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发帖数: 2000 | 1 Pilots of the Asiana Airlines jet that crashed at San Francisco
International Airport over the weekend allowed the Boeing 777's speed to dip
dangerously low, and then apparently ran out of time to correct their
landing approach, according to preliminary data released by investigators.
While stopping short of pinpointing pilot error as the likely cause of the
fiery crash that killed two teenage passengers and injured dozens of others,
National Transportation Safety Board Chairman Deborah Hersman indicated
Sunday that investigators already are focused primarily on understanding why
the crew allowed speed to decay to such an extent—and failed to take
decisive action until the wide-body jet was less than two seconds from
impact.
In the first on-scene briefing by the NTSB, Ms. Hersman said a preliminary
readout of the plane's flight-data and cockpit-voice recorders indicates
that everything was normal—with no discussion of any onboard problems or
concerns about the visual approach in good weather—until just seven seconds
before impact.
At that point, she told reporters, the crew realized the plane arriving on
an overnight flight from Seoul was flying too slowly. "The speed was
significantly below" the designated approach speed of roughly 130 miles an
hour.
Three seconds later, a stall-warning activated, indicating the Boeing 777
carrying 307 passengers was losing aerodynamic lift. The crew didn't act to
sharply increase engine thrust and try to climb away from the strip—
conducting what is called a "go-around"—until 1.5 seconds before impact.
The safety board believes "the engines appear to respond normally" to those
commands, Ms. Hersman said, but by then it was too late to recover, and
portions of the lumbering jet slammed into the seawall in front of the strip.
Taken together, the preliminary data and Ms. Hersman's early description of
the sequence of events strongly suggest investigators are leaning away from
mechanical or other system failures as the likely culprit.
During the media briefing, Ms. Hersman stressed that there was "no prior
distress call" from the cockpit crew, which should have been able to rely on
both ground-based and onboard landing aids to "establish an approach path"
to safely reach the beginning of the runway. The jet slammed down roughly 1,
000 feet short of that point, leaving some parts on the seawall separating
the runway from San Francisco Bay. Other parts were recovered from the
nearby water.
Because the jet was on a visual approach in excellent weather, "you don't
need instruments to get into the airport" safely, Ms. Hersman said. |
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