Aircraft Cables
Introduction
The content of this article is everything you need to know about aircraft cables and their use.
You will learn:
- What is Aircraft Cable?
- How Aircraft Cables are Made
- Types of Aircraft Cables
- Uses for Aircraft Cables
- And much more …
Chapter 1: What is Aircraft Cable?
An aircraft cable is a style of highly durable cable that is used for aircraft flight controls and other applications and is differentiated from normal cables by its diameter, stranding, and wires, which provide its strength and flexibility. The term “aircraft cable” is a descriptor used to indicate a specific type of cable with diameters that are less than 0.375 and 7 by 7 or 7 by 19 construction made of galvanized or stainless steels. The most important aspect of aircraft cable is its tensile strength, which ranges between 120 lbs up to 14,400 lbs (54 kg up to 6532 kg).
Regardless of the type of aircraft cable, all forms are manufactured using the same principles as those that are used to manufacture other forms of cable or wire rope, which is arranging individual wires in a uniform helical order to form the wire’s strands. When more strands and wires are added per strand, the more flexible aircraft cable becomes. Additionally, as the diameter of the cable increases, the diameters of the wires increase, and the breaking strength of the cable increases.
Chapter 2: How Aircraft Cables are Made
Aircraft cables are used in industry, shipping, commercial enterprises, and homes. Their tensile strength is built upon their individual wires and strands. Galvanized high carbon wire A1S1 C1050 and C1070 and A1S1 stainless steel series 302 and 304 are the most used metals for producing aircraft cable strands.
What differentiates aircraft cables from other forms of cables is their number of strands and the number of wires per strand. Generally, aircraft cable has a diameter of 0.03125 in up to 0.375 in (0.79 mm up to 9.5 mm) with a 7 by 7 or 7 by 19 construction and a wire core that is the same as the outer strands. Aircraft cables consist of wire that is twisted into strands around a core with the basic unit being highly durable wire. Each strand has individual wires wrapped around a central wire.
The created strands are placed helically around a core or center. The classification for aircraft cable includes two numbers with the first number being the number of strands while the second number is the number of wires per strand. Typical aircraft cable has a classification of 7x19, which is 7 strands with 19 wires per strand.
The other form of aircraft cable is classified as 7x7 cable with seven strands wrapped around a seven wire core with each strand having seven wires. The different wire count for 7x7 cable gives the cable different properties. Although the wire counts between the two cables are different, both types of cable are flexible since higher wire counts make it possible for cables to bend easier for use in cable systems. The higher wire count of classification 7x19 makes it ideal for applications that have frequent use while the rigidity of classification 7x7 makes it the best choice for aircraft cabling.
Winding
The first step in the construction of aircraft cable is winding the galvanized or stainless steel wires into strands. For aircraft cables, 6 or 18 wires are wound in a helical pattern around a single wire to form a strand. The helical pitch of the winding determines how flexible the strand will be as well as its axial stiffness. The lay of aircraft cable can be either left or right, which is the stranding direction.
The helix or spiral winding of the wires to create the strands is referred to as the lay. Classifications 7x7 and 7x19 aircraft cables are traditionally wound with a right hand lay. When their wires are wound in a clockwise direction, it is a right lay while a winding in a counter clockwise direction is a left lay. The lay length is used as a unit of measure and refers to the linear distance a wire extends when making a complete turn.
Core
The core of aircraft cable is its foundation and consists of a single strand with the same construction as that of the outer strands. It supports the compressive force of the load on the cable and runs through the center of the cable. The core supports the outer strands and helps maintain their position when the cable is being bent or under the tension of a load.
The flexibility, strength, and elasticity of an aircraft cable depends on the core and outer strands working together for enduring the stress of a load and repeated bending. Although there are many different types of cores that include rods and fabrics, the cores of aircraft cable are always made of a strand that is the same as the outer strands to ensure the durability and strength of the cable.
Constructing Aircraft Cable
The construction of an aircraft cable follows the same steps as the ones that were used to construct the strands with right or left lays. As with the winding of the wire for the strands, the lay of the strands for an aircraft cable is important in regard to the strength of the cable.
During the manufacture of the strands, each strand is preformed to the spiral or helical shape it will take to fit its position on the final cable, a process referred to as preforming. The use of preforming ensures the flexibility of the finished cable and helps in relieving of stress as the strands are woven into the final cable. As the strands are wound, they are lubricated to reduce friction and provide corrosion resistance.
The two types of aircraft cable lubricants are penetrating and coating. Penetrating lubricants have a petroleum solvent that takes the lubricant to the core of the cable where it evaporates after lubricating each strand leaving a film of lubrication. Coating lubricants act as a coating and seal the outside strands to protect the cable from moisture, wear, and corrosion. In most cases, both lubricants are used with aircraft cables to ensure that the core is lubricated and saturated.
The final step in the manufacturing process for aircraft cable is to roll it onto a spool for shipment. In some manufacturing processes, assemblies or terminations may be added to the end of the cable in preparation for the cable's final use. Since there is such a wide range of uses and assemblies, most cable manufacturers do not add assemblies unless the cable is custom made.
Chapter 3: Aircraft Cable Assemblies and Terminals
The strength and durability of aircraft cables makes them ideal for a wide variety of applications. A key factor in their use is how they are connected to the process for which they are designed. Since the many uses for aircraft cables are varied and unique, the types of terminals and assemblies take different forms, shapes, and sizes.
The two basic types of terminations are a loop or eye and a fitting. Loops are formed using a splice with a swaged sleeve, hand tucked splice, or wire cable clips. Fittings are placed on a cable using swaging, pouring molten zinc or resin to bond the fitting, or by using a wedge. The types of terminations or assemblies for aircraft cables come in a wide variety of shapes, sizes, and materials and include button stops, thimbles, shank balls, spelter sockets, and turnbuckles.
Loop Sleeves
Loop sleeves or cable crimp sleeves are the most common tool used to form a cable loop. They are specifically designed for use with cable assemblies to form loops of any size or attach separate pieces of aircraft cable. Loop sleeves come in every size imaginable with geometries, sizes, and materials for any type of application. The types of loop sleeves include cylindrical or figure 8 and are applied manually by a hand tool or industrial press. Loop sleeves are made of stainless steel and are swaged or pressed to the cable to form the loop.
Ball and Shank End Fitting
Ball and shank end fittings have a spherical shape and are crimped to the end of an aircraft cable such that they can fit into a socket. They have a hole that goes through the middle of the ball and are made of stainless steel. The shank portion of the fitting is attached to the ball and is crimped to the cable. Ball and shank end fittings are used for applications where a cable termination has strength that is greater than the cable to which it is swaged.
Strap Fork
Strap fork terminations are used in combination with ball and shank end fittings to which they are attached such that the forks can swivel. The design allows the end load to twist without putting undue tension on the cable. The spherical portion of the ball and shank end fitting provides the means for the strap fork to swivel and a shoulder that protects the cable.
Strap Eye
A strap eye termination is similar to a strap fork in that it is secured to a shank ball and not connected directly to the cable, which allows it to rotate without stressing the cable. Unlike strap forks, strap eyes have their forks welded together to make them thinner and capable of fitting into small spaces.
Thimble
Cable thimbles are used in combination with loops and serve as a holder for the cable and the inner lining of the loop. They are used to reinforce the loop or eye with grips, clips or clamps and prevent the loop from fraying caused by friction under the pressure of the load by providing a solid metal barrier. The cable is wrapped around the groove of the thimble. Once securely in place, the loop is crimped near the bottom of the thimble. The wide use of cable loops has necessitated the introduction of thimbles in sizes to fit any size of aircraft cable.
Threaded Terminal
Threaded terminals are designed to increase tension on an aircraft cable using a locking nut, rigging screw, or turnbuckle. They are swaged or pressed onto an aircraft cable and come with left or right hand threads. Threaded terminals are commonly used to tighten aircraft assemblies to achieve a specific tension. Matched with a turnbuckle, a threaded terminal is used to make adjustments to the length of an aircraft cable and adjust its tension.
Turnbuckle
Turnbuckles work with threaded terminals to adjust the length and tension of aircraft cables. They make it possible to connect several lengths of aircraft cable to create a single long cable. Turnbuckles have threads at both ends into which threaded terminals are attached. As the turnbuckle is rotated, it increases the tension of the connected threaded terminals and their cables.
The different turnbuckles are adaptable for a wide variety of uses and come with hooks, eyes, and several types of fittings, which makes them flexible for use in a wide range of applications. Their threading is normally left to make the insertion of right threading smooth and easy.
Eyelet
Eyelets have a round end with a hole in the middle for connecting screws, bolts, or clevis pins. They are a metal loop to be used as an attachment point and are made of aluminum, stainless steel, or carbon steel. Eyelets, as with all forms of aircraft cable terminations, come in a wide variety of sizes. They are produced by stamping and have a sleeve attached to their round O like portion such that they can be swaged to aircraft cable.
Cable Clips
Cable clips have a similar function as that of loop sleeves. They are used to create cable loops and to connect cables. Cable clips include a U-shaped bolt that is threaded on both ends of the U-shape, a saddle, and two bolts. They connect to an aircraft cable by placing the U bolt over all portions of the cable, normally near the dead end, placing the saddle over the bolt ends, and attaching and tightening the screws securely such that the cable cannot shift or twist.
Chapter 4: Uses for Aircraft Cable
Of the various types of cable and wire rope products, thin, strong, and flexible aircraft cable has been found to be the most useful and reliable. Its stranding of thin steel wires gives it the strength and durability that can be used by a wide range of applications. Stainless steel aircraft cable is used for stressful applications due to its ability to withstand harsh and hazardous temperatures due to its resistance to corrosion. Galvanized steel aircraft cable is less expensive but has the strength of stainless steel and is used in milder and less harsh conditions.
Aircraft Cable Lanyards
Aircraft cable lanyards are made of galvanized steel or stainless steel and are widely used for their strength, durability and longevity. They are attached to pins and fasteners to prevent loss and as tethers for components and door restraint cables. Aircraft cables are ideally suited for lanyard applications due their resistance to wear. They are widely used in the military and marine applications. As with all forms of aircraft cables, lanyards can have several types of terminations including hooks, loops, and eyelets.
Aircraft Controls
Aircraft cable is used with aircraft for securing aircraft or securing cargo. The durability of aircraft cable makes it ideal for controlling aircraft parts and connections. Aircraft cable is attached to several parts of an aircraft including the rudder, engine systems, and emergency systems and is used to raise and lower landing gear.
Securing Cargo
The securing of cargo during transport is a major issue for shipping companies that can lose money for damaged goods. Aircraft cables are used to tie down and secure cargo to keep it from shifting. It is ideal for the application due to its size, which makes it easy to handle, install, maintain, and shape.
Maritime Applications
Any type of wire or cable that is used for maritime applications requires special protection from the effects of salt water. In most cases, stainless steel series 316 is the preferred metal for maritime use due to its high resistance to pitting corrosion, which is common for maritime applications. Aircraft cable is used for hoisting, securing boats and docks, rigging for sailboats and fishing boats, and cables for winches and pulleys.
Pulleys and Winches
Pulleys and winches endure a great deal of stress, torque, and tension during use. Since they are designed to lift heavy loads and move the loads for shipping or placement, their cables have to be extremely strong and rigid. The strength of aircraft cable makes it the perfect choice for use with pulleys and winches. It is capable of enduring the constant strain and tension with resilience and strength.
Stage and Movie Rigging
In the entertainment business, the presentation of shows and plays requires the lifting of backdrops, scenery, and curtains that are heavy and cumbersome. For performance and safety reasons, the equipment that is used for lifting and hoisting the many effects have to be secure, strong, rigid, and capable of handling the heavy loads. It is for these reasons that aircraft cable is used by stage managers and stage hands for quick and efficient movement of props and other heavy items that are part of a performance.
Zip Lines
Although they do not fall under the classification of a dramatic performance, zip lines are a form of entertainment that has rapidly grown in the last few years. They are used to carry tourists over caverns, canyons, valleys, and between points on a mountain. For a wide variety of reasons, insurance being one of the most prominent, zip lines have to be exceptionally secure and durable. During tourists’ season, they are constantly in use and are inspected and maintained daily. In most cases, the use of aircraft cable for zip lines is not so much concerned about weight but more concerned about constant use, which can wear out most other types of cable.
Garage Door
A common use of aircraft cable is for the lifting and opening of garage doors, a time saving application. Garage door openers are driven by a change drive that slowly pulls or releases a cable that is attached to the garage door. Although the mechanism functions smoothly and slowly, the angle and weight of the garage door places a great deal of tension and strain on the lifting cable. It is for these reasons that aircraft cables are ideally suited for the application.
Exercise Equipment
The exercise and work industries have rapidly grown in recent years due to concerns regarding health and exercise. While in past years, going to the gym or exercising at home meant lifting weights, jogging, and stretching, modern gyms and personal exercise equipment include a wide range of equipment that has replaced barbells and medicine balls. Weights on various mechanisms are connected to cables that can be adjusted according to the desired weight and lifting angle. The connections in the mechanism are made by aircraft cables, which are used all over gyms as parts of modern weight lifting equipment and commercially sold equipment.
Leading Manufacturers and Suppliers
Chapter 5: Types of Aircraft Cables
Although each type of aircraft cable is the same, there are adjustments and changes in the manufacturing of the cable that differentiates one type from another type. These changes can be the type of metal being used, coatings, lubricants, and other factors that can make a certain type of aircraft cable unique. When planning to purchase aircraft cable, it is important to be aware of these differences to ensure the cable that is purchased matches the application for which it was purchased.
Metals
Aircraft cable is available in galvanized steel and stainless steel. The choice of metal is dependent on the use of the cable and its cost since stainless steel is more expensive than galvanized steel. Applications in harsh, hazardous environments with chemicals and moisture require the use of stainless steel aircraft cable. Less aggressive conditions, where chemicals and moisture are not present, allow for the use of galvanized steel aircraft cable. The process of winding of each type is the same and involves 7x7 and 7x19 constructions.
- Stainless Steel – Stainless steel aircraft cable is used where there is corrosion, and increased cost is acceptable. Series 302 is the most commonly accepted used for its resistance to corrosion and strength. Other types of stainless steels are 304, 305, 316 and 321, with each having a unique advantage. Series 305 is used when non-magnetic properties are required and the loss of strength is acceptable.
- Galvanized Carbon Steel – Galvanized carbon steel is used when strength is important and resistance to corrosion is not a factor with its lower cost being a consideration. Galvanized carbon steel wires are coated with a layer of zinc for protection from the environment.
Push Pull Aircraft Cables
Push pull aircraft cables control movement in two directions and are resistant to wear and weather conditions. They activate equipment using mechanical force and are specifically designed to meet the needs of an application. The design of push pull aircraft cables enables them to translate motion and force over any distance. Aircraft push pull cables are used in several applications due to their strength, dependability, and durability.
Connector Cables
Connector cables are the most common use of aircraft cables for supplying connections that are strong, sturdy, reliable, and long lasting. The performance of connector aircraft cables is influenced by the amount of tension they must endure and their linear movement. Aircraft cables are compatible with most standard terminals and have the specifications to perform in any environment.
Aircraft Cable Coatings
Regardless of the type of metal used to produce aircraft cable, the cable may be coated with different materials, such as polyvinyl chloride (PVC), nylon, or high-density polyethylene (HDPE), for extra protection. The presence of the coating helps the strands in the cable retain their form and alters the outside profile of the cable. The reasons for the use of coatings include protection, ergonomics, aesthetics, and visibility.
Extrusion is used to apply the various types of coatings and involves melting resin pellets in an extruder. In the extruder, the resin pellets are heated and melted. Aircraft cable is reeled out and pulled through the liquified coating. To maintain consistency of coverage, a pulley system is used to maintain tension on the cable as it passes through the melted resin.
- Polyvinyl Chloride (PVC) – PVC is the most common form of coating used for aircraft cable. It can be applied in standard and custom colors to meet the needs of an application or brand.
- Nylon – Nylon 6 and Nylon 11 are used for aircraft cable for high friction applications and to extend the life of the cable. The higher temperature rating of nylon makes it ideal for special applications.
- HDPE – HDPE is selected for use for specific and unique applications. It is exceptionally durable and suitable for low temperature conditions.
Chapter 6: Reasons to Use Aircraft Cable
There are several factors that separate aircraft cable from all other forms of cable, the most notable of which is its exceptional strength and durability in the most stressful conditions. Aside from this outstanding quality, aircraft cable has other characteristics and qualities that makes it an excellent choice for stressful applications.
Strength
Since its introduction, aircraft cable has been subjected to a wide array of stressful conditions including tension, acceleration, load shock, bending, and a multitude of outside forces. Regardless of the severity of these many stresses, aircraft cable has endured and performed flawlessly.
Safety
The safety factors of aircraft cable varies in accordance with its workload. The ratio of the strength of aircraft cable to its workload is the barometer used to determine how safe the cable is. In most cases, aircraft cable is capable of enduring several times its measured workload.
Fatigue
A common problem with wire rope and cable is fatigue, which appears as cracks after bending the cable multiple times. This normally occurs when cables pass over a surface and are straightened. As fatigue increases, by the bending of the cable’s wires, the cable breaks. Unlike typical cables, aircraft cables have a flexible construction due to its small wires, which prevents the effects of fatigue.
Abrasive Wear
The ability of aircraft cable to withstand abrasive wear is due to the quality of the wires used in its construction. Although aircraft cable is more likely to have abrasive wear due to its flexibility, how it is used and maintained has a substantial influence on its resistance to abrasion. The higher grade of galvanized and stainless steel wires provides the strength and resistance necessary to overcome abrasive wear.
Chapter 7: Aircraft Cable vs Wire Rope - The Difference
The terms wire rope and cable are often used interchangeably but actually refer to two different types of wound wire products. The difference between them is rather simple and refers to their sizes. Of the two forms, aircraft wire is smaller and categorized by experts as cable, cord or aircraft cable.
Aircraft cables and wire ropes involve the use of wires that are twisted together to form strands with multiple strands being twisted together to form a single wire rope. The construction of aircraft cables includes 1x7, 1x19, 7x7, and 7x19 configurations. Wire rope has a more expansive set of configurations covering a wide range of diameters and sizes with some types of wire rope having different strands with different widths.
Aside from other factors, the fundamental difference between wire rope and aircraft cable is their diameter. Wire rope has a diameter that is greater than 0.375 in (9.5 mm) while aircraft cable has a diameter that is less than 0.375 in. This difference restricts the size of wires that can be used in cables and lets wire rope use any size wires as well as different size wires in the same strand.
Other Factors
Strength
Wire ropes are far stronger than cables and are used for heavy duty and strenuous applications.
Flexibility
Cables are thinner, more flexible, and extremely strong. The flexibility of cables makes them suitable for a wide range of applications.
Abrasion Resistance
An increase in the flexibility of wire rope and aircraft cable increases their vulnerability to abrasions with wire rope being less vulnerable, while aircraft cables are more flexible and susceptible to abrasions.
Fatigue Resistance
Breakage due to fatigue is common for wire rope and aircraft cable with cables being less susceptible due its flexibility. The key to the lifespan of wire rope or aircraft cable is the application for which they are used.
Conclusion
- An aircraft cable is a style of highly durable cable that is used for aircraft flight controls and other applications and is differentiated from normal cables by its stranding, diameter, and wires, which provide its strength and flexibility.
- What differentiates aircraft cables from other forms of cables is their number of strands and the number of wires per strand. Generally, aircraft cable has a diameter of 0.03125 in up to 0.375 in (0.79 mm up to 9.5 mm) with a 7 by 7 or 7 by 19 construction and a wire core that is the same as the outer strands
- The strength and durability of aircraft cables makes them ideal for a wide variety of applications. A key factor in their use is how they are connected to the process for which they are designed.
- Of the various types of cable and wire rope products, thin, strong, and flexible aircraft cable has been found to be the most useful and reliable. Its stranding of thin steel wires gives it the strength and durability that can be used by a wide range of applications.
- Although each type of aircraft cable is the same, there are adjustments and changes in the manufacturing of the cable that differentiates one type from another type. These changes can be the type of metal being used, coatings, lubricants, and other factors that can make a certain type of aircraft cable unique