Controlling air traffic is one of the world's more stressful jobs. There's the "life and death" element, plus the need for razor-sharp reactions on everything from terrorist attacks to extreme weather. But despite the apparent complexity of the task, and the high-tech appearance of the equipment, it is still a job that relies completely on the ability and skill of its staff.
The basic process of finding the best route and landing safely would be simple if it wasn't for the thousands of flights dodging each other every day. The role technology plays in this process is, perhaps surprisingly, fairly minimal. The equipment looks impressive, and no flights would take off without being able to communicate with controllers, but the crux of the system still comes down to human decision-making.
"The technology is about providing information," says Jonathan Astill, head of operations at NATS' Prestwick control centre in Scotland. "At the moment, none of the decisions or actions that are necessary to keep aircraft apart are taken by automated systems. The controller makes the decisions based on the information provided by the IT. That will remain the same for quite some time yet."
As things stand, each controller receives information from 26 different air traffic management systems and must synthesise this into a schedule for each flight. If all goes well, the process is not complicated. The airline's operations department files a flight plan for each journey several hours before take-off is due, giving the flight's direction, speed, altitude and any other information needed to get it from A to B. The controller receives this, assesses it with other information available, and gives the flight the go-ahead. If anything changes during the flight, controller and pilot will communicate via encrypted radio or a satellite datalink.
The new centre at Prestwick controls the largest airspace in Europe. It handles 42% of UK air traffic and is the only provider of en-route airspace in the country, with all aircraft coming across the Atlantic going through it. It takes over from a control centre in Manchester, which now deals with flights taking off and landing from Manchester Airport. The move to Prestwick completes NATS' long-term plan to reduce the number of UK air traffic control centres from four to two, with the other centre being located in Swanwick, Hampshire.
NATS says delays attributable to air traffic control have fallen from 21.9 seconds per flight in 2008 to 4.6 seconds in 2009. The number of flights with no delay has risen from 98% to 99.5%. This is partly down to the Traffic Load Prediction Device, which helps supervisors to plan more precisely for expected traffic and adjust staffing levels accordingly.
While human decision-making and spatial awareness are still the integral parts of the process, technology continues to improve it. Better presentation of flight data and improved distribution of flights between controllers has reduced the workload associated with every flight, helping staff to handle more flights at a time.
Plotting a flight's route
Flight data, including its intended route, the type of aircraft and its altitude, is currently printed out. A series of empty spaces on the paper are used to record instructions passed to the aircraft or information received from it. Several strips of paper are used for each aircraft, each relating to a different time and position. The controller compares the positions of each flight at a given time, and builds up a mental model of where they all are. He or she tells any aircraft that might conflict to turn, climb or descend to resolve any problems. The paper strips are stored for about 30 days after the flight has passed through the airspace.
The technical version of this - Electronic Flight Data (EFD) - is expected later this year, and will allow information on each aircraft to be shared more easily between controllers. It will also make potential conflicts or unusual circumstances more obvious.
Reducing the distance between flights
Environmental concerns notwithstanding, people keep flying and the skies keep getting busier. Technology is helping more flights take to the skies by improving the surveillance tools on board an aircraft, allowing them to fly closer together.
Traditionally, aircraft use high-frequency radio to report their position when crossing oceans. Satellite-based datalink communications have improved this, boosting accuracy and frequency. The next step is one many airlines have already taken: installing systems called Automatic Dependent Surveillance - Broadcast or Contract (ADS-B and ADS-C). These help an aircraft to accurately report its position and share it with other nearby aircraft, and it creates the possibility of allowing flights to travel closer together.
NATS says it is also trialling ways of working called In-Trail Procedures that could reduce separation from the current 10 minutes to five.
|Air traffic controllers|
A tiny 3% of people accepted onto controller training courses complete the qualification. Astill says there are all sorts of reasons for this. The successful trainees have a well-developed ability to keep calm under high pressure, as well to receive and synthesise lots of different information. "In one ear you have someone on the telephone, in another you can have the pilot on the radio, and then you can be doing something else," says Astill, a former controller. "You need to be able to take lots of different sensory inputs and make sense of them." He says 80% of the job is about confidence; you really need to know what you are doing. Some technical knowledge is also required. Controllers need to understand the ins and outs of all the systems, as well as the basics of how radio and radar work, because if a part of the technology goes down, they need to know what they have lost, why they might have lost it, and possibly how to get it back.
Protecting the system
The control room at Prestwick is protected by a Faraday cage, preventing the use of mobile phones. Ordinary business systems are completely separate from the control room systems, and there are several layers of firewalls.
Astill says the most likely thing to fail is the power. Prestwick's power comes from two separate supplies, and if both of these fail, four generators can take over. If these go down, there are 110 tonnes of batteries on site that will run the site for two hours. There is also an off-site contingency building, although the location is undisclosed.
The control room has four separate power threads, so if one fails, only a quarter of the room will be affected. Each controller has a workstation with two terminals, and no workstation has two terminals on the same power thread.
Chief systems engineer, Frank Crozier, says, "There is a huge amount of testing - months in some cases when we make changes to the software. We have multiple systems, so if one has a problem, we can switch to another. Glitches are always possible, but everything we do has a safety process around it. There's always a point when something will fail so we have procedures around it so we know how we'll handle it. The most important thing is talking to the pilot, so we have two support telephone systems."
Radar tracks a flight until it is 160-180 miles from the control tower. Beyond that, aircraft are not tracked as they cross the Atlantic. Pilots have always kept track of where they are using in-flight navigational systems that work out how far they have travelled since they left the ground. The lack of radar is one reason why communication is important.
Technology enabling aircraft to be tracked by satellite exists, but has not been rolled out on a large scale. Aircraft do use satellite technology to decipher their own position, along with navigational systems and radar when they are passing a beacon. But air traffic control does not have the IT to track them, relying on pilots to communicate their whereabouts if it differs from the flight plan. Few aircraft are equipped with the technology controllers would need to track them, so the incentive to invest in new IT won't be there unless airlines also upgrade their systems.
A fully automated air traffic control system is probably unlikely. Technology goes wrong; a human would still be needed to watch the systems, correcting them when their automated decisions are not the right ones. The problem with that is, as with any highly skilled role, you need to keep practising to stay good, and watching the systems do it is not the same as doing it yourself.
Air traffic controllers play a role in dealing with national and international emergencies, and must be ready to act if something big happens. When the terrorist attacks took place in New York in 2001, the US closed its airspace and UK air controllers were left with half an Atlantic full of aircraft, about 200 in total. The aircraft had to take care of themselves as they each turned around with about 60 miles between them, and returned to the UK.
"Extra staff came in to help without being asked, because they knew things were going to get interesting," says Astill. But the process got easier as outgoing flights were cancelled, freeing up space.
This was first published in February 2010