7.13 Control Cables Flashcards
What does the term ‘swaging’ mean?
A process that creates a permanent connection between a control cable and an end fitting by applying pressure.
What are the methods of swaging?
- Kearney® hand swager
- Hydraulic press
- Nicopress® swaged sleeve
Why is swaging needed?
To allow for attachment and adjustment of control runs so that the controls can be correctly rigged.
What is the preferred method used on older aircraft before swaging?
Hand-woven splice.
What is the approximate strength provided by a hand-woven splice?
Approximately 75% of the cable strength.
What are the two most common materials used in the construction of aircraft control cables?
- Carbon steel
- Stainless steel
Which material has a longer service life in harsh environments?
Stainless steel.
What standards are swage type compression end fittings manufactured in accordance with?
AN standards.
What is essential to ensure when using swaging tools?
All manufacturer’s instructions, including ‘GO and NO-GO’ dimensions, must be followed.
What type of pressure does the Kearney® swager apply during the swaging process?
Squeezing pressure.
What must be removed from a plastic-coated cable before swaging?
The plastic coating over the length.
What is the maximum cable diameter that can have a terminal swaged to it using standard size cables?
Up to 3/8 in diameter.
What is the first step in setting up the Kearney® swaging tool?
Select the matched pair of roll dies suited for the size cable.
What should be checked to ensure a proper fit before swaging?
The cable diameter and the outside diameter of the terminal shank.
Fill in the blank: The cable must be a close fit in the bore of the terminal before _______.
swaging.
What should be done to the cable end before swaging?
Cut cleanly and squarely, with no wire strands protruding.
What happens after the first pass of the swaging process?
A longitudinal fin or flash on two diametrically opposite sides will be noticeable.
How many passes should be made during the swaging process?
No more than four passes.
What is the purpose of rotating the terminal during the swaging process?
To eliminate the longitudinal fin and ensure a uniform diameter.
True or False: Over-swaging can lead to embrittlement and terminal cracking.
True.
What is the main advantage of hydraulic/pneumatic press swaging?
It is a quicker means of swaging an end fitting to a cable.
What is the Nicopress® process?
A patented process using a copper sleeve mechanically compressed into a cable.
What is imperative when using the Nicopress® process for cable splicing?
Use the right tools and follow the supplied instructions.
What is a safety feature applied during inspection of Nicopress® sleeves?
Apply a band of paint to the cable and sleeve.
What indicates that the cable has slipped during inspection?
The paint band breaks.
What are the methods used to inspect and test control cables?
Visual inspection, cloth snagging method, and using a magnifying glass
Cloth snagging helps detect broken wires and cleans the cable for better visibility.
What is the recommended frequency for inspecting control cables?
Annually or every 100 hours of operation
What must be done if a cable assembly has one broken wire strand in a critical fatigue area?
It must be replaced
Define critical fatigue areas in control cables.
- Working length over pulleys or through fair-leads
- Sections where the cable is flexed or rubbed
- Points within 12 inches of a swaged end fitting
What types of swaged fittings are found in control cables?
- Eye
- Fork
- Ball
- Ball and shank
- Ball and double shank
- Threaded stud
- Threaded stud and turnbuckle
- Compression sleeve
How can kinking of a wire cable be avoided?
Proper handling and installation
What is the effect of kinking on cables?
Creates unequal tension and excessive wear, necessitating replacement
What should be done if a cable shows a popped core or loose strands?
Replace the cable regardless of wear or broken wires
When should flexible and non-flexible cables be replaced?
When individual wires appear to blend together, usually after 40-50% wear
What are common signs of cable wear and damage?
- Blending of wires
- Distortion
- Corrosion
What must be ensured during pulley inspection?
- Proper alignment
- Free rotation
- Absence of rough edges and foreign material
What is the purpose of fairleads in control cable systems?
To prevent contact with the structure while allowing cable movement
What is the importance of cable tension in aircraft flight control systems?
Correct tension allows for proper control input transfer and prevents locking
What can happen if cable tension is excessive?
It can damage pulleys and support structures
How is cable tension adjusted in aircraft?
Using a turnbuckle
What materials are used for pressure seals in control cable systems?
Soft plastic or fiber such as Nylon® or Tufnell®
What tools are available for turnbuckle tensioning?
Various cable turnbuckle tools and rigging kits
What is the accuracy of a properly maintained tensiometer?
98%
What is the primary function of a tensiometer?
To measure the force needed to offset the cable
What cable diameters are commonly used for control cables?
- 3/32 in
- 1/8 in
- 5/32 in
- 3/16 in
What should be done to ensure accurate tension values in varying temperatures?
Use average readings and compensate for extreme temperature variations
Fill in the blank: The cable is only allowed to be preloaded when it is not _______.
bent
True or False: Fairleads can be used to change the direction of a cable.
False
What is a Bowden cable?
A type of flexible control cable used to transmit mechanical force or energy by the movement of an inner cable running inside a conduit.
What are common applications of Bowden cables in aircraft?
Examples include:
* Aircraft engine controls
* Throttle or power controls
* Propeller pitch controls
* Landing gear emergency extensions
What materials are Bowden control cables typically made from?
Bowden control cables are normally constructed from stainless steel, with a coiled wire covered by cotton braiding.
How do Bowden cables operate?
The Bowden cable control system operates in one direction (pull) and requires a method to return the control, typically through:
* Two cables for bi-directional control
* A cable and a return spring
What is the purpose of an adjustable stop in Bowden cable systems?
To prevent the cable from becoming slack over time.
What is the difference between an adjustable stop and a double-ended stop?
An adjustable stop is a standard stop with a tee-barrel and locknut, while a double-ended stop is used when access to cable ends is limited and features an internally threaded tube.
What types of hand levers are commonly used with Bowden cables?
The common types are:
* Thumb type
* Ratchet type
* Plain type
What is the throw distance for ratchet and plain type hand levers?
Both have a 90 mm (3.54 in) throw in radial motion.
What is the throw distance for thumb type hand levers?
The throw distance is 35 mm (1.378 in).
Describe the inspection process for Bowden cables.
Check for:
* Axial alignment
* Corrosion
* Deformation, bends, and kinks
* Chafing
* Tension
* Cleanliness
* Broken or exposed wires
* Other forms of damage
What should be done if corrosion is detected on a Bowden cable?
Remove and replace the cable.
How can one check for exposed or broken wires on a Bowden cable?
One person moves the cable through its length while another holds a cotton cloth around the wire, looking for snags.
What is a cable connector used for?
To connect a Bowden control cable to other types of control cables.
Fill in the blank: Bowden cables are designed to operate _______ loaded components or systems.
lightly
True or False: Bowden cables can operate in both directions without additional components.
False
What is the recommended action for Bowden cables regarding maintenance?
Regular inspection and lubrication according to the service manual.
What is a Teleflex cable system similar to?
Bowden cable system
What is a typical use of a Teleflex system?
Throttle lever to an engine fuel control system
How does a Teleflex cable system transmit force?
Transmits a push force as well as a pull force
What construction feature makes Teleflex cables stronger than Bowden cables?
Cable attached to a rod or shaft inside the outer sheath
What can cause a Teleflex cable to seize?
Foreign objects, dirt, or freezing
What maintenance action is important for the inner cables of a Teleflex system?
Regularly removed, cleaned, and lubricated with low temperature grease
What should be checked during inspections of the outer conduit?
Signs of damage or kinking
How should the cable engage with the pinion in a box type end unit?
Wrap of at least 40 degrees
What is the required wrap of the cable for double entry units?
180 degrees
What is the maximum distance from the face of the body to the end of the sliding tube for end fitting adjustment?
0.45 in / 11.43 mm
True or False: The body of the end fitting must be screwed onto the hexagon plug.
False
How often should control cables be inspected?
Annually or every 100 hours
What should be inspected on control cables during inspections?
Correct tension, routing, security, and signs of damage
What is the most common area for control cable damage?
At bends
What can cause Bowden cables to freeze or corrode?
Water ingression from moisture or condensation
What is the most common method to examine a control cable for broken wires?
Pass a cloth along the entire length of the cable
What should be done if broken wires or signs of corrosion are found in a cable?
Removed, replaced, and tensioned in accordance with the recommended Aircraft Maintenance Manual
