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Human Failings Underscored In Report of 2002 Mid-Air Collision Over Germany

Air Safety Week, May 31, 2004

A copilot hesitatingly asked the right question about the alert to descend, was ignored, and they all died. From the fatal July 2002 mid-air collision over Switzerland of a B757 cargo aircraft and a Russian TU154, the object lesson that surfaces is to follow the direction of the traffic alerting and collision avoidance system (TCAS). If there is a contrary instruction from air traffic control (ATC), follow TCAS.

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That is but one of many messages contained in the report of investigation. The English language version of the German Federal Bureau of Aircraft Accidents Investigation (Bundesstelle fur Flugunfalluntersuchung, or BFU) report, released May 19, contains a sweeping agenda of 15 recommendations, in addition to the four issued during the course of the investigation. Among the recommended actions: TCAS should be enhanced to alert air traffic controllers when the airborne system issues a resolution advisory (RA) to its pilots. A resolution advisory is, in effect, a commanded avoidance maneuver when two airplanes are on a collision course. If both aircraft are TCAS-equipped, the systems communicate with each other, and one aircraft is alerted to climb and the other to descend. The alerts are sounded to give pilots at least five seconds to respond.

Such was the case in this mid-air collision. The TCAS worked as designed. But, as in most accidents, a range of insidious policy, training and procedural issues are involved. This accident was no exception. It was one where other breakdowns overwhelmed the last ditch defense that TCAS was intended to provide.

That the accident occurred in RVSM (reduced vertical separation minimum) airspace - with aircraft separated vertically by just 1,000 feet - makes it all the more important, considering the advent of domestic RVSM in the United States (see ASW, Nov. 3, 2003).

This is a case where the airplanes were equipped with the latest in TCAS technology, the pilots were trained in its use and rated as highly competent, the Swiss air traffic control system was rated as among the world's best, the controller was "handling" just three airplanes at the time, and yet two airplanes collided on a clear night sky, littering the pastoral countryside with shivered parts of the jets and the remains of the 71 persons aboard both aircraft. The BFU report hints at the macabre effect, noting the "extreme destruction" of the pilots' bodies and that 40 passengers in the TU154 "fell out of the airplane" when the stricken fuselage decompressed explosively. Those 40, mostly children, fell 35,000 feet to earth, perhaps shocked insensate by the explosive decompression and, in any event, the time of useful consciousness at that altitude is about nine seconds, a brief amount of time likely to be halved by the startle factor and the body's adrenaline-stoked accelerated burning of oxygen.

Although the airplanes collided in Swiss-controlled airspace, they fell near the town of Uberlingen, Germany, hence the BFU's primary role in the investigation.

Briefly, the DHL B757 cargo plane was on a flight from Bergamo, Italy, to Brussels. The Russian TU154 was on a flight from Moscow to Barcelona, Spain. The airport is located in mountainous terrain, and per company policy the Russian captain was making his second of two required flights under instruction to Barcelona. The instructor, in this case, was the company's chief pilot, and the BFU considered him the pilot in command (PIC). Altogether, there were five flight crewmembers in the cockpit of the TU154 trijet.

The pilots of both airplanes had received instruction and training in the functioning of their TCAS systems. The two pilots of the B757 had undergone TCAS training in the simulator. This was not the case for the Russian pilots. They had received the requisite classroom training (except the flight engineer), but a simulator was not available for real-time exercises (nor was it required).

The accident flight was the Russians' first operational experience with a TCAS alert. Moreover, two latent hazards lurked. First, although the pilots of both airplanes had completed crew resource management (CRM) training, the BFU noted a steep "authority gradient" in the Russian cockpit (i.e., the chief pilot definitely was in charge). Second, the documentation regarding TCAS compliance in the TU154 manual was, in the words of the BFU, "not sufficiently unambiguous." The manual stated that "ATC measures are the main and major condition of collision avoidance."

The priority of complying with a TCAS-generated RA was not stressed, although elsewhere the manual said maneuvers contrary to an RA were prohibited (i.e., if TCAS said climb, the pilot should climb).

This, basically, was the setup for the two aircrews.

The 35-year old Danish controller had been working at the Zurich area control center (ACC) since 1996 and was considered proficient. The center had recently been privatized and was operated by SkyGuide. On the night in question, the controller was slated to man the ACC in concert with another controller and two assistant controllers. He was aware that a 10-man team of technicians would be working on the ACC computers that night, and that the system would revert to the fallback mode for some hours.

Government Industry

Human Failings Underscored In Report of 2002 Mid-Air Collision Over Germany

Air Safety Week, May 31, 2004

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