Background
ADC Flight 086 departed from Port Harcourt Airport, climbing to FL240 as cleared. At 15:47, the crew established contact with Lagos Approach Control and received a transponder code. At 15:54, they reported crossing the SEPER point.
Sequence of Events
After the position report, the flight appeared to lose communication discipline, failing to respond to two consecutive calls from Approach Control and later answering a transmission intended for another aircraft.
Meanwhile, Triax Airlines Flight TIX185, a Boeing 727, had departed Lagos and was flying at FL160 toward Enugu. The Lagos controller terminated contact with TIX185 when ADC requested descent, but clearance was delayed to allow corporate jet 5N-APN to pass beneath the 727 at FL210.
At 15:59, Lagos Approach Control cleared ADC Flight 086 to FL160 and directed it to contact Lagos Radar. The flight was identified 41 miles southeast of the airport and instructed to fly heading 320° to avoid TIX185, descending to FL50. At 16:02:50, the controller twice ordered the flight to maintain heading 300°. The captain then took control from the copilot, stating, "I have it." At 16:03:08, the flight transmitted its last message: "I have the traffic... and I continue my heading to 330 to avoid him."
Flight Data Recorder Analysis
FDR data showed the aircraft initially maintained a coordinated turn toward heading 330 for the first 10 seconds of the final 50 seconds. After 15 seconds, the bank angle increased to 43.2°, held for 10 seconds, then to 68.8° for 5.5 seconds, and finally to 83°. The aircraft likely entered a high-speed stall and subsequent roll with a nose-down attitude. It appeared to recover just before impact, reducing vertical acceleration from 8.44 to 2.1 G and the bank angle to 61.6°, but lacked sufficient altitude. The aircraft crashed in a lagoon approximately 7.5 km west of Ejirin. Wreckage was located the following afternoon; the aircraft disintegrated on impact, killing all 144 occupants.
Probable Cause
The official finding attributed the accident to untidy traffic separation by the radar controller, resulting from vectoring ADC086 toward the track of opposing traffic TIX185. Additionally, the pilot's error in judgment to continue the turn to heading 330 to avoid TIX185 and the subsequent collision avoidance maneuver were identified as remote causes.