Home' RTCA Documents for Review : DO-213A Change 1 Contents Appendix B
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DO-213A Change 1
Maintenance And Repair
The following steps are recommended for determining the extent of radome
1. Do not use chemical paint strippers to remove radome decorative paint before
making damage evaluations. Damage to the radome’s resin system will result.
2. Visually examine the nose radome for holes, scuffs, cracks, blisters, or
delamination, and for entry of oil, fuel, dirt and other foreign matter.
3. Check for any delamination of plies. Delamination can be detected by
instrumented non-destructive inspection methods or by a tap test. For the tap test,
use a solid metal disk (e.g., a coin) and tap the suspected damage area lightly but
firmly. Void areas will produce a dull sound, as opposed to a sharp ring on a solid
4. Check for moisture in the honeycomb core by radiographic or infrared
thermographic methods (e.g., a "calibrated" moisture meter or infrared photo
camera). If there is moisture ingestion, determine the extent of contamination and
proceed with appropriate repair steps. This will involve removal of the inner skin
over the wet area, drying the radome at 125 degrees Fahrenheit (maximum) in an
air-circulating oven, and replacing with a new inner skin. All epoxy resins absorb
some moisture and the rate of moisture absorption varies with relative humidity
and temperature. For skin contamination only, drying may be achieved with
electric blankets, radiant lamps, or a vacuum bag over the wet area. Paper tissues
over the area to be dried will show water coming out of the resin. Continue drying
until moisture meter readings are in the green band. Perform the required tests on
the radome if the contaminated area exceeds the size limits given in Table 2-3.
Failure to dry the damaged area will lead to bond failure. Since the dielectric
constant of water is 81, radar performance degradation will be significant if the
area is wet.
5. Check for damage to lightning diverter strips and the glide slope director element,
where applicable (i.e., when the aircraft's glide slope antenna is located in the nose
bulkhead). Check the provision for electrical bonding of the lightning diverter
strips to the airframe.
Make all repairs to radomes using techniques specified in the appropriate structural repair
or maintenance manuals and at a governmental agency approved repair facility. Restore
the repaired radome to its original electrical thickness, structural strength and aerodynamic
shape and smoothness.
If repair materials and facilities are not immediately available and the damaged area does
not exceed one square inch, temporarily protect the unrepaired damage from penetration
by water or other foreign matter by sealing with non-metallic tape. Thoroughly clean the
damaged radome surface with isopropyl alcohol and wipe it dry before applying the tape.
Tape repair is satisfactory if ground operation of the radar appears normal. Note that
excessive layering of tape reduces radar efficiency. Take care to avoid overlapping by more
than three layers of tape in any given area. Repair all damage at the earliest opportunity.
Before a repair is undertaken, dry the radome and prepare the damaged surface. Surface
preparation involves removing any paint by sanding very carefully with appropriate
abrasive paper. After these steps, wipe the surface free of any dust and debris. Ideally, carry
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