With all the attention focused on the new technology, it is easy to overlook the critical role wire and cable plays in the development of the next-generation aircraft. Using an array of materials and system designs, wire and cable developers are striving to meet growing capacity demands, while holding the line on size and weight and meeting stringent regulations. It is an effort filled with daunting challenges and opportunities.
Like many other technology segments, the industry is caught between the seemingly competing demands to provide smaller, lighter products and greater capacity to meet the power needs of in-flight entertainment (IFE) systems. For operators, however, the overarching goal is fielding fuel efficient planes, said Mark Sawyer, global director of wired cable for TE Connectivity-Aerospace, Defense & Marine. “Everyone has got one eye on the cost of fuel and (is) looking to drive down their operating costs.”
When looking for places to cut, wiring is, in its way, a big target. For example, there is about 171 miles of wiring on the 747-400s, according to Boeing. The key is reducing “size and weight without sacrificing quality,” said Scott Allan, vice president of sales and marketing at PIC Wire & Cable, based in Sussex, Wis. “It is easy to use cheaper/lower temperature materials or remove shielding to reduce size and weight, but that has a negative impact on quality, safety and/or performance.”
With this in mind, a great deal of research and development is being focused on insulation and conductor materials. Many of these efforts have been going on for some time, in some cases yielding mixed results. However, “the breakthroughs have to come from materials science,” said Sawyer. Noting the company’s expertise in this area from its Raychem legacy, Sawyer said, “TE is investing heavily around technology, materials, (and) process innovations.”
There has been “some headway being made on different insulating materials (coming) from just the increased emphasis by the manufacturing community on producing higher performing products,” said Bob Scott, senior wire and cable product manager at A.E. Petsche, Arlington, Texas, a distributor of wire and cable products. The progress has come “primarily in expanded PTFE material.”
Often, the key is balancing properties of the different materials.
“There is a continuing effort to make the wire insulation thinner, and obviously the thinner it gets you get a reduction in weight as well,” said Michael Traskos, president of Lectromec, a wiring test company based in Dulles, Va. However, it is a task rife with serious issues. For example, the basic PTFE or ETFE type insulations “do limit the severity of arcing events, but the more you reduce the insulation the less effect it can have in terms of reducing that damage” from these occurrences.
“From what I can tell, however, the main industry desire is to have insulation that goes up to a higher temperature and is more abrasion resistant,” said Traskos. “The higher the temperature the more current you can push down the wire … (allowing for) the use of fewer wires to accomplish what you need, which would be a way to reduce weight.” At this point, developers “can’t find anything that goes up to 300 degrees Celsius with much consistency, so the next step is to find that next highest temperature.”
“We’ve seen a need to have cables meet BMS13-58 (specification), which is rated to 260 degrees (Celsius),” said Kerry Stuckart, product manager-coax cables at Emteq, based in New Berlin, Wis. “Customers want the higher temperature rating to avoid separating wires when routing.”
Fiber, Aluminum Options
Along with insulation, operators and developers are looking at lighter weight replacements for copper as a conductor, such as fiber optic and aluminum solutions. “Fiber is great from a weight savings and data transfer angle (and reduces) wire bundle sizes,” said Stuckart. Along with greater bandwidth and speed, you also “take away the EMI [Electromagnetic interference] issue associated with copper,” but there are lingering questions about fiber’s reliability, added Sawyer.
In fact, “the adoption of fiber into the aviation industry (has been) … slower than expected,” said Stuckart. “There is still hesitancy, mainly due to the criticality of termination, especially in the field.” Still, Stuckart predicts: “It will become more widely used and accepted as the avionics equipment manufacturers specify fiber as requirements for their avionics equipment.”
Currently, there are commercial and business aircraft that are projected to use more fiber optic cable, and “I think the industry is waiting to see how these platforms perform with these products.”
Carlisle Interconnect Technologies, based in St. Augustine, Fla., is releasing a new fiber optic cable product, LITEflight HD Fiber Optic, designed to offer increased bandwidth, lower weight and immunity to electro magnetic interference.
The LITEflight HD cable is designed around compatibility with multi-fiber connectors, allowing the routing and simultaneous connection of multiple fibers in an extremely compact package. A 12-fiber bundle, capable of transmitting a dozen 100 Gigabit-per-second data streams simultaneously, is contained completely in a rugged, routable and aerospace qualified cable only 3.8mm in diameter.
Daniel Bagby, Carlisle Interconnect Technologies fiber optic product manager, said emerging demands for greater bandwidth, combined with the need for lighter weight, are driving more system designers to consider fiber optic interconnect for their system installations.
“Although advancements in high-speed Ethernet across twisted-pair copper cabling have increased the available bandwidth in these systems, the development has not produced a significantly lighter or more cost-effective interconnect solution. Maintaining signal integrity across a copper cable requires significant shielding to protect from signal crosstalk and EMI, this shielding comes with a considerable weight penalty and still only offers a marginal increase in available bandwidth,” he said.
Meanwhile, some OEMs, most notably Airbus on the A380, are using more aluminum wiring, said Traskos. Aluminum does provide a weight savings. However, “one concern is that when you crimp down on aluminum wire you can damage the plating, which can then lead to corrosion,” he said. “Aluminum is a softer material, which means that the insulation does need to hold better, (and) when you get down to a 20-gauge wire for some of the constructions, the insulation when subjected to a pull test … will sometimes last longer than the conductor,” he said. “The insulations that are out there are very strong and do a very good job, but if you make the conductor weaker … that means you just have to put even more trust in your insulating materials.”
Another approach airlines could take to drive down size and weight is to move to higher voltages, said Sawyer. With “higher voltage pushing current from point to point, you can go for smaller-sized or smaller gauge wire which, of course, drives lighter weight and a lower occupied volume.” However, those higher voltages “put more demands on the insulation. So again, you’ve got to balance the properties,” he said.
“There is an opportunity to offer a markedly … (improved) product to the marketplace if you truly understand the requirements,” said Sawyer. “One could say that materials in their pure form may be limited, but... there are (also) combinations of materials that (can be) alloyed and blended.” He suggested in the future there could be higher speed end-to-end solutions using copper fiber hybrids, for example. “We are (also) looking technology around carbon nanotubes,” he said. “Carbon nanotubes laid down the right way are very conductive.”
All of these R&D efforts are further complicated by the use of composite fuselages on the new generation aircraft and the Electrical Wire Interconnection Systems (EWIS) regulations. With the shift to composites, developers will rethink all “the things (they) … took for granted with having a metallic fuselage … like Faraday cage (and) EMI,” said Sawyer.
The responsibility for fulfilling EWIS regulations falls mainly on the OEMs and operators. However, there could be some impact on providers. For example, by assuming there will be a wire failure, the regulations stress ensuring the systems are properly separated from one another, Traskos said. In some instances, providers could “actually have to have … some sort of laboratory evidence that this wiring bundle can be this distance from (for example) a fuel tank or hydraulic line or other wires.”
Then there are cost issues. With the price of raw materials on the rise, the costs associated with “designing and manufacturing a cable to meet both small outer diameter and low weight” demands can be a challenge, said Stuckart. Often, “customers want the size reduction and weight savings, but they don’t want to pay additional money up front for it, even though it will be more cost effective in the future.”
Despite these technology and cost challenges, the changes spurred by the growth of digital technology on aircraft is providing opportunities for wire and cable vendors, who are painting a picture of a reviving if not entirely robust market.
“We’ve definitely seen the uptick in the forward fit market, and believe we will continue to do so, especially as some of the new platforms, such as Honda Jet, Gulfstream G650 and the Lear 85 aircraft, move into production in the next one to three years,” said Stuckart. “The aftermarket is still strong for us and (we) believe others.”
Emteq introduced this year two high-definition multimedia interface (HDMI) cables designed to deliver 1080p video to entertainment and business modules: a 26 AWG cable that runs up to 20 feet and a 24 AWG cable that stretches to 50 feet. “We feel this is a niche offering as there are very few cable manufacturers offering prefabricated and tested HDMI cable assemblies,” Stuckart said, adding the product has already generated sales, orders and interest from both forward and retrofit market, she said.
For PIC Wire & Cable’s Allen, the market outlook is more mixed. He said the higher end of the corporate jet market was starting to rebound after dropping significantly in 2008. “The military market has remained stable, but we see that trending down in the future; however, this business could shift to retrofits.”
With customers showing a desire to have the same video technology on their planes that they have in their houses, the use of SMPTE Video cable with 75 Ohm impedance match connectors “has been a growing trend in corporate aircraft,” said Allen. The company offers a 26 AWG SMPTE 292 cable and a 20 AWG SMPTE for longer cable runs. To go along with its 75 Ohm cable offerings for video applications, the company is launching a line of high-frequency cables to meet the growing demand for this technology in aviation applications, said Allen.
TE Connectivity a variety of high-performance wire and cable solutions including its Spec 55 airframe wire and cables, Cheminax high-speed transmission cables as well as the Quadlite family of light-weight, fluoropolymer cables are for use in high-speed, high-bandwidth applications, such as 100 Base T, Gigabit Ethernet. However, a key focus of the company is an end-to-end systems approach tapping its portfolio of offerings.
“A good example of a systems approach would be our fiber to the screen (FTTS) solution that we worked … with (Irvine, Calif.-based) Lumexis to develop,” said Sawyer. Using fiber optics technology, it provides a “flexible routing approach that maintains room for … the expansion of the system and is based on a ARINC 801 fiber optic interface, so it is based on a standard protocol using the fiber optic contacts and a cable solution for modular solution for IFE,” he said. The modular system fills the “need for higher bandwidth higher speed (and) size and weight (reduction)” while allowing operators “to play around with the configuration of the aircraft.”
After successful flight trials of the system on a US Airways A320, Lumexis received a contract to provide the FTTS system fleet-wide for flydubai, a low-cost sister carrier of Emirates, which took delivery of the first fully equipped Boeing 737-800 in 2010.
Next month: Databus
Avionics Magazine’s Product Focus is a monthly feature that examines some of the latest trends in different market segments of the avionics industry. It does not represent a comprehensive survey of all companies and products in these markets. Avionics Product Focus Editor Ed McKenna can be contacted at firstname.lastname@example.org.
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