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Fairleads Fairleads maybe made of a solid piece of material to completely encircle cables when they pass through holes in bulkheads or other metal parts. Fairleads may be used to reduce cable whipping and vibration in long runs of cable. Split fairleads are made for easy installation around single cables to protect them from rubbing on the edges of holes.Grommets Grommets are made of rubber, and they are used on small openings where single cables pass through the walls of unpressurized compartments.Pressure Seals Pressure seals are used on cables or rods that must move through pressurized bulkheads. They fit tightly enough to prevent air pressure loss, but not so tightly as to hinder movement of the unit.Pulleys Pulleys (or sheaves) are grooved wheels used to change cable direction and to allow the cable to move with a minimum of friction. Most pulleys used on aircraft are made from layers of cloth impregnated with phenolic resin and fused together under high temperatures and pressures. Aircraft pulleys are extremely strong and durable, and cause minimum wear on the cable passing over them. Pulleys are provided with grease-sealed bearings, and usually do not require further lubrication. However, pulley bearings may be pressed out, cleaned, and relubricated with special equipment. This is usually done only by depot-level maintenance activities. Pulley brackets made of sheet or cast aluminum are required with each pulley installed in the aircraft. See figure 2-38. Besides holding the pulley in the correct position and at the correct angle, the brackets prevent the cable from slipping out of the groove on the pulley wheel. |
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