23 Years ago today: On 7 November 1996 an ADC Boeing 727 lost control and crashed during an evasive manoeuvre to avoid collision while approaching Lagos, killing all 143 occupants.

Date:Thursday 7 November 1996
Type: Boeing 727-231
Operator:ADC Airlines
C/n / msn:20054/718
First flight:1969-04-29 (27 years 7 months)
Engines:Pratt & Whitney JT8D-9A
Crew:Fatalities: 10 / Occupants: 10
Passengers:Fatalities: 134 / Occupants: 134
Total:Fatalities: 144 / Occupants: 144
Aircraft damage:Destroyed
Aircraft fate:Written off (damaged beyond repair)
Location:near Ejirin (   Nigeria)
Phase:Approach (APR)
Nature:Domestic Scheduled Passenger
Departure airport:Port Harcourt Airport (PHC/DNPO), Nigeria
Destination airport:Lagos-Murtala Muhammed International Airport (LOS/DNMM), Nigeria

The ADC aircraft was flying at FL240 en route from Port Harcourt to Lagos. At the same time a Triax aircraft had departed Lagos and was flying at FL160 towards Enugu. The Lagos controller had terminated contact with the Triax aircraft when the ADC crew requested to descend. The permission to descend was delayed to allow an ELF Petroleum bizjet to pass beneath the 727 at FL210.
When the controller finally cleared the ADC flight to descent, he thought he had cleared to aircraft to FL100 at an earlier stage, but the aircraft was still flying at FL240. When the ADC aircraft descended through FL160, the TCAS alarm sounded. To avoid a head-on collision the flight crew immediately took evasive action. During this maneuver, the Boeing rolled to an excessive bank angle and control was lost. Within 16 seconds speed had increased from 280 knots to almost the speed of sound. The aircraft crashed and disintegrated on impact

Probable Cause:

IMMEDIATE CAUSE: “The untidy traffic separation by the radar controller which resulted from the vectoring of ADK 086 towards the track of the opposite traffic TIX 185.”
REMOTE CAUSE: “The error of judgement by the pilot of ADK 096 to continue his turn to heading 330 M to avoid TIX 185 and his subsequent collision avoidance manoeuver constituted the remote causes of this accident.”