7.13 Control Fittings Flashcards
What is the traditional method of moving aircraft flight control surfaces?
The traditional method is by using flexible control cables terminated at their ends by swaging of a terminal or end fitting.
What is swaging?
Swaging is a process that creates a permanent connection between a control cable and an end fitting by applying pressure.
What technology do modern aircraft use for flight control?
Modern aircraft use digital flight control technology, commonly known as fly by wire.
What was the preferred method before swaged fittings?
The hand-woven splice was the preferred method used on older aircraft.
What are the two most common materials used in aircraft control cables?
The two most common materials are carbon steel and stainless steel.
Why is stainless steel preferred in harsh environments?
Stainless steel has a longer service life in harsh environments, making it better where corrosion can be an issue.
What standards are swage type compression end fittings manufactured in accordance with?
They are manufactured in accordance with AN standards.
What is essential for a correctly swaged terminal?
A correctly swaged terminal ensures that the cable maintains its full rated strength.
What tools can be used for swaging compression end fittings?
Tools include Kearney® swager, hydraulic/pneumatic press, and Nicopress® hand splicing tool.
What is the swaging process using the Kearney® Swager?
The process involves cold roll forging where the terminal is squeezed onto the cable.
What must be done if the cable has a plastic coating before swaging?
The plastic coating must be removed over the length before it can be engaged with the terminal.
What must be checked before starting the swaging operation?
Check that the cable and terminal are of the correct size using a micrometer and GO/NO-GO gauge.
What is the purpose of marking the cable and shank during swaging preparation?
Marking ensures proper alignment and engagement of the cable and terminal during swaging.
What is the maximum number of passes allowed during swaging?
Never use more than four passes during swaging.
What is the purpose of the Nicopress® process?
The Nicopress® process uses a copper sleeve that is mechanically compressed into a cable to form a strong bond.
What is a safety feature for inspecting Nicopress® sleeves?
Applying a band of paint to the cable and sleeve helps indicate if the cable has slipped.
What is required for running splices using Nicopress® sleeves?
Running splices can be made using two Nicopress® sleeves, ensuring full cable strength.
What are the common types of deterioration in aircraft cable systems?
Wire or strand breakage is easy to recognize visually, while wear, corrosion, and distortion are not easily seen.
How often should control cables be inspected?
An annual or 100-hour inspection is recommended to check for broken wire strands.
What must be done if a cable assembly has one broken wire strand in a critical fatigue area?
The cable assembly must be replaced.
What are critical fatigue areas in aircraft cables?
- The working length of a cable over, under, or around a pulley, sleeve, or fair-lead.
- Any section where the cable is flexed, rubbed, or worked.
- Any point within 12 inches (30.5 cm) of a swaged end fitting.
What are possible swaged on fittings for cables?
Eye, Fork, Ball, Ball and shank, Ball and double shank, Threaded stud, Threaded stud and turnbuckle, Compression sleeve.
How can broken wires in critical fatigue areas be detected?
By passing a cloth over the area to snag on broken wires, which also cleans the cable for visual inspection.
What can kinking of a wire cable lead to?
Kinking can create unequal tension and excessive wear, necessitating cable replacement.
What should be done if a cable has 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 the individual wires in each strand appear to blend together, usually when outer wires are worn out by 40-50%.
What is necessary for proper pulley inspection?
Pulleys must be carefully aligned, free to rotate, and inspected for roughness, sharp edges, and foreign material.
What is the purpose of pressure seals in aircraft cables?
To allow the cable to pass freely while preventing pressurisation-air leakage.
Why is correct cable tension important in aircraft flight control systems?
Loose cables cannot transfer control inputs and can endanger the aircraft and occupants.
How is cable tension adjusted?
By adjusting a turnbuckle, which can be locked using wirelocking, lock nuts, or special locking clips.
What tool is used to determine cable tension?
A tensiometer.
What is the accuracy of a properly maintained tensiometer?
98%.
What should be done when tensioning cables?
Only the turnbuckle should be rotated while keeping each cable end stationary.
What is the significance of ambient temperature when adjusting cable tension?
Temperature variations can create large differences in tension due to the different materials of the aircraft and cables.
What should be used to ensure satisfactory results during tension measuring?
Rigging pins and gust locks.
What is a Bowden cable?
A Bowden cable is a type of flexible control cable used to transmit mechanical force or energy by the movement of an inner cable running inside a conduit.
Where is the Bowden cable system commonly used?
The Bowden cable system is sometimes used to operate remote control systems on aircraft.
What is an aircraft remote control system?
An aircraft remote control system is a system where the controls are located in one area of the aircraft, and the item to be controlled is somewhere else.
What are examples of remote control systems on an aircraft?
Examples include aircraft engine controls, throttle or power controls, propeller pitch controls, and 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 placed around the cable, covered by cotton braiding.
How are Bowden cables protected from moisture and contaminants?
Bowden cables are housed in a conduit to keep out moisture and contaminants.
How does the Bowden cable control system operate?
The Bowden cable control system operates in one direction (pull) like a normal cable, requiring a means to return the control.
What methods are used to return the control in a Bowden cable system?
Control can be returned using either two cables that give control in both directions or a cable and a return spring.
What devices can be used to adjust Bowden cables?
An adjustable stop or a double-ended stop can be used to adjust Bowden cables.
What is an adjustable stop?
An adjustable stop consists of a tee-barrel, locknut, and hollow-threaded portion fixed on the conduit at the receiving end of the cable.
What is a double-ended stop?
A double-ended stop is used when access to the ends of the cable is restricted, allowing adjustment at an accessible portion of the cable.
How can Bowden control cables be connected to other control cables?
Bowden control cables can be connected using a cable connector, a cable connecting barrel for one-to-one joining, or a junction box for connecting to multiple cables.
What types of hand levers are used with Bowden cables?
Common types of hand levers include thumb type, ratchet type, and plain type.
What is the throw distance for ratchet and plain type hand levers?
Both ratchet type and plain type have a 90 mm (3.54 in) throw in radial motion.
How does the thumb type hand lever differ from the others?
The thumb type has a shorter lever, giving a throw of only 35 mm (1.378 in).
What is important for the inspection of Bowden cables?
The center line of the cable within the conduit must be in a straight line through the mid position of the rise and fall of the lever’s arc of travel.
What should be checked during the inspection of a Bowden cable?
Inspect for corrosion, deformation, bends, kinks, chafing, tension, cleanliness, broken or exposed wires, and other forms of damage.
How can exposed or broken wires on a cable be checked?
One person moves the cable through its length of travel while another gently holds a cotton cloth around the wire, looking for snags.
What is a Teleflex cable system?
A Teleflex cable system is similar to the Bowden cable system, where the operating cable is within a conduit, allowing it to transmit push and pull forces without a return spring.
A typical use of a Teleflex system might be a throttle lever to an engine fuel control system.
How does the construction of a Teleflex cable compare to a Bowden cable?
Teleflex cables are stronger in construction than Bowden cables and usually have the cable attached to a rod or shaft inside the outer sheath for added strength.
What maintenance is required for a Teleflex cable system?
Inner cables should be regularly removed, cleaned, and lubricated with low temperature grease to prevent seizing due to foreign objects, dirt, or freezing.
What should be done before installing the inner cable in a Teleflex system?
The inside of the conduits must be thoroughly cleaned prior to the inner cable being installed.
What should be inspected on the outer conduit of a Teleflex cable system?
Inspect the outer conduit for signs of damage or kinking that can cause the control to become tight or jumpy.
How should the cable be attached in a box type end unit?
Tuck the cable into the slot in the pinion and ensure that the cable helix engages with the pinion teeth to give a wrap of at least 40 degrees.
What is the cable wrap requirement for double entry units?
On double entry units, the cable should engage with the pinion to give a wrap of 180 degrees, projecting through the lead out hole throughout the travel of the control.
What is the adjustment process for sliding end fittings?
Unscrew the threaded hexagon plug, screw the lock nut back, pass the cable through the plug, and screw the lock spring onto the end of the cable so that 3/16 in (4.75 mm) projects.
What is the maximum distance from the face of the body to the end of the sliding tube?
The distance must not exceed 0.45 in / 11.43 mm (0.35 in / 8.89 mm for the old type, without tab washer) to ensure the lock spring is tightly compressed.
What is the correct assembly rule for the end fitting?
The body of the end fitting must not be screwed onto the hexagon plug; the plug must be screwed into the fork, not the fork into the plug.
How often should control cables be inspected?
Control cables (Teleflex & Bowden) should be inspected annually or every 100 hours, depending on the operator.
What should be checked during cable inspections?
Inspect all engine control and flight control cables for correct tension, routing, security, and signs of damage from chafing or heat distress.
What is a common area for control cable damage?
The most common area for control cable damage is at bends, where the cable may rub against the housing.
What issue can Bowden cables face due to moisture?
Bowden cables are prone to water ingression from moisture or condensation, which could cause freezing or corrosion.
How can broken wires in a control cable be detected?
Pass a cloth along the entire length of the cable; any broken wires will snag the cloth.
What should be done if a cable shows signs of broken wires or corrosion?
The cable must be removed, replaced, and tensioned according to the recommended Aircraft Maintenance Manual.
