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| Summary Some areas of airframe structures are sealed to prevent fuel fumes from entering the aircraft's interior. Pilot and crew compartments are tightly sealed to permit controlled ventilation. The three kinds of sealers in general use are rubber, sealing compound, and special seals. Rubber seals are used when the seal is frequently broken for repairs. Rubber seals are not repairable, and they must be replaced anytime the seal is damaged. Sealing compounds are used where the seal is seldom broken except for structural maintenance or part replacement. Special seals are used to pass cables, tubing, mechanical linkages, and wires into and out of sealed areas. Cannon plugs, couplings, and similar fittings are sealed to the bulkheads. All seals of moving components are subject to wear and must be inspected regularly. Surfaces to be sealed must be clean, and only approved strippers and cleaners can be used. Cleaning techniques include using a vacuum cleaner to pick up loose dirt, a stripper to remove the old seal, and an approved solvent to scrub the repair area. Safety practices range from protecting undamaged sealants and acrylic plastics from the stripper to wearing protective clothing and goggles and using explosive-proof lighting. Rubber seals must be applied immediately after a seal frame is cleaned. A clean paint brush can be used to apply an even coat of rubber cement. Rubber cement must be allowed to dry to a sticky consistency before joining the seal to the metal. Sealing compound can be applied directly from a tube or, if it is in bulk form, from a pressure gun. A sealing compound application overlaps each end of the repair area by 3 inches. The compound must be allowed to cure to a tough, rubbery consistency before joining the surfaces to be sealed. High temperatures, not more than 120° F, speed curing. Infrared lamps can be used if adequate ventilation is available to dispel the solvent fumes.
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| Curriculum design: David L. Heiserman Publisher: SweetHaven Publishing Services |
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