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" Alaska Airlines Flight 75 from Seattle was about 30 minutes from Juneau when the pilots heard from the control tower: The airport was fogged in, and visibility was less than 400 ft. In that kind of late February weather, the crew normally would divert rather than try to land at an airport ringed by 2200-ft. mountains and buffeted by winds from the Gastineau Channel. Instead, the Boeing 737-400 stayed on course. A global positioning satellite (GPS) relayed real-time information about the plane&amp;#039;s location to the cockpit&amp;#039;s situational display, which cut through the gloom and put the aircraft on a flight path up the channel, between mountains that the pilots couldn&amp;#039;t even see. It was one of around 1000 flights that Alaska Air rescued last year from typical foul-weather fates: a long delay, cancellation or diversion. Those completed flights added millions to the airline&amp;#039;s bottom line, but the new flight-saving hardware may have an even greater impact than increased profits. The Federal Aviation Administration (FAA) has been quietly using Alaska as a testbed for technologies that could radically transform the nation&amp;#039;s antiquated air traffic control (ATC) system from ground-based radar to space-based GPS. It&amp;#039;s part of an overhaul called NextGen -- and it&amp;#039;s long overdue. Last year was the most delay-filled on record; 2007 looks like it will be worse. &amp;quot;The current system cannot handle the projected traffic demands expected by 2015,&amp;quot; Robert Sturgell, the FAA&amp;#039;s deputy administrator, told the Senate Committee on Commerce, Science and Transportation in March 2007. &amp;quot;Absent modernization, the consequences will be a total system collapse.&amp;quot; Sky Highways  Currently, a plane is guided to its destination via a series of radar handoffs. The relay starts with the control tower at the departure airport and continues through one or more of the 22 regional en route control centers that track flights at 18,000 ft. and above. It ends with the tower at the destination airport guiding the plane in for a landing. With today&amp;#039;s radar, it can take up to 36 seconds to get an accurate read on a plane&amp;#039;s position -- a long time for an aircraft flying 500 mph. So safety buffers err on the conservative side: The minimum distance between planes is 5 miles horizontally and about 3 miles on landing and approach. The result is inefficient use of airports and airspace. Another consequence of safety spacing: Air traffic control requires pilots to stick to a series of highways in the sky, a three-dimensional web of flight paths that keeps planes separated both horizontally and vertically but rarely represents the most direct route. A navigational chart looks a lot like an interstate map, with access roads feeding into expressways at higher altitudes. But unlike motorists, commercial pilots have to file a plan and stick to it, unless authorized by an air traffic controller to switch course. So, in many cases pilots can&amp;#039;t take the most direct route or dodge traffic snarls, which leads to more congestion. Real-Time Surveillance  NextGen is designed to change all that by providing air traffic controllers and pilots with much more accurate and detailed real-time information, which will help keep aircraft safely separated in the sky and on runways. Instead of radar, the new system relies on ADS-B, or automatic dependent surveillance-broadcast. It goes beyond the technology used by Alaska Air, Required Navigation Performance, which provides surveillance mainly for approach and departure paths within a few miles of the airport. An aircraft equipped with ADS-B receives GPS signals via an on-board receiver to determine its position in the sky. That information, plus data on the plane&amp;#039;s identity, position, speed and intended flight path, is broadcast to other aircraft and ground stations within 150 miles. For the first time, both pilots and controllers will see the same real-time displays of air traffic. Planes will be able to fly closer without jeopardizing safety, so more flights can be scheduled, easing congestion. Pilots will have greater flexibility to leave the aerial expressways and go &amp;quot;off-road,&amp;quot; flying more directly between two points because they&amp;#039;ll see surrounding traffic with far greater accuracy. This procedure is known as self-separation, because it transfers to pilots some of the responsibility for deciding how close they can safely fly to other aircraft -- a task now handled by air traffic controllers. As one retired controller says, &amp;quot;They won&amp;#039;t have to ask, `Mother, may I?&amp;#039; as often.&amp;quot;  Getting Airborne  The Aviation industry has talked about ADS-B for at least a decade. Skeptics note that the funding for the project is far from assured; many airlines, burned by the failure of past FAA modernization projects, are leery of buying new equipment before they&amp;#039;re sure of the government&amp;#039;s commitment. A breakthrough, however, appears to be imminent. In August, the federal government is expected to greenlight the program, which could ultimately cost between $30 and $40 billion; the tab will be split about evenly with private industry. The government has proposed shifting more air traffic control expenses from airlines to general aviation pilots. Two options: Triple the fuel tax on small plane operators; or charge a per-flight fee of $25. Private pilots protest vigorously that airlines benefit most from the system, and thus should shoulder most of the costs. Small plane operators argue they don&amp;#039;t generally fly to large airports, and they require far less attention from air traffic control. (Many don&amp;#039;t fly instrument flight rules or file flight plans.) At press time, Congress was debating the final form of funding. As the first phase, the government plans to award $1 billion this summer to a major contractor -- ITT Corp., Lockheed Martin or Raytheon -- to design the infrastructure that will eventually replace the nation&amp;#039;s 380 or so vintage radar towers. (Some will be kept for backup in case satellite transmissions fail.) In their place will rise a parallel web of sensors, each about the size of a minifridge and packed with devices to track planes at all phases of flight across the country. At some point, the FAA will require that airplanes flying under air traffic control be equipped with the avionics to make the system work. The transition will be gradual -- but, by 2025, the FAA expects the entire country to be on the new network. Early Adopters  Several airlines aren&amp;#039;t waiting for government action: Cargo carrier UPS Airlines has already equipped nearly 300 of its planes and its main airport hub in Louisville, Ky., with ADS-B technology. &amp;quot;It allows us to do simultaneous approaches to parallel runways, which we couldn&amp;#039;t do with existing surveillance,&amp;quot; says UPS director of operations Karen Lee. &amp;quot;It leaps the old technology by 15 generations.&amp;quot; By shortening flight times and using more efficient approach paths, UPS expects to save about 800,000 gallons of fuel annually. Next year, Southwest will install a system similar to that used by Alaska Air. Southwest is forecasting big fuel savings when it re-equips its fleet of 520 737s next year, because pilots will be able to throttle down to near idle power during a constant descent, staying a specific distance behind the plane ahead in what UPS&amp;#039;s Lee describes as &amp;quot;beads on a string.&amp;quot; At a busy airport with ADS-B, the landing capacity for a single runway could increase by 25 percent, handling a plane every 45 seconds. To passengers sitting on the tarmac this summer, delayed yet again, that day can&amp;#039;t come too soon.  Day in, day out, New York&amp;#039;s JFK Airport handles nearly a flight per minute. (Photograph by Adam Nadel/Polaris) "^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.popularmechanics.com/flight/a1936/4219569/>