American Airlines Flight 2253 Runway
January 13, 2011 - In its continuing investigation of
the runway overrun of a jetliner in
about 11:38 am MT on Wednesday, December 29, American
Airlines flight 2253, a B-757-200 (N668AA) inbound from
Chicago O'Hare International Airport, ran off the end of
runway 19 in snowy conditions while landing at
Instrument Flight Rules (IFR) weather conditions prevailed around the time of the incident with a ceiling of 400 feet, light snow and visibility of 1 mile. Winds were 10 knots from 240 degrees. Runway friction measurement data obtained before and after the event have been provided by the Jackson Hole Airport Authority for further evaluation by the NTSB.
continuing investigation, work groups have been formed to
examine the subject areas of air traffic control, airports,
meteorology, flight crew operations, airworthiness, maintenance
records, cockpit voice recorder (CVR), flight data recorder
(FDR), and airplane performance.
discrepancies were found in the air/ground, autobrake, and
thrust reverser systems. Examination of the auto speed brake
mechanism in the cockpit pedestal found that the linear actuator
aft attachment was improperly installed and was missing a
maintenance group convened at the American Airlines facility in
The airplane was
manufactured in June 1992 and, at the time of the incident, had
accumulated 58,879 hours and 20,518 cycles. No discrepancies were noted
during the last periodic service maintenance check conducted on December
26, 2010. The last heavy maintenance was accomplished in October 2005.
The auto speed brake actuator was replaced in January 2008.
The FDR group has
begun the process of determining which of the documented parameters are
installed and should be functional, and is checking the recorded data
for validity. The group has verified the following factual information.
The FDR download contains the last 43.9 hours of data, more than the
required 25 hours, and includes all of the incident flight. The recorded
speed brake handle position indicates that the speed brakes were
manually extended by the flight crew during the approach after which the
handle was left in the armed position until landing. The FDR records
only the speed brake handle position and not the individual speed brake
(spoiler) panel positions.
The FDR data indicate that the aircraft touched down at approximately 132 knots. At touchdown, the air/ground parameter changes to "ground" for approximately one second and then switches to "air" for approximately ? second before changing back to "ground" for the remainder of the recording. During the time period when the air/ground parameter switched back to "air," the speed brake handle position momentarily moved toward the down position and then returned to the armed position where it stayed for the remainder of the recording.
Thrust Reverser (T/R) discrete parameters indicate that the T/Rs moved into the in-transit position during the ? second that the air/ground logic parameter indicated "air." The T/Rs remained in the in-transit position for approximately 10 seconds before transitioning to the stowed position for one second. The T/Rs then moved back to the in-transit position for an additional 6 seconds before becoming deployed.
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