After the passage of a rain storm over N’Djamena runway 05 (2800 m long) was wet with standing water. At 23:00 the Air Afrique Boeing 707 arrived from Paris. The aircraft touched down at Vref +4 knots and after extension of the spoilers and reverse thrust, the Boeing started to veer to the left. The crew managed to stay on the runway by reducing the reverse thrust. When applying reverse thrust again the aircraft started to move to the left again, so the pilots reduced reverse thrust again, but were forced to apply more reverse again when the aircraft neared the end of the runway. At a speed of about 10 knots it overran the runway, and the left MLG struck a concrete block and collapsed. The had problems maintaining its directional control due to the fact that no. 4 engine failed to go into reverse.