What happened
During the descent for an ILS approach to runway 35L, the crew encountered weather conditions consisting of fog with ceilings between 300 and 1,000 feet and 1/2 mile visibility. The first officer was hand-flying the aircraft when the crew received a special observation regarding the weather. While at 9,000 feet, the captain reported that the glide slope indicator had moved below the aircraft and that the localizer had not yet been intercepted. Following a request for a lower altitude, TRACON cleared the aircraft to 7,000 feet.
The crew continued the approach, with the captain reporting that the aircraft was configured and intercepting the localizer. At 10 and 100 feet, the captain reported seeing approach lights. Upon reaching decision altitude, the first officer called for landing. The captain noted seeing threshold lights before hearing a Ground Proximity Warning System (GPWS) glide slope warning. He issued a "pull up" command to the first officer.
Upon touchdown at 133.5 knots, the captain observed some approach light bars below the nose but reported no unusual sensations or sounds during the landing roll. After parking, the crew discovered damage to the left main brake line and a loss of hydraulic fluid from the right system. The aircraft also sustained damage to the left main tires, the bottom left aft portion of the fuselage, and the left engine and cowling.
An examination of the runway revealed one approach light broken at its base 19 feet from the start of the paved overrun. Tire marks were observed starting approximately 49 feet from the start of the paved overrun, with the left pair running through three sets of center approach lights and two runway threshold lights for 354 feet before continuing down the runway for approximately 700 feet. Broken light stanchions and debris were found along these marks.
The investigation
An examination of the aircraft's avionics equipment and the airport's ILS approach revealed no anomalies. Data from the flight data recorder (FDR) showed the aircraft captured the ILS glide slope 38 seconds before touchdown at a radio altitude of 734 feet. Four seconds later, the FDR indicated the aircraft was tracking the glide slope at 617 feet. However, five seconds prior to touchdown, the glide slope showed a 2-dot fly-up deviation at a radio altitude of 114 feet, and the glide slope warning was active. At touchdown, the glide slope deviation had increased to 4.3 dots fly up. The FDR recorded vertical acceleration of 1.7 g's followed by 0.7 g's, and lateral acceleration of -0.15 g's. The right outboard spoiler began deploying 2.5 seconds after touchdown. Low hydraulic pressure lights remained off throughout the sequence.
Findings
- The first officer's last simulator checkride occurred 14 months prior to the incident.
- The first officer could not recall the last time he had flown an instrument approach in the aircraft in actual weather conditions.