THE AEROMEXICO DISASTER : Sky Too Crowded to Track Small Planes, Controllers Say

On a clear day, especially a holiday, the skies over Southern California are crowded with so many planes, says air traffic controller Kathy Heet, that her radar screen is “covered with them.”

“You see airplanes all over the scope because everybody and their brother is flying,” says Heet, a controller stationed at the Federal Aviation Administration’s facility in Palmdale.

But the density of the air traffic is only one problem facing both pilots and controllers in the Los Angeles area, according to Heet and Dennis Cottle, one of her co-workers, who discussed their work in the aftermath of Sunday’s collision over Cerritos.

“Even if you see every plane up there . . . you can’t track every one,” Heet said. “It’s impossible. . . . But there are also plenty of planes that we’re not seeing. They’re not showing up on our screens at all.”

Cottle says many planes are not equipped with transponders, the electronic device that transmits information about an aircraft’s location to radar facilities. “It’s almost impossible to see an airplane not equipped with a transponder,” Cottle said, “but even having one doesn’t solve the problem. There are many planes out there with broken transponders. It’s a $700 job to fix them, and a lot of pilots put off getting them repaired. And even planes equipped with transponders don’t always send out altitude data.”

For example, National Transportation Safety Board officials said Monday that the transponder on the single-engine plane that collided with an Aeromexico DC-9 on Sunday was not reporting the aircraft’s altitude. Safety board officials said this means it was very unlikely that air traffic controllers could have successfully tracked the path of the small plane.

Meanwhile, Cottle says controllers often miss the presence of a small plane because it is located in a radar “blind spot” caused by a hill, or by an antenna turned the wrong way.

“There’s lots of chances to miss it (the plane),” Cottle said. “It happens all the time.

“Sometimes you see it (a small plane) but the pilot in the big jet says he can’t see it, and they come together (on the radar screen), and you cringe. You hope that there are two targets (blips) on your radar screen when it’s over. That happens to controllers every day.”

In the Los Angeles area, aircraft are first monitored by air traffic controllers at FAA facilities in Palmdale. As they enter the landing pattern for Los Angeles International Airport, the controllers in Palmdale “hand off” planes to controllers in an FAA facility at El Toro. In turn, the planes are then “handed off” to so-called “Los Angeles Approach” controllers stationed at Los Angeles International Airport.

Each group of controllers tries to warn pilots when their aircraft are coming too close.

Cottle is a former pilot for Southeast Airlines who moved to California from New York to take the air traffic controller job five years ago.

“Numerous times we’ve heard (airliner) pilots say, ‘Hey, did you see that? We just had to bank to avoid another airplane, and we didn’t see them.’ And although controllers were supposed to see the small guy, we didn’t. There was no image on our scopes,” Cottle said.

“Some targets (radar blips) show an altitude, and others don’t. Sometimes we get false targets. . . . Airborne collision-avoidance equipment is the only way to go, because air traffic control simply can’t separate all the aircraft.

“It’s unfortunate that this (a major crash) has to happen, but by the law of percentages, it does have to happen.”

(Two collision-avoidance systems are currently being tested, but both are years away from widespread deployment. One system, under study by Piedmont Airlines, employs ground radar that analyzes the course and altitude of each plane that it picks up and transmits the information to all other planes operating in the same system.

(Another technique being developed for the Navy employs radar, a transmitter and minicomputer aboard each plane. The transmitter sends out a signal, the on-board radar listens for the echo, and the computer calculates whether a collision is imminent.)

Near Crowded Level

Cottle said that the altitude of Saturday’s collision, 6,000 to 7,000 feet, is just below the most crowded level in the skies.

“Between 7,000 and 18,000 feet . . . any plane that wants to be there can be there . . . you end up moving out of the way a lot. Small planes often want to skirt the terminal control area about 500 feet above the 7,000-foot level, and laterally just outside it. And as a pilot myself, I know that’s the altitude where you’re most likely to encounter another plane.”

The terminal control area is airspace reserved for aircraft that have permission from controllers to be there, Cottle said.

He said he has had to divert his own small airplane to avoid collisions about 20 times since moving to California, something he only did once while a pilot for eight years on the East Coast.

In most situations, he said, the pilot of the other aircraft “never saw me.”

“It’s a lot more crowded here,” he said. “I can’t believe how bad it is compared to even the area around New York City. There’s just a lot more traffic here.”

Close Call With Jetliner

Cottle recalls that he once had to swerve sharply to avoid a United Airlines jet that had just departed from Santa Barbara Municipal Airport. “The United pilot did see me on that one, because he swerved too.”

Cottle says he complains to air traffic controllers about such incidents, but he doesn’t go to higher authorities.

“I don’t want to get another controller in trouble,” Cottle explained. “As long as they know there was a problem, that’s enough for me.”

Heet agreed that not being able to see a light plane on radar is a “frequent problem.”

Heet said she has often seen light planes go into prohibited air space.

“I think they’re crazy,” she said. “Sometimes they’ll be tracked to an airport and somebody will talk to them there. Sometimes they get written up and admonished, but often times nobody does anything about it.”

John Mazur, Washington-based spokesman for the Air Line Pilots Assn., said Monday that he would not comment on the frequency of near-misses over Southern California because “this leads to speculation and new headlines in each day’s paper about the cause of the crash.”

Mazur said he did not believe Mexican pilots belong to his group, but instead have their own association. Mazur added that agreements between American and Mexican pilots about safety procedures occur only on an “ad hoc basis.”