of material (with intrinsic dielectric constants and loss
tangents) and construction used. A very small variation in physical thickness may cause a
sizable variation in electrical thickness that will degrade the radome's performance.
There are two general types of radomes used in civil aviation: the "thin wall”, and the
"sandwich". Thin-wall radomes are thin compared with the wavelength of the radar. They
are generally useful when the radar frequency is low enough to allow a skin thickness that
will satisfy the structural requirements. Sandwich radomes consist of two or more
composite (e.g., epoxy-fiberglass) skins or facings separated by a dielectric core. The core
may consist of non-metallic honeycomb sections, hollow flutes, or plastic foam. The
thickness of the facings and core depends on the radar operating frequency, and on the
dielectric constant and loss tangent of the facings, core, paint system, and antistatic
One frequent cause of radome damage is the result of a dielectric breakdown process
caused by static charge building up on the radome surface. When these electric fields are
high enough, voltage will puncture the radome wall, forming almost imperceptible
pinholes. Continued current transfer through the pinhole can produce an even larger hole
that is readily apparent. Any hole, regardless of size, can cause major damage to a radome
because moisture can then enter the radome wall, and because pressure changes during
altitude cycling cause internal delamination. If the moisture freezes, damage that is more
serious may occur. If enough moisture collects, distortion of the radar antenna's radiation
pattern can occur, with the transmitted signals and return echoes seriously attenuated. Other
types of damage, including punctures, dents, and scratches can be caused by: impact with
stones, hail or birds; improper handling of the radome when it is removed for radar antenna
maintenance; impact with ground service vehicles; or landing with the landing gear up or
with inadvertent nose gear retraction. These types of damage are easily found by inspecting
the radome outside and inside.
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