Home' RTCA Documents for Review : DO-213A Change 1 Contents Appendix A
DO-213A Change 1
© 2018 RTCA, Inc.
The causes of degradation of a radome's electrical and/or structural performance are:
Rain Erosion - High velocity rain will erode the paint system, then the outer radome
structure in the forward area of the radome. Protection of the structure against rain erosion
consists of maintaining a good paint layer on the radome, and/or installing an appropriate
rain-erosion paint system, a thin polyurethane film, or a rubber boot on the radome nose.
Impact Damage - Impact damage from small hail and small bird strikes can be quite
inconspicuous. If the flight or ground crew does not notice this type of damage, and if there
is a puncture to the radome's outer surface, moisture will get into the core area of the radome
and reduce the electrical performance of that portion of the radome. With time and
subsequent flights above the freezing level, the alternating freezing and thawing of the
water will cause micro-cracking of the structure and allow moisture to propagate, thus
enlarging the area of moisture on the radome.
Larger impact damage such as large hail, large bird strikes (ducks, etc.), or ground vehicles
(tugs, etc.) is readily noticed by the flight or ground crew, and the radome is then removed
With current technology, protection against impact damage has not yet been found for the
"A-sandwich" (facing/core/facing) type of structure with which commercial radomes are
Lightning Strike Damage - Most radomes are equipped with a lightning diverter system.
Nose mounted radomes can be struck by lightning on its way to the antenna or other
conductive structure within the radome. The damage to the radome can range from a hole
through the radome wall a few thousandths of an inch in diameter to a four-inch or larger
hole, depending on the current level of the strike. In addition, the heating of the core can
delaminate (disbond) the inner facing-to-core bond in an area the size of a football or larger.
Lightning has also been known to travel between the inner skin and core to the rear of the
radome, delaminating an area of one foot by four feet, severely impacting the structural
integrity of the affected area.
Even radomes that have a lightning diverter system are occasionally subject to a lightning
strike that ignores the lightning diverters and punctures the radome. Lightning diverters
must be positioned for minimum impact on the radome's electrical performance
(transmission efficiency, sidelobe levels, etc.) . They should be placed to provide effective
lightning protection for the conductive items contained within the radome. The finished
radome with lightning protection system should be subjected to a lightning test program to
determine that the system is satisfactory.
Static Burns - A static burn is a small puncture in the radome wall caused by a static
electricity charge on the radome's outer surface. The charge builds up to a level that will
puncture the radome wall on its way to the antenna or other conductive structure within the
radome. Visually, the damage looks minor, as though a straight pin had been driven through
the radome wall by a small tack hammer. Some static burns will have the surrounding inner
and/or outer radome surface blackened from the exposure. The size of this blackening
ranges from 0.12 inches to 0.25 inches.
Such a puncture will allow moisture to enter the radome. With time and subsequent
flights, damage and impact on the radome's electrical performance will occur as
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