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Control Cable Basics
Control cables play a big part in your aircraft. It is an item that should not be taken for granted and for that reason should be inspected properly. Periodical inspections of the control cables are important. The inspection should not only consist of checking the cable ends and making sure that the bell cranks hit their stops. The proper way to inspect a cable is to inspect it inch by inch.
Control cables are generally fabricated of carbon steel or corrosion resistant steel wire and may consist of either flexible or nonflexible type construction. Control cables are made up of many wires twisted together to form a strand and many strands are then twisted together to form a cable.
Aircraft cable systems are subject to a variety of environmental conditions and forms of deterioration that easily recognised such as wire/strand breakage, or the not so readily visible type of wear such as corrosion. critical areas for wire breakage are those sections of the cable which pass through fairleads and around pulleys.
Examine cables for broken wires by passing a cloth along the length of the cable. This will clean the cable for a visual inspection and will detect broken wire if the cloth snags.
When snags do occur, closely examine the cable to determine the full extent of the damage. Even if no snags occur, it is not positive evidence that broken wires dont detect any snags with your cloth, remove and bend the cable, making sure no kinks get into the wire so that it can be reinstalled if the cable is found to be in good condition.
Cable Wear
Cable wear from pulleys or fairleads will normally extend along the cable equal to the distance that the cable moves at that location. This may occur either on one side or the entire circumference. Cables should be replaced when signs of wear are visible.
As wear is taking place on the exterior surface of a cable, the same thing is happening internally, particularly in the section of the cable that passes over the pulley or quadrant. This wear is caused by relative motion between the inner wire surfaces.
Another type of cable wear is due to corrosion. Be suspicious of broken wires in areas of non contact. During inspection, take particular attention in areas where cables pass through areas of moisture such as in wheelwells, battery compartments and any other areas where moisture or chemicals come into contact with cables.
Cable Inspection
When doing an inspection, check the following:
· cable runs for incorrect routing or areas where cables make contact with other objects. Have someone move the controls so you can see if contact is being made in any extreme or travel.
· cable end fittings such as swaged terminals for distortion or broken strands. Ensure that all bearing and swivel fittings pivot freely to prevent binding and subsequent failure.
· turnbuckles for proper thread exposure and broken or missing safety wire or clips.
· pulleys for wear, making sure they all move freely and that safety pins are installed over them to prevent cables from popping off.
· loose bolts and missing cotter pins.
· cable travel is sufficient to hit stops.
· cable tension, too loose or too tight. This could cause sloppy or stiff control movement.
After inspecting the cable system, sit in the cockpit and make sure all controls move freely and in the proper direction. This will assure you did not disturb anything during your inspection.