All flights begin not with a takeoff, but with a slow taxi across the tarmac. At Washington Reagan National Airport, for example, jets taxi from the terminal to the runway, within sight of the Washington Monument. As at any other major airport, pilots here complete their earth-bound maneuvers only when they're told to, by someone watching them from up in the control tower.
In the tower, a controller looks through enormous, wrap-around windows to make sure no one's coming or going on the three busy runways.
Maneuvering planes from the gate to the runway seems like the simplest part of the flight. And for the passenger, the least nerve-wracking.
"In reality, I have never met a white-knuckle taxier," says Mark Rosenker, head of the National Transportation Safety Board. He says the slow, simple ground maneuvers are more dangerous than they look.
"I believe that's where the greatest potential for catastrophic accidents can occur right now. We've had too many close calls. And it's just by sheer luck and tremendous airmanship that we have averted a catastrophic collision."
Actual collisions on the ground are rare, and incident rates are lower than a few years ago. But federal records since 2001 show that dozens of near-misses still occur each year at U.S. airports. Within the past nine months there were close calls at J.F.K., Boston-Logan, Fort Lauderdale, and Chicago. The Chicago-Midway incident began with a controller's instructions to a United Airlines jet.
The United pilot was told to wait at the end of his runway until cleared for takeoff. Also waiting was a Southwest Airlines jet, sitting across the airfield on an intersecting runway. The controller gave Southwest the go-ahead. But the United pilot thought that was for him, and accelerated down his runway on a collision course. A second controller eventually noticed.
An order for the United jet to stop came just in time. If not, a collision might have echoed the Tenerife runway nightmare of 1977. NTSB chair David Rosenker says of that catastrophe: "The worst air disaster in the history of aviation was on the Canary Islands, where two aircraft collided and 583 people died."
To prevent such a tragedy, ground radar systems have since been installed at major U.S. airports, including Reagan National. Chris Stephenson, a controller there, says, "A ground radar system gives us a radar display of aircraft and vehicles that are on the airport surface area. It's a tool to control traffic as well as a backup."
But he says the technology has a major flaw. "The big killer on it is when it rains, you have to turn it off. And the time that we really need this is during periods of reduced visibility."
So the F.A.A. developed an upgrade known as Airport Surface Detection Equipment Model X, otherwise called ASDE-X. It's been tested at a handful of airports, including at Providence, Rhode Island. Controller Bruce Miller in Providence says this new technology is vital because the fog that regularly rolls in nearly led to a fatal runway collision there a few years ago. "ASDE-X is a very good tool, and what it does is it gives us eyes through weather conditions that we would normally not be able to see the aircraft. I wouldn't want to work without it, to be honest with you."
ASDE-X alerts Miller whenever planes appear to be headed for a collision. But NTSB Acting Chairman Rosenker says those alerts should go directly to pilots, giving them crucial seconds they might need to act quickly.
Still, he thinks ASDE-X is a good step by the FAA, if only a small one. "I would give them a B-minus. And when they finally get to these developments that... communicate directly to the cockpit, I will give them an A-plus."
FAA Chief Operating Officer Russ Chew says the new system will eventually lead to what the NTSB is asking for.
"ASDE-X is a digitally based system. The flow of digital information can allow us to start to move that information out of that system to other places, such as the airplane, should it be in the future equipped to receive it."
A ground radar system that communicates directly to pilots is in development, but years away from use. Until then, the time spent taxiing will remain one of the more dangerous parts of air travel.
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