Skyguide cuts capacity by 20 per cent

Skyguide's controllers have been under pressure since last Monday's accident Keystone Archive

The Swiss air traffic control agency, Skyguide, has cut its work capacity by 20 cent following Monday's mid-air collision over southern Germany.

According to Felix Hitz, Skyguide’s chief of staff, the agency’s controllers have been under severe stress since the accident between a Russian Tupolev and a DHL cargo jet. Skyguide wants to take some of the pressure off its employees.

The reduction of work capacity went into effect on Friday at midnight until further notice. Delays are expected at Zurich airport.

The lowered capacity will be taken into account by the European air traffic control centre in Brussels. It concerns both departures and arrivals at Zurich airport, as well as flights over the sector controlled by Skyguide.

Technical problems

The announcement comes just one day after German investigators said the lone air traffic controller on duty in Zurich when the two planes collided in mid-air on Monday was battling with technical problems.

The investigators said on Friday that Skyguide was working on its telephone and radar systems on the night that two aircraft slammed into each other at 11,000 metres above Lake Constance.

The revelation has added weight to growing criticism of Skyguide’s role in the disaster, which left 71 people, including 45 children, dead.

According to the German Aircraft Accident Investigation Bureau, Skyguide’s air traffic controller was using a temporary line while technicians worked on its regular system.

Around the same time Skyguide’s radar data processing system momentarily went out of action.

The problems meant the air traffic controller was simultaneously monitoring two frequencies and two radar monitors. At the same time the two aircraft were on a collision course.

Control system discrepancies

Between 2325 and 2333 the air traffic controller repeatedly attempted to contact an aircraft that was landing at the German port of Friedrichshafen.

Shortly afterwards, at 2334, the controller made contact with the Tupolev – just 44 seconds before it collided.

The Russian pilot began to lose altitude 30 seconds prior to impact – around the same time as the Boeing pilot began to initiate a descent after his in-flight warning system warned of the on-coming Tupolev.

The Swiss Aircraft Accident Investigation Bureau added on Friday that part of the control system wasn’t working properly just prior to the accident.

No hiding of facts

The short-term conflict alert system (STCA), which is designed to warn the controller visually and acoustically that two aircraft at the same altitude are too close, did not function. There are also discrepancies between the legal recording system of the radar and what the controller saw on his screen.

According to the Bureau, one of the discrepancies is that the STCA was working in the background, but did not show any warnings on the control monitor.

In a report published just over a week ago, the Swiss Bureau had recommended that Skyguide conform to European standards by making sure that any discrepancies between the legal recording and the control monitor were eliminated.

Skyguide has also answered criticism that it was trying to bury the facts about the accident. The head of the agency, Alain Rossier, admitted on Swiss radio on Saturday that there had been errors in communication following the tragedy, but he said there had been no desire to hide the truth.

Everything that happened would be studied second by second, Rossier said. He said three questions had to be answered: the reactions of the controllers, of the pilots and of the systems in the planes.

“Only then will we be able to say whether it is only a disaster for us or whether it is also a disaster for others,” said Skyguide’s boss.

swissinfo with agencies