Events Leading To German Midair Reveal Complex Scenario

By Jens Flottau/Aviation Daily

09-Jul-2002 10:03 AM U.S. EDT

The collision warning system on the Bashkirian Airlines Tupolev TU-154 jet involved in last week's midair collision over Germany instructed the plane to pull up to avoid a fast-closing DHL 757 at the same altitude, but the crew heeded a nearly simultaneous ATC instruction to descend, putting the planes back on a collision course, investigators said yesterday.

According to German investigators who released some cockpit voice recorder (CVR) details on Monday, both planes' Traffic Alert and Collision Avoidance Systems (TCAS) were issuing "traffic, traffic" warnings a little less than one minute before the crash. Fifteen seconds later, the 757 TCAS issued a "resolution advisory" that called for the pilot to "descend, descend," while the Tupolev system called, "Climb, climb."

Assuming the two systems were operating correctly, they would have been coordinating the advisories so that, if followed by the pilots, the planes would not hit each other. About one second after the advisories, however, the Skyguide controller in charge told the Tupolev crew to "descend Flight Level 350 [35,000 feet], expedite, I have crossing traffic."

It is not clear if the Bashkirian pilots reacted immediately, but the controller 14 seconds later urged them to "descend Level 350, expedite descent." Skyguide claims the Tupolev started its descent only after the second call. The two aircraft collided at FL354, while both were descending from FL360.

Minutes before the accident, both aircraft were cruising at 36,000 feet (FL360), with the Tupolev heading west on a charter flight from Moscow to Barcelona and the DHL 757 heading north on a scheduled service from Bergamo to Brussels. The 757 had been under Zurich ATC's control for seven minutes and the Tupolev for five minutes.

The CVR information adds to an increasingly complex set of factors related to the accident that killed 71 people. Controller workload and cockpit procedures are the investigation's focus.

Meanwhile, Skyguide has confirmed that its Short Term Conflict Alert (STCA) system that warns controllers of conflict situations was down for maintenance that night. Also, the main telephone line was down. At the time of the crash, the controller handled five aircraft, one of them on a different frequency on approach to Friedrichshafen airport.

The controller tried to call Friedrichshafen tower for about eight minutes until 21:33:11 UTC but did not get through on the reserve line. The collision took place around 21:35:33. A second controller, who should have assisted him in the sector, had taken a break. A controller at the German ATC center in Karlsruhe became aware of the situation and wanted warn his Swiss colleague but failed to get through to him.

According to the German aircraft accident investigation authority, BFU, minimum lateral separation with STCA down should have been 7 nautical miles (up from the regular 5 nm). In order to comply with the regulation and with a 1,000 ft. vertical separation, Skyguide should have told the Tupolev to descend to FL350 around 90 seconds before the crash, but the first call came only 44 seconds before impact.

As a result of the crash, Skyguide has reduced peak capacity by 20% to "reduce controller stress." The measure, which is planned to remain in place until mid-July, leads to significant delays. A spokesperson for Swiss International Air Lines said delays of 30 minutes were common on Monday. But also east-west traffic is expected to be severely affected right at the start of the European holiday season.

Aviation Week & Space Technology:
July 15, 2002
 

Europe Needs More
ATC Common Sense

The international team investigating the July 1 midair collision over Lake Constance, in southern German airspace, needs to put a damper on bickering among Russian, German and Swiss authorities. Politics can't be allowed to intrude on the effort to perform an objective analysis of possible problems with equipment, communications, human factors, procedures or organizations. The lessons learned could prevent a recurrence. With the investigation just underway, it is clearly too soon to draw conclusions. However, Europe's decades-long failure to unify its fragmented airspace, and an astonishing loss of vigilance in managing air traffic, were contributing factors.

In this context, investigators can be expected to sharply criticize Swiss air traffic control operator Skyguide's policy. Performing maintenance work on ATC systems at night, when the traffic level is low, makes sense. However, in the temporary absence of a working collision warning system at Zurich Control, the rules dictated that both controllers in the sector be at their stations. Sadly, one person was taking a break.

In the same vein, conventional communications systems should be constantly checked to verify they are working. In this era of high-speed Internet, it is hard to believe that controllers separated by a virtual border could not reconcile conflicting flight paths electronically in the absence of working phone lines.

Such weaknesses also expose European government foot-dragging in implementing the European Commission's objective of linking ATC centers, which are fragmented by national boundaries, to a more efficient, unified system or a "Single European Sky." The need to unify Europe's airspace to cope with higherspeed aircraft has been stressed since jet transports entered service in the late 1950s. But self-interest and national pride have stalled progress.

The 71 victims of this month's midair collision paid the highest price for such a formidable breach of European unification and collective discipline. Only EC Vice President/Transport Commissioner Loyola de Palacio's determination and wide-ranging political support could lead to the long-overdue Single Sky. In the meantime, it is the European aviation community's responsibility to restore efficiency to its strained ATC network. The July 1 wake-up call also shows common sense could provide much-needed safeguards.

Also See: Appreciation: Benjamin O. Davis, Jr. 1912-2002

From the New York Times:

Midair Crash Opens Debate on Air Safety Over Europe

By MARK LANDLER


FRANKFURT, July 20 — Europeans can drive from Stockholm to Seville without stopping at a border post or showing a passport. But if they fly across the Continent, their pilot must deal with a long succession of national air traffic authorities, some calling on different radio frequencies, as the plane streaks across the borders that divide the skies of one country from the next.

Aviation experts have complained for years that this fragmentation of airspace contributes to the chronic delays in European flights, since pilots take longer plotting their routes.

Now, in the wake of the recent midair crash of a Russian passenger jet and a Boeing 757 cargo plane over southern Germany, some say Europe's patchwork of air traffic control systems is also a safety threat.

"Many of these countries are way, way too small to have their own air traffic control centers," said Jim Eckes, the managing director of Indoswiss Aviation, an airline consulting company. "The Swiss airspace should be merged into the German zone. If the Germans were running it, this accident probably wouldn't have happened."

Such assertions are predictably controversial in Europe, where sovereignty and pride often clash with growing economic and political integration.

But officials here acknowledge that among the baffling chain of missteps that led to the midair collision on July 1 was a breakdown in communication between controllers in Karlsruhe, Germany, who had been tracking the planes, and the controller on duty in Zurich, who picked up the planes as they flew close to Lake Constance, in southern Germany near the Swiss border.

Investigators say the German controller tried desperately to call his counterpart in Zurich, after noticing that the planes were on a collision course two minutes before the crash. But the line was busy.

"Normally a controller should have a hot line to call his colleague," said George Paulson, the director of safety, airspace and airports at the European Organization for the Safety of Air Navigation, which provides technical advice on air traffic control issues to 31 European countries.

Mr. Paulson said his organization, known as Eurocontrol, had set up a high-level committee after the crash to draft new safety recommendations. It expects to issue the guidelines in November.

Among the possible recommendations, he said, could be emergency phone lines, or a computer link, between air traffic control centers in different countries. It may also suggest ways to improve communication between pilots and controllers.

On the fateful night of July 1, the Swiss controller ordered the pilot of the Russian Tupolev Tu-154, to descend to avoid the Boeing, operated by the overnight courier service DHL Worldwide Express. Later, the collision warning system on the Russian plane instructed the pilot to climb. He obeyed the Swiss controller, with tragic results.

"It's an accident that never should have happened," Mr. Paulson said.

Despite that, he said Europe's safety record compared favorably to that of the United States, which has a unified air traffic control system. Midair crashes are rare on both sides of the Atlantic.

The difference is that American controllers handle double the volume of traffic, on average, of their European counterparts. As traffic in Europe becomes more congested, experts worry that its fragmented system — which uses 73 control centers, compared with 22 in the United States — will not be able to cope.

Defenders of the European system point out that in most countries the private companies that provide air traffic control services use newer, more advanced technology than that used in the United States.

Still, Europe's airlines are pushing for a uniform airspace, which would be regulated by the European Commission. Their motivation is mainly economic: eliminating national boundaries would allow Europe to consolidate its 73 centers into a few megacenters.

Not surprisingly, the chief opponents of the idea are the controllers themselves. They fear that streamlining Europe's air traffic system will lead to a loss of jobs. And they argue that the commercial pressure will increase, not reduce, the likelihood of future crashes.

"There's nothing wrong with harmonizing the system," said Marc Baumgartner, a controller in Geneva who is president of the International Federation of Air Traffic Controllers. "But the way the E.C. is doing it is through economic incentives, and that has a direct impact on training." He acknowledged, however, that the crash had thrown many long-held assumptions into question.

"It took away a bit of our religion," he said. "We had all the safety nets in place to prevent this, and still it happened."
   

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