Control Cables – Maintenance and Inspection

Cable identification is done by the part number followed by a proof loading inspectors stamp which may be rolled or etched on either of the end fittings. Alternatively a tag or label may identify some aircraft cables. On this type of identification system it could be dangerous or impracticable to leave the tag or label dangling for whatever reason the certifying engineer deems appropriate, this could be down to a risk of the tag/label jamming or fouling a control run or chafing structure as this could aid corrosion and impair flight safety, the tag/label could be removed and the details on the tag/label could be entered into the aircraft log book or maintenance record in accordance with the authorities legislation.

Cables 45cwt or over can be subjected to operational loads, which may tend to straighten the strands within the wire to the extent that the nuts may loosen or lockwire may break. In these situations the Turnbuckles may be locked with the use of an approved tube pre-drilled and bolted through the turnbuckle.

When a cable is assembled at the factory it is assembled with a lubricant within the cable to give internal lubrication and life enhancing properties. In an aircraft cables life it will have many protective treatments to prolong its life and performance. From time to time these treatments need to be repeated which involves cleaning off the old treatment. When doing so it is recommended that you use a clean rag or the airframe manufacturers cleaner. If this information is not available then only use a dry rag,

DO NOT UNDER ANY CICUMSTANCES IMPROVISE AS THIS MAY WASH OUT THE CABLES INTERNAL LUBRICANT AND DECREASE CABLE PERFORMANCE AND LIFE.

Cable servicing data can be found in chapter 12 in the maintenance manual or in the aircraft service manual.

It is always important that a cable is never overgreased as this can attract dust, dirt and grit which damages cables, fairleads and pulleys. This can lead to costly maintenance later. Grease can normally collect around fairleads, pulleys and controls so try to keep an eye on these areas and wipe away excess as soon as possible.

It is a good indication that a cable is worn out when its strands or wires start to spray out of the cable. This is normally detected when greasing but is not restricted to it. Cables will normally wear out around pulleys and fairleads first but BE A PROFFESIONAL CHECK THE WHOLE CABLE OR ZONE ON THE WORK CARD , IT IS WHAT YOU ARE REQUIRED TO DO. PEOPLES LIVES DEPEND ON YOU BEING A PROFESSIONAL, DO NOT DISSAPOINT THEM.

When checking cable tension always use the correct tensiometer in the correct units with the correct riser and always make sure the serial number on the calibration chart tallies with the serial number on the tensiometer. The servicing manual (MM chapter 12) specifies the correct cable tension for the ambient temperature of the day (use a calibrated thermometer to measure the temperature and remember to hold it or locate it as far away from your body as possible as body heat can effect the reading of the thermometer). The manual will normally specify a position to locate the tensiometer but were this is not specified locate it as far away from fairleads or pulleys as possible. when adjusting cable tension try to adjust it as evenly as possible throughout the turnbuckles in the system.

After adjusting turnbucles do not forget to lock them again. Before you do lock them, check that they are in safety, either by ensuring that you can not push a pin through the inspection hole or by making sure that there are no more than three threads showing, Always check the maintenance manual for methods and Tolerances. There are two main methods of locking turnbuckles, Spring clip type and wire lock type.When wire locking always make the slope of the wire tighten the turnbuckle and always use the correct gauge of wire. When using the spring clip type it is imperative that it is locked down properly, This is normally when it has clicked down and is tight against the body of the turnbuckle, Please note that you MUST always check the maintenance manual when securing turnbuckles and always use the specified methods in the manual.

Note: When locking turnbuckles with spring locking clips there is no inspection                   hole and are inspected to be in safety when no more than three threads show.

 

 

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