294 Part Three Planning and control Case study Air traffic control - a world-class juggling act www Air traffic controllers have one of the most stressful jobs in the world. They are responsible for the lives of thousands of passengers who fly every day in and out of the world's airports. Over the last 15 years, the number of planes in the sky has doubled, leading to congestion at many airports and putting air traffic controllers under increasing pressure. The controllers battle to maintain 'separation standards that set the distance between planes as they land and take off. Sheer volume pushes the air traffic controllers' skills to the limit. Jim Courtney, an air traffic controller at LaGuardia airport in New York, says: 'There are half a dozen moments of sheer terror in each year when you wish you did some thing else for a living. Error-free control is particularly important where people New York - the world's busiest airspace are being processed, as is the case for these air traffic The busiest airspace in the world is above New York controllers Around 7,500 planes arrive and depart each day at New York's three airports, John F. Kennedy, LaGuardia and are in three-dimensional airspace, flying at different altitudes Newark. The three airports form a triangle around New York and in various directions. The job of the approach con- and are just 15 miles from each other. This requires careful troliers is to funnel planes from different directions into an coordination of traffic patterns, approach and take-off routes, orderly queue before handing each one over to the tower using predetermined invisible comidors in the sky to keep controllers for landing the planes away from each other. If the wind changes, all three airports work together to change the flight paths. Tower controllers Sophisticated technology fitted to most of the bigger The tower controllers are responsible for coordinating planes creates a safety zone around the aircraft so that landing and taking off. Newark is New York's busiest air- when two aircraft get near to each other their computersport. During the early morning rush periods, there can be negotiate which is going to take action to avoid the other 40 planes an hour coming into land, with about 60 want- and then alerts the plot who changes course. Smaller ing to take off. As a result there can be queues of up to aircraft, without radar, rely upon vision and the notion of 25 planes waiting to depart. little plane, big sky At LaGuardia, there are two runways that cross each During its passage into or out of an airport, each plano other, one used for take-off and the other for landing. At will pass through the hands of about eight different con peak times, air traffic controllers have to shoot the gap' - trollers. The airspace is divided into sectors controlled by to get planes to take off in between the stream of landing different teams of air traffic controllers. Tower controllers at aircraft, sometimes less than 60 seconds apart. Allowing each airport control planes landing and taking off together planes to start their take-off as other planes are landing, with ground controllers who manage the movement of using 'anticipated separation, keeps traffic moving and the planes on the ground around the airport. The TRACON helps deal with increasing volumes of traffic. At peak times, (Terminal Radar Approach Control) controllers oversee the controllers have to shoot the gap 80 times an hour. surrounding airspace. Each New York air traffic controller Most airports handle a mixture of large and small handles about 100 landings and take-offs an hour, about planes, and tower controllers need to be able to calculate one every 45 seconds safe take-off intervals in an instant. They have to take into account aircraft type and capabilities in order to ensure TRACON controllers that appropriate separations can be kept. The faster The 60 TRACON controllers manage different sectors of planes need to be given more space in front of them than airspace, with planes being handed over from one con- the slower planes. Wake turbulence-mini-hurricanes which troller to the next. Each controller handles about 15 planes trail downstream of a plane's wing tips - is another major at a time, yet they never see them. All they see is a blip on factor in determining how closely planes can follow each a two-dimensional radar screen, which shows their aircraft other. The larger the plane and the slower the plane, the type, altitude, speed and destination. The aircraft, however. greater the turbulence. 295 Chapter 10 The nature of planning and control Besides the usual Marge planes, controllers have to Stress manage the small aircraft business helicoptero, traffic Dealing continually with so many sircraft movements means spotter planes and the many sightseeing planes flying over that controllers have but a split second to analyse and Manhattan, or up the Hudson towards the Statue of Liberty react to every situation, yet they need to be right 100 per The tower controllers have to control the movement of over cent of the time. Any small error or lapse in concentration 2,000 helicopters and light aircraft that fly through New can have catastrophic consequences. They can't afford York's airspace every day, being sure to keep them out of to lose track of a single aircraft, because it may stray into the airspace around each airport used by the arriving and someone else's airspace and into the path of another air- departing aircraft craft. If the computer projects that two planes are about to fly closer than three miles, the Conflict Alert buzzer sounds Ground controllers and the controllers have just seconds to make the right As an aircraft lands. It is handed over to the ground decision and then transmit it to the pilota Sometimes prob- controllers who are responsible for navigating it through lems arise in the planes themselves, such as an aircraft the maze of Interconnecting taxiways found at most running short of fuel. Emergency landing procedures cover intomational airports. Some airport layouts mean that such eventualitlen. At Kennedy airport, they have about one planes, having landed, have to cross over the runway such incident each day. As one controller remarked, "It's like where other planes are taking off in order to get to the an enhanced Video game, except you only have one we. terminal. All this needs careful coordination by the ground controllers. Questions Some pilots may be unfamiliar with airport layouts and need careful coaxing. Worse still is poor visibility, fog or 1 What does "planning and control mean to air traffic controllers? low cloud. At Kennedy airport, the ground radar does not show aircraft type, so the controllers have to rely upon 2 What are the differing problems faced by TRACON, memory and constant checking of aircraft position by tower and ground controllers? radio to ensure they know where each aircraft is at any 3 What sequencing rules do you think the tower time. controllers use