Incident Overview
On a flight over the South Atlantic Ocean, a US Air Force Lockheed C-141B Starlifter collided with a German Air Force Tupolev 154M approximately 65 nautical miles west of the Namibian coast. Both aircraft crashed into the sea, killing all 33 occupants.
Flight Details
The Tupolev 154M, registration 11+02 and call sign GAF074, operated from Cologne/Bonn Airport, Germany, to Kaapstad, South Africa, with planned refueling stops at Niamey, Niger, and Windhoek, Namibia. It carried ten crew members and 14 passengers. The aircraft departed Niamey at 10:35 UTC.
The C-141B, registration 65-9405 and call sign REACH 4201, had delivered UN humanitarian supplies to Windhoek and was returning to the US via Georgetown on Ascension Island. It had nine crew members. REACH 4201 departed Windhoek at 14:11 UTC and climbed to its filed and assigned cruise level of 35,000 feet (FL350).
Air Traffic Control Communications
At the time of the collision, GAF074 was not at its filed cruise level of FL390 but was still at its initially assigned cruise level FL350. Windhoek ATC was in sole and continuous radio contact with REACH 4201 and had no knowledge of GAF074's movement. Luanda ATC was in radio contact with GAF074 but not with REACH 4201, though Luanda ATC had received flight plans for both aircraft and a departure message for REACH 4201 only.
At 15:10 UTC, both aircraft collided at FL350 and crashed into the sea.
Investigation and Probable Cause
The Accident Investigation Board, presided over by Colonel William H. C. Schell Jr., USAF, determined the primary cause: GAF074 flew at a cruise level (FL350) that was not the level they had filed for (FL390). Neither FL350 nor FL390 were the correct cruise levels for that aircraft's magnetic heading according to International Civil Aviation Organization regulations; appropriate levels would have been FL290, FL330, FL370, FL410, etc. A substantially contributing factor was Luanda ATC's poor management of air traffic through its airspace. While communications could be improved, Luanda ATC had all pertinent information needed to provide critical advisories to both aircraft. If unable to contact GAF074, Luanda should have used other means (HF radio, telefax, or telephone) to contact REACH 4201 through Windhoek ATC. Another substantially contributing factor was the complicated and sporadic operation of the Aeronautical Fixed Telecommunications Network (AFTN), which caused delays and misroutings. Windhoek ATC did not receive a flight plan or departure message for GAF074, which could have helped identify the conflict. The absence of TCAS was not considered a cause or substantially contributing factor, but the presence of a fully operational TCAS could have prevented the accident.