Flight Details
The departure, en route, and initial approach phases of the flight were reported by the crew to be without incident. The aircraft was configured for landing with gear down and flaps set to 28 degrees. The landing weight was 127,000 pounds.
Approach and Landing
Air traffic control reported winds from 100 degrees at 6 knots. The aircraft exited a thin cloud layer with a base approximately 1,000 feet above ground level. At 100 feet above the runway, the captain detected a "sinker" and applied thrust to arrest the descent. The aircraft continued to sink during the flare and made a "very firm landing with no bounce."
Data Analysis
Digital Flight Data Recorder (DFDR) data showed that a few seconds before touchdown, airspeed decreased 6 knots below Vref, and pitch attitude changed from 2.1 degrees to 5.3 degrees. A vertical acceleration of 2.032 Gs was recorded at an airspeed of 129.2 knots. Vref was calculated at 135 knots. The pilot reported applying thrust upon detecting the sink rate, but DFDR data indicated that engine pressure ratios (EPRs) did not increase until 7 seconds after touchdown.
Company Procedures
The company's standard operating procedures define a stabilized approach as requiring the aircraft to be at approach speed (Vref plus additives), on the proper flight path with the proper sink rate, and at stabilized thrust. These conditions must be maintained throughout the remainder of the approach; otherwise, a go-around is required.
Cockpit Voice Recorder
The Cockpit Voice Recorder (CVR) contained four channels of audio, but none of the recorded audio was pertinent to the incident. The audio was consistent with the CVR being overwritten or recorded over by subsequent events.