Supplied B1 Module 07A textbook: PDF pages 263–274.
Cable construction and flexibility
Aircraft control cables use groups of wires formed into strands and laid into a cable. Construction influences flexibility, strength and permitted pulley use. Match cable material, diameter and construction to the installation. More flexible constructions can negotiate smaller bending arrangements within the prescribed limits, but no cable is immune to fatigue. Cable identification and approved end fittings matter as much as visible diameter. A replacement must also satisfy route, travel and tension requirements.
What does cable construction influence? Flexibility and mechanical behaviour.
Swaged terminal fittings
Swaging compresses a terminal onto a correctly prepared cable using specified tooling. Verify cable insertion, fitting size, dies and completed dimensions. Inspect for cracks and use go/no-go gauges or dimensional checks as specified. Proof testing may be required; a casual pull by hand is not equivalent. Keep the process and test records when required. Do not heat, hammer or reshape a rejected swage as an informal repair. Strength depends on a qualified combination of cable, fitting and process.
What is swaging intended to create? A controlled mechanical grip of a terminal on the cable.
Cable inspection
Inspect for broken wires, corrosion, wear, kinks, birdcaging and heat damage. Pay particular attention to pulley contact zones, fairleads and terminal exits. Flex the cable only as the inspection procedure permits to reveal hidden breaks. Avoid running bare fingers along a cable; broken strands can injure the skin. The allowed number and location of broken wires depend on the approved limits, not a universal rule. Internal corrosion can exist even where the external surface appears satisfactory.
Where is detailed control-cable inspection especially important? At pulley zones, fairleads and terminal exits.
Tension and temperature
Use a suitable calibrated tensiometer with the correct cable-size riser or setting. Read the instrument and apply its conversion chart if required. Cable tension changes with aircraft temperature and structure expansion, so compare the reading with the specified temperature-tension chart. Excess tension overloads bearings and structure; low tension increases lost motion and may allow cable derailment. Check relevant paired circuits and control position. A tension reading is valid only with the required rigging condition and measurement technique.
Why is a temperature-tension chart used? Cable and structure dimensional changes alter tension.
Turnbuckles, pulleys and rigging
Turnbuckles adjust effective length and must have the prescribed thread engagement and locking. Avoid twisting the cable during adjustment. Inspect pulley grooves, bearings, guards and cable alignment. Fairleads guide a cable but do not necessarily permit large changes of direction. Set neutral positions, travel and stops using the rigging procedure, then check both directions and required clearances. Safety wire or locking clips prevent unintended rotation; their installation must not conceal inadequate engagement or incorrect rigging.
What must be verified before locking a turnbuckle? Thread engagement, adjustment and cable condition.
Bowden and flexible controls
A Bowden control uses an inner member moving inside an outer casing. Depending on design it may transmit pull only or push and pull. The casing must be securely anchored so inner movement produces the intended output rather than moving the sheath. Inspect bend radius, friction, corrosion and end attachment. Excessive bends or damaged lining can create stiffness and delayed response. Lubricate only where specified and verify full travel. A flexible control's apparent movement at the input does not prove the output reaches its stop.
Why must a Bowden cable's outer casing be secured? It provides the reaction path for inner-cable movement.
Apply the knowledge
Work through these examples before starting the quiz. Explain why the other choices would not meet the requirement.
A cable tension reading is correct at one temperature. What must be considered before acceptance?
The specified chart and actual aircraft temperature — Tension limits are evaluated under the defined temperature and rigging conditions.
A turnbuckle is locked but has insufficient engagement. What is correct?
Rectify engagement and rigging before acceptance — Locking prevents rotation; it does not establish adequate thread engagement.
A Bowden input moves but the casing moves at its bracket. What is the likely effect?
Lost effective output travel — The casing must react the input motion through secure supports.
A cable has a kink but no visible broken wires. What is appropriate?
Assess the kink under the cable rejection limits — A kink is a separate damage mechanism that can compromise strength.