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Originally published January 10, 2007 at 12:00 AM | Page modified January 10, 2007 at 9:40 AM

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Sea-Tac radar "ghosts" prompt warnings

After repeated safety warnings from air-traffic controllers, Federal Aviation Administration officials said Tuesday they will upgrade software...

Seattle Times aerospace reporter

After repeated safety warnings from air-traffic controllers, Federal Aviation Administration officials said Tuesday they will upgrade software to combat "ghost" radar images that can confuse the people guiding airplanes to and from Sea-Tac International Airport.

Controllers complain that recurring "false targets" on the radar system sometimes force them to redirect planes to avoid what looks like an impending collision with one of these ghost aircraft.

In one of many reports filed with the FAA since November, National Air Traffic Controllers Association union representative Dan Olsen wrote that the malfunctions were "extremely dangerous and stressful on the controllers. ... Fix the radar before someone is killed."

The FAA, while acknowledging the need for improved software that's scheduled to be installed at month's end, denies there's a safety issue.

"If at any point it's determined the system is uncertifiable or unsafe, we take that system out of service," Dave Adams, the FAA's district manager, said Tuesday in an interview.

The controllers' union is at loggerheads with the FAA over pay, staffing and other contract issues, and has worked since September under a contract imposed by the agency.

Several experienced controllers said that while Olsen's language may be overheated or even alarmist, the radar concerns he is raising are valid and many false targets show up daily.

"I can understand Dan putting it that way and applying pressure. Things don't get fixed until something happens," said Tony Haynes, a senior controller at Sea-Tac who is not a union member. "In a worst-case scenario, his concerns are correct. Yes, it can kill people in a worst-case scenario."

Olsen is not impressed by the FAA's proposed software patch, saying it won't fix the problem.

And he suggests that other unrelated recent radar failures — including a major one on Nov. 6 that caused numerous flight delays and cancellations at Sea-Tac — point to wider problems in FAA oversight.

Controlling air traffic


The radar system in question, at the Terminal Radar Approach Control (TRACON) facility, controls planes within a 40-mile radius of Sea-Tac.

The TRACON facility is beside the third runway under construction at Sea-Tac and is fed data by a 200-foot-tall square radar tower nearby.

Inside is the control room, perhaps 10 yards wide and 30 yards long, dark except for the cold light from dozens of high-tech computer consoles and flat-panel display screens.

During a recent visit, around a dozen controllers sit around the periphery. Their screens all display a map of Puget Sound with radar blips showing the airplanes in the air.

Each controller directs specific airplanes in or out of local airports. Some handle arrivals, some departures; some are looking at a corridor to the east, some to the west. In the middle of the room, various supervisors man stations to watch the overall picture.

As weather and circumstances change, Traffic Management Coordinator Haynes adjusts the flow of airplanes in and out of the region. Typically, the center handles 60 to 70 aircraft in or out in an hour.

A large flat-panel screen shows all the airplanes in the air over Washington, color-coded by size. Big jets will take just 20 minutes to pass over the state and get to Seattle.

Haynes twiddles the display and now it shows all aircraft in flight over the United States — 2,352 one late afternoon in November.

Sitting down at a console, Olsen shows how the system looks to a controller. Electronic tags beside each radar blip provide detailed information beamed from the transponder in the aircraft's nose: Alaska Airlines, flight 582, a Boeing 737, is at 9,000 feet, moving at 290 knots (nautical miles per hour).

"Everything happens in our airspace very fast," he said. "All the aircraft are doing about 250 knots and you have only 40 miles to get them in line."

When two jets are heading toward each other, "You're looking at 570 miles per hour closure. ... If we get a false target projected, we have to scramble to separate."

After a few moments, he points to a "false target." How does he know it's false? "We don't get traffic over there," he said. "See how he disappeared."

The false targets are usually reflections of other aircraft already on the screen. The computer system recognizes the duplication and so displays only a bare target with an altitude and speed but without the identifying information on airline, aircraft and flight number.

But Olsen said that under unusual circumstances that information could be missing from the radar feed off a real aircraft. So the rule is, if a target shows up, a controller must direct traffic to avoid it.

"I'm issuing traffic [instructions], sometimes making turns," Olsen said. "And that's a very high-stress issue because some of them look like they are going to hit."

"That's very distracting," Olsen said. "It's so common, you're having people starting to just ignore it, which is scary. We shouldn't be ignoring anything."

Controllers can push a button to record and document anomalies when they occur. Olsen showed more than 60 such "discrepancy reports" from November and 29 more filed in December. He also showed copies of more detailed "unsatisfactory condition reports" (UCRs) he'd filed complaining about five different false-target incidents affecting flights on a single day in November.

But that's only a portion of the total, he said. He makes a point of recording discrepancies and in flurries follows up with UCRs; some controllers don't.

"You get tired of doing this," he said. "There's not enough hours in the day to keep up."

TRACON facility acting manager Steve Atkinson said all radar systems show some false targets. The problem is tuning the system to eliminate as much clutter as possible — a sensitive system might display a big truck moving over the floating bridge — without blocking out any real aircraft.

Still, the FAA decided Monday to accelerate a planned adjustment of the Seattle TRACON radar system. At month's end, the agency will install a software revision to prevent any target from showing on the radar scope if it registers only a single radar hit. That means a reflection would have to persist beyond one radar sweep to register in the system.

"If it happens a single time, it won't appear," Atkinson said. "If it happens more than once, this revision won't fix that."

Olsen responded that though the software revision "might fix a few" of the false targets, an internal FAA evaluation by specialists in the software has already indicated it won't eliminate most of them. The issue is a basic radar issue rather than a software problem, he said.

Problems cause delays

The radar system has had other recent problems, too. TRACON was closed for a day in the December windstorm due to a power outage. In response, police rushed two TRACON controllers down to the regional Air Route Traffic Control Center (ARTCC) in Auburn, which normally manages planes only after they've left Seattle airspace.

And that widely publicized glitch followed one that escaped attention earlier but caused far worse delays.

On Monday, Nov. 6, it rained very heavily at Sea-Tac, and water leaked into the radar antenna cable at TRACON. Separately, an oil cooling system on the radar tower failed. The upshot was that the system lost three of its four radar feeds, forcing controllers to slow down the plane traffic and causing long delays and canceled flights.

FlightStats, a company that compiles real-time commercial aviation data, found that among the nation's top 30 airports, Sea-Tac that day ranked dead last in performance by a wide margin. Only 26 percent of scheduled arrivals were on time, 81 flights were canceled, and more than 400 flights were delayed by more than 45 minutes.

The loss of that last radar feed would have forced the closure of TRACON and a shift of all responsibility to ARTCC, which would have slowed air traffic in the region even more.

Haynes, the traffic management coordinator who worked for many years as a controller in Dallas before coming to TRACON two years ago, said it's "very rare" to get two such incidents in a short period.

"I'm amazed how few redundancies we have compared to that facility in Dallas," he said.

The FAA says the Nov. 6 episode was a one-time event, and its contingency plan for the problem worked.

For Olsen, though, it's another symptom of the agency's cost-cutting.

"The way the FAA has decided to manage this is, until it's broken, don't fix it," he said, "They're trying to save money."

Dominic Gates: 206-464-2963 or

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