475,000 Takeoffs and Landings a Year
The Summer Games will bring 4,000 additional aircraft to London's airports. Find out what it takes to keep Heathrow running smoothly on a normal day.
- By Michael Milstein
- Air & Space magazine, January 2007
(Page 2 of 5)
Heathrow has gone 34 years without a major accident. The last was a British European Airways Trident that crashed just after takeoff in 1972, killing all 118 aboard. It was the nation’s worst air disaster—that is, until the bombing of a Pan Am 747 over Lockerbie, Scotland, in 1988. Collisions have happened—on the ground. At least three times since 2004, airplanes jostling for position on busy taxiways have bumped wings or rudders. In 2005, the crew of a United Airlines 777 that struck an Air Jamaica A340 while heading for a takeoff holding spot suggested the Airbus was closer than it would be at other airports. But investigators said, “This was not considered unusual for Heathrow.”
One of the trade secrets of Heathrow’s air traffic controllers is that they don’t think about the people. They focus on the airplanes, because considering the hundreds inside every one—sipping their complementary sodas and worrying about their connections—would rapidly overwhelm anyone, says Mark Hewitt, a control tower supervisor.
A trick to making the most of Heathrow’s runways comes clear in the routing of inbound airliners. They go first to one of four beacons at each corner of the airport, where they circle in stacks—each one 1,000 feet above the other—waiting for controllers to direct them in. For passengers, it’s frustrating. For controllers, the stacks supply a constant reservoir of airplanes to put—rapid-fire—onto the pavement. The steady stream of airplanes from the stacks guarantees the runways never go idle.
Heathrow’s schedule is so full that if the runways stand empty for even a moment, millions of dollars’ worth of landing time will be lost.
“Once it’s gone, it’s gone, and you’ll have a delay through the rest of the day that you cannot recover from very easily,” says Martin Alder, a former air traffic controller and pilot who recently retired from flying British Airways 747s and A320s in and out of Heathrow. “The only way it can work to the levels it does is uniformity.”
The stacks also give controllers a choice of airplanes. A big 747 trails powerful tornado-like vortices from its wings, so a smaller Airbus A321 cannot follow as closely. Faster airplanes catch up to slower ones. Airliners flying against the wind touch down at a lower speed so they can turn off the runway faster. Controllers deal a landing lineup out of the stacks based on all these factors, packing airplanes as close as safely possible.
The dealing is done deep within a dull concrete building a few miles north of Heathrow, in a room the size of a small gymnasium, called the London Terminal Control Centre. Controllers at screens along both sides of the room watch over some of the most congested airspace on the globe, handling all airplanes below 24,500 feet flying to and from Heathrow and domestic airports Gatwick, Stansted, Luton, and London City. Today Andrew Garrett has one of the hottest seats in the room. He is the Heathrow director, guiding much of that airport’s incoming traffic.
Right now, his green-glowing screen shows problems: The northern stack, which collects airplanes from Central Europe, has turned into a snarl as pilots wheel around thunderstorms.
The landing rate has dropped from the usual goal of 45 airplanes an hour to about 35, troubling Garrett like too few RBIs would a cleanup hitter. Instead of three miles apart, airplanes entering the stack are about four miles apart, which to Garrett means wasted time. It also means airplanes showing up from around the world stack up faster; monitors in the center of the room show how many minutes each one is behind its estimated time of arrival.
He spots an Alitalia flight from Milan and sees a chance to shave off some time. It’s bound for a southern stack, but he intercepts it. Telling the pilot to turn right, Garrett weaves the Airbus A321 between two other aircraft sliding across his screen toward the runway. That puts one more airplane on the pavement this hour.
Up in the Heathrow control tower, controllers—some in their 20s and wearing T-shirts—sort everything out onto the pavement. The tower takes over flights four miles from the airport. By that point, the airplanes are on final approach, as set up by London Terminal Control Centre, so the tower controllers shouldn’t have that much to do with the aircraft aside from instructing inbound flights to adjust speed to maintain minimum spacing and keeping an eye on potential missed approaches.