What happened
The flight crew reported that the departure, en route, and initial approach phases were completed without incident. During the approach, the crew configured the aircraft with gear down and flaps at 20 degrees for landing, with a total landing weight of 127,000 pounds. Weather conditions at the tower indicated winds from 100 degrees at 6 knots. As the aircraft descended through a thin cloud layer with a base of approximately 1,000 feet above ground level, the captain detected a sink rate while at 100 feet above the runway and applied thrust to correct it.
The aircraft continued to descend during the flare, resulting in a very firm landing with no bounce. While the pilot reported applying thrust upon detecting the sink rate, data indicated that engine EPR did not increase until seven seconds after touchdown.
The investigation
A review of the Digital Flight Data Recorder (DFDR) revealed that a few seconds before touchdown, the airspeed decreased 6 knots below Vref, and the pitch attitude shifted from 2.1 degrees to 5.3 degrees. The aircraft recorded a vertical acceleration of 2.032 Gs at an airspeed of 129.2 knots, compared to a calculated Vref of 135 knots. The Cockpit Voice Recorder (CVR) contained four channels of audio, but none were found pertinent to the investigation, as the audio appeared to have been overwritten by subsequent events.
Findings
- The approach did not meet company stabilized approach criteria, which require the aircraft to be at approach speed, on the proper flight path, and at a stabilized thrust.
- Company procedures mandate a go-around if stabilized approach requirements cannot be maintained through the minimum stabilized approach heights.