Mayhem in the sky

8 April 1998 is a day forever etched on the furrowed brows of Britain's stressed-out air traffic controllers. It was a day when the airspace above Heathrow became clogged with aircraft caught out by a freak thunderstorm. It was a day which, for a terrifying 30 minutes, degenerated into chaos. It was a day that must never come again

ON 29 APRIL this year an air traffic controller at the London Area and Terminal Control Centre (LATCC) in West Drayton, Middlesex, sent a letter to senior management. "I have been a radar controller on the Clacton sector for 10 years," he wrote, "and throughout that time I have found it to be a `fast and furious' sector but a containable one. Yesterday, 28 April, the sector degenerated into chaos and was extremely dangerous. I have never been so frightened when controlling a sector. All the decisions had to be based on instinct as there was NO planning or thinking time ... I feel I must write to you to express my concern. After all, the blips we are controlling are REAL aeroplanes with REAL people on board, and I feel their lives were put at risk by yesterday's situation."

The letter went on to describe the "mayhem" that had occurred the previous day, and concluded: "I would like to make it clear now that should some remedial action not occur to ensure that yesterday's problems are NEVER repeated, I will hand in my CLN validation as I am not prepared to work under such dangerous and unprofessional conditions."

To understand fully what happened on 28 April, it is necessary to understand the nature of an air traffic controller's job and the stresses it involves on a day-to-day basis. "Like 3-D chess" is the image one controller uses to describe what he does. A controller sits at a radar screen which displays a given sector of airspace. The blips on his screen tell him the current altitude, flight number, destination and ground speed of all the aircraft in his sector. His job is to marshal those aircraft while keeping a safe distance between them, which is a statutory minimum of five miles, coming down to three miles on final approach (or two and a half miles in fine weather).

At LATCC there are usually around 120 controllers on duty at any time. Of these, around 50 work in the terminal control room, which is responsible for bringing aircraft safely in to land, and the rest work in the area control room, directing air traffic over the whole of England and Wales. The job requires high concentration and controllers are obliged to take a half-hour break every two hours, although such is the pressure that they are more likely to do so after an hour and a half or even just an hour.

In order for the system to work to its maximum capacity, the spacing of aircraft has to be precise - too close and it becomes dangerous, too far apart and the controller is "wasting space". The satisfaction of achieving an optimum flow rate can be considerable. "You think to yourself, `Oh yes, I've got a space there, now can I squeeze that one into it?'" one controller told me. "And you get it in and they're all safely separated and you get a nice flow. You do that for an hour, an hour and a half, and you think to yourself, `Oh I kind of enjoyed that'."

Such moments of enjoyment are becoming increasingly rare, however. The volume of air traffic in the skies is growing by around seven per cent a year, which means that controllers are now working under maximum pressure most of the time. "We used to have some easy sectors, so if you didn't feel quite up to it, you used to say, `Do you mind if I just sit over there and do that bit?'" one told me. "But today there are no easy sectors at all, it's bang, bang, bang all the time. There's hardly any let-up."

Half the time when they are working, controllers also have to supervise a trainee who is directing air traffic but whose directions can be over- ridden if necessary. "They're making mistakes all the time with real aircraft, real lives," said one. "We come close to having air-misses every day. You have to catch them and you've only got seconds to do something, so you really have to be on the ball. Of course that puts your stress level right out of the window." Many controllers believe that it is now too busy at LATCC for trainees to work there safely.

Pilots can be a problem, particularly if their use of English, the universal language of air traffic control, isn't up to scratch. Controllers tend to accuse those from the newer Eastern bloc countries and from South America of being particularly bad. "The thing is, you're going at twenty to the dozen and these guys are going, `Sorry? Say again'," said one controller.

In the area control room at LATCC, the equipment is 26 years old and spares are no longer manufactured for it. There used to be a spare radar suite available if one went down, but that is now in constant use. "The computer fails on a regular basis," said one controller. "Our radars go blank." Without radar, the controllers can fall back on procedural control, which enables them to separate aircraft according to time and height. "That's our safety net," the controller went on. "But you can't really do that nowadays because we're spacing aircraft right on the five miles that we need and doing some really complex stuff with them, turning them behind each other and so on. If the radar goes then, you're up shit creek without a paddle, really."

But the major potential cause of disruption is bad weather. In the case of, say, thunderstorms, a controller can suddenly find he's playing 3- D chess on an entirely new board, as aircraft are re-routed to avoid flying through the storm. "You have complete traffic flows move into areas of airspace which they're not normally supposed to be in, so you end up having to co-ordinate with someone else because you're in their airspace," one controller said. "Instead of falling back on a procedure, you then have to think on your feet."

There was early fog and low cloud at Heathrow on the morning of Tuesday, 28 April. In accordance with standard procedures for bad visibility, air traffic managers at LATCC had already reduced the landing rate at the airport as the day's first scheduled arrival touched down at 6am. The standard landing rate at Heathrow is 45 aircraft per hour, but on this morning it had been set at just over half that. This meant inevitable delays for in-coming aircraft. Some would be forced to wait in holding patterns until they were given permission to land. Others were sitting on the tarmac at airports all over Europe, awaiting the go-ahead to begin their journeys. But as the fog began to lift, the landing rate was gradually increased. Finally, at 7.55am, when the last residual low cloud had dispersed, traffic managers set the rate to the standard 45 per hour.

According to an internal report concerning the events of April 28th written by the National Air Traffic Services investigation unit, the area control watch supervisor at LATCC "did consider that the proposed flow rate for Heathrow was a little high, but was prepared to accept the advice of the traffic managers". There was a sound reason for his concern. When the landing rate returns to normal, it's the signal for Euroflow control in Brussels to allocate take-off times for delayed aircraft all over the continent. With some aircraft already in holding patterns over England, a fresh influx could cause the holding stacks to become congested. However, the situation was nothing out of the ordinary and at 8.30am the terminal control traffic manager reported that all seemed well, with holding time averaging just 15 minutes. Controllers braced themselves for the anticipated explosion of blips on their screens as the European wave arrived. It was going to get busy, but it was nothing they couldn't handle.

And then the unexpected happened. Everyone concerned was fully aware of a Met Office warning which stated that thunderstorms and hail would become widespread during the afternoon. However, the storms began much earlier than forecast. By approximately 9.30am, thunderstorms had already broken out over south-east England. Soon after 10am, the storms began seriously to affect the area of the main holding stack for Heathrow, which is over Lambourne, near Romford in Essex. For the controllers directing this sector of airspace, the so-called Clacton sector, which acts as the main entry point for aircraft entering British airspace from mainland Europe, the unexpected disruption caused their already high workload to rise to almost unmanageable levels. The Lambourne stack was soon full to capacity, and the two subsidiary stacks, codenamed Saber and Logan, were also reaching saturation point as more and more aircraft flowed into the sector. In an attempt to control the situation, the chief controller of the Clacton sector doubled the number of his control staff from three to six. Another chief was also brought in. (All the controllers I spoke to said it was sheer luck that enough controllers with the appropriate experience happened to be on hand at the time.)

When all three stacks were full, the controllers then had to route other arriving aircraft through those which were already circling. "There were all these other aircraft still flowing in with nowhere to go, it was chaos," said a controller who was working on a nearby sector at the time. "They were borrowing all our airspace. We could see the carnage that was going on. There were in excess of 50 aircraft just going round in circles. They [the controllers] were doing some really unusual things with the aircraft to avoid hitting the ones going round in circles. To be quite honest, I thought it was out of control."

"Everything coming into that sector, somewhere along the line, was going to be in conflict with something else, and they couldn't stop the traffic coming in," another controller told me. "There were controllers with 15 years of experience and even they were just spotting the conflictions at the last minute."

"One of them told me, `I never noticed one confliction until they were ten miles apart'," said another. "Ten miles head on! It was a case of `Turn right now!'. [The combined closing speed of the two aircraft would have been around 12 miles per minute.] It's just by the grace of God that nothing happened. We were fortunate that all those controllers were very experienced and extremely competent. If there'd been any guys on there who were newly validated, I don't think they would have coped. You don't really want to think about the consequences. We do emergency training, but you can't really train someone to cope with that scenario. It was really bad, it was awful." The mayhem lasted for around half an hour. The flow rate was reduced and traffic from Maastricht, Brussels and the North Sea was stopped from entering the sector while the controllers sought to empty the stacks. It had been a harrowing experience for all involved. "I saw all the controllers just after they'd been relieved," one observer told me. "There was a woman who was physically shaking. She'd copped it quite bad, she was on the worst position. The rest of them were up in arms. They all marched up to the super visor's desk, and there was a big shouting match going on about why they'd been put under so much pressure." According to the official investigation report: "The actions taken prior to this incident are similar to those taken on other occasions which have led to successful conclusions. In the circumstances the decisions made were logical and based on soundinfo rmation and past experience." The report concludes that "an over-delivery of traffic for Heathrow did occur" and that "the situation may have been mitigated by closer monitoring of the actual traffic situation by supervisory staff". There is nothing in the report to suggest that in the same circumstances, similar "mayhem" would not necessarily happen again. When a controller faces a situation in which the number of aircraft he has to deal with at any one time means that if one of th em has a problem, he is unable to give it his full attention, he later files what is known as an "overload report". Following the events of 28 April, every controller on the Clacton sector filed one. One controller told me he expected the number of overload reports to be filed at LATCC this year to rise to around 40 from last year's 12. The controllers are finding themselves more and more overloaded, and the strain is beginning to show. "The older co ntrollers are feeling the pinch now, it's very obvious to all of us that they're struggling," a controller in his early thirties told me. "It's a young person's job nowadays, definitely. But I think even the younger element are now walking away at the en d of a shift saying, `Bloody hell, that was busy'." The number of controllers on long-term sickness leave, known ironically as "gardening leave", has increased more than threefold since last year. Currently around 20 radar operators out of the 240 who work at LATCC are on sick leave lasting from one month to more than two years. Some are suffering from serious back problems as a result of the horizontal screens they have to bend over, but most are suffering from stress-related illnesses. At least five have been prescribed Prozac to combat depression. One ray of light for the controllers was to have been the new pounds 163 million control centre at Swanwick in Hampshire. It was originally scheduled to be operational in 1996, but software problems have led to continuing delays. It is now scheduledto o pen in 2000, but many believe even this is optimistic. Those controllers who have already moved house to be nearer the new centre face many more months of lengthy commuting to West Drayton. The recent announcement by Gordon Brown that the Government is to sell off a 51 per cent stake of National Air Traffic Services has further added to the controllers' worries. They fear that the private sector might cut costs at the expense of safety, and they are also concerned that one or more of the airlines might buy into NATS, leading to pressure on controllers to give their aircraft preferential treatment. "People are brassed off," one controller told me. "They expected to be down at the new centre over two and a half years ago, and they still don't really know when they're going. And now with this privatisation thing, it's just another sword of uncertaint y hanging over their heads." In the meantime, the traffic in our skies just gets busier, and life for our air traffic controllers gets more and more stressful. Things can only get worse, it seems, before they get better.