Swanwick upgrades after near miss

The near miss of two large passenger jets over Wales, during which a woman was injured, has led to a change in the design of...

The near miss of two large passenger jets over Wales, during which a woman was injured, has led to a change in the design of software at a £623m air traffic control centre in Hampshire.

An upgrade to the software at the Swanwick air traffic control centre near Fareham will be made next month to help to prevent the recurrence of an incident in which an air traffic controller confused the positions of a Virgin Atlantic 747-400 jumbo and a Delta Airlines 767 on his screen.

The controller thought his instructions to the pilots of the aircraft would direct their aircraft away from one another, but the opposite happened.

In the moments before the near miss on 15 November 2002, the controller had not realised he had mistakenly transposed the data boxes on the positions of the two aircraft. As he tried to force the jets apart, he brought them closer together.

During the incident other controllers gathered around and saw the aircraft converging. The confusion occurred, in part, because Swanwick's Windows-like displays give controllers the flexibility to use the mouse to click on and drag blocks of data about aircraft around the screen.

The boxes of data, called track data blocks, identify the aircraft and are usually displayed next to a diamond symbol that depicts the radar return of the jet. Controllers can move data blocks to stop them overlapping.

In the incident the controller who was operating several air space sectors simultaneously, repositioned the data blocks of the 747 and the 767. Later, according to the report, the controller "seemed to have forgotten" that he had swapped the text boxes.

Had there been a line or strut which connected the aircraft's diamond symbol to its associated track data block, there would have been no confusion, said the report. Next month's upgrade will ensure that a strut is displayed whenever a data block is moved.

National Air Traffic Services revised its operating procedure after the incident.

Stan Price is a former IT engineer at NATS who has studied the report of the Airprox Board, which examines the causes of near misses. He said that it lacked a "systems view", which implied that the operator should cope with the vagaries of the equipment.

"There is no appreciation of how the balance of control has moved to equipment, particularly the software," Price said.

A NATS spokesman said, "Changes to the software at Swanwick, to further improve the legibility of track data blocks - if they are moved - will be made next month after an extensive design and test programme.

"The change will ensure that, whenever a data block is moved, it will be automatically linked [by way of a strut on the screen] to the aircraft target to which it belongs."

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