Bashkirian Airlines Flight 2937, Tupolev Tu-154 M, collides with DHL Flight 611, a Boeing 757-23APF, in the skies above the town of Überlingen, Germany.
On the night of 1 July 2002, Bashkirian Airlines Flight 2937, a Tupolev Tu-154 passenger jet, and DHL Flight 611, a Boeing 757 Freighter, collided in mid-air over Überlingen, a southern German town on Lake Constance. All 69 passengers and crew aboard the Tupolev and the two crew members of the Boeing were killed.
Bashkirian Airlines Flight 2937, was travelling from Moscow to Barcelona. With a total on board of sixty passengers and nine crew. Forty-five of the passengers were Russian schoolchildren. DHL flight 611 originated in Bahrain and stopped over in Bergamo, Italy. At the time of the accident, the aircraft was en route from Bergamo, Italy, to Brussels.
The cause of the Accident?
Firstly both aircraft where flying at Flight Level 360 (36,000ft) and on a heading to cross flight paths. Despite flying over Germany the two aircraft where under control of Zurich ATC. There was only one controlled on duty on the night of the fateful accident. Peter Nielsen was working two workstations at the time. Due to the added workload and due to delayed radar data didn’t see the problem unfolding. As a result he failed to keep the aircraft within safe seperation distances.
Less than one minute before the accident he realized the danger and contacted Flight 2937. Instructing the pilot to descend by a thousand feet to avoid collision with crossing traffic FLight 611. Seconds after Flight 2937 initiated the descent, their traffic collision avoidance system (TCAS) instructed them to climb. while at the same time the TCAS on Flight 611 instructed the pilots of that aircraft to descend. Had both aircraft followed those automated instructions, the collision would not have occurred.
Flight 611’s pilots followed the TCAS instructions and initiated a descent, but could not immediately inform ATC because the controller was dealing with Flight 2937. About eight seconds before the collision, Flight 611’s descent rate was about 2,400 feet per minute (12 m/s), not as rapid as the 2,500 to 3,000 ft/min (13 to 15 m/s) range advised by TCAS. Having already started his descent, as instructed by the controller, the pilot on the Tupolev disregarded the TCAS instruction to climb. So both planes were now descending.
Unaware of the TCAS-issued alerts, ATC repeated instructions to Flight 2937 to descend, giving the crew incorrect information as to the position of the DHL plane (informing them that the Boeing was to the right of the Tupolev when it was in fact to the left).
The two collided at 23:35 local time, at an altitude of 34,890 feet. Flight 2937 broke into several pieces on impact. Where as flight 611 severely crippled fought on for another 7km before crashing into a wooded area close to the village of Taisersdorf at a 70-degree downward angle.
Contributing Factors.
Firstly with one controller on duty at the time of the accident Peter Nielsen was single handed responsible for two work stations. Whilst the other controller was resting in another room for the night. This was against the regulations but was due to poor management common practice. Secondly the night of the accident the primary radar system was under maintenance, meaning Nielsen had to rely solely on a back up system. Finally the ground-based optical collision warning system, which would have alerted Nielsen to the pending collision 2½ minutes before it happened had been switched off for maintenance. Nielsen was unaware of this. There still was an Audible STCA (Short term conflict alert) warning system. Which released a warning at 23:35:00 (32 seconds before collision.) This warning was not heard by anyone present at that time. Although no error in this system could be found in a technical audit; whether this audible warning is turned on or not, is not technically logged. Even if Nielsen had heard this warning, at that time finding a useful resolution order by the air traffic controller is impossible.
Legal cases & Aftermath.
Nielsen needed medical attention due to traumatic stress caused by the accident. Skyguide initially blamed the pilots of Flight 2937 before later accepting responsibility for the accident. Skyguide did pay out compensations to the families of the dead children the compensation amount was about SFr30,000 ($34,087).
On 27 July 2006, a court in Konstanz decided that the Germany should pay compensation to Bashkirian Airlines. As it was found they where legally responsible for the actions of Skyguide. In late 2013 Bashkirian Airlines and the Federal Republic of Germany reached a tacit agreement, ending the court case before a decision on the legal issues was reached.
Following the accident and devastated by the loss of his wife and children Vitaly Kaloyev, hunted and tracked down Peter Nielsen on 24 February 2004. Where Vitaly stabbed and killed Nielsen in front of his family in the town of Kloten, near Zürich.
TCAS?
TCAS (traffic collision avoidance system) was still fairly new technology and was mandatory in Europe since 2000. When TCAS issues a resolution advisory (RA), the pilot flying should respond immediately by direct attention to RA displays and maneuver as indicated. Unless doing so would jeopardize the safe operation of the flight, or unless the flight crew can assure separation with the help of definitive visual acquisition of the aircraft causing the RA. (FAA regulation). In response to any RA in deviation of assigned altitude when safe to do so pilots should alert ATC and assumed the previous assigned altitude.
TCAS assumes both pilots will respond and take the actions issue in the RA. Originally the operations manual didn’t state that in the event of a conflict pilots should disregard ATC instructions and take actions based on the RA instructions. The manual described TCAS as “a backup to the ATC system” Therefore it is now a common practice to follow all instructions issued in the RA.
