|Title:||Tailstrike on landing, McDonnell Douglas MD-11, HL-737, May 25, 1996|
|Micro summary:||This MD-11 encountered a tail strike while landing.|
|Event Time:||1996-05-25 at 1513 PDT|
|Publishing Agency:||National Transportation Safety Board (NTSB)|
|Site of event:||LAX|
|Departure:||Ted Stevens Anchorage International Airport, Anchorage, Alaska, USA|
|Destination:||Los Angeles International Airport, Los Angeles, California, USA|
|Airplane Type(s):||McDonnell Douglas MD-11|
|Type of flight:||Cargo|
|Executive Summary:||HISTORY OF FLIGHT |
On May 25, 1996, about 1513 hours Pacific daylight time, Korean Airlines Flight 090, a McDonnell Douglas MD-11 freighter, Korean registry HL7373, sustained major structural damage during a tail strike while landing at Los Angeles International Airport, Los Angeles, California. The crew of two were uninjured. The aircraft was being operated by Korean Airlines as a scheduled cargo operation under 14 CFR Part 129 when the accident occurred. The flight originated at Anchorage, Alaska, at 0945 hours Alaska daylight time.
During the approach into Los Angeles the air traffic controller advised the pilot to plan for a runway 25R approach. After passing the Santa Monica VOR eastbound (downwind), the controller advised a change to runway 25L. The pilot was given radar vectors for runway 25L, the final approach course. The Santa Monica VOR is located about 5 nautical miles north of runway 25L.
The crew of a commuter aircraft was holding for departure and witnessed the landing and tail strike.
The Digital Flight Data Recorder (DFDR) data indicated the autopilot was disconnected with the aircraft on a magnetic heading of 250 degrees and a wing flap configuration of 35 degrees. Ten seconds before the first touchdown, at FDR Subframe Reference Number (SRN) 1771, the aircraft was in a wings level attitude, the spoilers were not armed, and engine N1 settings were approximately 32 percent. (The FDR SRN is a measure of relative time on the DFDR; one subframe is equivalent to 1 second). At SRN 1778, the elevators trailing edge surface start deflecting up to about 12 degrees. The pitch attitude also begins to increase at that time. At SRN 1781, a 2.13 (g) spike in the vertical acceleration occurs. The aircraft reaches a maximum pitch attitude of 12 degrees and at SRN 1787, the nose gear compresses.
According to the operator's report, the captain accumulated 10,785 total flight hours with 3,072 in the make and model of the accident aircraft.
The first officer was flying the approach. According to the report, he accumulated 5,398 total flight hours with 2,800 hours listed in the make and model of the accident aircraft.
The McDonnell Douglas MD-11F was manufactured February 16, 1992. According to the operator, the aircraft had accumulated 15,896 flight hours.
Preliminary review of the flight release and load manifest revealed that the landing weight was about 419,700 pounds with a CG about 24.0 percent of the MAC.
Both the flight data recorder and the cockpit voice recorder were removed and sent to the Safety Boards Engineering and Computer Services Division for data retrieval. Copies of the these reports are attached to this report.
At 1452, the Los Angeles Airport Terminal Information Service (ATIS) was reporting: 4,300 feet scattered; 15 miles visibility; temperature 66 degrees Fahrenheit; dew point 54 degrees Fahrenheit; wind 250 degrees at 15 knots; and the altimeter was 29.92 inHg. There were no windshear conditions reported, nor forecasted.
On final approach to runway 25L, the air traffic controller advised the pilots that the winds were 220 degrees at 11 knots.
An examination revealed that substantial damage occurred between airframe stations 1801 and 2033. There was damage to the auxiliary power access door aft of station 2033. The major damage extended from the exterior skin inward to the stringers, bellframes, and the lower portion of the aft pressure bulkhead.
According to McDonnell Douglas representatives, this accident was the 13th tail strike incident/accident involving the MD-11 aircraft resulting in minor or substantial damage. There were five tail strikes during takeoffs and eight during landings. All takeoff tail strikes resulted in minor damage.
The factors affecting tail strikes during landing were: flap setting; center of gravity; gross weight; air speed; improper strut servicing (single chamber vs. Dual chamber); sink rate; pitch rate; attitude and ground spoilers.
According to the DFDR approach information, the descent rate was between 1,470 feet per minute (fpm) and 300 fpm. The horizontal stabilizer moved over 3 degrees aircraft nose up between 700 feet above ground level (agl) to 200 feet agl with a corresponding increase in pitch. At 200 feet agl, an additional 3 degrees aircraft nose up were commanded which raised the pitch attitude to 8 degrees aircraft nose up. According to the data, the auto throttles were held back and the speed dropped below landing approach speed (Vref). At 50 feet agl the speed was 10 knots below Vref and raised the pitch to 12 degrees aircraft nose up. The touchdown occurred at 12 degrees pitch, 16 knots low at a sink rate of 9 feet per second. The tail touched the runway coincident with the main gear. According to the DFDR, the spoilers were not armed and the aircraft responded to all pilot inputs.
According to the cockpit voice recorder information, no formal checklist was used during the approach.
The FDR was previously released, and the CVR was released to a Korean Airlines representative on 10/25/96.
|Learning Keywords:||Operations - Checklists/Procedures|
|Operations - Crew Resource Management|
|Operations - Tailstrike|
|Operations - Unstabilized Approach|
|Consequence - Damage - Airframe or fuselage|
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