Chapter. 13. Penetration Through Pressurized Structure




Chapter. 13. Penetration Through Pressurized Structure

Electrical Wire Bundles And Coaxial Cable Feed Through Pressurized Structure 


This section describes typical methods for sealing aircraft openings where wires and coaxial cable are installed through pressurized structure.

a. Assure that the strength of the structure is maintained when installations require additional opening.

b. The aircraft manufacturer's data may specify the size and location where additional openings are permitted and the reinforcement required to maintain the design strength of the affected area.

c. The manufacturer's data may also recommend the specific sealant to be used and provide instructions for the application.

Caution: Sealant and solvents may contain toxic and/or flammable components. Avoid inhalation of vapors and supply adequate ventilation. Wear appropriate respiratory protection while using these materials in confined areas. Avoid contact with the skin and eye.


Use a cleaning solvent and clean a larger area than required for the fairlead or connector. Remove solvent by blasting with dry air and wiping with a clean soft cloth.


Seal electrical wire bundles and connectors where they pass through the opening in the pressurized structure.

a. Separate and coat each wire with sealant over the length which is to pass through the fairlead, figure 13.1A. After coating each wire with sealant, pull the wire bundle into position in the fairlead, figure 13.1B. Assure that the fairlead is located on the pressure side of the structure.

b. Apply sealant to the surface of the fairlead which comes in contact with the pressurized structure. Use a spatula or brush and spread sealant on the entire surface approximately 1/32 inch in thickness. Attach the fairlead to the pressurized structure, sealant, sealant should extrude around the mounting flange (see figure 13.1C).

c. Wrap the fairlead with at least three turns of masking tape as shown in figure 13.1D. Puncture the masking tape over the injection hole in the fairlead assembly and inject sealant with a sealing gun. Apply sealant over each fairlead fastener as shown in figure 13.1E.

d. Complete all of the aforementioned steps during the application time of the sealant. Allow sealant to cure, remove masking tape and excess sealant which extruded from the fairlead mounting flange.

e. Figures 13.2 and 13.3 illustrate a different type fairlead and wire bundle connector. The procedure for sealant application is the same as previously described.

f. Figure 13.4 illustrates various coaxial connectors frequently used for installation through structure. Fairleads are not recommended for installation of coaxial cable. Sealant application is the same as previously described.

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