NTSB Identification: DEN05IA027.
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Scheduled 14 CFR operation of American Airlines, Incorporated (D.B.A. American Airlines)
Incident occurred Sunday, November 21, 2004 in Denver, CO
Probable Cause Approval Date: 07/07/2005
Aircraft: McDonnell Douglas DC-9-82, registration: N234AA
Injuries: 106 Uninjured.

NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.

The first officer was hand-flying the airplane. During the descent for the approach, the crew received a special observation that the weather was ceilings 300 and 1,000 feet broken and 1/2 mile visibility and fog. The crew briefed the ILS approach for runway 35L. When approach control (TRACON) cleared the airplane for the ILS approach, the airplane was at 9,000 feet. The captain reported that as they continued, the glide slope indicator "came up and actually went below us," and that the airplane had not yet intercepted the localizer. The captain asked TRACON for a lower altitude. TRACON "apologized" and cleared the airplane to 7,000 feet, and then asked the crew if they would still be okay for the approach. The crew said they would be okay. The captain said the airplane was configured and was approaching the glide slope from above, as it was intercepting the localizer. He said the first officer was on the localizer and glide slope. At 100 feet, the captain called approach lights in sight, and the first officer acknowledged. When the captain called reaching the decision altitude, the first officer called landing. The captain said he started to see the threshold lights and then heard the "glide slope" GPWS (Ground Proximity Warning System) warning. The captain called "pull up" to the first officer. The captain said as they touched down he thought he could see some approach light bars below the nose, but did not feel or hear anything unusual. The landing roll out was normal. After parking, the crew discovered damage to the left main brake line and loss of hydraulic fluid from the right system. The airplane showed additional damage to the left main tires, bottom left aft portion of the fuselage, and to the left engine and left engine cowling. An examination of the runway showed one approach light, 19 feet from the beginning of the paved overrun, broken forward at its base. Approximately 49 feet from the start of the paved overrun surface, the beginning of two pairs of parallel-running tire marks were observed. The left pair of tire marks ran through three sets of center approach lights in the overrun, two runway threshold lights, a distance of 354 feet, and continued down runway 35L for approximately 700 feet. Light stanchions, broken lens pieces, and bulb debris was observed extending down the runway along the tire marks. An examination of the airplane's avionics equipment and the airport's ILS approach showed no anomalies. The flight data recorder (FDR) showed that the airplane captured the ILS glide slope 38 seconds prior to touchdown at a radio altitude of 734 feet. The FDR pitch, recorded 4 seconds later, indicated the airplane was tracking the glide slope and at a radio altitude of 617 feet. At 5 seconds prior to touchdown, the glide slope showed a 2 dots fly up deviation. The airplane was at a radio altitude of 114 feet. The glide slope warning was on. The glide slope continued to increase reaching 4.3 dots fly up at touchdown. The airplane's airspeed at touchdown was 133.5 knots. Vertical acceleration was 1.7 g's followed by 0.7 g's approximately 1/2 second later. Lateral acceleration was -0.15 g's. The right outboard spoiler began to deploy at touchdown plus 2.5 seconds. The hydraulic pressure low lights (left and right) remained in an "off" state throughout the incident sequence. Flight crews are administered a simulator check every 9 months, either by the company or the FAA. Crews do not fly practice approaches in the airplane. The first officer's last simulator checkride was 14 months prior to the incident. The first officer stated he could not recall when the last time was that he flew an instrument approach in the airplane in actual weather conditions.


The National Transportation Safety Board determines the probable cause(s) of this incident to be:

the first officer's failure to maintain proper glide slope during the landing approach, and the captain's failure to adequately monitor the approach and landing, and his failure to challenge and/or intervene when the first officer continued to descend below the glide slope. Factors contributing to the incident were the first officer's lack of recent experience in flying a complete ILS approach in actual instrument conditions, the low ceilings and fog.

Full narrative available

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