Approach and Descent
The flight was conducting a coupled Category I ILS approach under fog and dark night conditions. After passing the final approach fix, the crew was notified that the runway visibility range (RVR) was below minimums. The captain continued the approach to decision height (DH) in accordance with company operations specifications. He visually acquired the runway prior to DH and continued toward landing.
Autopilot Disengagement and Heading Drift
About 60 feet above the runway, the captain disengaged the autopilot. The flight data recorder (FDR) indicated that the aircraft heading then began to drift right. The cockpit crewmembers stated that upon noticing the drift, the captain countered it with aileron and rudder inputs.
Roll Angle and Ground Contact
The FDR indicated a roll angle of -7.50 degrees at the instant maximum vertical G and minimum altitude readings were recorded, increasing to -14.90 degrees one second later. After the flight, damage was observed to the left outboard slats and flap. A Boeing chart indicated that at a pitch angle of 3.9 degrees and landing sink rate of 10 feet per second, the outboard slat and flap will contact the ground at a roll angle between 7.45 and 8.7 degrees.