With commercial airline traffic expected to top one billion passengers annually by 2016 (compared with the 769 million who flew in 2007), there are more aircraft than ever taxiing, taking off and landing on airport runways. All of this airfield congestion requires technology that can monitor what is happening at the dizzying pace it is occurring, and radar, a World War II–era invention, is not up to the task.

Recognizing this, the U.S. Federal Aviation Administration (FAA) last week announced it will pay Morristown, N.J.–based manufacturer Honeywell International, Inc., and Aviation Communications & Surveillance Systems (ACSS) in Phoenix $9 million to test and install satellite-based ADS–B (automated dependent surveillance–broadcast) systems to help improve runway safety.

ADS–B—first conceived in the early 1990s by the FAA and a variety of government agencies and businesses that build and/or rely heavily on airplanes, including NASA and delivery giant United Parcel Service (UPS)—relies on the proactive communication between global positioning system (GPS) satellites and transponders placed on board aircraft to inform pilots, other aircraft and air traffic controllers about an aircraft's location, identity, speed and altitude. Whereas ADS–B is continuously collecting and transmitting information, radar emits electromagnetic waves at regular intervals—every 12 seconds or so—and measures the time it takes for their reflection to return to determine the proximity of objects to an aircraft.

"(ADS–B is) more active, rather than passive," says Terry von Thaden, assistant professor of human factors in the Institute of Aviation at the University of Illinois at Urbana–Champaign. "Radar's considered passive. ADS–B doesn't have to wait for the radar to sweep and sort of mosey along."

Although ADS–B—designed to be a replacement for radar—can be used in to coordinate aircraft position in flight, the Honeywell and ACSS contracts are designed specifically to improve runway safety. Honeywell will test the technology in two of its planes as well as install ADS–B systems in JetBlue Airways and Alaska Airlines aircraft for pilots from those companies to evaluate. Honeywell will work at Seattle–Tacoma International and Snohomish County Paine Field airports. ACSS will work at Philadelphia International Airport with US Airways to develop standards, flight demonstrations and prototypes of the technology, equipping 20 Airbus A330 aircraft with ADS–B systems.

With radar, pilots rely on air traffic controllers and a see-and-avoid strategy that literally entails looking out the window to avoid wandering in the way of—or colliding with—other aircraft on the runways. With ADS–B, pilots have a cockpit display, which looks like a full-color, topographical map on a computer screen, showing where they are, where everyone else is, and the ever-changing weather around them. "It's giving the pilot an extra set of eyes," says von Thaden, who is also a licensed pilot.

ADS–B's ability to update in real-time is especially important on runways, with so many planes in such close proximity. "Things happen a lot faster on the surface," says Vincent Capezzuto, the FAA program manager for ADS–B. "There are aircraft speeding up to take off. There are aircraft that are landing and going really fast and decelerating and taking sharp turns onto these high-speed taxiways to get off the runway."

After years of research and development, and tests by general aviation pilots in Alaska and air transport carriers in the Ohio River Valley, the FAA in 2005 declared ADS–B to be a safe radar alternative and pegged the technology as a crucial component of the agency's plans to by 2020 upgrade the national airspace system—a program known as Next-Generation Air Transportation System.

NextGen is the far-ranging plan the FAA developed in conjunction with the U.S. Department of Homeland Security, the White House Office of Science and Technology Policy and others.

The technology tested well in Alaska, where the harsh landscape makes it difficult to implement a radar infrastructure (including towers and other equipment). "Ninety percent of Alaska has no radar coverage," says Wilfred Ryan, president of the Alaska Air Carriers Association, which promotes Alaska's commercial airline interests. "ADS–B brings a radarlike environment to places where radar is too expensive to install." Alaska had the nation's worst airline accident rate in 1991, Ryan notes. Because of this accident rate, the FAA selected Alaska's commercial airlines to participate in the Capstone Program, a 1999 to 2006 joint venture between industry and the FAA that provided Alaskan aircraft with ADS–B systems for free. During Capstone, accidents decreased by 47 percent.

ADS–B is also expected to increase airline efficiency and help the environment. In weekly experimental flights, UPS, which helped develop ADS–B, has already seen the benefits. At its Worldport hub in Louisville, Ky., the company handles more than 100 flights—most during a four-hour window from 11 P.M. to 3 A.M. With ADS–B, spokesman Mike Mangeot says, UPS could increase that traffic, and therefore the number of packages it delivers, by as much as 15 percent. Additionally, by enabling more tightly spaced landings, and less time in holding patterns, ADS–B saves 40 to 70 gallons (150 to 265 liters) of fuel per landing. Mangeot estimates that the Continuous Descent Approach enabled by ADS–B, during which aircraft glide in with their engines at idle thrust, cut nitrous oxide emissions (a greenhouse gas) by about 34 percent as well as noise pollution by some 30 percent.

Perhaps the biggest sticking point for ADS–B, like any new technology, is its cost. According to FAA spokesman Paul Takemoto, the agency estimates that the NextGen infrastructure will cost from $15 billion to $22 billion to construct—it is unclear exactly how much of this price tag includes the cost to equip aircraft with ADS–B. The FAA wants to make a standardized version of ADS–B that can be brought to market by a number of different manufacturers, a move that Capezzuto says will drive the cost down for aircraft manufacturers. He adds, "The idea is to make it available as fast as we can.”

2 Comments

1. 1. GetTheFlick 08:06 AM 11/15/08

   How disappointing to see such an article in SciAm. ADS-B, while an interesting technology, cannot and will not replace radar. An event where the data is available to the public -- to demonstrate the gaps in the technology -- is the events of 9/11. The hijackers turned off their transponders to confuse ATC. However, radar (where it was available) was still be able to track the traffic. ADS-B, on the other hand, would not. If the pilot turns off the device, the aircraft disappears from the controller's scope. Think electrical failure -- which, unlike a terrorist attack, happens every day in the National Airspace System (NAS).
   
   The exceptions to the NAS are always used to justify ADS-B. ADS-B looks good in the Alaskan bush because there isn't any infrastructure to speak of. In the busy areas of the NAS -- with a lot of infrastructure -- ADS-B doesn't hold nearly as much promise. UPS flies out of an obscure airport (Louisville, KY) on the midnight shift when they are virtually alone in the sky. Continuous Descent Approaches don't work during the normal work day when the traffic increases and multiple airports are in heavy use -- like in New York with JFK, EWR and LGA.
   
   And finally, the real fallacy -- "enabling more tightly spaced landings". The limiting factor is spacing arrivals is wake turbulence. ADS-B will not eliminate the distance needed to safely avoid wake turbulence. And radar is more than adequate to provide that type of separation.
   
   Again, ADS-B (and the FAA's "NextGen" system as a whole) does provide some interesting solutions to some limited problems. The question is whether or not it is worth the cost. ADS-B does not replace the National Security functions of radar. (FAA radar sites are joint use facilities with the Department of Defense.) Therefore, we would have to pay for both -- radar and ADS-B.
   
   All this doesn't mean that we shouldn't pursue ADS-B. It's just important to know the truth in order to make an informed decision. This is "preaching to the choir" at SciAm. Unfortunately, in this case, I feel compelled to do so.
   
   Don Brown
   Retired Air Traffic Controller
   http://gettheflick.blogspot.com/

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2. 2. jtormey3 12:19 AM 11/16/08

   Saturday, November 16, 2008
   
   Do You Speak EEL?:
   http://removesturgell.blogspot.com/2008/11/do-you-speak-eel-translating-faa-bobby.html
   
   Blue-Ice Sturgell: A Hard Rains A-Gonna Fall:
   http://removesturgell.blogspot.com/2008/11/bobby-sturgell-failed-faa-head-hard.html
   
   Malaysian Fatwa Bans FAA Management:
   http://removesturgell.blogspot.com/2008/11/malaysian-fatwa-bans-faa-management.html
   
   http://www.bobbysturgell.com
   http://www.bobbysturgell.net
   http://www.bobbysturgell.org
   

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