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Friday, February 1, 2008

Product Focus: Connectors

Aviation-grade connectors are being designed to work with new composite structures and to support high data rates, moving connector manufacturers in new directions

Barry Rosenberg

Few other components in aerospace have changed as little as connectors have over the years.

However, the connector has been roused from its slumber by the introduction of new aircraft — Boeing’s 787 Dreamliner, in particular — and by the revolution in high-speed, high-bandwidth data transfer. As a result, the connector industry is helping to facilitate an electronics evolution in aerospace.

As the aerospace and defense industries can attest, a rising tide raises all ships — even down to the smallest components like connectors.

"It’s a very interesting time in the connector world right now," said Andy Gibb, product manager for filter connectors with Deutsch Connectors, East Sussex, U.K. "Over the next 10 years, connectors will change very dramatically from where they are now. There are a lot more systems on aircraft, and we’re seeing an increase in fly by wire, IFE and power management requirements. There is also a lot of bus-type information flying around the aircraft, as well. That’s reducing the number of signal sets you have and it changes the way connectors are designed."

Dominique Buttin, executive vice president of aerospace and defense for French connector manufacturer Radiall, based just outside Paris, said the aerospace connector business is doing well because its customers are doing well.

"The aircraft manufacturers are building more aircraft, which is increasing demand for receptacles on the equipment side and plug connectors on the airframe side," Buttin said. "Then there are more new aircraft, so there is more opportunity to bring in new technologies. The competition between Airbus and Boeing is having a good affect from that standpoint because they have to take more risk and more challenges. There’s also more pressure on cost and we have to be more competitive."

Customer demands for fuel-efficient aircraft and the role of connectors toward that goal, the ruggedization of commercial products and speed and bandwidth are driving a lot of product research and development in the aerospace connector industry, said Russ Graves, business development manager for Tyco Electronics, Berwyn, Pa. Tyco Electronics designs and manufactures an array of fiber optic, ruggedized and high-speed connectors for the aerospace industry. More specifically, the company manufactures, among other products, a circuit board connector system that enables data rates up to 10 gigabits per second and a highly modular, high-speed ruggedized connector.

"The market is quite robust, particularly on the commercial aerospace side," said Graves. "There are a number of new platforms that we are all working toward. The future for the industry is very positive."

Composite Challenge

Advanced composite materials, including solid carbon fiber laminate used in the aircraft wing and fuselage, will make up about 50 percent of the construction of the Boeing 787, which is slated for delivery in late 2008. Composite construction, which is more fuel-efficient, is becoming an issue for connector manufacturers as the technology trickles down to smaller components.

"When you have a composite structure you do not have a Faraday cage (a conducting cage used to shield electronic equipment) to protect systems against lightning or EMI influences," Buttin said. "Composites are plastic and not conductive, so system connectors are more subject to external influences. We’ve changed (some of) our metal connectors to composite connectors. But composite in itself is not conductive and lightning would fry all the electronics and destroy the airplane. So you need a metal plating on the composite to withstand lightning."

Said Graves, "The main drivers in commercial aerospace are around trying to get more fuel efficient airplanes, and that would be moving more toward composite airplanes, moving away from hydraulics to electrical systems, and other ways to increase the speeds on the network-side of the aircraft in order to be able to get more throughput through the various wires and cables."

Another challenge for connector manufacturers is addressing electromagnetic interference (EMI) from the myriad electronic systems packed into modern aircraft.

"One of the largest concerns is transmission of multiple streams of data through connectors without cross talk between the streams," said David Knoll, RF/electrical engineering manager for ECS, of Franklin, Wis. "Cross-talk is minimized by twisting the pairs of wire, but the wires are untwisted when they go through the connector. Because you want to minimize the number of parallel lines going through the connector you want a one-quarter turn or less. The less you untwist the pair the better your chance of success."

Knoll said shorter connectors are better than wider connectors when it comes to improving cross-talk performance.

The transition by airframers and electronics manufacturers to fiber optics also will help relieve interference problems, companies say. "Fiber is one of the big new technologies coming in the market, and with fiber there is no EMI influence because there are no more electrical signals," said Buttin.

Thus far, in the commercial air-transport world, only the Boeing 787 employs significant amounts of fiber, Buttin noted. The design of the Airbus A380 was frozen in the 2000-2001 time frame. As such, the A380 has fewer fiber optic systems — primarily for its in-flight entertainment (IFE) system. However, Airbus is expected to make a larger commitment to fiber in the new A350 medium capacity, long-range widebody, now under development.

"Composite aircraft benefit greatly from the use of fiber optics because then suddenly a lot of the grounding and EMI issues go away," said Gregory Powers, Tyco Electronics business development manager. "So people who are building composite aircraft have their eyes very heavily on fiber optics."

Jay Sandidge, Midwest district manager for Positronic Industries, Springfield, Mo., said fiber optic technology has two major advantages, beside bandwidth. "It is not prone to any kind of interference, like a copper-based conductor would be," he said. "And you can push a lot of data and take a lot of wiring off the aircraft to reduce weight."

Companies such as Radiall, Deutsch, Amphenol, Souriau and ITT Canon are addressing the fiber market with an expanding line of products that didn’t exist just a couple of years ago. For example, Radiall has developed the LuxCis contact, a new generation of high-density, low-cost, fiber-optic butt joint contact upon which the ARINC 801 standard was developed. The LuxCis terminus is based on a standard 1.25mm ceramic ferrule and sleeve and is compatible with standard LC polishing process. The LC connector is a small form-factor interconnect.

LuxCis termini are designed to be pull-proof — the cable jacket is crimped on the external body, and a floating mechanism avoids any loss of contact when pulling on the cable. This feature, which is available only with a semi-loose cable jacket, allows users to employ LuxCis termini without a connector backshell.

Other Factors

An expanded line-up of IFE offerings, particularly in business aviation, is also moving connector manufacturers in new directions.

"A lot of consumer electronics that customers have in their homes are getting put onto aircraft," said Tim Knutson, ECS director of customer service engineering. "We’re trying to use commercial interfaces and make them aviation grade. One of the problems you run into is that aircraft-grade wire has a bigger diameter (than consumer wire) because of insulation for fire requirements. That presents some unique issues because the wires won’t fit into standard connectors. We’re coming up with a way to make conventional connectors work.

"In addition, data rates for IFE are faster than for avionics-type systems. The challenge is providing connectors that can transmit these high data rates without corrupting data or corrupting the data around it."

As always, the perennial demands of faster speed, lower weight and smaller footprints are pushing connector manufacturers to raise the bar. "We’re definitely seeing an increased emphasis on weight savings and manufacturability, while cost savings and increased density continue to be issues," Sandidge said.

Embracing modularity through a decrease in part numbers is a top priority, manufacturers say.

"Typically, aerospace used connectors of different sizes and you had to manage lots of part numbers and arrangements," said Buttin. "For the 787, Boeing wanted to divide by 10 the number of components. Modularity has brought a reduction in inventory."

Connector manufacturers responded by designing inserts and shells that could be mixed and matched in many combinations to create a large number of new connectors. The industry also is shifting toward rectangular connectors and away from circular connectors as a way to reduce the footprint of its products. Buttin said 75 percent of the connectors on the 787 are rectangular.

There are several key challenges for connector manufacturers in the near term, including the need to add metal to composite connectors to protect against lightning and the imperative to understand the technology behind fiber optics.

"Being able to protect a composite connector with metal plating is a very challenging process and only a few manufacturers in the world can master that," said Buttin. As to the fiber challenge, he added: "Traditional connectors use copper. The contacts need to be very well aligned with tight tolerances and precision for the silicon fibers used in fiber optics."

Working to develop a new generation of connectors and cabling that can support gigabit Ethernet operation is the ARINC Cabin Systems Subcommittee, Gigabit Ethernet Technical Working Group. The group is striving to define the electrical performance parameters for connectors and wire that are expected to be developed in the near future. Additionally, definition of uniform test methodology and test instrumentation to verify the component-level and link-level parameters is required.

"Keeping up with the data rates that equipment manufacturers are coming up with will be a big challenge," said Mike Taubenheim, sales engineer with PIC Wire & Cable, Sussex, Wis. "Because of even higher data rates coming, the industry is developing a new generation of connectors that will be able to support gigabit Ethernet.... The most important product they need to develop is a connector to terminate a four-pair, 100 ohm Ethernet cable into a connector robust enough for aircraft use in place of the RJ45 connector."

Powers, of Tyco Electronics, said, "I see an exploding demand for speed and bandwidth, not only within the box, but box-to-box. And what we’re looking at quite a bit is the ruggedization of commercial technologies."

After 2010, connectors are expected to play an important role in embedded sensors and next-generation maintenance capabilities for composite materials used in aircraft.

"We’re working on a method where fiber-optic glass and strain sensors are embedded into the composite," said Andrew Watson, Deutsch product manager for environmental products. "With a delicate fiber embedded into composite you need an embedded connector to take the stress away from the fiber where it comes out. We’ve developed a technology to break out of the side or end. It is still in development. The question is, can we do it?"

Market Moves

Following are some recent developments announced by connector manufacturers.

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