Accident Boeing 757-23APF A9C-DHL,
ASN logo
ASN Wikibase Occurrence # 323025

Date:Monday 1 July 2002
Type:Silhouette image of generic B752 model; specific model in this crash may look slightly different    
Boeing 757-23APF
Owner/operator:DHL Aviation
Registration: A9C-DHL
MSN: 24635/258
Year of manufacture:1990
Total airframe hrs:39022 hours
Engine model:Rolls-Royce RB211-535E4-37
Fatalities:Fatalities: 2 / Occupants: 2
Other fatalities:69
Aircraft damage: Destroyed, written off
Location:Überlingen -   Germany
Phase: En route
Departure airport:Bergamo-Orio Al Serio Airport (BGY/LIME)
Destination airport:Brussel-Zaventem Airport (BRU/EBBR)
Investigating agency: BFU
Confidence Rating: Accident investigation report completed and information captured
Bashkirian Airlines flight 2937, a Tupolev Tu-154M, and DHL flight 611, a Boeing 757-200PF cargo plane, crashed following a mid-air collision near Überlingen, Germany. All 69 on board the Tu-154 and both crew members of the Boeing 757 were killed in the accident.

Bashkirian flight BTC2937 operated on a charter flight from Moscow (DME) to Barcelona (BCN), Spain. The aircraft departed Moscow at 18:48 UTC and climbed to the planned cruising altitude of FL360.
Five flight crew members were in the cockpit. The commander (under supervision) - who was the PF (Pilot flying) on this flight - occupied the left-hand seat. The right-hand seat was occupied by an instructor, who as a PNF (Pilot non flying) also conducted the radio communications. He was also the pilot-in-command (PIC). The seat of the flight navigator was between and slightly behind the pilots. The work station of the flight engineer was behind the instructor. A further pilot (copilot), who had no function on this flight, was on a vacant seat behind the commander.

DHL flight DHX611 departed from Bahrain 13:30 UTC on a cargo flight to Bergamo (BGY), Italy to Brussel (BRU), Belgium.
The flight landed at Bergamo Airport at 19:10 UTC. The airplane was refuelled, unloaded and reloaded with cargo. Take-off for the last leg to Brussels was at 21:06 UTC. The airplane was flown by the copilot (PF).

At 21:21 flight DHX611 contacted ACC Zurich, and received clearance to climb to FL320 and subsequently to the planned cruising altitude of FL360. At 21:29 the airplane reached this flight level, without the pilots reporting it.
At 21:30 flight BTC2937 contacted ACC Zurich, and reported they were at FL360.
From about 21:33 a discussed ensued among the crew on the Tu-154 concerning an airplane approaching from the left which was displayed on the vertical speed indicator (VSI/TRA) which is part of the TCAS. The crew strived to localize the other airplane as to its position and its flight level.
Meanwhile, on board DHX611, the copilot had handed over the control of the airplane to the PIC in order to go to the lavatory. At 21:34:31 the PIC confirmed that he had taken over.
At 21:34:42 the airborne TCAS on board both flights alarmed the crews about possibly conflicting traffic by a Traffic Advisory (TA): “traffic, traffic".
Seven seconds later the radar controller issued descent instructions to flight 2937: "Descend flight level 350, expedite, I have crossing traffic". This descent was necessary for continuation of the flight to Barcelona and to achieve a vertical separation with respect to the approaching DHL Boeing 757.
At 23:42:56 the crews of both aircraft received a Resolution Advisory (RA)-command from their TCAS. The DHL crew complied with this and initiate a descent. At the same time the Tupolev crew were trying to deal with the conflicting descent (by ATC) and climb (TCAS) instructions. Seven seconds after the Resolution Advisory-command, the ACC Zurich controller repeated the instruction to descend. The Bashkirian crew then decided to follow the controller's instructions. A little later the TCAS aboard the Boeing 757 gave the crew a Resolution Advisory to "increase descent". At that time the First Officer had returned to his seat.
They then contacted ATC, reporting that they were doing a TCAS descent.
Since both aircraft were descending, the TCAS of the Russian plane warned the crew to "increase climb" to avoid a collision. This was eight seconds before the collision. Just prior to the collision, both crews detected the other aircraft, and reacted to avoid the collision by attempting appropriate flight manoeuvres. Nevertheless, at 23:35:32 both aircraft collided at approximately FL354. The tail fin of the Boeing 757 struck the left side of the Tupolev 154 fuselage near both overwing emergency exits, while the Tupolev's left wing sheared off 80% of the Boeing's tail fin. The Tupolev immediately broke up in four pieces (left wing, right wing, main fuselage and tail unit including the engines). The Boeing 757 lost control and crashed 8 km north of the Tupolev, just after losing both engines.

At the night of the accident, from 21:00 UTC, the configuration of the radar data processing of ACC Zurich was modified in order to re-arrange the control sectors.
During this time the radar system was operated in the "fallback mode" and the separation minimum had been increased from 5 to 7 NM. In doing so the MV9800 radar computer was not available to the controllers, therefore no automatic correlation of the flight targets was possible and the optical STCA (Short Term Conflict Alert) was not displayed anymore.
After the air traffic flow had decreased one controller retired to rest at about 21:15.
From then on one controller was solely responsible for the entire ATC within ACC Zurich. For this he had to fill two adjacent workstations with different frequencies and worked with two radar monitors. In order to control flights in the upper airspace and the approach in the lower airspace to Friedrichshafen. During the last five minutes prior to the collision, the controller paid more attention to the
Airbus A320 in approach to Friedrichshafen.
At 21:33:24 the radar controller of UAC Karlsruhe was alerted by his STCA of the conflict situation. His attempts to warn the controller of ACC Zurich by phone were not successful as a telephone connection could not be established.

A Russian man who had lost his family in the accident held the controller responsible and killed him at his home in Kloten, near Zürich, on 24 February 2004.

CAUSES: The following immediate causes have been identified:
- The imminent separation infringement was not noticed by ATC in time. The instruction for the TU154M to descend was given at a time when the prescribed separation to the B757-200 could not be ensured anymore.
- The TU154M crew followed the ATC instruction to descend and continued to do so even after TCAS advised them to climb. This manoeuvre was performed contrary to the generated TCAS RA.
The following systemic causes have been identified:
- The integration of ACAS/TCAS II into the system aviation was insufficient and did not correspond in all points with the system philosophy.
The regulations concerning ACAS/TCAS published by ICAO and as a result the regulations of national aviation authorities, operational and procedural instructions of the TCAS manufacturer and the operators were not standardised, incomplete and partially contradictory.
- Management and quality assurance of the air navigation service company did not ensure that during the night all open workstations were continuously staffed by controllers.
- Management and quality assurance of the air navigation service company tolerated for years that during times of low traffic flow at night only one controller worked and the other one retired to rest.

Accident investigation:
Investigating agency: BFU
Report number: BFU AX001-1-2/02
Status: Investigation completed
Duration: 1 year and 10 months
Download report: Final report





photo (c) BFU

photo (c) Aviation Safety Network

photo (c) Koen Gladines; Brussel-Zaventem Airport (BRU); 02 June 2000

Revision history:


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