American Trans Air Lockheed L1011-385-1 L1011-385- accident

The scheduled airline Lockheed L-1011, sustained a tail strike during landing damaging the pressure bulkhead and several bell frames and stringers in the aft fuselage. According to the flight crew, the captain was landing on runway 2 using a flaps 42 (full down) setting. The ATIS was reporting winds from 060 degrees at 18 knots with gusts to 26 knots. Both pilots stated that as the airplane descended through 30 to 40 feet agl, a sudden high sink rate developed. The captain added power and pitched the nose up to arrest the rate of descent. All three crewmembers said that the landing was harder than normal, but none would classify as a "hard landing." According to the airport METAR, the winds at 0954 were from 060 degrees at 22 knots with higher gusts to 27 knots. Review of the high resolution ASOS wind data from a sensor near the touchdown zone for the runway disclosed no significant speed variations in either the head or crosswind components during the last 10 seconds of the approach. An FAA inspector entered the cockpit after the aircraft had been parked at the gate and observed the captain's airspeed indicator final approach speed bug setting at 142 knots. According to the airline's L-1011 Operations Manual, the inner bug is set to the final approach speed, which is Vref adjusted for 1/2 of the steady state wind plus all of the gust additive. The final bug setting cannot be less than Vref + 5, nor more than Vref + 20. For the aircraft's landing weight, the zero wind Vref was calculated at 138 knots, with a wind adjusted final approach speed of 150 knots. Read out of the Flight Data Recorder disclosed that in the 48 seconds prior to touchdown, the calibrated airspeed varied from 154 to 145 knots. In the 10 seconds prior to touchdown, the airspeed varied from 143 to 130 knots at wheel contact. In the 10-second period before touchdown, the airspeed decreased from 143 to 135 knots, then increased to 143 knots 3 seconds later, and then steadily decayed to the 130-knot value recorded at ground contact. At touchdown, the aircraft was 8 knots below the no-wind reference speed, and, 13 knots below the airline's minimum specified speed. The maximum pitch attitude value of 8.79 degrees aircraft nose up was 4 degrees less than the maximum allowable pitch attitude to prevent a tail strike. Teardown of the left and right main landing gear assemblies revealed no discrepancies, and no write-ups were found in the maintenance records for the previous 180 days.

Verbatim NTSB analysis and probable cause from the NTSB dataset