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ATC UpdateATC Update

A day in the ATC trenchesA day in the ATC trenches

My last visit to an air route traffic control center (ARTCC) was in 1981, while doing research on a story about the effects of the Patco (Professional Air Traffic Controllers Organization) strike and subsequent mass firing of controllers. That's a long time ago, and much has happened in air traffic control in the intervening years. Because it's always educational to periodically visit a center or tower — and because I'd been away so long — I spent a day at the Washington ARTCC in Leesburg, Virginia. Then I stopped by the tower facilities at nearby Washington Dulles International Airport to see how things had changed there.

Action central

At first glance, Washington Center's inner sanctum doesn't appear to have changed much at all in the past 10 years. The huge, darkened room is still there, with the same two corridors lined with radarscopes. Those scopes haven't changed, either. They're vintage, 20-year-old sets that are the workhorses of the controller's trade.

New to the scene, however, are large color monitors that continually display weather maps and other meteorological information. These monitors are installed in the center of the aisles, near supervisor stations — more about these later.

Another immediately evident change is the composition of the controller work force. Compared to the pre-strike days, controllers are younger and tend to be unaffiliated with organized labor. There are more women controllers, too. About 15 percent of Washington Center's 400 controllers are women, compared to a small handful before the strike.

Is the new breed of controller as sharp as the pre-strike force? According to one traffic supervisor, who preferred anonymity, "There's something to be said for age and experience, but there's also something to be said for youth and speed. And this is a fast-paced job. By the time we go through our four-year preparation for full-performance-level duty, we're more than up to the challenge."

That challenge — keeping up with a burgeoning load of IFR traffic — is being met more and more aggressively these days with the help of some new procedures and new technology. One big help is the center's traffic management unit, or TMU. The TMU is a three- or four-man group set up in an enclave separate from the bulk of the controller work stations.

The TMU's job — ensuring in-trail traffic separation of high- altitude traffic — combines anticipation of localized traffic jams at peak hours with nationwide coordination of traffic flows through ATC's central flow control facility at the Federal Aviation Administration's Washington, D.C., headquarters. Take the daily morning and evening rush hours, add in the fact that each center experiences them, and throw in weather-induced delays, and it's easy to see that each center's TMU has its work cut out.

The TMU concept came about in the late 1970s, but it's only since 1990 that Washington Center has been able to take full advantage of the idea. That's when new software permitted the installation of aircraft situation displays (ASDs) at the TMU stations.

The ASD screens give TMU staffers a quick, easy-to-comprehend picture of traffic conditions. The day I was there, the ASD screen was alive with white, purple, green, blue, yellow, and red dots — all of them showing airplanes tracking various airways and jet routes. These particular dots showed the traffic flows all up and down the Boston- Washington corridor.

Bill Pearman, the supervisor of traffic management that day, said that the ASD makes all the difference in the world. "What this does is tell us quickly what will happen in two hours — before these airplanes arrive in Washington Center airspace. Sure, the controllers receive hand- offs and can tell by their data strips who's going where. But they can't get the big picture," said Pearman. "That's our job."

Pearman explained the meaning of the dots' colors: White means an arrival at Washington National; purple means a Charlottesville-Albemarle arrival; green, Baltimore-Washington International; blue, Dulles; yellow, Orlando International; and red, Miami International. "By watching what happens here, we can alert controllers to potential traffic conflicts long before they become immediate problems," Pearman boasted. "And it's not just for traffic in Washington Center. We can call up the same type of display for any route affecting the United States."

I asked if this applied to overseas arrivals, and Pearman started punching buttons. Soon, a display of North Atlantic routes was on the screen, filled with lines of colored dots. In one concise vision, it showed all the traffic over the ocean, together with their destinations.

Safe separation — 5 miles horizontally and 1,000 feet vertically — remains the watchword at every ATC facility. The TMU and each controller's proficiency help guarantee that, but to give teeth to the marching orders is the "snitch patch," a system that automatically detects violation of separation standards and identifies those controllers who let airplanes get too close. Bluntly speaking, the snitch patch rats on controllers.

It's a system that's been around since the early 1980s and the subject of controversy. Critics have said that there's been overeager use of the snitch patch as an instrument of punishment in some centers. In times of great traffic saturation, many controllers argue, it can be difficult to manage a heavy flow of traffic without a rare, inadvertent violation of separation standards.

And saturation has been a nationwide problem. "I wouldn't say that the system is hopelessly saturated," Pearman says, "but it needs constant surveillance. Our peak times are Wednesday and Thursday afternoons — that's when we have the most volume in the sky."

When that happens, readouts at the center's watch desk can show the ATC computers reaching maximum capacity. Pearman said he's seen the readouts go as high as 85 to 91 percent of capacity. At times like these, a priority list designed to shed the least necessary data takes over. The objective is to regain or preserve computer storage space and memory. Precipitation returns are eliminated from controllers' screens, for example, as are approach control boundaries. Any scopes not being used are turned down.

Of course, the saturation problem isn't a new one. It's been around since the mid-1960s. When asked what general aviation pilots on instrument flight plans could do to help reduce saturation and prevent potential traffic conflicts, Pearman offered the following advice:

  • If a frequency is busy, keep transmissions and requests to a minimum.
  • Give as much advance notice of desired route changes as possible.
  • For example, a three-minute advance warning gives very little time to correctly process and coordinate altitude or route changes.
  • Use published preferred routes as much as possible.

When asked about flying direct, controllers explain that oftentimes jurisdictional boundaries, letters of agreement assigning various tasks between centers (and sectors within centers), and preferred routings can create conflicts that are difficult to resolve. "You may ask to fly into an area that an adjoining center is using as a departure or arrival corridor," one controller said. "So it may be impossible to comply with a request for a direct routing.

"Still, we try our best to let pilots fly direct as much as possible."

Center weather

Ever since 1978, each ARTCC has had a center weather service unit (CWSU) attached to it. The intent was to have a full-time, resident staff of meteorologists capable of providing controllers with near-real-time weather reports and forecasts. Since their inception, CWSUs have increased in efficiency and capability. In fact, their refinements appear to have surpassed those of the separation and surveillance portion of the FAA's modernization plan.

Meteorologist Carl Ewald showed me around Washington Center's four-man CWSU. The latest additions to the unit have been the meteorological weather processor, or MWP, and a WSR-88D Doppler weather radar capability.

A half-dozen video terminals grace the unit. Most are connected to feeds from the National Weather Service and show such things as satellite and radar imagery, charts showing pressure and wind patterns, and severe weather watch and warning areas. Two terminals are connected to the Doppler weather radar site in nearby Sterling, Virginia.

The MWP equipment was installed at Washington Center — and many others — in September 1991, and it's been a godsend for center meteorologists. Before the MWP, meteorologists had to rely on facsimile charts and reams of printed reports and forecasts. Many times, they had to create their own charts in an ordeal that could take up to 50 minutes to plot data, then another 10 minutes to analyze it and create usable reports and graphics. Now, it takes just two clicks of a mouse and 20 minutes to generate charts of vastly higher quality.

As for the Doppler radar, it's been available to Washington Center since December 1991. It's still in the experimental stage, though staffers use it for advisories in the immediate area. Its nominal range is 120 nautical miles or so, though it is capable of detecting cloud tops greater than 30,000 feet some 250 nm away. Because of this new WSR-88D Doppler radar's limited range, experimental status, and frequent outages, the nation's aging network of WSR-57 weather radars is still the official source of radar imagery.

All these tools help center meteorologists create their two principal products with much greater speed and accuracy. Besides a minimum of two daily (8 a.m. and 4 p.m.) stand-up briefings to controllers and their supervisors, the meteorologists must prepare center weather advisories (CWAs) and meteorological impact statements (MISs) as conditions dictate. On a convectively active day, there could be as many as 12 or more of these briefings and reports.

The CWA is a two-hour nowcast — a sort of weather howgozit for center airspace. The Doppler radar can come in very handy here, and the MWP's ability to produce custom products is a help, too. For example, cloud-to-ground lightning strokes can be superimposed on satellite imagery, along with constant pressure charts showing areas of maximum winds and their direction.

MISs are four- to 12-hour forecasts that are issued whenever sigmet criteria are reported or forecast in center airspace. These are primarily for planning purposes. A forecast of low IFR conditions with airport-closing potential, for example, will certainly catch the interest of TMU specialists. That's because they'll have to begin planning for diversions or reroutings.

By far, the most convenient aspect of the MWP setup is the ability to feed a constantly updated supply of weather graphics and other reports to the aisle-mounted video monitors mentioned earlier.

Before the MWP setup was complete, supervisors had to leave their posts and walk to the weather unit, located at the far end of the floor. There, they'd check the weather, do their best to remember the locations of the worst radar returns, then return to their controllers to give advice. With the aisle-mounted videos, all a controller or supervisor has to do is swivel his or her chair around for a weather update.

Which brings us to the next step in the ATC modernization plan. The 20-year-old scopes used by the controllers show precipitation returns, but their information is crude at best. Small "H" symbols mark areas of heavy precipitation; tiny slash marks denote lighter levels. There's no contouring of precipitation levels, a la weather radar, and poor delineation of radar echo boundaries. That's why controllers are not urged to give vectors around the weather appearing on their scopes.

Relying on radar data from the MWP video monitors is better, but there are two problems here. One is that the controller has to turn around, locate the echoes and contours, try to commit them to memory, then turn back around and attempt to superimpose the memorized position on the scope. The other is that the imagery on the MWP terminal may be up to four minutes old by the time it's broadcast. In a convective situation, a lot can happen in four minutes.

The solution is the integrated sector suite (ISS) concept. This will do away with the old scopes and install new ones with the ability to display both traffic and high-quality, WSR-88D Nexrad Doppler weather radar imagery. This program is due to be initiated in late 1994, beginning with Seattle Center. All centers are supposed to have the integrated suites six to eight months later. Once up and running, pilots can look forward to more accurate vectors around weather and safer instrument flying.

Calling on the tower

At Dulles, the approach control radar room sits one floor beneath the tower cab. And the approach control's acquisition of brand-new ASR-9 radars is the big news at Dulles. The old radars — ASR-4s — with their poor weather resolution and limited range — are long gone.

The ASR-9s can show both traffic and precipitation returns. Seven levels of radar reflectivity can be shown, and the update time of these radars is a sprightly 12 seconds. Thanks to this near-real-time feature, traffic can be given highly accurate vectors around mean-looking echoes.

The ASR-9 radar beam has a 60-nm range, and this has been a benefit, too. According to Dulles air traffic control supervisor Dan Laswell, this range increase means that hand-offs to and from Washington Center can be performed later (for departures) or sooner (for arrivals) than with the ASR-4s. This, in turn, means better coordination of departing and landing traffic.

Next on tap is terminal Doppler weather radar (TDWR). Like most other major airports, Dulles was due to receive its TDWR this year. But like so many other elements of the FAA's modernization plans, the schedule has slipped. TDWR is designed to scan the approach segments to runways. The major objective is to use Doppler's ability to detect microbursts and other dangerous wind shifts that may occur as airplanes descend to the runway threshold. Microbursts and wind shear can be easily seen on TDWR.

I earned my instrument rating through a Dulles-based flight school in the mid-1970s, and in those days, Dulles was an empty place. To keep their traffic count up, controllers would ask us if we wanted another practice ILS or an ASR approach or no-gyro vectors. You name it, they'd do it. We also used to park at the base of the tower and walk up the stairs for lunch at the tower's restaurant. For its monstrous size, Dulles was, well, practically asleep.

No more — now Dulles controllers have to contend with shoehorning in 45 arrivals per hour in instrument weather and 65 an hour when visual conditions prevail. For this reason, Dulles Approach is on the waiting list for an ASD of its own so that, like Washington Center, it can better plan for the press of rush hour. Dulles already has a TMU, which I'm sure was unnecessary in the days when I was learning to shoot approaches.

The day of my visit, the "Charlie gate" was giving Dulles controllers fits. The Charlie gate is a point to the northeast of the airport where departures from Dulles, Washington National, and Baltimore- Washington International all converge. Letters of agreement are supposed to ensure that there's adequate vertical separation over Charlie, but that day, there were two outbound aircraft from National that were too low. That meant Dulles controllers had to stop the climbs of two departures.

Meanwhile, a turboprop commuter on the ILS to Dulles' Runway 12 was ordered to stop its descent. The reason: An unidentified airplane had blundered into the Class B airspace without a clearance.

Laswell cites Class B violators as just one of the problems routinely faced by Dulles personnel. Others include pilots not filing preferred routes ("File for the preferred route, then ask for direct once you're up there," Laswell advises), long-winded initial call-ups, and pilot reluctance to use remote frequencies to open or close their flight plans.

The action came hot and heavy around 3 p.m., and I knew it was time to get out of the way. A huge combination of commuters and heavy jets was about to beset Dulles, and controller chatter picked up considerably.

I spotted a Mooney next to a 737 at the runup pad next to Runway 19L. A 747 touched down, and the 737 was cleared for takeoff. Another jumbo was over the outer marker, inbound.

"What are the chances of a single-engine airplane getting in here right now?" I asked tower controller Brenda Gross. "It's not a good idea," she deadpanned.


I came away from these visits with an image of a system caught in flux. New equipment promises greater safety and efficiency of traffic movements, but budgetary constraints and bureaucratic inertia will certainly delay implementation. And all the while, technological advances like GPS, satellite communications, and automatic dependent surveillance zoom forward in a frenzy of sophistication. The government moves ponderously, and quick changes to accommodate these advances are impossible.

In effect, we're stuck between the government's plans of a decade ago and the private sector's vision of a future that could happen now. Yes, the FAA has taken the first steps toward approval of GPS as a sole means of navigation. But as we've seen, the current system isn't ready for total reliance on satellite navigation. Until it makes ready, controllers will get along the best they can. Fortunately, improvements such as ASD, MWP, ISS, and TDWR will make their jobs — and our flying — easier in these transitional times.

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