Saturday, January 1, 2011
Product Focus: Switches
Manufacturers strive for lower-profile and solid state solutions. Touchscreen technology offers design flexibility.
In a drive to boost efficiency and lower costs, fundamental aircraft components, including cockpit switches, are being required to use less space and energy, or in the industry parlance, to adopt a lower profile.
To reduce the profile of their products, switch manufacturers are using new materials and technologies, and some are introducing touchscreen products, to make optimum use of the limited available cockpit real estate. At the same time, they are dialing down their products’ energy consumption through increased use of light emitting diode (LED) technology.
Many companies already offer smaller, low-profile products. Many tout 5/8-inch-square pushbutton switches. “In integrated displays, where legend requirements are more limited, we have seen buttons that are as small as a half-inch by three-eighths inch,” said Terry Trumbull, vice president of Electro-Mech Components, based in South El Monte, Calif.
The main focus now, however, is on reducing the length or depth not just of switches but of all cockpit avionics, said Bob Witwer, vice president of advanced technology for Honeywell Aerospace.
Why? “Imagine if nothing attached to the front of the cockpit was more than one-inch long,” he said. “You could move the cockpit forward,” which would allow for more cabin room on a business jet or passenger space on commercial aircraft.
Responding to this challenge, Staco Systems, of Irvine, Calif., in June 2010 introduced its Series 200 pushbutton switches, which it claims are the lightest at 11 grams and the shortest, with behind-panel depth of 18.87 mm, or 0.71 inches, on the market.
The switches represent “a major technological shift,” said Jason Childs, Staco Systems vice president of sales and marketing. “We used completely different technologies (including) different plastics, different contact materials; and the way the switch actually functions is different. Several (new) patents were involved.”
Staco Systems is testing the switches with new aircraft, while already retrofitting them on existing airplanes. In one case, an operator selected the switches so it could deploy a wire bundle along the back of the panel, Childs said.
Size is “always an attractive feature and benefit (but) we have kind of taken a little bit different approach,” said Craig Morgan, vice president of sales with Aerospace Optics, based in Fort Worth, Texas. “We have elected to not necessarily concentrate on getting every possible thousandths (of an inch) in size out of the unit, but to enrich the component’s performance.”
The company’s Vivisun Logic Series switches may occupy the same piece of real estate as before but now can perform the functions of up to 10 component items that would have been traditionally external to the switch, Morgan said.
“Instead of just (being) a momentary action switch, the same switch can be a latching switch,” said Morgan. “You have cut your demand for hardware in half right there.”
The company’s Pulse/Timer switch, introduced late last year, could replace the functions of such external components as time-delay relays, external-pulse generation circuits and relays that are used to change signal polarity.
The technology also eases pilot workload. “If you turn off the power and walk away from the aircraft, our new switch will reset itself, so when you come back everything is in an off mode,” said Morgan. “Traditional switches would require the operators to manually reset or turn them off.”
The Logic Series are electro-mechanical switches but feature integrated, solid-state circuits to boost their versatility. In fact, companies are making increased use of solid-state technology to scale down and upgrade their offerings.
The market “is definitely evolving away from electromechanical to solid state; in 10 to 20 years it could all go solid state,” said Electro-Mech’s Trumbell.
Last February, Electro-Mech released the SW44687 potentiometer switch assembly, a lightweight, all-in-one unit that saves panel space. It weighs less than one ounce, measures less than ¾-inch square, requires less than one inch of space behind the display panel and mounts via either a quarter -inch diameter threaded bushing or optional mounting block to the mounting plate. Interconnection is provided via either wire leads, PC pins or solder lug terminals.
Solid-state switches typically have a smaller profile than comparable mechanical components and are more reliable. Even the most advanced electro-mechanical switches rely on metal contacts to generate energy which limits their lifespan, observed Bruce Maxwell, president of Luma Technologies, based in Bellevue, Wash.
“You can burn them up,” said Witwer of Honeywell. With solid state, there are no contacts to wear out or burn up — “a magnet passes in front of a semiconductor device and generates voltage,” he explained.
But there are tradeoffs. Electromechanical is a commonplace, relatively low-cost and proven technology, Maxwell said.
With solid-state technology, pilots don’t have the same “user interface and the tactile feel” although the mechanical feel can be added, said Trumbell.
“Electromechanical can handle higher electrical loads,” but that capability is not as necessary in current cockpits using systems with much lower electrical loads.
Korry Electronics, an Esterline Technologies Corp., subsidiary based in Seattle, has been spearheading the move to solid state with its Opticon switching technology. The company says the combination of a lower profile solid-state switch and digital interface weighs half as much as conventional technology.
Other companies, including Luma, are using Hall effect technology to produce a voltage difference across a conductor, which has “been around in automotive and industries forever,” said Maxwell. The Hall effect is often identified as a type of solid state although that view is controversial. It has mechanical components but doesn’t rely on contacts for voltage.
“It can go well in excess of one million cycles” unlike electromechanical technology, where you would be “lucky to get (more than) 100,000,” said Maxwell. For the record, he said, Luma’s LT-2000 Series switches are a half-inch thick but are designed specifically for cockpit terrain awareness systems.
Electro-Mech Components also uses Hall effect technology in its compact potentiometer switch, which offers pushbutton and rotary control for audio volume preset in avionics cockpit applications.
Ducommun Technologies, based in Carson, Calif., is looking at Hall effect among other technologies, including Piezo switches, at least in part to “address the depth factor,” said Laura Hanks, Ducommun Technologies director of business development. Hanks said Hall effect technology has its own challenges, noting that it relies on magnetic elements that are not as conducive to an avionics environment as current technology.
However, discussion of switch depth is “overshadowed” by the steady movement away from these components to touchscreen displays, said Hanks.
“Almost all of the new cockpit designs that I have seen, including retrofits and upgrades, are hugely dominated by AMLCDs,” she said. “We are developing products in that market space because we think our existing market is in slow but steady decline.” Ducommun introduced a Multi-Input Interactive Display Unit at the 2010 Farnborough Airshow.
These types of displays could lower equipment costs by supporting a number of electromechanical controls and “make better use of the cockpit real estate,” Honeywell’s Witwer said. Touchscreen technology also will boost design flexibility, as modifications could be made or functionality added by making software changes rather than retooling hardware.
Witwer said safety-critical situations, such as turbulence, pilot fatigue or a smoke-filled cockpit, will prevent a complete conversion to touchscreens.
“I don’t think touchscreens are going to replace all electromechanical switches,” he said. “Fuel cutoff and a number of other switches that the pilot needs to be able to get to instantly, with high reliability, are good candidates to remain mechanical.”
Touchscreens can, however, be deployed to take care of a number of functions, such as providing graphical status updates of the electrical system, flight-control system and hydraulics. A map display is an example where it is “really intuitive for people to, when they want to move it, put their finger on it and slue it,” Witwer said.
In making systems selections, it is critical to adopt “what we at Honeywell call a human-centered systems view of cockpit,” said Witwer. The focus should not be on the technology as much as on the central mission of “reducing pilot workload by improving the man machine interface.”
As it sorts through different switching technologies, the industry continues its efforts to boost energy efficiency and rid excess heat by replacing incandescent with LED lighting. This initiative is being pressed by the efforts of major aircraft companies, including Boeing, Airbus and Gulfstream, to produce more fuel efficient, “greener” aircraft, said Childs.
“LED is clearly the path of the future. That said, it is a more expensive” to produce and presents some challenges for retrofit, said Ducommun’s Hanks.
Short of a complete conversion, there are challenges associated with integrating LED with incandescent components in the cockpit, she said. For example, it is difficult to achieve “uniform dimming” because of the difference in the nature of lighting technologies. Unfortunately, the technology fix for this, pulse-width modulation, undoes much of the good gained from LED technology by adding more weight and electronics.
Gulfstream Aerospace in November won FAA approval to retrofit Gulfstream IV, GIV-SP and GV aircraft cockpits with light-emitting diode (LED) lamps via two Gulfstream aircraft service changes. The LED lamps were developed by Gulfstream to replace up to 700 incandescent bulbs throughout the cockpit, depending on each aircraft and its configuration.
In general, retrofitting switches “is a pretty major undertaking,” said Luma’s Maxwell. “You have at least four to six wires on each switch just to control the lighting, and on a major Boeing cockpit there are upward of 60 to 80 switches.”
However, there are innovations being offered, such as “poke home” technology, which makes it easier to replace the lighting “without having to upset all the wiring,” he said. There are also products referred to as LED modules, which allow for the replacement of just the cap assembly rather than the whole switch.
Following are some recent developments announced by manufacturers of cockpit switches.
➤ Luma Technologies, of Bellevue, Wash., in October introduced the LT-4500 line of integrated LED Caution Warning panels.
The product line includes six separate panel sizes, which are installed as a drop-in replaceable, two-panel suite for the model in question. They also provide enhanced EMC/EMI protection. Luma’s LT-4500 offerings are contained in a single integrated unit for either the glareshield or center console positions. All units carry a five-year warranty and NVIS compatible versions are also available.
➤ Ducommun Technologies, based in Carson, Calif., in June was awarded a contract from Boeing to deliver Next-Generation 737 engine start switches. The rotary switches will support all models in production as well as classic 737 platforms, beginning in 2011, according to the company.
In April, Ducommun received the second installment of a multi-phased contract from Boeing for retrofit of the Caution Light Panels (CLP) on F/A-18 fighters, as part of the U.S. Navy Caution Panel Warning System (CPWS) Upgrade Initiative. Deliveries on the initial order supporting current F/A-18 production as well as the upgrade of more than 300 aircraft were completed in 2009. The follow-on order supports upgrades for additional F/A-18 aircraft with deliveries scheduled through 2010, according to the company.
➤ Staco Systems in August opened its new headquarters facility in Irvine, Calif. The 40,400-square-foot building offers more than double the space of Staco System’s previous headquarters in Costa Mesa, Calif., and is equipped with an in-house lighting design and qualification lab. In addition, Staco Systems said its operations and manufacturing divisions have the additional space needed to meet expanding customer demands.
➤ Eaton Corp., Shanghai Aviation Electric Co., Ltd. (SAE) and Commercial Aircraft Corporation of China, Ltd. (COMAC) in July signed a letter of intent for Eaton to supply cockpit panel assemblies and the dimming control system for the COMAC C919 family of narrowbody aircraft.
The total value of the program is estimated to exceed $425 million, based on an anticipated volume of 2,500 aircraft, according to Eaton, based in Cleveland, Ohio.
“The award of the C919 cockpit panel assemblies and dimming control system business will strengthen Eaton’s presence in China’s emerging aerospace market while expanding our capabilities to serve customers worldwide,” said Brad Morton, president of Eaton’s Aerospace Group.
AeroFlite Enterprises www.aeroflite.com
Aerospace Optics www.vivisun.com
Ametek Aerospace www.ametek.com
Avionics International Supply www.avionicsinternational.com
AvTech Corp. www.avtcorp.com
B/E Aerospace www.beaerospace.com
Cole Instrument Corp. www.cole-switches.com
Crane Aerospace & Electronics www.craneae.com
Dallas Avionics, Inc. www.dallasavionics.com
Ducommun Technologies www.ducommun.com
Eaton Corp. www.eaton.com
Electro-Mech Components www.electromechcomp.com
Electro Switch Corp. www.electroswitch.com
Esterline (Leach, Korry) www.esterline.com
Flame Enterprises www.flamecorp.com
HS Electronics www.hselectronics.com
IDD Aerospace Corp. www.iddaerospacecorp.com
Interface Displays and Controls www.interfacedisplays.com
Luma Technologies LLC www.lumatech.com
Marine Air Supply Co. www.marineairsupply.com
Panelight Components Group, LLC www.panelightcomponents.com
Peerless Electronics www.peerlesselectronics.com
Spectralux Corp. www.spectralux.com
Staco Systems www.stacosystems.com
Teledyne Relays www.teledynerelays.com
Tyco Electronics www.tycoelectronics.com