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RF/Microwave??

Dow-Key switches continue to fly on Boeing planes after [nearly] 20 years

Posted: 02 Jun 2006 ?? ?Print Version ?Bookmark and Share

Keywords:RF switch? Dow-Key? Boeing? traffic collision avoidance system? TCAS-II?

Dow-Key said no commercial airplane has left Boeing Corp.'s manufacturing facilities for the past 20 years without its microwave RF switches being outfitted within the aircraft maker's collision avoidance and landing systems.

The company revealed that in the late 1980s, Boeing specified Dow-Key as the preferred supplier of RF switches for use in its traffic collision avoidance systems and instrument landing systems. According to Dow-Key, it provides its switches for Boeing's current fleet of commercial airplanes, including the 777, 767, 747 and 737, as well as the upcoming 787 Dreamliner.

Dreaming big in a mid-size jet
Boeing's mid-sized 787 Dreamliner will be the most technologically-advanced commercial airplane ever built when it's released for service in 2008, said Dow-Key.

A total of 43 supplier partners have provided engineering, materials and components in every area of the 787's design. New engines from General Electric and Rolls-Royce help provide fuel efficiency, nearly 20 percent less fuel than similarly-sized airplanes, and account for an 8 percent overall efficiency in the entire airplane. The 787's one-piece fuselage eliminates the need for 1,500 aluminum sheets and 40,000 to 50,000 fasteners. Further, as much as 50 percent of the 787's primary structure is made of advanced composite material, making the plane even lighter yet more durable. The 787's open-architecture design affords even greater efficiencies, including the possibility of using health-monitoring systems that gives the airplane the ability to self-monitor and report maintenance requirements directly to ground-based computer systems.

In flight, the 787 will carry up to 250 passengers and can travel at speeds up to Mach 0.85, similar to today's fastest wide-body jets, while its advanced safety systems ensure uncompromising passenger security from take-off to landing.

The 787's traffic collision avoidance system or TCAS-II is also equipped with Dow-Key's RF switching technology.

In the air
The purpose of Boeing's TCAS-II, which is mandated by the Federal Aviation Administration (FAA), is to provide air traffic controllers with an aircraft's identification and altitude, while terminal radar provides relative position and distance. In operation, if the system detects a possible in-flight collision with another airplane, it presents to the pilot on the flight deck a series of advisories that tells the pilot to pull up, dive, turn right or left, and so on.

Part of Boeing's TCAS-II employs the use of two antennas, one of the top of the fuselage and one below. Internally, these antennas are connected either to one of two Mode S transponders, which provide redundant support for a portion of the TCAS-II. In order to connect one or the other of the transponders to the two antennas, two Dow-Key 402-167 switches are used.

"While the FAA mandates the use of TCAS-II among all commercial airplanes, it allows for some options, one of which is a redundant Mode-S transponder," explained Carl Abendroth, president of Anzak Corp., an electronic components representative for Dow-Key. "Not all aircraft manufacturers use a redundant system, but Boeing has done so for many years to ensure its customers reliability."

Dow-Key, too, took a proactive approach years ago to assist airlines that already had Boeing planes in the field so that they could comply with the FAA mandate to add TCAS-II.

In 1987, said Abendroth, Dow-Key assisted the airlines and maintenance organizations that used Boeing aircraft by offering engineering guidanceand in some cases even modifications to the Model 402-167 switches themselveson how best to handle the retrofits. Typically, retrofitting the TCAS systems into existing aircraft took airline crews about 1,000 man-hours per plane.

"After Dow-Key's service to the airlines," said Abendroth, "the company became Boeing's vendor of choice for the TCAS-II switch requirements."

On the ground
Equally important to ensuring safety in the air is an aircraft's ability to safely land. The instrument landing system (ILS) in an airplane enables its pilots to acquire the specific RF signal that identifies their runway of choice. The ILS antenna acquires a glide scope signal, which can be described as an electronic highway with a decreasing angle that ends at the threshold of the runway. On all but the 787 Dreamliner, Dow-Key's model 402-188-1 switches actuate Boeing's ILS equipment, allowing the flight crew to choose from a variety of modes in which to land as they get closer to their destination. Depending on the size of these other Boeing aircraft, the complexity of the ILS could require as few as two or three switches or as many as six or eight.

"The pilot can fly the glide path manually," Abendroth continued, "or choose one of the various categories of auto-land, which typically is found as an ILS option on fully-equipped airplanes that do a lot of international travel." Auto-land mode, which includes auto-pilot and auto-throttle modes, is triggered by an extra actuation switch inside the 402-188-1 switch, when it acquires and is switched to that particular set-up antenna at the nose gear door.

"Here too, as was the case with Dow-Key 402-167 switch for the TCAS-II, Dow-Key provided customer service for the maintenance of its 402-188-1 switch," said Abendroth. Because of the higher quantity of switches that would be used on large airplanes such as the 777, Boeing customers wanted to be able to repair these devices in their own facilities should they require it.

"Dow-Key offered to provide them with a Certified Maintenance Manual (CMM) for the Model 402-188-1 switch," said Abendroth. "Essentially, the CMM contains all of the proprietary information about this product: its parts, how it's built, adjusted, disassembled, repaired, reassembled and certified to be able to go back on the airplane. This strengthened the relationship between Boeing and Dow-Key."

Savings in time, money
Dow-Key said it has been able to save Boeing time during its qualification testing process for parts used on new airplane models, as per the Radio Technical Commission for Aeronautics document #D0-160C.

"We have a lot of existing data on other programs that we have qualified," explained Jovita Trujillo, sales operation manager for Dow-Key. "We make it more cost-effective for Boeing by offering a qualification by similarity, which in turn reduces the time and money that the company would have had to have spent on testing from the ground up. This can save them as much as a 50 percent reduction in time specific to testing, which translates to a cost savings from 30 percent to 50 percent."

Trujillo shared that Boeing's internal quality and delivery ratings for Dow-Key's 402-167 and 402-188-1 switches are in the top 90s on the airplane maker's internal scale of 0-100.

"We monitor all of Boeing's orders on an internal weekly and external monthly basis to ensure that its deliveries are always on schedule," she concluded. "From our perspective, it's not just about creating switching technologies, but also being able to deliver solutions to our customers quickly and on time."




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