Hybrid interconnects set to meet future aerospace needs

Robustness for signal integrity tends to frame the connectivity issues for this sector. Connectors have to cope with shock and vibration at various levels, at different times and in different parts of the plane – takeoff has different performance considerations to cruising and the cabin is very different to the cockpit in terms of what is specified. "Where they are used on the airframe tends to define which sort of connector is used," said Steve Webster, European industry specialist, military/aerospace, at Molex. He described how the aerospace connector market has generally followed the military market, with the mil spec 38999 proving very popular. In terms of backplanes and slot in modules, the ARINC specification has also been widely used. "The 38999 is forecast to be in demand for years to come," agreed Alec Sluce, product manager at Aerco. He proposed that what we're seeing now is manufacturers focusing on making smaller and enhanced versions of these products rather than moving away entirely. For example, Glenair is making Mighty Mouse connectors, which offer push/pull and bayonet mating, as well as threaded mating, to give designers more variety. "Effectively, they're trying to get more out of fewer connectors," said Sluce. "Many connectors now have mixed contacts." He emphasised that the role of space and weight savings are driving proliferation of connectors with multiple uses. An example could be Harwin's Mix-Tek range. Harwin says that running signal and power in the same connector not only saves space on the plane, but also back at the warehouse. "The connectors that are being looked at in standards committees at the moment tend to be a lot more hybrid than a single solution," commented Webster, who also suggested a growing demand for modularity in connectors. As well as more hybrid devices, Webster believes fibre optic technology will become more prevalent. "We haven't seen the much vaunted move towards fibre," admitted Sluce. "It hasn't happened at the sort of pace people predicted." He believes this is because data rates for copper have become higher than expected, so designers have been able to get much more out of it. "If users change to a completely new method for routing signals, there can be a lot of cost involved in the physical changeover," he said. "Once your fibre is up and running, your ongoing cost is much lower, but it's that initial changeover period." Aerco may have noticed few customers asking for fibre, but Sluce proposes this might be because fibre sales tend to be directly between the manufacturer and the oem, rather than involving a distributor. When the takeup of fibre is more widespread, distributers will join in. "Fibre has a lot of advantages, but the death of copper has been put off for a few more years yet," he added. According to Webster, the potential for fibre optic technology has brought with it many questions about taking advantage of what has previously been used in the military. As these solutions tend to be more expensive, companies like Airbus and Boeing are investigating more commercial off the shelf (COTS) solutions to stay competitive. "They're looking to use more COTS that are standardised, but aren't typically military connectors," said Webster. "An example could be the EN4165 connector family, which is more compact, cheaper and better performing than the old ARINC solutions." With more of these solutions being seen, Webster noted the market is looking to best support top level requirements, whilst implementing fibre optics, meaning transceivers will be needed to transfer the signal from copper to fibre, then back again. "The aerospace market is being driven by the commercial market's availability of cost effective solutions for transceiver technology," he said, "and that's moved on apace in the last 3 to 5 years." Webster argues these solutions are now more cost effective due to experience from the datacoms/telecoms market, so we will be seeing them sooner, rather than later. Both Webster and Sluce see growing need for connectors for in flight entertainment (IFE) applications. Webster envisages more local area networks being constructed within the plane to support wireless devices and additional multimedia being built into the seat, causing seat manufacturers are looking at their different connectivity module options. These will need to ensure there is enough bandwidth for potentially everyone on the plane to stream a video at the same time. More complex electronics means more connectors. "The cabin environment is relatively benign", said Webster, "so that will drive the use of standard connectors to keep costs down." These aerospace connectors will not be flight critical, so customers won't be tied into using military spec connectors, but high reliability and high mateability will still be required. Jamie Furness, general manager UK, Ireland & South Africa at TTI, sees increasing pressure on manufacturers to bring out new aerospace ratings that aren't mil spec, but still accommodate the performance. "At the moment, there's a bit of a no man's land in that they don't need ruggedised HDMI connectors," he said. "But they do need strong HDMI connectors that can withstand high amounts of mateability." When it comes to connectors for IFE, quality is key – no one wants to be ripping up the floor of the cabin because the connectors have failed. In Webster's view, this is a major consideration if fibre is used. "The biggest risk from a user perspective is maintenance," he said. "Installation as well. Sometimes you have to terminate the connector on the plane itself; you have to repair the connector in situ and this is more onerous than reterminating a copper connector." Plus, fibre won't perform if there is dirt or scratches on the end of the terminations. Webster suggests this is driving a new fibre optic technology with an expanded beam, which is less susceptible to dirt and scratches. Webster is confident the main driver for the market will be fibre optics and notes the presence of various formal and informal industry working groups looking at requirements for future architectures and their potential impact. Although Sluce believes fibre is on the cards, he cites talk of copper reaching speeds of up to 40Gbits/s to illustrate there could still be a lot more to come first. "We're only at the start of the high speed revolution," he concluded. "Sometimes, connectors can play a bit of a catch up with everything else." Gecko connectors launched At electronica this week, Harwin is unveiling a connector family based on a 1.25mm pitch that it says will offer significant weight savings in aerospace applications. Devices in the Gecko range are said to offer a 35% space saving over other connectors and Harwin claims its four finger copper alloy contact allows the G125 family to operate in temperatures ranging from -65 to 150°C and under Z axis vibration of up to 100g.