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9/8/98 AC 43.13-1B 11-189. BONDING JUMPER INSTAL- LATIONS. Bonding jumpers should be made as short as practicable, and installed in such a manner that the resistance of each connection does not exceed .003 ohm. The jumper should not interfere with the operation of movable aircraft elements, such as surface controls, nor should normal movement of these elements re sult in damage to the bonding jumper. a. Bonding Connections. To ensure a low-resistance connection, nonconducting fin ishes, such as paint and anodizing films, should be removed from the attachment sur face to be contacted by the bonding terminal. On aluminum surfaces, a suitable conductive chemical surface treatment, such as Alodine, should be applied to the surfaces within 24 hours of the removal of the original finish. Refer to SAE, ARP 1870 for detailed instruc tions. Electric wiring should not be grounded directly to magnesium parts. b. Corrosion Protection. One of the more frequent causes of failures in electrical system bonding and grounding is corrosion. Aircraft operating near salt water are particu larly vulnerable to this failure mode. Because bonding and grounding connections may in volve a variety of materials and finishes, it is important to protect completely against dis similar metal corrosion. The areas around completed connections should be post-finished in accordance with the original finish require ments or with some other suitable protective finish within 24 hours of the cleaning process. In applications exposed to salt spray environ ment, a suitable noncorrosive sealant, such as one conforming to MIL-S-8802, should be used to seal dissimilar metals for protection from exposure to the atmosphere. c. Corrosion Prevention. Electrolytic action may rapidly corrode a bonding connec tion if suitable precautions are not taken. Aluminum alloy jumpers are recommended for most cases; however, copper jumpers should be used to bond together parts made of stain less steel, cadmium plated steel, copper, brass, or bronze. Where contact between dissimilar metals cannot be avoided, the choice of jumper and hardware should be such that corrosion is minimized, and the part likely to corrode would be the jumper or associated hardware. Tables 11-14 through 11-16 and figures 11-20 through 11-22 show the proper hardware com binations for making a bond connection. At locations where finishes are removed, a pro tective finish should be applied to the com pleted connection to prevent subsequent corrosion. d. Bonding Jumper Attachment. The use of solder to attach bonding jumpers should be avoided. Tubular members should be bonded by means of clamps to which the jumper is attached. Proper choice of clamp material should minimize the probability of corrosion. e. Ground Return Connection. When bonding jumpers carry substantial ground re turn current, the current rating of the jumper should be determined to be adequate and that a negligible voltage drop is produced. 11-190. CREEPAGE DISTANCE. Care should be used in the selection of electrical components to ensure that electrical clearance and creepage distance along surfaces between adjacent terminals, at different potentials, and between these terminals and adjacent ground surfaces are adequate for the voltages in volved. Par 11-189 Page 11-75PDF Image | AFS-640
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